Pilot Study On Municiple Wastewater Treated By Biofilm-Actived Sludge Process

In order to improve the water quality of Shenzhen river and Buji river, Shenzhen government decided to reconstruct the Buji wastewater treatment plant. The original coagulation-flocculation-sedimentation process was reconstructed into the novel process of Enhanced biomembrane -actived sludge which was short HRT. This hybrid process is novel that we should make the pilot study to verify the operating effect before the reconstruction. This dissertation is about the pilot study of the novel process.Firstly, the biomembrane was cultivated, using the inoculation sludge to cultivate biomembrane on the static state, then on the dynamic state. After a week, the sludge in the reactor assumed the yellow brown, the milk yellow biomembrane grew on the carriers, from the microscope we found large quantities of protozoa and the metazoa in the water, which indicated the biomembrane had been matured. Then the influent water was based on the design inflow, the operation stage began.At the pilot study,the designed parameters are shown as follows: the inflow of water is 18m3/h, BOD-SS load of 0.15kg/kg.d ,DO is 2～4mg/L in the compound pond , pH value of 6.5～8.5, SV₃₀ is 100-120mL/2000mL. Gas water ratio of 6:1 to 10:1, the total HRT of the reactor is 3.5h.On the condition of description above ,after two months operation, the average COD removal was 80.37%, the average TP removal was 80.62%, the average SS removal was 90.52%, the average NH₃-N removal was 58.14%, the average TN removal was 44.78%,The effluent concentration of all the pollutants well meet the discharge standard 1B.Because the system can realize the separation of three "RT"s(BfRT, SRT and HRT) from each other ,by means of which sludge retention time(SRT)was separated from hydraulic retention time(HRT),and suspended sludge retention time(SRT)separated from attached biofilm retention time(BfRT) in the hybrid system, As a result, sludge retention time can be reduced properly to improve phosphorus removal without affecting nitrifiers growth in biofilm with much longer retention time that is beneficial to the growth and multiplication of nitrifers, which are helpful to nitrification and de-nitrification of nitrifers. Therefore, both high phosphorus and nitrogen removals can be achieved in the hybrid system.