Analysis and evaluation of sewage discharge from large-scaled pig farms in Guangdong province

Ten large-scaled pig farms in Guangdong province were selected to monitor the pollutant contents in sewage discharged from the farms. The results showed that，concentrations of ammonia nitrogen（NH3-N）， total phosphorus（TP），CODCr，BOD5，total suspended solids（TSS）and fecal coliforms were 277.4-921.8 mg/L， 57.6-132.8 mg/L，677.4-5 046.9 mg/L，248.2-4 122.5 mg/L，374.8-3 290.3 mg/L and 75 420×104-3 961 610 ×104，respectively. Significant decreases of 10.9%-97.8%，33.4%-99.0%，75.4%-95.1%，25.6%-99.3%， 54.0%-97.3% and 55.7%-99.9% were observed for pollutants mentioned above as the piggery sewage treated with the sewage disposal systems. The discharge standard of pollutants for livestock and poultry breeding was used to evaluate the potential sewage contamination by nutrients，organic pollutants，TSS and fecal coliforms. The results indicated that fecal coliform bacteria exceeded the standard in most pig farm sewage，while NH3-N，TP，CODCr，BOD5 and TSS exceeded the standard in sewage mainly from the pig farms in Yuanzhou，Luoyang，Longxi and Changning towns. In summary，the sewage disposal systems performed well in purifying piggery sewage，however， several pollutants especially fecal coliforms in pig farm discharge exceeded the standard due to other exogenous pollutant sources