Nitrate Removal From Aquaculture Using Poly(ε-caprolactone)and Poly(3-hydroxybutric Acid-co-3-hydroxyvaleric Acid )as Carbon Source

The pollution of nitrate nitrogen has always been focused and urgently resolved in the aquaculture activities.Solid counter nitrification stands out with its simple,easy-to-control features in many denitrification methods.In this paper,PCL and PHBV were used as carriers and carbon sources to control the results of high concentrations of nitrate nitrogen in circulating aquaculture water against two carbon sources.Through the understanding of the degradation of PCL and PHBV,PCL and PHBV as biofilm fillers and carbon source denitrification reactors,and the long-term treatment effect of the reactor after stable film formation.In order to provide technical support for the denitrification of aquaculture wastewater,and provide a theoretical basis for denitrification equipment of the new circulating water system.1.Effects of several physical and chemical factors on the production of DOC Efficiency in PCL and PHBV under aseptic conditionsUnder non-biological conditions,the release profiles of carbon sources PCL and PHBV under various conditions were studied,and then it was explored whether the degradation of carbon sources under non-biological conditions could be used for denitrification.The results show,PHBV does not release DOC under abiotic factors,Increasing the temperature and increasing the shaking conditions of the shaker will increase the carbon release ability of the PCL,pH has little effect on the release of PCL,and the dissolved organic carbon concentration in the aqueous solution released by PCL will inhibit the release of PCL.The DOC released by PCL under non-biological conditions can be used for denitrification.The denitrification with PCL natural leachate and glucose as the carbon source has an average removal rate of（31±2）%and（28±2）%,and the DOC of the effluent are about 10.38±1.25 mg/L2.Experimental study on the membrane of PCL and PHBV for solid-reverse nitrification of carbon sourcesThe removal efficiency of nitrate nitrogen and the change of concentration of water quality index in the start-up phase of a continuous denitrification reactor with PCL and PHBV as carbon sources and carriers were studied.PCL and PHBV were the carbon source reactors for 21 days and 17 days respectively.The highest removal rates were（57.43±1.43）%and（36.44±1.48）%,respectively.The average removal rate of PCL as a carbon source was significantly higher than that of PHBV as a carbon source.Denitrification removal rate.During the whole experiment period,neither nitrite nor ammonia nitrogen accumulated and remained at a low level.The average concentration of nitrite nitrogen was lower than 0.1 mg/L.The average ammonia concentration was maintained at about 0.5 mg/L.3.Denitrification on effects of long-term treatment of recirculating aquaculture water using PCL and PHBVTo remove the nitrate in the circulating water system,The study of the fixed membrane sequencing batch reactor was established by the degradation of poly（ε-caprolactone）and poly（3-hydroxybutric acid-co-3-hydroxyvaleric acid）as organic carbon source and biofilm carrier respectively.The influent NO₃^--N is81.1-132.65mg·L^-1,the flow rate is 1 L/h,working 102 days,the carbon source filling rate is 19%,the nitrate average removal rate of PCL and PHBV is（54.32±15.85）%and（39.75±12.42）%under these conditions.There was no presence of ammonia nitrogen and nitrite accumulation during the experiment.Removal of 1g nitrate requires the consumption of PCL and PHBV respectively（1.01±0.11）g and（3.37±0.39）g by calculation.High-throughput sequencing analysis shows,The dominant bacteria group of the surface biofilm of PCL are Proteobacteria、Bacteroidetes and Chlorobi.The dominant bacteria group of the surface biofilm of PHBV are Proteobacteria、Bacteroidetes and Firmicutes.At the genus level,The dominant bacteria group of the surface biofilm of PCL are Acidovorax（27%）and Denitratisoma（7%）.The dominant bacteria group of the surface biofilm of PHBV are Acidovorax（18%）and Bdellovibrio（8%）.Among the identified bacteria,the Acidovorax can degrade the BDPs and has an denitrification function.