Preparation Of Bamboo Fiber Biofilm Carrier And Its Application Research In Domestic Sewage Treatment

Aiming at solving the problems of short service life, high price, and environmental pollution for the biocarries used nowly, a new type of bamboo fiber biocarrier was first prepared, which was made up of bamboo fiber, polyester fiber, and foamed plastics of ethylene vinyl acetate copolymer. In this study, the physical properties of bamboo fiber carrier were measured, including surface area, porosity, hydrophilicity, and adsorption of NH₃-N and TP. The parallel test of biofilm reactor with bamboo fiber biocarrier and the one with combined packing was employed to study the film formation performance of bamboo fiber biocarrier. Then the reactors with bamboo fiber biocarriers were also used to treat the low concentration domestic sewage. Finally, it was studied on the optium condition and microbial morphology in the biological contact oxidation process of bamboo fiber biocarrier.Taking into account of the cost and hydroscopicity of carrier, there were three biocarriers, prepared wih diffirent ratios of bamboo fiber and polyester fiber. The specific surface area of this biocarrier was up to 5393 m2·m-3. Under the external force, the saturated absorption of water were about 6.9 g·g^-1 after 120 min. The increase of bamboo fiber content helped to improve the hydroscopicity. At 25℃, the saturated adsorption of NH₃-N onto the three kinds of bamboo fiber carrier（A,B,C）, were 806.45 mg·kg^-1, 613.50 mg·kg^-1, and 621.12 mg·kg^-1, as well as that the saturated adsorption of TP were 568.18 mg·kg^-1, 363.64 mg·kg^-1, and 247.53 mg·kg^-1. The comparative test results of bamboo fiber biofilm carrier and combined packing showed that the former’s performance of film formation and capacity of resisting impact was better. After 6 days, the COD_Cr removal rate of two biocarriers reached 70% and 74%, completely. Different hydraulic retention times were get by regulating flow. This test results showed that the treatment effect of pollutants by bamboo fiber biocarrier was better than that by combined packing. When HRT was 5 h, the difference of COD_Cr removal between bamboo fiber biofilm carrier and combined packing was biggest, which was about 7%, as well as that the biggest difference of NH₃-N removal was about 8%.The biggest difference of TN was about 9%when HRT was 4 h, then the biggest difference of TP was about 10%when HRT was 6 h.Furtherly, the three biological contact oxidation reactor with bamboo fiber carrier were employed to treat the low concentration domestic sewage by changing the operation paramenters of HRT, gas-water ratio, and so on. Considering the actual economic and engineering factors, the technical conditions were ultimately determined, which of HRT 8 h, and gas-water ratio about 9:1. In this condition, the effluent concentrations of COD_Cr, NH₃-N,TN and TP remained under 50.0 mg·L^-1, 1.5 mg·L^-1,5 mg·L^-1 and 1.0 mg·L^-1, completely. The comparison of the three reactors runned under this conditon and the aerobic system of wastewater treatment plant showed that the COD_Cr removal of the former was about 13%, 20% and 29%, higher respectively than that of the latter. TheⅢreactor with 70% bamboo fiber was predominate in the aspects of biofilm culturing speed, treatment efficiency, stability and resistance capacity.In order to illustrate the effect of the biofilm of bamboo fiber and the treatment efficiency, the microbial morphology was studied. In growth of bamboo fiber biofilm, there was a variety of microbes, the main kinds of which were flagellate, swimming ciliates, sessile ciliates, rotifers, nematodes. The appearance of biofilms was brown at stationary phase, thickness of which about 2 5 mm, the volume up to 0.8984 g·g^-1.