Reuse of sewage sludge as a catalyst in ozonation - Efficiency for the removal of oxalic acid and the control of bromate formation

► Sewage sludge was converted into catalyst (SBC) and characterized. ► SBC can enhance oxalic acid degradation in ozonation. ► Surface reaction mechanism is responsible for enhancement of ozonation by SBC. ► SBC can control the formation of bromate in ozonation. ► Several combined reasons for the control of bromate formation are proposed.