Effects of anaerobic fermentation on reducing organic pollutants in sewage of large-scaled pig farms

Anaerobic fermentation technology is widely used to treat piggery sewage. 10 large-scaled pig farms were selected and the organic pollutants in sewage from hoggery and newlybuilt methane tank were monitored dynamically. The value of CODCr and BOD5 in hoggery sewage ranged from 1057.6 to 3873.7 mg/L and 1847.8 to 5515.4 mg/L，respectively. In sewage discharged from the methane tank，value of CODCr and BOD5 ranged from 266.7 to 1 420.4 mg/L and 534.4 to 2 490.2 mg/L，respectively. The value of CODCr and BOD5 in hoggery sewage reduced 63.33%-90.09% and 54.82%-87.06%，respectively，as treated by anaerobic fermentation system. The ratio of BOD5/CODCr in sewage of methane tank was 0.53-0.71，which facilitated the subsequent aerobic treatments. Sewage discharged from the methane tank received further treatment by the fish pond and oxidation pond and then discharged out of the pig farm. The concentrations of COD and BOD in effluent of pig farm increased significantly compared to that in effluent of methane tank. Among the 10 pig farms，contents of COD and BOD in the effluent of nine pig farms met the value of the discharge standard of pollutants for livestock and poultry breeding，which did not pose any pollution potential on surrounding environment.