title: Effect of dissolved oxygen on nitrate removal using polycaprolactone as an organic carbon source and biofilm carrier in fixed-film denitrifying reactors.
abstract: Nitrate-nitrogen (NO3(-)-N) always accumulates in commercial recirculating aquaculture systems (RASs) with aerobic nitrification units. The ability to reduce NO3(-)-N consistently and confidently could help RASs to become more sustainable. The rich dissolved oxygen (DO) content and sensitive organisms stocked in RASs increase the difficulty of denitrifying technology. A denitrifying process using biologically degradable polymers as an organic carbon source and biofilm carrier was proposed because of its space-efficient nature and strong ability to remove NO3(-)-N from RASs. The effect of dissolved oxygen (DO) levels on heterotrophic denitrification in fixed-film reactors filled with polycaprolactone (PCL) was explored in the current experiment. DO conditions in the influent of the denitrifying reactors were set up as follows: the anoxic treatment group (Group A, average DO concentration of 0.28±0.05mg/L), the low-oxygen treatment DO group (Group B, average DO concentration of 2.50±0.24mg/L) and the aerated treatment group (Group C, average DO concentration of 5.63±0.57mg/L). Feeding with 200mg/L of NO3(-)-N, the NO3(-)-N removal rates were 1.53, 1.60 and 1.42kg/m(3) PCL/day in Groups A, B and C, respectively. No significant difference in NO3(-)-N removal rates was observed among the three treatments. It was concluded that the inhibitory effects of DO concentrations lower than 6mg/L on heterotrophic denitrification in the fixed-film reactors filled with PCL can be mitigated.
authors.affiliation: College of Fisheries and Life Science of Shanghai Ocean University, Shanghai 201306, China; Shanghai Collaborative Innovation Center for Aquatic Animal Genetics and Breeding, Shanghai 201306, China; Research and Development Center of Aquacultural Engineering of Shanghai, Shanghai 201306, China. Electronic address: gzhluo@shou.edu.cn.
authors.forename: Guozhi
authors.initials: G
authors.lastname: Luo
authors.affiliation: College of Fisheries and Life Science of Shanghai Ocean University, Shanghai 201306, China.
authors.forename: Guimei
authors.initials: G
authors.lastname: Xu
authors.affiliation: College of Fisheries and Life Science of Shanghai Ocean University, Shanghai 201306, China.
authors.forename: Jinfang
authors.initials: J
authors.lastname: Gao
authors.affiliation: College of Fisheries and Life Science of Shanghai Ocean University, Shanghai 201306, China; Shanghai Collaborative Innovation Center for Aquatic Animal Genetics and Breeding, Shanghai 201306, China; Research and Development Center of Aquacultural Engineering of Shanghai, Shanghai 201306, China.
authors.forename: Hongxin
authors.initials: H
authors.lastname: Tan
mesh_terms: D018441:Biofilms; D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification; D009566:Nitrates / Q000032:analysis*; D058458:Nitrogen Cycle; D010100:Oxygen; D011091:Polyesters; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D011091:Polyesters; D014874:Water Pollutants, Chemical; C016240:polycaprolactone; D010100:Oxygen
keywords: Biodegradable polymers; Dissolved oxygen; Heterotrophic denitrification; Polycaprolactone; Recirculating aquaculture system