Brief Project Description
The new Middletown Wastewater Treatment Works is a dual train, hybrid attached /dispersed growth biological treatment facility capable of biological nitrogen removal and chemical-physical phosphorus removal. The design hydraulic capacity of the treatment facility is 400,000 GPD.
The main concrete tank (a combined/common wall structure including the biological unit, clarification, and sludge holding) is being constructed in a corner of the polishing cell of the existing aerated lagoon facility, for which a berm was created. A triplex pumping station, an influent flow meter, and a mechanically cleaned screen precede the biological treatment unit, and it is followed by an ultraviolet radiation unit for disinfection.
The “Bio-Wheel” system is a variant or hybrid of an attached/disbursed growth activated sludge process that combines mechanical simplicity with low intensity aeration and low energy requirements. The process consists of parallel rectangular tanks followed by rectangular (axial swept) clarifiers. Each process train consists of three transversely mounted rotating structures with cell plates arranged in a series of rows. The cell plates, which are 3/4” apart, have a roughened surface as a media for fixed film growth and also provide a source of aeration for the activated sludge. During rotation of the Bio-Wheel, trapped air is gradually released into the mixed liquor as fine bubble aeration. The rotational speed of the Bio-Wheel is adjustable, which regulates the amount of aeration and mixing in the bio-tank. The length of the Bio-Wheel unit is approximately 102 feet, which offers a substantially smaller footprint than most other activated sludge processes.
Nitrogen removal to an annual average concentration of 8.0 mg/l is achieved by a variation of the Modified Ludzack-Ettinger process. Nitrate rich mixed liquor is returned from the clarifiers and/or the terminus of the biological treatment tank to a covered pre anoxic tank.
Phosphorous removal to 1.0 mg/l by means of chemical precipitation is achieved by the addition of aluminum sulfate at the influent to the clarifiers.
The existing post aeration, flow measuring weir, and outfall line were retained in service.
A sludge dewatering building is being constructed integral with a covered aerated waste sludge holding tank. Sludge dewatering is by means of a rotary fan press.
Once the new treatment works are operating the existing aerated lagoons will be dewatered and closed in accordance with an approved closure plan