A WASTE-WATER TREATMENT SYSTEM FOR AN INDUSTRIALIZED PIG FARM

A demonstration wastewater treatment plant was built to treat the wastewater from a large, intensive farm with a standing pig population (spp) of 25,000 to establish design and operating parameters. The mean wastewater flow was around 500 cubic metres per day (30 l/spp.d) with a peak flow of around 700 cubic metres per day (35 l/spp.d). Treatment processes used during the study period included primary sedimentation, anaerobic digestion for settled solids and an anaerobic lagoon for the treatment of the settled raw wastewater and the discharge from the anaerobic digester. The steady state BOD and COD of the anaerobic lagoon were 1,520 and 3,630 mg/l respectively as compared to the mean BOD and COD respectively of 10,200 and 28,900 mg/l of the raw wastewater. Although close to 80% treatment efficiency was achieved further treatment was necessary to meet the effluent standard of 250 mg/l COD.