Enhanced treatment effect and universality of novel ARAO coupling process on municipal sewage: A pilot study

Under the impending demand of wastewater treatment plants (WWTPs) upgrading and reconstruction, it is feasible to propose a new process with low cost and high efficiency based on traditional process. Novel anaerobic-RBC-anoxic-oxic (ARAO) process was obtained after coupling traditional anaerobic-anoxic-oxic (A2/O) process with rotating biological contactor (RBC). Compared to traditional A2/O process, ARAO process has more efficient municipal wastewater treatment effect. Within 40 days of continuous operation, the average removal rates of COD, NH4+-N, TN and TP of sewage by ARAO process are 87%, 87%, 75% and 87%, respectively. The optimal operating conditions of ARAO process are the mixed liquor reflux ratio (MLRR) of 200%, the mixed liquor suspended solids (MLSS) of 3500–4500 mg/L, the dissolved oxygen (DO) concentration of 2–3 mg/L and the hydraulic retention time (HRT) of 6 h. The enhanced enzyme activity of ARAO process compared with A2O was determined through extracellular enzyme activity (EEA) and extracellular polymeric substances (EPS), and the microbial abundance and dominant species were further analyzed through high-throughput sequencing. The three-dimensional fluorescence measurement results showed a significant improvement in wastewater treatment efficiency. In addition, ARAO process has good adaptability to low temperature wastewater, low concentration wastewater and high concentration wastewater, which provides a good reference for the upgrading and reconstruction of WWTPs in the future.