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New Method Uses Chemical Solution to Measure Microplastics in Sewage

Researchers have started closely analyzing human sewage to identify how best to quantify hidden and potentially harmful plastics.

This image is generated by siMPle, an FTIR particle-analysis software, after comparison of the acquired particles spectra with a reference database. Image Credit: University of Portsmouth.

The measurement and counting of microplastics differ from one place to another. Therefore, there is no standard understanding of the weight of the issue. Until researchers can come to a consensus on a single way to measure them, life on land and sea will continue to consume an immeasurable amount of plastic, thereby affecting health for several generations.

A new study by researchers at the University of Portsmouth and recently published in Analytical and Bioanalytical Chemistry has investigated one technique that involves using a chemical solution known as “Fenton reagent” to eliminate organic matter from sewage. The study identified that it offers major benefits in terms of processing costs and times when compared to other existing methods of testing.

According to Dr Fay Couceiro, Project Lead and Senior Research Fellow in Biogeochemistry at the University of Portsmouth, “Multiple digestion with Fenton reagent involves mixing the sewage with hydrogen peroxide and iron sulphide multiple times to breakdown the organic matter. When followed by density separation, where you float off the plastics from everything else, it provides a cleaner sample so the size and type of microplastic can be determined with much less interference.”

Having some idea of the amount of microplastics in the environment is key to understanding and stopping the potential harmful impacts that this new category of emerging pollutants could have on life on earth. The need for protocols that are robust, simple and reliable together with their standardisation are of crucial importance in the fight against plastic pollution.

Steve Fletcher, Professor and Director, Revolution Plastics Initiative, University of Portsmouth

The target of the research is to detect microplastics in the sub-hundred-micron size range, which are usually missed due to their tiny size. However, they have potentially higher health risks related to them. Particles of this size also have limited data available from earlier wastewater research.

The researchers demonstrated the value of this method by mixing samples of raw sewage, final effluent, and sludge with two different sizes and types of microplastics. The multiple digestion with Fenton reagent method exhibited optimal recovery of the added microplastics.

Given the different stages needed for microplastics separation, time is a limiting factor when it comes to sample processing. The multiple digestion with Fenton reagent is a low-cost and time-efficient procedure than other existing methods when analyzing large numbers of samples.

The Fenton reagent method used in this study has huge potential for bringing about a much needed standardisation of the measuring of microplastics. Without being able to compare and contrast concentrations of microplastics, our ability to make significant strides forward in limiting pollution will be restricted. We would welcome further research that could investigate other types of plastics and the recovering of even smaller plastic particles.

Dr Fay Couceiro, Senior Research Fellow in Biogeochemistry, University of Portsmouth

Journal Reference:

Cunsolo, S., et al. (2021) Optimising sample preparation for FTIR-based microplastic analysis in wastewater and sludge samples: multiple digestions. Analytical and Bioanalytical Chemistry. doi.org/10.1007/s00216-021-03331-6.

Source: https://www.port.ac.uk/

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