Investigation of a sewage-integrated technology combining an expanded granular sludge bed (EGSB) and an electrochemical reactor in a pilot-scale plant

A sewage-integrated treatment system (SITS) for the treatment of municipal wastewater, consisting of an expanded granular sludge bed (EGSB) reactor to remove soluble organic matter and an electrochemical (EC) reactor to oxidize the NH₃-N, was evaluated. The performance of the EGSB reactor was monitored for 12 months in a pilot-scale plant. Iron shavings were added to the EGSB reactor on the sixtieth day to improve the removal efficiency of the chemical oxygen demand (COD), suspended solids (SS) and total phosphorus (TP). After the iron shavings were added, the effluent COD, SS and TP decreased from 104 to 46 mg L⁻¹, 21 to 8.6 mg L⁻¹ and 3.62 to 1.36 mg L⁻¹, respectively. Moreover, in the EC reactor, which was equipped with IrO₂/Ti anodes, the NH₃-N and total nitrogen (TN) concentrations decreased from 25 to 12 mg L⁻¹ and 29 to 15 mg L⁻¹, respectively. The NH₃-N was directly oxidized to N₂, resulting in no secondary pollution. The results demonstrated the possibility of removing carbon and nutrients in a SITS with high efficiency. The system runs efficiently and with a flexible operation, making it suitable for low-strength wastewater. The results and parameters presented here can provide references for the practical project.