Adsorption-style high-rate activated sludge for carbon management and diversion

Abstract: The ability to obtain energy neutral operation is dependent on redirecting the organic carbon present in raw sewage to energy generating processes, like anaerobic digestion, in an energy- and cost-effective manner. This study evaluated the performance of an A-stage HRAS process as part of an A/B pilot project for this purpose. The high-rate operation of the A-stage (<1 day SRT, 30 min HRT, <1 mg/L DO) resulted in concentrating the influent COD to a waste solids stream with minimal energy input in a small footprint by maximizing sludge production (i.e., observed yield). At an average SRT of 0.15±0.05 days, the A-stage pilot averaged 45±12% COD removal with only 12±5% mineralization of the raw wastewater COD. The A-stage observed yield averaged 0.57±0.18 kg VSS/kg COD. This study demonstrated that the A-stage is capable of producing a carbon-rich waste stream representing almost 70% of the total sludge produced in an A/B that can be redirected to anaerobic digestion for energy recovery in the form of biogas.