Isolation Of Heterotrophic Nitrifying Bacteria In Recirculating Aquaculture Wastewater Treatment

To solve the slow recirculating aquaculture system initiating stage andaccumulation of anitrogen recirculating aquaculture systems, especially the problem ofthe nitrate nitrogen accumulation in the traditional recirculating aquaculture systems,this study started from heterotrophic nitrifier, the study isolated heterotrophic nitrifyingbacteria strain with efficient denitrification capacity from an activated sludge, than usedit in the practical application of aquaculture wastewater treatment, and provide a basisfor the development of new recirculating aquaculture technology. The results of thisexperiment were as follows:1The study of the bacteria’s isolation, screening and nitrogen use efficiency.This study isolated heterotrophic nitrifying bacteria strains from an activatedsludge, after screening, choose a heterotrophic nitrifying bacteria with obviousnitrification. According to molecular biological identification,this bacteria belonging toacinetobacter. and was high similar to Acinetobacter calcoaceticus, and the similarityreached99%.This bacteria strain had no effect on the short term growth of the tilapia,but we can not be sure whether the bacteria had toxicology or not. In practice, youshould be attacking poison experiments to determine whether had toxicology or not forbreeding object.The results of this study showed that: A1in this study belong to Acinetobacter, its16S rDNA sequence similarity with Acinetobacter calcoaceticus reached99%, and ithad heterotrophic nitrification-aerobic denitrification, belonging to heterotrophicnitrifier.when screening,the initial ammonium nitrogen concentrations was104mg/L, After60h culture, the ammonia removal rate by the strain was89.64%, the maximuminstantaneous Ammonia removal capability was4.54mg/(L*h). During the nitrificationprocess of the strain, the initial ammonia concentration was10mg/L, the ammonia nitrogen removal by the strain rate was80.31%and TOC removal rate by the strain was52.61%. Nitrification process did not find nitrite. During the denitrification process ofthe strain, the initial nitrate nitrogen concentration was10mg/L, the nitrate nitrogenremoval rate by the strain was74.2%and the total nitrogen removal rate by the strainwas46.5%and TOC removal rate was only34.63%. Denitrification process fond traceamounts of nitrite. The strain can use a single nitrite as nitrogen source, when the nitriteconcentration was10mg/L, the strain can effectively remove nitrite, the removal ratewas88.56%while the content of TOC and TN were both reduced, TOC removal ratewas54.74%, total nitrogen removal rate was68.06%.2. Treatment of aquaculture wastewater by the heterotrophic nitrifier.In the experiment of single heterotrophic nitrifier bacteria recirculating aquaculturewastewater, The bacteria can effectively remove the nitrate, total nitrogen and TOC ofaquaculture water, removal rates were91.70%,83.56%and67.57%. But during theexperiment, the ammonia concentration have a fluctuation, while nitrite concentrationwas lower.In the cylindrical reactor recirculating aquaculture wastewater treatment experiment, thenitrate removal rate of experimental group was94.74%,79.48%higher than the controlgroup; total nitrogen removal rate experimental group was87.60%,48.21%higher thanthe control group; The difference in ammonia removal and TOC removal of theexperimental group and the control group is unlikely, and the difference of nitrateaccumulation between control group and the experimental group is not obvious.In the continuous survey, the nitrate concentration of experimental group increasedfirst and then decreased, the trend was similar to the trend of control group, but16hoursnitrate concentration of experimental group was lower than the control group; ammoniaconcentration of the experimental group increased first and then decreased, unlike thecontrol group, ammonia concentration of the control group showed a downward trend;The nitrite concentration in the continuous survey increased first and then decreased,and the first nitrate concentration of control group was higher than the nitrateconcentration of experimental group; while nitrogen and TOC concentrations in theexperiment were both a downward trend. In the continuous survey, the differencebetween the control group and the experimental group was not obvious, but the reactionprocess was not the same. The strain A1can use ammonia, nitrite, nitrate nitrogen as the single nitrogensource, and it can effectively remove ammonia, nitrite, nitrate, total nitrogen and TOC;while a single strain treating aquaculture wastewater, it can effectively remove theammonia, nitrite, nitrate, total nitrogen and TOC form the aquaculture wastewater;while treating aquaculture wastewater with column reactor, it can efficiently removenitrate, total nitrogen and TOC, and nitrate concentration in the reaction process was nothigh, but the bacterial cell cracking will cause fluctuations of ammonia concentration.