Research Of Nitrogen Removal Via Simultaneous Nitrification And Denitrification In Moving Bed Biofilm Reactor

In this paper, the moving bed biofilm reactor is established to research treatment effect with low COD/N wastewater by controlling the process operating parameters. The main purpose of this study is to build an efficient moving bed biofilm reactor, to enrich nitrifying bacteria and denitrifying bacteria, and to realize SND process in a single reactor. Based on the research of dynamic process, simulated the SND dynamic process in moving bed biofilm reactor when aerating, provided reference for the practical application of the technology; The analysis results for relative abundances of ammonia oxidizing bacteria demonstrated that the bacteria were enriched in biofilm by using FISH approach; Microbial community structure was examined by using DGGE; And discussed operating conditions of the reactor, so that it can be acquire the best denitrification effect.The main research contents are as follows:(1) K1type packing film was filled into the reactor with the rate of40%(v/v), COD and NH4+-N concentration of influent water was200mg-L-1and40mg-L-1respectively, DO was controlled between3-4mg·L-1. The biofilm was formed after20days, and80days later, the biofilm was fully mature. The average MLSS was0.0335g per packing film, the removal rate of COD, NH4+-N and TN was80.68%,97.25%and90.6%respectively, and SND rate can be arrived91.66%; It was indicated that microorganism enrichment condition was good in the biofilm, the reactor plays displayed high nitrogen removal efficiency, hanging membrane effect is better.(2)A kinetic model for SND was constituted on the basis of batch tests, and the simulation nitrate saturation coefficient KNO3(5.83mg·L-1) was higher than that in a single-sludge wastewater treatment system.(3) The EPS of polysaccharide and protein in activated sludge and biofilm were3.92mg-L-1,16.31mg-L-1and8.72mg-L-1,26.12mg-L"1respectively, indicating that biofilm growth stability.(4) DGGE profiles confirmed that nitrosation bacteria and nitrifying bacteria growth stability, denitrifying bacteria growth with the increase of the thickness of the biofilm during the cultivation of domestication of biofilm.(5) By discussing on the condition of different DO reactor operation, it is concluded that when the DO concentration between3-4mg-L’1, the reactor’s best denitrification effect, and total nitrogen removal rate up to83.46%, and the average removal rate is about80%. When the HRT of the reactor was controlled at12h, the reactor denitrification effect is good, the reactor effluent ammonia concentrations at20mg-L-1or less, obtained the total nitrogen removal efficiency of70-80%, it can up to87.47%. Keep the COD=400mg-L-1, when reactor with low ammonia nitrogen, the minimum effluent TN concentration was6.13mg/L, and this time the TN removal rate was higher. To observe the same COD/N in the operating condition of different load conditions, under the condition of low load, total nitrogen removal rate reached highest60.33%in the reactor (when COD/N=300,60).