An evaluation of microplastics fate in the wastewater treatment plants: frequency and removal of microplastics by microfiltration membrane

Neda Yahyanezhad,Mohammad Javad Bardi,Hassan Aminirad

doi:10.2166/wpt.2021.036

Neda Yahyanezhad, Mohammad Javad Bardi + Show 1 more

Open Access

https://doi.org/10.2166/wpt.2021.036

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Abstract

Abstract In this research, the fate and removal of microplastics (MPs) entering and leaving a wastewater treatment plant (WWTP) was investigated. Additionally, application of the microfiltration membrane technique for MPs removal was evaluated. In the first phase, the quantity, type and size of the MPs were studied from three different points of the WWTP. The results showed that the average amount of MPs entering into the WWTP, accumulated in the sludge matrix and discharged from the effluent were 206, 183 and 94 MP/L, respectively. The MPs were observed mainly in the forms of fibers, pellets, and fragments, with a proportion of 35%, 39%, 22%, and 34%, 22%, 38%, and 31%, 39%, 37.7% in the influent, effluent and sludge of the WWTP, respectively. It should be noted, a minor amount of foam (2%) and film (0.3%) was also observed. The particle size distribution of the MPs in the effluent of the system was almost identical (6–14% for 1–5,000 μm), while the influent mostly contained particles within 1–100 μm (above 26%) with other particle sizes within 100–5,000 μm (8–17%). Particle size within a range of 500–5,000 μm was abundant in the sludge. In the second phase, a micro-filtration (MF) membrane with a pore size of 0.1 μm was applied to eliminate the MPs from the WWTP effluent. It was observed the application of the MF membrane technique could achieve MPs removal efficiency up to 98% in the effluent of the system.

Highlights

Existence of microplastics (MPs) in wastewater streams has become a major concern for many wastewater treatment plants (WWTP) (Brepols et al 2020; Cuartucci 2020)
The Environmental Protection Agency (EPA) reported that about 80,000– 219,000 tons of MPs are generated in the European countries annually, and they are discarded into the environment (House of Commons Environmental Audit Committee 2016)
It can be noticed that the number of MPs increased in the influent of samples 1, and 2 rather than sample 3 (Table 3). This phenomenon could have been due to climate change, by which rainfalls wash out the MPs into WWTPs (Xia et al 2020)

Summary

Introduction

Existence of microplastics (MPs) in wastewater streams has become a major concern for many wastewater treatment plants (WWTP) (Brepols et al 2020; Cuartucci 2020). MPs can be classified based on their color, shape, and polymer characteristics (Jung et al 2018). MPs can be categorized according to their chemical composition such as applied polymers during the manufacturing process of the origin plastics. The other forms of MPs, known as secondary MPs, can be generated after the breakdown of large plastic wastes or primary MPs into small pieces during a harsh environment (Michielssen et al 1970; Claessens et al 2013). The Environmental Protection Agency (EPA) reported that about 80,000– 219,000 tons of MPs are generated in the European countries annually, and they are discarded into the environment (House of Commons Environmental Audit Committee 2016). The presence of these materials can impose many adverse impacts on the environment

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