Construction Of Low-temperature Biofilm And Application In Aquaculture Seawater

The strains of denitrifying bacteria F (Halomonas alimentaria), photosynthetic bacteriaP6-2(Rhodovulum sulfidophilum) and bacillus Y8-2were obtained from Microbiological Labof Hebei University. After cold acclimation, they were added to the18-20℃artificialseawater in both conditions of being free floating and immobilized. The purification effectswere tested in the recirculation aquaculture seawater system by observing the removal rate ofnitrate, nitrite and ammonia as the purification index. We researched the optimum proportion(R/H ratio) of two strains, and the most suitable carrier for membrane forming in the coldseawater.The artificial seawater was made by sea salt and aquaculture water,30in salinity,16-18℃. In the free floating P6-2group, the removal rate of nitrite nitrogen, nitrate nitrogenand ammonia nitrogen is15.82%,20.39%, and20.18%. In the free floating F group,purification efficiency of nitrite nitrogen, nitrate nitrogen and ammonia nitrogen is26.32%,26.43%and21.10%. After being mixed in proportion of1:1, the free floating P6-2and Fshowed a higher removal rate. The removal rate of nitrite nitrogen, nitrate nitrogen andammonia nitrogen is33.12%,41.26%, and24.07%.We chose sodium alginate and embedding method as the immobilization technology.According to the experiments results and cost, The optimum adding amount of bacteria liquidwas20mL/L water. To determine the optimum proportion (R/H ratio) of two bacterial strains,the F and the P6-2were immobilized with sodium alginate and added to purifyingbio-ceramic units in different proportions. The purification effects were tested in therecirculation aquaculture seawater system. The results showed the highest removal rate ofnitrate and ammonia at a R/H ratio of75%, in which the removal rates of ammonia, nitrateand nitrite were79.72%,90.61%and77.06%.Immobilized bacteria were added to purifying units made up by bio-ceramic, quartz sandand activated carbon respectively. The results showed a highest removal rate in the activecarbon purifying unit. Experiments showed that, the active carbon has the best ability in water treatment. In the active carbon in the experimental group, the removal rate of nitrite nitrogen,nitrate nitrogen and ammonia nitrogen is83.79%,86.39%, and83.11%.The above experiments established the basic route of sodium alginate embedded asimmobilization technology, active carbon as the biofilm matrix. According to the results, weadded a Bacillus strain as the compatibility of bacteria. After testing, the removal rate ofnitrite, nitrate and ammonia nitrogen reached93%,95.4%,96.9%.