Development and Optimization of Methods for Microplastic Analysis in Drinking Water: A Case Study of Glenmore Drinking Water Treatment Plant, Calgary

In recent years, the presence of microplastics (MPs) in drinking water has garnered increasing attention due to their potential impact on human health. MPs are plastic particles ranging from 1 µm to 5 mm and can have varying size, morphology, and chemical composition. Although their full impact on human health remains unclear, characterizing the MPs and understanding their fate throughout the drinking water production process is crucial to managing potential risks. This thesis investigates the presence of MPs larger than 10 µm in raw and treated water from the Glenmore drinking water treatment plant (G-DWTP), one of the two facilities supplying drinking water to the City of Calgary. To facilitate the study, a novel sample collection device was developed to collect large (~1000 L) sample volumes for analysis. Experiments were conducted to improve particle recoveries by evaluating the application of high-pressure flushing (HPF) and ultrasonic treatment. Additionally, the optimal magnification for Raman microspectroscopic analysis of different-sized particles was assessed. Monthly samples from April–September 2024 were collected from both raw and treated drinking water. After pretreatment, samples were stained with Nile Red and suspected MPs were identified by fluorescence microscopy and analyzed using Raman microscopy for identification of their polymer composition. For sample pretreatment, the optimal procedure involved assembling the filter support and mesh together, followed by a one-minute ultrasonic treatment and HPF. This pretreatment method yielded differing recoveries across various size ranges: 76.7 ± 20.9% for 250-300 µm, 75.3 ± 7.8% for 106-125 µm, 64.6 ± 13.3% for 63-70 µm, and 26.3 ± 7.1% for 10-20 µm. The optimal magnification was 10x for particles larger than 90 µm and 50x for those smaller than 90 µm. The measured abundance of MPs in the raw water was 1.9 ± 2.8 MPs/m3, with a slight increase to 3.1 ± 3.1 MPs/m3 in the treated water. Among the detected MPs, particles in the size range of 1-80 µm accounted for 73%. Three morphological types of MPs were identified: fragments (89%), beads (8%), and fibers (3%). The predominant polymer types were polypropylene, polystyrene, polyethylene, and polyvinyl chloride. In terms of color, white and transparent MPs were the most common, comprising 54%, and 32% of the total, respectively. Overall, MP abundance at the G-DWTP was relatively low compared to other studies. This thesis represents the first assessment of MPs in the G-DWTP. While it provides baseline information, establishing a monitoring plan is important to adequately assess MP risks. Finally, acceptable particle recoveries achieved through the design of the sampling equipment and methods development offer valuable reference points for MPs monitoring activities at other DWTPs in Calgary.

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