Experimental Study On Urban Landscape Purifying Of Bio-filter Circulating Process

The experimental study on urban landscape purifying by bio-filter circulating process was made in this paper, using the lake water of Handan as the source water. The pollutants removal effect by bio-filters of different filter medias was investigated, and the best filter media and filling height of the bio-filter circulating process were determined. The influence of water temperature and hydraulic loading on pollutants removal effect were studied, and the best operating parameter of the process was determined. Organic matter degradation kinetic model of bio-filter was derived. Decontamination effect of bio-filter circulating process was syudied when operated steadily.The Down-flow bio-filter was used to purify urban landscape, and ceramsite, two different particle sizes activated carbon and quartz were used as filter medias. The results demonstrate that activated carbon filters had a better removal efficiency to CODMn, NH4+-N, TN and turbidity, and the purification efficiency by small particle filter was heigher than large one. The average removal rates of CODMn, NH4+-N, TN and turbidity by small particle activated carbon filter were36.82%,84.59%,10.81%and84.78%, respectively. The removal efficiency of turbidity by quartz sand filters was heigher than activated carbon filter and ceramsite filter, and the removal efficiency of small particle was better than the large one. The average removal rates of CODMn, NH4+-N, TN and turbidity by small particle quartz sand filter were32.44%,78.23%,8.49%and87.97%, respectively. For the large particle diameter, ceramsite filter had lower turbidity removal, and the average removal rates of CODMn, NH4+-N, TN and turbidity were35.79%,80.09%,9.69%and75.71%, respectively.The pollutants removal effect by bio-filter circulating process was investigated under the filling height of0.2m,0.4m,0.6m and0.8m of the2rd bio-filter. It was in the filling height of0.4m,0.6m,0.6and0.2m that the process could get better removal effects of CODMn, NH4+-N, TN and turbidity when process running a cycle, which were30.33%,66.83%,4.79%and71.55%, respectively.The influence of water temperature and hydraulic loading on removal effect of CODMn, NH4+-N, TN and turbidity were analyzed. When the water temperature was high and the hydraulic loading was5m3/(m2·h), the bio-filter circulating process could get a good removal effect.Organic matter degradation kinetic model was S=S0e-Kh. The relation equation about organic matter degradation kinetic constants(K) and hydraulic load(q) was K=-0.084q+0.9073,(R2=0.9921). The verification revealed that the maximum absolute error and the maximum relative error were0.32mg/L and7.21%between the theoretical calculating value and the experimental value.The activated carbon bio-filter filter (2nd) was used to treat the lake water, and the purification effect of the bio-filter circulating process was studied when the water temperature was22.1-27.3℃, hydraulic load was5m3/(m2-h) and air-water ratio was2:1. The water quality of raw water and recycled water were tested when the process was on the run of Cycle One, Cycle Two and Cycle Three. The average removal rates of CODMn waere38.86%,76.74%and85.92%, of NH4+-N were38.86%,76.74%and85.92%, of TN were6.45%,9.68%and11.29%, of turbidity were57.5%,83.75%and87.5%, respectively.