GREEN TECHNOLOGIES FOR LEACHATE MANAGEMENT: FERRATE OXIDATION AND ADVANCED MEMBRANE FILTRATION

Abstract

Leachate is the liquid wastewater produced after the percolation of water through the waste deposited at a specific landfill or dumpsite. Landfill leachate carries very high concentrations of unwanted organic, inorganic, and metallic compounds, which are harmful in nature, consequently contaminating the surface and sub-surface water resources. In traditional practices, the landfill leachate has been treated through biological methods such as activated sludge process, trickling filter, as well as physicochemical techniques such as filtration, super/advanced oxidation, etc. Conventional leachate treatment technologies often fail to meet necessary effluent standards, negatively impacting the environment. Advancements in membrane technology offer a greener, more efficient approach to leachate treatment, providing stable effluent with high rejection rates for pathogens and contaminants. Ultrafiltration (UF) membranes are widely used in water and sewage treatment, but membrane fouling remains a significant challenge. To address this, pretreatment techniques such as coagulation and oxidation are recommended for their simplicity and low cost compared to other methods (e.g., electrochemical, ultrasonic, air stripping, adsorption, photocatalysis). Common coagulants and oxidants like ferric chloride (FeCl3), aluminum sulfate (Al2(SO4)3), calcium hydroxide (Ca(OH)2), sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2), and potassium permanganate (KMnO4) help minimize membrane fouling, though their effectiveness can be limited by the formation of disinfectant by-products and low destabilization performance. In this study, we adopted ferrate (Fe6+) as green pre-oxidation due to its environment friendly nature for hollow fiber (HF) UF membranes system. Further, to overcome the limitations of fouling, scaling, and reduced flux, the interface of the HF UF membrane was modified and treated via plasma enhanced chemical vapor deposition (PECVD). The promising capabilities of the PECVD technique was established as a viable approach for swiftly enhancing membrane surface hydrophilicity (water contact angle ≈ 18°) and high porosity (≈ 80 %). This surface-modified membrane was utilized further to remove the organic and inorganic fractions from Fe6+ pre-treated landfill leachate. The membrane demonstrated promising results, including a permeate flux of nearly 53.19 L/m2/h and removal efficacies of 98.6 % for COD and 98.07 % for TOC.