Ohio Wastewater Treatment Plant Installs Covers On Sludge Digester Tanks

Aug. 13, 2011

Attempting to maintain aerobic conditions in two large, municipal thickened sludge digesters created problems in an Ohio community. High aeration rates caused splashing out of the digesters, while lowering the aeration rates to reduce the splashing created additional odors.

Twenty miles north of Columbus, Ohio is the lovely community of Powell, Ohio. Located in the southern tier of Delaware County — Ohio’s fastest growing county and recognized as one of the most rapidly growing counties in the nation — Powell is experiencing double-digit growth with dozens of homes under construction in any given month, and new businesses and retail shops springing up throughout the area.

Serving this dynamic growth is the Olentangy Environmental Control Center, a six million-gallon per day tertiary treatment wastewater plant employing biological nutrient removal with aerobic sludge digestion.

Bounded by the Olentangy River, a metro park, a scenic byway road as well as high-end housing, this facility is the daily focus of many neighboring eyes and noses.

As part of its "Good Neighbor" effort, the Olentangy facility features low profile buildings, ponds and landscaping. However, attempting to maintain aerobic conditions in the two 16 ft. x 85 ft. and one 18 ft. x 85 ft. thickened sludge (6%) digesters created problems. High aeration rates caused splashing out of the digesters — a housekeeping nightmare — while lowering the aeration rates to reduce the splashing created additional odors.

To address this issue, the Delaware County Board of Commissioners issued in April of 1999 a solicitation to procure covers for these tanks. Cover selection criteria in this solicitation included:

• Total and long-term containment of odor emissions,

• Minimize the visual impact of the covers,

• Install covers without removing the existing handrails.

After a thorough evaluation of all cover options, ILC Dover’s Vapor Guard® covers were awarded a turnkey contract for the design, engineering, manufacture and installation of the digester covers in September of 1999. "ILC Dover had the product to fit our need," said operations manager Paul Sandstrom.

Key to this award was Vapor Guard’s performance on each of the selection criteria:

• Vapor Guard’s heat-sealed seams ensure total and long-term containment of odor emissions;

• Vapor Guard’s flat profile and tan color minimize the visual impact of the covers;

• Vapor Guard’s support structure included custom fabricated "knee braces" to discreetly reinforce the cantilevered walkways and to permit installation of the covers without removal of the existing handrails. Further, Vapor Guard’s modular panels were laser-cut at the factory to ensure a tight fit with the existing handrails.

Installation of the Vapor Guard covers was completed in March of 2000. The covers have enabled the previous high aeration rates to be maintained and presently, additional odor control devices are not needed. Further, an added benefit of the covers is the warmer temperatures maintained in the tanks — especially helpful during Ohio’s winter season.

For further information, phone ILC Dover, Inc. at 800-631-9567, FAX 302-335-1320, email [email protected].

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