Study On The Cross-flow Biofilter For Treatment Of Micropolluted Surface Water

Due to self-purification capacity deficiency, the artificial water bodies have no ability to maintain ecological balance, which cause serious eutrophication. Although sewage interception can fundamentally solve the problem of lake pollution, it is difficult to implement and the technology need costs a lot. So it is necessary to find a new process that is suitable for China and beneficial to solve lake pollution problem.In this research, the cross-flow biofilter process was discussed for treating micropolluted surface water. Fistly, the hydrodynamic behavior was observed by the method of the pulse stimulus response; Secondly, the natural set-up period was completed 60 days later during the conditions of hydraulic loading 0.08 m3/(m2·h),meanwhile, the removal rates of ammonia nitrogen and CODCr were about 90% and60%respectively; the influence of hydraulic loading on the nitrogen removal efficiency was researched by increasing hydraulic loading from 0.16 m3/(m2·h)to 0.80 m3/(m2·h);furthermore, comparing the nitrogen removal efficiency and the variation of biomass in two process of different influent direction, the mechanism of endogenous denitrification was studied. The results showed:(1)Tracer test showed short flow or circulation flow, and dimensionless variance was 0.34, which drawed a conclusion that the flow pattern was similar to pushing flow;(2)During the process of hydraulic loading from 0.16(m3/(m2·h) to 0.80(m3/(m2·h),the removal rates of ammonia nitrogen and CODCr had bigger fluctuation,compared with their removal rates in hydraulic loading hydraulic loading0.16(m3/(m2·h), ammonia nitrogen in 0.80 m3/(m2·h) decreases 12%,while CODCr increased by 6%, which showed that hydraulic loading hydraulic had great influence on theremoval rate of ammonia nitrogen and the biofilter had strong ability of anti-shock loading; meantime, the removal rates of nitrite nitrogen and nitrate nitrogen decreaded by 21%and less than 1%separatedly; TN removal was almost unchanged and turbidity removal efficiency was all over 90%;(3)During the process of forward influent direction, the removal rates of ammonia nitrogen 、nitrate nitrogen 、nitrite nitrogen、TN and CODCr was 67.55%、10.96%、63.92%、31.18%、67.55%; when the influent direction was reverse, their removal rates changed into 50.89%、27.22%、74.71%、35.10%、46.11%. In the whole operation process, the removal of CODCr mainly originated from mechanical interception and physical adsorption, while microbiological degradation was a little.From spectral analysis, humic acid was the main dissolved organic matter, and the removal effect of was similar in the two different process of influent direction. All of the above inferred that endogenous denitrification existed;(4) From analyzing the variation of biomass in the fist biofilter, the rate of endogenous denitrification increased gradually which could increase the removal rate of TN and ammonia nitrogen and p H.