Immobilization Of Novel Denitrification Strains

With rapidly developing of industry and agriculture, improving of the level of human life, widely using of pesticides, fertilizers and synthetic detergent, increasing of sewage discharge amount and so on, the nitrogen in sewage gradually become main pollutants.The methods of wastewater denitrification mainly includes physical-chemistry denitrification method and biological denitrification method, and the biological denitrification method is considered as one of most cost-effective methods.Immobilized microorganisms technology as a new technique of biological denitrification method, comparing of traditional suspended biological treatment, have many advantages, such as high density of microorganism, less loss, better ability of resistance to poison and resistantion shock load, easy separate of product, miniaturization of process equipment, easy operation, strong stability, less number of surplus sludge and so on.But the mixed immobilization of novel denitrification strains-heterotrophic nitrfier and aerobic denitrifier has been less reported. According to a efficient heterotrophic nitrfier and a efficient aerobic denitrifier which are screeninged by our laboratory, we investigated immobilized effect of different embedding agent and cross-linking agent, confirmed immobilized scheme of mixed strains, and optimized immobilized conditions of mixed strains, researched denitrification conditions of immobilized strains, inspected the removal efficiency of actual sewage by immobilized strains.Main research finding was following:1. Carrier combination of mixed-immobilized HN-S and DN-S strains is10%PVA+1%SA, and cross-linking agent is saturated boric acid(adding Na2CO3to adjust pH=6.7、2%CaCl2). According to physical traits(such as easily or hardly into the ball, strength of balls, stability, performance of transferred-material), we synthetically evaluated the quality of immobilized balls which are formed by different embedding agent, additive agent and cross-linking agent.We finded the quality of immobilized balls which are formed by embedding agent10%PVA, additive agent1%SA and cross-linking agent saturated boric acid(adding Na2CO3to adjust pH=6.7、2%CaCl2)was best.2. With the index of TN removal rate, we confirmed best immobilized conditions of the mixed-strains by single factor experiment and orthogonal experiment:the concentration of PVA is10%, the weight ratio of enrichment bacterium fluid and embedding agent solution is1:1, the time of cross-linking is24h, the percentage composition of SA in PVA gel is1%.3. The empty immobilized ball which was formed by PVA-SA don’t have toxicity for mixed-strains, this system was suitable for growth of mixed-strains.The denitrification speed of immobilized strain was slower than speed of free strains, but the time of its denitrification was longer, it had longer using lifetime, and the nitrogen assimilation was lower, thus enhanced its denitrification effect.After immobilization, the tolerance ability of mixed-strains for extreme pH, extreme temperature and high nitrogen concentration all are improved.4. According to storage test, We found the effect of immobilized balls which was storaged on4℃medium soaking was best. After immobilization, The advantage of mixed-strains which handle low concentration Nitrogen containing wastewater(Hubing pools wastewater)is not very better.But when handle high concentration Nitrogen containing wastewater(the food manufacturer), The Nitrogen removal effect of mixed-strains was greatly increased, and the lifetime of strains was prolong.