Optimization of Biological Elimination of Ammonia and Chemical Oxygen Demand from Wastewater Using Response Surface Methodology

Using a statistical technique, i.e. response surface methodology (RSM), optimization studies were carried out for different parameters like nitrogen ammonia (N‐NH3), chemical oxygen demand (COD) and time, to optimize overall method for maximum elimination of N‐NH3 and COD from synthetic waste water using heterotrophic biomass conversion (HBC) process, and simultaneously minimizing the N‐N2O emission. Ammonium hydroxide and glucose were used as nitrogen and carbon source. Central composite design technique was used to optimize the parameters with RSM. In this experiment, N‐NH3 and organic nutrient concentrations were varied keeping the biomass (total volatile suspended solids) concentration invariable. The pH during HBC process showed a decreasing trend may be due to consumption of alkalinity. Analyses of variance were carried out for quadratic model and were observed to be highly significant. The model was verified through experiments and tested statistically. Under optimized conditions (N‐NH3: 210 mg/L, COD: 2.90 g/L, time: 38 h) N‐NH3 and COD removal efficiency were observed to be 82.72 and 84.78%, respectively. N‐N2O emissions were minimized to 2.96 µg. The total desirability factor obtained was 0.9.