Study On Production And Application Problem Of Biological Sand Filter In Treating Micro-polluted Water

The production and application problems of biological sand filter in treating micro-polluted water were studied in this paper,using the Fuyang River as source water. Based on operational character of biological sand filter,the removal effect of contaminations and the operational performance of filters were studied under various biofilm formation methods. It was investigated biological sand filter improve the biological stability and health safety of drinking water through pilot-plant experiments. The optimal operation parameters for air-water backwashing in biological sand filter were determined through orthogonal experiment. The removal organic matters,NH₄⁺-N were studied and the biomass and biological activity in filter were analyzed at law temperature. It applied Hierarchical process diagnosis analysis for analyzing influencing factors.The results demonstrate that compared with the nature biofilm formation,the start-up time of inoculated biofilm formation is shorter 6 to 8d. The different column filters can remove CODMn,DOC,SCOD,NH₄⁺-N,NO₂^--N,Fe,Mn and turbidity effectively at average removal rates of 34.55%,44.13%,51.07%,83.79%,77.71%,75.50%,79.89% and 62.95%,respectively. The natural biofilm formation method has more efficient pollutants removal than the inoculated biofilm formation method. In particular,the UV₂₅₄ removal rate and operation period of the former are 6.22% and 4 to 8h more than that of the latter. The operation is more stable.Using the turbidity of discharged backwashing water,the change rate of biomass and biological activity in biological sand filter before and after backwashing as evaluation indexes,the optimal operation parameters for air-water backwashing in biological sand filter were determined through orthogonal experiment and intuitive analysis. The results show that the biomass is reduced by 5.43% to 23.18%,and the biological activity is enhanced by 10.53% to 34.48% in biological sand filter after backwashing compared with that before backwashing. The optimal operation parameters are determined as follows: the single air backwashing intensity,single water backwashing intensity,combined backwashing intensity are 10L/m²Â·s,8L/m²Â·s and 4L/m²Â·s respectively,the single backwashing time,single water backwashing time and combined backwash time are 2min,4min and 5min respectively. The air backwashing intensity is the important factor influencing backwashing efficiency of the filter.The biological sand filter can remove Pb,Cr and UV₂₅₄ effectively. The removal rates of Pb,Cr and UV₂₅₄ are 67.85% to 78.45%,59.09% to 72.73%and 19.47% to 34.74%,respectively. The influence factors such as temperature and filter velocity are analyzed for removing UV₂₅₄. It also investigates the relationship between inflow UV₂₅₄ and effluent turbidity. The correlation of DOC and UV₂₅₄ is studied,the relational expression is y = 0.025 x+ 0.0543, R² = 0.8838. The average removal rates of BDOC and TP are 61.05% and 65.35% in biological sand filter.The removal rates NH₄⁺-N,CODMn are 51.31% to 66.35% and 9.18% to 12.36% separately in biological sand filter at 5.2℃to 10.2℃. Biofilm activity is 0.029～0.067 mgO₂ /h·g and lower 45.53% than at normal temperature. It applies Hierarchical process diagnosis analysis for analyzing influencing factors. The results show that the temperature,filter velocity and substrate concentration are the important factors. Their weights are 0.318,0.270,0.118,respectively.