Energy-positive nitrogen removal of pharmaceutical wastewater by coupling heterotrophic nitrification and electrotrophic denitrification

•Substantial bioelectrochemical denitrification was noticed under closed circuitry.•The designed bioelectrochemical DNT system performed at low C/N ratios.•Sequential integration of ANT & DNT resulted in remarkable multi-pollutant removal.

An attempt was made to cohesively assess the aerobic nitrification treatment (ANT) and bioelectrochemical denitrification treatment (DNT) of real-field pharmaceutical wastewater. The ANT resulted in the removal of 73% ammonium and 78.5% organic carbon content. Subsequently, the outlet of ANT reactor was fed to DNT reactor and the relative influence of external circuitry was investigated. The DNT reactor operated with closed circuit mode (CCM) resulted in ~83% of nitrates and % ~61% of organic content removal even at low C/N ratio of 2.18. The other pollutant concentrations viz., phosphates, sulfates and total dissolved salts were also significantly removed by both ANT and DNT processes. In this study, a sequential integration of both ANT and DNT processes exhibited high potential for self-sustained energy-positive nutrient removal.

Graphical abstractSchematic view of (A) ANT (aerobic nitrification treatment) reactor and (B) DNT (denitrification treatment) reactor (1: nitrifying organisms, 2: Anode Oxidizing Bacteria, 3: Nitrate reducing bacteria, P1 & P2: Pumps).Download high-res image (147KB)Download full-size image