Application of response surface methodology in optimization of process parameters for combined biological treatment of dairy wastewater using consortium of bacteria and microalgae

Abstract

This study was conducted to investigate the combined two‐stage biological‐treatment‐process using consortium of bacteria and microalgae for removal of soluble chemical oxygen demand (SCOD), ammonium‐nitrogen (NH4+‐N), nitrate‐nitrogen (NO3−‐N), phosphorus (PO43−‐P) from dairy wastewater in suspended‐growth batch‐reactor (SGBR). The study also investigated the removal of SCOD, NH4+‐N, NO3−‐N, PO43−‐P under different process parameters, like initial SCOD, NH4+‐N,NO3−‐N, PO43−‐P, MLSS, pH and react time using response surface methodology (RSM) with a five‐factor‐three‐level Central Composite Design(CCD). The experimental results were analyzed by ANOVA and second‐order polynomial mathematical‐models were developed with high correlation efficiency for SCOD, NH4+‐N removal, NO3−‐N, PO43−‐P removal using bacterial and microalgal‐consortia respectively in SGBR. Individual and combined effects of process variables on responses were studied using three‐dimensional response surface plots. Under the optimum conditions (initial SCOD, NH4+‐N, pH, MLSS of 720 mg L−1, 55 mg L−1 as N, 7 and 1500 mg L−1, respectively and react time of 24 h) highest removal efficiencies of SCOD (98.61%) and NH4+‐N (97.42%) were obtained using bacterial consortium and in second‐phase using micro‐algal consortium under optimum conditions highest removal efficiencies of nitrate nitrogen and phosphorus 98.64% and 90.53%, respectively. Optimization of process‐parameters by RSM study is supposed to be helpful for the treatment of real life dairy wastewater in effluent treatment plants.