Decanter centrifuge reduces biosolids disposal costs

Problem

Hollandia Dairy in Southern California was paying to transport 25,000 pounds of wastewater biosolids a day.

Solution

An Alfa Laval ALDEC 20 decanter centrifuge now concentrates solids from moving bed biofilm reactor (MBBR) wastewater before further processing into Class A biosolids. The skid-mounted unit was selected as a tried and tested technology; it includes the company’s Connectivity remote monitoring support.

Result   

The decanter handles 3,000 gpd of wastewater and achieved the expected results. With the additional processing, the dairy now trucks away only a small amount of Class A biosolids that can be used for purposes such as fertilizer. “After meeting the experts at Alfa Laval, my world became so much easier,” says Hank van Nieuwenhuyzen, Hollandia chief operating officer. “I had someone to guide me through the possible solutions, and during the process, I learned so much about wastewater.” 866-253-2528; www.alfalaval.us

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Rotary press enables city to dewater more efficiently

Problem

The City of Lancaster, South Carolina, had a biosolids dewatering system that could not keep up with demand. Population growth along with aging, unreliable equipment forced the city to haul liquid material at high cost even when the dewatering system was running. The system could process only 14 gpm and deliver 8% solids. 

Solution

After a successful pilot test, the city installed a rotary press from Fournier Industries while the dewatering system was down. The city chose a six-channel rotary press, which was installed in July 2019. 

Result

After four months, the press was processing at 80 to 100 gpm and delivering cake at 17-18% solids. The digesters are now emptied in two to three days rather than two weeks. The staff now can choose which days to run. “Our budget for polymer is going to drop by two-third, and I no longer have to worry about my solids levels,” says Donnie Ledford, plant superintendent. 418-423-4241; www.rotary-press.com

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Dewatering drum a fit for compact space

Problem

The owners of Greenway Waste Solutions of Charlotte, North Carolina, set out to build a compact dewatering facility that would be easy to replicate on other small parcels.

Solution

The company chose the dewatering drum from In The Round Dewatering, as it can be left stationary without affecting other parts of the operation. “This saves us time and space because we are able to build close to the drum,” Reese Blackwell says. “Our cake comes out exponentially drier than with the dewatering options we have used in the past. We do not need to get into the drum to wash it down. This cuts downtime for hauling a box to and from a composting site and the intensive washing when it returns.” A technician augers out the solids onto a pad and then loads a roll-off container. Automatic rotating pressure nozzles clean the unit for the next batch to load.

Result

“We have really enjoyed the drum, and it has made our operations more efficient,” Blackwell says. 317-539-7511; www.itrdewatering.com

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City upgrades headworks package to meet regulations

Problem

To comply with stricter phosphorus effluent limits, Morgan City, Utah, needed to upgrade its headworks.

Solution

The city chose an all-stainless steel headworks package from Lakeside. The system combines a 6 mm Raptor mechanical fine screen with a bypass bar rack, plus a SpiraGrit vortex grit chamber in an elevated, preengineered system. Jamie Grandpre, senior water/wastewater operator, worked with J-U-B Engineers on phased solution. “We needed a long-lasting mechanical fine screen and grit removal system and so visited other facilities in Utah to speak to operators,” says Gary Vance, project engineer at J-U-B. “Finding reliable, low-maintenance equipment that could stand the test of time was a must.”

Result

“With a strong and reliable screen and grit removal system, the negative impact on the plant has been solved,” Grandpre says. “We’ve had no issues with the equipment. It is very easy to maintain.” 630-837-5640; www.lakeside-equipment.com

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Mixer helps municipality save on polymer costs

Problem

City of Port Angeles, Washington, needed to mix a 24-by-27-foot, cone-shaped biosolids storage tank holding 40,000 gallons of biosolids at 2% solids. The material would then be sent to a dewatering press.

Solution

The Kennedy/Jenks engineering firm looked for a system to maintain biosolids consistency before sending to the dewatering press. Pulsed Hydraulics provided a Model 310 large-bubble mixer with one bubble-forming plate and a 7.5 hp rotary screw compressor (sized for additional plant uses). The plate is at the bottom of the cone next to the discharge valve. The system was adjusted to inject one large bubble every 20 seconds. 

Result

Before the installation of the mixer, the plant was using 1.5 totes of polymer monthly at a cost of $5,300 per month. The consistent biosolids from the mixed storage tank reduced polymer consumption to one tote per month, saving $19,300 per year. The belt press no longer requires constant adjustment. 800-641-1726; www.phiwater.com

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Utility authority to install three new screw presses

Problem

The West Rankin Utility Authority serves several communities in Mississippi, sending 10 to 12 mgd of wastewater to the Savanna Wastewater Treatment Plant in Jackson at a cost of a few million dollars per year. To save money and operate independently, the authority decided to build a wastewater treatment plant.

Solution

The authority selected three of Schwing Bioset’s largest dewatering screw presses, model FSP 1203, designed to handle up to 7,468 dry pounds per hour. The authority expects to process 24 dry tons per day operating 60 hours per week, dewatering waste activated sludge at 0.75% solids to a 17% solids cake with at least a 90% solids capture rate.

Result

With the screw presses, the authority will bring its system into compliance with federal water-quality laws, increase plant capacity and save costs. 715-247-3433; www.schwingbioset.com

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Screw press enables efficient dewatering at resource recovery facility

Problem

Utah-based Wasatch Resource Recovery is a treatment facility that processes food and other organic wastes. When the engineering team investigated biosolids dewatering options, Trident Processes provided early-stage design and capacity recommendations.

Solution

To provide efficient, reliable dewatering, the company chose the MD 454 multidisc screw press with floc and mixing tank from Trident Processes. The four-cylinder press dewaters anaerobically digested biosolids at 185 gpm to dry, phosphorus-rich cake for land application. Norman Robinson, senior plant operator, observes, “Because we receive a variety of organic wastes, we need to process sludge that often changes its characteristics, but still produce a consistent, dry cake.” The press is integrated with the plant’s automation system and processes biosolids continuously.

Result

The cake is consistently at 21%-25% solids range, allowing smooth handling and transportation. After the initial optimization, the client has seen low polymer consumption and low operating cost. “We do some visual checks during the day and perform the occasional washdown and greasing,” Robinson says. “The press simply does its job without requiring much of my time.” 800-799-3740; www.tridentprocesses.com

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District upgrades grit removal system to save on process wear

Problem

Aging aerated grit facilities at the North Davis Sewer District treatment plant in Syracuse, Utah, caused downstream process tanks to fill with grit and accelerated wear on process equipment. Annual basin clean-outs burdened the staff.

Solution

The district employed an in-house plan involving all 24 staff members to design, install and maintain a new grit removal system inside the existing tankage. It includes a hydraulic forced- vortex grit removal system from Smith & Loveless, installed as an in-kind replacement that did not require new-construction permits. The in-house project eliminated consulting and contracting costs and reduced grit handling and maintenance expenses.

Result

The district completed the first round of the project in 2018, converting one of two aerated grit chambers to the hydraulic forced-vortex process. The system is online and removing ample grit to protect downstream processes and equipment. 800-898-9122; www.smithandloveless.com

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Screening system eases district’s septage receiving

Problem

The West Montrose Sanitation District in Colorado needed a low-maintenance septage receiving unit requiring minimal staff operations time.

Solution

The district chose the Maxi Screen 400 unit from ScreencO Systems. It was built and designed by operators who struggled with automatic screening equipment, and it has virtually no moving parts and requires minimal maintenance.  

Result

In the first two years, the district received 1,283 loads and processed 1.47 million gallons of septage. The dual screen size enables rapid dumping without compromising screening. “We were amazed at the amount of material the screens collect,” says Andres Garcia, district manager. The Grit Eliminator in 2018 removed roughly 8.2 tons of grit, reducing wear and tear on pumps and cutting costs for cleaning out basins, pits and pipes. “We intended our receiving station to be an alternative to land application but quickly found that most haulers prefer to dump at our facility,” Garcia says. “They can haul two to four additional loads per day due to the ease and practicality of the facility.” 208-790-8770; www.screencosystems.com

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Gravimetric selection technology employed at recovery facility

Problem

The Ephrata Borough (Pennsylvania) Authority Water Resource Recovery Facility has battled chronic sludge settling issues since a biological nutrient removal upgrade in 2011. During winter, sludge volume index values have reached up to 300 g/mL.

Solution

The authority chose gravimetric selection technology to retain denser biomass while wasting the lighter fraction of mixed liquor suspended solids. A gravimetric selection system from World Water Works became operational in January 2019. The overflow of MLSS light fraction gravity-feeds to an existing scum collection pit, where pumps transfer waste sludge to solids handling. The underflow of the denser MLSS gravity-feeds back into the return activated sludge tank, from which it is pumped back to the head of the oxidation ditch.

Result

Within several weeks, the SVI was reduced from a monthly average of 144 g/mL to 71 g/mL. The MLSS settling velocity also improved with the clarifier sludge blanket levels. As settling continued to improve, the plant reduced their powdered activated carbon addition by about 70%. The system continues to show stable performance with effluent ammonia less than 1 mg/L on average. 800-607-7973; www.worldwaterworks.com