Study On Co-processing Municipal Sewage And Organic Wastewater With High Concentration Of Salt And Nitrogen

Pickle producing is the characteristic and pillar industry of the Three Gorges, but the waste water treatment rate of the pickle enterprises all over the Three Gorges is less than 1 percent, and the effluent can't reach drainage standard with the restricted factor of the less of treatment technology for pickle wastewater with high efficiency and low cost. The results of the earlier experimental research and theoretical analysis showed that anaerobic treatment and then co-processing with domestic wastewater was an advisable technique line for the pickle wastewater treatment. However, there were two technical bottleneck during the co-processing after anaerobic treatment of pickle wastewater: the first was to decide the limited salinity and doping amounts of pickle comprehensive wastewater in result that the effluent of the domestic wastewater treatment system could meet the discharging standard; the second was to decide operating ways and the parameters for biological nitrogen removal of the mixed wastewater when the effluent drained into municipal pipes which contained low carbon and high nitrogen after the pickle wastewater reached the third class criteria of Integrated Wastewater Discharge Standard by anaerobic treatment. Therefore, the research was carried out on co-processing organic wastewater with high concentration of salt and nitrogen and municipal sewage by the process pilot-scale experiment. The research contents and main results were as the follows:â‘ By the method of gradually increasing salinity to train salt tolerance of microorganisms in the sludge, the test study was carried out to discuss the effect of salinity on the removal of organics. The experimental results indicated that when the salinity was 5000mg/L, COD concentration in effluent was about 30 mg/L; when the salinity was 10000mg/L, COD concentration in effluent was about 50 mg/L; when the salinity was 15000mg/L, COD concentration in effluent was about 70 mg/L. Compared with the first B class discharge standard of urban sewage treatment factory(GB18918-2002)( here in after referred to as"the first B class standard"), the data of the COD concentrations in effluent showed that the suitable salinity was 10000mg/L during processing organic wastewater with high concentration of salt.â‘¡The experiment was carried out to discuss the effect of salinity on the removal of the main pollutants co-processing pickle wastewater and domestic sewage by CASS process. The results indicated that when the salinity of mixed wastewater was 1500mg/L, 2000mg/L, 2500mg/L, 3500mg/L and 4500mg/L, respectively, the concentrations of COD, NH₄⁺-N, and SS in effluent could reach the first B class standard, but the limited indicator was TN, and it's thought by analysis that the lack of silicon source was the main influential factor for the low nitrogen removal efficiency.â‘¢The experiment was carried out to discuss the effect of C/N ratios and operation conditions on treating domestic sewage by CASS process according that the concentrations of TN could reach the first B class standard. The results indicated that the optimal operation condition of the CASS reactor was when drainage ratio was 50%, operating time was 8.5h and C/N ratio was 5:1 by adding methanol as carbon source.â‘£The experiment was carried out to discuss the effect of the doping amounts for pickle wastewater on co-processing pickle wastewater and municipal sewage by CASS process. The results indicated that when operating the reactor under the optimal operation condition that drainage ratio was 50%, operating time was 8.5h and C/N ratio was 5:1, in case of 5% doping amounts for pickle wastewater, the concentrations of COD, NH₄⁺-N, SS and TN in effluent could all reach the first B class standard; in case of 10% doping amounts for pickle wastewater, the concentrations of COD, NH₄⁺-N, and SS in effluent could reach the first B class standard without TN. Therefore, the advised doping ratio for pickle wastewater was 5% when co-processing pickle wastewater and municipal sewage by CASS process.By the CASS process pilot-scale experiment of co-processing organic wastewater with high concentration of salt and nitrogen and municipal sewage, the limited salinity and doping amounts pickle comprehensive wastewater were worked out in result that the effluent of the domestic wastewater treatment system could meet the discharging standard, and the optimal operation condition of the CASS process was found, which would provide the theoretical bases and technique data for the practical application of the system and the spread and application of the process of great practical significance.