Application Research Of A~2/O-BAF Process In Rural Wastewater Treatment

With the development of rural economy and improvement of living standard in rural areas, the pollution of water environment in rural areas is rigorous caused by large quantities of wastes from industrial production, daily life, livestock farming and agricultural non-point source. The issue of water pollution in rural areas is becoming a matter of urgent concern. In recent years, the mixed discharge problem of industrial and domestic wastewater is serious along with the rapid development of livestock and poultry industry in Huangtan Town of Wengcheng Country, Wenzhou Ctiy, and then influence the downstream drinking water quality. According to wastewater characteristics of big variation of pollutants loading and high concentration of nitrogen and phosphorous in Huangtan town, a wastewater treatmen plant with the capacity of 2500t/d is established, and the effects of influent loading and operation parameters on the performance of A2/O-BAF process are studied. The main research results are as follows:1. The engineering was run under the condition of CODCr loading of 0.60 kg/m3.d, and the removal efficiencies of nitrogen and phosphorus were improved via the increase of ratios of sludge return and internal reflux in A2/O process. When the influent CODCr, nitrogen ammonia, TN concentrations were 678 mg/L,115 mg/L,140 mg/L, the effluent CODCr, nitrogen ammonia, TN concentrations were 91 mg/L,19 mg/L,42 mg/L under the condition of external reflux ratio of 160%, internal reflux ratio of 100%at the A2/O unit. The major index could not meet the 1st discharge standard of GB18918-2002.2. Under the condition of CODCr loading of 0.33 kg/m3.d, and influent CODcr, nitrogen ammonia, TN, TP concentrations of 363 mg/L,38.01mg/L,56.17mg/L,5.84mg/L, the removal efficiencies of nitrogen and phosphorus increased by the addition of 200-300 mg/L PAC at A2/O unit and methanol (70mg/L of equivalent CODcr as the carbon source for denitrification) at BAR The effluent CODCr nitrogen ammonia, TN, and TP concentrations were 42 mg/L, 1.63 mg/L,5.07 mg/L,0.41 mg/L, and the major effluent index could meet the 1st (A) discharge standard of GB 18918-2002.3. Under the condition of CODcr loading of 0.13 kg/m3.d, and influent CODcr, nitrogen ammonia, TN, TP concentrations of 131 mg/L,10.44 mg/L,12.35 mg/L,5.77 mg/L, the the removal efficiency of phosphorus was improved by the addition of 200-300 mg/L PAC at A2/O unit. The effluent CODcr, nitrogen ammonia, TN, and TP concentrations were 8mg/L,0.45 mg/L,7.97 mg/L,0.33 mg/L, and the major effluent index meets the related discharge standard.In summary, the A2/O-BAF process is suitable for the rural wastewate treatment with the big variation of pollutants loading and high concentration of nitrogen and phosphorous. The effluent quality is affected by ratios of sludge return and internal reflux, and available carbon source at A2/O unit. The removal of nitrogen and phosporus could be enhanced via the the addition of PAC at A2/O unit and methanol at BAR...