Kinetics and oxidative mechanism for H2O2-enhanced iron-mediated aeration (IMA) treatment of recalcitrant organic compounds in mature landfill leachate

A hydrogen peroxide (H2O2)-enhanced iron (Fe0)-mediated aeration (IMA) process has been recently demonstrated to effectively remove organic wastes from mature landfill leachate. In this paper, the kinetics and oxidative mechanisms of the enhanced IMA treatment were studied. Bench-scale full factorial tests were conducted in an orbital shaker reactor for treatment of a mature leachate with an initial chemical oxygen demand (COD) of 900-1200 mg/L. At the maximum aeration rate (8.3 mL air/min mL sample), process variables significantly influencing the rates of H2O2 decay and COD removal were pH (3.0-8.0), initial H2O2 doses (0.21-0.84 M), and Fe0 surface area concentrations (0.06-0.30 m2/L). Empirical kinetic models were developed and verified for the degradation of H2O2 and COD. High DO maintained by a high aeration rate slowed the H2O2 self-decomposition, accelerated Fe0 consumption, and enhanced the COD removal. In hydroxyl radical (OH) scavenging tests, the rate of removal of glyoxylic acid (target compound) was not inhibited by the addition of para-chlorobenzoic acid (OH scavenger) at pH 7.0-7.5, ruling out hydroxyl radical as the principal oxidant in neutral-weakly basic solution. These experimental results show that this enhanced IMA technology is a potential alternative for the treatment of high strength recalcitrant organic wastewaters.