Delaware County, Ohio
Due to Delaware County’s exceptionally high population growth rate, additional wastewater treatment facilities were needed, despite the 300 percent expansion to the Olentangy Environmental Control Center in 1995. The team of Burgess and Niple, Limited and Jones and Henry Engineers, Limited planned and designed this new facility which has a design capacity of 10 mgd (30 mgd peak capacity), a new tributary wastewater pumping station, associated force mains and sewers, and a new sewer system maintenance facility.
Preliminary treatment includes sewage screening with two, cylindrical fine screens and automatic screenings bagging for easy disposal. The pretreatment building also contains an odor control system which can remove odorous gas via chemical scrubbing or ventilation air discharged to the aeration tanks.
Six, three-pass aeration tanks are capable of multiple modes of operation and provide biological nitrification and denitrification. The aeration tanks contain a full floor coverage of fine bubble flexible diffusers and the first installation of low-speed submersible hyperboloid mixers in the United States. Foam/scum control as well as chemical phosphorous removal systems have also been incorporated.
Final settling includes four, 135-foot diameter clarifier tanks featuring innovative scum releasing feed wells, ducking scum skimmers, covered weirs to eliminate formation of algae, variable speed flocculation, and suction type scrapers.The tertiary filtration process includes eight lowhead traveling bridge filters and provisions for partial bypass.
Post treatment includes ultra violet (UV) disinfection and post aeration. The UV systemconsists of five channels each with 5 vertical modules and 40 lamps per module. Postaeration is provided via fine bubble flexible diffusers.
The solids handling facilities are able to produce Class "B" biosolids for land application. These facilities were designed for a potential retrofit to autothermal thermophilic aerobic digestion which can produce Class "A" sludge in the future. The waste activated sludge is thickened to 4 percent solids by a gravity belt thickener prior to digestion. Aerobic digestion is provided in covered, buried tanks with shear tube coarse bubble aeration. The digesters have a total volume of one million gallons. The biosolids are then thickened to six percent solids by a gravity belt thickener/belt filter press prior to storage. Sludge storage is provided in similar covered tanks and are able to be converted to digesters in the future. The storage tanks have a total volume of two million gallons. A covered bay is provided for trucks hauling stabilized sludge off-site.
The site layout and architectural design successfully blends the facility into the surrounding upscale residential community. This was accomplished architecturally through the use of the Frank Lloyd Wright "Prairie School" concept which stresses low profile structures, gentle roof slopes, and the use of premium quality residential looking building materials. The terraced site concept, architectural mounding, and extensive landscaping serves to conceal open tanks.
The electrical system includes a single feed loop to four transformers and two 1,250 kW diesel standby generators to handle critical loads during a power outage. The instrumentation and control systems provide for the continuous monitoring and control of the plant.
Plant effluent can be reused for many on-site operations including irrigation, heating and cooling, decorative fountains, foam/scum control, fire fighting, and plant wash down.
The Alum Creek Water Reclamation Facility received an Outstanding Achievement award from the American Council of Engineering Companies (ACEC) of Ohio. In addition, B&N’s project design manager received the Ohio Water Environment Association’s Engineering Excellence Award.