Research On The Characteristics Of Biofilm On Several Packings And The Optimization Of Biofilm Parameter

On the basis of water pollution characteristics of Jiaxing City and rapid development of bio-ecological remediation technology for polluted water bodies, research on the characteristics of biofilm on several packings and the optimization of biofilm parameter were carried out to provide technical support for engineering applications. The main results were as follows:1.Effects of different types of packing on the biofilm formation in simulated bioreactors were studied. Combined packing, elastic packing and novel bamboo packing were selected as the testing packing. The results showed that the removal efficiency of combined packing and elastic packing were better than bamboo packing during the test. When the reators were stable, the reator with elastic packing had the most number of bacteria. In contrast, elastic packing was more favorable for static biofilm formation.2. At present, research on the biofilm colonization on the packing have been extensively carried out, but few specific studies on the impact of dissolved oxygen on biofilm colonization were conducted. To study the effect of oxygen on biofilm colonization, three groups of bioreactor were designed in which DO were controlled at 4.0-5.Omg·L-1,4.6-6.0mg·L-1 and 5.2-6.5mg·L-1 respectively. The results showed that the removal efficiency of tubidity and NH3-N were significantly better in the third bioreactor than the first one. The thickness of biofilm on the packing in the third bioreactor was 20～160μm, at the same time, polysaccharides content in EPS (extracellular polymeric substances) and biofilm activity were higher than the other two groups. In contrast, The third bioreactor showed the most stable biofilm structure and the maximum biofilm activity. After biofilm mature, the CODcr and NH3-N in effluent could reach the grade III of "Environment Quality Standard for Surface Water" (GB3838-2002).3.To study the effect of oxygen on biofilm colonization, three groups of bioreactor were designed in which DO were controlled at 2L/(L·d),1L/(L·d) and 0.67L/(L·d), respectively. The results showed that the average removal rate of CODcr in three reactors were 56.1%,55.2% and 46.6% during the test and the time for effluent CODcr stabilization were 6d,6d and 13 d, respectively. The removal efficiency of NH3-N had not reached the steady state, mainly due to the fluctuations of temperature. The third reactor had the largest number of bacteria and the dry weight of biofilm gradually increased with the augment of hydraulic loading.4. Tridimensional floating bed is an innovative type of biological pretreatment. Previous studies were usually focused on the removal efficiency of pollutants, few research on biofilm characteristic on the packing were carried out. This test used an enhanced treatment composed of aeration system and new tridimensional floating bed for micro-polluted river water purification. The biofilm characteristics on the packing and purification of the water during biofilm colonization were studied. The results showed that when temperature was 15.2℃～23.6℃, pH 7.0-7.8, dissolved oxygen 4.0 mg·L-1～5.9 mg·L-1, it took approximately 40 days for the biofilm maturation. Based on the analysis of water quality and microbial indicator, the process of biofilm colonization could be divided into four stages including physical adsorption, physical adsorption with rapid proliferation of microbes, enhanced adsorption and degradation by microbes, and the biofilm maturation. After maturation of biofilm, the removal efficiency of turbidity, CODcr and NH3-N could reach 20.1%,17.5% and 18.3%, respectively, showing a high purification efficiency.