Work

Microplastic Retention in Secondary Sewage Sludge: Characterization and Influence of Solid Concentration

Year: 2025

Type: article

Abstract: The majority of microplastics (MPs) removed from urban wastewater during conventional treatments end up in sewage sludge (around 95%). There are not many studies focused on the retention of MPs in secondary sewage sludge. This study explores the amount and kind of MPs retained in secondary sludge from a municipal wastewater treatment plant (WWTP) and the factors affecting the entrapment of MPs within the sludge flocs. The most abundant MPs in the sludges were fibres (61%), and the majority were within the size range of 250–500 μm. In addition, the effect of solid concentration on MP retention in settled sludge was analysed by carrying out a mixing–settling test. Without the addition of any chemicals, a maximum MP retention efficacy of 63% was obtained for a total suspended solids (TSS) concentration of 5.33 g/L. The effect of adding FeCl3 and non-ionic polyacrylamide (PAM) was also investigated, and the percentage of retained MPs increased to values of 82% and 70%, respectively (with only 0.63 g TSS/L). This improvement occurred predominantly in the case of fibres. The results suggest the possibility of adding chemicals before the secondary settling stage as a means of reducing MP contamination in treated water.

Source: Applied Sciences

DOI: 10.3390/app15073557

Authors: Claudio Casella, Daniel Sol, Adriana Laca, Mario Díaz

Institution: Universidad de Oviedo

Language: English

Topic: Microplastics and Plastic Pollution

Subfield: Pollution

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Clean water and sanitation

Open Access status: gold

Estimated APC paid: $2,896