Simultaneous removal of organics and ammonia using a novel composite magnetic anode in the electro-hybrid ozonation-coagulation (E-HOC) process toward leachate treatment.

To achieve simultaneous organics and ammonia (NH4+-N) removal toward leachate treatment, this study designed a composite anode (CA+), in which iron powders were attracted to RuO2-IrO2/Ti tube surface by an inserted magnet and utilized in electro-hybrid ozonation-coagulation (E-HOC). The E-HOC (CA+) resulted in higher chemical oxygen demand (COD) and NH4+-N removal with most content of CO2/H2O and gaseous N in product compared with E-HOC (Fe+), electrolysis ozonation and single ozonation. Reactive chlorine species (RCS) and coagulants were co-produced by compositing RuO2-IrO2/Ti and Fe powders, resulting in multiple reactions including electrocoagulation, ozone oxidation, synergistic between ozone and coagulants (SOC), electrolytic chloride and synergistic oxidation between active chlorine and ozone (SCO) occurred. Hydroxyl radical (•OH) generated through SOC reaction was promoted due the RCS generation in E-HOC. The interaction between •OH and Cl-/ClO- also contributed to enhanced Cl•/ClO• production. Consequently, synergy of chlorine, coagulants and ozone enhanced reactive species generation which contributed to favorable organics and NH4+-N removal. Enhanced •OH and RCS are also attributed to conversion of bio-refractory organics like polyphenol, polycyclic aromatics and S-containing to biodegradable ones, e.g., aliphatic compounds and CHO. This study provides an easily operating strategy for leachate treatment with high content organics and NH4+-N.