Operational strategy for solid phase denitrification to achieve carbon balance between organic release and...

This study developed a pilot-scale vertical-baffled solid-phase denitrification reactor (VbSPDR) incorporating polycaprolactone (PCL) and ceramsite as fillers to balance organic carbon release and denitrification consumption. The Box-Behnken design was employed to assess the effects of hydraulic retention time (HRT), temperature, and influent nitrate concentration on nitrate removal efficiency and COD accumulation. Optimal conditions yielded a 95 % nitrate removal rate at 33 °C, an HRT of 1.22 h, and an influent nitrate concentration of 19 mg/L. Conversely, effluent COD concentration was minimized and dropped 2.5 mg/L at 13 °C, an HRT of 0.39 h, and an influent nitrate concentration of 19 mg/L. The PCL layer enriched hydrolysis-acidification and heterotrophic denitrifying bacteria by unclassified_f__Comamonadaceae and Acidovorax, while heterotrophic genera Phreatobacter thrived in ceramsite layer, enhancing the metabolism of COD over-released from PCL. These findings indicate that inorganic fillers can effectively enhance nitrate removal and controll effluent COD under varied operational parameters.