A novel process for landfill leachate pretreatment using hydrodynamic cavitation combined with potassium ferrate oxidation

Abstract

AbstractBACKGROUNDEfficient pretreatment is key to improving landfill leachate biodegradability. This is the first study to combine hydrodynamic cavitation (HC) and potassium ferrate (K2FeO4) for the treatment of landfill leachate, using chemical oxygen demand (COD) and UV absorbance at a wavelength of 254 nm (UV254) as the main test indicators. The feasibility of HC combined with K2FeO4 as a mature leachate pretreatment method was explored.RESULTSThe HC experiment used 40 L of mature landfill leachate raw water, with optimal reaction conditions of: pH 4, 70 min continuous cavitation and K2FeO4 dosage of 1.5 g/L. The leachate COD decreased from 3812.64 mg/L to 1833.8 mg/L (51.69% removal), while UV254 decreased from 20.44 to 6.14 (65.14% removal) and total organic carbon decreased from 1489 to 915.3 mg/L (38.53% removal). After HC/K2FeO4 treatment, the biochemical oxygen demand after 5 days (BOD5)/COD (0.61) was greatly improved compared to the raw leachate (0.362), with effluent reaching the standard (BOD5/COD >0.6) required to be considered fully biodegradable. Studies have shown that HC can accelerate the reaction rate of Fe(VI) with pollutants, while also forming a Fenton‐like system with the products of Fe(VI) reduction. FT‐IR analysis results showed that HC/K2FeO4 treatment achieved the removal of complex high molecular weight compounds, by carbonization or decomposition into more biodegradable substances.CONCLUSIONCompared with the traditional pretreatment process, HC/K2FeO4 exhibits strong oxidation and coagulation performance, achieving the significant removal of leachate humus and effectively improving biodegradability, while also being suitable for large‐scale applications, such as landfill leachate treatment. © 2022 Society of Chemical Industry (SCI).