Design of discharge permit system of livestock and poultry breeding: a case study in Zhexi Reservoir Basin

As an effective environmental management instrument, the discharge permit system has certain restriction on pollutant discharge of point sources, especially of large-scale livestock and poultry breeding in the basin. The TN discharge from livestock and poultry breeding was studied in Zhexi Reservoir Basin. The water environmental capacity and the TN discharge load of livestock and poultry breeding were calculated on the small basin scale, and the response relationship between the environmental capacity of the river basin and the TN discharge of the livestock and poultry breeding determined according to the pollutant discharge contribution rates of different industries. The pollutant discharge limits and permit system program were identified according to the water environment capacity of large-scale livestock and poultry breeding for the basin, and the pollution control measures of livestock and poultry breeding under different environmental capacity targets were put forward.