Deepening Treatment of the Low C/N Ratio Biogas Slurry at Mountainous Region Livestock Farming by Using Modified Two-Stage A/O System

The intensive and fast development of livestock farming with ecological pattern of raising-biogas-irrigating is widely applied in China. After anaerobic fermentation the agricultural wastes can provides clean energy. However, there is problem by lacking of land to digest the biogas slurry. Based on livestock wastewater from a dairy farming, the experiment used modified two-stage anoxic/oxic (A/O) system for biogas slurry with low chemical oxygen demand/total kjeldahl nitrogen (C/N)ratio. After anaerobic treatment, effluent is at the low C/N ratio of 1.7, and the proportion of nutrition is imbalance. Ammonia nitrogen (NH₃-N), total nitrogen (TN) and total phosphorus (TP), respectively are 225 mg/L, 255 mg/L and 19 mg/L. After cultivated and domesticated to activated sludge by increasing the proportion of biogas slurry gradually, the removal ratios of SS, COD_cr, NH₃-N, TN and TP are 90.7%, 90.7%, 92.3%, 76.4%, 84.0% respectively, and the performance is quite well. It will provide theoretical basis for livestock wastewater treatment.