Study On Treatment Of Micro-polluted Source Water By Zeolite Biological Aerated Filter

As the raw water pollution is becoming increasingly serious, conventional water purification systems (CWPS) could not effectively remove some main pollutants in raw water,such as the dissolved organic matter, NH3-N , N02ˉ-N and so on. The safety of drinking water is under serious threat. In this paper, a biological aerated filter stuffed with activated zeolite was applied to pretreat micro-polluted raw water in Hangzhou. On the basis of the analysis about NH3-N adsorption properties by zeolite, experiments were carried out to discuss the starting and running performance of AZBAF, its removal characteristics for N and organics with different molecular weight as well as the distribution characteristics of biofacies on filter surface.Zeolite from Jinyun of Zhejiang province was modified by NaCl. Results showed when 15 g zeolite was modified in 100 mL NaCl solution ( mass ratio was 6% ) under room temperature, the obtained zeolite presented the best ammonia nitrogen adsorp ion property. Furthermore, activated zeolite was found to be suitable stuffing to fill the biological aerated filter due to its better porous structure and higher adsorption for N than natural zeolite and zeolite modified by NaCl.Owing to the zeolite adsorption property, AZBAF could start up quickly through the natural hanging film. Nitrobacterium and nitrosobacteria could tend to mature in 20 days. AZBAF showed fine removal capacity with around 95% of NH3-N, 25% of CODMn and 40% of TOC removed respectively during stable running. Measuring of the molecular weight of organic matter in inlet and out water showed more efficient degradation for organics of low molecular weight (<500Da)with the removal rate as high as 53.4% depended on biofilm, while interception, filtration and adsorption of stuffing for high molecular weight organics. AZBAF could be provided high resistance to Hydraulic (enhance to 2.45m3.m-2.h-1) and Ammonium (enhance to 2.7mg.L-1) shock loading. It made shutdown time had little effect to AZBAF by oligotrophic running and it could be recovered quickly in 24 hours even after shutdown for 35 days.According to the investigation into biofacies on filter surface, biomass in AZBAF decreased along the flow direction while an inverted"V"for the variation trend of biological activity. The biological activity per unit biomass increased with the distance from the intake, which was opposite to the distribution of biomass. Furthermore, the PCR-DGGE analysis showed rich microbial communities on zeolite and the above-mentioned trend for biomass could be obtained from it.