Optimising nutrient removal of a hybrid five-stage Bardenpho and moving bed biofilm reactor process using response surface methodology

Abstract

Nutrient pollution has become a global environmental issue. Innovative biological nutrient removal (BNR) processes are needed to overcome the drawbacks of conventional technologies. This study evaluates the potential of a hybrid 5-stage Bardenpho - moving bed biofilm reactor (MBBR) process for organic carbon and nutrient removal from municipal wastewater at different hydraulic retention time (HRT) and nitrate recycle ratio (R). Response surface methodology (RSM) based on a central composite design (CCD) of thirteen experiments was applied to optimize the nitrogen and phosphorus conversion of the treatment system. High removal efficiencies of about 98.20%, 92.54%, 94.70% and 96.50% for total chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and ammonium, were achieved, respectively. The best performance was observed at HRT of 2, 4, 6, 2.67 and 1.07 h correspondingly in the anaerobic, first anoxic, first aerobic, second anoxic and second aerobic compartments, resulting in a total HRT of 15.74 h with a nitrate recycle ratio of 2. Biofilm nitrifying activity was four times higher than in suspended biomass. The hybrid 5-stage Bardenpho-MBBR process enhanced biological nutrient removal at comparatively short HRT and low R ratio due to biofilm contribution to the conversion.