Wastewater Treatment Works (WwTW) as a Source of Microplastics in the Aquatic Environment

Abstract

Municipal effluent discharged from wastewater treatment works (WwTW) is suspected to be a significant contributor of microplastics (MP) to the environment as many personal care products contain plastic microbeads. A secondary WwTW (population equivalent 650 000) was sampled for microplastics at different stages of the treatment process to ascertain at what stage in the treatment process the MP are being removed. The influent contained on average 15.70 (±5.23) MP·L(-1). This was reduced to 0.25 (±0.04) MP·L(-1) in the final effluent, a decrease of 98.41%. Despite this large reduction we calculate that this WwTW is releasing 65 million microplastics into the receiving water every day. A significant proportion of the microplastic accumulated in and was removed during the grease removal stage (19.67 (±4.51) MP/2.5 g), it was only in the grease that the much publicised microbeads were found. This study shows that despite the efficient removal rates of MP achieved by this modern treatment plant when dealing with such a large volume of effluent even a modest amount of microplastics being released per liter of effluent could result in significant amounts of microplastics entering the environment. This is the first study to describe in detail the fate of microplastics during the wastewater treatment process.

Sources and Fate of Microplastics in Urban Areas: A Focus on Paris Megacity

“…No fragments in a 400 mL sample, for instance, imply a concentration <2.5 particles L À1 . Larger values were observed in other studies: 430 particles L À1 [19] or 13 particles L À1 [20]. If this variation in fragment concentrations is site dependent or is related to different methodologies, it remains unknown at the moment.…”

“…The results suggested a removal from 83 to 95% of the fiber contamination. Other works showed higher removal efficiencies of MPs by WWTPs, i.e., between 95 and 99% [20,21]. However, all these results are hardly comparable since methods used vary from one study to another.…”

Microplastic-Associated Biofilms: A Comparison of Freshwater and Marine Environments

“…Subsequently, flocculates and settling tanks are used to facilitate separation of sewage sludge from the post-processing effluent prior to a potential disinfection step, also known as advanced tertiary treatment. Studies reporting pathways of microplastics through different wastewater treatment stages are only beginning to emerge [73][74][75], and little is still known about how these stages influence the development of plastisphere microbial communities.…”

Micro- and Nanoplastic Pollution of Freshwater and Wastewater Treatment Systems

“…Loadings from WWTP and the removal efficiency of various treatment stages has also been considered [10,11,13,23,60,72]. For example, in New York, discharges of 109,556, 81,911, and 1,061,953 particles per day were reported for three different WWTP [13], while an average annual discharge of 9 9 10 8 particles was reported from a WWTP in Germany [23].…”