Experimental Studies On The Advanced Treatment Of Secondary Effluent By Different Combination Processes

The secondary effluent of municipal wastewater treatment plant is a stable quality, sustainable utilization of water resources, by advanced treatment and reuse,can alleviate the water shortage and water pollution problems. The experiment took the secondary effluent from biological treatment of municipal sewage plant in Harbin as the research object, by running small scale testing device, advanced treatment secondary effluent by using coagulation sedimentation filtration,coagulation sedimentation-BAF and ozone- biological activated carbon filter were studied. During stable operation, investigated and assessed the cutting force of pollutants in secondary effluent by different processes, and studied the treatment characteristics and advantages of each process.Coagulation-sedimentation-filtration as a conventional treatment process,widely applied to advanced treatment process of wastewater treatment plant in China. In the experiment studies, according to beaker test, determined the coagulants was PAC, and the optimal dose of PAC was 20 mg/L, and continuous running under this conditions. Analyzing operation effect and the results showed that the combined process could effectively remove phosphorus, the removal rate was 64%, to make up the phosphorus deficiency in secondary biochemical treatment.Due to the concentration of SS in secondary effluent was lower, the effluent SS increased after sedimentation, but decreased in sand filter, indicated that the removal of SS by this combination process was not obvious. The combined process had some effect on the removal of CODCr, UV254, and ammonia removal, the removal rate were 17%, 19% and 16%, but low TN removal. And the coagulating and sedimentation units played a major role in coagulating-sedimentation-filtration process, and the filter units could provide protection for discharge.The results of the experiment on the treatment of secondary effluent by coagulation sedimentation-biological aereated filter showed that the average removal rates of CODCr, UV254, ammonia nitrogen, TN and TP were 19%, 21%,40%, 11% and 55%, respectively, the average value of the effluent were 31.6mg/L,0.23cm-1, 0.49mg/L, 8.62mg/L and 0.22mg/L. While the average removal rates of CODCr, ammonia nitrogen, TN and TP by single-stage BAF were 14%, 49%, 3.5%and 3%. The removal of ammonia nitrogen by BAF and combined process were influenced by the ammonia nitrogen concentration of secondary effluent, the removal rate could be greatly improved when the ammonia concentration of secondary effluent increased.In the experiment on the treatment of secondary effluent by ozone andbiological activated carbon filter process, studied the characteristics of the secondary by ozone oxidation firstly, determined the optimum reactive time was20 min by analyzing data, in this case the content of ozone in water was 16mg/L.The running results showed that the removal effect of CODCr and UV254 by combined process was good, the average removal rate were 30% and 56%,respectively, and UV254 and chroma was mainly removed in ozone unit. The removals of TN and TP by combined process were not high, the removal of ammonia nitrogen was influenced by ozone and the ammonia nitrogen concentration of secondary effluent. In addition, studied the content distribution and variation of nitrogen in the effluent of process and each processing units.The secondary effluent and the effluent of combined processed were analysed by using fluorescence Excitation-Emission Matirx Spectroscopy, the results showed that all of the effluent mainly contained humic acid materials, the peak intensity of fluorescence decreased obviously in the ozonation of secondary effluent, and effluent of other processes were not obvious, demonstrated that ozone could effectively remove the humic acid organic matters in secondary effluent.Three kinds of combination process were run continuously at the same time,and comparing the removal efficiency of the pollutants from secondary effluent by combination processes. It was concluded that in the three process, ozone and biological activated carbon had stronger ability for the removal of organic matter,coagulation sedimentation-biological aerated filter had the advantage on the removal of ammonia nitrogen, nitrite nitrogen and phosphorus, and coagulation sedimentation filtration had highest removal efficiency for phosphorus, three kinds of combination processes had no significant removal for nitrate nitrogen,as well as could not effectively remove total nitrogen.