Influence of COD/ammonia ratio on simultaneous removal of NH4+-N and COD in surface water using moving bed batch reactor

The present study was carried out to investigate the influence of COD/ammonia ratio on simultaneous removal of nitrogen and carbon in the form of NH4+-N and COD. Cow dung slurry was taken as a source of microbial culture and acclimatized with dextrose and NH4Cl as carbon and nitrogen source. COD/ammonia ratio is important parameter in nitrification process and was varied from 2 to 10 (2, 4, 6, 8, 10) by concurrently varying influent COD (100-2500 mg/L) and NH4+-N concentration (50-250 mg/L). Results reveal that COD/ammonia ratio has a direct correlation with COD removal efficiency as when COD/ammonia ratio increased from 2 to 10, COD removal efficiency also increased from 80 to 98%. Maximum NH4+-N removal efficiency (99.4%) was obtained at low COD/ammonia ratio. At its maximum, the corresponding removal of NH4+-N and COD was obtained with COD/ammonia ratio of 2 and 48 h retention time (RT). Response surface methodology (RSM) using MATLAB software was used for the optimization of RT, COD/ammonia ratio, influent concentration of COD and NH4+-N. Response surface was generated in order to obtain the optimum value of each parameter in the nitrification process. The optimized parameters by RSM were obtained at COD/ammonia ratio of 4 with 41 h RT.