Comparison of UV/H2O2 based AOP as an end treatment or integrated with biological degradation for treating landfill leachates

The application of a biological treatment together with a chemical oxidation process was investigated. In particular, the effectiveness of the biological treatment followed by a UV/H2O2-based advanced oxidation process (AOP) used as an end treatment was compared with that in which the same AOP was integrated with biological degradation for treating a medium age sanitary landfill leachate. The results show that better performance with removal efficiencies higher than 80% for all investigating parameters was obtained when AOP was integrated with the biological treatment, thus allowing the discharge limits to be met. This was due to the biological removal of the biodegradable compounds produced by UV/H2O2 treatment. Instead, UV/H2O2-based AOP biodegradability enhancement gave no advantage when it was used as an end treatment. Finally, the results show that H2O2 alone (i.e., without UV power) was quite ineffective either as a mineralizing or as a biodegradability enhancing agent and that the only reactive species was essentially the hydroxyl free radical OH.