Reuse, Recovery and Energy Management

Treatment plant uses microturbines to generate heat and power

Problem: In upgrading the boiler used to heat anaerobic digesters at the 15 mgd Sheboygan (Wisconsin) Regional Wastewater Treatment Plant, the plant’s superintendent wanted to solve two problems at once: use excess biogas and reduce electricity.

Solution: The plant ultimately in-stalled 10 30 kW C30 combined heat and power microturbines from Capstone Turbine. The city agreed to purchase all the electricity produced and provide all the needed biogas fuel.

Result: The microturbines generate up to 2,300 MWh per year. The exhaust heat maintains the proper digester temperature and heats the plant buildings in winter. The microturbines can generate 1 million Btu/h, amounting to 73,000 therms per year — enough to heat 60 homes. 818-734-5300;

City uses digesters to rid lift stations of hydrogen sulfide

Problem: The city of Taylorville (Illinois) Street/Sewer Department faced issues with hydrogen sulfide in three lift stations and with biofilms further downstream in the delivery piping to the wastewater treatment plant. The discharge manhole H2S readings were over 700 ppm, and local residents complained of odors.

Solution: The city purchased three Little John Digesters from DO2E Wastewater Treatment. After the first month of running the digesters with ozone, the average H2S levels at the three lift stations were 42 ppm.

Result: “These digesters have made a tremendous difference not only in odor control, but also in heavy matting and FOG removal,” says Richard Wiseman, street and sewer superintendent. “The FOG and heavy matting have never reformed in the stations nor down the collection lines. We have received no further complaints.” 251-937-8200;

Shredder used on university food court waste increases biogas production

Problem: The West Lafayette (Indiana) Wastewater Treatment Plant uses anaerobic digestion and wanted to increase biogas production after rehabilitation of aging digesters.

Solution: Dave Henderson, plant operator, read about Purdue University’s food court sending 20 tons of food waste a month to landfills. The plant team and the university work together using a 4-SHRED-H food waste shredder from JWC Environmental. The high-strength organic material is macerated and fed to digesters to produce biogas for electricity generation.

Result: The digestion process aided by the shredder produces around 37 cfm of biogas. The plant generates 15 percent of its electricity — 728,000 kWh — for $50,000 in annual savings; Purdue University saved money by reducing landfilling. 800-331-2277;

Twin-auger mixer assists city in composting biosolids

Problem: Kodiak, Alaska, could not landfill its biosolids or efficiently compost the materials because mixing conditions were suboptimal.

Solution: The city purchased a Knight VT 144 Vertical Maxx stationary mixer from Kuhn North America to help better blend biosolids and wood-chips for composting. Kuhn also supplied a belt conveyor that moves discharged compost to a collection bunker.

Result: “The most obvious benefit of using the mixer is how fast we can mix and make compost,” says Steve Gauna, lead compost operator. The process creates an ideal mix of biosolids and bulking agent to compost in 40 minutes versus 120 minutes previously. Labor cost per ton has been reduced significantly. 608-897-2131;

Pump is a fit in challenging install

Problem: The water treatment plant at a southern Florida municipality faced a challenge replacing a pump in tight quarters through a window.

Solution: Ruthman supplied a Deming Model 24HH-2C 24-inch-diameter, 200 hp pump measuring 152 inches. It was dropped in three pieces into a hole 90 inches tall from the pad to ceiling. The pump delivers 9,360 gpm at 55 inches total dynamic head.

Result: The installation was successful. The pump ran so smoothly and quietly that “you could set a penny on the edge and it would not move,” says Dan Torongo of Process Systems. 859-824-3100;


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