Electro-oxidation assisted biodegradation of microplastics
- Nymphe
- 12 hours ago
- 4 min read
Electro-oxidation assisted biodegradation of microplastics is a technology that combines Electro-Fenton oxidation to functionalize microplastics, enhancing their biodegradability and enabling subsequent biological degradation.
Objective:
The objective is to achieve effective removal of microplastics from WWTP effluents. Through the biological degradation of these persistent particles, the process offers a sustainable treatment solution, while also preventing their accumulation in residual streams that require proper disposal or in sludge. The target pollutant is persistent microplastics that remain after conventional treatment processes, especially following tertiary treatment. Therefore, this technology is proposed as a quaternary treatment alternative specifically targeting microplastic pollutants.
WASTEWATER TECHNOLOGY: Electro-oxidation + biodegradation of microplastics
Technology description:
The treatment is designed to integrate two complementary processes: Electro-Fenton oxidation and biological degradation to effectively remove microplastics that conventional tertiary treatments often fail to eliminate (Figure 1).
The first step involves applying Electro-Fenton oxidation under mild conditions for 5 hours, using an iron concentration of 10 ppm and a current density of 5 A/m². The Fenton reaction consists of the in-situ production of hydroxyl radicals (•OH) by the traditional reaction of hydrogen peroxide with iron (II). These highly reactive radicals attack the surface of microplastic particles, inducing functionalization by introducing oxygen-containing groups.
This oxidation alters the physicochemical properties of microplastics, such as increasing their surface hydrophilicity and creating reactive sites that improve their affinity for microbial degradation. In addition, this attack may also solubilize some microplastic fractions or their additives, consequently enhancing the bioavailability of these compounds. On the other hand, the electrochemical reactions coupled with the Fenton reactions enhance the sustainability of the treatment by enabling in-situ hydrogen peroxide production and the recycling of iron (III) (formed after the Fenton reaction) back to iron (II).
Following electrochemical treatment, the functionalized microplastics undergo biological degradation in an aerated bioreactor utilizing specific microbial consortia capable of metabolizing the polymers. This biological step takes advantage of the increased biodegradability conferred by the Electro-Fenton pre-treatment, enabling microbes to more efficiently break down microplastic polymers into complete mineralization.
This two-step process significantly enhances the overall removal efficiency of microplastics from WWTP effluents.
TRL
The TRL of the combined Electro-Fenton and biological degradation technology is currently at level 3. At this stage, the treatment has been tested using real microplastics and actual WWTP effluents, primarily to understand the mechanisms involved and evaluate the process's potential effectiveness. However, Electro-Fenton oxidation and biological degradation are already well-established technologies for treating other water contaminants (TRL 9). This work aims to integrate these proven methods to specifically target the effective removal of microplastics.
Currently, the main strategies for microplastic removal in WWTPs rely on physical separation rather than complete degradation. Consequently, microplastics often accumulate in sludge, which is frequently used as fertiliser in agriculture, leading to secondary soil contamination. The novelty of this approach lies in the degradation of microplastics as the target contaminant. This technology involves the combined, synergistic use of Electro-Fenton oxidation under mild conditions to functionalise microplastics and enhance their biodegradability, followed by biological degradation aimed at achieving complete mineralisation. This integrated process goes beyond conventional treatments by addressing not just separation, but also the effective elimination of microplastics, thereby reducing their long-term environmental persistence.
Understanding the mechanisms and identifying the potential of this combined treatment makes its implementation both practical and highly effective, offering a promising quaternary treatment solution for WWTPs to combat microplastic pollution.
Results of technology development and implementation:
The results highlight the potential of the combined treatment, particularly in addressing polyethylene (PE), one of the most recalcitrant polymers. The Electro-Fenton pre-treatment significantly enhanced the biodegradability of PE. Tests were carried out using both synthetic granular PE and real PE extracted from an agricultural site, resulting in a threefold and twofold increase in biodegradability, respectively. This enhancement was confirmed by evidence of surface functionalization. In addition, the treatment was applied to real WWTP effluent containing PE particles. After 21 days of biological treatment in batch mode, over 80% of the PE particles were removed.
These findings confirm both the effectiveness and feasibility of the proposed technology for microplastic removal. The enhanced polymer biodegradability and high removal rates achieved under realistic conditions support its potential as an advanced solution for wastewater treatment, specifically targeting persistent microplastics. In addition, these encouraging results suggest that the integration of a microfiltration step at the bioreactor outlet could further increase removal efficiency up to 100% and reduce the reaction time. This would enable the system to operate in continuous flow mode, improving its scalability and making it more suitable for real-world applications.
WASTEWATER TECHNOLOGY: Electro-oxidation + biodegradation of microplastics
Speaker: Dr. Sebastià Puig, Associate Professor at the University of Girona
Interviewer: Agnieszka Sznyk, PhD, President of the Board, The Institute of Innovation and Responsible Development, INNOWO.
In our Technology Booklet, we showcase 10 solutions currently under development:
4 wastewater treatment technologies
3 soil remediation technologies
3 microbiome modelling approaches
Read the full technology overview: https://www.nympheproject.eu/technologies
This interview is a part of Nymphe project (New system-driven bioremediation of polluted habitats and environment)
More about project: https://www.nympheproject.eu/
Project funded by the European Union
Grant Agreement ID: 101060625
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