Performance evaluation of moving-bed Sequencing batch reactor for livestock wastewater treatment by SND process

In this study, the performance of moving-bed sequencing batch reactor with intermittent aeration strategy (IA-MBSBR) was evaluated for treatment of livestock wastewater in simultaneous nitrification-denitrification process. The statistical design and analysis were employed to optimize independent variables such as sludge retention time (SRT), temperature, and aeration rate using response surface methodology (RSM) through Box-Behnken design (BBD). The effect of variables was investigated on chemical oxygen demand (COD) removal and SND efficiency ( ). The analysis of variance (ANOVA) was conducted to confirm the suitability and significance of the quadratic models. Based on the results, a very high regression coefficient was achieved between the variables and the responses: COD removal and SND efficiency were R2 = 0.9788 and R2 = 0.9600, respectively indicating an excellent evaluation of experimental data by polynomial regression model. Long SRT reduced the negative effect of low temperature, but lowered COD removal and ESNDin high temperature. Further, appropriate aeration rate was vital for the SND to reach equilibrium between the nitrification and denitrification processes. The optimal conditions obtained from the models were SRT= 20 d, temperature = 19.16 °C and aeration rate= 0.1 , which results in COD removal and ESND of 92.9 and 91.3%, respectively. It was found that an alternating anaerobic/aerobic conditions with step-filling mode is an effective, economic, and environmentally-friendly strategy for the biological treatment of livestock wastewater in the moving-bed sequencing batch reactor.