Application and Efficacy of Management Interventions for the Control of Microplastics in Freshwater Bodies: A Systematic Review

Abstract

This systematic review represents one of the first attempts to compare the efficacy of the full suite of management interventions developed to control (prevent or remove) microplastics (MPs) in freshwater bodies, both man-made and natural. The review also traces the evolution of research on the topic in relation to the timing of key policy and regulatory events and investigates whether interventions are being applied within regions and freshwater bodies that represent concerns in terms of MP pollution. The review incorporated bibliometric analysis and meta-analysis of 124 original research articles published on the topic between 2012 and April 2023. To supplement the key findings, data were extracted from 129 review articles on the major knowledge gaps and recommendations. The number of articles on the topic increased with each year, coinciding with a range of global policy commitments to sustainability and mitigating plastic pollution. The majority of the studies focused on MPs in general, rather than any particular particle shape or polymer type, and were conducted at wastewater/sludge treatment plants. Upstream interventions accounted for the majority of studies reviewed (91.1%). A smaller proportion (4.8%) of studies involved reduction in production and physical removal at the point of production (1.6%); treatment-related objectives such as removal through filtration and separation and the combination of these with other technologies in hybrid systems were dominant. Of the physical, chemical and biological methods/technologies (and combinations thereof) employed, physical types (particularly membrane filtration) were most common. The majority of the studies within the wastewater/sludge, stormwater and in situ water/sediment categories exhibited removal efficacies >90%. Although new interventions are constantly being developed under laboratory conditions, their scalability and suitability across different settings are uncertain. Downstream interventions lack sustainability without effective upstream interventions. Though in situ methods are technically achievable, they may not be feasible in resource-limited settings.