Microplastics are increasingly recognized as contaminants of emerging concern in wastewater systems, where treatment plants act both as sinks and as point sources. However, Central Asian wastewater infrastructures are under-represented in the literature, and global syntheses are hindered by strong methodological heterogeneity (sampling regimes, size cut-offs, QA/QC). This PRISMA-guided critical review compiles and harmonizes data from 63 WWTP studies worldwide (402 matrix-stage observations), including the few available case studies from Kazakhstan and neighboring countries, to benchmark Central Asian plants against a global envelope and identify methodological and infrastructure gaps. Globally, influent concentrations cluster around a median ≈65 particles/L, while final/tertiary effluents show a median ≈2.2 particles/L. Median removal efficiency is 85.5% for secondary and 95.0% for tertiary/advanced trains, with ≈10³–10⁵ particles/kg DW typically retained in sludge. Across influent, effluent and sludge, fibers and fragments of PE, PP and PET dominate polymer morphology patterns, with similar PET/PE/PP signatures also reported in downstream river water. Central Asian influents fall within global interquartile ranges, but secondary-only facilities tend to yield effluents in the upper half of the global distribution. Overall, the review provides a first integrated, methodologically explicit assessment of WWTP microplastics in Central Asia and underscores the need for protocol harmonization, longitudinal monitoring, and targeted upgrades of polishing steps and sludge management in arid hydrosystems.

The occurrence of microplastics in natural and process waters presents a significant challenge for the design and operation of engineering water treatment and water supply systems in buildings and structures. This study experimentally evaluated the efficiency of a ULP21-4040 reverse osmosis membrane in removing polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) particles of different sizes from artificially contaminated water (hereafter, model water). Experiments were conducted using a pilot-scale HAIAO RO-250 unit operated at 1.3 MPa with a nominal capacity of 250 L/h. Model water was prepared by adding 1 g of each polymer with nominal particle sizes of 0.20 or 0.45mm to 100 L of distilled water. Each polymer–size combination was tested in triplicate. Microplastic particles in the permeate (treated water) and concentrate (water with increased concentrations of retained contaminants) were recovered using Sefar filter cloth with a 100 μm mesh size and quantified gravimetrically. Particle presence was confirmed by digital microscopy. Mean removal efficiency exceeded 97%, ranging from 97.81 ± 0.24% for 0.20mm PP to 99.87 ± 0.07% for 0.45mm PET. Retention efficiency depended on polymer type and particle size. Mass-balance calculations showed that an average of 0.81% of the initial microplastic mass accumulated inside the membrane module. The results support the potential application of the ULP21-4040 membrane as a final treatment stage in compact engineering water treatment systems. Further research should investigate membrane fouling, pressure losses, energy consumption, cleaning regimes, and long-term performance under actual operating conditions to support integration into building water supply systems and water reuse.