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Investigating biodegradation of polyethylene and polypropylene microplastics in Tehran DWTPs
Summary
This Iranian study tested whether bacteria naturally present in drinking water treatment plant source water could biodegrade polyethylene (PE) and polypropylene (PP) microplastics. Three bacterial strains caused measurable structural, chemical, and mass changes in both plastics, with one strain achieving up to 32.6% weight loss in PP microplastics over the study period. While biodegradation rates remain slow relative to the scale of plastic pollution, identifying indigenous bacteria capable of attacking plastics in drinking water systems offers potential pathways for bioremediation.
Microplastic (MP) pollution is a growing concern and various methods are being sought to alleviate the level of pollution worldwide. This study investigates the biodegradation capacity of MPs by indigenous microorganisms of raw water from Tehran drinking water treatment plants. By exposing polypropylene (PP) and polyethylene (PE) MPs to selected microbial colonies, structural, morphological, and chemical changes were detected by scanning electron microscope (SEM), cell weight measurement, Fourier transform infrared (FTIR), Raman spectroscopy test, and thermal gravimetric analysis (TGA). Selected bacterial strains include Pseudomonas protegens strain (A), Bacillus cereus strain (B), and Pseudomonas protegens strain (C). SEM analysis showed roughness and cracks on PP MPs exposed to strains A and C. However, PE MPs exposed to strain B faced limited degradation. In samples related to strain A, the Raman spectrum was completely changed, and a new chemical structure was created. Both TGA and FTIR analysis confirmed changes detected by Raman analysis of PP and PE MPs in chemical changes in this study. The results of cell dry weight loss for microbial strains A, B, and C were 13.5, 38.6, and 25.6%, respectively. Moreover, MPs weight loss was recorded at 32.6% for PP MPs with strain A, 13.3% for PE MPs with strain B, and 25.6% for PP MPs with strain C.