UC Irvine

The presence of high concentrations of dissolved organic matter (DOM) in landfill leachate (LL) and reverse-osmosis (RO) treated wastewater require effective treatments for their disposal. This study investigates the use of engineered photolysis using UV light (185/254 nm) as a possible treatment method for the mineralization of leachate organic matter (LOM) and RO concentrate. A flow-through UV system (NeoTech Aqua, San Diego CA) was used to photodegrade the DOM. Control experiments were carried out with Aldrich humic acid (AHA) to test the influence of flow rate, pH, DOM concentration, and buffer composition on the potential of the UV treatment to mineralize the DOM and reduce sample color. Photodegradation experiments were performed on leachate samples collected from Florida and California and tertiary-treated water samples from California. Mineralization was monitored by UV-visible spectroscopy, excitation-emission matrix (EEM) fluorescence spectroscopy and size exclusion chromatography (SEC). Photolysis resulted in a 70\% loss in UV absorbance at 254nm after 5h of treatment for both types of leachate and was associated with a reduction in color. There was an 85-95\% decrease in EEMs fluorescence intensity indicating the degradation of various compounds present in the leachate. However, the RO concentrate was found to be less photodegraded with an overall loss of 60\% in fluorescence over 4h of treatment. SEC showed the highest molecular weight peaks were the most rapidly degraded with an overall reduction in peak area with time. Post-photolysis treatment with ozone was effective in reducing the residual color with an additional decrease in fluorescence. Results from this study indicate that photolysis using UV 185/254nm lamps is an effective method for the photodegradation of DOM.