Experimental Investigation On Municipal Wastewater Treatment By BAF Packed With Magnetic Biochar

Biological aerated filter(BAF), which integrates filtration and biological contact oxidation, can clarify sewage effectively. Since a filler is the core of BAF, developing an environmental-friendly biological filler which has high processing efficiency, superior performance, low cost and no secondary pollution is the major trend for future development. With the biochar prepared from the abandoned agricultural shells as the basic carrier, this study has prepared magnetic biochar fillers which can carry the product of heavy medal wastewater treatment, and analyzed its performance. The present study has also designed and constructed a BAF system. The experiment of biofilm colonization has been conducted to comparatively analyze the performance of ordinary biochar filler and magnetic biochar filler, as well as the reactor’ effect of simulated municipal wastewater treatment. In order to explore the operation parameters of pollutants removal effects on magnetic biochar filler BAF and determine the optimal combination of process parameters, the single factor experiment and the orthogonal experiment researches have been conducted in the biofilm reactor. The actual sewage treatment effect of ordinary biochar filler BAF and magnetic biochar filler BAF are comparatively analyzed and the characteristics of filler were also studied in this study. The main conclusions are as followings:1) The higher n(Fe2+)/n(M2+), the greater the saturation magnetic susceptibility. The difference of specific surface area between ordinary biochar and magnetic biochar is relatively small, indicating that loading magnetic ferrite has little effect on the specific surface area of biochar.(2)During the biofilm culturing, the biofilm rate of magnetic biochar filler BAF was higher than that of ordinary one. The magnetic biochar filler BAF only needs 13 days to form biofilm and the ordinary biochar BAF needs 15 days. The average removal efficiency of COD, NH4+-N, TP is 95.8%、90% and 77.6% by magnetic biochar filler BAF, meanwhile the average removal efficiency of COD, NH4+-N,TP is 92.7%、72.7% and 65.8% by ordinary biochar BAF during stable operation of biofilm culturing.(3)Single factor experiments shows that the HRT, DO, organic loading and filler filling ratio has significant impact on the removal efficiency of pollutants. The orthogonal experiments were tested by four factors with HRT, DO, organic loading and filler filling ratio, which shows that the magnetic biochar BAF can achieve the best removal efficiency when organic loading is 450mg/L, HRT 10 h, DO 3mg/L, and filler filling ratio 35%.(4) The study of actual domestic wastewater treatment experiments with two kinds of BAF finds that the removal effect of COD, NH4+-N, TP by magnetic biochar BAF is better than ordinary biochar BAF, which is consistent with the results of simulated wastewater treatment experiments. And the capacity of resisting impact load of magnetic biochar filler BAF is superior to that of ordinary biochar filler BAF.(5) Biofilm SEM analysis shows that the magnetic biochar filler and ordinary biochar filler all contains large amounts of bacteria, protozoa and metazoan, but the microbial numbers of magnetic biochar filler were significantly greater than the ordinary biochar filler. Based on two kinds of biofilm filler, dehydrogenase activity analysis shows that ferrite can increase the dehydrogenase activity of microorganism to a certain extent. With the increasing of ferrite saturation magnetic susceptibility, biofilm dehydrogenase activity doesn’t increase significantly.With the biochar prepared from the abandoned agricultural shells as the basic carrier, this study has prepared magnetic biochar fillers for BAF which not only can effectively solve the problem of agricultural wastes huddling and misplacing to fully utilize resource, but also process heavy metal wastewater effectively; magnetic biochar filler can form weak magnetic field around the filler without adding external magnetic field, improve the microbial metabolism, and accelerate the pollutants degradation rate. In addition, the magnetic biochar filler can be used again after simple treatment when abandoning. Therefore, the research is of great significance and the results will produce significant practical value.