Properties Of Marine Nitrifying Bacteria And Their Application In Circulation Water Treatment Of Sea Cucumber Aquaculture

As continuous development of marine aquaculture industry, recycled watercultivation process is being applied more and more broadly. Recycled water cultivationsystem is efficient, environment-friendly and energy-saving. Through artificial controlof crucial cultivation parts, it can achieve the optimal economic benefit by controllingcultivation technical index in appropriate range, based on the specific needs ofcultivation objects. The most important part of recycled seawater cultivation system isrecycled water treatment process. Since the main pollutant of aquaculture water isammonia and nitrogen, so it is the key to control the accumulation of ammonia andnitrogen in the water. In recent years, nitrogen removal of wastewater using certainnitrobacteria has been emphasized. Especially many researchers found that certainheterotrophic denitrifiers can conduct hetetrophic nitrification and aerobicdenitrification, which is in practical significance to treat high DO and comparativelylow ammonia aquaculture wastewater.The article conducts growth and physiological characteristics research on marineheterotrophic nitrifiers MN-2which has been enriched and domesticated, then comes toknow its optimal growth conditions and investigates its nitrogen removal performanceand metabolic pathway. After that the author investigates the practical denitrificationperformance of marine heterotrophic nitrifiers by using MN-2Member Enhanced BioReactor. According to comparing dominant biofilm formation and spontaneous marinebiofilm formation, the author finds out the optimal operation conditions of recycledwater treatment process; The article also designs the sea cucumber recycled watercultivation system based on the growth environment of sea cucumber, with membranebio reactor as main body and provides relevant parameters and suggestions on factoryproduction.The experiment results shows that:（1） Compared with autotrophic bacteria, marine heterotrophic nitrifiers MN-2hasthe advantages of higher growth rate, longer stable growth period, mass propagation innutritionally adequate environment and the ability to become dominant bacteria in theenvironment. According to the nitrogen balance test, MN-2can conduct nitrification anddenitrification using nitrate nitrogen. It shows that MN-2is more suitable in theapplication of recycle aquaculture water treatment process which is of high recycle frequency and ammonia accumulation rate.（2） Through comparing the adsorption capacity on MN-2of three carriers, theauthor got that the oyster shell, is most suitable bio-carrier. Start time of biofilmformation can be shortened more than15days when MN-2dominant bacteria is addedmanually. After the biofilm is stable, ammonia and nitrite nitrogen in the recycled waterremain very low level and the concentration of nitrate nitrogen is between2-3mg L^-1.MN-2bio-film formation can conduct nitrification and denitrification, which can lowerthe peak value of substrate and suit better in recycle water aquaculture, whilecomparatively, spontaneous marine biofilm only can conduct nitrification. By singefactor analysis of HRT and ammonia concentration of inflow, MN-2bio-film formationcan achieve the best nitrogen removal performance when the inflow ammoniaconcentration is3mg L^-1, HRT is20min.（3）When designing the recycled water aquaculture process, aiming to treat seacucumber aquaculture water using the nitrogen removal capacity of MN-2. The authortakes into account the integrated factors of breeding density, bait, water temperature andso on in integrated factors. During the lab cultivation process, ammonia nitrogen, nitritenitrogen and nitrate nitrogen decreases into a level which is in favor of the growth of seacucumber when aeration time during all the day and circulating water treatment for12hours. It can also be concluded that is reasonable to clean the feces and residual feedssedimented in the culture every7days. The author also provides necessary processparameters for factory recycled water design based on the feasibility research of MN-2bio-film formation water treatment process through the lab environment.