Physicochemical Treatment Approaches for Leachate Treatment

The generation of solid waste is anticipated to continue to increase globally. One of the most cost-effective methods for managing solid waste is landfilling, which is widely utilized. Leachate is a liquid that extracts dissolved and suspended materials as it flows through a landfill which is comprised of organic, inorganic, and heavy metal pollutants. As landfill leachate has a high level of toxicity, it is recommended to utilize truly effective techniques of purification to avoid contaminating the ecosystem. There are different methods available for treating landfill leachate which are based on biological processes (activated sludge, aerobic and anaerobic stabilization ponds and biological filters), physicochemical processes (coagulation/flocculation, adsorption, electrochemical treatment, filtration and advanced oxidative processes) and natural attenuations (wetlands). The applications of treatment technique, however, have been constrained by a variety of criteria, including processing effectiveness, operational strategy, power requirements, and financial benefits. Among other factors, the relationship between landfill age and leachate composition should be taken into consideration when adopting the best technique. Even though biological processes are commended for their favorable, cost–benefit, and operational simplicity, effective utilization is only possible in landfills with BOD5/COD ratio greater than 0.5 which shows higher biodegradability in the leachate. Moreover, temperature increases seem to facilitate faster stabilization of organic matter, resulting in a more recalcitrant leachate. Furthermore, the BOD5/COD ratio decreases as landfill age, whereas the amount of non-biodegradable organic material increases in aged leachate. Excessive amounts of heavy metals in leachate may hinder the microorganisms responsible for ammonia removal. Thus, with the increase in landfills’ age and ammoniacal nitrogen concentrations, conventional biological treatment approaches may become ineffectual in meeting the legislatively allowed threshold values for disposal into aquatic bodies. Due to bio recalcitrant substances that are difficult to be biologically treated, physicochemical treatment is the most suitable treatment for mature landfill. Hence, different treatments consisting of physicochemical approaches for leachate treatment were investigated and reviewed in this chapter.