Development Of An Immobilized Nitrogen Removal Bacterial Consortium For Treating With Nitrogenous Sewage

Nowadays eutrophication is one of more severe problems occurred in water pollution,and the occurrence and deterioration of eutrophication are caused by many factors, among which increase of nutrient substance content is the main one. In this study, aiming at removing nitrogenous substance from the pollution water we developed an immobilization technology of bacterial consortium for nitrogen removal to reduce nitrogen concentration in sewage and decrease the risk of causing eutrophication. The ammonifier, heterotrophic nitrosobacteria, nitrobacteria and denitrifying bacteria were screened from activated sludge, soil and other niches. The strains were identified by observation of colony morphology, physiological and biochemical characteristics and 16S rDNA sequence analysis. The bacterial consortium for nitrogen removal was composed of four strains that had different functions and able to reduce organic nitrogen and ammonia nitrogen concentration efficiently without accumulating nitrate and nitrite. The granule immobilization technology of nitrogen removal bacterium consortium was researched, the composition was optimized and the quality evaluation system of immobilized granules was established. The treating effect of the immobilized granule on nitrogenous sewage in self-developed sewage treatment reactor was studied. This paper provided theoretical basis and practical guidance for nitrogenous sewage treatment by microbial means. It has combined immobilization technology of nitrogen removal bacterial consortium with the technique of sewage treatment reactor, which had great purification effect on nitrogenous sewage. The following conclusions were mainly drawn:1. Screening and identification of ammonifier, heterotrophic nitrosobacteria, nitrobacteria and denitrifying bacteria196 bacteria including 112 ammonifiers, 46 heterotrophic nitrosobacteria, 25 nitrobacteria and 13 denitrifying bacteria were obtained through enrichment and initial screening from activated sludge, fish pond water and soil. 18 high efficient strains including four ammonifiers, four heterotrophic nitrosobacteria, four nitrobacteria and five denitrifying bacteria were gained through secondary screening. A nitroso-C-3, G nitro-3, M ammonia-4 and R denitro-5 were identified as Bacillus subtilis, Pseudomonas mendocina, Bacillus subtilis and Pseudomonas pseudoalcaligenes, respectively.2. Construction of nitrogen removal bacterial consortiumThe bacterial consortia were constructed from four strains which had respective function, and there were 72 consortia in all. The AMGR consortia were screened out according to the principle of reducing organic nitrogen and ammonia nitrogen concentration efficiently and accumulating no nitrite and nitrate nitrogen. The denitrogen rate of AMGR consortia was higher than others. The denitrogen rate of AMGR was 65.32% within 48h and 95.27% within 96 h.3. Preparation of immobilized consortium granules, optimization of granule ingredient and quality evaluation.Polyvinyl alcohol (PVA) and Na-alginate were used as a gel matrix to entrap microbes within the beads, and optimized compositions were 0.25% Na-alginate, 2% activated carbon, 12% PVA and linking cross time of 24 h. Immobilized nitrosobacterium Bacillus subtilis A beads were prepared under the optimized formula. The results showed the carbon source was beneficial to ammonia nitrogen removal and granules with two different bacterial concentration have similar effect on removing ammonia nitrogen. Compared with immobilized single bacterium, the immobilized consortium had better effect of removing nitrogen in the simulated eutrophic water and river. This paper proposed the quality evaluation system of immobilized microbe beads in aspect of physical, chemical and microbial index.4. Effect of immobilized Bacillus subtilis A granule on ammonium nitrogen-rich sewage in bioreactor systemImmobilized Bacillus subtilis A beads would be in the steady state after one week's domestication. In the continuous treating process, when HRT was 20 min, the concentration of ammonium nitrogen effluent was lower than 0.3 mg/L, and removal rate of ammonia nitrogen was more than 90%; Compared with low DO condition, high DO was beneficial to removing ammonium nitrogen; More suitable carbon nitrogen ratio was 10.5. Effect of immobilized bacterium consortium on nitrogen removal in sewage treatment reactorImmobilized nitrogen removal bacterium beads would work in fixed bed reactor and fluid bed reactor, and this paper researched the effect of sewage treatment under different parameters and optimized these parameters.â‘ In fixed bed continuous flow way, the results showed HRT of 20 min was a suitable retention time, at which time the removal rates of effluent total nitrogen was close to 100%.â‘¡In fluid bed intermittent flow way, the removal rate of effluent total nitrogen was close to 100% when HRT was 140min and DO was between 56.8% and 71.6%. This reactor system was fit for slight pollution water, initial nitrogen concentration in which was below 20 mg/L.â‘¢In fluid bed continuous flow way, the removal rates of total nitrogen were between 78.12% and 80.86% under HRT of 12h and DO of 43.0~56.8%. In addition, compared fixed bed reactor, the treatment effect of fluid bed reactor was better.6. The theoretical discussion on nitrogen removal of immobilized denitrogen bacterial consortiumIn the process of nitrogenous sewage treatment with immobilized denitrogen bacterial consortium, the nitrogen removal played major role; Observing with the scanning electron microscopy, we found that the microbes after domestication would show succession in distribution, mainly at surface layer of beads; The dominant gas produced by bacterial consortium was the nitrogen gas.