The improper treatment of landfill leachates is one of the major problems associated with waste landfilling and causes serious environmental pollution at waste landfill sites and their surroundings. To develop a suitable landfill leachate treatment system and to minimize the risk of environmental pollution, it is important to characterize seasonal and temporal variations of landfill leachates. This study investigated the leachate quality of the Nam Son waste landfill in Hanoi, Vietnam in 2017–2019 and characterized the potential risks of landfill leachate using a leachate pollution index (LPI). The results of this study showed that the seasonal and temporal variation of the overall LPI during the monitoring period was small and in the range of 20–25 (values 2.5 times higher than the maximum permissible limits of Vietnam National Technical Regulation on Industrial Wastewater). The LPI sub-indices attributed to organic and inorganic pollutants were major components of the LPI. Especially, the annually averaged values of LPI of inorganic pollutants were 7.7 times higher than the maximum permissible limits, suggesting that the treatment of inorganic pollutants, such as ammonium-nitrogen (NH₄⁺–N) and total nitrogen (TN), is highly required at Nam Son landfill to prevent environmental pollution surrounding the landfill site.

Due to stringent local regulations and adverse environmental impacts, Vietnamese coal mining industries are under pressure to reuse the large volume of wastewater they produce. To this end, the aim of this study was to add microfiltration membranes after the conventional Vietnamese coalmine wastewater treatment systems (coagulation/sedimentation/filtration) to assess the feasibility of effluent reuse. The pilot-scale test was performed at a coalmine plant located in Quang Ninh province, Vietnam. Results indicate that precipitation with slaked lime (Ca(OH)₂) and poly aluminum chloride (PACl) followed by sand filtration are important pre-treatment steps, prior to microfiltration. To achieve high Mn removals the sand in the filter had to be replaced by a KMnO₄ coated sand. The MF membrane produced a stable and high quality effluent that meets the Vietnamese National Technical Regulations for Drinking Water quality (Fe < 0.5 mg/L, Mn < 0.3 mg/L, hardness <350 mg/L as CaCO₃). Complete membrane recovery was achieved by sequential 24 h soakings in NaOCl, citric acid and a surfactant.