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• Application of membrane separation process in China is comprehensively investigated. • Leachate treatment capacity of NF is the highest in landfill and incineration plant. • A combination of NF and RO exhibits the best efficiency for leachates treatment. • Membrane processes are more likely to be adopted in economically developed regions. • Operation costs of membrane process mainly depends on the pre-treatment process. To comprehensively investigate the application of membrane separation technology in the treatment of landfill leachate in China, the performance of nearly 200 waste management enterprises of different sizes in China were analyzed, with an emphasis on their scale, regional features, processes, and economic characteristics. It was found that membrane separation technologies, mainly nanofiltration (NF), reverse osmosis (RO), and NF + RO, have been used in China since 2004. The treatment capacity of the two most dominant membrane separation technologies, i.e., NF and RO, were both almost 60,000 m3/d in 2018, and both technologies are widely used in landfills and incineration plants. Their distribution is mainly concentrated in eastern and southwestern China, where the amount of municipal solid waste (MSW) is relatively high and the economy is developing rapidly. Membrane separation technology is the preferred technique for the advanced treatment of leachate because more contaminants can be effectively removed by the technology than by other advanced processes. However, the membrane retentate that is produced using this technology—commonly known as leachate concentrate—is heavily contaminated due to the enrichment of almost all the inorganic anions, heavy metals, and organic matter that remain after bioprocessing. An economic cost analysis revealed that the operating cost of membrane separation technology has stabilized and is between 1.77 USD/m3 and 4.90 USD/m3; electricity consumption is the most expensive cost component. This review describes the current problems with the use of membrane separation technology and recommends strategies and solutions for its future use. [ABSTRACT FROM AUTHOR]

• Solidification and stabilization effect of Pb in MSWI fly ash was compared. • Pb leaching concentration, volume change ratio, and treatment cost were evaluated. • Combined solidification-stabilization process yielded the best treatment effect. • Optimal parameters are obtained through response surface methodology. Fly ash is a hazardous material that is produced from municipal solid waste incineration. It contains heavy metals and should be properly treated to meet landfill entry requirements. In this study, under the precondition that the leachable concentration of lead (Pb) exceeded the limit value for landfill disposal, the effects of cement solidification, chemical stabilization, and their combination on the leachable Pb concentration and the chemical state of Pb were systematically investigated. In addition, the reaction conditions were optimized by response surface methodology (RSM) in terms of leachable Pb concentration, volume change ratio, and treatment cost. The results indicated that the leachable Pb concentration decreased at lower cement or sodium dihydrogen phosphate (NaH 2 PO 4) dosages in cement solidification or NaH 2 PO 4 stabilization, and the liquid-to-solid ratio had a significant influence on cement solidification. The leachable Pb concentration met the limit value for landfill disposal in the individual processes with 20% cement or 5% NaH 2 PO 4 , and in the combined process with 10% cement + 2% NaH 2 PO 4. The combined process achieved the best treatment efficiency by enabling Pb to transform to a stable residual state. According to the RSM, a combined cement content of 11.64%, NaH 2 PO 4 content of 2.79%, and liquid-to-solid ratio of 0.48 were the optimal parameters, resulting in substantial decreases in the volume change ratio and treatment costs, while satisfying the preconditions for landfill disposal. In conclusion, the combined process can reduce the pollution risk to the environment, and is an efficient and cost-effective pre-treatment method for incinerator fly ash. [ABSTRACT FROM AUTHOR]