[Wastewater pollution characteristics from typical intensive pig farms in the Pearl River Delta and its ecological risk assessment].

Based on the wastewater quality investigation data from March 2009 to November 2011, wastewater qualities from typical intensive pig farms were assessed in the Pearl River Delta by single and comprehensive pollution index model. The results showed that key pollutants of piggery wastewater were fecal coliform (FC), total phosphorus (TP), chemical oxygen demand (COD) and biochemical oxygen demand (BOD), with their average mass concentrations of 1.98 x 10(9) CFU.L-1, 158.61 mg.L-1, 5 608.68 mg.L-1 and 1984.34 mg.L-1, respectively; key pollutants of biogas slurry were FC, TP, ammonia nitrogen (NH+4 -N) and suspended substance (SS), with their average mass concentrations of 8. 10 x 10(6) CFU.L-1, 81.76 mg.L-1, 476.24 mg.L-1 and 464.58 mg.L-1, respectively. Under the effect of wastewater pollutants, environment surrounding of typical intensive pig farms was seriously polluted, which decreased gradually from piggery wastewater to biogas slurry, and comprehensive pollution indices were 11.41, 6.91, 5.27, respectively. The risk analysis showed that the high-risk wastewater could never be discharged directly and irrigated crops. After the anaerobic treatment, FC, TP, NH+4 -N and SS were still strong factors with the potential ecological risk in the biogas slurry. In the long run, the ecological risk still exists for direct discharge or irrigation of them, and it is necessary to apply further treatment.