Study On The Preparation And Application On Sewage Treatment Of The Suspended Carrier PVFM Composited With Natural Fiber

With the rapid process of urbanization, the problem of water pollution is getting more and more serious. Increasing the renewable utilization rate and improving the shortage of water resources is imminent. In recent years, improving the performance of suspended carriers becomes one of the research hotspots in the field of biofilm water treatment. Develop a new type of filler which has the characteristics of low-cost, easy to hang membrane and good sewage treatment effects, and make it be widely used in wastewater treatment is meaningful.In this thesis, a new type of biological carrier was prepared by using the chemical foaming methood combined with mechanical blistering method. This new type of suspended carrier was natural fiber-polyvinyl formal composite materials (called NF-PVFM), which was added in the natural fiber and used polyvinyl formal (called PVFM) as skeleton structure. By testing the properties of apparent density, water absorption, porosity, wet tensile strength and surface roughness, the appropriate synthesis conditions of NF-PVFM were optimized by single-factor experiments. The conditions were as follows:In200mL10%polyvinyl alcohol solution, under the reaction temperature of60℃, add2.0g200-250μm diameter acacia fiber soaked for48h with15wt%NaOH solution, sodium dodecyl sulfate1.0g, sulfuric acid solution (1:1)30mL, formaldehyde solution15mL, foaming agent sodium bicarbonate0.3g. On the basis of above experiments, investigate the influence of fly ash content to the performance of NF-PVFM. Under the best dosage of4.0g, the natural fiber/fly ash-polyvinyl formal (called NF/FA-PVFM) had good physical and chemical properties.Using the method of rapid discharge sludge bio-membrane, the performance of biofilm and the effects of sewage treatment about PVFM suspended carrier were researched in the biological fluidized bed reactor, the relationship between physical-chemical properties and biofilm culturing performance was studied. The results showed that, the acacia fiber and fly ash can improve the physical-chemical and biochemical properties of PVFM suspended carrier, the starting time of biofilm culturing was shorten. The advantages and disadvantages of biofilm culturing performance maintained a consistent with the wastewater treatment effects. The biofilm forming speed of NF/FA-PVFM was the fastest, the thickness of0.5～1mm fawn biological membrane was appeared in the third day, the biofilm was basically mature after14days, and the biomass on the carrier was176.23mg/g after21days. The biofilm culturing speed of NF-PVFM was closed to the NF/FA-PVFM, the biofilm quantity reached174.33mg/g after21days. The biofilm forming speed of pure PVFM was slowest, the biofilm biomass was165.01mg/g after21days. The CODcr removal rate of three kinds of PVFM suspended carrier was basically stable at90%, the NF-PVFM had the highest CODcr removal rate, which reached93.82%. The TN removal rates of NF-PVFM, NF/FA-PVFM and pure PVFM were stable respectively at64%,65%,60%around. The TP removal rates of three kinds of suspended carrier were stable between69%-72%, the TP removal efficiencies of NF-PVFM and NF/FA-PVFM were better than pure PVFM.The stable operation and the effects of sewage treatment about suspended carriers were investigated in the biological fluidized bed reactor, in order to examine the performance of the new type carrier. The experimental results showed that, NF-PVFM had the best operational stability, and it had good fluidized state in the bioreactor which could fulfill the technical requirements of suspended carrier. But NF/FA-PVFM was needed to increase the amount of aeration to improve the degree of fluidization, for it had a poor fluidized state. On the removal rate of CODa, TN and TP, NF-PVFM and NF/FA-PVFM had better effects than pure PVFM. NF-PVFM had the best CODcr removal effect with an average removal rate of94.05%. The TN average removal rates of NF-PVFM and NF/FA-PVFM were63.30%and65.61%, the TP average removal rates were70.93%,71.32%respectively.The suspended carrier of NF-PVFM had good abrasion resistance. After nearly two months of biofilm culturing and sewage treatment experiments, there were no abrasion and damage phenomenon appeared on the suspended carrier, and the aging phenomenon caused by microbial erosion was not been found.