Study On Enrichment Process And Influential Factors Analysis Of Marine Low Temperature Nitrifying Bacteria

It would do harm to the cultured species such as fish and shrimp when there areexcessive amounts of ammonia nitrogen and nitrite nitrogen. So it is necessary toremove them, and the common ways is the addition of nitrifying bacteria agents,which is effective, simple to operate and without secondary pollution. However, thegrowth rate of nitrifying bacteria is low and it is easily affected by the environmentalfactors. Especially, the growth rate and activity of it will be decreased at thetemperature of20℃below. The temperature of aquaculture water is always20℃below, especially cultivating cold-water fish. Therefore, it is significant for thedevelopment of aquaculture industry to enrich marine nitrifying bacteria which ishighly active at low temperature.This study was to establish a method of nitrifying bacteria enrichment, andexplore the nitrifying characteristic and the community structure and influentialfactors of the enrichment culture. The results proved:(1)An equipment of nitrifying bacteria enrichment culture was established, whichhad been obtained a patent. It was equipped with cooling system constituted by waterchannel and water chiller, monitoring system constituted by pH meter and dissolvedoxygen meter and dissolved oxygen and culture system. The water channel of theequipment and its outer cover was made of organic glass with paper for keeping outof the light and avoiding evaporation of water.(2)The enrichment culture of AOB with the nitrifying capacity of25.76mgNH4+-N/(L·d) could be gotten under the condition of16~18℃,pH7.5~8.0,DO4.5~5.5mg/L after27day-long enrichment culture, and the averageparticle size of it was7.521μm. The enrichment culture of NOB with the nitrifyingcapacity of109.68mgNO2--N/(L·d) could be gotten under the condition of16~18℃,pH7.5~8.0,DO2.5~3.5mg/L after41day-long enrichment culture, and the averageparticle size of it was5.738μm.(3)The ammonia nitrogen or nitrite nitrogen removal efficiency of the enrichment culture of nitrifying bacteria was higher in comparison with thecommercially available nitrifying bacteria under the appropriate conditions. Thenitrifying capacity of the enrichment culture of AOB and NOB was higher by3.73,4.19,5.94,8.19and4.73,4.23,3.53,3.17in comparison with the commerciallyavailable nitrifying bacteria at the temperature of15℃,18℃,21℃,24℃respectively,and the special nitrification rate of the enrichment culture of AOB and NOB washigher by16.20,18.30,25.14,33.13and9.08,8.19,6.65,5.66in comparison with thecommercially at the temperature of15℃,18℃,21℃,24℃respectively.(4) Organobentonite, talcum powder, active bentonite, white corundum, sodiumbentonite and calcium bentonite affected nitrifying bacteria differently. The nitrifyingcapacity of the enrichment culture of AOB with sodium bentonite and the enrichmentculture of NOB with active bentonite was the highest.(5) The dominant bacteria of the enrichment culture of AOB was B-42, and theproportion was42.15%; next for Flavobacteriaceae, the proportion was29.28%; theproportion of Nitrosomonadales which could oxidize ammonia was0.97%. Thedominant bacteria of the enrichment culture of NOB was Halorhodospira, and theproportion was84.13%; the proportion of Nitrobacter, Nitrospira and Nitrococcuswhich could oxidize nitrite was0.02%,0.29%and0.37%respectively.