Case Studies: Biosolids and Biogas Technology

Case Studies: Biosolids and Biogas Technology

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Wastewater plant finds creative upgrade

Problem: The F. Wayne Hill Water Resources Center in Gwinnett County, Georgia, dewatered biosolids with six Alfa Laval Sharples DS-706 decanter centrifuges. The machines delivered performed well and were reliable, but technology had advanced and the team wanted to explore sustainable solutions.

Solution: The 20-year-old decanters were replaced with ALDEC G3-125 decanters from Alfa Laval that improve performance and efficiency while using fewer resources.

Result: The units increased cake solids from 21% to 23%, reducing weight hauled to landfill by 6,000 tons annually. They also saved more than $300,000 a year polymer costs and saved significant energy. The next phase will add dryers to remove 90% of the water from biosolids, yielding a saleable fertilizer, generating revenue and eliminating hauling costs. 713-934-3160;

High-capacity septage receiver improves operation

Problem: A Kentucky wastewater treatment plant implemented a solution to prevent wear and tear on downstream pumps from septage receipt. Plant officials settled on dedicated screening for septage to capture more debris. Requirements included a small footprint, a through-flow screen design with a moving bar grid, the ability to carry large materials including rocks and debris to an integral compactor, offloading using no brushes and screening deposition into a compactor with a high-torque motor.

Solution: The plant team selected a Hydro-Dyne Engineering Dusky Shark Septage Receiving System.

Result: Septage haulers are extremely happy with the septage receiver speed and durability. The system is used to offload a typical 2300-gal tank in 10 minutes or less. The screen starts automatically when a truck starts the flow of septage and shuts down when the flow stops. The traveling bar grid changes speed for effective capture and to remove rags that can bind rotating equipment downstream. The receiver has internal water spray nozzles that rinse the tank and screen. No manual interaction with the system is needed. The screen picks up rocks, and the high-torque compactor can crush large objects. Screening volume is reduced by over 80% from the high torque compactor resulting in a minimum of waste carried offsite with a moisture content less than 50%. 813-818-0777;

Dryer system reduces biosolids hauling risks

Problem: The City and Bureau of Juneau, Alaska, produces 7,000 wet tons of dewatered biosolids each year. The material is hauled 1,300 miles by truck, barge and train to the Columbia Ridge landfill in Arlington, Oregon. This transport poses multiple risks and costs, and the utility faced uncertainty over environmental regulations.

Solution: Officials chose the Veolia BioCon medium-temperature belt dryer. The Class A EQ product provides pathogen reduction and diversifies end uses, which can include landfill cover material, fertilizer for community sites and parks, erosion control and topsoil replacement. These uses offer potential for significantly lower cost versus long-distance shipping to landfill.

Result: The dryer is designed for 36 wet tons per day and produces 5.5 tons of dried product, an 85% reduction in volume and weight. 919-677-8310;

Rotary press helps plant increase dewatering capabilities

Problem: The Glasgow (Kentucky) Wastewater Treatment Plant serves a community of 15,000 and also provides treatment for Barren River State Park and two elementary schools. The replacement of rectangular secondary settling tanks by circular clarifiers greatly improved settling and solids capture capacity. Consequently, the plant found itself with additional biosolids. 

Solution: A Fournier Rotary Press was installed to increase dewatering capacity. On summer days, solids at the bottom of the clarifier are thick enough to feed the presses without polymer. Polymer is required only in cold weather. In summer, solids are spread on drying beds to save on power costs. In all seasons, dewatered cake is trucked to the city landfill.

Result: “It has worked great for us,” says Jacob Billingsley, superintendent. “We run it about 3 1/2 days a week. After seven years of operation, we’ve spent less than $400 for parts, and we only use a gallon and a half of polymer an hour. That’s our biggest savings. Having a SCADA system decreases the chance of a failure and loss of solids.” He can dial up plant operations, receive alarms and make process adjustments using his cellphone. 800-463-6328;

Screening system eliminates wipes issues

Problem: Wipes were an ongoing issue in Glenbard, Illinois, causing maintenance issues with blocked pumps, aeration systems and other downstream equipment. Grinders did not solve the problems because the shredded material remained in the system and formed clumps downstream.

Solution: MS Bar Screens with 3/16-inch bar spacing from Headworks International now remove nearly all wipes from the flow.

Result: The utility saved significant money and aggravation. The bar screen helps prevent fatbergs and overflows and frees up labor for more important work. 713-647-6667;

City improves operation and throughput capacity

Problem: The city of Marengo, Illinois, faced capital costs estimated at $2.1 million to repair and upgrade its aging temperature-phased anaerobic digestion process. The city sought an alternative disinfection and stabilization process.

Solution: The city commissioned a CleanB system from BCR Environmental. 

Result: The process consistently met Class B disinfection and vector attraction reduction requirements and significantly reduced repair, maintenance, energy and polymer costs, while also reducing odors. In addition, with reduction in nutrient return from digestion, effluent nutrient concentrations continue to decline. The system will enable the city to outperform regulatory requirements for biosolids and effluent. 866-724-9145;

Overcoming escalating biosolids disposal costs

Problem: The Kalamazoo (Michigan) Wastewater Treatment Plant treats a mix of residential and industrial wastewater. Industrial loading accounted for 65% of influent BOD. The city faced rising costs for biosolids handling; landfill costs increased from $17.50 per wet ton in 2008 to $158 in 2020.

Solution: The city installed three Centrisys CS26-4 decanter centrifuges, which increased cake solids and substantially reduced biosolids volume.

Result: The centrifuges improved the cake solids content from 16-17%, with the presses to between 21-23%, at 20-30% volume reduction. This reduced costs by $2.5 million per year. 262-747-2384;

Facility develops strategy for optimizing aerobic digestion

Problem: The Jacksonville Beach Water Reclamation Facility’s digesters were using excessive energy, lacked homogeneous mixing and were not optimized.

Solution: Contrary to the common belief that aerobic digestion requires continuous aeration, a more effective and energy-efficient approach is cycling between mixing and aeration. This process improves nutrient reduction, alkalinity, dewaterability and volatile solids destruction by supporting endogenous respiration and nitrification. The HYPERCLASSIC Mixing and Aeration System from INVENT Environmental Technologies performs both mixing and aerating in one device, reducing the need for multiple equipment types. Additionally, since the device maintains a homogeneously mixed basin both with and without aeration, it allows for a unique level of process control and optimization. The enhanced control over aerobic digestion reduces operational costs and chemical addition, while improving energy efficiency. Its design includes a nonclogging hyperboloid mixer-body that ensures continuous, efficient mixing and aeration, even at high MLSS levels.

Result: The aerobic digesters treat to 3% solids in three circular tanks and provide consistent quality feed to their dewatering process. The treated biosolids continue to meet Class B standards. 973-571-2223;

University upgrades system to handle variable flows

Problem: The University of Mississippi needed to upgrade to its wastewater facility built in 1972 as a dual-basin extended aeration plant. Flows varied widely with swings in on-campus population, from near zero at the Christmas break to extreme flows during home football games.

Solution: ESI converted one basin to a 0.75 mgd oxidation ditch (Lakeside Equipment), replacing the existing clarifier and recirculation pumping, upgrading the headworks and converting the other aeration basin to flow equalization. The Closed Loop Reactor process consists of reactors with a single feed for raw wastewater and return activated sludge. The simple racetrack configuration provides a straight-line flow for wastewater from the headworks to the final clarifiers. 

Result: The system has proven simple yet effective with a single drive that keeps maintenance and energy costs low. Aerators are controlled based on dissolved oxygen using variable-frequency drives. 630-837-5640;

System maintains homogeneous biosolids to create efficient dewatering operation

Problem: Operators of the Scarborough Wastewater Treatment Plant in Narragansett, Rhode Island, wanted to produce more uniform and consistent consistency to affect a more readily dewaterable biosolids.

Solution: C3ND Environmental Consulting provided a PHi-CA mixing system from Pulsed Hydraulics due to its simplicity, mixing energy, and ability to maintain consistently uniform sludge solids throughout the entire holding tank. The system can be operated as needed during the period when the dewatering process is ongoing. The system consists of a bubble forming plate connected to 50 feet of chemically resistant air hose and a 1 hp linear air pump. Since this a portable device, the Scarborough staff moves it to one or more of their pump stations to eliminate grease and other debris accumulation.

Result: Requirements were met and verified by the customer’s Superintendent Scott Goodinson, president-elect of NEWEA. 800-641-1726;

Company aids water treatment plant in repairing damaged equipment

Problem: A wastewater treatment facility in Amarillo, Texas, had a spillage emergency in 2023 caused by lack of repair and maintenance over many years. The spill lasted three days and spread 1 million gallons of partially treated sewage. A detailed review turned up six critical repair needs: blowers, headworks, site electrical, influent pump station, north secondary clarifiers and sludge equipment. 

Solution: Rebuild-It Services and Newman Regency Group are working to rebuild, update and repair two damaged clarifiers. The team will also support the six repair needs. The first repair of the secondary clarifier was completed in a few weeks, followed by a rebuild of a primary clarifier drive. These repairs enabled more high- and low-flow capabilities, thus avoiding future spillage. 

Result: The plant team is confident that Rebuild-It engineers will help them with many other repairs over the next few years. The team will advise plant operators, repair equipment quickly and efficiently, and incorporate preventive measures to safeguard against future incidences. The team will also assess other equipment and offer retrofit services to further increase plant efficiency. 888-709-5676;

Cost Savings with screw presses at water reclamation facility are notable

Problem: The Big Creek Water Reclamation Facility in North Fulton County, Georgia, is the county’s largest in flow and service area. To accommodate population growth and economic development, the facility needed more capacity.

Solution: A phased expansion with multiphase construction started in 2020 with expected completion in mid-2024. The project included a new dewatering building commissioned in May 2022 and including two Schwing Bioset FSP 1203 screw presses, designed to replace five smaller screw presses. Each new press can process 2,600 dry pounds per hour of aerobically digested biosolids, versus a previous maximum throughput of 550 dry pounds per hour. 

Result: The presses operate 18 hours a day, five to six days a week. Five 25-ton trailers of biosolids are hauled to landfill daily. Hauling and landfill costs, electricity usage and maintenance all have been reduced. Each screw press operates at 50% of design capacity. The facility is ultimately designed for five FSP 1203 machines. 715-247-3433;

Water reclamation facility implements grit removal system to improve plant operation

Problem: The 6 mgd George F. French Water Reclamation Facility, operated by Destin Water Users, serves a population of nearly 20,000 that can triple during vacation seasons. The grit removal facilities installed in 1983 were poorly performing, requiring frequent and costly maintenance.

Solution: The utility chose a baffled vortex PISTA VIO system from Smith & Loveless for its performance, small footprint, low maintenance, long service life and variable flows. The system offers variable inlet-outlet flexibility along with a 10-1 turndown, allowing flow variations from 1.2 to 12 mgd while removing 95% of particles down to 100 microns. Stainless steel tankage combats seaside concrete degradation. The system was fabricated in a controlled environment and delivered to the job site for low-cost installation.

Result: The facility team has not found grit in its downstream basins, and significantly more grit is entering the dump container. Grit removal efficiency tests demonstrate greater than 98% removal of particles down to 100 microns. 800-898-9122; 

Osmosis dehydrator saves on cake disposal costs

Problem: The Henderson, Kentucky Wastewater Treatment Plant dewaters their biosolids to 17% cake solids via belt filter presses. Plant operators needed a way to further dry the solids to save in hauling and disposal costs.

Solution: They installed a 3.0-meter-wide Elode Electro osmosis dehydration dewatering unit from Charter Machine along with sludge holding bin and conveyors. The technology effectively takes 17% total solids cake and dries it to 42% total solids cake in under 2 minutes, with only the use of electrical AC power converted to DC power. It introduces the belt press dewatered cake to this DC field to separate water from solids via electrophoresis and electroosmotic processes. 

Result: Use of the Elode Electro unit resulted in a 60% reduction in hauling costs for the plant. 732-548-4400;  


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