Influence of pH in AOP on Humic Compounds Removal from Municipal Landfill Leachate Concentrate after Reverse Osmosis

The choice of the optimal method of municipal waste landfill leachate treatment should take into account such factors as: the variability of their composition and quantity over time, requirements for effluent or economic capacity. Due to the variety of compounds found in landfill leachate, it is advised to use a combination of different treatment processes. Biological methods are effective in the treatment of leachates from young landfills, but generally their efficiency declines significantly with the age of the landfill. Therefore, the physicochemical methods, i.e. advanced oxidation, adsorption, membrane methods or a combination of the mentioned, are preferred. The aim of the study was the assessment of the Fenton's reagent utilization to process reverse osmosis concentrate of leachates collected from municipal non-hazardous waste landfill. The research was focused on the influence of pH on the process. Additionally, the effectiveness of organic compounds removal, increasing the biodegradability, as well as humic substances transformations were determined. The concentrations of humic compounds were measured by means of optical density at the wavelengths: 254, 265, 280, 320, 465 and 665 nm. In the experiment, the H2O2/Fe2+ 10: 1 ratio was tested at with a dose of H2O2 equal to 3.4 g/l (0.1 M). It was found that the pH affects the efficiency of COD removal and the increase of the biodegradability of the landfill leachate retentate, as well as the removal of humic substances and its transformation. It was found that at pH 3, the highest removal of COD occurs, with simultaneous increase in biodegradability, and decrease of absorbance caused by humic compounds.