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. 2020 Jun 10:720:137383.
doi: 10.1016/j.scitotenv.2020.137383. Epub 2020 Feb 19.

Removal efficiency of micro- and nanoplastics (180 nm-125 μm) during drinking water treatment

Yongli Zhang  1 , Allison Diehl  2 , Ashton Lewandowski  3 , Kishore Gopalakrishnan  2 , Tracie Baker  4
Affiliations

Removal efficiency of micro- and nanoplastics (180 nm-125 μm) during drinking water treatment

Yongli Zhang et al. Sci Total Environ. .

Abstract

This study investigated the removal efficiency of micro- and nanoplastics (180 nm-125 μm) during drinking water treatment, particularly coagulation/flocculation combined with sedimentation (CFS) and granular filtration under ordinary working conditions at water treatment plants (WTPs). It also studied the interactions between biofilms and microplastics and the consequential impact on treatment efficiency. Generally, CFS was not sufficient to remove micro- and nanoplastics. The sedimentation rate of clean plastics was lower than 2.0% for all different sizes of plastic particles with coagulant Al2(SO4)3. Even with the addition of coagulant aid (PolyDADMAC), the highest removal was only 13.6% for 45-53 μm of particles. In contrast, granular filtration was much more effective at filtering out micro- and nanoplastics, from 86.9% to nearly complete removal (99.9% for particles larger than 100 μm). However, there existed a critical size (10-20 μm) where a significant lower removal (86.9%) was observed. Biofilms were easily formed on microplastics. In addition, biofilm formation significantly increased the removal efficiency of CFS treatment from <2.0% to 16.5%. This work provides new knowledge to better understand the fate and transport of emerging micro- and nanoplastic pollutants during drinking water treatment, which is of increasing concern due to the potential human exposure to micro- and nanoplastics in drinking water.

Keywords: Biofilm; Coagulation/flocculation/sedimentation; Filtration; Micro-and nanoplastics; Water treatment.

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Conflict of interest statement

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1:
Figure 1:
Drinking water treatment processes adopted in the Detroit WTP. Coagulation/flocculation combined with sedimentation (CFS) and filtration were chosen to study the removal efficiency of micro- and nanoplastics.
Figure 2:
Figure 2:
The removal efficiency of plastic particles during the filtration process.
Figure 3:
Figure 3:
Interactions of microplastics and biofilms. Left, within 4 days, biofilms were observed on microplastics; Right, more biofilms were formed at day 7. Blue arrows, biofilms on microplastics.
Figure 4:
Figure 4:
The removal efficiency of plastic particles (45 – 53 μm) with and without biofilm formation during CFS and filtration.
See this image and copyright information in PMC

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