Monte Carlo simulation for estimating microplastic pollution in a municipal wastewater treatment plant

This study investigates microplastic (MP) pollution in influent (W1), effluent (W2), and sludge cake (S) samples from a municipal wastewater treatment plant (WWTP) in Türkiye. Statistical distributions characterizing the properties of MP were derived from the collected data. Annual MP loads were estimated using Monte Carlo simulations with 100,000 replications. Results show that approximately 1.23×1014 MPs/year enter the WWTP via W1, while 6.40×1012 MPs/year and 9.38×1013 MPs/year are discharged through W2 and retained in S, respectively. Simulations conducted over a range of 1–4 years demonstrate the robustness of the model and enable the estimation of MP load across sampling points. Statistical tests revealed significant seasonal and spatial differences in MP concentrations, particularly between summer and winter. These findings confirm the reliability of the simulation approach for assessing MP pollution in WWTPs.