Contaminant removal performances on domestic sewage using modified anoxic/anaerobic/oxic process and micro-electrolysis

Abstract

The objective of this study was to enhance removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic sewage in a sequencing batch reactor with added new materials. A modified anoxic/anaerobic/oxic (MAAO) process, integrating a micro-electrolysis (ME) bed in an anoxic tank, and complex biological media (CBM) in anoxic, anaerobic and oxic tanks to treat domestic sewage, and their performances were investigated. The MAAO system was operated at controlled hydraulic reTENTion time (HRT) of 8 h and mixed liquor recirculation (MLR) at 75%. The results showed that the MAAO system could effectively remove COD, TN and TP with average rates of 93%, 80% and 94%, respectively, in March, and 94%, 76% and 91%, respectively, in August. In this system, TP was primarily removed from the anoxic tank regardless of the operational conditions; removal contribution ratios to TP of the anoxic tank reached 56% both in March and August, indicating that the ME bed can effectively enhance phosphorus removal. TN was primarily removed from the anoxic and anaerobic tanks; removal contribution ratios to TN of anoxic and anaerobic tanks reached 36–38% and 37–38%, respectively. The oxic tank had the highest share of COD removal (56% both in March and August) in the removal of phosphorus. The outflow concentrations of COD, TN and TP were 3–46, 7–14 and 0.3–0.5 mg/L, respectively, in March, and 26–49, 9–15 and 0.04–0.1 mg/L, respectively, in August. COD and TN removal performances indicated that the innovative materials of the ME bed and CBM can effectively enhance COD and TN removal.