Operation Characterstics And Backwash Optimization Research Of The Rapid Filter Under The New Standards For Drinking Water Quality

As new<Standards for Drinking Water Quality>(GB5749-2006) promulgateand implement, the quality of water treatment plant effluent need higher request, atthe same time, it is different for the filter s operation as usual. Particularly inturbidity, the new standard requires its less than1NTU in water supply. In order toinvestigation the characteristics of the filter in our country under the low turbidity,as well as the rapid sand filter s operation and backwash trait in cold region, so asto puts forward a universal backwash optimization scheme for filter, this paperwill research in views of the above argument.At first, we investigated38water treatment plants in most of our country,those plants representative different water source. The contents of thisinvestigation including as follows: filter type, filtration rate, filter runs, filter runsend type, backwash type, backwash rate and time, backwash drainage, theturbidity of influent and effluent, meanwhile, find out the problems duringoperation. The survey suggests: V-filter is one of the common type; filtration raterelatively low, the quartz sand used in single layer filter s rate usually is7~10m/h,and the double-layer with quartz sand/anthracite filter s rate always7~16m/h; thetypes terminate filter runs often simple. The backwash water rate is higher, and thewastewater reuse rate too lower.Secondly, under the new standard, we analyzed rapid filter operation andbackwash status in Z water treatment plant where in northeast cold region of China.Focus on the present filter runs, backwash rate and time, the average contain ofclay in filter material, drainage water quality, the initial filtrated water quality. Wecome to a conclusion: when the influent turbidity is less than1.5NTU, theturbidity removal rate is still higher after operation48h or72h. Furthermore, wecontrast the difference of filter condition before and after the standards p ublish,the result show that the water consumption rate in water works increased by3.65%,but the backwash water rate increased by0.59%only. After48h of operation, theaverage contain of clay in different depth are good, is between0.2%~0.4%. Thequartz sand has high removal efficiency in ammonium nitrogen. After backwash,all of the initial filtrated water quality is well.In the end, the optimal backwash time match for rapid filter is obtainedthrough orthogonal test. The test results are as follows: the greatest impact on headloss recover is time of water wash alone；the greatest impact on time which thedrain off water s NTU will drop to10NTU is air wash alone time and simultaneous air scouring and water wash time；the greatest impact on the initial30minutes turbidity of filtrated water is time of water wash alone；the greatestimpact on the ammonia nitrogen ratio is time of water wash alone；the greatestimpact on the UV254ratio is simultaneous air scouring and water wash time；thegreatest impact on the particle entrapment rate is air wash alone time；the greatestimpact on the capacity consume is simultaneous air scouring and water wash time.All in all, after analysis and contrast, the optimum time match for Z watertreatment plant of rapid sand filter is water wash alone3minutes, simultaneous airscouring and water wash1minute, air wash alone10minutes.