Wastewater treatment plants are known to contribute to microplastic (MP) pollution in freshwater and terrestrial environments, but studies on MP abundance in sludge are scarce. We aimed to provide an initial estimate of mass loads of MPs in sludge by compiling literature (<i>n</i>= 7) reported particle counts and dimensional data and then converting these into units of MPs mass per sludge mass. Conversion factors used were informed by the average weight of plastic beads, particles, pellets, films, and fibers. Data on MP abundance were found to be inconsistent with respect to analytical methods and quantification units used. Polymer types present in sludge were identified in 57% of studies. The average weight ± standard deviation in units of mg by MP class was 1.5 ± 0.5 for fibers, 12 ± 4 for particles, 55 ± 1 for fragments, 0.3 ± 0.1 for films, 13 ± 1 for plastic pellets and 3.4 ± 0.1 for microbeads. Based on the weights obtained, the mass loadings of MPs in sludge in units of mass per mass of dry weight sludge were highest for China followed by the United States, Finland, the Netherlands, and Sweden. Mass loading data underscore the significance of the MP pollution problem and found significant geospatial variation worldwide.

Municipal sewage sludge as a source of microplastics in the environment

2019 Fall National Meeting

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