A critical review of the recently developed laboratory-scale municipal solid waste landfill leachate treatment technologies

Leachate contamination poses a serious risk to water resources. Therefore sustainable treatment techniques are essential to protect the environment and public health. The study provides a comprehensive review of leachate treatment technologies with a critical evaluation of the strengths and limitations. The choice of technology is highly dependent on the capital and operating cost, types of leachate, and regulatory standards. The study observed that aerobic biological treatment (e.g., lagoons, constructed wetlands) and physicochemical treatment (e.g., air stripping, coagulation, flocculation, etc.) are suitable to remove organic substances. While the above technologies have limitations in treating heavy metals and ammonia. On the other hand, adsorption and advanced oxidation are very effective in treating old leachate that contains heavy metals and NH₃-N. But the process needs pretreatment and expensive chemicals supply, which is unsustainable. Advanced oxidation can efficiently remove COD, especially from matured leachates due to the complete degradation of recalcitrant organic pollutants. Still, it seems ineffective for young leachates with high organic pollutant loads. The review also identifies the cost for chemicals and energy needed to treat different leachates with each specific technology. Therefore, innovative techniques are required that will minimize energy consumption, sludge and toxin production, and recover organic, inorganic, xenobiotic compounds in a harmless phase and maximize their beneficial applications.