Preparation And Application Of High Microorganism Enrichment Density Filler

With the rapid development of economic and society of rural areas in China,a large amount of rural sewage generated in people's daily production and life.The biofilm treatment system has been widely used in the treatment of rural sewage owing to its advantages such as the excellent processing effect,the large amount of active microorganism per unit volume,the strong ability to resist impact load,no sludge expansion,the convenient operation and management.As the carrier for the attachment and growth of microorganism,the filler is the core component of the biofilm wastewater treatment system,which affects the removal efficiency of sewage pollutants directly.At present,the inorganic filler is widely used in the biofilm wastewater treatment system.However,most inorganic filler has poor biological affinity and low microbial attachment but high density.Most of the inorganic filler is made of clay and prepared by sintering process,which has the disadvantages such as the high preparation cost and energy consumption as well as wasting land resource.The surface of the inorganic filler is easy to glaze at high temperature,which is not conducive to increase its specific surface area.In view of above problems,a new type of high microorganism enrichment density filler was prepared by non-sintered process in this study.The new filler had the advantages such as large specific surface area,more microbial adhesion,the production raw materials was cheap and easy to obtain,and low energy consumption in the preparation process compared with the conventional inorganic filler.The research result could provide a certain scientific basis and technical support for the application of the new filler in the biofilm wastewater treatment system.In this study,high microorganism enrichment density filler was prepared with fly ash,dewatered sludge,cement,calcium oxide and aluminum powder.The amount of raw materials and the preparation process parameters were optimized through the orthogonal experiment and single factor experiment.The physical and chemical properties of the filler were characterized by SEM,XRD and other analysis methods.The new filler was applied to the biological aerated filter?BAF?system for treating the rural sewage,and the conventional ceramsite filler was selected as control.The characteristics of biofilm adhesion characteristics and removal efficiency of pollutants of BAF were investigated.The effects of HRT,air-water ratio and backwash on the operation of BAF were studied.The microbial community structure of the new filler BAF system was analyzed based on the high-throughput sequencing technology.The relationship between microbial community structure,removal effect of pollutant and operating parameter in BAF system were analyzed.The removal mechanism of sewage pollutants in the new filler BAF system was discussed.The optimized raw material ratio was that the dewatered sludge was 15%,the calcium oxide was 5%,the cement was 25%,the fly ash was 55%,and the aluminum powder was0.02%.Steam curing at 90?through 12 hours was the optimum technological condition of the preparation of the new filler.Under the optimum condition,the density of the new filler was 730 kg/m³,the apparent density was 1258 kg/m³,the compressive strength was 1.7 MPa,the specific surface area was 21.3 m²/g,the porosity was 42%,the water absorption was 22%,and the solubility of hydrochloric acid was 1.8%.Each performance index of the filler could meet or better than the standard of artificial ceramsite filter material for water treatment?CJ-T299-2008?.The biofilm of the new filler BAF hung successfully after 25 days with the concentration of COD of influent was 117²02 mg/L and the air-water ratio was 10:1.The amount of biofilm on the surface of the new filler and the control filler during startup were 102 mg/g and82 mg/g,respectively.The BAF could achieve higher pollutants removal efficiency when the HRT was 6h and the air-water ratio was 7:1.The removal rates of COD,NH₃-N and TN were74%,73%and 32%,respectively.The cycle of backwash was determined to be 45⁵5h.Backwash had little effect on the removal effect of COD,and the removal effect of NH₃-N could recover within 15 hours after backwashing.The concentration of COD in the new filler BAF decreased gradually along the flow direction,pH increased first and then decreased,the concentration of DO decreased first and then increased,the concentration of NH₃-N and TN decreased gradually,the concentration NO₂-N and NO₃-N increased first and then decreased,the amount of biofilm decreased gradually,and the activity of biological increased gradually.The economic analysis showed that the cost of new filler preparing was 566 yuan/m³,the new filler had obvious economic advantage compared with the traditional sintered ceramsite filler which cost 900¹200 yuan/m³.The high-throughput sequencing technology was uesd to analyze the microbial community structure of the new filler BAF system.The result showed that the new filler had complex components and properties,its selective effect on microorganisms was stronger than the control filler.And the new filler had a large specific surface area which could attach more microorganisms.The biofilm on the surface of the new filler was thicker,and the presence of aerobic and anoxic environment made the microbial diversity at the bottom of the new filler BAF system was better than that of the control BAF system.However,the physical and chemical characteristics of the new filler changed the living environment of the microorganisms,and the trace elements such as Ca²⁺and Fe³⁺of the new filler participated in microbial metabolism,the microorganisms with poor tolerance were eliminated in this process,resulting in the middle and upper part of the new filler BAF were not as good as the control filler BAF.At the level of phylum classification,Proteobacteria and Bacteroidetes were the most predominant phylum in all biofilm samples,and their relative abundance in each biofilm sample were all greater than 50%and 10%,respectively.At the level of genus classification,thiotrix,dokdonella and ottowia were the dominant bacteria shared by all biofilm samples.Polyangium was the unique dominant bacterium belong to the new filler BAF,with relative abundance of 0.34%,28.17%,17.29%,0.45%,0.78%,and 0.69%in each biofilm sample.This showed that the new filler had a certain selective effect on the types of microorganisms and a certain regulating effect on the abundance of functional microorganisms.Polyangium rarely appeared as a dominant bacterium in the sewage treatment system.This indicated that the BAF system with the new filler had a certain selective effect on the type of microorganisms and a certain regulating effect on the abundance of functional microorganisms.