Micro-Nano-Plastics in Sewage Sludge: Sources, Occurrence, and Potential Environmental Risks

The presence of microplastics (MPs) as a global contaminant has gained increasing attention, particularly in relation to water pollution. However, research on MPs in sewage sludge remains restricted in comparison. MPs originating from many sources accumulate inside sewage systems, with a significant portion becoming entrapped within the sludge throughout the sewage treatment process. Consequently, the sludge not only serves as a sink for MPs but also as a source of MPs. The utilization of sludge in soil amendments offers the advantage of nutrient provision while potentially introducing a significant microplastic (MP) content into the soil. However, it is important to acknowledge the associated environmental hazards. MPs that have accumulated in the soil can alter its properties and migrate, leading to the contamination of subsurface soils and groundwater. Furthermore, it is important to consider the adsorption of heavy metals and organic pollutants by microplastics (MPs) in sewage sludge, given that these pollutants are often present in significant quantities within the sludge. The coexistence and interplay of microplastics (MPs) and the pollutants they absorb might amplify the environmental hazards, hence enhancing the possibility of their absorption by plants. There is a need for further exploration and investigation of MPs in soil amendments as they can cause long-term risks to the environment. Therefore, this chapter focuses on MPs in sludge, sources of MPs in sewage sludge, and their sampling, separation, and identification methods.