| With the continuous attention of the water environment quality,the stricter standards.have been made to the municipal sewage treatment plant effluent quality.The TN and TP value asked in the first level A are remarkable higher than the water eutrophication critical value.The research we have done on site aims at the situation of the secondary effluent unbalanced C/N ratio and the high dephosphorization cost,and designs an up-flow biofilter with the simultaneously advanced nitrogen and phosphorus removal based on sulfur autotrophic denitrification?SDN?and chemical dephosphorization.Comparing to the heterotrophic denitrification?DN?biofilter,SDN successively and researching their advanced treatment efficiency.Engineering application feasibility and economic cost were analysed at last.We also made a preliminary exploration on the advanced treatment by using sulfur-iron tailings mixed packing.We can get the following main conclusions:The SDN filter started up successfully by using the sludge inoculation and the mature packing inoculation respectively and without the help of technical microbial inoculum.The start-up completed respectively in the 13th and 15th days in turn,and the start-up procedure was slower than the DN filter`s.The advanced denitrification is realized by using SDN filter.At HRT1.4h,the effluent TN was less than 5 mg/L,and the effect was equal to the DN adding 80100 mg/LCOD under same HRT.The average removal was 16 mg/L NO3--N.There was not NO2--N accumulation detected in the stable SDN effluent,while it was detected in DN`s and relatively high at average of 2.54 mg/L.The head loss growth rate of SDN is obviously lower than that of DN,and the water quality is stable and reliable,which significantly reduces the SDN backwashing frequency,but refer to the DN`s backwashing method,the SDN recovery phase is slightly longer than that of DN,the loss of sulfur particles during the SDN backwashing is serious,so the DN backwashing method can`t be copied directly to SDN,reference to the backwashing experiences got in research,the recommended method was“low gas washing intensity-low gas washing intensity joint water washing-water washing.By the lithium ion tracer experiment and hydraulic characteristics investigation,we found the long term running has no obvious sideeffect on the SDN hydraulic characteristics,that`s good for the pollutant removal.On the contrary,due to the rapid growth of heterotrophic microorganism,the high sludge yield,the increased dead zone ratio led to the deterioration of hydraulic characteristics and poor treatment effect.According to the microbial community composition analysis,the microbial diversity in SDN was significantly lower than that in DN filter.The proteobacteria was the main microbial phylum in two filters.Sulfurimonas.sp and Thiobacillus.sp are the main microorganisms in SDN,there are also some heterotrophic and ferric respiration microorganisms.The quality of SDN effluent satisfies the V standard of GB3838-2002,the material costs 0.052 Yuan/t.By using DN denitrify,it causes the effluent secondary pollution easily by carbon source addition and costs very much.Combined the above results,the stable effect of simultaneous denitrification and phosphorus removal got by adding ferrous sulfate in influent.The phosphorus removal rate is 82%at 0.14mg/L and TN is 1.5mg/Lin the effluent,the quality satisfies the V standard of GB3838-2002,the cost is 0.064Yuan/t.Considering many aspects,this new filter technology has more advantages. |
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