Editorial Feature

Wastewater Treatment to Reduce Microplastic-Associated Antimicrobial Resistance

This article discusses the effectiveness of the wastewater treatment process combined with a constructed wetland (CW) in substantially reducing the antimicrobial resistance (AMR) and pathogenic load carried with microplastics (MPs) from sewage.

microplastics, microplastic pollution, wastewater treatment for microplastics, microplastic antimicrobial resistance

Image Credit: wonderisland/Shutterstock.com

Effects of MPs on Human Health

Ever-increasing plastic pollution is severely damaging aquatic life and marine ecosystems and leading to uncontrolled transmission of human-induced AMR. AMR is one of the leading global public health problems, causing more annual fatalities than malaria or human immunodeficiency virus (HIV).

MPs, a type of plastic pollution, are micrometer to millimeter size plastic particles that adversely affect both terrestrial and aquatic life by disrupting the immune and digestive systems and the reproductive process. Thus, MPs pose significant risks to human health.

MPs are colonized by microbial biofilms, including bacteria populations with high AMR gene abundance, specifically in antibiotic-rich wastewater. Both AMR bacteria and MPs are prevalent in wastewater, with wastewater treatment plants (WWTPs) acting as the hub of these contaminants.

Limitations of Wastewater Treatment Plants in Reducing MP-Associated AMR Load

WWTPs are not specifically designed for complete AMR/MP elimination. Thus, the MP removal by WWTPs depends on the treatment technology and stage. For instance, 50% and over 99% MP removal can be achieved through basic secondary treatment and advanced tertiary treatment, respectively.

Although several conventional large municipal WWTPs have achieved 90-99.9% AMR gene removal, only advanced treatment, such as membrane filtration or ozonation, can lead to 99.99% AMR removal.

However, the WWTP effluent can still have more than 104 AMR gene copies (GC) mL-1 for the most prevalent AMR genes, such as sulfonamide or tetracycline resistance, which is 1-3 orders of magnitude higher compared to the background AMR gene concentration in upstream WWTPs.

Importance of CWs for AMR and MP Removal

Non-conventional treatments such as CWs can play a critical role in addressing the risks of AMR and MPs. CWs are low-energy, nature-based water treatment technology that imitates the purification process of natural wetlands.

Although CWs have several limitations due to low-tech operation and design, they can treat different types of municipal, agricultural, and industrial wastewater. In CWs, MP removal from wastewater streams varies between 20-95%, while AMR removal is comparable to conventional WWTPs.

Studies have demonstrated that MPs from WWTP effluent possess a uniquely different bacterial community compared to the planktonic community, including AMR genes and pathogenic bacteria. MPs in wastewater effluent increased the survivability and spread of pathogens.

Additionally, studies also displayed that disinfection has little effect on MP-associated biofilm composition and their ability to accommodate intact AMR. Thus, the risk of AMR spread is increased through MPs released by WWTPs.

However, most of these studies have been limited to single-step treatment, single-step incubation times, or laboratory settings. Although few field studies have been performed, none of them have evaluated time-dependent colonization dynamics or the role of CW systems in mitigating pathogen and AMR hazards due to MPs.

Recent Studies

In a recent study published in the journal Water Research, researchers investigated the establishment and changes in MP-associated biofilm and AMR during a full-scale conventional 2100 population equivalent wastewater treatment process coupled with free water surface polishing CW.

The objective of the study was to assess the combined effect of colonization time and treatment step-dependent dynamics on MP-associated pathogens and AMR in wastewater.

Downstream wastewater effluent treatment through a polishing CW can alter the biofilm composition and AMR levels of MPs and minimize the synergy between AMR spread and MPs pollution.

This hypothesis was investigated by successfully incubating batches of sterile microplastics and transferring them between various stages of a full-scale wastewater treatment process equipped with a CW at different incubation times and then evaluating the AMR evolution and colonization patterns on sterile MPs to determine the changes in these patterns along multiple stages.

Sequential microplastic colonization experiments were performed at different stages, including in raw sewage, treated effluent, and the CW. Researchers also assessed the feasibility of using CW either as a polishing step or as a primary recipient of sewage-inoculated MPs.

Four types of plastics were used for the colonization experiment, including polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and high-density polyethylene (HDPE). These plastics represent the major polymer types present in municipal wastewater. 

Bacterial 16Svedberg ribosomal ribonucleic acid (16S rRNA) gene sequencing was performed for qualitative bacterial community analysis, while quantitative polymerase chain reaction (qPCR) was employed for quantitative analysis of bacterial biomass, a human fecal marker, and AMR genes.

The study demonstrated that CW as a polishing step can effectively neutralize the MP-associated AMR load transferred from the WWTP. Increased MP incubation time within the CW and WWTP eliminated AMR contamination and potentially pathogenic bacteria belonging to the genera Pseudomonas, Arcobacter, Acinetobacter, and Klebsiella.

MP-associated AMR also displayed gene-specific dynamics, as Streptococcus, Aeromonas, and Klebsiella were the major pathogenic genera that correlated with the presence of AMR in MP biofilms.

Although the AMR load and pathogens reduced in MPs after treatment from WWTPs and CWs, these plastic particles still acted as a source of fish pathogens, including Lactococcus, Stenotrophomonas, and Aeromonas, which can impact the downstream ecosystems.

CW, as a primary treatment unit, consistently reduced AMR without being impacted by the retention duration of MPs. However, the effect of the CW varied during the elimination of pathogenic genera.

Additionally, CW as a primary treatment step was less effective in neutralizing pathogens and AMR on MPs compared to WWTP equipped with an oxidation ditch. However, a 99% reduction in pathogenic and AMR load carried from MPs from sewage was achieved when the WWTP was used in combination with CW.

More from AZoM: Polymer Innovations in 3D Printing

References and Further Reading

Bydalek, F., Webster, G., Barden, R., Weightman, A. J., Kasprzyk-Hordern, B., & Wenk, J. (2023). Microplastic biofilm, associated pathogen and antimicrobial resistance dynamics through a wastewater treatment process incorporating a constructed wetland. Water Research, 235, 119936. https://doi.org/10.1016/j.watres.2023.119936

Bydalek, F., Ifayemi, D., Reynolds, L., Barden, R., Kasprzyk-Hordern, B., Wenk, J. (2023). Microplastic dynamics in a free water surface constructed wetland. Science of The Total Environment, 858, 160113. https://doi.org/10.1016/J.SCITOTENV.2022.160113

Lai, K.P., Tsang, C.F., Li, L., Yu, R.M.K., Kong, R.Y.C. (2022). Microplastics act as a carrier for wastewater-borne pathogenic bacteria in sewage. Chemosphere, 301, 134692. https://doi.org/10.1016/J.CHEMOSPHERE.2022.13469

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Samudrapom Dam

Written by

Samudrapom Dam

Samudrapom Dam is a freelance scientific and business writer based in Kolkata, India. He has been writing articles related to business and scientific topics for more than one and a half years. He has extensive experience in writing about advanced technologies, information technology, machinery, metals and metal products, clean technologies, finance and banking, automotive, household products, and the aerospace industry. He is passionate about the latest developments in advanced technologies, the ways these developments can be implemented in a real-world situation, and how these developments can positively impact common people.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Dam, Samudrapom. (2023, May 12). Wastewater Treatment to Reduce Microplastic-Associated Antimicrobial Resistance. AZoM. Retrieved on September 24, 2023 from https://www.azom.com/article.aspx?ArticleID=22677.

  • MLA

    Dam, Samudrapom. "Wastewater Treatment to Reduce Microplastic-Associated Antimicrobial Resistance". AZoM. 24 September 2023. <https://www.azom.com/article.aspx?ArticleID=22677>.

  • Chicago

    Dam, Samudrapom. "Wastewater Treatment to Reduce Microplastic-Associated Antimicrobial Resistance". AZoM. https://www.azom.com/article.aspx?ArticleID=22677. (accessed September 24, 2023).

  • Harvard

    Dam, Samudrapom. 2023. Wastewater Treatment to Reduce Microplastic-Associated Antimicrobial Resistance. AZoM, viewed 24 September 2023, https://www.azom.com/article.aspx?ArticleID=22677.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Your comment type