| Considering the township sewage treatment plant in winter, which influent is low C/N ratio, low sludge activity, microbial abundance and C/N of domestic sewage directly affects the effluent quality of some biological sewage treatment plants and the total nitrogen removal of some upgrading and reconstruction WWTP. CAST process, which contain anaerobic, anoxic and aerobic in the same reactor was studied. To improve the TN removal performance of low C/N ratio domestic wastewater treatment by CAST process, combining the biological intensive preparation and the solid carbon source was put forward. To solute the questions of carbon deficiency and low efficiency of TN removal of low C/N ratio domestic wastewater treatment by CAST process, microbial agents relate to nitrogen removal was used to improve the microbial abundance and species and solid carbon source was used to increase the C/N.Nitrogen removal characteristics of three strains aerobic denitrifiers which belong to different genus were studied. The corncob as solid carbon source and biological carrier feasibility test was introduced, which include carbon release capability and quality, aerobic denitrification capability of using released carbon and persistence of carbon release in activated sludge system. Feasibility test of using the biological intensive preparation and the solid carbon source to treat low C/N ratio domestic sewage in CAST process was also studied.Three strains aerobic denitrifiers were isolated from ponds sediments and were named strainN1,N2 and N3.Through the morphological and molecule biology identification, the three strains were identified as Pseudomonas sp.,P. stutzeri and P. aeruginosa. The denitrification of the three strains mainly occurred during the period of logarithmic growth. There is no nitrite accumulation during cultivation process of P. sp., whereas P. stutzeri and P. aeruginosa occurred nitrite accumulation. The best optimum C/N of three strains were12, 6 and 9.Beside, the best optimum temperature were 20℃~30℃,30℃and 30℃~40℃.Both the three strains can maintain a high nitrogen removal performance with a high DO in the range of 2.2mg/L to 7.6mg/L. Compared with traditional anoxic denitrification, aerobic denitrifiers have a wider range of application.During the feasibility studied when used as solid carbon source, corncob has good performance of carbon release. In addition, nitrogen release cannot cause secondary pollution. Leaching solution contains a large number of tryptophan, which are easily degraded by microorganisms. The surface structure become loose and porous after liquid immersion, which is conducive to the attachment of microorganisms. Aerobic denitrifiers can use released carbon source to denitrification metabolism. The quality unit(1g) corncob can contribute to13.6mg/L NO3--N for denitrification and 1.702mg/L NH4+-N for the receiving water system. Tryptophan in the leaching solution was replaced by fulvic acid. Corncob can continuous release to carbon source last for 20 days. During the period, the ability of carbon source release keep stable. The concentration of effluent COD keep under 50mg/L, which wouldn’t cause threat on effluent standard. After biological enhancement, the surface of corncob attached large quantity of microorganisms, which proved that corncob can be used as solid carbon source and biological carrier.Biological nitrogen removal agent, which was composed of nitrification bacteria, anoxic denitrification bacteria and aerobic denitrification bacteria, and corncob, a kind of solid carbon source, were used to enhance nitrogen removal performance of CAST reactor for treating low C/N ratio domestic sewage. The quality of domestic wastewater used in experiment was COD 150mg/L,TN 35mg/L and NH4+-N 25mg/L. The effluent COD of the enhanced reactor stayed about 30mg/L, which have no marked increase. The removal rate of ammonia nitrogen and TN increased obviously. Besides, the concentration of ammonia nitrogen and TN reached the first level A standard. Nitrogen removal efficiency of CAST process for treating low C/N ratio domestic wastewater was increased after enhanced by biological agents and corncob. The experiment proved that enhancing activated sludge system by biological agents and corncob can ensure the effluent according with the standard. The addition of biological agents related to nitrogen removal bacteria can effectively increase the species and microbial quantities of nitrogen removal system.Besides,this method can improve the performance of nitrogen removal. |
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