The Highspire Borough Authority’s wastewater treatment plant is designed to treat up to 2 mgd of wastewater. The current treatment process includes primary screening and grit removal, grinding or commutation, biological treatment for biochemical oxygen demand and nutrient removal, secondary clarification, anaerobic sludge digestion with biogas flared, centrifuge dewatering, and disinfection using UV light.

The Authority requested RETTEW review their biosolids processing train and provide recommendations for improvements in performance, cost, and reliability for treatment up to the plant’s full design capacity.

RETTEW conducted a feasibility study to assess the most appropriate sludge digestion process to meet Class B biosolids requirements. Processes evaluated included mesophilic and thermophilic digestion, co-digestion, as well as aerobic digestion. RETTEW also evaluated biosolids dewatering as the existing centrifuge was nearing the end of its useful life. We investigated various dewatering options including screw presses, belt presses, and centrifuges. RETTEW determined aerobic digestion is the most economically viable and robust sludge processing technology.