Microplastics in landfill leachate: Occurrence, health concerns, and removal strategies.

Landfills are commonly used to manage solid waste, but they can contribute to microplastic (MPs) pollution. As plastic waste degrades in landfills, MPs are released into the surrounding environment, contaminating soil, groundwater, and surface water. This poses a threat to human health and the environment, as MPs can adsorb toxic substances. This paper provides a comprehensive review of the degradation process of macroplastics into microplastics, the types of MPs found in landfill leachate (LL), and the potential toxicity of microplastic pollution. The study also evaluates various physical-chemical and biological treatment methods for removing MPs from wastewater. The concentration of MPs in young landfills is higher than in old landfills, and specific polymers such as polypropylene, polystyrene, nylon, and polycarbonate contribute significantly to microplastic contamination. Primary treatments such as chemical precipitation and electrocoagulation can remove up to 60-99% of total MPs from wastewater, while tertiary treatments such as sand filtration, ultrafiltration, and reverse osmosis can remove up to 90-99%. Advanced techniques, such as a combination of membrane bioreactor, ultrafiltration, and nanofiltration (MBR + UF + NF), can achieve even higher removal rates. Overall, this paper highlights the importance of continuous monitoring of microplastic pollution and the need for effective microplastic removal from LL to protect human and environmental health. However, more research is needed to determine the actual cost and feasibility of these treatment processes at a larger scale.

Peroxidases from an invasive Mesquite species for management and restoration of fertility of phenolic-contaminated soil.

Phenolics drive the global economy, but they also pose threats to soil health and plant growth. Enzymes like peroxidase have the potential to remove the phenolic contaminants from the wastewater; however, their role in restoring soil health and improving plant growth has not yet been ascertained. We fractionated efficient peroxidases (MPx) from leaves of an invasive species of Mesquite, Prosopis juliflora, and demonstrated its superiority over horseradish peroxidase (HRP) in remediating phenol, 3-chlorophenol (3-CP), and a mixture of chlorophenols (CP-M), from contaminated soil. MPx removes phenolics over a broader range of pH (2.0-9.0) as compared with HRP (pH: 7.0-8.0). In soil, replacing H2O2 with CaO2 further increases the phenolic removal efficiency of MPx (≥90% of phenol, ≥ 70% of 3-CP, and ≥90% of CP-M). MPx maintains ~4-fold higher phenolic removal efficiency than purified HRP even in soils with extremely high contaminant concentration (2 g phenolics/kg of soil), which is desirable for environmental applications of enzymes for remediation. MPx treatment restores soil biological processes as evident by key enzymes of soil fertility viz. Acid- and alkaline-phosphatases, urease, and soil dehydrogenase, and improves potential biochemical fertility index of soil contaminated with phenolics. MPx treatment also assists the Vigna mungo test plant to overcome toxicant stress and grow healthy in contaminated soils. Optimization of MPx for application in the field environment would help both in the restoration of phenolic-contaminated soils and the management of invasive Mesquite.