Research On The Application Technology Of Nitrifying Bacteria

The autotrophic nitrifying bacteria play a critical role in nitrogen cycle in nature. The detection and application of nitrifying bacteria is limited by their peculiar ecophysiology such as strict autotrophic bacteria and slow growth. But they are urgently needed in the nitrogen pollution removal in several fields in the serious conditions of nitrogen pollution in our country. This paper focused on the key problems about application technology of nitrifying bacteria and finished some research about the techniques of enrichment, detection method and application methods in nitrogen pollution removal. The following are the results.1. In the MPN-Griess method of enumeration of nitrite-oxidizing bacteria, the nitrite concentration deeply effect the enumeration results and detection time. The o.lmmol/L nitrite concentration in the culture is the best choice for MPN-Griess method and the shortest detection time is 4 week.2. A rapid enumeration method for nitrifying bacteria was developed using the 2-(p-indophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT) ?dehydrogenase assay. The enumeration results were correlated well with those results of MPN-Griess method. The two methods correlation of ammonia-oxidizers and nitrite-oxidizers are 0.9593 and 0.9823, respectively. Compared with the conventional MPN method, INT dehydrogenase method is more rapid, simpler, and easily operated. The detection periods were shorten from 4 weeks of MPN to 2 days. The INT dehydrogenase is a pragmatic method for rapid detection of nitrifying bacteria.3. Choosing the activated sludge of aerobic tank from one municipal wastewater treatment plant as the resource, the nitrifying bacteria were enriched by inorganic medium. During the first week, the nitrifiers increased 2 orders of magnitude.The ammonia-oxidizers were increased from 2.13 106 /g MLSS to 6.28 108 /g MLSS, while the nitrite-oxidizers were increased from 2.13 103/g MLSS to 6.28 106/g MLSS. After a month, most of the heteotrophic bacteria were washed out from the system. They nitrifying bacteria were prevalent in the enrichment system and were around 99% in total bacteria. The results proved the feasibility of this enrichment technique. The enriched nitrifying bacteria can directly storein a lucifugal condition for a long time, the nitrifiers decay at a rate of 0.0138d-1. But the decay rate of the nitrifiers stored in phosphate buffer (pH 7.2) is 0.023d-1.4. In order to seek the solution for water purification and reduce the water quantity used in the artificial propagation of mud crab, one kind of biologic combined technology is provided in this paper. The enriched nitrifying bacteria and other beneficial microorganism are used as predominant strains in rearing pond and inoculated in bio-contact oxidization reactor. Some basic experiment and mud crab artificial propagation production experiments were done. The basic experiment showed the enriched nitrifying bacteria can quicken the nitrifying biofilm formation, strengthen it to adapt the high salted water and reduce NH3-N from 5 mg/L to 0.7mg/L under a short HRT condition (1.2 hour). The mud crab artificial propagation production experiments results showed the biologic combined technology could recycle and reuse the pond water and improve the water quality, reduce production cost and pollution against the water environment. The dissolved oxygen .concentration of the experimental pond water can keep in more than 7.5 mg/L and the NH4+-N concentration can keep in less than 0.5mg/L without exchange the pond water. The water quality of the experimental rearing pond was obviously better than the normal check rearing pond. The total survival ratio of mud crab megalops larva was 19.4% and the yield was 175.8g/m3 in the experimental pond. The survival ratio, yield and quality of mud crab megalops larva in the experimental pond was much better than them in the normal check pond. Good economic retu...