| In recent years biological aerated filter (BAF) is a new wastewater treatment technology that has been received more and more attentions for its advantages of less land use and high treatment efficiency. However, it is still with some problems such as easily being blocked and low phosphorus removal efficiency in operation. To solve these problems, a new kind of BAF, namely Baffled BAF (BBAF), was developed and studied in this paper, which includes: the hydrodynamic behavior of BBAF reactor; the effect of operational conditions on removal efficiencies of organic pollutants, suspended solids as well as nitrogen and phosphorus, development of a kind of chemical method appropriate to BBAF reactor using aerated filtration to enhance phosphorus removal and the corresponding mechanism, and the characteristics of biofilm by investigation into the biomass, biofilm activity and microorganism distribution in each BBAF compartment.Hydrodynamic behavior on BBAF proved to be relatively complicated flow combined by completely mixed flow in each stage while plug flow for the whole reactor along the horizontal direction. With a theoretical analysis, the hydrodynamic behavior of BBAF is helpful to full use of volume. Hydrodynamic behavior model of the each stage filter is as following:Hydrodynamic behavior model of BBAF is as following:Operation results indicated that BBAF reactor has a steady performance and good effluent quality. Flexible variation of influent quality has little effect on COD and BOD5. SS concentration of effluent showed that BBAF reactor has capacity to suit shock loadings. It was also found that a moderate change of hydraulic load affected COD and BOD5 removal efficiency slightly. TP, TN and ammonia removal efficiency dropped sharply with increase of hydraulic load. An excessive hydraulic load could result in anincrease of SS concentration of effluence. So, the appropriate hydraulic load was 17.4m3/m2.d. An increase of COD loading rate could cause a higher effluent COD and SS concentrations, but could influence little on COD and SS removal efficiency. The proper volume ratio of anaerobic to aerobic ranged from 1 : 6 to 1 : 3 in BBAF reactor with hydraulic loading of 17.4. It was also measured that the ratio of air to water for COD, BOD5 and ammonia removal was 10:1. Meanwhile, in the research, it was concluded that the zeolite media filter had a much better performance on ammonia removal than enzyme-promoted media filter. It was also observed that neither TP nor TN removal efficiency could be improved a lot with more small size media used in filter, while the ammonia removal efficiency achieved a distinct improvement.COD and SS concentrations decreased along the filtration length, especially in the first stage, which was so significant for COD and SS removal. COD concentration could decreased about 50% and SS could droped below 60mg/L after treatment by first stage filter. The decrease of organic pollutants and SS concentrations along the filtration length represented that the main function of 0~3.2m filter depth was area for organic pollutants removal and the aim of following depth was area for nitrification and denitrification. Model of BBAF for degradation of organic pollutants is as following:Analysis of influence of filtration length on organic pollutants removal efficiency with the model is consistent with experimental conclusion.TP removal was better than SP removal in BBAF. This demonstrated that the particulate phosphorus captured in filer contributed a lot to TP removal in BBAF, while biological assimilation could only play a small role on soluble phosphorus removal.The distribution of SS in BBAF represented the reactor had a large capability of pollutants, which could avoid quick block. The operation time was about 7-8 days. Stagewise backwashing with combined air and water applied in BBAF according to practical requirements could obtain a small water-consumption, less than 15% of the influent flow to BBAF system.A new chemical method (aerated filtration for phosphorus removal) was invented according to...
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