Title
Transport and fate of microplastic particles in wastewater treatment plants
Author
Steve A. Carr, Jin Li , Arnold G. Tesoro
Year
2016
Journal
Water Research Volume 91, 15 March 2016, Pages 174-182
Abstract
Municipal wastewater treatment plants (WWTPs) are frequently suspected as significant point sources or
conduits of microplastics to the environment. To directly investigate these suspicions, effluent discharges
from seven tertiary plants and one secondary plant in Southern California were studied. The study also
looked at influent loads, particle size/type, conveyance, and removal at these wastewater treatment
facilities. Over 0.189 million liters of effluent at each of the seven tertiary plants were filtered using an
assembled stack of sieves with mesh sizes between 400 and 45 mm. Additionally, the surface of 28.4
million liters of final effluent at three tertiary plants was skimmed using a 125 mm filtering assembly. The
results suggest that tertiary effluent is not a significant source of microplastics and that these plastic
pollutants are effectively removed during the skimming and settling treatment processes. However, at a
downstream secondary plant, an average of one micro-particle in every 1.14 thousand liters of final
effluent was counted. The majority of microplastics identified in this study had a profile (color, shape,
and size) similar to the blue polyethylene particles present in toothpaste formulations. Existing treatment processes were determined to be very effective for removal of microplastic contaminants entering
typical municipal WWTPs.
Instrument
FTIR 4600
Keywords
Microplastic pollutantsWastewater treatmentLarge-volume samplingEffluent dischargeCosmetic polyethyleneSurface filtering