The Research On Effect And Affecting Factors Of Biofiltration In The Micro-polluted Drinking-water Source

On the basis of summarizing the related references home and abroad, a great many of the experiments had been done to study removal results of organic matter, ammonia and turbility, influence factors and distribution trends of the biofilm in the drinking-water biofilters. The results of experiments indicated the biofiltration could remove organic matter, ammonia and turbility effectively. When water temperature was 7~9℃ and empty bed contact time (EBCT) was 6.75min, removal rates of TOC, COD and UV in the GAC-sand biofilter were 33.1%, 58.6% and 64.0% respectively. Under the conditions of the same water temperature and EBCT removal rate of ammonia was 71.8% when influent ammonia was 1.07 mg/L. Biofilters, the same as conventional filters, could produce the effluent with low turbility and has longer filtration cycle time.But water head loss of the biofilters was bigger than that of conventional filters with the same filter media, and had faster growth rate. In the biofilters different filter media had different biomass quantity, and the biomass quantity of the GAC media surface was obviously more than that of the anthracite or quartz sand media surface. The biomass in the biofilters decreased gradually from the top layer to the bottom layer along water flow direction, which coincided with the change trend of TOC concentration. The biofilm on the media surface mainly existed in the form of zoogloea. Some factors such as filter media, EBCT, water temperature, backwash and filter closedown had some effect on the results of the biofilters on organic matter removal. The filters with GAC and quartz sand media could reach higher organic matter removal rate than the filters with anthracite or quartz sand media. As water temperature or EBCT increased removal rates of the biofilters on organic matter increased. Backwashing with chlorinated water had negative effect on the biofilm obviously. Short-term shutdown of biological filters had little effect. Long-term shutdown had some effect, but could be restored in a few days after restarting the biofilters...