How effective is the retention of microplastics in horizontal flow sand filters treating stormwater?
Journal article, 2023

Microplastics accumulate in stormwater and can ultimately enter freshwater recipients, and pose a serious risk to aquatic life. This study investigated the effectiveness of lab-scale horizontal flow sand filters of differing lengths (25, 50 and 100 cm) in retaining four types of thermoplastic microplastics commonly occurring in stormwater runoff (polyamide, polyethylene, polypropylene, and polyethylene terephthalate). Despite the differences in particle shape, size and density, the study revealed that more than 98% of the spiked microplastics were retained in all filters, with a slightly increased removal with increased filter length. At a flow rate of 1 mL/min and after one week of operation, 62–84% of the added microplastics agglomerated in the first 2 cm of the filters. The agglomerated microplastics included 96% of high-density fibers. Larger-sized particles were retained in the sand media, while microplastics smaller than 50 μm were more often detected in the effluent. Microplastics were quantified and identified using imaging based micro Fourier Transform Infrared Spectroscopy. The efficient retention of microplastics in low-flow horizontal sand filters, demonstrated by the results, highlights their potential importance for stormwater management. This retention is facilitated by various factors, including microplastic agglomeration, particle sedimentation of heavy fibers and favorable particle-to-media size ratios.

Agglomeration

Stormwater pollution

μ-FTIR analysis

Microplastics

Lab-scale experiment

Porous media filtration

Author

Gabriella Rullander

Uppsala University

Claudia Lorenz

Aalborg University

Roger B. Herbert

Uppsala University

Ann-Margret Hvitt Strömvall

Chalmers, Architecture and Civil Engineering, Water Environment Technology

Jes Vollertsen

Aalborg University

Sahar Dalahmeh

Uppsala University

Journal of Environmental Management

0301-4797 (ISSN) 1095-8630 (eISSN)

Vol. 344 118690

Subject Categories

Water Engineering

Environmental Sciences

DOI

10.1016/j.jenvman.2023.118690

PubMed

37586166

More information

Latest update

9/12/2023