Removal of refractory organic pollutants in reverse-osmosis concentrated leachate by Microwave-Fenton process.

A microwave-Fenton technology was applied to dispose of the reverse-osmosis concentrated leachate. Influential factors on the treatment of concentrated leachate with the pure Fenton and microwave-Fenton method were investigated. For the conventional Fenton process, the removal efficiencies of chemical oxygen demand (CODCr ), UV254 , and the color number (CN) reached 84%, 87%, and 96%, respectively, with the biodegradability (BOD5 /CODCr ) increased from 0.13 to 0.51 at an initial pH of 5.0, Fe2+ of 0.04 mol/L, a n(H2 O2 )/n(Fe2+ ) ratio of 8 after a reaction time of 3 h. When incorporating the Fenton process with microwave irradiation, a comparative CODCr and UV254 , and the CN removal rate of 75%, 83%, and 95%, and a high BOD5 /CODCr of 0.62 were achieved under a microwave power of 390 W and an extremely shortened reaction time of only 8 min. Meanwhile, sludge quantity showed a reduction of 24.7%, decreased from 8.50 g/L to 6.40 g/L after the participation of microwave. In addition, molecular-weight fraction (MWF), UV-visible spectrum (UV-vis), and 3D-EEM spectrum tests demonstrated that the macromolecular and complex organic compounds in the wastewater were significantly decomposed into small molecular matters. Our results found that microwave-Fenton is a promising technology for concentrated leachate treatment, with much shorter reaction time, lower sludge production, and enhanced biodegradability, as well as comparative organic matter removal performance.