Microplastic contamination in wastewater sludge and its agricultural reuse risks, pathways, and management-a review

Microplastics (MPs) are small plastic particles that are present in the wastewater sludge which is frequently reused to fertilise the agriculture. The review focuses on the entry of MPs into sludge through sources such as laundry, personal care products, industrial waste, city runoff, and air. Majority of the sludge consists of very small (less than 500 micrometres) MPs that are predominantly polyethylene, polypropylene, and polyester (PET) etc. When sludge is applied to farmland, MPs move into the soil and persist for years, carrying harmful chemicals and bacteria. MPs alter the soil structure and hinder the activity of microbes, damage the growth of plants. They also have the potential to spread other pollutants and antibiotic resistance genes which are dangerous to the environment and human health. To tackle these risks, the review discusses about the solutions such as superior filters in the washing machine, enhanced wastewater treatment technologies, and other sludge treatment methods (thermal treatment and biochar). Authors emphasise the necessity to have strict regulations, enhanced surveillance and combined risk evaluation to reduce MP discharge into wastewater and to make sure that sludge reuse in agriculture is safe and sustainable.