The Research On Removal Characteristic And Mechanism Of Organic Matter, Iron And Mangnese In The Drinking Water Resource By Biofiltration

On the basis of summarizing the related references home and abroad, a great deal of experiments had been done to study organic matter, iron and manganese removal characteristics and removal mechanism as well as removal kinetics by biofiltration in drinking water treatment. Results indicated the biofiltration could remove trace organic matter and chlorination disinfection by-products effectively. When water temperature was 8℃ and empty bed contact time (EBCT) was 6.75min, removal rates of BDOC and AOC in the GAC-sand biofilter were 65.0% and 84.2% respectively. When water temperature was 18~20℃ and EBCT was 13.5min, the removal rates of trichl-oromethane and dichloroacetic acid could reach 43% and 95% respectively. After the micro-polluted source water of Xiangjiang was treated by coagulation, sediment-tation and biofiltration, BDOC could be lowered to below 0.2 mg/L and AOC could be decreased to below 50|Ag/L. The removal of dissolved organic matter was strongly related to the molecular weight of organic matter. The removal rates of organic matter with small molecular weight (<1000) and with m olecular weight between 3000 and 6000 was 54.46% and 54.57% respectively. The removal rate of organic matter with molecular weight between 1000 and 3000 was 11.4%. The removal rate of organic matter with molecular weight between 30000 and 100000 was 36.0% .There was more than 69 varieties of synthetic organic matter which mainly consisted of hydrocarbon, benzoic acid esters, aliphatic acid esters and phenols in the influent of the biofilter. The molecular weights of these organic compounds were between 104 and 562. The GAC-sand biofilter could remove benzoic acid esters, aliphatic acid esters and phenols in the influent of the biofilter effectively. 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. The dominant bacterial genus and subdominant bacterial genus were Pseudomonas and Bacillus. The organic matter removal by microorganisms in the filters could be attributed to microbial metabolism, secondary utilization and microbial adsorption. Some factors such as filter media, EBCT, water temperature, backwash and filter closedown had some effect on organic matter removal. The filter whose media consisted of GAC and quartz sand could reach higher organic matter removal rate than the filter with anthracite or quartz sand.Backwashing with chlorinated water had negative effect on the biofilm obviously. The biological removal of manganese and iron could consist of three stages such as diffusion, adsorption and biological oxidation (regeneration). The removal rates of manganese and iron abided by first-order reaction kinetic respectively. The concentration of Mn2+ or Fe2+ in the filter was correlated with EBCT by the inverted exponential function. According to the function relationship, the concentration of Mn2+ or Fe2+ in any location along the filter depth could be predicted. When the influent pH was 6.6 and water temperature was 20℃, the kinetic constant of the biological manganese removal was 1.54mm-1 . When the influent pH was 5.8 and water temperature was 28℃, the kinetic constant of the biological iron removal was 0.98mm-1. The biological manganese removal could adapt the change of pH well. When pH was above 5, good manganese removal could be gotten and the manganese concentration of the effluent could remain steadily below 0.lmg/L. But if pH was less than 5, the manganese concentration of the effluent increased greatly. If there wasn't Fe2+ in the influent, efficient biological manganese removal would not occur. But too much Fe2+ (>0.75mg/L) could disturb the removal of Mn2+ in the biofilter obviously. Long time closedown of the filter only had a little impact on the biological manganese removal. Oxidation reduction potential (ORP) was correlated to the biological manganese removal inseparately. When the effluent ORP was in...