Microplastics continue to receive increased attention because of observed accumulation in marine environments. While microplastics have been found in several water bodies, the exact magnitude of accumulation and any associated risks have remained controversial. The lack of standard methodology for microplastic extraction has served to undermine reported microplastic concentrations and hinder the ability to determine microplastic pollution sources. Wastewater, thought by some to be a major source, offers a complex chemical matrix that requires special consideration during microplastic extraction. A wide variety of methods have been commonly used to extract and quantify microplastics, most of which are known to include implicit user bias and/or require highly specialized instrumentation.  The objective of this study was to determine the best available method for analyzing municipal wastewater samples in preparation for a large scale sampling campaign. Different methods for quantifying microplastics were analyzed for accuracy and feasibility with expected time and cost constraints. A sample preparation procedure using catalyzed wet peroxidation oxidation, density separation, and cellulase treatment retained a minimum of 85% of total spiked microplastics during control testing. After extraction, samples from the Lawrence, KS wastewater treatment plant were analyzed using FTIR, Raman, EDX and XPS. FTIR was shown to be the most time efficient (with the most data obtained per analysis time) due to the linear array detector and established microplastic libraries; however, all chemical analysis methods required subsampling to maintain feasible processing time and cost. Newer FTIR and Raman technology could minimize the need for subsampling but will require large capital investment. Microscopic techniques, both visual inspection and Nile Red staining, were used on the same samples to gauge the error in comparison to the quantification via chemical analysis. Quantifying particles stained with Nile Red could serve as a surrogate parameter, giving results accurate to within 15% of actual concentrations. Based on these trials, both FTIR Linear Array and Nile Red staining appear to be suitable for high-throughput quantification of microplastics within wastewater samples.

Reliably quantifying microplastics within a wastewater matrix

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.