Leachate degradation using solar photo-fenton like process: Influence of coagulation-flocculation as a pre-treatment step

Abstract

The effectiveness of using solar photo-Fenton-like processes to degrade sanitary landfill leachates was investigated. Leachate samples exhibited varying composition, owing to a mixture of older and younger effluents from a former dump site subsequently converted into a sanitary landfill. Coagulation assays (jar test) using Al3+, Fe2+, and Fe3+ in the 240–800 mg L–1 range were performed to evaluate optimal coagulant concentration for abatement of chemical oxygen demand (COD) and dissolved organic carbon (DOC). A high COD (53%) and DOC (72%) removal rates were obtained for Al3+ but there was a very substantial increase in the turbidity. Optimal coagulant concentration was then adopted, and the effluents were subjected to photo-Fenton processes at laboratory scale. At this scale, coagulation by Fe3+ at 240 mg L–1 combined with a photo-Fenton-like method exhibited superior performance, with 66% DOC removal by coagulation and over 70% DOC removal using the photo-Fenton-like process. Solar photodegradation was conducted for 180 min at [Fe3+] ≈ 100 mg L–1, pH = 3.0 ± 0.3, and [H2O2] = 50–250 mg L–1 at a solar pilot plant. Use of solar photo-Fenton-like processes improved effluent biodegradability, irrespective of coagulation pretreatment, and also reduced leachate toxicity, as shown by acute ecotoxicity tests using Lactuca sativa seeds, Allium cepa bulbs, and Artemia salina, proving to be a promising treatment method in line with the National Solid Waste Policy, which promotes and encourages non-generation, reduction, reuse, recycling, the treatment of solid waste, and the environmentally appropriate final disposal of tailings.