| Water is a precious resource, the survival and development of human society could not do without it. But with the increase of the urban population, the ecological environment and the water pollution were worsening, and water resource was scarce. To solve this problem, urban wastewater resource had caused the attention of people. The urban wastewater was conducted to treatment depth. Because of this, we can realize the wastewater reuse, save water resource, alleviate the pressure of the city, ensure the water security, realize the sustainable development of water resource in our country.The secondary effluent of WWTP was chosen as raw water in this research. The combined process of advanced treatment was used to remove pollutant to meet the standard of the first level A criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB18918-2002). The process of denitrification biological filter-coagulation sedimentation-O3-biological sand filter was determined to conduct the secondary effluent.The denitrification filter used boring exposure and continuous water to select advantage bacterium group to form biological membrane attached on the surface of the filter material. In order to confirm this procedure successfully, the mark was that the COD removal rate reached to 50% and the NO3--N removal rate reached to 60%. It was showed that the ceramsite filter needed 25 d, and the polyethylene polyhedral hollow ring filter needed 30 d.After the stable operation, the denitrification effect of the two denitrification filters was studied with methanol, acetic acid sodium and glucose as carbon source. Results showed that when C/N>4.5 with methanol as carbon source, C/N>5.2 with sodium acetate as carbon source and C/N>11.6 with adding glucose, the nitrate removal efficiency was more than 95% in ceramsite filter. When C/N>5.5 with methanol as carbon source, C/N>6.7 with sodium acetate as carbon source and C/N>14.1 with adding glucose, the nitrate removal efficiency was more than 90% in polyethylene polyhedral hollow ring filter. Moreover, the effluent TN concentration of two filters was below 15mg/L, meeting the first level A criteria. From the operation effect and practicality, sodium acetate was more suitable in the actual production.With ceramsite filter as an example, within the scope of 0~400mm of the filter packing on the pollutants removal was best through analysis and comparison.In addition, the effects of the temperature and the influent COD concentration on the denitrification reaction were studied. The results showed that the denitrification effect was better under 28℃ and the ceramsite filter was better than the polyethylene polyhedral hollow ring filter. When the COD loading was 78.9mg/L, the TN removal rate of ceramsite filter increased to 82.12% and it was the best. When the COD loading increased to 82.49mg/L, the TN removal rate of the polyethylene polyhedral hollow ring filter was 80.45% and it was the best. So ceramsite was more suitable for the packing of denitrification filter.In this test, Polyaluminium Chloride(PAC) was chosen as coagulant. When the dosage of coagulant was 60mg/L, The coagulation precipitation on the removal effect of the secondary influent achieved the best performance.The start-up and operation characteristics of biological sand filter were studied in this test, and the mark of the membrane forming was that the NH4+-N removal rate reached to 70%. It was showed that the biological sand filter needed 24 d.The optimal dosing quantity of ozone was 3mg/L by analyzing the NH4+-N, CODCr, UV254 removal effect of the process of O3-biological sand filter.Except that, the effect of the NH4+-N initial concentration on the process was studied. When the NH4+-N concentration of the influent was 8.864mg/L, the NH4+-N removal rate of biological sand filter reached to the highest.Finally, the denitrification effect on secondary effluent of the denitrification biological filter-coagulation sedimentation-O3-biological sand filter was mainly studied in normal operation condition by the analysis of NO3--N, NH4+-N, TN removal effect. The results found that TN was mainly removed by the denitrification filter. |
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