Riviera Utilities Wastewater Treatment Facility

RIVIERA UTILITIES WASTE WATER TREATMENT FACILITY

First installation of Nereda® Aerobic Granular Sludge technology in the United States.

THE PROJECT

The City of Foley, Alabama, and the surrounding area experienced rapid economic growth with few signs of slowing. This growth, along with tightening of regulations for nutrient limits in surface waters, added considerable strain on the Riviera Utilities Waste Water Treatment Facility (RUWWTF) in terms of treatment effectiveness and capacity. These challenges prompted the owner and operator of RUWWTF, to develop a team to plan, design and implement upgrades to the facility.

Goodwyn Mills Cawood (GMC) was selected as its consulting partner.

The receiving stream, Wolf Creek, discharges into Wolf Bay, which is classified as an Alabama Outstanding Waterway. This classification indicates significant probability that nutrient limitations will be imposed.

One major challenge in upgrading the biological process and increasing capacity at RUWWTF as the limited space at the plant site. Further, maintaining existing process operations during the construction duration provided another impediment to the team.

AquaNereda® Aerobic Granular Sludge (AGS) technology was selected as the basis of design with its ability to produce the same effluent quality as an enhanced biological nutrient removal facility, all while consuming significantly less real estate and energy. By utilizing AGS biological treatment, the facility is the first full-scale installation of AGS technology in the United States. The AquaNereda® Aerobic Granular Sludge replaced the extended aeration oxidation ditch process and allowed room for future expansion on the site without the acquisition of new space.

The holistic project consisted of a new influent pump station and headworks, complete with 6mm rotary drum

screens and mechanical vortex grit removal; a three-basin AquaNereda® AGS system; tertiary filtration; sludge thickening; a plant reuse water pump station with a 9,000-gallon hydro-pneumatic tank; and a septage receiving station. The facility has a primary design capacity of 3.5 MGD (with a peak of 10 MGD) and a secondary/tertiary capacity of 3.5 MGD (with a peak of 6 MGD), utilizing the existing oxidation ditch tankage and clarifier as offline equalization. Two (2) existing small clarifiers were converted into aerated sludge thickening prior to dewatering utilizing screw presses technology. In addition to the process equipment, three (3) electrical buildings were constructed to house motor control centers, SCADA panels and other various equipment.

The team of Riviera Utilities, GMC and Max Foote Construction Company of Mandeville, Louisiana completed the construction in the summer of 2020. The construction sequence included three phases to allow for the continued processing of wastewater and discharge into the receiving stream. The process has reduced power consumption at the facility by approximately 40% while also expanding capacity.

GRANULES UNDER MICROSCOPE

GRANULE DISSECTION SETTLING COMPARISON (SVI5) CONVENTIONAL VS. GRANULES THE CYCLE

THE FACILITY 1

Influent Pump Station

The influent pump station was constructed, consisting of a self-cleaning, trenchtype wetwell and six (6) Hidrostal submersible screw centrifugal pumps which convey raw wastewater to the elevated headworks. Two (2) of the pumps are installed in a pre-rotation basin to provide automatic drawdown and cleaning of the wetwell.

Pump Sizes: • Two duty pumps with pre-rotation – 50 hp • Two duty pumps without pre-rotation – 50 hp • Two low flow condition pumps – 20 hp

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Headworks

In coastal areas, large amounts of fine sand and grit often enter the collection system where it is conveyed to the treatment facility.

Inadequate grit removal results in abrasion and abnormal wear of mechanical equipment, loss of capacity in downstream process tanks, and loads the biological process with inert material that reduced efficiency. Continued grit accumulation exacerbates these negative effects.

The AquaNereda® process necessitates a high degree of grit removal—at least 95% removal of all

grit and organic material greater than or equal to 105 microns. The peak capacity - 10 MGD - headworks was designed to achieve this requirement with the installation of two (2) 3mm mechanical drum screens with a single screenings washer/ compactor and conveyor, as well as a vortex grit removal system consisting of one (1) PISTA® 360 with V-Force Baffle™, one (1) PISTA® TURBO™ Grit Washer, and one (1) PISTA® Grit Concentrator™.

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FLOW EQUALIZATION

An overflow weir in the splitter box diverts flows over 6 MGD to the equalization basins where it is fed back to the headworks once flow subsides.

neous feed and discharge 2) aeration 3) settling. Each cycle has a duration of 3.5 hours (Feed/Discharge: 72 min; Aeration: 123 min; Settling: 15 min). The process cycles are staggered for each reactor, allowing one reactor to always be in fill stage; therefore, pre- nor post-equalization tanks are necessary for the AGS process reducing necessary real estate.

The revolutionary aerobic granules developed in the AquaNereda® process allow for biological oxygen demand (BOD) removal, nitrification, denitrification, and phosphorus removal simultaneously in a single tank. The granules have significantly better settling characteristics than typical activated sludge, which reduces settling time and allows for higher MLSS concentrations. In comparison,

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Aerobic Granular Sludge Process (AquaNereda®)

The AquaNereda® Aerobic Granular Sludge (AGS) process included three (3) new AGS reactors with a total treatment capacity of 3.5 MGD on a max monthly flow basis. The reactors have the capability to pass a total peak day flow of 6.0 MGD. The process operates similar to a sequencing batch reactor (SBR) and utilizes aerobic granules to treat the waste. Instead of the typical 5-step SBR treatment cycles, the AquaNereda® process has a 3-step process cycle: 1) simulta-

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MLSS of 8,000 mg/L, the AGS process produces an effluent with BOD5, TSS, TN and TP levels below 5 mg/L, 20 mg/L, 3 mg/L and 1 mg/L. The final effluent TSS concentration can be further reduced to below 10 mg/L with the tertiary filtration process.

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Four (4) 100 horsepower Aerzen® hybrid blowers supply the required oxygen to the biological process. Each blower has a capacity of 1315 SCFM. A small level correction tank provides equalization during the aeration process and is common wall constructed to two (2) sludge buffer tanks. The Sludge Buffer Tanks provide automated thickening and decanting of WAS from the AGS process.

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the SVI5 of granular sludge is comparable to the SVI30 of typical activated sludge. The influent design criteria for BOD5, TSS, TN and TP are 245 mg/L, 225 mg/L, 37 mg/L, and 7 mg/L, respectively. With a design SRT of 18.4 days and a design

TERTIARY FILTERS

Two (2) AquaDisk® cloth media disk filters manufactured by Aqua Aerobic Systems, Inc. further reduce effluent suspended solids and provide a platform process for the chemical phosphorus precipitation and removal. The filters have a peak capacity of 6 MGD.

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UV DISINFECTION & POST AERATION

The existing ultraviolet disinfection system continues to provide effective deactivation of E-Coli and other bacteria. Following the UV disinfection, the treated wastewater cascades down a post-aeration structure to infuse additional oxygen into the water prior to discharging into the stream. This process completes the wastewater treatment process at RUWWTF.

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SOLIDS HANDLING

Two (2) existing clarifiers were converted during the construction process into aerated sludge thickening tanks. The thickening tanks allow for aeration, settling and decanting of sludge. Thickened sludge is then pumped to a dewatering process capable of Class A biosolids utilizing screw presses and a thermal sludge dryer. The repurposing of the clarifiers was instrumental in saving space and reducing cost by utilizing existing tankage.

GMC assisted Aqua Aerobic in the design of the AquaNereda® demonstration facility, located at the Rockford, Illinois wastewater treatment facility.

This demonstration facility was the first installation of the aerobic granular sludge technology in the United States and was placed into operation in January 2018. The design allows for the treatment of an average design flow (ADF) of 200,000 GPD. The process produces BOD/TSS < 10 mg/l, and TN and TP of < 0.5 mg/l, respectively, and is utilized to train operators and engineers in the technical arena of aerobic granular sludge.

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AquaNereda Demonstration Facility

The Nereda AGS technology allows for the design and construction of sewage treatment plants that are more compact, consume less energy and comprise less mechanical equipment.

Startup

After the construction completion, the AquaNereda® reactors at the Riviera Utilities Waste Water Treatment Facility were seeded with standard flocculent activated sludge from the facility’s existing oxidation ditches while raw influent was gradually directed to the AGS reactors.

Small granules, up to 600 µm in diameter, were observed within four (4) weeks after seeding. The AGS reactors achieved adequate treatment performance, even without mature granules. Further, the wellplanned construction sequence and the dedicated staff of Riviera Utilities did not allow a permit violation during the process start-up.

Typically, the start-up time for AGS processes can last from six (6) months to a year when fully-developed granules are established in the reactors. When available, seeding with intact or crushed granules from other AGS facilities can accelerate the granule maturation process and reduce start-up time.

THE PROJECT TEAM

This first-of-its-kind project is the result of successful collaboration between Riviera Utilities; Goodwyn Mills Cawood, project engineer; Aqua-Aerobic Systems, Inc., of Loves Park, Ill., the exclusive supplier of the Nereda® technology in the U.S.; and Cahaba Water Solutions of Pelham, Alabama.

equipment and technology for water and wastewater treatment. CWS’s team strives to provide the most efficient and cost effective equipment solutions to utilities.

Their continued goal is to provide solutions that deliver energy savings and minimal maintenance, while providing excellent customer support.

Riviera Utilities

Goodwyn Mills Cawood

Riviera Utilities is responsible for power, water, wastewater, natural gas, and internet/cable utility services in south Baldwin County. The Utility has proven itself as a progressive and reliable utility that is committed to providing quality services.

The leadership at Riviera Utilities works tirelessly to invest consumer dollars in a manner that benefits its customers for years to come.

The use of efficient technologies and quality management of its people is at the heart of its successful operation.

CahabaWater Solutions (CWS)

Cahaba Water Solutions (CWS) is a leading manufacturer’s representative in Alabama, providing the quality process

Goodwyn Mills Cawood (GMC) is one of the largest architecture and engineering firms in the Southeast, with offices located throughout Alabama, Florida, Georgia, South Carolina and Tennessee. Whether designing schools, parks, hospitals and other commercial developments, or providing clean water, safe streets and restoring resilient environments, GMC takes great pride in serving our communities through the transformative work we perform. Every project is guided by the foundational concept that communities are built by people, not companies, and we strive to serve our communities with quality, integrity, creativity and care. One of the Southeast’s most comprehensive multi-disciplined firms, GMC is equipped to provide all the services associated with architecture, interior design, civil engineering, environmental services, landscape architecture, planning, transportation

engineering, geotechnical engineering, electrical engineering, surveying and disaster recovery. www.gmcnetwork.com

Aqua-Aerobic Systems, Inc.

Aqua-Aerobic Systems, Inc. is an applied engineering company specializing in total water management solutions in the areas of aeration and mixing, biological processes, cloth media filtration, membranes, disinfection and process control. The company is the exclusive supplier of the Nereda® Granular Activated Sludge Process in the United States.

Nereda is the name given to Royal HaskoningDHV’s (The Netherlands) biological wastewater treatment technology (also known as AGS) that purifies water based on bacteria growing into compact granules. The technology was invented by the Delft University of Technology in the Netherlands and developed in a unique public-private partnership between the University, the Dutch Foundation for Applied Water Research (STOWA), the Dutch Water Authorities and Royal HaskoningDHV.