Background: Low-cost anaerobic sequencing batch reactor (ASBR), which is widely used for controlling high-organic wastewater, is an effective method to remove chemical oxygen demand (COD).
Objectives: The main objectives was evaluating the feasibility of using ASBR in the treatment of synthetic dairy wastewater, determining its removal efficiency, and assessing the effect of temperature on operating conditions to remove the COD effectively.
Materials and Methods: The present study was conducted at a pilot scale system. Experiments were performed using a 20-L reactor and two storage tanks with the volume of 10 L. The effect of the variation of temperatures (20°C-35°C) and the effect of running cycles (10 runs) on the efficiency of COD removal by the ASBR process were investigated. Four heaters were used to produce the heat of the reactor. At first, raw wastewater in the primary tank was heated to the desirable temperature and then three more heaters continuously produce the heat in the reactor to operate system at the constant operating temperature in each run. Data were analyzed by SPSS 16through Pearson’s correlation coefficient to analyze the association between these parameters.
Results: The maximum COD removal rate was 89.7% at the organic loading of 4.5 g/L per day in a 24-hour cycle condition with reaction time of 21 hours and 30 minutes. The maximum biochemical oxygen demand (BOD5) removal rate was 91% and occurred at the first run. The amount of COD removal efficiency was higher at the first run in comparison to the third cycle (27.5%). BOD5 removal efficiency decreased up to 24.4% due to the drop of temperature in the reactor. Pearson correlation analysis showed a significant association between the temperature and the removal efficiencies (P < 0.01).
Conclusions: The results of this study indicated that any decrease in the temperature caused reduction in system efficiency of removing BOD5 and COD. Temperature of 35°C is optimal for the removal of high organic load wastewater. ASBR can be used as an effective tool to treat dairy industry wastewater.