Online measurement of oxygen uptake rates (OUR) in Biomass can be utilized to control activated sludge (or wastewater). Modeling showed that this novel control strategy ensured year-round compliancy to total nitrogen discharge limits, contrary to mixed liquor and solids retention time control. In a pilot-scale high-rate contact-stabilization system, control based on online OUR instead of MLSS or SRT, successfully correlated with COD oxidation. At a vOUR setpoint of 22-24 mg O2 L-1 h-1, OUR control maintained a solids retention time (SRT) of 0.4 ± 0.2 days while preserving excellent bioflocculation. Approximately 55% of the incoming chemical oxygen demand (COD) was redirected and incorporated into the particulate COD fraction. Of the redirected COD, two thirds (66 ± 23%) was captured, resulting in 36% of the incoming COD sent to the digester. Controlling wasting rates to maintain a setpoint vOUR is an alternate approach for high-rate activated sludge system management.
