Assessing microplastic fate through textile wastewater treatment plants: Stage-specific retention and removal performance

Industrial wastewater treatment plants (WWTPs) are a key line of defense obstructing the release of microplastics (MPs) into the ecosystems. While removals can be efficient, the plants nonetheless release a detectable number of MPs. Most studies consider only influent and final effluent, leaving the fate of MPs in the interim treatment phases relatively unknown. To remedy this, the current research monitored each of four full-scale industrial WWTPs' respective stages for MPs and standard water quality indicators. Plants A and B underwent standard primary and secondary treatments, whereas Plants C and D had tertiary treatment. The investigation surveyed MP abundance, size distribution, shape, and polymer material, in addition to correlations with standard water quality indicators, including pH, biochemical oxygen demand, chemical oxygen demand, total suspended solids, total dissolved solids, and electrical conductivity. Concentrations in the influent ranged from 549 to 823 particles/L. Polymer composition was dominated by nylon (polyamide), primarily as fibers. Primary settling retained 38.8 % of the particles, and the secondary processes added a further 36.8 %, totaling a combined two-stage removal of 71.8 % with effluent levels of 166-233 particles/L. Addition of tertiary treatment increased the removal efficiency to 95.6 %, reducing final discharge levels on average to < 28 particles/L.