Pilot-scale Study Of Treatment Efficiecny Of BAF In The Augmentation Treatment Of Secondary Effluent

Severe quality standards has been published which forced sewage treatment plants to upgrade. Biological aerated filter is a reactor having double functions,including biofilm and activated sludge,which has better application prospect in secondary treatment of urban sewage.Treatment of secondary effluent from a wastewater treatment plant by biological aerated filter was discussed in this paper. Ten bacterial strains obtained from the wastewater by separating and domesticating were used to treatment wastewater experimental of Single strain; the removal efficiency of COD and total nitrogen were studied to obtain the dominant bacteria: Q1,Q5,L4,ZW which were then used in composite stabilizer test. Study result showed that the suitable start-up conditions were Q1:ZW as the percentage of 1:1.Pilot scale text model was established in TaiPing wastewater treatment plant to grope the practical running parameters of BAF. Experiments on start-up forms demonstrated that the way of artifical adding bacteria was better tha natrual enrichment both on start-up time and on the subsequent treatment effect. The biological aerated filter was successfully started up within 9 days. The suggested conditions for wastewater treatment by BAF were: heights1.5m-1.8m, hydraulic loading1.25 m3/m2·h, water flow 22.12 L/h , HRT 0.54h,gas-water ratio10:1 under which the effect was the best. During the process, a simple and periodic backwash was used to regenerate the used BAF, with gas rate 8-10 L/(m2·s),water rate 2-3 L/(m2·s) and back washing time 11min.The capability of regenerated BAF was recovered almost completely after reprocess.The mechanism of biofilm forming were investigated and it was found that interception and adsorption closely lined with biofilm forming. Also diversity and activity of microbial community of BAF were examined and the succession rule of indigenous microorganisms was analyzed; How microbial community structure changed along different heights were discussed. These studies have not only developed the theory of biological aerated filter in some extent, but also will provide a foundation for the application of BAF to water deep treatment.