Recent occurrence of microplastics in freshwater and efficiency of available treatment technologies

This review assesses microplastic occurrence in freshwater systems globally between 2018 and 2024, examining spatial distribution patterns across rivers, lakes, groundwater, and wastewater treatment plants, alongside treatment technology efficiency. Studies were selected following PRISMA guidelines, with inclusion criteria requiring spectroscopic confirmation using ATR-FTIR or Raman spectroscopy and compliance with ISO/TR 21960 and GESAMP quality control protocols. Microplastics were detected across five continents with notable spatial variations: riverine systems showed mean concentrations of 0.5-5 particles/L, lakes exhibited 0.1-2.5 particles/L, whilst groundwater demonstrated significantly lower levels at 0.01-0.5 particles/L. The most prevalent polymers were polyethylene and polypropylene, primarily linked to secondary microplastic formation from consumer packaging degradation and agricultural film, whilst fibres (predominantly polyester and polyamide) originated from textile washing effluents, representing primary microplastic sources. Conventional drinking water treatment plants achieved 85-95% removal efficiency for particles >50 μm but declined to 40-60% for smaller fractions, with analytical limitations persisting below 5 μm. Emerging technologies including photocatalytic degradation demonstrated up to 70% polypropylene removal, though scalability challenges include high energy requirements (2-5 kWh/m³) and potential toxic intermediate formation. Health implications include endocrine disruption, inflammatory responses, and oxidative stress, with nanoplastics (<1 μm) potentially 10-100 times more prevalent than microplastics, though detection capabilities remain critically limited. Legislative frameworks, including the EU Single-Use Plastics Directive, have shown measurable reductions (20-40%) in targeted polymer types, though enforcement gaps and limited scope continue hampering comprehensive pollution control. Standardised international monitoring protocols remain integral for effective contamination assessment.