What Microbial Control Strategies Are Followed by AWT Members in Cooling Water Treatment?

Ken Soeder, CWT, Jamestown Technologies Division; John Caloritis, CWT, The Metro Group, Inc.; and Garret Garcia, Masters Company, Inc.; and Members of the AWT Cooling Water Technical Subcommittee

For many decades, a wide variety of water treatment professionals, including product vendors, government regulators, industry consultants, trade associations, and academic scholars, have provided the cooling water marketplace with information on the proper selection and application of microbiocides in open recirculating water systems. These recommendations were usually based on well-investigated studies, and, for the most part, have been very useful to the water treatment vendors who are tasked with implementing successful microbiological control programs in their customers’ cooling water systems.

However, water treatment vendors are often operating under a different set of criteria than their academic and commercial colleagues and need to take other operating factors into consideration when designing their programs. These include factors such as treatment economics, ease of product application, time constraints, safety concerns, and customer acceptance. Historically, any differences in product microbiocide selection and application strategies between the academic and practical sections of our marketplace have often led to conundrums for the water treatment industry.

The purpose of this study was to directly survey AWT member companies to learn just what types of products, equipment, and procedures are currently being used to properly control microbiological issues in their customers’ open cooling water systems. Conducted over the course of two years, the information gathered from the two separate surveys has provided valuable insights on the daily concerns and choices made by our fellow AWT members when implementing their own microbiological control programs. In this article, the authors review all data generated from the surveys and then highlight areas and trends that provided the most insight and benefit to our industry. It should also be noted that these surveys achieved two of the highest response rates ever by AWT studies, so we have a broad database that provides confidence in the observations and conclusions.

Survey Part One—Results Survey Part One was distributed to the AWT membership via the online Survey Monkey application. The survey that was released in May 2018 had a total of 18 questions in a multiple-choice format. Tables A and B provide summary evaluations of the answers to the presented questions. A complete review of the raw data collected from Part One of the Microbiological Control Strategies Survey can be found on the AWT website (www.awt.org).

Table A: Survey Part One – Questions 1 Through 9

Questions Responses

Q1: What technologies does your company use to control microbiological growth in open cooling water systems?

Q2: With EPA registered products, does your firm use the manufacturers’ labels or does your company subregister its own products? Q3: What percentage of your customers’ locations have ASHRAE-188 or Legionella Water Management Plans established by you? Q4: What percentage of your accounts require you to have a state-issued pesticide applicator’s license to administer cooling tower microbiocides? The response to this question was an overwhelming confirmation that more than 90% of responders use EPA-registered microbiocides as their primary strategy, followed closely at 74% by another large group who use microbiological/organic dispersants. We are reminded that the dispersants are not necessarily replacements for biocides but are often used simultaneously to augment a treatment program. From this question, we learned that more than 50% of respondents do in fact use a manufacturer’s microbiocide products/labels exclusively. It was also surprising to learn that 35% of respondents use both manufacturer’s labels, along with their own sub-registered trade name, for a particular biocide chemistry. In 2018, survey respondents reported that Legionella Water Management Plans were still gaining prominence in the water treatment community. In the survey, 73% of respondents reported that 0 to 25% of their clients had formal water management plans in place. The operating assumption is that this trend will continue to grow as more states begin to legislate Legionella requirements, but also as the market continues to shift into taking proactive steps for prevention. The assortment of responses here demonstrates that Pesticide Applicator certification is not a popular requirement in states across the United States. More than 60% of respondents indicated that there was no formal certification requirement, while another 20% only have a requirement in some customer locations. This is assumed to be from the companies who operate in more than one U.S. state.

Q5: What percentage of your cooling systems utilize oxidizing microbiocides? Again, the response to this question overwhelmingly confirms that halogen chemistries are present in more than 75% of member customer accounts. This is based on consolidation around best practices for general microbial control, but also suggests that Legionella control is a significant part of our industry’s concerns.

Table A: Survey Part One – Questions 1 Through 9 (continued)

Questions

Q6: If employed, which types of oxidizing microbiocides are most commonly used in your open cooling water systems? (Check all that apply): Q7: What is the preferred method for feeding oxidizing microbiocides to your systems? Q8: If shock fed, how many times per week is the oxidizing microbiocide typically added? Q9: What percentage of your systems also use non-oxidizing microbiocides?

Responses

Survey results confirm that bromine chemistry is the dominant approach to cooling water microbiological control, followed by sodium hypochlorite and stabilized chlorine. While far less prominent, other chemical and nonchemical strategies are also utilized in meaningful ways.

The answers here were not surprising, with most of the respondents (42%) feeding product with a system controller based on a timer, and another large group (22%) using controllers operated with oxygen reduction potential (ORP) feedback. The consensus is clear here, with most of the respondents (44%) shock feeding an oxidizing microbiocide 1 to 3 times per week. We suspect that this decision is also greatly influenced by program economics, especially in larger systems. Adhering to commonly recommended water treatment protocols, most respondents (54%) are also using a non-oxidizing microbiocide as part of their overall microbiological control program.

Table B: Survey Part One – Questions 10 through 18

Q10: If employed, which types of non-oxidizing microbiocides are most commonly used in your open cooling water systems (check all that apply)? Q11: What is the preferred method for feeding non-oxidizing microbiocides to your systems? Q12: If shock fed, how many times per week is the non-oxidizing microbiocide typically added?

Q13: Do you perform specific test procedures to measure residual levels for non-oxidizing microbiocides in your systems? Q14: Do you primarily use liquid or solid microbiocides (both oxidizing and non-oxidizing products)? Q15: Are your cooling water treatment programs targeting a specific microorganism or foulant class? (Check all that apply) Q16: With your EPA registered microbiocides, do you also use organic dispersant or penetrating agents in your cooling water treatment programs? Q17: Which of the following mechanical strategies does your company also actively support to minimize microbiological contamination in your cooling water systems? (Check all that apply) Q18: Does your company also offer or recommend routine cooling tower mechanical cleanings to your customers? Since we allowed respondents to check several choices to this question, we have a lot of answers—235 in total. Leading the way are isothiazolinone-based products at 26%. This was then followed by DBNPA-based products at 19%, glutaraldehyde-based products at 18%, and quat or polyquat-based products at 17%. Other microbiocides did not seem to have that much of a following. As expected, this question had the most universal answer, with most respondents (89%) using a system controller with a timer to feed non-oxidizing microbicides to the system. This makes sense from both performance and economic perspectives. More than 75% of the respondents stated they are applying non-oxidizing microbiocides on a 1 to 3 times per week application basis. Only about 11% of the respondents apply non-oxidizing microbiocides 4 to 6 times per week. A small minority, less than 5%, are applying non-oxidizing microbiocides daily. Only 22% of survey respondents stated they routinely test for non-oxidizing microbiocide residuals. Less than 20% responded that they test “on occasion,” and 42% of respondents replied they test “not typically.” Almost 20% of respondents stated they “never” test for nonoxidizing microbiocides. Survey results show most vendors (58%) utilize liquid microbiocides, while 41% of respondents state they use a combination of liquid and solid microbiocide products.

In the survey, 96% of respondents replied that they are indeed selectively applying microbiocides to target specific microorganisms. Slime forming, Legionella, and algae were each above 80% of the target organisms.

A substantial amount, 42% of survey respondents, stated they use dispersant/penetrating agents in their cooling water treatment programs on an “always/usual” basis. A minority (38%) responded that they apply dispersant/penetrants “sometimes.” A smaller minority (19%) responded that they “rarely or never” use supplemental dispersant/penetrating agents. The variety of responses clearly shows that most survey respondents are also utilizing mechanical strategies to help control microbial contamination. Sand, media, or bag filtration (74%); cooling tower deck covers (64%); and cooling tower basin scrubbers (42%) were the most cited mechanical strategies followed.

Survey responses showed that some end-users do their own cleanings (23%), while slightly over a third (34%) of respondents state they provide tower cleaning services. A large segment of respondents (43%) only recommended those services to their customers.

Survey Part One Observations Looking closely at the results from the Part One Survey, several observations that are important to our industry can be observed and are outlined here: 1. Despite strong support from AWT over the past 10 years, adoption of the ASHRAE-188 Legionella

Water Management Plan by member companies has been slow. The assumption is that this trend will continue to improve as more states legislate Legionella requirements and member companies shift into more proactive and preventative business positions.

2. Member companies have clearly stated that Pesticide

Applicator Certification is not a popular requirement and is not pursued in states where the certificate is not required.

3. Not surprisingly, oxidizing products are the primary approach used to control microbiological growth in cooling water systems. Surprisingly, with a higher use cost, bromine chemistry is the preferred technology for this application.

4. The introduction of advanced digital system controllers is playing an important and positive role in the feed of microbiocides to cooling water systems. As this equipment improves further, we can expect to see even more advancements in system control, a reduction in microbiocide usage, and a lowering of manpower requirements. 5. Most water treatment vendors do not offer tower cleaning services for their customers. With more evaluation, this segment of the business might represent a new revenue source for member companies.

Survey Part Two—Results After reviewing the results from the Survey Part One, it was decided to develop a second and more inquisitive survey. The purpose of our Survey Part Two was designed to obtain more detailed responses to microbiological use operation of the AWT membership by utilizing a text response to our new set of questions. The Part Two Survey was again distributed to the AWT membership via the Survey Monkey application in March 2019 and had eight new questions. Table C is a summary evaluation of responses compiled by the authors. A complete review of the raw data collected from the Part Two Survey can be found on the AWT website.

Table C: Survey Part Two – Questions 1 and 2

Q1: In our initial survey, it was shown that most of our customers were not operating cooling water treatment programs under an ASHRAE-188 or similar Legionella WMPs. What do you think are some of the main reasons or concerns for customers not implementing a WMP as part of their overall cooling water treatment program?

Response Category Quantity Percent of Total

Not mandated by regulations 12 25.0 Not sufficiently motivated 11 22.9 Cost prohibitive 10 20.8 Uninformed clients 6 12.5

Not worried about risk 3 6.3

Too complicated or burdensome Liability to WTSC Not enough staff

Totals:

3

2

1

48

6.3

4.2

2.0

100

Q2: In the initial survey, we learned that many states do not require water treatment member companies to maintain a Pesticide Applicators Permit to administer microbiocides to a cooling water system. What are your thoughts on water treatment member companies being required to maintain a Pesticide Applicators Permit to feed microbiocides to cooling water systems?

Response Category Quantity Percent of Total

Yes, good idea 23 48.0 No, not needed 14 29.0 Not applicable 4 8.3 Ambivalent, do not care 3 6.3 I am not familiar with this 2 4.2

Laws are confusing (tower biocides overlooked) 2 4.2

Totals: 48 100

Table D shows responses from Questions 3, 4, and 5.

Table D: Survey Part Two – Questions 3, 4, and 5

Q3: With microbiocide applications, many member companies are now using a combination of liquid and solid products in their cooling water treatment programs. What combination of individual liquid and solid products have worked best for your company in cooling water treatment?

Response Category

Combination (equal liquids and solids) Liquids only Primarily liquids Primarily solids Other: chlorine dioxide (Cl02) Solids only

Totals: Quantity

22

14

9

1

1

0

47 Percent of Total

46.8

29.8

19.2

2.1

2.1

0

100

Q4: How are rising state product registration and application fees impacting the selection and use of sub-registered microbiocides at your company?

Response Category Quantity Percent of Total

No effect or business impact 16 34.0 Selling manufacturer’s labeled products 14 29.7 Selective or partial product line sub-registration 9 19.1 Adds more burden or extra cost 6 12.8

Trend limits my product selection 2 4.4

Totals: 47 100

Q5: Some member companies have indicated that they do not use oxidizing microbiocides as part of their overall cooling water microbiological control programs. If your company uses this strategy, what factors would prevent you from incorporating oxidizing microbiocides as part of your cooling water treatment control program?

Response Category Quantity Percent of Total

Always use an oxidizing microbiocide 40 83.3 Feed/equipment issues 4 8.3 Customer/consultant preference 1 2.1 Difficult to control 1 2.1

Discharge requirement Other (non-oxidizing microbiocide)

Totals:

1

1

48

2.1

2.1

100

Table E provides a look at the answers for Questions 6 through 8.

Table E: Survey Part 2 – Questions 6, 7 and 8

Q6: Recent data suggest that recirculating potable (or domestic) water systems in large buildings are important breeding grounds for Legionella bacteria. If offered, what technologies does your company use to provide Legionella control in your customers hot and cold recirculating potable water systems?

Response Category Quantity Percent of Total

Company not involved in this marketplace 22 45.8 Chlorine/ClO2 11 23.0 Chloramine 6 12.5

Monitoring/review only Copper/silver Peroxide 5

2

1 10.3

4.2

2.1

UV disinfection 1 2.1

Totals: 48 100

Q7: What are your major concerns with EPA-registered microbiocides that are currently available to or marketplace?

Response Category Quantity Percent of Total

No major concerns 23 49 Product cost 8 17

Lack of competition/overseas manufacturing Complicated and costly sub-registration process Product performance Safety and handling

Totals:

5

4

4

3

47

10

9

9

6

100

Q8: Do you anticipate any new microbiocides being introduced to the marketplace soon?

Response Category Quantity

No 35

Yes, traditional technologies Yes, “green technologies” Do not know 6

2

2

Hope so!

Totals:

2

47 Percent of Total

75

13

4

4

4

100

Survey Part Two—Observations The purpose of the Survey Part Two was to look deeper into some of the answers provided by member companies in the initial survey and to better understand the factors influencing their responses. Here are some general observations from the Survey Part Two answers:

1. Several strong and varied responses were given to support the low acceptance rate for the ASHRAE-188

Legionella Water Management Plan by member companies. Primary reasons included the lack of state and federal regulations mandating these programs, the high setup and maintenance costs associated with the plans, and a lack of motivation by member companies. Hopefully, AWT will consider and act upon these concerns as the organization moves forward.

2. In terms of Legionella control in potable or domestic water systems, almost 50% of respondents stated that they are not involved in this aspect of the water treatment marketplace. Perhaps a future survey could investigate reasons for this hesitancy, as this may be an overlooked business opportunity for member companies.

Overall Trends Identified The data were evaluated by reviewing, categorizing, and quantifying each response. The evaluation allowed for identification of trends that were underway, with the following six being the most noteworthy. Future surveys will confirm whether these trends hold over the long term, or whether new ones will emerge for reporting back to members.

1. Regulations are taking hold: At the time the surveys were issued, regulations mandating product selection and program activities had already begun in both the state and city of New York. Since then, several states have laws being considered that are expected to be enacted. Those regulations should inevitably increase overall microbiocide demand and usage.

2. Oxidizing agents continue to lead as primary

microbiocides: It was not surprising that the oxidizing chemistries used by the cooling water treatment industry continue to lead as our primary microbiocides. However, many companies have adopted alternative or supportive chemical strategies to augment these oxidizing technologies.

3. Automation is increasingly used to dose

microbiocides: During the past 10 or more years, great progress has been made by equipment vendors on the automation of controllers used to dose microbiocides to open cooling water systems. Now, digital system controllers can track a wide variety of cooling water parameters, such pH, conductivity, temperature, and ORP readings on a real-time basis, and present this information instantaneously to water treatment vendors and customers alike.

Advanced systems also allow the data logging of vast amounts of information and allow vendors to make changes to water treatment parameters, including microbiocide feed rate and times, from remote access points such as personal computers and hand-held devices. If used properly, these digital controllers will enable service companies to have much better control of their customer’s cooling water systems and even result in a reduction in the actual amounts of microbiocides needed to obtain desired control results.

4. An unexpected acceptance of some “niche”

microbiological control approaches: During the past years, we have seen an increase in the use of unconventional microbiological control approaches in cooling water systems, including technologies such as chlorine dioxide, onsite generated halogens, and supporting biological dispersants. It will be interesting to see if these new technologies gain increased acceptance in our industry over the upcoming years.

5. Use of liquid halogen chemistries leads solid

products: Use of solid halogen donor biocides has been on a continuing decline. The ease of application and control for liquid halogen donors has become widely accepted. Also, users do not want to handle solid halogens or deal with dusting or similar handling issues. Furthermore, solid halogen donors have become more price sensitive of late, and global supplies have become very tight; that trend is very likely to continue.

6. ASHRAE 188 acceptance was lower than

expected: Without the force of local and regional legislation, there has been no continuing pressure for either end-users or water treatment service companies to more aggressively embrace the

ASHRAE 188 standard. Outside the city and state of New York, there are no legal mandates in the

United States for Legionella control utilizing the

ASHRAE 188 Standard at this time. Compliance with the standard, although not prohibitive, is costly in both dollars and time, which has translated into less than expected adoption.

Overall Conclusions As any seasoned water treatment professional knows, maintaining proper microbiological control in a recirculating cooling water system is critical to the overall success of the program. Improper microbiological control can lead to a myriad of other operational problems, including increased corrosion rates, accelerated deposition, excessive utility costs, shorter equipment life, and even health and safety concerns.

With this “Microbiological Control Strategies” project, AWT’s Cooling Water Subcommittee was able to successfully survey the association’s membership to learn

what types of microbiological control products and strategies they use in their own situations and companies. By gaining a better understanding of the practices used by our colleagues, the survey will enable member companies to more closely evaluate their own programs to see if any changes and improvements can be made to ensure the success of their own operations. Although we are confident that very good, valid, and broad data was generated by this study, it must be noted that a project of this type needs to be re-evaluated on a regular basis to ensure that current and useful data is always provided to the AWT membership.

The Microbiocide Survey completed in 2019 had the highest response rate and was the most comprehensive survey conducted by AWT to date. We suggest that an updated survey and paper be done in three-tofive-year intervals to update the information. Using a Microbiocide Survey as a living document would provide AWT membership with timely and ongoing information for a very important part of our water treatment marketplace.

Kenneth Soeder, CWT, recently retired as the senior technical advisor for Azure Water Services. He previously was a founding and a principal partner in Azure Water Services and president of the company’s Jamestown Technologies Division. During Mr. Soeder’s 38-year involvement in the industrial and commercial water treatment industry, he has published more than 12 technical papers on corrosion, deposit, and microbiological control in various water-handling systems, and has also been granted four U.S. patents for new product developments. He graduated from the State University of New York (SUNY) Oneonta with a B.S. in biology and chemistry and has also received an M.S. in water resource management from the SUNY College of Environmental Science and Forestry at Syracuse. Mr. Soeder is available at soeder@comcast.net. John Caloritis, CWT, holds a B.S. in chemistry and is the technical director of The Metro Group Inc. He has spent 37 years in water treatment in multiple roles, all with one firm. Mr. Caloritis has been active within AWT as both a member and chair of the Cooling Water Subcommittee and a member of the Legionella Task Force, and was recently elected to serve on AWTs Board of Directors. He can be reached at jcaloritis@ metrogroupinc.com.

Garret (Gary) Garcia became involved in water treatment as a young high school student, continuing through college working with Masters Co. Inc. (MCI), which he and his family later purchased. Some of the many facets of Mr. Garcia’s experience include laboratory testing, pilot formulations, field applications, method development, production blending, and operations. Over the years, he has served on several AWT committees, including Cooling Water and Special Projects as well as the Supplier Task Group. Mr. Garcia continues to serve as MCI’s technical director as well as at the firm’s sister division, LiquiLogic, LLC. He may be reached at gary@ masterscoinc.com.