Research On Distribution And Electron Metabolism Character Of Organic Compounds During The Sewage Denitrification

Generally, the effluent of urban sewage treatment plant remains soluble microbial products which come from the biological treatment processes. These products will not only make the effluent can not reach the standards, but also carry some precursors of carcin-ogens. So this paper researched the formation, distribution and the biodegradability of SMP during the denitrification process, and discussed the influence of different factors to the SMP molecular weight distribution.The results show that:(1)In conventional denitrification process, the concentration of SMP increase with the reaction time runing. In the early stage of the reaction(0-20min),the rate of denitrification is fast. In5min, it increases to33.99mg/(gMLSS·h).The growth rate of SMP is fastest which is6.42mgTOC/(h·L) in the average and the accumulation of SMP accounts for79.57%of the total.In the middle of the reaction(20-180min),the growth rate of SMP is low and the accumulation only accounts for6.18%.When it comes to the end,the growth rate of SMP is0.60mgTOC/(h·L) and the accumulation accounts for14.25%.(2)When the reaction is going to20minutes, the SMP mainly distribute in the range of300-1000D and3000-5000D, and the sum of the two intervals accounts for approximately53%of total SMP. When the reaction is going to6o minutes,90minutes and120minutes, the trends of SMP’s molecular weight distrubution are almost the same, and the shape looks like a "W". When the reaction is going to180minutes and240minutes, the SMP mainly distribute in the range of lw-80wD, and the concentration in this range accounts for approximately40%of the total SMP. The molecular weight distribution of SMP are mainly affected by the matrix metabolism and endogenous respiration. SMP distributed in0-1000D are mainly come from the metabolism of microorganisms and SMP distributed in lw-450wD are mainly come from endogenous microbial respiration.(3)C/N has little effect on the molecular weight distribution regularity of SMP, however the growing of C/N can lead to the increasement of SMP concentration and TN removal efficiency.(4)The changement of initial electron acceptor will alter the concentration and molecular weight distrib-ution of SMP, especially to the SMP distributed between3000D and5000D.(5)Mixing intensity affects TN removal and the molecular weight distribution of SMP, either too high or too low will bring down the effluent water quality. On the condition of low mixing intensity, the concentration of SMP is low. On the condition of high mixing intensity, the SMP distributed between10wD and450wD have a substantial accumulation.(6)Most of the SMP(Mw<1wD) can be used in the denitrification.The SMP in the Mw range of1w-80wD can also be used by microbes in some degree, however its degradation rate is slower. In the denitrification process SMP (Mw>80wD) have a fairly slow degradation rate,ever hardly can be degraded..