Optimization Study: Biological Removal of Inorganic Nitrogen along with Chemical Oxygen Demand from Wastewater Using Response Surface Methodology

Abstract

A comparative optimization study using response surface methodology (RSM) was carried out for biological removal of various inorganic N–NH3 sources (NH4OH, (NH4)2SO4, NH4NO3) along with chemical oxygen demand (COD; glucose: C6H12O6) from synthetic wastewater and consequently minimizing the N–N2O emission. Heterotrophic biomass conversion (HBC) process was used for wastewater treatment. Central composite design (CCD) method was used to optimize various experimental parameters using RSM. During the experiment biomass (total volatile suspended solids) was kept constant, while varying nitrogen and carbon concentration, respectively. Alkalinity consumption results in pH decrease during the HBC process. N–NH3 and COD depletion rates were higher in NH4OH in comparison to the other two nitrogen sources. Analyses of variance observed highly significant differences. Models obtained through CCD method were checked and tested via experiments and statistics. Having optimum value, i.e., 210 mg/L N–NH3, 2.90 g/L COD and 38 h; higher COD (94.1%) and N–NH3 (82.72%) removal was observed in (NH4)2SO4 and NH4OH. Higher desirability factor was obtained in NH4OH.