Centrifuges help treatment plant save substantial annual costs

Problem

The Greenway Wastewater Treatment plant in London, Ontario, used belt presses to dewater biosolids. The solids content was such that the plant had to use ancillary fuel to maintain the temperature in the fluidized bed incinerator.

Solution

The plant installed three Flottweg C7E centrifuge units. The process operates 95% of the time, and two of the units run at all times. The machines each accommodate 1,200 liters per minute of liquid material, or 1,700 kg per hour of mass flow.

Result:

The centrifuges enable the plant to increase the solids content to about 26%, and ancillary fuel is no longer needed, leading to savings of nearly $700,000 per year. 859-448-2331; www.flottweg.com

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Press reduces hauling costs for municipality

Problem

 The wastewater facility in Haysville, Kansas, treats 650,000 gpd (2 mgd design). Biosolids are aerobically digested. At 1.5% solids the material was costly to haul to farms.

Solution

The plant team installed a Fournier Rotary Press, which has multiple modular dewatering channels rotating at 1 rpm on a single shaft. The liquid enters at low feed pressure (5 psi) and drains as it rotates. It is squeezed through a restrictor valve and extruded as 18% solids cake. The four-channel press is expandable to six channels for growth.

Result:

“The press processes biosolids right from our holding tank and dewaters it to the highest level possible” says José Aguilar, plant superintendent. “Since startup we haven’t had to do anything on it. Its low rotation really translates to reliability and low maintenance.” 418-423-4241; www.fournierdewatering.com

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Two-stage screening provides low effluent levels and downstream protection

Problem

 The Malden Public Service District in Charleston, West Virginia, constructed a new wastewater treatment plant to maximize capacity and help meet tighter discharge requirements. To maximize performance, a high-quality headworks system was needed.

Solution

The district had enjoyed ease-of-use and operator-friendly Parkson Aqua Guard screens at the previous facility for over 20 years. For the new facility the staff chose Aqua Guard self-cleaning screens. Two Aqua Guard UltraClean MN units (15 mm coarse screens) are followed by two Aqua Guard PF perforated plate screens (1/4-inch fine screens). Two-stage screening maximizes solids removal. The units run in a series, augmented by two Aqua WashPress washer-compactors.

Result:

The units effectively remove debris with low maintenance, so that downstream equipment is protected and the treatment process works efficiently. “The overall performance of the screens beat all our expectations,” says Josh Jeffrey, general manager. “The ease of use and low maintenance really make for a fine machine.” 888-727-5766; www.parkson.com

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City converts biosolids processing to meet the growing needs

Problem

 The wastewater treatment plant in Otsego, Minnesota (population 17,000) treats 4 mgd and produced Class B biosolids via aerobic digestion for liquid land application. The plant required an expansion, while residential development limited application sites nearby and prevented expansion of the plant’s footprint. 

Solution

The city installed dewatering equipment along with the Schwing Bioset lime stabilization process. This eliminated the digesters by processing waste activated sludge directly to Class A biosolids. The facility can also operate in a Class B mode, reducing costs when sending material to the landfill in winter. The equipment’s small footprint easily fit the existing site.

Result:

The plant produces Class A biosolids at a cost comparable to aerobic digestion, but with more flexibility in operation. The process improved solids treatment and reduced the overall plant footprint. 715-247-3433; www.schwingbioset.com

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Treatment plant expands ion exchange system to treat total organic carbon and color

Problem

Palm Beach County needed to address issues with total organic carbon, disinfection byproduct precursors, and color in finished water. An initial installation of a 10 mgd seven-vessel ion exchange system was effective, but the county wanted to add ion exchange capacity for TOC and color removal.

Solution

The initial installation, an Organix ion exchange system from Tonka Water, a Kurita America Brand, was installed downstream from the lime softening process. Kurita America then helped design a cost-effective addition of 14 vessels and 20 mgd of additional capacity. The system, now 21 vessels with 30 mgd capacity, is one of the nation’s largest municipal ion exchange systems. Treatment begins with lime softening, clarification and gravity filtration. The water then flows to the ion exchange system. Lime solids carryover and any solids accumulation from an upset are easily managed with the addition of airwash grids, which break up solids before backwash and regeneration.

Result:

The process has been highly efficient in delivering high quality water. 866-663-7633; www.kuritaamerica.com   

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System helps eliminate hydrogen sulfide odors at pump station

Problem

High hydrogen sulfide levels at the Forest Hills Pump Station in Pikeville, Kentucky, were creating a nuisance odor and a possible health risk. The station is at a major intersection and across the street from a high school and football stadium. Operators had tried various chemicals and other odor controls with limited success.

Solution

The operators tried a Phantom odor control system from Anue Water Technologies that uses sidestream wastewater to draw in concentrated oxygen and ozone. The aerated/ozonated stream is delivered back to the wet well through well washing systems, uniformly transferring the oxygen and ozone for FOG and odor/corrosion control. 

Result: 

The hydrogen sulfide levels dropped to 9 ppm after the first day of operation and to zero during the second day. 760-727-2683; www.anuewater.com