A-stage and high-rate contact-stabilization performance comparison for carbon and nutrient redirection from high-strength municipal wastewater

This study performed a parallel comparison of the A-stage (adsorption) and high-rate contact-stabilization (CS) technology for carbon and nutrient redirection, operating both systems at similar sludge retention time (SRT) of 0.16-0.3 d and treating high-strength raw wastewater. Overall at the average 0.22 d SRT condition, both A-stage and CS had similar carbon capture behavior (42-43%) and thus the similar potential for energy recovery. However, the A-stage had better effluent quality (67 mg VSS/L) through the growth of more heterotrophic biomass leading to increased oxidation (22% vs 18%), and increased fraction of nitrogen (26% vs 19%) and phosphorous (36% vs 30%) redirection compared to the CS. At biomass limited conditions and at lower SRT, CS maintained better performance, potentially through a better extracellular polymeric substance management under feast-famine conditions. Full-scale plant energy calculations based on this study results showed that chemically enhanced primary treatment (CEPT), A-stage, CS, primary treatment + CS and CEPT + CS could all lead to energy neutral plants as enough carbon can be redirected to generate the energy needed to support wastewater treatment. Given the superior performance of CS under lower loading or SRT limitation, the best energy gain (200%) could be potentially reached with a combination of CEPT and CS in series to enhance carbon capture up to 68% in combination with mainstream deammonification.