Long-Term Occurrence and Fate of Microplastics in WWTPs: A Case Study in Southwest Europe

Abstract

Microplastic (MP) water pollution is a major problem that the world is currently facing, and wastewater treatment plants (WWTPs) represent one of the main alternatives to reduce the MP release to the environment. Several studies have analysed punctual samples taken throughout the wastewater treatment line. However, there are few long-term studies on the evolution of MPs over time in WWTPs. This work analyses the performance of a WWTP sited in Southwest Europe in relation with annual occurrence and fate of MPs. Samples were monthly taken at different points of the facility (influent, secondary effluent, final effluent, and sludge) and MPs were quantified and characterised by means of stereomicroscopy and FTIR spectrophotometry. The majority of MPs found in wastewater and sludge samples were fragments and fibres. Regarding to the chemical composition, in the water samples, polyethylene (PE), polyethylene terephthalate (PET) and polypropylene (PP) stood out, whereas, in the sludge samples, the main polymers were PET, polyamide (PA) and polystyrene (PS). The MPs more easily removed during the wastewater treatment processes were those with sizes greater than 500 µm. Results showed that the MPs removal was very high during all the period analysed with removal efficiencies between 89% and 95%, so no great variations were found between months. MP concentrations in dry sludge samples ranged between 12 and 39 MPs/g, which represented around 79% of the total MPs removed during the wastewater treatment processes. It is noticeable that a trend between temperature and MPs entrapped in sewage sludge was observed, i.e., higher temperatures entailed higher percentage of retention.

Microplastics in Wastewater by Washing Polyester Fabrics

“…The fact is that the amount of microplastic is highest in warmer conditions than in colder ones. It has been shown that wastewater samples contain fragments of PP and PE, whereas sludge contains PA, PET, and PS, as denser polymers are deposited during the treatment process [ 85 ]. Studies have also shown that a human can ingest between 39,000–520,000 microplastic per year through food and beverages, with levels naturally depending on age and gender [ 86 ].…”

Contribution of household dishwashing to microplastic pollution

“…Most of these microparticles end up in sewage systems which are one of the main culprits of MP release into the environment (Horton et al 2017 ; Padervand et al 2020 ; Petersen and Hubbart 2021 ; Xu et al 2020 ). Certainly, wastewater treatment plants (WWTPs) can remove more than 90% of MPs from wastewater, but this is insufficient, since millions of microplastics are still discharged into the environment every day by each WWTP (Ali et al 2021a , b ; Masiá et al 2020 ; Sol et al 2020 ; Menéndez-Manjón et al 2022 ). More specifically, it has been estimated that a WWTP releases between 0.01 and 2.97 × 10 2 particles per liter of effluent (Ali et al 2021a , b ; Liu et al 2021 ).…”

Identification of microplastic pathways within a typical European urban wastewater system

“…The article presents data on MP contents in municipal sewerage systems of a bigger European city. There are some data on different wastewater treatment plants (WWTP) available in the literature, [30][31][32], but a more comprehensive analysis of the entire municipal wastewater system often not exists. The entire wastewater system must be considered to track down undesirable entry paths into the environment.…”