Occurrence, identification and removal of microplastics in a wastewater treatment plant compared to an advanced MBR technology: Full-scale pilot plant

Abstract

Microplastics are of increasing interest as one of the most important threats to the natural environment and aquatic life. One of the main pathways of microplastics entering the aquatic and terrestrial environment are wastewater treatment plants. The aim of this study was to investigate the occurrence and removal of MPs in both wastewater and sludge from an MBR-based and a WWTP. The focus is on the amount of microplastics emitted into the environment, the efficiency of removal in wastewater treatment plants and how their operation and design, could be improved to reduce the presence of these pollutants in the effluent. The results showed that the influent (SI) had mean concentration of 507 ± 70 MPs L-1, in the reactor tank (SRS) the concentration increases to 1.77 × 107 ± 1.61 × 107 MPs kg-1 (dw) and in the permeate (SP) the estimated amount of microplastics decreased to 1.58 ± 1.08 MPs L-1. This is a removal efficiency of 99.69%, with respect to the estimated average MPs. After the clarifier (SC) and sand filtration (SSF) a mean of 17.38 ± 4.71 MPs L-1 and 2.93 ± 1.50 MPs L-1 respectively were found, resulting in an efficiency of 96.58% and 99.42%, respectively, regarding the inlet water of the treatment plant. The two predominant forms in all samples (except for SCS) were fragments and fibers. In total 25 types of polymers were detected, and only 5 resulted in all types of samples, the most detected polymer families were Acrylates and Polyethylenes.