Enhancing Microplastics Removal from Wastewater Using Electro-Coagulation and Granule-Activated Carbon with Thermal Regeneration

Keug Tae Kim,Sanghwa Park

doi:10.3390/pr9040617

Keug Tae Kim, Sanghwa Park

Open Access

https://doi.org/10.3390/pr9040617

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Abstract

Discharge from sewage treatment plants (STPs) is a significant pathway of entry for microplastics (MPs) to the environment. Therefore, STPs should be considered as an important barrier to the distribution and circulation of MPs in the aquatic environment. In this study, the fate and material-specific properties of MPs were investigated in an STP-equipped and granule-activated carbon (GAC) tower with a thermal regeneration system. This system functioned with a tertiary treatment unit. The GAC with thermal regeneration removed 92.8% of MPs and was useful for removing MPs with a specific gravity less than that of water and with a size of 20–50 µm, which had negligible removal in the conventional STP process. In addition, a lab-scale electric-coagulation experiment was conducted to examine its potential utility as a pretreatment process for further enhancing the removal efficiency of MPs by GAC. After 30 min of electro-coagulation using aluminum electrodes, 90% of MPs were converted into separable flocs by centrifugation. These flocs may be effectively removed by GAC or other tertiary treatment steps. This study demonstrates that GAC with thermal regeneration is a tertiary process that can efficiently prohibit the release of MPs from STPs and circulation of MPs in the natural environment.

Highlights

Microplastics (MPs) in the aquatic environment are of increasing concern because they pose a threat to the aquatic ecosystem and human population [1]
Discharge from an sewage treatment plants (STPs) is an important pathway for microplastics to enter water supply systems and the environment
Membrane biological reactor (MBR)-based methods are the most well-known methods for MP removal, these methods have the disadvantages of high costs for installation and operation as well as short life spans

Summary

Introduction

Microplastics (MPs) in the aquatic environment are of increasing concern because they pose a threat to the aquatic ecosystem and human population [1]. Depending on the requirements of the final product, polymers can be mixed with different additives to enhance their performance. These include plasticizers, antioxidants, flame retardants, ultraviolet stabilizers, lubricants, and colorants, to customize the characteristics of plastics (e.g., flexibility, strength, resistance to heat, electrical isolation, etc.) [2]. The most common additives used in the fabrication process and found in the microplastic debris collected in environmental surveys are phthalates, bisphenol A, polybrominated diphenyl ethers, and nonylphenols [3]. MPs may exhibit a considerable potential to transfer water pollutants to aquatic ecosystems and human health

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