Anaerobic digestion and post-treatment of swine wastewater using IC–SBR process with bypass of raw wastewater

A combined system consisting of Internal Circulation (IC) anaerobic reactor and Sequencing Batch Reactor (SBR) was used to treat swine wastewater in order to establish a cost-efficient wastewater treatment system. IC reactor could remove about 80% of COD with organic loading rate of 6–7 kg COD/(m3 day) in treating raw swine wastewater. Performance of direct post-treatment of digested swine wastewater was very poor with COD removal 7.54% and NH3-N removal 81.2% because of the low biodegradability and improper carbon/nitrogen ratio. Performance of post-treatment using SBR with the addition of raw wastewater was good with effluent COD less than 300 mg/L and effluent NH3-N less than 10 mg/L. The removal rates of COD, BOD5, NH3-N and TN were 95.5%, 99.6%, 99.4% and 94.3%, respectively, in the IC–SBR system with total hydraulic retention time of 5–6 days.