Effect of dissolved oxygen on nitrate removal using polycaprolactone as an organic carbon source and biofilm carrier in fixed-film denitrifying reactors

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• 作者：Guozhi Luo¹ ; ² ; ³ ; ^{gzhluo@shou.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Guimei Xu¹ ; Jinfang Gao¹ ; Hongxin Tan¹ ; ² ; ³
• 关键词：Heterotrophic denitrification ; Dissolved oxygen ; Biodegradable polymers ; Polycaprolactone ; Recirculating aquaculture system
• 刊名：Journal of Environmental Sciences
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：43
• 期：Complete
• 页码：147-152
• 全文大小：619 K

文摘

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 ± 0.05 mg/L), the low-oxygen treatment DO group (Group B, average DO concentration of 2.50 ± 0.24 mg/L) and the aerated treatment group (Group C, average DO concentration of 5.63 ± 0.57 mg/L). Feeding with 200 mg/L of NO₃⁻-N, the NO₃⁻-N removal rates were 1.53, 1.60 and 1.42 kg/m³ 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 6 mg/L on heterotrophic denitrification in the fixed-film reactors filled with PCL can be mitigated.