Comparison between the performance of activated sludge and sequence batch reactor systems for dairy wastewater treatment under different operating conditions

Abstract

The main purpose of this study was to investigate the effect of operating conditions on the performance of two methods used for dairy wastewater treatment. First, conventional activated sludge (AS). Second, conventional sequencing batch reactor (SBR). On one side, the study included the comparison between the two basic systems. On the other side, it studied the influence of adding plastic media on both systems. The modified systems are known as biofilm conventional activated sludge (BAS) and biofilm sequencing batch reactor (BSBR). Four pilot-scale bioreactors, were operated in parallel under different conditions of temperature; 20, 35 and 45 °C. Synthetic dairy wastewater was used with characterizations of COD; 5000 mg/l, NH3-N; 250 mg/l and TP; 50 mg/l. The results recorded that the optimum temperature was 35 °C where removal efficiencies for COD were (93.52%, 96.63%, 94.74% and 97.79%), (89.01%, 91.14%, 90.45% and 93.22%) for NH3-N, and the concentration of NO3-N in effluents was (7.56 mg/l, 10.58 mg/l, 8.72 mg/l and 14.12 mg/l) for AS, BAS, SBR and BSBR respectively. At temperature equals to 45 °C; the oxygen consumption recorded the highest level of consumption, it was (1.07 mg/l, 1.64 mg/l, 0.98 mg/l and 1.23 mg/l) for AS, BAS, SBR and BSBR respectively. The results indicated that the sludge settleability was enhanced with the decrease of temperature. Furthermore GPS-X simulator was employed to predicting the performances of the biological systems under high COD concentrating reaching up to 17500 mg/l. GPS-X results indicated that SBR effluent could comply with Egyptian standard NO 2000. An overview, comparing with various treatment systems, it can be concluded that the SBR was the optimum treatment method for dairy wastewater based on the investigated conditions.