Fall 2023 Issue by Association of Water Technologies

the ANALYST The Voice of the Water Treatment Industry

Volume 30 Number 4

1300 Piccard Drive, Suite LL 14 • Rockville, MD 20850

Fall 2023

Accounting for Consumptions of Water Treatment Chemicals Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations Can Recent Advances in Fluorescence Improve Control of Cooling Water Chemistry? No Phosphonate? The Effective Use and Limits of Polymers

Volume 30 Number 4 Fall 2023

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Cover A cold lime clarifier at a coal mine for treating run-off water. Photo courtesy of Dave Christophersen, Dave Christophersen, LLC.

Fall 2023

Volume 30

10 Accounting for Consumptions of Water Treatment Chemicals David Christophersen, Dave Christophersen Consulting LLC

Chemicals that are used in water treatment processes have various purposes and consumption factors. There are many considerations that explain chemical consumption or loss of residual. Some consumptions are intentional and beneficial; some are circumstantial, consequential, or nonbeneficial.

22 Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations

Matheus Paschoalino, PhD; LoongYi Tan; Donald A. Johnson, PhD; and Jun Su An, Solugen Inc. With the ban on chromate use in CTW, phosphate-based technologies were introduced and became the new standard for cooling water treatment for the past several decades. Even stricter environmental regulations have followed that are associated with phosphorous-containing products. These regulatory changes have stimulated the development of novel corrosion inhibitors that are phosphorous free, including the use of compounds from natural sources, aiming for less-toxic products with a negligible negative impact on the environment.

30 Can Recent Advances in Fluorescence Improve Control of Cooling Water Chemistry? Raymond M. Post, P.E., United Water Consultants

Number 4

Calendar of Events

President’s Message

Message From the President-Elect

54 Discovering AWT 59 Making a Splash 61 CWT Spotlight 62 Tales From the Waterside 66 T.U.T.O.R. 73 In Memoriam 74 What’s (Water) on Your Mind? 78 Advertising Index

42 No Phosphonate? The Effective Use and Limits of Polymers Michael L. Standish, Radical Polymers, a division of MFG Chemical

Water treatment professionals use chemicals and equipment to control mineral scale, metals corrosion, and microbial growth in process applications such as cooling towers. Recent disruptions in raw material supplies have significantly altered how water treatment companies formulate products and, ultimately, service their customers. One primary disruption has been the availability and cost of phosphonate chemistries that are heavily relied upon for the control of mineral scale and mild steel corrosion. The aim of this article is to equip the reader with an understanding of the consequences (Pros and Cons) of using polymers as phosphonate substitutes for mineral scale control.

the ANALYST Volume 30 Number 4

1300 Piccard Drive, Suite LL 14 Rockville, MD 20850 (301) 740-1421 • (301) 990-9771 (fax) www.awt.org

2024 AWT Board of Directors

Calendar of Events Association Events

President

Noah Baskin

President-Elect

John D. Caloritis, CWT

Secretary

Kyle Rossi, CWT

Treasurer

Craig Bodenmiller, CWT

Immediate Past President

Steve Hallier, CWT

Directors

Tammy Faber, MBA Michelle Lunn Derrick Vandenberg, CWT Greg Gehrke

Ex-Officio Supplier Representative

Pam Simmons

Past Presidents

Fred Shurtz Matt Jensen, CWT Jack Altschuler Mark R. Juhl John Baum, CWT Brian Jutzi, CWT R. Trace Blackmore, CWT, Bruce T. Ketrick Jr., CWT LEED AP Bruce T. Ketrick Sr., CWT Michael Bourgeois, CWT Ron Knestaut D.C. “Chuck” Brandvold, CWT Robert D. Lee, CWT Thomas Brandvold, CWT Mark T. Lewis, CWT Brent W. Chettle, CWT Steven MacCarthy, CWT Dennis Clayton Anthony J. McNamara, CWT Bernadette Combs, CWT, James Mulloy LEED AP Alfred Nickels Matt Copthorne, CWT Scott W. Olson, CWT James R. Datesh William E. Pearson II, CWT John E. Davies, CWT William C. Smith Jay Farmerie, CWT Marc Vermeulen, CWT Gary Glenna David Wagenfuhr Charles D. Hamrick Jr., CWT Casey Walton, B.Ch.E, CWT Joseph M. Hannigan Jr., CWT Larry A. Webb

Staff

Executive Director

Denise Jackson

Deputy Executive Director

Sara L. Wood, MBA, CAE

Member Services Director

Angela Pike

Senior Vice President, Meetings

Tina Schneider, CMP

Account Executive

Matt Coffindaffer, CAE

Meeting Coordinator

Caroline Bentley

Meeting Planner

Tim Foley

Exhibits and Sponsorship Manager

Jessica Martin

Director of Marketing

Melissa Graham, MBA

Marketing Manager

Mary Claire Gordon

Editorial Services Manager

Heather Rigby

Production Manager

Jansen Vera

Director of Accounting Services

Dawn Rosenfeld

The Analyst Staff Publisher

Denise Jackson

Managing Editor

Heather Rigby, hrigby@msp-amc.com

Production Manager

Jansen Vera

Technical Editor

Michael Henley, mdhenleywater@gmail.com

Advertising Sales Manager Carol Nettles, carol@awt.org

The Analyst is published quarterly as the official publication of the Association of Water Technologies. Copyright 2023 by the Association of Water Technologies. Materials may not be reproduced without written permission. Contents of the articles are the sole opinions of the author and do not necessarily express the policies and opinions of the publisher, editor or AWT. Authors are responsible for ensuring that the articles are properly released for classification and proprietary information. All advertising will be subject to publisher’s approval, and advertisers will agree to indemnify and relieve publisher of loss or claims resulting from advertising contents. Editorial material in the Analyst may be reproduced in whole or part with prior written permission. Request permission by writing to: Managing Editor, the Analyst, 1300 Piccard Drive, Suite LL 14, Rockville, MD 20850, USA. Annual subscription rate is $100 per year in the U.S. (4 issues). Please add $25 for Canada and Mexico. International subscriptions are $200 in U.S. funds.

2024 Technical Training Seminars (West) March 6-9, 2024 Embassy Suites Dallas – Frisco Convention Hotel Frisco, Texas

2024 Technical Training Seminar (East)

April 17-20, 2024 Cleveland Marriott Downtown at Key Tower Cleveland, Ohio

2024 Annual Convention and Exposition September 10–13, 2024 Louisville Convention Center and Omni Louisville Louisville, Kentucky

2025 Technical Training Seminars (West) February 25–28, 2025 Doubletree Mission Valley San Diego, California

2025 Technical Training (East)

TBA

2025 Annual Convention and Exposition

November 12–15, 2025 The Broadmoor Hotel Colorado Spring, Colorado

2026 Annual Convention and Exposition September 16–19, 2026 Oklahoma Convention Center and Omni Hotel Oklahoma City, Oklahoma

2027 Annual Convention and Exposition September 8–11, 2027 Cleveland Convention Center Cleveland, Ohio

Also, please note that the following AWT committees meet on a monthly basis. All times shown are Eastern Time. To become active in one of these committees, please contact us at (301) 740-1421. Second Tuesday of each month, 11:00 am—Legislative/Regulatory Committee Second Tuesday of each month, 2:30 pm—Convention Committee Second Wednesday of each month, 11:00 am—Business Resources Committee Second Friday of each month, Noon—Pretreatment Subcommittee Second Friday of each month, 10:00 am—Special Projects Subcommittee Second Friday of each month, 11:00 am—Cooling Subcommittee Third Monday of each month, 10:00 am—Certification Committee Third Monday of each month, 3:30 pm—Young Professionals Task Force Third Monday of each month, 3:00 pm—Education Committee Third Friday of each month, Noon—Boiler Subcommittee Third Friday of each month, 10:00 am—Technical Committee Third Friday of each month, 11:00 am—Wastewater Subcommittee Fourth Friday of each month, 1:00 pm—Education Resources Committee

Other Industry Events

RETA, Annual Convention, November 13–16, 2023, Jacksonville, Florida Cooling Technology Institute, February 4-8, 2024, Houston, Texas WateReuse Association, March 11–14, 2024, Denver, Colorado ABMA Boiler Technology Conference & Expo, May 1–3, 2024, Aurora, Colorado Electric Utility Chemistry Workshop, June 7–9, 2024 Champaign, Illinois

the ANALYST Volume 30 Number 4

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President’s Message

By Noah Baskin

AWT is working with the American National Standards Institute (ANSI) to obtain accreditation for our CWT program. ANSI is the premier organization to ensure the highest standards for continuing education programs. ANSI accreditation is a highly regarded credential. We have established an ANSI accreditation task force, and we will have more information about this process as the year progresses.

I’ve just returned from Grand Rapids following our hugely successful Annual Convention. It was great to see so many friends and colleagues. We had record attendance and participation by AWT members, along with great support from suppliers and exhibitors. I was honored to be installed as AWT President. My thanks to my predecessor, Steve Hallier, CWT, for his leadership this past year, and thanks to all who joined us in Grand Rapids!

Finally, I want to challenge all of you to take advantage of all AWT has to offer. Join a committee, subcommittee, or task force and lend your expertise. AWT grows stronger only through the participation and engagement of our members. Our field benefits from our collective experience and wisdom, and I guarantee you will get more out of your participation than you put in.

During the convention we held our Annual Membership Meeting where we looked back at 2022 and reported on our success to-date in 2023. Membership is steady, despite consolidation, attendance at Technical Trainings and the convention are up and our new Individual Member category has exceeded expectations.

I am looking forward to a great year ahead. I welcome your suggestions and feedback and I can be reached at nbaskin@towerwater.com.

2024 Technical Training

In 2023, we held two AWT Technical Training Seminars. The sessions were held in Pittsburgh and San Diego, and as noted above, they were well-attended. Those who participated in our 2023 sessions told us they found the training worth their time and investment. The training courses are revised and updated each year to ensure we are delivering the very latest information. It is essential that we stay on top of emerging trends in our field and prepare to address new challenges as they emerge. In 2024, we are planning two more sessions: Dallas on March 6–9, 2024, and Cleveland on April 17–20, 2024. I hope you and your team will find time to participate. To learn more about our 2024 Technical Training, please visit www.awt.org.

the ANALYST Volume 30 Number 4

SYSTEM

BUILDER

Message From the President-Elect

By John Caloritis, CWT

The Omni Louisville

Believe it or not, we have already begun planning for the 2024 Annual Convention & Exposition, which will take place next September in Louisville, Kentucky.

At the Omni Louisville Hotel, experiences are tailored to the history and rhythm of the city. Take a dip in the heated rooftop pool, dine with family or bowl with friends while sipping signature cocktails at Pin + Proof, the hotel’s Prohibition-style speakeasy. Relax at the full-service Mokara Spa or enjoy built-in entertainment and uninterrupted connectivity in one of 612 charming guest accommodations. The Omni is steps from the Kentucky International Convention Center. You’ll also find Churchill Downs, Main Street, Whiskey Row Distilleries, and the Louisville Slugger Museum & Factory nearby.

The Location

We are very excited to be headed to Louisville next year. Louisville is a city that combines heritage with innovation, originality and quirkiness, with friendliness in a way that is completely unique! Louisville has iconic attractions, world class hotels, great golf, and fantastic culinary scene. And, of course, Louisville is the home of Kentucky bourbon and the official starting point of the Kentucky Bourbon Trail.

Educational Program

We are currently accepting abstracts for the 2024 convention. If you have a presentation that would be of interest to the membership, submit an abstract to be a part of the program. We are already researching keynote speakers for next year and welcome your suggestions.

The Convention & Exposition will be held at the Kentucky International Convention Center. This facility, fresh off a $207 million renovation, has great meeting rooms, well-designed exhibit space, and interesting venues to ensure a successful event.

Please mark your calendars for the week of September 10th, 2024, and join us in Louisville. More details to follow.

Our 2024 Awards Dinner will take place at historic Churchill Downs, the annual home of the Kentucky Derby. First opened in 1875, Churchill Downs has hosted the Derby, the Kentucky Oaks, and Breeder’s Cup races. It is a spectacular setting for our Awards Dinner.

I look forward to an exciting year ahead. If I can ever be of service, please contact me at jcaloritis@metrogroupinc.com. Thank you!

the ANALYST Volume 30 Number 4

Accounting for Consumptions of Water Treatment Chemicals David Christophersen, Dave Christophersen Consulting LLC

Accounting for Consumptions of Water Treatment Chemicals

Oxidation/reduction reactions Hydrolysis (reactions with water) Precipitation reactions Adsorption onto suspended solids, surfaces, deposits, biofilm, etc. Chelation or sequestration Biological degradation UV degradation Volatilization Testing inaccuracies Temperatures Retention times Other chemical reactions

Depending on the chemical, its purpose may be to treat the water and may include reacting with constituents in the water, or it may be used to treat system surfaces or components. Demand then can be influenced by water chemistry, conditions, materials of construction, and surface areas. When target control limits are set, applied dosages will need to compensate for consumption to achieve the desired residuals for many of the chemicals that are applied.

Minimal (<10%) Low (10 to 30%) Significant (30 to 80%) High ( >80%)

Polymeric Dispersants—Minimum to Low Depending upon the chemistry of a specific polymer, its functional groups, molecular weight, dosage, and mode of action, the polymer can have some staying power in a water treatment application. Generally, it is assumed that a polyacrylate, copolymer, or terpolymer residual will be close to the applied concentration in a boiler, cooling, or membrane system where there is a reasonably low retention time of the system such as a few hours for a boiler, a few days for a cooling tower system, or a few minutes for a reverse osmosis system. However, these polymers can be lost to adsorption onto suspended solids to some extent or consumed by high amounts of iron, or cationic materials such as an epichlorohydrin-dimethylamine (Epi-DMA) or diallyldimethylammonium chloride (DADMAC) coagulant. One proprietary laboratory test that was conducted at my request using an acrylic acid and 2-acrylanmido-2-methylpropanesulfonic acid (AA/ AMPS) copolymer dispersant and a terpolymer showed that when applied to a relatively clean cooling tower water containing 50 parts per million (ppm) of kaolin clay, the applied concentration remained about unchanged.

The following is a list of water treatment chemicals evaluated in this article:

Neutralizing amines Molybdate Zinc Nitrite Chlorine Bromine Biocides Coagulants Flocculants Cleaners Objective: From the list of frequently applied water treatment chemicals, categorize each on the typical relative amount of consumption expected and provide a table with a general summary of typical consumptions as:

Polymeric dispersants Phosphates use in boiler and cooling waters EDTA Sulfites Organic oxygen scavengers Phosphonates Azoles Surfactants Silicates Film-forming amines

The blue line in Figure 1 shows that with 1,000 ppm of clay at a dosage of 10 ppm polymer, about 2 ppm of the 11

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Accounting for Consumptions of Water Treatment Chemicals continued

of either cationic coagulants/flocculants or biocides exhibit strong antagonistic effects on the performance of calcium phosphate-inhibiting polymers (2). Significant turbidity represented the precipitation of the cationic coagulants, flocculants, and biocides with the anionic polymer dispersants. An example of one of the studies presented in this article, Figure 3 presents turbidity created between various anionic dispersant polymers and DADMAC coagulant and significant loss of soluble and functioning dispersant from the water.

copolymer was lost and the red line shows that almost 1.5 ppm of the terpolymer adsorbed onto the clay, which is a consumption rate of 15 to 20% for a very unusually high total suspended solids (TSS). Figure 1: Kaolin clay consumption in a cooling tower.

Figure 3: Turbidity created between various anionic dispersant polymers and DADMAC coagulant.

In a different study shown next, performed by Radical Polymer using an AA-AMPS-tagged copolymer, they showed that when the ability of the polymer to stabilize the calcium phosphate is exceeded, the majority of the polymer is lost from solution as it adsorbs onto the precipitating calcium phosphate (1). So, the polymer concentration remains good until its ability is exceeded, then up to almost all of it is consumed, depending on how much precipitation occurs. Under this failure mode, 90% or more of the polymer can be consumed (Figure 2).

Phosphates in Boiler Water

In boiler water treatment, sources of orthophosphate (PO4) are often applied such as from trisodium phosphate, or a polyphosphate such as sodium hexametaphosphate and choices are made for a variety of reasons. The polyphosphates will completely hydrolyze to ortho phosphate in the boiler water.

Figure 2: Consumption rates of an AA-AMPS-tagged copolymer.

Low-pressure boilers (low to high, dependent on concentration of Ca and Fe). In low-pressure boilers, phosphate is often used as part of a phosphate precipitating program where orthophosphate is used to preferentially precipitate calcium out of solution in the bulk water where it can be conditioned as sludge. Phosphate may also precipitate with other cations such as iron if present and consumption is dependent upon concentrations. Consumption can be minimal if there is zero hardness and iron in the boiler feedwater, or it could be very high if there is calcium present to consume it. Phosphate dosage is based upon the amount required to remove calcium plus the residual soluble phosphate desired to maintain in the cycled boiler water. Demand could be zero and the applied cycled residual would be that which was fed, or when calcium level is high, greater

Cationic materials can have high consumption effect on anionic dispersants as they charge-neutralize each other and create suspended solids. A study performed by Lubrizol and presented at an AWT conference in 2002 showed that even low levels of 0.1 ppm to 2 ppm 12

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Accounting for Consumptions of Water Treatment Chemicals continued

than 90% could be consumed and the applied dosage would be very much greater than the desired residual concentration dosage.

and particularly during initial passivation. Some orthophosphate and polyphosphate may also precipitate at the cathode with calcium, serving as a cathodic inhibitor.

The product dosage calculation (Equation 1) shows the consumption portion plus the residual portion and how it is influenced by calcium in the feedwater as well as feedwater cycles.

After film formation has occurred, further phosphate consumption is relatively low as it replenishes breaks in the film. Commonly, probably less than 10% of applied phosphate is lost from the bulk water as it fixes breaks in the inhibitor film, but the percent consumption is also affected by the amount of carbon steel surface area relative to the system volume and the actual demand in mass quantity of the phosphate molecules.

[100/(% PO4 activity of the product) ] x [ (Ca as CaCO3 x 0.67) + (PO₄ residual desired / FW cycles) ] = ppm of product required in the boiler feedwater Eq. 1

Examples

Phosphate solubility is very low and is much lower as pH increases, and calcium levels increase. Solubility is stabilized by sulfonated polymers, so the wrong or insufficient polymer can cause significant loss of soluble phosphate.

Using a 30% sodium hexametaphosphate product (PO₄ of 27.3%) at 20 cycles or 5% blowdown rate, and desired PO₄ residual of 30 ppm, a feedwater dosage for 0 ppm calcium or 1 ppm calcium are as follows: For 0 ppm calcium:

EDTA

100/27.3 x (0x0.67) + 30/20 = 0 ppm demand + 1.5 ppm residual dosage = 1.5 ppm total For 1 ppm calcium: 100/27.3 x (1x0.67) + 30/20 = 2.45 ppm demand + 1.5 ppm residual dosage = 3.95 ppm total

Demand for 1 ppm calcium in this example is 62% of the dosage. High-pressure boilers (minimal). In high-pressure boilers such as > 900 pounds per square inch gauge (psig), all of the applied phosphate should generally remain soluble and in solution at the applied dosage when high-purity water is used. This is because this grade of water has no consumptive reactive demand on the phosphate, assuming that the residual is maintained below phosphate solubility limits for the heat flux of the boiler tubes (i.e., phosphate hideout does not occur.

In boilers (low to high pressure—dependent on concentration of Ca, Mg, and Fe, and if there is existing scale in the boiler). Ethylenediaminetetraacetic acid (EDTA) dosage and demand calculation is very similar to that of phosphate for low-pressure boiler phosphate precipitating programs. There is a demand dosage based upon the amount of hardness and iron in the feedwater, plus the residual dosage of excess free available EDTA in the cycled boiler water. There is also a possible additional demand for excess EDTA if there are existing deposits within the boiler that could be chelated or resolubilized. If the boiler feedwater has zero hardness or iron and the boiler is free of scale deposits, then the demand and consumption are low.

In cooling systems, both orthophosphate and polyphosphates are commonly applied. There are consumptive mechanisms that will cause the soluble residual to be lower than the applied amounts.

If the boiler feedwater has some hardness or iron such as 1 ppm, then demand can be quite high. Typically, EDTA programs are reserved for very low hardness feedwaters of 1 ppm or less, and with consistent concentration since variations in demand can make dosage control very difficult.

Soluble orthophosphate is a powerful anodic corrosion inhibitor that reacts with iron being released from carbon steel at the anode to form an iron phosphate protective film. This film formation consumes some phosphate

The product dosage calculation (Equation 2) shows the consumption portion plus the residual portion and how they are influenced by hardness in the feedwater as well as feedwater cycles.

Phosphates in Cooling Water

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Accounting for Consumptions of Water Treatment Chemicals continued

(100/% EDTA in product) x [(Feedwater [FW] hardness x 3.8) + (EDTA residual/FW cycles)] = ppm product in FW Eq. 2

rate, and desired sulfite residual of 40 ppm, a feedwater dosage for 0.01 ppm dissolved oxygen or 2.0 ppm dissolved oxygen the calculations are as follows:

Examples

For 0.01 ppm DO (Good deaerator):

Using a 38% EDTA product at 20 cycles or 5% blowdown rate, and desired EDTA residual of 10 ppm, a feedwater dosage for 0.2 ppm hardness or 1 ppm hardness for a clean boiler are as follows:

100/62 x [ (0.01x5) + 40/20 ] = 0.08 ppm demand + 3.23 ppm residual dosage ] = 3.31 ppm total

For 0.2 ppm hardness:

Demand for 0.01 ppm DO in this example is 2.4% of the dosage. For 2.0 ppm DO (No DA, poor mechanical deaeration):

100/38 x [ (0.2x3.8) + 10/20 ] = 2 ppm demand + 1.32 ppm residual dosage ] = 3.32 ppm total

Demand for 0.2 ppm hardness in this example is 60.2% of the dosage.

100/62 x [ (2.0x5) + 40/20 ] = 16.13 ppm demand + 3.23 ppm residual dosage ] = 19.36 ppm total

For 1 ppm hardness:

Demand for 2 ppm DO in this example is 83.3% of the dosage.

100/38 x [ (1x3.8) + 10/20 ] = 10 ppm demand + 1.32 ppm residual dosage ] = 11.32 ppm total

Organic Oxygen Scavengers

Demand for 1 ppm hardness in this example is 88.3% of the dosage.

There are other oxygen scavengers or reducing agents that are used instead of sulfite or along with sulfite. They do not have the ability to scavenge oxygen as quickly as sulfite or catalyzed sulfite, so applied dosage calculations may not include complete oxygen removal (3).

Sulfites in Boiler Water

Sulfites are very commonly fed to boiler feedwater systems after mechanical deaeration to remove residuals of dissolved oxygen (DO). Good practices rely on a properly operating deaerator to remove most of the oxygen with the last very small traces to be removed chemically. Where improper deaeration occurs such as when the residual is above 7 to 10 parts per billion (ppb), there is high risk of corrosion since chemical removal and corrosion become competing reactions with both occurring simultaneously.

Depending upon the product selected, the purpose of its application may include passivation of metal surfaces besides removal of oxygen. Because reaction rates are slow for removal of oxygen, the consequence is that demand may often be less than what would be calculated based upon required stoichiometry for oxygen removal. With slow reaction rates the storage section of deaerators or feedwater tanks do not provide sufficient times for complete removal.

Sulfite usage then is dependent on the amount of oxygen to be chemically scavenged, which is the demand, plus the residual desired in the cycled boiler water. In properly operating deaerators, demand should be low.

The consequence is that when organic oxygen scavengers are applied, their consumption rate is generally anticipated to be low and the consumption comes from some oxygen removal, perhaps some metal passivation reaction, and if volatile such as DEHA, a loss to venting or with the steam. Figure 4 (4) shows oxygen scavenger reaction rates.

The product dosage calculation in Equation 3 shows the consumption portion plus the residual portion and how they are influenced by dissolved oxygen in the feedwater as well as feedwater cycles. (100/% SO3 in product) x [ FW O₂ x 5 + SO₃ residual in boiler/cycles)] = ppm product in FW Eq. 3

Phosphonates

A common use of phosphonates in cooling and in some boiler water treatment is as a threshold scale inhibitor. Some may also function as cathodic corrosion inhibitors. The mechanism of threshold scale control is

Examples

Using a 62% SO3 product at 20 cycles or 5% blowdown 14

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Accounting for Consumptions of Water Treatment Chemicals continued

a little sketchy, but when dosed at sub-stoichiometric concentrations compared to the scale-forming ions, the phosphonate at single-digit ppm concentration or less can temporarily interfere with formation of crystals. When induction time of scale formation is not exceeded, then there is little loss of phosphonate concentration in the treated water.

or benzotriazole with functionality as yellow metal corrosion inhibitors in open evaporative cooling systems or in closed loops. The azole ring reacts with copper and copper-containing metals to form a nitrogencopper (N-Cu) bond that is stabilized by the adjacent nitrogen atom. The rest of the molecule forms an organic hydrophobic barrier film to protect the metals surface from corrosion. Azoles also react with copper ions in solution creating a filterable copper-azole precipitant.

Some causes of loss include the following:

Exceeding its calcium tolerance whereby calcium phosphonate precipitation occurs. Degradation by an oxidant such as chlorine or bromine. High temperature degradation in some boiler applications. Cathodic corrosion control of certain phosphonates (calcium phosphonate film).

Initial demand is very high if the yellow metals have not been previously treated or have been stripped due to high chlorine, low pH or other causes. Consumption will be a factor of the amount of surface area of yellow metals in the system and the concentration of copper ion in solution. Where halogenation of the water occurs, tolyltriazole (TT) can be chlorinated and may then not show up in azole testing. Also, it has been reported that TT is a 60:40 racemic mixture and the higher percentage isomer is subject to microbiological degradation. Apparently, benzethonium chloride (BZT) does not face this same issue (4).

Working as threshold scale inhibitors and within normal holding times, phosphonate consumption should be minimal, but could be higher such as up to 30%.

Azoles

The most commonly applied azoles are tolyltriazole

Figure 4: Reaction rates of oxygen scavengers at pH 8.5 (left) and at pH 11 (right). Figure source: Arkema, Reference 4.

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Accounting for Consumptions of Water Treatment Chemicals continued

Surfactants

Surfactants and biodetergents are often used in cooling systems to help address biofilm control. They are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads). Therefore, a surfactant contains both a water insoluble (or oil soluble) component and a water-soluble component. Surfactants will diffuse in water and adsorb at interfaces between air and water or at the interface between oil and water, in the case where water is mixed with oil. Demand of surfactants and therefore dosage can be influenced by the amount of oil in the water or on system surfaces and some may also adsorb onto suspended solids in the system, but typically the applied dosage is high enough that most of the product remains in the bulk water until it is lost to blowdown or system draining.

Silicates

Soluble sodium and potassium silicates are useful as anodic corrosion inhibitors in open and closed cooling systems and for drinking water piping. They are also used in alkaline cleaning formulations. Monomeric and polymeric silica, introduced into a water system, is carried by flowing water to all parts of the distribution system. At the dilution levels used for water treatment, the majority of the silica depolymerizes to a reactive monomer form. The monomeric silica is adsorbed onto metal pipe surfaces at anodic areas, forming a thin monomolecular film with ferrous iron, preventing further corrosive reaction at the anode (5).

have a strong affinity to metal surfaces, thanks to the free electron pair of the amine nitrogen. Since FFA is an adsorption onto metal surfaces, its consumption is based upon surface area to treatment, along with replacement of stripped film-forming amines once the surfaces are initially coated. One study showed that the average surface coverage to be about 0.5 milligrams per square meter (mg/m²) and the average film thickness calculated to be about 0.5 microns (μm). Formulations have been made that are much easier to apply than ODA. Most of the products are more of a micro-emulsion today, but some are still considered as full emulsions. Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a co-surfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the “oil” may actually be a complex mixture of different hydrocarbons. The polyamine filming agents may include monoamines, diamines, tallow amines, modified octadecylamine, or others and are commonly blends. Making the polyamine products is not easy, so the intellectual property (IP) on making the products stable and effective is guarded. Emulsifiers and solvents are important, but the major active component for corrosion control is the filming agent. There may or may not be a correlation between the dose rate applied and the residual level measured, since a high percentage of dosed material is consumed, therefore we just monitor the presence of an excess. The correlation between dose rate and free film forming amine content is not strict due to adsorption/desorption processes, which is a dynamic film. Also, a residual of active FFA is typically maintained in the water and is lost to blowdown or other water loss (6, 7).

When the hydrous metal oxide film has been covered with a silica film, silica deposition stops. The film does not build on itself, so once the film is formed, additional consumption is to repair breaks in the film.

Neutralizing amines. For boiler systems, neutralizing amines are used to neutralize carbonic acid in the condensate and to raise the pH of the condensate to reduce corrosivity. In boiler systems using high-purity water, they may also be used to raise the pH of the feedwater.

Filming Amines for Boiler or Cooling Systems

Filming amines such as octadecylamine (ODA) have been used for years to provide a corrosion protective film on the surfaces of metals. Film-forming amines (FFA)

In high-purity water where then is nearly negligible demand from carbon dioxide, the applied dosage to 16

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Accounting for Consumptions of Water Treatment Chemicals continued

and losing 30 to 50% of the applied dosage to cathodic protection would be expected even after the initial cathodic film is formed.

achieve desired pH should be quite low such as 1 ppm active amine, depending upon the amine selection. Where there is high makeup and water containing significant levels of carbonate and bicarbonate alkalinity, the demand can be very high to achieve desired pH control limits. Almost all of the required dosage is based upon the amount of CO2 generated and the amount required to neutralize it, then only a small incremental amount is needed to raise the pH above 8.3. Molybdate. Sodium molybdate became popular as a cooling water corrosion inhibitor as an alternative to chromate after environmental and health concerns eliminated chromate. At low dosages such as 3 to 15 ppm molybdate as Mo, it creates a precipitated iron molybdate films and it may become more reactive to form bonded iron molybdate barriers at much higher concentrations such as 100 ppm molybdate as Mo. Molybdate will also adsorb onto bulk water ferric hydroxide, so there can be a significant loss to molybdate in high iron waters.

Nitrite (minimal). Nitrite is used as an anodic corrosion inhibitor and passivating agent in closed cooling and heating loops and hot water boiler systems. It forms a protective magnetite film. Residuals commonly range from 250 to 1,500 ppm as nitrogen dioxide (NO2), so after passivation there is minimal apparent loss of nitrite residual when maintaining a tight system. If there is water make up, consumption is proportional to makeup flow and a little more if there is disruption to the protected surfaces. When closed systems are open to the air or contaminated by nitrifying or denitrifying bacteria, then nitrite consumption and loss can be high, so nonoxidizing biocides may need to be used, or switching away from nitrite is often required. Commonly in tight systems, residuals can be maintained for extended periods of time.

Biocides

Molybdate does have solubility limitations with calcium, so its use is not recommended for cooling waters with moderate or high calcium concentrations or there may be unintended molybdate treatment losses.

Chlorine (high). Sodium hypochlorite is a common source of hypochlorous acid and hypochlorite ion used as a biocide in open evaporative cooling water systems. Both work as biocides and both go to satisfy the chlorine demand of cooling systems. In relatively “clean” waters, with typically low nutrient loading, the chlorine demand will be 3 to 6 ppm and commonly free residuals are set to be around 0.3 to 1.0 ppm to kill bacteria and algae. As an example, if there is 3 ppm demand and free residual attained is 0.5 ppm, the consumption factor is high: 3 / 3.5 = 86%.

For proper applications and after initial surface filming, consumptions are typically low, so applied levels will be close to tested residuals, which allows molybdate to also be used as a tracer in boiler and cooling water applications. Zinc (significant). The application of zinc in open recirculating cooling systems can be made at the typical range of pH levels encountered (6.5 to 9.4), but applied amounts generally go down and dependence on stabilizing polymers increases with increasing pH. Targeted residuals range from 5 ppm at low pH and down to 0.5 ppm at elevated cooling tower water pH.

If ammonia is present, then demand is much higher to attain a free chlorine residual. Breakpoint chlorination may require around 8 ppm chlorine per ppm of ammonia, so demand may be vastly high to attain free chlorine. In this case, bromine may be considered since bromamines may work better in the system than chloramine as a biocide.

The zinc is added as a cathodic inhibitor, so by design it precipitates as zinc hydroxide or hydroxycarbonate. If the pH is high, such as above 7.5, or the applied concentration is too much, and stabilization is incomplete, then bulk water precipitation can occur, which greatly increases the consumption factor. Depending upon pH, the consumption is significant

The sun does accelerate the degradation of the chlorine residual in the water. Time, heat, and metals degrade the sodium hypochlorite in the container. In waters containing significant ammonia, organics or metals that can be oxidized and when there is high bacteria loading, demand can be very much higher. 17

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Accounting for Consumptions of Water Treatment Chemicals continued

Organic chemicals such as sulfamate, cyanurate, and hydantoin can be used to help stabilize the chlorine, but should not be used in high demand waters, or overstabilization can occur. Consumption factors are still high. Bromine (high) chemistry, once attained in the cooling water, depending on the source method, will have a similar high demand before a microbiological control free or total residual level is reached, as is the case with chlorine. Some additional considerations are that bromine can be recycled in the tower water once it is reduced to bromide, so it can be reused. If there is a free chlorine residual, it may oxidize the bromide to bromine, but it then becomes part of the chlorine demand. Figure 5 shows a calibration column, which is a common way to determine chemical applied dosages.

There can also be additional loss if bromamines are formed since they are more prone to volatilize and be lost over the cooling tower. Nonoxidizing biocides (low to minimal). There are many nonoxidizing biocides to choose from. Therefore, it is necessary to look at the specific chemical, its functional method of reaction, chemical compatibility, sensitivity to pH, reaction with chlorine or other oxidants, reaction to hydrogen sulfide or other reducing agents encountered in a cooling system. As examples, DBNPA has a very short half-life if the pH is above 8.0, even though it may provide a quicker kill. Quaternary ammonium compounds are cationic compounds and may be lost to anionic dispersants. Isothiazolin may be consumed by significant levels of hydrogen sulfide or mercaptons. Typically, nonoxidizing biocides are applied at established required lethal concentrations based upon the category or type of microbiological concern and for the required kill time. This is the CT factor (Concentration x Time). With the assumption that the proper nonoxidizing biocide is selected for the specific water and conditions, the consumption factor is included in the applied dosage for the anticipated kill time, so consumptions are considered to be minimal to low. If the applications are wrong, the consumption can be significant to high.

Clarification Agents

Coagulants (high). When clarifying surface water or treating waste waters, there are various coagulants that are used to charge neutralize small, negatively charged particles and initiate the formation of larger particles. Inorganic materials such as iron or aluminum salts, or organic materials such as EPI-DMA or DADMAC are examples of some coagulants. If they are properly applied, the dosages are fairly stoichiometric based upon the demand and specifically the charged demand of the cationic coagulants. As such, when properly applied, there is nearly a 100% consumption of the coagulant used. Flocculants (high). High molecular weight polyacrylamides are commonly used for many applications to increase particle size or dewater sludge. In water clarification and wastewater applications, 18

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Accounting for Consumptions of Water Treatment Chemicals continued

Cleaners

dosages are quite small such as 0.1 to 2.0 ppm but could be higher for some needs. In dewatering applications, dosages are usually expressed in relation to pounds of dried cake produced, but the dosage is often in the 50 to 300 ppm to the liquid sludge being dewatered. For both applications, the flocculant, if properly selected, will have extremely high affinity to stay with the solids. In clarification and wastewater clarifiers, nearly 100% of the flocculant will go with the solids. Where dosages are much higher, such as in a belt press or centrifuge, there will generally be only a few to say 10 ppm flocculant residual in the filtrate from the 50 to 300 ppm applied (9). So generally, consumption of flocculants will be 95 to 100% of the amount applied.

Products that are useful in cleaning systems such as for newly installed piping, heat exchangers in cooling towers, boilers, or membrane systems can contain several different components, depending upon the application and its purpose. Consumptions will need to be considered based upon each specific application and condition encountered. For example, if EDTA or acid is used to remove a calcium carbonate highly scaled evaporative condenser, consumptions could be significant to high. If there is minimal scale, a lower concentration may be possible with much lower consumption. In general, cleaners are dosed at high product concentration such as 2 to 10%. As such, the components such as surfactants, corrosion inhibitors, acids, alkalis, or chelating agents are considered to be adequate to satisfy the demand of the condition to be cleaned, so

Table A: Typical Chemical Consumptions Based Upon Applied Dosages: Minimal: <10% Low: 10 -30% Significant: 30 – 80% High: >80% Chemical

Application

Typical Consumption

Some Factors

Polymeric dispersants

Boiler, Cooling, RO

Min to low

Water Chemistry

LP Boiler

Low to High

Hardness, Cycles

HP Boiler

Min

Hardness, Concentration

Cooling

Low

Chemistry, Conditions

Boiler

Low to High

Hardness, Cycles

Boiler with DA

Min to Low

D.O., Cycles

Boiler, no DA

Sig to High

D.O., Cycles

Organic Oxygen Scavengers

Boiler

Low

D.O., Selection

Phosphonates

Boiler, Cooling, RO

Min to Low

Selection, Application

Azoles

Cooling

Low to Sig

Surface Area, Chemistry

Surfactants

Cooling

Min to Low

Selection

Silicates

Cooling

Low

Chemistry, Conditions

Filming amines

Boiler, Cooling

Sig

Surface Area, Application

Neutralizing amines

Boiler

High

CO2, Pressures, System

Molybdate

Cooling

Low

Chemistry, Conditions

Zinc

Cooling

Sig

Chemistry, pH

Nitrite

Cooling

Min

Application, Conditions

Chlorine

Cooling

High

Water Chemistry

Bromine

Cooling

High

Water Chemistry

Nonoxidizing Biocides

Cooling, RO

Min to Low

Proper Selection

Coagulants

Clarifier, Wastewater

High

Process

Flocculants

Clarifier, Wastewater

High

Process

Cleaners

Boiler, Cooling, RO

Low

Components to Clean

Phosphates EDTA Sulfite

Notes: DA = deaerator; RO=reverse osmosis; LP = low-pressure; HP + high-pressure

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Accounting for Consumptions of Water Treatment Chemicals continued

consumptions are considered to be relatively low for the cleaning process. The spent solution is disposed of after the cleaning is complete.

Summary

This article is intended to give a perspective of what happens to water treatment chemicals in application and to help account for differences of applied dosages and expected residuals. This knowledge can be useful in designing and controlling water treatment programs. Table A is a summary of the treatment chemicals discussed and a quick-look summary of what to typically expect when applying these chemicals in water treatment programs. The table also makes it easy to broadly compare chemical consumptions.

References

Dave Christophersen is owner of Dave Christophersen Consulting LLC, and a senior consultant to AP TECH, based out of West Chester, Ohio. He has 45 years of experience in the water treatment industry, including managing water treatment programs for industrial sites for boilers, cooling systems, wastewater systems, and membranes. Having worked at Olin, Betz, Crown Solutions, and Veolia, Mr. Christophersen’s water treatment experience includes technologies for wastewater treatment, boiler water treatment and pretreatment, cooling water, and membrane technologies. He provides training, business, marketing, and technical support to the water treatment industry. Mr. Christophersen may be reached at christophersendave@gmail.com.

Keywords: BIOCIDES, BOILERS, COAGULATION, COOLING TOWERS, CORROSION, FLOCCULATION SCALING, TREATMENT CHEMICALS, WASTEWATER

1. Standish, M.J. (Winter 2022). “What Are the Do’s and Don’ts Related to the Proper Use of Fluorescent-Tagged Polymers?” the Analyst 29(1), pp. 8-23. 2. Amjad, Z.; Zuhl, R.W. (September 2002). “The Influence of Water Clarification Chemicals on Deposit Control Polymer Performance in Cooling Water Applications,” AWT 2002 Convention & Exposition, conducted September 18-22, 2002, Orlando, Florida. 3. Arkema Technical Guide (2001). “Organic Chemical: Oxygen Scavengers,” in technical guide, Arkema Inc., Philadelphia, Pennsylvania. 4. Rao, N.M.; Yu, F.Y.; Johnson, D.A.; Nghiem, N.P. (November 1993). “Microbiologically Stable Yellow Metal Corrosion Inhibitor,” European Patent Application, Application No. 93119207.2., Filing Date: Nov. 29, 1993, Applicant: Nalco Chemical Co., Naperville, Illinois. 5. PQ Corp. (n.d). “PQ Soluble Silicates: For Protection of Water Systems from Corrosion,” Bulletin 37-3, PQ Corp., Malvern, Pennsylvania. 6. International Association for the Properties of Water and Steam (October 2019). “Application of Film-Forming Substances in Industrial Steam Generators,” Technical Guidance Document, IAPWS TGD11-19. 7. International Association for the Properties of Water and Steam (October 2019). “Application of Film-Forming Substances in Fossil and Combined-Cycle Plants,” Technical Guidance Document, IAPWS TGD8-16. 8. Bursik, A. (2004). “Polyamine/Amine Treatment— A Reasonable Alternative for Conditioning High-Pressure Cycles with Drum Boilers,” Power Plant Chemistry. 9. Ormeci, B. (December 2006). “Optimization of a Full-Scale Dewatering Operation Based on the Rheological Characteristics of Wastewater Sludge,” Elsevier, Department of Civil and Environmental Engineering, Carleton University, Ottawa ON, Canada.

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Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations Matheus Paschoalino, PhD, LoongYi Tan, Donald A. Johnson, PhD, and Jun Su An, Solugen Inc.

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Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations

another common concern is the risk of oxidation by the oxidizing biocides commonly used in CTW for microbial control, reducing the efficacy of some scale and corrosion inhibitors (6).

With the ban on chromate use in Cooling Tower Water (CTW), phosphate-based technologies were introduced and became the new standard for cooling water treatment for the past several decades. Even stricter environmental regulations have followed that are associated with phosphorous-containing products. These regulatory changes have stimulated the development of novel corrosion inhibitors that are phosphorous free (P-free), including the use of compounds from natural sources, aiming for less-toxic products with a negligible negative impact on the environment (1). Last year, a new biobased polyhydroxy carboxylic acid A (PHC) was introduced that enabled formulations with low-phosphorous content for CTW. A technical article by Ngantung and Tan (2) discusses this treatment technology, including its environmental profile and its performance for treatment to control mild steel and copper corrosion. The purpose of this article is to investigate the use of this PHC treatment in non-P formulations, while improving performance and compliance with environmental regulations.

Background

Challenges of Developing Non-P Formulations The development of low-phosphorus and non-phosphorus green water treatment agents has increasingly become the focus of attention for CTW. “Green” water treatment agents generally mean that their manufacturing process is clean, and they are non-toxic to human health and the environment during their use (3). The common non-P programs for cooling water treatment often have disadvantages such as poor mild steel corrosion control, limited range of operation, and high treatment cost (4). Another non-negligible weakness when proposing a green extract or natural product for CTW is related to the limited yield production and variation of the active compound in the green extract, which often comprises a mixture of other unidentified molecules (5). An additional challenge is that the removal of P-based chemistries from formulations typically demands higher doses and associated cost increases of other additives such as oxyanions of heavy metals, polymers, and organic acids to keep an adequate range of corrosion and scale control. Regarding the increment of organic content, 23

When developing a sustainable non-P formulation, multiple aspects need to be considered beyond a single aspect of the performance, such as the compatibility with all the other actives, the toxicity and biodegradability profile of the final mixture at the proposed dosage levels, the robustness and reproducibility of the production process, and the final cost to treat.

Typical Non-Phosphorous Treatments Polymer-Based Formulations

Polymeric additives are generally first considered to be deposit control agents. However, under some circumstances they can contribute to corrosion inhibition. A large variety of polymeric additives are available for handling different challenges in treating industrial water systems such as: poly(acrylic acid), poly(methacrylic acid), poly(maleic acid), poly(acrylamide), poly(vinyl pyrrolidone), poly(2-acrylamido-2-methylpropane sulfonic acid), poly(maleic acid:acrylic acid), poly(acrylic acid:hydroxypropyl acrylate), poly(acrylic acid:2-acrylamido-2methylpropane sulfonic acid), poly(acrylic acid:2-acrylamido-2methylpropane sulfonic acid:sulfonated styrene), poly(acrylic acid:2-acrylamido2methylpropane sulfonic acid:t-butyl acrylamide), and poly(diallyldimethyl ammonium chloride) (7). The performance of these polymeric additives depends on both the water chemistry and inhibitor architecture. The main challenge of a polymer-only formulation is the associated higher cost since the dispersant and metal stabilization capacities increase according to the polymer concentration. An improvement of polymer-only treatment strategy is their combinations with metals, like zinc. Nishida et al. (8) demonstrated that the combination of low-molecularweight polymers and zinc showed similar inhibition ability as that of phosphorus and zinc treatments. The authors assumed that the polymers improve the performance by dispersing zinc effectively. Formulations Based on Carboxylic Acids

Several commercial products were introduced recently as green products in CTW formulations using carboxylic the ANALYST Volume 30 Number 4

Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations continued

acids and their polymers, such as polyaspartic acid (PASP), polyepoxy-succinic acid (PESA), poly maleic acid, xylonic acid, glyceric acid, gluconic acid, tartronic acid, glucaric acid, glucoheptaric acid, and a wide range of mixtures (3, 9-11).

surpassing 94% and 98%, respectively. Popoola et al. (20) demonstrated the synergetic interactions between iron and zinc gluconates as corrosion inhibitors in a 3.5% NaCl environment with 100% inhibition efficiency.

Carboxylic acid-based polymers plus zinc were one of the first attempted solutions for non-phosphorus treatment in the 1990s. Many providers now offer stannous chloride (tin) with a reactive starch, polyaspartic, or saccharic type acid for mild steel corrosion control. Tin can provide an improvement in mild steel corrosion control, mainly in waters that do not have an oxidizer like hypochlorite (chlorine) or bromine present (12).

A chemical manufacturerA, B developed a chemienzymatic process to produce PHCs on an industrial scale using natural feedstocks as raw materials. Unlike other traditional PHC production processes, this process does not use fermentation during the manufacture, which reduces greenhouse gas emissions (21).

Another treatment that has demonstrated potential as green corrosion inhibitors, is the use of non-toxic rare earth metal and carboxylate compounds. Sommers et al. (13) synthesized rare earth 3-(4-methylbenzoyl) propanoate (mbp) compounds (rare earth: = lanthanum [La], cerium [Ce], neodymium [Nd], and yttrium [Y]) and demonstrated that all inhibitors acted predominantly as anodic inhibitors for mild steel. In another study the compound 2-methylimidazolinium 4-hydroxycinnamate was synthesized, and corrosion studies showed it to be an effective inhibitor for steel (14).

PHC Treatments

Based on earlier work, it was found that the treatments using the alternate form of PHC were able to replace HEDP in all-organic formulations without compromise performance. This is shown in Figure 1 and Table A Table A: Alternate PHC Form as Replacement to HEDP Additive ppm Active

Gluconic and Glucaric Acids as Corrosion Inhibitors Gluconic acid- and glucaric acid-based treatments have gained attention recently because of their classifications as safer products for human health and the environment (15, 16). Both acids can be produced from the oxidation of glucose, being the first a PHC monoacid (PHCMA) and the second a diacid (PHCDA). Glucaric acid treatments have been introduced under commercial names and proprietary compositions, with multiple disclosures demonstrating improved corrosion inhibition performances versus P-based programs with minimal contributions to biological growth in cooling waters (17). Gluconates have been studied as green corrosion and scaling inhibitor for ordinary steel in cooling water, demonstrating an adsorption mechanism (18). Zeng and Qin (19) proposed multi-component phosphatefree corrosion and scale inhibitor formulation using sodium gluconate, with hydrolyzed polymaleic anhydride (HPMA), zinc ions (Zn 2+) and sulfamic acid with corrosion inhibition and scale inhibition rates

All Organic

All Organic + PHC Treatment

HEDP

PBTC

Acrylate Copolymer

TTA

1.5

PHC Alternative

Figure 1: Mild steel corrosion rates from modified “allorganic” formulations with PHCMA replacing HEDP. (Trial conditions: Temp. 40°C, Water cut 100%, rotation speed 200 revolutions per minute (rpm), air as a purge gas, electrode material C1018).

It was also shown that the performance of stabilized phosphate programs can be significantly improved through the addition of 5 parts per million (ppm) of PHCMA and the phosphate dosage can be reduced by half while maintaining a similar level of corrosion inhibition 24

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levels of HPMA as antiscalant, and acrylate copolymer as a dispersant was employed. Tolytriazole (TTA) was added as well because it is a common component of these formulations as a yellow metal corrosion inhibitor. A lower level of PASP was included in some formulations to evaluate its contribution to corrosion inhibition or synergic effect with monoacid PHCs.

(Figure 2 and Table B). Other advantages included a 50% reduction in polymer and TTA dosages (2). Table B: Alternate PHC Combined with Stabilized PO4 Additive ppm Active

Stabilized PO4

Stabilized PO4 + PHC

PO4

PyroPO4

HEDP

Acrylate Terpolymer

TTA

1.5

1.55

PHC Alternative

The water matrix composition and the formulations tested are described in Table C. The corrosion rates obtained for each condition are shown in Figure 3. Figure 3: Mild steel corrosion rates from “All-Organic non-P” formulations, with and without PASP and PHCMA.

Figure 2: Mild steel corrosion test results for stabilized phosphate formula variations. (Trial conditions: Temp. 40°C, water cut 100%, rotation speed 200 rpm, air as a purge gas, electrode material C1018).

The corrosion rates shown in Figure 3 indicate the elevated corrosivity of the water matrix and demonstrate that the addition of PASP or PHCMA individually did not significantly improve the performance of the All-Organic non-P formulation. This is something expected since previous studies indicate that PASP has been used as a corrosion inhibitor but are required in high concentrations to be effective (22).

The following sections examine the performance of phosphorous-free PHCMA and PHCMA/PHCDA treatments as corrosion inhibitors in different formulations.

Experimental Data

When both PASP and PHCMA are added together, a clear synergistic effect happens, and corrosion rates dropped ~60% to lower than 3 mils per year (mpy), confirming the feasibility of this type of formulation.

All corrosion rates were measured using a Linear Polarization Resistance (LPR) system, which consisted of a glass cell containing 1 liter (L) of synthetic concentrated cooling water, at 40°C, under agitation (200 rpm rotation speed) and air sparging with a concentric corrater probe using mild steel C1018 electrodes.

Effect of Naturally Occurring Species in CTW

Alkaline “All-Organic Non-P” Formulations with Monoacid-PHCs

In order to assess the potential of chemical company’s PHCs as non-P corrosion inhibitors for typical light-duty cooling systems, a non-P formulation consisting of lower 25

Cooling tower water contains components that diminish or improve corrosion inhibitor performance. It is common practice to add up to 0.5 milligrams per liter (mg/L) of ortho or polyphosphate to municipal water supplies for control of the corrosion of legacy lead distribution piping. One additional trial was carried out to evaluate the impact of naturally occurring phosphate the ANALYST Volume 30 Number 4

Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations continued

in tower makeup water. 2 ppm of orthophosphate was added to the matrix to simulate common levels found in CTWs. The result is shown in Figure 4.

Figure 5: Comparison of mild steel corrosion rates from “All-Organic non-P” formulations + PASP with and without PHCMA (predominantly mono-PHCs) or PHCMA/ PHCDA (mono-PHCs with higher diacid content).

Figure 4: Mild steel corrosion rates from “All-Organic non-P” formulations with PASP and PHCMA on the presence and absence of natural background phosphate (2 ppm).

The results have shown that the performance of proposed “All-Organic non-P” formulation with PASP and PHCMA would be beneficiated in waters with normal occurring levels of phosphate, reaching very low corrosion rates of 1.2 mpy.

Comparison of Mixtures of Monoacid and Diacid-PHCs

An optimized baseline formulation of “All-Organic non-P” + PASP was compared for corrosion inhibition performance of PHCMA against the chemical manufacturer’sA PHCMA+PHCDA product. The conditions are described in Table D and the performance results are shown in Figure 5.

The results demonstrated that despite a slightly faster action of the product with higher diacid content (PHCMA/PHCDA), the inhibitor composed predominantly by mono-PHCs (PHCMA) appears to produce similar final inhibition, with a modestly better trend for longer time exposures. These outcomes reveal the versatility of the organically based PHC treatmentsB, suggesting that the ultimate choice of one or another product may be function of other factors than the corrosion inhibition performance, such as: water chemistry, process conditions, anti-scaling capacity, compatibility with other chemistries and final cost to treat. Biodegradability

Another property of these products that could help the final selection among them is their biodegradability. The results of a biochemical oxygen demand 5-day (BOD5) test carried out by a third-party laboratory is shown in Table E.

Table C: Water Composition and “All-Organic non-P” Formulations Tested Additives (ppm a.i.)

Water Composition ppm (as CaCO3)

All-Organic Non-P

All-Organic Non-P + PASP

All-Organic Non-P + monoPHC

All-Organic Non-P + PASP + monoPHC

HPMA

500

Acrylate Copolymer

250

TTA

Alkalinity (HCO3 )

400

PASP

Cl -/SO42-

Counterions from CaCl2 and MgSO4

PHCMA

8.8 – 9.0

PHCMA/PHCDA

Parameter Ca Mg -

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Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations continued

The product also does not appear to interfere with the microbial control program.

Table E: Standard BOD5 Test of Organic PHC Products Additives

BOD5 (mg O2/g)

PHCMA

450

PHCMA/PHCDA

183

*Products diluted to the same activity.

PHCMA/PHCDA (higher diacid content) tend to be less biodegradable than PHCMA (predominantly monoacid PHC). According to the specificity of each system and its conditions (presence of other nutrients, chemical oxygen demand (COD), type and dosage of biocides, final disposal waterbody, wastewater system type, etc.) may be interesting to select one or another product. Biostability of PHCMA in a Real CTW Environment

To evaluate the biostability in a real CTW environment, a water sample from the cooling tower at the chemical makerA of the organic treatment was withdrawn, spiked with PHCMA, and incubated at 33°C for 5 days. The total active concentration was determined at the beginning and after experiment by a proprietary HPLC method. The results are shown in Table F.

Biostability at 33 °C

Parameter ppm

Day

Active (ppm)

Total Bacteria (CFU/mL)

155

679

< 103

668

< 103

8.99

Alkaline Non-P formulations with Metals + Monoacid-PHCs Another studied option of using Non-P formulations with PHCs was its association with transition metal ions. On the next trials the treatment was evaluated the incorporation of a classical cathodic corrosion inhibitor (Zinc, Zn), and a more recently explored alternative for Zn-free formulations (Tin, Sn) (23). The detailed tested formulations and the water matrix composition are described on Table G. The obtained corrosion-rates are shown in Figure 6.

Table F: CTW Composition and Total Active Concentration during Biostability Trial CTW composition

All the laboratory data presented were to be validated in pilot cooling tower (PCT) trials during the second half of 2022. The pilot testing has been delayed but is expected to happen in the fourth quarter of 2023.

Figure 6: Comparison of mild steel corrosion rates from “All-Organic non-P” formulations + PHCMA with 2 ppm of Zn or Sn as cathodic corrosion inhibitors.

The results show that even being more susceptible to biodegradation, the mono-PHCs levels were kept stable (< 2% variation) during 5 days in a CTW environment. Table D: Water Composition and “All-Organic Non-P” + PASP Formulations Test Results

Water Composition

Additives (ppm a.i.)

All-Organic Non-P + PASP

All-Organic Non-P + PASP + mono-PHC

All-Organic Non-P + PASP + di-PHC

HPMA

Parameter

ppm (CaCO3)

500

Acrylate Copolymer

250

TTA

Alkalinity (HCO3 )

400

PASP

Cl -/SO42-

Counterions from CaCl2 and MgSO4

PHCMA

8.8 – 9.0

PHCMA/PHCDA

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Developing an Alternative Biobased Water Treatment to Phosphorous-Based Formulations continued

Table G: Water Composition and Formulations Tested All Organic Non-P

Additives (ppm a.i.)

Water Composition

All-Organic Non-P + mono-PHC

All-Organic Non-P + monoPHC + Zn

All-Organic Non-P + monoPHC + Sn

Parameter

ppm (CaCO3)

HPMA

500

Acrylate Copolymer

250

TTA

Alkalinity (HCO3 )

400

PHCMA

Cl -/SO42-

Counterions from CaCl2 and MgSO4

8.8 – 9.0

Mg -

enables water treatment formulators to produce non-P formulations for a wide range of markets and conditions. The main outcomes in terms of corrosion inhibition performance were:

The addition of 2 ppm of Zn or Sn in association with monoacid PHCs enhanced significantly the inhibition performance of the Non-P formulation. The treatment with Sn improved performance in 50% reaching a corrosion rate of 3.9 mpy after 18 hours experiment. The treatment with Zn improved the performance with 90% reaching 0.8 mpy.

Other Desirable Features of PHCs Containing Formulas

Other than the corrosion inhibition performance, it was demonstrated on previous works (2), that the chemical maker’s PHCs have high selectivity for the formation of complexes with Fe3+, Al3+, Mn 2+, Cu+2, and other ions. These complexation properties also enable other interesting characteristics as:

Enhancement of CaCO3 inhibitors. Mitigation of iron poisoning of inhibitors. Improvement of azole performance on copper corrosion inhibition in the presence of halogen biocides allowing dosage reduction. Mitigation of copper-induced galvanic corrosion due to copper plating on susceptible metals.

All these characteristics may directly impact the final CTW cost to treat, depending on the water and process conditions, since it may favor additional savings on scaling inhibitors, dispersants, azoles, water usage and environmental fees.

Conclusions

PHC mixtures are currently being commercially produced in the U.S. from sustainable plant feedstocks via a novel carbon-negative chemienzymatic process. This process can be configured to produce a wide variety of chemical intermediates. The use of these products 28

Both mono-PHC and di-PHC are effective ingredients in non-P formulations. The all-organic PHC can provide improved carbon steel corrosion inhibition compared with polymer-only programs. The combination of PASP and PHC have improved performance versus using each by itself. The use of cathodic inhibitors, especially Zn, in conjunction with PHC presents excellent performance. The performance of the programs can be influenced by components of the CTW chemistry.

References 1. Yang, H.M. (2021). “Role of Organic and Eco-Friendly Inhibitors on the Corrosion Mitigation of Steel in Acidic Environments-A State-of-Art Review,” Molecules 26, p. 3473. 2. Ngantung, F.; Tan, L.Y. (Fall 2021). “Can a Biobased Additive Improve Performance and the Environmental Profile for Cooling Tower Formulations?” the Analyst Fall Supplement 28(4), pp. 16-22. 3. Liu, Z.; Li, N.; Yan, M.; Guo, R.; Liu, Z. (2020). “The Research Progress of Water Treatment Technology on Recirculated Cooling Water,” IOP Conference Series: Earth and Environmental Science, 508, 012041. 4. Marzorati, S.; Verotta, L.; Trasatti, S.P. (2018). “Green Corrosion Inhibitors from Natural Sources and Biomass Wastes,” Molecules 24, p. 48. 5. Xie, Y.; Chen, B.; Meier, D. (2019). “A Novel Non-Phosphorous Cooling Water Treatment Program with Robust Scaling and Corrosion Control,” Corrosion 2019, Nashville, Tennessee, NACE International, Houston, Texas. 6. LaBrosse, M.; Erickson, D. (Fall 2012). “The Pursuit of a Green Carbon Steel Corrosion Inhibitor,” Fall 2012 Analyst Technology Supplement. 7. Zuhl, R.; Amjad, Z. (2010). “Scale and Deposit Control Polymers for Industrial Water Treatment,” Chapter 5 in The Science and Technology of Industrial Water Treatment, Amjad, Z., ed., CRC Press, Boca Raton, Florida, pp. 81-104. 8. Nishida, I.; Fujita, K.; Togo, T.; Takanori, Y.; Sakamura, T. (2021). “Non-Phosphorus Treatment Technology for Cooling Water Systems, ” CORROSION 2021 virtual conference, NACE International, Houston, Texas. 9. Post, R.M.; Kalakodimi, R.P. (2017). “The Development and Application of Non-Phosphorus Corrosion Inhibitors for Cooling Water Systems,” World Energy Congress, Atlanta, Georgia. 10. 1Gao, Y.H.; Li, H.H.; Zheng, Y.X.; Zhang, L.H.; Liu, Z.F. (2020). “Application of Polyaspartic Acid Derivative in Circulating Cooling Water System with High Concentration Multiple,” Journal of Physics: Conference Series 1605,012133. 11. 1Frayne, C. (2009). “Organic Water Treatment Inhibitors: Expansion of Current Guidelines, Myths, Disinformation, and the Next Generation of Novel Chemistries – Part II,” The Analyst 16(4), pp. 24-33. 12. 1Green, J. (2020). “New Non-Phosphorus Technology Solves Decades of Issues in

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Cooling Water,” WQP October Commercial Water. 13. Somers, A.E.; Hinton, B.R.W.; Bruin-Dickason, C.; Deacon, G.B.; Junk, P.C.; Forsyth, M. (2018). “New, Environmentally Friendly, Rare Earth Carboxylate Corrosion Inhibitors for Mild Steel,” Corrosion Science, 139, p. 430. 14. Somers, A.E.; Peng, Y.; Chong, A.L.; Forsyth, M.; MacFarlane, D.R.; Deacon, G.B.; Hughes, A.E.; Hinton, B.R.W.; Mardel, J.I.; Junk, P.C. (2020). “Advances in the Development of Rare Earth Metal and Carboxylate Compounds as Corrosion Inhibitors for Steel,” Corrosion Engineering, Science and Technology, 55, p. 311. 15. Rivertop Renewables (2017). “Novel Corrosion Inhibitor Chemical Earns Regulatory Approval in Europe,” Materials Performance. 16. EPA (February 2020). “Supporting Information for Low-Priority Substance D-Gluconic Acid,” U.S. Environmental Protection Agency, Washington, D.C. 17. Christophersen, D. (2017). “Green Corrosion and Scale Inhibitors for Cooling Systems,” JCMEC ( Jubail Corrosion & Materials Engineering Forum) Technical Conference. 18. “Sodium Gluconate as Corrosion and Scale Inhibitor of Ordinary Steel in Simulated Cooling Water,” Corrosion Science 50, p. 1530. 19. Zeng, D.; Qin, W. (2012). “Study on a Novel Composite Eco-Friendly Corrosion and Scale Inhibitor for Steel Surface in Simulated Cooling Water,” Journal of Surface Engineered Materials and Advanced Technolog, 2, Article ID:20446. 20. Popoola, A P.I.; Sanni, O.; Loto, C.A.; Popoola, O.M. (2015). “Corrosion Inhibition: Synergistic Influence of Gluconates on Mild Steel in Different Corrosive Environments. Synergetic Interactions of Corrosion Inhibition Tendency of Two Different Gluconates on Mild Steel in Different Corrosive Environments,” Portugaliae Electrochimica Acta, 33,353. 21. Life Cycle Associates (2020), “Lifecycle Analysis”, Life Cycle Associates LLC, Portola, California. 22. Obot, I.B.; Ul-Haq, M.I.; Sorour, A.A.; Alanazi, N.M.; Al-Abeedi, T.M.; Ali, S.A.; Al-Muallem, H.A. (2022). “Modified-Polyaspartic Acid Derivatives as Effective Corrosion Inhibitor for C1018 Steel in 3.5% NaCl Saturated CO2 Brine Solution,” Journal of the Taiwan Institute of Chemical Engineers, 135, 104393. 23. Kalakodimi, R.P.; Turner, C.; Wills-Guy, D. (2015). “Corrosion Control for Water Systems Using Tin Corrosion Inhibitor with a Hydroxycarboxylic Acid,” U.S. Patent No. 10,174,429 B2, U.S. Patent and Trademark Office, Alexandria, Virginia.

Jun Su An is the senior director of product at Solugen. He has experience in developing new, novel and optimized solutions in various industries, including the industrial water treatment sector. This paper was presented at the AWT annual conference, which was conducted Sept. 21-24, 2022, in Vancouver, British Columbia, Canada.

Keywords: COOLING TOWERS, CORROSION, ENVIRONMENTAL, INHIBITION, PHOSPHONATES, POLYMERS, RAW MATERIALS, SCALE CONTROL, SCALING, TREATMENT CHEMICALS

Endnotes

A Solugen Inc. (Houston, Texas) is the chemical company that developed the method to produce an environmentally friendly type of PHC. B Examples of treatment products made by Solugen’s Bioforge™ containing a mixture of PHC include the AcquaCore™.

Matheus Paschoalino, PhD, is the IWT (industrial water treatment) support manager for Solugen. He received his doctorate in analytical chemistry from UNICAMP (Brazil) and UCM (Spain). He has 19 years of experience in R&D, and technical Support on IWT technologies, focusing on asset integrity and microbial control. Dr. Paschoalino has authored six patents, one book chapter and 30+ published papers and presentations from various international conferences. Dr. Paschoalino can be reached at matheus.paschoalino@solugentech.com.

Donald A. Johnson, PhD, is engaged in technical business development for Solugen. He holds a doctorate in physical chemistry and has more than 50 years of experience in the water treatment industry. Dr. Johnson is a member of the Society of Patent Holders and an inductee of the National Corporate Inventors Hall of Fame.

Uniphos 2020.pdf 1 4/23/2020 3:57:49 PM

Uniphos

LoongYi Tan is the senior director of business development at Solugen. Mr. Tan received his BS in chemical engineering from the University of California, Berkeley. Prior to joining Solugen, he was a system engineer at Theranos and a production engineer at The Dow Chemical Co. He can be contacted at loongyi@solugentech.com. CY

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Can Recent Advances in Fluorescence Improve Control of Cooling Water Chemistry? Raymond M. Post, P.E., United Water Consultants

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Can Recent Advances in Fluorescence Improve Control of Cooling Water Chemistry?

Introduction to Control and Monitoring

The performance of any chemical treatment program is only as good as the accuracy of the chemical feed dosing system and the effectiveness of the chemical residual monitoring program. Although the terms “control” and “monitoring” are related and frequently lumped together as “automation,” they are distinct in meaning and function. Chemical feed control refers primarily to the dosing rate of the applied chemicals. Several control methods have been in common usage for many years, often categorized as either “feed forward” or “feedback.” The most common feed-forward methods are “bleed-andfeed,” where the chemical feed is paced according to the blowdown flow and time; “makeup paced,” in which the chemical feed is paced on according to a makeup flow meter often in conjunction with conductivity (1); and continuous feed based on a calculated or measured blowdown flow.

on a change in sample turbidity when the polymer is precipitated or a subtle shift in blue color in response to a reagent, either of which can be inaccurate. Although it is possible to automate any of the wet chemical tests, the equipment is inherently complex, requiring sample conditioning/filtration, reagents, reagent metering pumps, sensing cells that can become stained, and spent reagent discharge. The complexity results in increased instrument costs and reduced reliability. An advantage of on-line wet chemical analysis is that it can serve both a chemical monitoring function and a feedbackbased control function. Regardless of the control method, some method of analyzing and verifying the concentration of the applied product in the water is required.

The Case for Fluorescence

Strictly speaking, feed-forward control is based on mass balance and does not require any chemical analysis, making it simpler and less costly to implement. However, in order to achieve a reasonable level of dosing accuracy, the concentration of one or more chemicals present in the applied products should always be monitored. Common chemicals used for monitoring include a molybdate tracer, orthophosphate, or a dispersant polymer, which must be regularly measured using wet chemical analysis, generally on-site using grab samples. Based on the results of the analyses, the chemical dosing pump rate is adjusted to bring the target product residuals in line with the designated control parameters. Monitoring using wet chemistry can be effective but has limitations. Specifically, it requires consumable reagents, glassware, a spectrophotometer capable of accurately measuring light transmittance at multiple wavelengths, rinse water, a timer, and a laboratory or convenient level workspace. The wet chemistry methods are somewhat expensive in terms of reagents and also time consuming. Accuracy tends to vary, depending on operator technique, water quality, and chemical interferences in the methods. Molybdate tracers add significant expense to the treatment chemistry. Orthophosphate is often inaccurate as an indicator of product dosage due to variable levels of phosphate in many makeup waters. Polymer concentration tests are usually based

Similar to wet chemical analysis, fluorescence can be used for both monitoring and feedback-based control yet offers several advantages. To a knowledgeable chemist, fluorescence is approximately 1,000 times more sensitive than ultraviolet (UV)/Vis spectrophotometric absorbance (2). Fluorescence is so sensitive that even a single photon can be detected, and the detection range can exceed three orders of magnitude without dilution. Therefore, only small amounts of fluorophore are required, making it very economical. Fluorescence is also very specific to the target compound in that only those substances that fluoresce at the excitation wavelength and emit at the detection wavelength are measured. Apart from the technical advantages, the most appealing aspects of fluorescence for cooling system operators are:

Measurement does not require any reagents, chemical handling, or disposal. Sensors are low-power solid-state devices that are portable for monitoring multiple locations. Readings are instantaneous and independent of operator technique.

What Exactly Is Fluorescence, and How

Does It Differ from Colorimetric Absorbance? Colorimetric absorbance monitoring of water treatment chemicals such as molybdate, phosphate, azoles, and chlorine involves collecting a sample, usually splitting it into “test” and “blank” vials and adding one or more reagents and pH buffers that have been developed to react with the chemical of interest. The chemical 31

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For example, one common multiparameter colorimeter for field use contains four LEDs that emit light at wavelengths of 420, 520, 560, and 610 nanometers (nm). Some better portable units have a greater number of LEDs, which improves their accuracy by enabling them to emit light at the absorbance wavelength peak of the colored complex.

reactions produce a color change in the test solution relative to the untreated blank solution. After a specified reaction time interval of a few minutes, the change in color relative to the blank is measured by a spectrophotometer, colorimeter, or visual color comparator. Although high quality laboratory benchtop spectrophotometers generally use a tungsten filament light source in conjunction with a collimator lens, monochromator prism, and wavelength selector to provide precise, tunable wavelengths, the portable colorimeters for cooling water treatment generally use low power light emitting diodes (LEDs) as light sources. LEDs by nature produce a characteristic fixed wavelength over a fairly narrow band width determined by the LED construction, requiring the meter to have several LEDs to produce multiple wavelengths required for different analytes.

As shown in Figure 1, absorbance measurements are made with the light source and photodiode detector directly opposite each other with the sample cell in between. Sample cells with longer pathlengths generally improve the accuracy of absorbance readings particularly for faint color changes. Filtering the sample also improves accuracy by reducing attenuation due to light scattering and errors associated with acidic reagents dissolving some of the suspended particles.

Figure 1: Illustration of colorimetric absorbance measurement.

Figure 2: Absorption and emission spectra with overlap profile. Source: Olympus Life Science Solutions, Reference 6.

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and Em bands which can be overcome through the use of band pass filters (“monochromators”) or compensated mathematically.

Subtle color changes, for example due to the effect of acidic or reducing reagents on iron salts, can also introduce errors in absorbance measurements. Colorimetric absorbance methods are subject to interference both from substances that interfere or interact with the color-forming chemical reactions and from substances that interfere with optical light transmission such as fine suspended particles. Although the colorimetric reactions are designed to be as specific as possible for the analyte of interest, there are many interferences. For example, the analytical procedure for one of the most common and selective of the cooling water tests, the Hach Phosver 3 Orthophosphate test, lists 12 interferences, including silica >10 milligrams per liter (mg/L) (as Si), hydrogen sulfide at any level, highly buffered samples, and high turbidity or color (3). The analysis requires one reagent and a two-minute waiting period for color development. Many other analytical tests are more complex, some requiring multiple reagents, digestion steps, and longer reaction times. All the colorimetric reactions require chemical reagents that must be purchased and inventoried as well as disposal of spent chemical solutions. The reagents themselves can also be subject to quality assurance issues. Figure 1 illustrates the colorimetric light absorbance measurement process. The primary advantage of absorbance is its versatility. Many color-producing reactions have been developed over time, enabling simple absorption meters to measure a wide range of water treatment compounds as well as common water quality parameters such as calcium, magnesium, iron, and many others. Two common handheld meters each list more than 40 analytes with more than 80 methods (4, 5). Fluorescence has been used for decades in water systems to determine flow rate, measure system volume, evaluate mixing efficiency, and study flow patterns. Fluorescence is the ability of some molecules to absorb light at a particular wavelength, referred to as the absorbance or excitation wavelength (Ex), causing the molecule to emit light at a different, longer wavelength, referred to as the emission wavelength (Em). Most fluorophores have both a primary and secondary Ex and a corresponding primary and secondary Em. As illustrated in Figure 2 (6), there is usually some spectral overlap between Ex 33

Portable fluorometers are similar to portable absorbance meters in that the light source is a low-power LED of a specific wavelength chosen to coincide with the excitation wavelength of the fluorophore. Unlike absorbance meters, the photodiode detector is located at a right angle (90°) to the excitation light source, which reduces the tendency for excitation light to interfere with the emission light sensor (Figure 3). This is the same configuration between light source and sensor that is used for nephelometric turbidity. Fluorometer accuracy tends to benefit from a shorter pathlength, in contrast to absorbance meters that are generally most accurate with a longer pathlength, especially for faint color changes. Figure 3: Illustration of simple LED-based portable fluorometer used in early cooling applications.

For organic compounds, carbon-carbon double bonds are responsible for most fluorescence. Multiple double bonds linked together (conjugated) fluoresce more strongly, especially in an aromatic structure (“benzene ring”) and even more so when the aromatic rings are linked together in a rigid structure. Consequently, common fluorophores are often based on pyrene, anthracene, naphthalene, or other polycyclic organics. The specific Ex/Em is a somewhat unique signature of each fluorescent compound. Because polycyclic hydrocarbons are not water soluble, they are modified by adding polar hydroxy, carboxyl, or sulfonic groups when used as water soluble fluorophores.

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The ability to easily detect a fluorescent tracer in cooling water checks several boxes for efficiently monitoring the performance of a chemical feed control system:

Figure 4: Examples of polycyclic organics used as watersoluble fluorophores.

1,3,6,8-Pyrenetetrasulfonic acid (PTSA)

Fluorescein

Evolution of Fluorescence in Cooling Systems The use of fluorescence for tracing water flow reportedly dates back to at least 1877 when fluorescein was used to monitor the flow of the Danube River (7). The basics of using fluorescein and 1,3,6,8-pyrenetetrasulfonic acid (PTSA) for monitoring and control in boiler and cooling water systems were first described 30 years ago (8, 9).

The initial patents for fluorescent tracer applications in cooling systems, and even the first patent for a solid state fluorometer to monitor industrial water systems (10), were granted prior to the commercial availability of LEDs capable of emitting the wavelength required for PTSA. The key enabler in the application of fluorometry to cooling systems was the development of low-power, low-cost LEDs that were capable of emitting light at the required shorter UV wavelengths. Advancements in UV LED development during the past 25 years have allowed developers to directly measure a growing number of compounds, including not only high quantum efficiency fluorophores but also some common water treatment chemicals including azoles, nitrite, and even hypochlorite at higher concentrations. Additional challenges included the selection of a fluorophore with an Ex/Em signature that is distinct from other common impurities in cooling water and is stable under typical cooling water and product conditions, including temperature, pH, other common water treatment chemicals, and chlorine and other halogens. PTSA was identified early on as meeting essentially all of those requirements with the exception of susceptibility to comparatively high molecular weight cations such as quaternary amine antimicrobials and cationic coagulants that might be carried over from a clarifier or filter.

Time saving. Results are obtained in seconds in the field with no waiting time for color development. The analysis is easily performed at the cooling tower with no need to collect a sample and take it to a lab. Some portable instruments do not even have cuvettes; just dip the meter into the cooling water, press a button, and read the product dosage. No reagents. No need to purchase and maintain reagent inventory. No chemical handling or disposal of spent solutions. Repeatable. Results are not operator or technique dependent. No need for sample dilution, DI squirt bottles, filtration, glassware, or timers.

Fluorescence can also be used as the basis for feedbackbased control systems, usually replacing makeup or blowdown flow-based feed-forward control systems. Fluorescence-based systems do not require wired or wireless signal devices to be run from the makeup or blowdown valves. The solid-state fluorescence sensor is simply placed in line with a sample flow, often together with the conductivity and pH sensors and the corrosion coupon rack. Fluorescence is also easily adapted to solid chemical feed systems for enhanced control. The simplicity and robustness of fluorescent measurement also makes it more practical for feedback control than in-line wet chemical-based systems, which require a sample line to the meter, sample conditioning, reagent and sample pumps, multiple reagent reservoirs, and a discharge line. Fluorescence can also be used as a feedback trim control to improve the accuracy of mass balance-based feed forward control systems.

Development of Fluorescent Tagged Polymers

The initial applications of fluorescence to cooling systems involved only the use of inert fluorophores, primarily PTSA. Although this was effective for monitoring the overall concentration of treatment product, it did not necessarily reflect the concentration of active ingredients, particularly polymeric dispersants that may suffer some loss due to adsorption onto solids and precipitates, nor some azoles that can be consumed by adsorption or degraded by halogens. Moreover, with only one 34

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fluorescent component, it was not possible to directly monitor the concentration of “two-drum” (two product) treatment programs that are commonly used in larger cooling water applications, apart from linking the second product to the dosing rate of the traced product.

product name apart from marketing differentiation. From a formulation and production perspective, the tagged polymer blend is even easier to manage than a PTSA tracer since it doesn’t require a separate raw material that must be precisely added to the final blend.

The next series of advancements in fluorescence monitoring involved the incorporation of a fluorescent monomer onto dispersant polymers. Fluorescent tags based on pyranine, a PTSA derivative, and naphthalimide, a naphthalene derivative, were first described more than 20 years ago (11, 12). Polymers with either tag chemistry are commercially available today, each with its advantages (13, 14). Because the monomer is covalently bonded to the polymer backbone the fluorescence travels with the polymer with the signal being attenuated or lost if the polymer is adsorbed onto particles, deposits, or solid surfaces.

In a “one-drum” formulation, the use of both an inert tracer and a tagged polymer can prove very useful in identifying unusually high polymer loss with the potential for deposition. The inert PTSA tracer indicates the concentration of the polymer product as fed, while the tagged polymer indicates the concentration of active polymer remaining in solution as an effective dispersant and scale inhibitor. For example, Figure 5 illustrates the effect of bulk water phase calcium carbonate precipitation on tagged polymer concentration as the pH is slowly increased in a stirred vessel.

While the initial tagged polymers were primarily calcium phosphate and silt dispersants (15) more recent developments include tagged calcium carbonate scale inhibitors (16) and other dispersant polymers. Since the introduction of tagged polymers, there have also been improvements in the purity of the tag precursor, reductions in the unpolymerized residual monomer, and enhancements to the quantum efficiency associated with polymer functional groups (17). Efficiencies in tag production have reduced the cost of the tagged monomer, enabling a higher mole fraction of tag to be economically incorporated in the polymer. These improvements and others have significantly improved the accuracy of tagged polymer measurements.

Formulating Products with Tagged Polymers

Existing formulations can be easily converted to fluorescent tagged polymers. Since fluorescence is easily measured at very low levels, the required amount of tag is so low that the tagged version of a dispersant polymer will carry the same Chemical Abstracts Service (CAS) Registry Number as its non-tagged counterpart. When substituting a tagged version of a polymer for its non-tagged counterpart or adding a fluorescent tracer, there is no change to its physical properties, formulatability, aquatic life effects, or performance. The Safety Data Sheet (SDS) and physical properties remain unchanged and there is no requirement to change the

When the concentration of filtered calcium decreases (green dots), the concentration of tagged polymer (red dots) also decreases sharply because it is consumed on the calcium carbonate precipitate, while the concentration of inert PTSA tracer (red triangles) remains constant. Using on-line measurements, the loss of effective, free polymer can be detected at its outset and corrective action taken before significant heat exchanger fouling can occur. In this laboratory study without heat transfer surfaces or low flow areas, most of the calcium carbonate precipitate remained in suspension. It is important to note that the polymer in this case was developed to control calcium carbonate deposition. As such, it adsorbs preferentially onto calcium carbonate particles. A polymer developed primarily for calcium phosphate control would show a similar response for calcium phosphate deposition, but it would be much less responsive to calcium carbonate deposition. The ability of tagged polymers to signal calcium carbonate deposition can be a significant advantage over organic phosphate scale inhibitors such as HEDP, PBTC, or PSO, which cannot be conveniently measured on-line. Tagged polymers can be even more useful in “two-drum” (two-component) treatment programs. In early two-drum programs, the inert PTSA tracer was typically added to the dispersant product; the corrosion inhibitor product, usually based on phosphate, was monitored using a wet chemical phosphate test.

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optic sensor in cooling water, fluorometers can become fouled by microbiological deposits, silt, and mineral scale.

A fluorescent tagged polymer enables the inert PTSA tracer to be added to the corrosion inhibitor product, while the dispersant product is monitored using the tagged polymer. Another advantage is that the tagged polymer fluorescence will reflect the free polymer in solution, which is the active polymer available to prevent deposition. By knowing precisely, the amount of active polymer in solution, the polymer dosage can be better optimized to the requirements rather than always feeding a generous excess to ensure there is enough.

Early fluorometer designs were based on enclosed cells that were difficult to examine for fouling and challenging to clean, requiring a cleaning solvent to be injected into the detector cell and hoping for the best. Newer in-line fluorometer designs are based on probes that can be easily removed, inspected, and cleaned with a cloth or cotton swab, sometimes aided by a cleaning solution.

Advancements in Fluorometer Design

Fluorometers have improved in a number of respects from the initial design represented in Figure 3. Early fluorometer designs used less expensive soft-coated optical filters that were susceptible to degradation by humidity and temperature. The in-line units contained a color-indicating desiccant, visible through a window, to indicate the desiccant condition. Dry desiccant is blue and shifts to purple-red and ultimately to white when fully saturated. Desiccants in field units were often observed to have been exhausted. Highly developed fluorometers for cooling system applications today are configured as shown in Figure 6. The current better quality fluorometers use more expensive “hard coated” optics that are impervious to humidity and resist temperatures to 77°C (170°F). The combination of high quantum efficiency fluorophores having unique Ex/Em bands with effective band-pass optical filters make the advanced fluorometers highly resistant to interference from organics in the water. There have also been improvements in the photodiode design to improve sensitivity and stability. As with any in-line Figure 5: Tagged polymer response to CaCO3 bulk water precipitation. Source: Kalakodimi, Reference 16.

As with absorbance, fluorescence is an optical measurement and is therefore subject to interferences caused by color and light-scattering particles or bubbles. It is essential to compensate for both color and turbidity in order to achieve accurate fluorescence measurements in cooling systems (18). Even in light industrial applications, the faint color associated with 1 to 2 parts per million (ppm) of iron corrosion products will significantly impact measurement accuracy in the absence of compensation. The most advanced fluorometer designs incorporate a separate LED/photodiode pair specifically to effectively overcome potential turbidity and color interferences (19, 20). The LED output, fluorophore response, and photodiode output are all temperature dependent to some degree, requiring effective compensation to achieve the best accuracy. The output of LEDs decreases significantly in response to increasing temperature in accordance with basic physics principles. The fluorescence intensity of PTSA and most other fluorophores decreases slightly with increasing temperature, in the range of 5% lower output at 40°C (72°F) higher temperature. Photodiode sensitivity in response to temperature is more complicated, depending on the type of photodiode and wavelength, but generally decreases slightly on the order of 4% over a 40°C (72°F) increase in temperature. The better fluorometers include internal temperature compensation circuity, while some may rely on an external controller or fixed temperature compensation factors based on the typical temperatures associated with the traced sample and the fluorometer LED. Fluorometer design for simultaneously measuring both the inert PTSA tracer and naphthalimide-based tagged

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that case since two signals could not be distinguished. The recent availability of high performance, low-cost microprocessors to manage multiple LED/photodiode systems and support the compensation algorithms for color, turbidity, and temperature has also contributed to enhanced fluorometer designs.

polymers has also improved significantly in recent years. Early fluorometers used a single LED, emitting light at approximately 365-nm wavelength, to excite both the inert PTSA and the polymer tag. Although the PTSA emission peak at approximately 410 nm is distinct from the polymer emissions peak at nominally 455 nm, there is considerable overlap in the two emissions spectra (Figure 2). Today, with LED costs being much lower, the more advanced fluorometers contain a separate 410-nm LED to take advantage of the secondary excitation wavelength for the polymer tag, providing much improved separation between the inert PTSA and tagged polymer responses.

Advancements in Communications

Tremendous improvements in communications capabilities have also been enablers for fluorescence and other in-line sensors. Sensors are capable of producing large amounts of useful data, but their value is significantly diminished without the means to transmit and analyze that data. In the past, the requirement to run communications wires was a major barrier to automation. Today there are numerous advanced communication methods such as cellular modems, Zigbee, and Bluetooth to transmit sensor data to the user, as well as computational capabilities to analyze the data and transform it into useful charts and alarms.

In-line and hand-held fluorometers that measure both PTSA and tagged polymer are relatively economical, currently costing 30% to 50% more than single fluorescence types. Polymers with tags based on pyranine can use the same fluorometer as used for PTSA, but a PTSA inert tracer would not be used in Figure 6: Advanced fluorometer design for cooling systems.

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Inline fluorescence monitoring sensors connected to a communications system can immediately alert personnel of a need for maintenance on a cooling system, making service calls more efficient and timelier.

Fluorescence offers the advantages of speed, efficiency, reliability, and low operating cost with no reagents. The time has come for fluorescence to take its place alongside traditional colorimetric analytical methods and flow-based control systems, to help water treatment professionals make better decisions through better data.

Analog 4-20 milliamp (mA) control loops are being replaced with digital communications protocols such as Modbus. Fluorescence sensors configured for Modbus are capable of outputting diagnostic information such as probe cleanliness as well as continuously transmitting the fluorescence data, saving time in the field and streamlining maintenance activities. Advanced in-line and hand-held sensors also have the capability to communicate wirelessly with nearby cell phones or laptops, simplifying calibration, and allowing data logged values to be transferred for further analysis and archiving.

References 1. Reggiani, G.; Young, P. (Winter 2007). “Trasar® Technology–A Review and Comparison,” The Analyst, (pp. 8-19).

Closure

The use of fluorescence as an analytical method has a 150-year history, and its use as a monitoring method for boiler and cooling systems spans the past 30 years. Fluorescence is well-suited to this application, with a sensitivity approximately 1,000 times greater than colorimetric absorbance. Only small amounts of fluorophore are required, making it very economical. Initial limitations and shortcomings have been overcome by several advances in technology that have combined to make fluorescence a highly effective and accurate method for monitoring or controlling cooling system chemistry. Prominent among these advancements are:

Advances in communication including digital Modbus, wireless cell modems, Bluetooth, Zigbee, and data acquisition and computation tools, which have combined to transform sensor outputs into actionable knowledge.

2. Geisler, G. (May 2007). “Choosing the Best Detection Method: Absorbance versus Fluorescence,” in Biocompare, retrieved from www.biocompare.com >Life Sciences Articles > Bench Tips : https://www.biocompare.com/ Bench-Tips/173963-Choosing-the-Best-Detection-Method-Absorbance-vs-Fluorescence/#:~:text=Sensitivity%3A%20The%20sensitivity%20of%20fluorescence,precious%20or%20limited%2Dquantity%20materials. 3. Hach ( January 2017). “Hach Phosver 3 orthophosphate Method 8048,” Phosphorus, Reactive (Orthophosphate, U.S. EPA Phosver 3 (Ascorbic Acid) Method, Hach Co., Loveland, Colorado. 4. Hach (n.d.). “DR900 Multiparameter Portable Colorimeter,” retrieved 08 07, 2022, from www.Hach.com: www.hach.com/dr900-multiparameter-portable-colorimeter/product-parameter-reagent?id=15684103251, Hach Co., Loveland, Colorado. 5. Pyxis Lab, Inc. (n.d.). “SP-910 Portable Watr Analyzer Proceudres Manual,” retrieved Aug. 22, 2022, 22, 2022, from Pyxis-Lab.com: www.pyxis-lab.com/ wp-content/uploads/2022/08/SP-910-Portable-Water-Analyzer-Procedures-Manual-07262022.pdf. 6. Olympus Life Science Solutions. (n.d.). “Fluorescence Excitation and Emission Fundamentals,” retrieved 08 11, 2022, from Olympus-lifescience.com: www. olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/ fluoroexcitation/. 7. Käss, W.; et al. (1998). Tracing Technique in Geohydrology, A.A. Balkema, Rotterdam, the Netherlands. 8. Avallone, S.C.; Fowee, R.W.; MacDonald, J.R.; Furibondo, N.J. (1994). “Boiler Steam Leak Detection,” U.S. Patent No. 5,320,967, U.S. Patent and Trademark Office, Alexandria, Virginia. . 9. Moriarity, B.E.; Hickey, J.J.; Hoy, W.H.; Hoots, J.E.; Johnson, D.A. (Feb. 12, 1991). “Continuous On-Stream Monitoring of Cooling Tower Water,” U.S. Patent No. 4,992,380, U.S. Patent and Trademark Office, Alexandria, Virginia.

Availability of low-power, low-cost LEDs emitting wavelengths in the UV fluorescence range. PTSA fluorophore, which remains inert in cooling system applications and has a distinct and widely separated Ex/Em spectra. Cost-effective, stable, fluorescent monomers that can be economically incorporated into dispersant polymers at higher concentration. Commercial availability of several fluorescent tagged polymers, including polymers to inhibit calcium carbonate and calcium phosphate deposition and disperse suspended solids. Ease of formulating with fluorescent-traced equivalents of common dispersant polymers. High quality hand-held and in-line fluorometers using hard-coated optics with excellent temperature, turbidity, and color compensation.

10. Alfano, J.C.; Fehr, M.J.; Godfrey, M.R.; Hoots, J.E.; Tubergen, K.R.; Whitten, J.E.; Rao, N.M. ( July 3, 2001). “Method for Using an All Solid State Fluorometer in Industrial Water System Applications,” U.S. Patent No. 6,255,118 B1. U.S. Patent and Trademark Office, Alexandria, Virginia. 11. Moriarity, B.; Wei, M.; Hoots, J.E.; Workman, D.P.; Rasimas, J.P. (Nov. 6, 2001). “Fluorescent Monomers and Polymers Containing for Use in Industrial Water Systems,” U.S. Patent No. 6,312,644 B1, U.S. Patent and Trademark Office, Alexandria, Virginia. 12. Morris, J.D.; B.E. Moriarty, B.E.; Wei, M.; Murray, P.G.; Reddinger, J.L. (Nov. 11, 2003). “Fluorescent Monomers and Tagged Treatment Polymers Containing Same For Use in Industrial Water Systems,” U.S. Patent No. 6,645,428 B1, U.S. Patent and Trademark Office, Alexandria, Virginia. 13. Brenntag (accessed in August 2023). “LumaTreat® Fluorescent Tagged Polymers,” developed by Nouryon, Amsterdam, the Netherlands, accessed at www.brenntag.com. 14. Standish, M. (Winter 2022). “What Are the Do’s and Don’ts Related to the Proper Use of Fluorescent-Tagged Polymers?” The Analyst 29(1), pp. 8-23. 15. 15. Radical Polymers. (2021). Initia® 910T Fluorescent Tagged Polymer. Chattanooga, Tennessee. 16. Kalakodimi, P.; Du, T.; Post, R. (Summer 2020). “Advances in the Monitoring and Control of Cooling System Chemistry,” Cooling Technology Institute Journal 41(2), pp. 38-48.

the ANALYST Volume 30 Number 4

Can Recent Advances in Fluorescence Improve Control of Cooling Water Chemistry? continued

17. Rodrigues, K.A. (Dec. 28, 2021). “Method of Controlling Scale in Aqueous Systems,” U.S. Patent No. 11,208,408, U.S. Patent and Trademark Office, Alexandria, Virginia. 18. Xiao, C. (2016). “Everything You Need To Know About Fluorescent Tracing in Cooling Water Systems,” retrieved Oct. 3, 2022, from https://www.pyxis-lab.com/ fluorescent-tracing-in-cooling-water-systems/. 19. Pyxis-Lab, Inc. (n.d.). “Pyxis ST-500 versus the Traditional Fluorometer,” retrieved 08 11, 2022, from youtube.com: https://www.youtube.com/channel/ UC8RqYgnwL-Vzu2TRzraqrUw. 20. Pyxis-Lab, Inc. (n.d.). “ST-500 Series User Manual V3.08-1,” retrieved 08 11, 2022, from www.pyxis-lab.com.

Ray Post has more than 45 years of industrial water treatment experience, specializing in the development, application, and evaluation of cooling water treatment programs. Prior to joining United Water Consultants in 2019, Mr. Post held several positions with ChemTreat, Betz Laboratories, and GE Water, including director of cooling technology, global technical leader for cooling water chemistry, power industry technical manager, senior technical consultant, and positions in product development, product management, and technical services. Mr. Post earned a

bachelor’s degree in chemical engineering from Princeton University in 1976. He is a licensed professional engineer and a member of the Cooling Technology Institute, ASME, and the National Society of Professional Engineers. He holds 5 US Patents and has authored more than 50 technical papers on industrial water treatment. Mr. Post may be contacted at raypostwater@gmail.com. This paper was presented at the Cooling Technology Institute’s winter conference, which was conducted Jan. 29-Feb. 1, 2023, in Memphis, Tennessee. It is published with permission of the CTI and the author. The 2024 CTI conference is planned for Feb. 4-8, 2024, in Houston, Texas (www.cti.org).

Keywords: BOILERS, COOLING TOWERS, CHEMICAL USAGE, FLUORESCENCE, MONITORING, TREATMENT CHEMICALS

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No Phosphonate? The Effective Use and Limits of Polymers Michael L. Standish, Radical Polymers, a division of MFG Chemical

No Phosphonate? The Effective Use and Limits of Polymers

2021, the Chinese government published a policy to restrict energy consumption, which dramatically impacted the production of yellow phosphorous (2). Since China now produces most of the yellow phosphorous and phosphonates such as HEDP and PBTC, this had an immediate impact upon the availability of these molecules and other phosphonate chemistries. Additionally, limited availability of shipping containers, vessels, and U.S. port congestion further limited supply and drove up costs. Given these facts, our industry finds itself at a point of limited availability of common phosphonates and pricing that is upward of 2-3X relative to historical levels.

Why Do We Need Phosphonates?

How Did We Get Here?

We have all become used to the functionality and effectiveness of phosphonate compounds in cooling water and other process water applications. For mineral scale control, phosphonates such as HEDP, PBTC, and ATMP can be highly effective and used at low concentrations versus polymers and other types of sequestrants and chelates. Some phosphonates can also provide functionality for mild steel corrosion inhibition. These include HEDP, HPA, and PSO. We can see the importance of phosphonates by examining a typical cooling water formula. It would by typical to prepare a product that would have some combination of the components listed in Table A where one or more components could be a phosphonate.

Today, we all find ourselves concerned with supply chain issues. In the water space, we have seen supply chain issues before. In times past, there were periodic tight supply of acrylic polymers due to plant shutdowns or hurricanes in the gulf coast, molybdate supply constraints and extreme price movements, or the occasional shortage of various specialty ingredients needed to put together water treatment formulations. But we now find ourselves in a time where literally everything has been impacted simultaneously, to the degree we are observing, or for such a long period of time. Three years in since the pandemic, we are all still struggling to get many raw materials and pricing levels are at an all-time high for most additives used in the water treatment industry. How did we get here? The present conditions seem to all run together between Covid-related issues, labor shortages, government regulations/restrictions, domestic and international transportation bottlenecks, port congestion, energy costs, and now war in Eastern Europe. It seems that the combination of all these things has led us to this point and created a state in the water industry that is not quickly or easily unwound.

Table A: Typical Cooling Water Formulation Components

One type of material that has been most intensely impacted has been organic phosphorous compounds that require the use of yellow phosphorous (P4). This type of phosphorous is necessary for the manufacture of phosphonate starting materials such as PCl3, PCl5, and phosphorous acid. According to statista.com (1), China is by far the largest producer of phosphate rock in the world with over 50% of global production. In September 43

Component

Function

HEDP/PBTC/ATMP

Threshold Inhibitor for CaCO3

Polycarboxylate (PAA, PCA, PMA)

Threshold Inhibitor for CaCO3, CaSO4, Crystal Modifier, and/or dispersant

Orthophosphate/ Polyphosphate

Mild steel corrosion inhibitor

Sulfonated Copolymer

Calcium phosphate stabilizer, dispersant, Transition metal stabilizer, silica/silicate control, On-line cleaning (non-ionic containing)

Organic Phosphonate (i.e., HPA,PSO or similar)

Mild Steel Corrosion Inhibitor

Metals (zinc, tin, molybdate)

Mild steel corrosion inhibitor

Azole (TTA, BZT, halogen stable, mixtures)

Yellow metal corrosion inhibitor

Tracer (PTSA, MoO4)

Formulation concentration monitoring

Acid or alkali

pH adjustment, solubility control

DI water

Diluent to 100%

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No Phosphonate? The Effective Use and Limits of Polymers continued

We can see that phosphonates are important contributors to water treatment formulas. By far, HEDP and PBTC are the most common phosphonates used in today’s cooling water treatment applications. ATMP, while highly functional, is used sparingly due to sensitivity to oxidizing biocides such as chlorine and bromine. These phosphonates are predominately used for calcium carbonate solubility management and are typically paired with polymers to extend functionality and improve control. As a quick refresher for the common phosphonates employed for scale and corrosion control, we can refer to the following summary: HEDP: Hydroxyethylidene diphosphonic acid

Most widely utilized phosphonate in cooling water systems Effective for calcium carbonate, less effective for sulfate-based mineral scales Some efficacy for mild steel corrosion control Typical dosage 2 to 5 parts per million (ppm) active in recirculating water Stabilizes CaCO3 (calcite) to about 125 to 150 X saturation (3)1 Typical use in waters with and LSI of <2.0 Forms insoluble calcium salts under severe conditions (high Ca 2+, high pH) Moderately stable to low levels of residual halogen biocide

Widely utilized in cooling water systems. Increased use in recent years due to improved economics and better functionality versus HEDP Effective for calcium carbonate, less effective for sulfate-based mineral scales Limited efficacy for mild steel corrosion control Typical dosage 3 to-5 ppm active in recirculating water Stabilizes CaCO3 (calcite) to about 225X saturation (3) Typical use in waters with and LSI of >2.0 to ~ 3.0 Does not typically form insoluble calcium salts under severe conditions. Highly stable to typical levels of residual halogen biocide

HPA/PSO: Hydroxyphosphono acetic acid (HPA), Phosphinosuccinic Oligomer (PSO)

ATMP: Amino tris (methylenephosphonic) acid

PBTC: Phosphonobutane tricarboxylic acid

Once a staple in cooling water systems, now sparingly utilized Most efficient phosphonate for calcium carbonate, effective for sulfate-based mineral scales Some efficacy for mild steel corrosion control Typical dosage 2 to 3 ppm active in recirculating water Stabilizes CaCO3 (calcite) to about 125 to 150X saturation (3) Typical use in waters with and LSI of <2.0 Does not typically form insoluble calcium salts Highly sensitive to halogen biocides. Not often utilized with oxidizers. Generates PO4

Moderate use in cooling water systems. Primarily function as mild steel corrosion inhibitors. Secondary efficacy for calcium carbonate. Typical dosage 5 to 15 ppm active in recirculating water. Typical use in waters with and LSI of >1.0 to 3.0 Requires calcium hardness to function well as a corrosion inhibitor. Can be paired with zinc to improve performance. Does not typically form insoluble calcium salts under severe conditions. HPA is highly sensitive to halogen biocides. generates PO4. PSO, much more stable to typical levels of residual halogen biocide.

The advantages of phosphonates are their functionality at low dosages, stability to oxidizing biocides (HEDP, PBTC, PSO), and contribution to mild steel corrosion control (HPA, PSO). Disadvantages include limited functionality. Phosphonates generally are threshold inhibitors but can be poor crystal modifiers and have little to no dispersion properties when compared to polymers. Phosphonates also contain phosphorus, which limits or excludes their use in applications requiring low to no phosphorus. However, the primary issues in today’s market are availability and cost of phosphonates. These current drivers highly support the need for 44

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No Phosphonate? The Effective Use and Limits of Polymers continued

typically require a lower dosage to inhibit the formation of calcium carbonate than polymers. However, when used at an effective dose, maleic-based polymers such as PEPMA can exceed the control limits (i.e., calcite saturation) when compared to these phosphonates.

finding alternative technologies. One of the primary technologies positioned to replace phosphonate is polymers. More specifically, a newly patented enhanced polymaleic acid (PEPMA) is a great candidate. To examine how PEPMA stacks up; we first need to understand the basics of how these materials function.

Common Definitions and Mechanisms

The author presented a technical paper (4) at the 2014 AWT annual conference that gave an overview of common definitions and mechanisms for scale control. These will be used as we examine how we can evaluate alternate technologies to phosphonates for mineral scale control. One of the most important concepts to understand when selecting an additive for mineral scale control is Threshold Inhibition, which is the extension of solubility of an otherwise insoluble salt beyond its saturation limits using an additive at

sub-stoichiometric levels. This concept of sub-stoichiometric functionality is very important and is what differentiates additives such as polymers and phosphonates from materials that function according to strict stoichiometric ratios such as EDTA. There are a few other key aspects of threshold inhibition that are important to recognize. Generally, threshold inhibition is a temporary effect with respect to time. For example, if uninhibited (untreated) water takes 60 seconds (sec) to begin to precipitate calcium carbonate in a given set of conditions (i.e., pH, temperature, calcium concentration, carbonate concentration….) and the same water, once treated, extends this time to 1 hour (hr), then inhibition has occurred with respect to time. The extent and duration of threshold inhibition can be related to a number of factors or conditions. These include, but are not limited to:

Driving force for precipitation (i.e., pH, temperature, concentration of scale forming ions) Particular efficacy of the selected inhibitor Other water impurities (both dissolved and suspended) Rate of water concentration or evaporation Frequency of additive dosage

For calcium carbonate threshold inhibition, phosphonates such as HEDP, PBTC, and ATMP are usually more efficient than even the best available polymers. There is a nuance in the commentary here regarding “efficient.” Specifically, phosphonates will 45

Stabilization can be a tricky and controversial topic within the discussion of scale control. Polymers can function as stabilizers whereas phosphonates typically do not provide this functionality. The concept of stabilization can have two meanings with respect to polymer interactions with metal ions: Colloidal stabilization is where precipitation in a fluid (water) occurs; however, the polymer or other additive prevents agglomeration of particles beyond 1 micrometer (µm) in size. These particles are thus stabilized via electrostatic interactions with the polymer and remain suspended throughout the water phase. The next paragraph offers a second definition for stabilization. These sub-micron particles are typically not visible to the naked eye. A notable exception to this is stabilized iron particles, which can be visible due to the orangebrown color associated with most oxidized (Fe3+) iron complexes. Colloidal stabilization can fail due to physical or chemical changes in the fluid, which results in particulate agglomeration beyond 1 µm in size and bulk settling of the precipitate. The term stabilization can also be a synonym for sequestration where a coordination complex between the polymer and soluble ions or surface interaction between the polymer and forming crystal lattices occurs and prevention of precipitation is achieved. In this case, threshold inhibition is not the prevailing mechanism since stoichiometry is undefined. Iron stabilization, calcium phosphate stabilization, and zinc stabilization are all relevant examples. Particulate dispersion may be the most straightforward of the concepts for scale control. A formal definition of particulate dispersion is where a mixture of finely divided particles, called the internal phase (often of colloidal size) is distributed in a

continuous medium, called the external phase. More simply stated,

particulate dispersion is a suspension of particulates in an aqueous solution. These can be inorganic (i.e., calcium carbonate), organic (i.e., biomass, oil, organic debris….) or a mixture of the two. Polymer composition and Mw are key determinants in deriving functionality for effective particulate dispersion. the ANALYST Volume 30 Number 4

No Phosphonate? The Effective Use and Limits of Polymers continued

Crystal habit modification is the basis for the control of mineral scales such as calcium carbonate. A crystal habit is defined as the normal size and shape of a precipitated substance in a given set of environmental conditions. The formation of crystals such as calcium carbonate and their subsequent deposition onto surfaces follow a simplified process of nucleation (Figure 1), lattice formation and propagation (Figure 2), Bulk precipitation (Figure 3), and surface deposition (Figure 4). Crystal Habit modification can be described in instances where a “poison” such as a polymer, phosphonate, or other contaminant disrupts normal lattice formation. The crystal lattice poison, in turn, produces crystals that either tend to re-dissolve or precipitate in abnormal forms.

Figure 3: Step 3—Bulk precipitation.

Figure 4: Step 4—Surface deposition.

Figure 1: Step 1—nucleation.

Metal Surface

Tube/Pipe Interior

Deposition - Maximum Surface Contact Area

Figure 2: Step 2—Lattice formation and propagation.

Table B: Simplified Definitions Additive Simple Definition Functionality

Threshold Inhibition

Extension of solubility of an otherwise insoluble salt beyond its saturation limits using an additive at substoichiometric levels.

Stabilization

Colloidal stabilization is where precipitation of a substance occurs, but the additive prevents agglomeration of particles beyond 1 micron in size. Stabilization can also be a synonym for sequestration where coordination complexes between the additive and soluble ions or forming crystal lattices are formed and prevention of precipitation is achieved.

Particulate Dispersion

Particulate dispersion is a suspension of particulates in an aqueous solution. These can be Inorganic (i.e., calcium carbonate), Organic (i.e., biomass) or a mixture of the two.

Crystal Habit Modification

Crystal habit modification is where a “poison” such as a polymer, phosphonate, or other contaminant disrupts normal formation and produces crystals that either tend to re-dissolve or precipitate in abnormal forms.

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No Phosphonate? The Effective Use and Limits of Polymers continued

point of view, this will roughly translate to an Langelier Saturation Index (LSI) limit of about + 1.5 to 2.0 for HEDP and + 2.5 to 3.0 for both PBTC and PEPMA. One important note is that typical dosages for HEDP and PBTC range between 3 to 5 ppm active in the cooling tower recirculating water where about 8 to 12 ppm active PEPMA is required in high calcite saturation applications. PEPMA can be applied at lower dosages at lower calcite saturation and where holding

Now that we have reviewed what types of functionalities are important for mineral scale control, we can compare how the patented enhanced polymaleic acid (PEPMA) compares to common phosphonates such as HEDP and PBTC. Table C provides an overview comparison. For threshold inhibition, it can be observed that HEDP is effective to a maximum of 150X calcite saturation, whereas PBTC and PEPMA can be effective to 225-250X calcite saturation (3). From a simple index

Figure 5: Left—Untreated calcite; Right— calcite precipitated in the presence of PEPMA.

Table C: Comparative Use of Phosphonates versus PEPMA Functionality Type

Performance Benefit

HEDP

PBTC

PEPMA

Threshold Inhibition

Extends stability/solubility of salt beyond normal saturation limits.

To 150X Calcite Saturation

To 225-250X Calcite Saturation

To 225-250X Calcit5e Saturation

Crystal Modification

Distorts crystal habit (normal shape) such that less agglomeration and adherence is observed. +

++++

Particulate Dispersion

Distributes particulates in the continuous phase (water) to maintain suspension.

Typical Dosage

Circulating water as active

3-5 mg/L

8-12 mg/L

Table D: Levers for Calcium Carbonate Control Lever

Implications

Lever #1 – pH Control/Acidification

Reduction in pH reduces the calcite saturation/LSI Handling of mineral acids such as H2SO4 Possibility of creating sulfate scales (CaSO4, BaSO4, SrSO4)

Lever #2 – Reduction of Cycles/ Concentration Ratio

Reduction of cycles reduces concentration of scale-forming components; therefore, reducing calcite saturation/LSI Reduction in cycles reduces holding time, thus reducing the inhibitor burden.

Lever#3 – Partial Replacement of Phosphonate with PEPMA

Allows formulator to conserve available phosphonate Benefit of both functionality types

Lever #4 – Total Replacement of Phosphonate with PEPMA

Effective replacement up to 225 to 250X calcite saturation Best-in-class crystal habit modifier for calcium carbonate Zero phosphorous Halogen stable Readily available

the ANALYST Volume 30 Number 4

No Phosphonate? The Effective Use and Limits of Polymers continued Is Testing for Legionella pneumophila or Legionella Species Better for Routine Monitoring? continued

33. Petrisek, R.: Hall, J. (2018). “Evaluation of a most Probable Number time is reduced such as RO and once-through cooling Method for the Enumeration of Legionella pneumophila from North American Potable and Nonpotable Water Samples,” Journal of Water and applications. Health 16(1), pp. 25-33, https://doi.org/10.2166/wh.2017.118.

34. Rech, M.M.; Swalla, B.M.; Dobranic, J.K. (2018). “Evaluation of Quantification of Legionella pneumophila from PBTC Non-potable For Legiolert calcite for crystal modification, HEDP and do Water,” Current Microbiology, 75, pp. 1282-1289, accessible at https://doi. haveorg/10.1007/s00284-018-1522-0. some effect versus an untreated blank. However, the

35. Barrette, I. (2019). has “Comparison of Legiolert and a Conventional Culture PEPMA material best-in-class functionality as a crystal Method for Detection of Legionella pneumophila from Cooling Towers in habitQuébec,”, modifier. Figures and 6 show a comparison Journal of AOAC5International 102(4), pp. 1235-1240,between accessible at https://doi.org/10.5740/jaoacint.18-0245. untreated calcite crystals and those treated with PEPMA

36. Scaturro, M.; Buffoni, M.; Girolamo, A.; Cristino, S.; Girolamini, L..; Mazzotta, M.; Sabattini, M.A.; Zaccaro, C.; Chetti, L.; Laboratory, M.A.; Bella, A.; Rota,are M.C.; M.L. (2020).good “Performance of Legiolert Phosphonates notRicci, particularly dispersants or Test versus ISO 11731 to Confirm Legionella pneumophila Contamination in suspending aidsSamples,” for mineral scale or other water borne Potable Water Pathogens, 9, accessible at https://doi. org/10.3390/pathogens9090690.

particulates. Best-in-class particulate dispersants are 37. Inoue, H.; Baba, M.; Tayama, S. (2020). “Evaluation of Legiolert for typically polymeric and will have an molecular Quantification of Legionella pneumophila fromaverage Bath Water Samples,” Biocontrol Science 25(3), pp. 179-182, https://doi.org/10.4265/bio.25.179. weight between ~4,500 daltons (Da) and ~30,000 Da. 38. Monteiro, S.N.; Robalo, A.M.; Santos, R.J. (2021). “Evaluation of These materials will also tend to have sulfonation and, Legiolert™ for the Detection of Legionella pneumophila and Comparison with Spread-Plate Culture and qPCR Methods,” Current Microbiology, 78, in many cases, a non-ionic or hydrophobic co-monomer. pp. 1792–1797. https://doi.org/10.1007/s00284-021-02436-6. The catch-22 here isI.;that these typesI. (2021). of materials are Study 39. Checa, J.; Carbonell, Manero, N.; Marti, “Comparative Legiolert with ISO 11731-1998 poorofthreshold inhibitors and Standard crystal Method-Conclusions modifiers for from a Public Health Laboratory,” Journal of Microbiological Methods, 186, https:// doi.org/10.1016/j.mimet.2021.106242. calcium carbonate. HEDP and PBTC are discrete, 40. McCuin, R.M.;molecules Bartrand, T.A.; Clancy, J.L. (2021). pneumophnon-polymeric and PEPMA is “Legionella a very low ila Recovery Using Legiolert and a Traditional Culture Method. AWWA Water Science, e1228, https://doi.org/10.1002/aws2.1228.

41. Boczek, L.A.; Tang, M.; Formal, C.; Lytle, D.; Ryu, H. (2021). Comparimolecular polymer. Table C illustrates how son of Twoweight Culture Methods for the Enumeration of Legionella from Potable Samples,” Journal of Water Health 19(3), thepneumophila phosphonates haveWater essentially no functionality as pp. 468–477, https://doi.org/10.2166/wh.2021.051. particulate dispersants while the PEPMA has limited 42. Lucas, C. E.; Taylor, T.H., Jr.; Fields, B.S. (2011). “Accuracy and Precision of Legionella Isolation by U.S. Laboratories in the ELITE Programeither Pilot efficacy due to its low molecular weight. Typically, Study,” Water Research 45(15), pp. 4428–4436, https://doi.org/10.1016/j. phosphonates or PEPMA would be paired with a higher watres.2011.05.030. molecular weight copolymer to add particulate dispersion when indicated. Jeff Bates is the strategic marketing

manager for Premise Water at IDEXX. In

Calcium Carbonate his role, he isControl responsible for promoting

At this point in our discussion, we have mainlyin premise testing for waterborne pathogens considered an “either/or” decision regarding use of plumbing systems globally andthe the IDEXX either phosphonates or polymers for calcium carbonate culture tests Legiolert and Pseudalert. He control. However, there other options to consider. holds a bachelor’s degree in are environmental studies from Table D summarizes these options. Middlebury College and received his MBA from the Darden School of Business at the University of Virginia. Mr. Bates Induction Experiments can be contactedTime at Jeff-Bates@idexx.com. When discussing inhibition, example This article is based on a threshold paper presented by the authoran at the 2021 AWT Annual Convention & Exposition, which was conducted September 22–25, was described where uninhibited (untreated) water 2021, in Providence, Rhode Island. takes 60 sec to begin to precipitate calcium carbonate in a given set of conditions and the same water, once

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35 48

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No Phosphonate? The Effective Use and Limits of Polymers continued

treated, extends this time to 1 hour. This is an example of induction time or the time in which an additive delays the onset of precipitation. It is important to understand that neither phosphonates nor polymers prevent calcium carbonate formation. Instead, they provide a temporary increase in stability of calcium carbonate. This is typically recognized as an increase in apparent solubility within the observed window of time. This can be demonstrated in one way by looking at additive dosage versus time. For example, we could have the exact same water chemistry and temperature conditions in a once-through cooling system and a recirculating cooling system. In the once-through system, we may observe that the average time for the water to pass through the condenser is about 10 sec, while in the recirculating system our holding time might be 48 hr. In the oncethrough system, we may require 0.5 ppm active or less of the additive to “inhibit” calcium carbonate where in the recirculating system, we might need 5 to 10ppm active to achieve the same results. The only difference here is time. To further make this point, we can look at the situation in reverse. If we were to add 0.5 ppm active additive to our recirculating water, we would likely see precipitation and deposition of calcium carbonate. In this instance, we would consider that the additive was not effective as a calcium carbonate inhibitor but our issue how we looked at dosage versus time. The main point here is that polymers and phosphonates do not infinitely control solubility of scale. They delay the onset of precipitation (induction time). Induction time is impacted by many variables, including additive dosage and conditions that impact the driving force for scale precipitation such as temperature, pH, concentration of scale-forming ions, co-precipitation, perturbation, and surface characteristics. In practical use, we would tend to add enough or excess of the additives in a given combination of conditions and time to ensure we maintained stability for the scale forming species.

CaCO3. This technique is one of the simplest ways to screen additives in a lab environment. Another tool that can be used is turbidity. As insoluble calcium carbonate forms, we observe an increase in turbidity that indicates precipitation has occurred. A third method would be to look for mass balance changes in calcium and/or alkalinity via water analysis. This method is least preferred as continuous collection and analysis of water samples is cumbersome and often impractical due to water stability issues or inconsistencies with ion-specific electrodes. Lastly, we can also use a tool called a Quartz Crystal Microbalance (QCM). In these instruments, a quartz crystal is set to oscillate at a specific frequency that is measured in Hertz (Hz). The instrument has a quartz crystal resonator that measures the change in frequency as there is deposition of foreign matter onto the crystal. This is an extremely sensitive technique that can measure down to micrograms per square centimeter (µg/cm2). Where changes in pH, observation of turbidity or even water chemistry analysis are lagging indicators of scale formation, use of the QCM is an extremely valuable tool for measuring real time changes and observing the onset of scale formation and deposition. Induction time work presented in this article includes both experiments using pH inflection as well as QCM deposition measurements. In the pH inflection work, a solution containing 800 ppm calcium (as CaCO3) was heated to 50°C was added to a separate solution containing 800 ppm alkalinity as CO32, which was also heated to 50°C. The resulting water is shown in Table E, Table E: Induction Time Conditions— pH Inflection

There are several ways to compare additives using induction time experiments. For calcium carbonate, we can look for a pH inflection that indicates the onset of precipitation. As calcium carbonate forms in waters that are not highly buffered, we will observe a decrease in pH shortly after the precipitation as we are effectively removing alkalinity from the water via the formation of

Test Parameter

Range

Target pH

8.8 to 9.0

Temperature

50°C

Calcium Concentration

400 ppm calcium (as CaCO3)

Alkalinity

400 ppm (as CO32-)

Calcite Saturation

~188X

LSI

~2.73

Figure 6 shows the induction time for an untreated blank 49

the ANALYST Volume 30 Number 4

No Phosphonate? The Effective Use and Limits of Polymers continued

sample in these conditions. At about 2 minutes (min), a pH inflection is observed, indicating the precipitation of calcium carbonate. It can also be observed that the desired pH range of 8.8 to 9.0 was not reached in the untreated blank. This is a good indication that precipitation occurred before the lagging indicator of a pH inflection was measured in the sample.

Table F: Induction Time Conditions—QCM Analysis

Figure 6: Induction time for an untreated blank—pH inflection.

Figure 7 shows the comparison in the same water conditions of HEDP, PBTC and PEPMA. The phosphonates were treated at 5 ppm active, whereas PEPMA was treated at 10 ppm active. It can be observed that HEDP shows a pH inflection at ~ 350 min, whereas PBTC and PEPMA do not show failure over the course of the 600-min (10 hr) evaluation period. Figure 7: Induction time using HEDP, PBTC, PEPMA — pH inflection.

Test Parameter

Range

Target pH

8.9 to 9.3

Temperature

50°C

Calcium Concentration

425 ppm calcium (as CaCO3)

Alkalinity

255 ppm (as CaCO3)

Calcite Saturation

~153X

LSI

~2.81

Additive Dosage

500 ppb (0. 5ppm as active)

Figures 8 and 9 show the results of the experiment. Changes in frequency can be observed in Figure 8. For the untreated blank, we can see the frequency decrease at about 10 to 15 sec after the solutions were mixed. Similarly, HEDP shows an early onset of a small amount of precipitation as indicated by the inflection change at about 5 sec after the solutions were mixed. What is different here is that HEDP does not continue to show evidence of precipitation throughout the duration of the test (~150 sec). The best performer was the PEPMA/Copolymer mixture that shows no evidence of precipitation until about 120 sec into the test. In this particular application, the additive is only required to control precipitation for 10 to 20 sec. Figure 9 shows the mass change or amount of deposition in µg/cm 2. We can observe here that the untreated blank shows greater than 9 µg/cm2 deposition of calcium carbonate over the duration of the test, while HEDP shows around 0.5 µg/cm2 and the PEPMA/Copolymer mixture shows no evidence of deposition. Figure 8: Induction time blank, HEDP, PEPMA/Copolymer mixture—QCM analysis—delta frequency. Δ F (Hz) Vs . Time (S econds ) 200

Blank

500 ppb PEPMA/Copolymer Mixture

500 ppb HEDP

150 100

SOLUTIONS MIXED (30 SECONDS)

QCM Testing was used to compare an untreated blank to HEDP and a mixture of PEPMA and copolymer in a once-through utility application. Similar to the pH inflection experiments, a calcium and separate alkalinity solution were prepared and heated to 50°C. These were treated as indicated and mixed starting at 30 sec. The onset of precipitation of calcium carbonate was measured by frequency changes using the QCM. Table F shows the conditions of the evaluation. 50

Δ F (Hz)

50 0 -50 -100 -150 -200

Time (Seconds)

the ANALYST Volume 30 Number 4

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120

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No Phosphonate? The Effective Use and Limits of Polymers continued

Figure 9: Induction Time Blank, HEDP, PEPMA/Copolymer Mixture—QCM Analysis—Delta Mass (µg/cm2). Δ m (µg/cm^2) Vs . Time (S econds )

Blank

500 ppb HEDP

500 ppb PEPMA/Copolymer Mixture

Δ m (µg/c m^2)

SOLUTIONS MIXED (30 SECONDS) 1

-1

100

150

200

250

300

Time (Seconds)

Conclusions

The water treatment industry has historically relied upon phosphonate technologies for mineral scale and, in some instances mild steel corrosion control. Over the past 12 to 18 months, unreliable raw materials supply has necessitated the need for alternatives to phosphonates. This is particularly true for staple products such as HEDP and PBTC. Water treatment professionals have several operational levers such as pH control and limiting cycles to help overcome some of the issues with limited phosphonate supply. Additionally, the functionality of polymers provides a viable alternative due to their efficacy as threshold inhibitors, crystal modifiers, and particulate dispersants. Recently, PEPMA has proven to be an effective alternative as shown in laboratory experiments and through use in the field.

References 1. statista.com (2022). “Phosphate Rock Production Worldwide in 2022, by Country,” accessed at https://www.statista.com/statistics/681617/phosphate-rock-production-by-country/.

List of Abbreviations:

Daltons: Da ATMP: amino tris (methylenephosphonic) acid CaCO3: calcium carbonate CaSO4: calcium sulfonate HEDP: hydroxyethylidene diphosphonic acid Hour: hr HPA: hydroxyphosphono acetic acid LSI: Langelier Saturation Index Minute: min PEPMA: patented enhanced polymaleic acid PBTC: phosphonobutane tricarboxylic acid PSO: phosphinosuccinic oigomer QCM: Quartz Crystal Microbalance Second: sec Michael Standish is vice president – Water Additives at MFG Chemical, LLC. Previously, Mr. Standish was founder of Radical Polymers, LLC, a business designed to specifically develop and provide technologies to the independent water treatment community. He has 36 years’ experience in water treatment additive design, development and evaluation. Prior to forming Radical Polymers, Mr. Standish served as senior business manager for International Specialty Products and Global Business Manager for National tarch’s Alco Chemical business. He has served on the AWT board and holds a BS in chemistry and master’s in business administration from the University of Tennessee at Chattanooga. Mr. Standish may be contacted at mike.standish@radicalpolymers.com. This paper was presented at the AWT annual conference, which was conducted Sept. 21-24, 2022, in Vancouver, British Columbia, Canada.

1. argusmedia.com (Sept. 15, 2021). “China’s Yunnan Sets Energy Limits for Fertilizer Sector,” accessed in 2022 at https://www.argusmedia.com/en/ news/2254118-chinas-yunnan-sets-energy-limits-for-fertilizer-sector. 1. French Creek Software (n.d.). “Cooling Water Treatment,” accessed at https:// frenchcreeksoftware.com/WaterCycle/, French Creek Software, Valley Forge, Pennsylvania.

Keywords: COOLING TOWERS, INHIBITION, PHOSPHONATES, POLYMERS, RAW MATERIALS, SCALE CONTROL, SCALING, TREATMENT CHEMICALS

2. Standish, M.L. (2014). “Ground Up: Designing New Polymers for Independent Water Treatment Companies,” AWT annual conference, Oct. 29-Nov. 1, 2014, Fort Worth, Texas.

the ANALYST Volume 30 Number 4

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Discovering AWT Pyxis Lab, Inc.

21242 Spell Circle Tomball, Texas 77375 (866) 203-8397 www.pyxis-lab.com process water, wastewater, municipal drinking water, food and beverage, aquatics, and agricultural applications.

Company History: Founded in 2013 by Dr. Caibin Xiao, Pyxis Lab started in Holliston, Massachusetts. After a decade, the company has grown and is currently operating its global headquarters near Houston, Texas, with international locations in Spain and China. The company offers inline sensors, handheld analytical devices, and fluorescent tracing chemicals. Current Business: Pyxis makes fluorescent tracing chemicals. Its inline sensors and control packages are capable of communicating with receiving devices in both analog and digital (MODBUS) formats with Bluetooth® wireless configuration, diagnostics, and calibration via the firm’s mobile and desktop app. Company products have been installed in more than 20,000 locations across multiple industries within the last ten years. The goal of installations is to control chemical dosing, improve process control, and to reduce the environmental impact. Pyxis offers EPA-ISO-compliant technologies, including advanced monitoring technology globally for use in a number of water treatment areas, including cooling and

Turbidimeter in a municipal drinking water plant.

Business Locations: The company offers its products globally with sales teams in the U.S., Europe, and Asia. It has business operations in Tomball (Houston area), Texas; Barcelona, Spain; and Shanghai and Changzhou, China. It manufactures its products at its headquarters in Texas as well as both locations in China. Recognition and Involvement: Pyxis joined AWT in 2016. In 2022, Pyxis received the AWT Innovation Award for its auto-compensating inline sensor technology. Company president Dr. Xiao accepted the award. Top Executives: Dr. Xiao, president and founder; Jeff Deak, chief commercial officer; Matt Mauch, chief executive officer; Gene Donachie, VP of new business development; Diana Cruz, EMEA sales director; Hua Zhou, APAC general manager; and Jake Deak, marketing director.

Pyxis Lab’s global headquarters in Tomball, Texas.

the ANALYST Volume 30 Number 4

Discovering AWT continued

SNF Holding Company 1 Chemical Plant Road Riceboro, Georgia 31323 (912) 884-3366 www.snf.us

Company History: SNF was founded as a privately held company in 1978 by Rene Pich and Hubert Issaurat in St. Etienne, France, to manufacture polyacrylamide-based, water-soluble polymers for the rapidly growing water treatment market. In 1987, SNF purchased property in Riceboro, Georgia, to focus on the U.S. market. In 1990, SNF purchased Pearl River Polymers Inc. to broaden its product line to include organic coagulants. SNF purchased Polypure in 1995 to enter the U.S. municipal market, and Secodyne in 1996 to create Polydyne Inc. Current Business: SNF is a specialty chemical company that has become the global leader in the sales and manufacturing of polyacrylamide-based flocculants and coagulant polymers for the water and wastewater treatment markets. SNF has a variety of business units for selling and supporting the municipal water and wastewater, oil and gas, mining, paper, personal care, home care, industrial and institutional, agriculture, textiles, and civil engineering/construction markets. This is accomplished by utilizing direct (to end users and authorized distributors) and indirect (through industrial water treatment resellers) channels to those markets.

SNF produces a complete polymer product line, which includes cationic, anionic, and nonionic polymers, supplied in liquid emulsion, solution, and powder forms. The company also offer a complete line of other chemistries, such as monomers, polyacrylates, polyDADMACs, polyamines, metal precipitants, and dispersants. SNF’s production has grown from 9,000 metric tons (MT) in 1978 to more than 1,500,000 MT in 2022. Business Locations: SNF’s North American headquarters is based in Riceboro, Georgia, and has manufacturing plants in Riceboro; Plaquemine, Louisiana; Pearlington, Mississippi; and other manufacturing sites across the U.S. The SNF Group has its corporate headquarters based in Andrézieux, France, with major production facilities in France, the U.S., China, the U.K., India, and South Korea. They are also expanding manufacturing to Brazil and Canada. All SNF locations are ISO9001(2008) certified, members of Responsible Care®, and practice Lean/Six Sigma® for continuous improvement. Top executives: Rene Pich, co-founder; Pascal Remy, CEO and chairman; John Pittman, president of SNF North America; and Marco Giuliani, VP of SNF Canada.

SNF corporate headquarters Andrézieux, France.

the ANALYST Volume 30 Number 4

Discovering AWT continued

Spectra Colors Corp.

25 Rizzolo Road Kearny, New Jersey 07032 (201) 997-0606 www.SpectraColors.com Company History: Spectra Colors Corp. was founded in 1987 by Luis Marrero, with a simple philosophy of providing reliable service, high quality dyestuff, and strong technical support. These traditional values have not changed and are as important today as they were when the company was founded. Over the years, Spectra Colors. has grown from a regional American company to become a dye supplier with a global outreach. Current Business: Spectra Colors is a global supplier of specialty dyes/colorants for a variety of industries and applications. Examples include inks for printing and ball point pens, coatings, food, drugs, cosmetics, paper, water, household products, detergents, soaps, wood stains, paints (finger and spray), water treatment products, and others.

For water treatment, the firm offers dyes and pigments for the water treatment and other specialty applications, including a full line of specialized dyes and pigments for plumbing /piping tracing, leak detection, pollution studies, closed systems and other water treatment uses. Other applications include brand identification or product differentiation to avoid application errors. The company’s laboratory employs current technologies to custom design products to customer specifications. Business Locations: The company’s plant in New Jersey serves both domestic and international customers. Recognition and Involvement: Spectra Colors has been an AWT member since 2012. Top Executives: Alexis Capik, president; Chris Almonte, general manager; Sal Harfouch, lab manager.

the ANALYST Volume 30 Number 4

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Making a Splash

Tanner Chance

Corporate Sales Representative at Brainerd Chemical Company What inspired you to begin volunteering with AWT?

Why would you encourage others to consider volunteering?

I was brand new to the water treatment industry with absolutely zero experience or knowledge. I was nudged by one of my co-workers to join a subcommittee and did not know really what to expect. Our company itself is new to the water treatment industry, so for me to be one of the first to jump into AWT and begin volunteering has truly been an awarding experience.

Being a volunteer not only allows your ideas and voice to be heard but gives you the opportunity to hear so many different ideas and voices. It allows you to be a part of a group that is open to hearing and listening to problems or solutions that you may be able to bring to the table. It also allows you to stay in tune to what is happening throughout the water treatment industry you can bring value back to your own company with updates.

What has been the most fulfilling aspect of your volunteering experience?

Could you share details about a current project you or your committee are involved in?

The ability to have such a strong network of connections to reach out to whenever I run across a unique or interesting situation. Through volunteering, I have met so many different people that handle so many different projects, that I know I have numerous people to reach out if I have questions. In an industry that is constantly gaining new innovations and technology, it is extremely beneficial to hear different techniques that are working in certain applications. Also, the monthly meetings just allow a great chance to understand what is going on throughout the industry and what potential issues could be on the horizon.

A current project that I am a part of is why wastewater treatment is so important and why everyone needs to add this skill to their treatment knowledge. Having no prior water treatment experience before volunteering, it has been fascinating to hear about the stigma of wastewater throughout the industry. With me being clueless to the concept, I was able to help generate basic questions to help construct a sales pitch as to why ever water treater should go after wastewater accounts.

the ANALYST Volume 30 Number 4

The third edition of AWT’s TR&TM is now available for purchase! It has been reviewed and updated to include current technology and recent developments, with an all-new chapter covering even more water treatment topics. Stay up to date on: • • • • • • • •

General Water Treatment Concepts Pretreatment Boiler Water Cooling Water Regulations Wastewater Potable Water And Other Water Treatment Applications

To order your copy, visit the AWT Bookstore at www.awt.org/awt-bookstore. For more information, contact Angela Pike at apike@awt.org or (240) 404-6477.

CWT Spotlight

Nathaniel L. Woodrum Jaytech Water Solutions St. Louis, MO

What prompted you to obtain your CWT and when did you begin the process of taking the exam?

the example math problems. I also took as many online AWT quizzes as I could, usually at the pace of one a week. Again, this is a process. Invest time daily over the course of months and you’ll be amazed how much you learn.

When I came to work at my current employer, an AWT member, our training cycle relied heavily on AWT papers and AWT’s Technical Reference and Training Manual. As I dug deeper, I began to realize how much I did not know, even with years of experience already under my belt. As a person who takes pride in my profession, I decided to become an expert by mastering the AWT Technical Reference and Training Manual and passing the CWT exam.

What was the most difficult aspect of the exam?

The setting itself was difficult, as was the timing. There are five sections to the test, and each must be passed individually to pass the exam as a whole. You may find one section or the other the more difficult.

Why do you feel this credential was important to have?

Would you employ a lawyer who did not pass the bar exam? How about a carpenter who didn’t know how to use a level and hammer? Put simply, every profession has a trade group or accrediting body. AWT is ours, and there’s no reason not to tap into that resource. A lot of AWT companies are smaller than our corporate competitors and this provides us a way of proving to customers that we know as much or more than the larger competitors. It shows the customer that you are a subject matter expert in your field, a true professional. How did you prepare for the exam?

Even though I had a full work schedule in the field, I prepared by reading the manual daily for about 30-60 minutes before hitting the road for work. I would tackle several sections each morning with a cup of coffee and an open mind. I read through the entire manual in that fashion, not once but twice. Reading the manual and then re-reading it gives you more insight the second time through. I then went back and worked through 61

Regarding the setting, I had to report to a professional testing facility where the proctor identifies you, then you empty your pockets into a locker, then you walk into a secure computer lab where the test is administered. No notes or calculator are allowed, but you’re provided with a white board for figuring math. I have a poor memory, so memorizing the cooling tower and boiler formulas was difficult for me. I also took the test during the summer of 2020 (remember COVID-19?) so the pandemic itself was another barrier, but that should be resolved by now. What advice would you give those thinking about taking the exam?

Earning your CWT is a marathon, not a sprint! I would encourage everyone working in an AWT-member company to study the Technical Reference and Training Manual as if you were going to take the test. Obviously, your educational background will affect your perception of the material’s difficulty, however with proper time and commitment anyone can pass the test.

the ANALYST Volume 30 Number 4

Tales From the Waterside

How Could a Bug Eat a Hole in my Admiralty Tubes? Loraine A. Huchler, P. E., CMC®, FIMC

customer some questions (my questions in italic):

One December, a business manager at a chiller manufacturer asked me why all three new chillers in a district heating and cooling plant failed six weeks after commissioning. The manager described the scope of their standard warranty and the risk of significant financial and reputation issues.

“Who was the manufacturer of those chillers?” “Broad,” they answered. “What is Broad?” I asked.

The eddy current inspection showed several perforations and numerous locations with significant wall loss in the admiralty (90:10 copper:nickel) tubes. On a phone call with my client’s local staff, the sales manager said, “Are you telling me that a bug ate a hole in my admiralty tubes?”

“A Chinese company.” “Why is this chiller open?” “Motor problems.”

“Yes,” I answered – “perfect translation.”

“When were they installed?”

Failure Inspection

“Several years ago.”

The following week, I was on my way to Europe to conduct a site visit. Within an hour of landing, I was interviewing the local sales team that had sold the chillers. Then off to see their customer; the plant manager was very angry and my client was trying to manage the situation.

“What is the material of construction for the tubes?” “Copper.” Why didn’t the Broad chillers fail shortly after commissioning? Copper has a lower resistance to corrosion than admiralty. I said to myself, “Think fast; these people are angry.”

I looked at the inlet tube sheets and the entrances of the tubes in my client’s chillers. Smooth bore tubes and a heavy layer of silt on all surfaces. It was impossible to determine the condition of the tube surfaces.

Back to the conference room, I had still more questions:

The plant had another set of chillers that they called the “Broad units.” I looked at the inlet tube sheets and smooth-bore tubes in the Broad units; their diameter was at least 25% larger than the tubes in my client’s chillers. The tube surfaces had some discoloration, but the dark-colored surfaces were mostly clean and smooth. The source of the make-up water to the condensers was a river that eventually empties into the North Sea. As we walked back to the conference room, I started asking the 62

“Did you require the Chinese company to conduct a factory performance test on each chiller?” “Yes, of course.” “What about my client’s chillers – did you require any factory performance tests?” “OF COURSE NOT – these are American chillers!” the ANALYST Volume 30 Number 4

Tales From the Waterside continued

I had not expected the plant manager to shout; I realized that I had just asked a dumb question. Unlike Chinese products, there was no need to question the quality of American products.

Failure Analysis

metabolites from SRB interfered with the passivation process (sulfide-related corrosion) (Figure 1). These bacteria caused localized corrosion (MIC) (proliferation of bacteria on the tube surfaces, beneath the loosely adherent copper oxide layer) (Figure 2).

Root Cause Conclusion

I had a working theory – but it was just speculation until I could get more data. My client’s local sales team arranged to send portions of the damaged tubes and a sample of water from one of my client’s chillers to a laboratory. The metallurgical analysis showed two mechanisms of corrosion: microbiologically induced corrosion (MIC) (localized corrosion), and sulfide-related corrosion (generalized corrosion). How did that happen? The map showed that the location of this plant is at the boundary of a river and a harbor on the North Sea. It was clear that the water quality at the intake structure would be a mixture of fresh and seawater according to the tidal flow. In other words, this plant was using brackish water from an estuary. Water experts know that brackish water supports a variety of bacteria, including sulfate-reducing bacteria (SRB) that are common in fjords.

Based on the results of the metallurgical and water analyses, I concluded that the failure of the admiralty tubes was caused by commissioning these units using water from the estuary without conducting a factory performance test or an in-situ passivation procedure. The plant manager continued to assert that my client was responsible for this failure – he was sure that there was a design issue: the selection of a material of construction that was not compatible with the water quality. During a failure investigation, it’s common for the owner to question the consultant’s conclusions about the root cause of failure, especially failures that are not covered by a warranty. I began to methodically review all of the possible contributing factors.

Possible Contributing Factors

It was no surprise that the laboratory results for the water analysis showed high populations of bacteria and sulfides. Investigators identified both acid-producing bacteria (APB) and iron-oxidizing bacteria (IOB) on the tube surfaces. Naturally occurring sulfides and

Corrosion Patterns. I started with the pattern of the localized corrosion sites (pits). The preponderance of pits at the inlet of the tubes is likely to be an artifact of the flow pattern as the water travels from the inlet plenum into the tubes. From a hydraulic perspective, the best model for a tube sheet is a square-edged inlet. Figure 3 shows that the hydraulic effect of “turning the corner” results in secondary flow patterns for a short length at the inlet. At some unknown location

Figure 1: Generalized corrosion by sulfides.

Figure 2: Localized corrosion by MIC.

the ANALYST Volume 30 Number 4

Tales From the Waterside continued

farther downstream, the velocity distribution returns to the normal pattern. These areas of secondary flow may provide a more favorable environment for bacteria to adhere to the tube surface and could account for the preponderance of pits on the tube surfaces near the inlet. Figure 3: Effect of a sharp-edged Inlet on flow patterns.

a maximum linear flow rate to prevent the fluid from causing erosion-corrosion. Copper alloys can tolerate a higher flow rate without being vulnerable to erosion corrosion; however, designers generally use the same guidelines for all copper and copper alloys in smoothbore tubular heat exchangers. The linear flow rates were well within the range for turbulent flow and there is no risk of erosion-corrosion. Water temperatures. The cooling water temperature is 24oC (75oF) at the entrance to the tube bundle and increases by approximately 13.3oC (8oF) at the exit of the tube bundle. Heat exchanger designers characterize this heat transfer rate as “low duty” due to the low inlet temperatures and small temperature differentials across each heat exchanger. The thermal design for these heat exchangers is consistent for systems that use oncethrough untreated cooling water. Materials of construction. The alloy for the tubes conforms to the specification for UNS C70600. The other construction materials in the system include a non-corrosive material, fiberglass, for most of the transfer piping and coated carbon steel tube sheets and heads for the chillers. I could not identify any other compatibility issues for these materials of construction.

This phenomenon is not a design issue because all shell-and-tube heat exchangers, including these chillers, operate with this type of hydraulic pattern. Our investigation ruled out linear velocity and erosioncorrosion as root causes because the flow rates were within an acceptable range for turbulent flow and the velocity is not high enough to cause erosion of base metal, even for un-passivated surfaces. However, every un-passivated tube will be vulnerable to generalized corrosion from trace concentrations of sulfides in the estuary water. These locations of generalized corrosion will not be the first location to fail because localized corrosion (e. g., MIC) results in a much faster corrosion reaction.

Materials handling and fabrication procedures. Discussions with my client’s engineering and manufacturing staff provided information about material handling and fabrication procedures, especially practices that would compromise the cleanliness of the tube surfaces, creating a risk of localized corrosion. I determined that the tube rolling procedure that uses a special expander tool does not use any oils or grease. I could not identify any procedures that would compromise the cleanliness of the tube surfaces or damage the tube at the boundary of the tube sheet.

De-alloying. An analysis of a sample of scale formed by generalized corrosion showed no unusual concentrations of elements on the surface and there was no evidence of the corrosion mechanism of de-alloying (e. g., selective corrosion of nickel) on the underside of the deposit.

Installation and commissioning. Discussions with my client’s local staff about the installation and commissioning procedures indicated that one unit has a co-current configuration for the heat exchanger, resulting in a higher temperature differential across the heat transfer surface at the inlet, and a higher corrosion rate than the other two heat exchangers that have a counter-current flow configuration. However, all three chillers had evidence of localized corrosion.

Flow rates. The commonly accepted range of linear flow rates for turbulent flow inside smooth-bore copper tubes is 0.9 to 3.6 meters per second (m/s) (3 to 12 feet per second [ft/s]). Designers specify a minimum linear velocity to ensure a fully developed turbulent flow to optimize the heat transfer efficiency and specify 64

the ANALYST Volume 30 Number 4

Tales From the Waterside continued

Corrective Actions

Under the threat of a lawsuit, my client agreed to replace all tubes that had a wall loss of 40% or more and conduct an in-situ passivation. The local sales team installed a pump, a sump, and a heater to recirculate potable water mixed with sodium borate to adjust the pH. Ideally, I would have recommended the use of additional chemicals to accelerate the passivation process; however, these other chemicals are not permitted to be discharged to the estuary after completing the passivation process. Figure 4 shows the passive oxide layer that formed on tube samples suspended in the sump after seven weeks of circulation. Figure 4: Admiralty tube samples after seven weeks of passivation.

corrosion in my client’s chillers. Consequently, the plant manager withdrew the lawsuit. Now, ten years later, there have been no tube failures – that’s the power of proper passivation! Loraine Huchler is the founder and president of MarTech Systems, Inc., a firm that assesses and manages risk in water-related utility systems. Her work includes optimizing the performance of the water treatment service provider and the assets in water circuits in hot water/steam and chilled/condenser water in large-scale corporate and university campuses and manufacturing facilities. She also provides technology feasibility studies, water conservation and water reuse studies, technical training and serving as an expert witness in patent infringement and equipment failure litigation. Ms. Huchler has a B.S. in chemical engineering from the University of Rochester (New York) and is licensed as a Professional Engineer and has earned the accreditation of Certified Management Consultant®. Ms. Huchler can be contacted at huchler@martechsystems.com.

Keywords: CHILLER, COOLING TOWERS, COPPER, CORROSION, MATERIALS OF CONSTRUCTION, PASSIVATION, TUBES

The local sales team was working against a deadline to have these refurbished chillers ready for the cooling season; they wanted to know how long the passivation process should last. The duration of the factory performance test of the Broad chillers would have been less than 24 hours of operation under controlled conditions (conventional water treatment and normal operating temperatures). It’s likely that the factory performance test of the Broad chillers created a passive copper oxide layer that was strong enough to prevent corrosion from the sulfides and bacteria for several years. I recommended a conservative passivation period of seven weeks to establish a protective oxide layer. Six months later, I was back at the plant, tutoring an expert witness in preparation for the trial. At the end of the first cooling season, the eddy current test showed no 65

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T.U.T.O.R. Technical Updates, Tips, or Reviews

Part 2: Lessons Learned about the Attack of Cooling Water Microbials Brad Buecker, Bueker and Associates

In a previous Analyst article (1), we examined several important steam generation chemistry lessons-learned that are often overlooked, or where knowledge has not been adequately transferred to new employees. The same is frequently true for cooling systems. Large plants may have numerous cooling towers, many of which sit in out-ofthe-way places and escape attention. This article outlines several examples of how cooling system performance can quickly degrade due to microbiological fouling, and it provides an overview of modern control techniques to minimize fouling.

Microbes—Ignore at Your Peril

A new water treatment manual from ChemTreat (2) makes the following observation about microbial fouling: “Cooling water systems provide an ideal environment, warm and wet, for microbiological growth. Bacteria can form colonies in many locations, fungi will attack cooling tower wood, and algae will proliferate in sunlit areas, particularly on tower decks and other exposed areas. More advanced microorganisms such as amoeba and protozoa often multiply in established microbial colonies. Figure 1: A heat exchanger fouled by slimeforming bacteria. Source: Reference 2.

These more complex organisms can enhance growth of Legionella bacteria.” Figures 1-3 offer dramatic examples of excessive microbiological fouling. Microbes that enter a cooling system via the makeup water or from the surrounding atmosphere initially exist as free-floating (planktonic) organisms. In this state, unless pathogenic organisms are present, the microbes are relatively harmless. However, if the organisms are allowed to settle, they will establish colonies that cause the fouling shown in the figures above. Not only do the organisms and accompanying slime/silt mass degrade heat transfer, but they can also induce under-deposit corrosion and microbiologically influenced corrosion (MIC) that may lead to rapid metal failures and unit shutdowns (Figure 4).

Lessons Learned

Lesson #1 A power plant unit was taken off line for a monthlong scheduled outage. The operators did not drain the waterside of the steam surface condenser, which contained more than 15,000, 316 stainless steel tubes. Upon startup,

Figure 2: Fouled cooling tower fill. Source: Reference 2.

Figure 3: Extreme algae formation on the side of a cooling tower. Source: Reference 2.

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T.U.T.O.R. continued

plant chemists detected serious raw water contamination of the condensate that required an immediate unit shutdown. Inspection revealed thousands of pitting failures, which metallurgical analyses confirmed as MIC. A complete condenser re-tubing was required. Microbiological control methods. For most cooling systems, oxidizing biocides are the backbone of the microbial control program, as chemistry usually represents the most cost-effective method for maintaining system cleanliness. It is important to properly size each chemical feed system so it can provide the desired oxidizer concentration during all conditions. Obviously, microbes are most active at warmer temperatures, so the system should be large enough to provide sufficient chemical feed in summer, with the ability to reduce feed as temperatures cool in the autumn. Sometimes, oxidizer feed is suspended during winter for cooling systems located in northern climates, which leads to the next case history.

that had Admiralty brass tubes. Copper is a natural biocide to many microorganisms.

Lesson #3 To restore heat transfer in the non-Admiralty condenser from the above lesson learned, plant personnel took the unit down to 50% load one night and then shock chlorinated the condenser tubes, one half at a time. Subsequent visual inspection and sampling confirmed that the bacteria had been killed but the slime layer was so tenacious that the condenser cleanliness factor only recovered by about 50%. At the earliest available opportunity, plant management hired a firm to clean the condenser with tube scrapers.

A General Lesson Learned

Lesson #2 Plant personnel would regularly shut down the biocide feed (to three once-through steam surface condensers) through December-February at this midwestern power plant. One year, when they attempted to start the system as spring began to arrive, the staff discovered that maintenance was needed to make the system operational. This gave bacteria a three-week window to form colonies in the condensers and establish a protective slime layer. Condenser performance dropped significantly, although fouling was less pronounced in two of the condensers

The above three lessons learned were a result of issues illustrated in Figure 1. Microbiological fouling and solids accumulation can also plague cooling tower fill as shown in Figure 2. Fill fouling reduces water flow and heat transfer. But the situation may become even worse. Figure 5 (4) illustrates both the loss in tower efficiency and the weight gain that results from fouling and deposit accumulation. Figure 5: Tower capability loss versus fill weight gain for a standard offset flute cellular plastic fill pack. Source: Reference 4.

Figure 4: Through-wall penetration caused by MIC. Source: Reference 3.

While the primary purpose of this graph is to show the loss of tower efficiency as a function of solids accumulation in the fill, it also reveals that the weight density can become quite high. Incidents are well known of partial cooling tower collapse because of fill fouling. The costs for lost production and equipment replacement can be staggering.

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T.U.T.O.R. continued

Fouling Control Methods

Hypochlorite (OCl-) is a much weaker biocide than HOCl, probably because the charged OCl- ion does not effectively penetrate cell walls. The dissociation of hypochlorous acid dramatically increases in relation to rising pH (Figure 6).

These lessons illustrate the importance of establishing a regular inspection program for chemical feed systems, with procedures in place for expedited repairs if a system malfunctions. This typically requires stocking the necessary replacement parts, and perhaps even a spare pump for each system, in the storeroom. Another important issue is the choice of oxidizing biocide, which in large measure stems from long ago lessons learned.

Figure 6: HOCl dissociation as a function of pH. Source: Reference 2.

Chlorine gas was the workhorse for drinking water and then cooling water treatment for many years. The reaction with water is shown below in Equation 1:

Cl2 + H2O ⇌ HOCl + HCl Eq. 1 Hypochlorous acid (HOCl) is the killing agent, and it functions by damaging cell walls and oxidizing cell components. Due to safety issues with gaseous chlorine, many industrial facilities switched to liquid sodium hypochlorite (NaOCl, aka bleach), with a common active chlorine concentration of 12.5%. Lessons learned from this changeover include:

HOCl is 80% undissociated at a pH of 7 but is almost 80% dissociated at a pH of 8. Also, ammonia and organics in the water will consume chlorine, leaving it unavailable to attack microbes. This influence is known as chlorine demand.

Prepare precise specifications for the product. Impurities such as iron can catalyze decomposition. Store the bleach in an insulated tank, preferably with a white coating, and protected by a roofed open structure to shield the tank from direct sunlight. Heat will degrade the compound.

So, for cooling waters with an alkaline pH, alternate programs may be more efficient. A popular alternative has been bromine chemistry, where a chlorine oxidizer (bleach is the common choice) and sodium bromide (NaBr) are blended in a slipstream and injected into the cooling water. The reaction produces hypobromous acid (HOBr, Equation 3).

Chlorine treatment was quite effective when combined with the acid/chromate scale-corrosion control programs of the last century, in which pH was typically maintained within a range of 6.5 to 7.0. However, chromate treatment was abandoned per the recognition of health hazards from hexavalent chromium (Cr6+). The common replacement programs have relied on inorganic and organic phosphates, with a typical operating pH near 8.0 or slightly higher. (Reference 2 provides additional details regarding this chemistry, and evolving non-phosphorus programs that are better for the environment.) The efficacy and killing power of chlorine are greatly influenced by pH, per the equilibrium nature of HOCl in water (Equation 2). HOCl ⇌ H+ + OCl-

HOCl + NaBr ⇌ HOBr + NaCl

HOBr has similar killing powers to HOCl, but functions more effectively at alkaline pH. Figure 7 compares the dissociation of HOCl and HOBr as a function of pH.

Eq. 2

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Eq. 3

T.U.T.O.R. continued

Chlorine dioxide must be prepared on site via the reaction of either sodium chlorite (NaClO2) or sodium chlorate (NaClO3) with an additional oxidizing agent under acidic conditions. ClO2 is more expensive than halogens, but modern production techniques have lowered the cost.

Figure 7: Comparison of HOCl and HOBr dissociation versus pH. Source: Reference 2.

Chloramines Chloramines have served for microbial control in potable water systems for many years. For industrial cooling water, monochloramine (NH 2Cl) is the compound of interest. Technologies are now available to produce a pristine stream of NH 2Cl for this purpose. When compared with sodium hypochlorite, monochloramine is less reactive but almost equally toxic. The reduced reactivity allows it to penetrate biofilms and attack underlying organisms. However, monochloramine generally needs a longer contact time than hypochlorite to achieve the desired microbial destruction.

Note the high concentration of un-dissociated HOBr at pH of 8. Unlike chlorine, which reacts irreversibly with ammonia, the bromine-ammonia reaction is reversible, and leaves that portion of the bromine free for activity towards microbes. Of note though is that concern continues over the reaction of chlorine and bromine with water to form halogenated organic compounds. Environmental regulators may consider these side reactions when reviewing discharge permits. A number of alternatives are available to or can supplement chlorine and bromine. A brief review of some of the most common is provided in the following sections.

Halogen Stabilizers Several chemical compounds are available that can stabilize chlorine and bromine and then release the oxidizers gradually, and where they are most needed. Three classes of stabilizers dominate the market: sulfamate, dimethylhydantoin, and isocyanurates.

Nonoxidizing Biocides While oxidizing chemicals normally serve as the foundation of cooling water biocide programs, microorganisms can develop partial immunity to the compounds. Accordingly, in some applications, feeding of a non-oxidizing biocide on a periodic basis (e.g., once or twice per week for an hour or so) can help to control microbial growth. The non-oxidizers typically penetrate cell walls to then react with compounds within the cell that are integral for metabolic processes. Common compounds include: Bronopol 2,2-dibromo-3-nitrilopropionamide (DBNPA) Glutaraldehyde Isothiazolines Quaternary amines

Chlorine Dioxide Chlorine dioxide (ClO2) is powerful oxidant that exists as a gas at ambient temperature. It is soluble in water to a maximum concentration of approximately 3,000 milligrams per liter (mg/L). Chlorine dioxide exhibits a high degree of reaction selectivity, and it can penetrate biofilms to attack microbes. The selectivity is advantageous for other water treatment applications, including wastewater phenol destruction and odor control.

These compounds often show enhanced selectivity towards some organisms and reduced selectivity towards others. Careful evaluation may be needed to choose the correct product or product blends. As with any chemical, care is needed in storing and handling these compounds. Strict adherence to safety data sheet (SDS) information is critical.

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T.U.T.O.R. continued

Sustainability Lessons Learned

The next example is to some extent a continuation of the lessons learned above. Increasingly, either by choice or mandate plants are switching from fresh water makeup sources to reclaim supplies such as effluent from municipal wastewater treatment plants, also known as publicly owned treatment works (POTW). We covered a number of issues regarding POTW use in an earlier Analyst article (5), but an issue that bears further discussion is that selection of alternative makeup supplies requires careful planning, as the next lesson learned illustrates.

Lesson #4 This example came from a power plant project during the design phase in which the cooling tower makeup would be a secondary-treated publicly owned treatment works (POTW) effluent. This water contained much higher concentrations of ammonia, nitrite/nitrate, phosphorus, and organics than surface water supplies in the area. For makeup pretreatment, the design team originally specified just basic clarification to remove suspended solids, as costs for additional pretreatment were considered too large. But when the design specifications were issued to a major cooling tower manufacturer for their estimate, back came the reply that without additional makeup water pretreatment the cooling tower would have to be much larger than normal, with low-fouling fill to handle the poor-quality makeup water. Investigation revealed a significantly less expensive alternative—installing a moving bed bioreactor (MBBR) at the plant to convert the secondary-treated water to tertiary quality. Some reputable vendors offer this and similar equipment on a build-own-operate-method (BOOM), where for a monthly fee they will handle system operation and maintenance. This arrangement removes the burden of operation and troubleshooting from plant personnel.

At my first power plant, I had been performing thriceweekly cleanliness factor (CF) analyses on several steam condensers, including the largest, rated at 1,000,000 pounds per hour (lb/hr) maximum steam flow. The CF values remained very steady for several months before suddenly dropping by almost 50% in one day. Even waterside microbiological fouling does not occur this rapidly. Such drastic changes are more indicative of excess air in-leakage. Maintenance personnel were notified, and upon inspecting the condenser they discovered a crack in the condenser shell where a feedwater heater drips line penetrated. The large volume of air that then entered the condenser steam-side overloaded the air removal vacuum pumps and allowed air to begin blanketing the condenser tubes. Once the maintenance staff sealed the crack, the cleanliness factors returned to previous values and remained at that level for another two months until suddenly dropping again. The seal had failed. The maintenance crew then welded a collar around the drips line, which totally sealed the crack and cured the problem. This is an example of how someone new to the industry might have chased a fouling or scaling issue when in fact the problem occurred on the steam-side.

Conclusion

This article outlined several important lessons learned that will hopefully be of value to readers. Two key takeaways are the need to have cooling water treatment systems in place and fully functioning for however long the microbiological season lasts, and to regularly monitor cooling system conditions to catch problems before they become too severe.

References 1. Buecker, B. (Summer 2023). “Lessons Learned from the Power and Industrial Steam Generation Industries,” the Analyst 30(3), pp. 72-79. 2. Buecker, B., Tech, Ed., (2023). “Water Essentials” ChemTreat, Inc., 2023. (This industrial water handbook is currently being released digitally on a chapter-by-chapter basis.) Information is available at www.chemtreat.com. 3. Post, R.; Buecker, B.; Shulder, S. ( June 6-8, 2017). “Power Plant Cooling Water Fundamentals,” pre-conference seminar conducted at the 37th Annual Electric Utility Chemistry Workshop, Champaign, Illinois.

A Hidden Menace

Efficiency loss in heat exchangers is typically due either to microbiological fouling or scale formation. But sometimes overlooked is an issue that can plague power plant steam surface condensers. I offer the following as Lesson Learned #5.

4. Monjoie, M.; Russell, N.; Mirsky, G. (1993). “Research of Fouling Film Fill,” Cooling Technology Institute, TP93-06, New Orleans, Louisiana. 5. Buecker, B.; Post, R. (Fall 2019). “Is Greywater a Sustainable Alternative for Cooling Tower Makeup?” the Analyst Fall Supplement 26(4), pp. 10-22.

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T.U.T.O.R. continued

Brad Buecker is president of Buecker & Associates, LLC, consulting and technical writing/marketing. Most recently he served as senior technical publicist with ChemTreat, Inc. He has more than four decades of experience in or supporting the power industry, much of it in steam generation chemistry, water treatment, air quality control, and results engineering positions at two coal-fired power plants. His work also included 11 years with two engineering firms, Burns & McDonnell and Kiewit, and he also spent two years as acting water/wastewater supervisor at a chemical plant. Mr. Buecker has a B.S. in chemistry from Iowa State University with additional course work in fluid mechanics, energy and

materials balances, and advanced inorganic chemistry. He has authored or co-authored more than 250 articles for various technical trade magazines, including the Analyst, Industrial Water Treatment, and Ultrapure Water Journal. Mr. Buecker has also written three books on power plant chemistry and air pollution control. He is a member of the ACS, AIChE, AIST, ASME, AWT, NACE (now AMPP), and the Electric Utility Chemistry Workshop planning committee. He may be reached at beakertoo@aol.com. Keywords: BIOCIDES, COOLING TOWERS, CORROSION, ENVIRONMENTAL, MONITORING

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the ANALYST Volume 30 Number 4

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In In Memoriam Memoriam

Honoring our deceased water treatment colleagues.

Robert J. Ferguson 1949–2023

Rob Ferguson, co-founder of French Creek Software, passed away in August. He and his wife, Janet, co-founded the business in 1989, which he was president of for 34 years. The company became known for its predictive software tools. He began his water treatment career with Nalco in 1974 and continued with positions at Chemlink and Calgon before starting French Creek. His son, Baron, noted that his father had a desire to simplify water chemistry to make it more accessible to the everyday person. Rob was named the Ray Baum Water Technologist of the year in 2017, and later in 2020 he was honored as the first AWT Innovation Award honoree. Many recall his larger-than-life presence at AWT conventions over the years. French Creek Software remains active in the water treatment market and will continue licensing and supporting its global user base, the family said.

Marvin Rex Rankin, III 1952–2023

Rex Rankin passed away peacefully in his home in July. He started his own insurance company after working at his father’s insurance company for many years, and he was successful, taking risks that no other insurance company was willing to take. Rex was also responsible for starting a water treatment company that supplied the Turks and Caicos Islands with clean running water, known as Water Colors Water Treatment. Rex was an avid supporter of AWT, who contributed both financially (memorably, the 2010 anniversary in Reno, NV) and personally (his efforts to bring lower insurance premiums to water treatment businesses who have CWTs in their employ have been realized). He is fondly remembered by many for his vibrant personality, golf course conversations, and making sure everyone was having a good time at conventions.

John Brady Benson, Jr.

Earl E. Martens

1963–2023

1943–2023

Brady Benson, founder of AquaMedix, passed away in June. He is survived by his wife, Michelle, three children, and two brothers. For 12 years, he lovingly built the AquaMedix company and was an active participant in AWT, in particular as part of the Special Projects Subcommittee. Brady is remembered as an “extremely nice man” who loved being outdoors for fishing trips on Minnesota’s beautiful lakes.

Earl Martens passed away in his home surrounded by family. He is survived by his wife of 49 years, Mary, their two children, and one grandson. Earl started Moorefield Group in 1996, a water treatment business. He had many customers and dear friends across the Midwest, and one of the highlights of his career was serving on the AWT Board of Directors. He believed in the nobility of craftsmanship and took pride in a job well done, no matter how small.

the ANALYST Volume 30 Number 4

What’s (Water) on Your Mind?

Back in the day, what was it like to wear ties in the field to practice industrial water treatment? Compiled by James McDonald, Chem-Aqua Note: The following discussions come from the Industrial Water Treatment interest group on LinkedIn.

Question of the Week

changed. Folks were getting less formal and hipper, not like the stodgy boomers. I would still wear a tie in client meetings through the late 90s, but then in the early 2000s I recall the meeting that ended it for me. I was at a DuPont site, not that it matters it was Dupont, but I thought, “I better be wearing a tie because it is DuPont, and this shows some respect.”

Back in the day, what was it like to wear ties in the field to practice industrial water treatment? Dorian: I’m a second-gen water treater. My dad, John Willis, was a single parent. He used to take me to his customers. I could run basic water tests at 10 years old. He had to wear a tie. He ruined a lot of them. I’m glad we are out of that stage just due to safety. Des: Not many of us are left from that era. Dress code and etiquette were hand in glove (no pun intended). We were all in a steep learning curve, both client and we engineers. I made some lasting friendships. Keith: For safety reasons I’m happy that it is not standard anymore. A nice suit looks a bit funny with safety shoes on. Also, when I’m approached by someone in a suit in a water treatment situation, they may have years of experience; however, the fact that we wear so many hats (sales, service, marketing, customer service) the suit to me says that you aren’t the one actually doing the work. Charles: We did that when I started with Nalco. Eventually, customers said to stop. It was always unsafe around rotating equipment.

Well, the meeting starts, and the rep said something along the lines of, “Thanks for coming. We appreciated your attendance, but before we got started (which I figured for darn sure would be a safety moment...but NO), they turned and pointed at me and said, “You need to lose the tie.” I was the only one sitting there with this stupid tie on, and I ripped that off and never looked back. It was a wake-up call that things had changed. Carol: I remember those days. I had a customer who told me, “If you are not dirty, I don’t see you giving me technical services.” Stephen: I stopped wearing ties after I heard a story about a tie getting caught in a pump shaft. Alberto: A water treatment specialist may or may not talk to the CEO, but they will always take a look at the equipment on the roof and in the basement to get an idea of what is going on. So, in our work, wearing a tie is not appropriate since we always include visits to dynamic (moving and potentially dangerous) equipment.

Robert: I used to wear a tie in the office through most of the early 90s. It was considered appropriate dress code for process, mechanical, electrical engineering groups. We had the occasional Friday where we would lose the tie but not to the casual level of your Hawaiian doublefisted umbrella drink Fridays, James. LOL (I add some exaggeration of course to make a point.)

Jon: Remember it well. Clip-ons (ties) were needed so that if equipment caught it, you weren’t pulled in. Chris: I wore a tie and nice clothes into the steel mill, changed into a jump suit for the day, then put my nice

Then the internet happened, and it seemed things 74

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What's (Water) on Your Mind? continued

clothes on at the end of the day. In the paper mill, I wore the tie all day through 1992.

and services. Dressing the part is a simple way to distinguish a water treater from a drum kicker.

Paul: I liked to wear a three-piece suit (vest) in the 80s.

Stephen: I wore one in Darwin, the NT and was told to remove it before someone cut it off. A lot of big knives up there!

Lauren: My last job required ties and a jacket (except Fridays and in the summer from Memorial Day to Labor Day) up until like 2018. Women were required to wear pantyhose to cover any bare skin exposed with dress shoes. When clients would visit our campus, we often warned them to wear their nicer matching FRC or golfing clothes. Mitchell: Working for Nalco in the 80s, you had to wear a suit. They gave you coveralls so you could inspect the boiler in your suit. The most important thing to remember was to either wear a breakaway tie or tuck it into your shirt so you don’t die leaning over a pump shaft. Mark: I remember my first manager telling me to always have a suit in the car to put on for important review meetings. “You never know if someone senior will be there, and you wouldn’t want to look underdressed,” he said. But I stopped wearing them shortly after that time because the times changed and one looked overdressed for a review meeting, especially in the summer. Sampath: It’s better to wear formal pants and a formal shirt with collar will be good to wear for meetings and even water testing on sites as our days can sometimes be unpredictable. We may be required to visit sites or go to important meetings. It is also important to always have safety shoes available.

Paul: We had the 100-degree rule here in Arizona. No ties until cooled back down. Amy: I appreciated this post as well as the couple of women who commented on their experiences! Happy to see a different dress code and more of a female presence in the industry these days, too. Dick: It was part of the Dearborn “Uniform”. The intent was a professional first impression. I removed my college ring in my first week after transferring from the laboratory to sales. That ring has been in a drawer since 1975. Mike: Hats were out by the time I got into the business, but the professional look still carried a great deal of weight, until you got in the plant and then it was coat off, tie loosened, and sleeves rolled up!

Question of the Week

When can literally leaving fingerprints cause issues in industrial water treatment? Catherine: Colorimeter cells with fingerprints on them give inaccurate results. Dipslides with fingerprints grow the bugs on your hands.

Paul: Professors wear business casual now. I used to wear a sport coat, shirt, and tie when I taught chemistry at Indiana University in the 70s. I later wore business casual clothes for R&D work at Nalco, Olin Water Services, Petrolite, and Grace Dearborn between 1973 and 1996. I wore very casual clothes when I worked as a consultant from home between 1996 and 2008 before returning to college students where I teach the young and the restless future nurses, engineers, and medical doctors. My colleagues and I make them work hard before they earn the big bucks :). Rob: I wore a tie into the boiler room today. Our industry seems to have forgotten that we are serious, scientific professionals, offering professional consultation 75

Luke: Definitely corrosion coupons. Tony: On testing vials. Thabiso: When doing analysis sampling. Brian: When there’s a case that Detective H 2O needs to solve! Henry: Pushing the wrong override button, plus all answers already said. Chris: Don’t touch your bug slides. Mike: Dissolved oxygen data logging (probe membrane). the ANALYST Volume 30 Number 4

What's (Water) on Your Mind? continued

David: TOC analysis sampling.

James2: I thought we’d get more answers to this one. There are arguments to be made for both locations.

Michael: Corrosion coupons.

Garrett: Can you expand on the arguments for both locations? Or if you prefer, send me a private message to discuss further. Thanks!

Dave: UV bulbs.

Question of the Week

Is the best place to feed makeup water to a steam boiler system to the deaerator or to the surge tank ahead of the deaerator (that mixes condensate and makeup water)? What are the pros and cons of each location?

James2: Garrett, a strong argument for feeding makeup to the deaerator is the corrosion that can occur in the surge tank system due to the oxygen in the cooler makeup water becoming less soluble at higher temps. More corrosion-resistant metallurgy can help. An argument I have heard for feeding to the surge tank is load balancing of condensate return vs makeup demand.

Chris: If you put the makeup water into the surge tank, then your metallurgy should be stainless from the surge tank to the DA. Oxygen in hot water is very corrosive. John: No argument! Makeup water must not go to the condensate tank! Oxygen in the makeup will cause corrosion in the condensate tank and piping leading to the deaerator. The increased iron in the feedwater causes porous deposits on high heat transfer surfaces that promote caustic accumulation and gouging damage. Do not try to feed chemical oxygen scavenger to the condensate tank as pH will drop and conductivity will rise. Let the mechanical deaerator do what it is designed to do! James1: It depends. Vinod: Water becomes reddish in blowdown of a boiler. Geopure: Place @deaerator.

Mohamedreza: I created a flow diagram for 12 large refineries, each with a steam production of around 500 tons per hour. The design involves entering makeup water directly into the deaerator. Direct to Storage Tank: Advantages: Better level control in deaerators. Lower temperature in storage tanks, reducing the required class of construction materials. Prevents the escape of volatile compounds from returning condensates due to temperature and N2 blanket failure (which happens frequently due to lack of N2). Allows storage tanks to be used as balancers in addition to their main storage function.

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What's (Water) on Your Mind? continued

Question of the Week

Disadvantages: •

How do you decide it is time to replace a reverse osmosis (RO) membrane?

Corrosion due to higher dissolved oxygen (DO) in makeup (MU).

Qassim: By KPIs and clean in place (CIP) results.

•

Lowering the temperature in storage tanks increases the amount of nitrogen required for blanketing.

•

When a heavy tube, CPP, or ACF failure occurs, storage tanks can separate oil in the upper level and the operator can overflow the tank and remove HCs by simple gravity separation. When we direct MU to the deaerator, return condensate will have higher space-time (residence time) in storage tanks and HC separation will be enhanced.

Abilash: If the old membrane’s normalized performance cannot be recovered by extensive CIP procedure.

Question of the Week

What keeps you up at night in the world of industrial water treatment?

Musyafa: And if the salt rejection is already at the lowest level. Abilash: True. That’s part of normalized membrane performance parameters. Sarah: When its effectiveness deteriorates after 2 to 5 years. Vijayakumar: Check the log sheet performance of RO membrane past 3 months: Pressure drop in RO inlet and outlet Permeate TDS Reject pressure increased? Pumping pressure increased? CIP no longer makes any difference

John: Customers who will not follow written instructions and then blame their water treatment supplier for poor results. Also, water treatment company representatives that do not clearly document their recommendations!

Narayanan: If salt passage is higher than our requirements in permeate and/ or the permeate flow is lesser than our design value even after cleaning of RO membrane.

Dorian: Did I shut that valve? Did I program that bleed valve right?

Fernando: If after a cleaning procedure, the performance in DP, Flow Rate, and Salt Rejection does not change, it´s an indicator of replacement.

Mike: Did I get the right dosing duration for the foaming biocide that’s being dosed during the night? (Of course, the pro checks it during the day and has defoamer on hand.)

Chris: Remember to normalize your data!!!

Brent: Truck deliveries, usually.

Question of the Week

Rabeya: According to me, the following few points can keep a chemist up at night in the world of industrial water treatment: Environmental Impact, Regulatory Compliance, Emerging Contaminants, Energy Consumption, Cost Management, Technological Advancements, Industrial Growth and Urbanization, Resilience and Preparedness. With all these issues and points, it became a challenge for chemists to cope with these issues and stick to their work for the world.

What are some examples of steam uses you’ve seen in your career? Justin: Steam for a thermal evaporator I ran on a small Vacom pilot-scale system. The steam would be used in our flash vessel to maintain pressure and run our heat exchanger. It would ultimately boil our target wastewater stream to create (hopefully) cleaner condensate on the back end and concentrated brine as well for encapsulation research. It was a small system rated for only about 0.5 gpm, but it was fascinating to operate! 77

the ANALYST Volume 30 Number 4

What's (Water) on Your Mind? continued

Graeme: In the manufacture of Akubra hats.

Brian: HP (high-pressure) steam created from the manufacture of sulfuric acid to generate 1.1 MW (megawatts) of electricity that went directly into the grid. The LP steam from the turbine set was used to run cooling tower recirc pumps and in the deaerator, too.

Muhammad: Here are some examples: For steam turbines for power generation For chillers For industrial process vacuum For steam-driven pumps For a heating source in sugar industry For a heating source in edible oil industry For a solvent extraction plant In the dairy industry For textile dying For the pulp and paper industry Food and beverages

William: Probably not really common anymore but absorption chillers! Trane Horizons to be specific. Steam to make chilled water. Who would have thought?! Todd: Most common was for heating of commercial buildings but have seen it used for processing of dog food, energy for dryers, chemical stripping of VOCs, and keeping process lines from freezing. My favorite was temporarily heating of a mobile RO trailer for the winter at an oil refinery.

Rabeya: Most commonly in my view: process heating and power generation and sterilization. Paul: Heating buildings, food processing, refining oil, and gasoline, paper manufacturing. Keith: Used Con Ed steam in a NYC chiller plant to clean a chilled water filter lower wedge wire distributor caked with iron and other nasty contaminants. The client had everything in place to achieve a safe solution. Guess that problem was an issue prior to us showing up.

Moderator James McDonald, PE, CWT, is Director of Technology & Marketing with Chem-Aqua. He holds an M.S. in chemical engineering and is a Ray Baum Memorial Water Technologist of the Year award winner (2013). Mr. McDonald also chairs the Association of Water Technologies (AWT) Technical Committee. Key words: BOILERS, CHILLERS, DEAERATORS, MEMBRANES, REVERSE OSMOSIS, STEAM, SURGE TANKS.

Nasro: I’ve Seen LP (low-pressure) steam used as stripping vapor in the bottom of distillation column of crude oil.

Advertising Index Advantage Controls

Pulsafeeder

72 Advantage Controls

Qualichem, Inc

60 AWT Technical Reference and Training Manual

53 Quantrol

58 Bio-source, Inc.

39 Brenntag North America

48 Sanipur US

CHEMetrics

Enviromental Safety Technologies

80 Special Pathogens Laboratory

Radical Polymers LLC

Solugen, Inc.

40 Myron L Company

29 Uniphos

79 Walchem Iwaki America

North Metal and Chemical Company

the ANALYST Volume 30 Number 4