Abstract
Plastic pollution stands as a critical environmental issue. The prevalence of microplastics
(MPs) and nanoplastics in aquatic environments is acknowledged as a global threat that is
directly aligned with the United Nations Sustainable Development Goal (SDG) 14th objective
to reduce global marine plastic pollution. Even though SDG 14 is the only goal directly
addressing plastic pollution through Indicator 14.1.1b (measuring plastic debris density), it
does not include MPs. MPs are plastic particles ranging between 0.05 mm and 5.00mm in size,
contributing significantly to global freshwater and marine plastic litter. MPs encompass a
wide array of polymer compositions, making it difficult to characterise their behaviour as a
single category. This is especially the case in wastewater treatment plants (WWTPs). In South
Africa, municipal WWTPs are not adequately designed or optimised for the effective removal
of MPs, with approximately 80% of wastewater flowing back untreated or partially treated
into the aquatic environment. This study is centred on the prevalence and abundance of MPs
in Gauteng’s Municipal WWTPs and their influx in receiving waters, with the objective of
acquiring in-depth insights into the abundance and transfer of MP from effluent to receiving
aquatic environments. This study highlighted the methods utilised for the sampling and
detection of MPs in wastewater. Bulk wastewater sampling was conducted at nine WWTPs in
Gauteng’s Municipal WWTPs and spanned from October 2022 to July 2023. The sampling was
done to examine the influence of seasonal variations on MP abundance. Light microscopy was
used in the initial phase of sample identification and quantification. In addition, scanning
electron microscope energy-dispersive X-ray spectroscopy (SEM/EDS) was utilised to screen
the sample for non-plastic particles. SEM/EDS was further used to conduct elemental analysis
with the objective of identifying elemental components. Fourier-transform infrared
spectroscopy (FTIR) analysis was employed as the primary method for chemical analysis,
successfully identifying various polymers and discerning their functional group regions. The
findings of this research revealed that fibres and filaments were the predominant shape of
MP particles. These synthetic fibres and filaments mainly originated from polyester, nylon
and acrylic, which constitute the primary materials used in synthetic textiles. Moreover, most
of the MPs in wastewater samples were dark-coloured, particularly black, blue and red. Based
on these data results and hypotheses. Synthetic textiles are identified as the largest
contributors to MPs in WWTPs. In addition, the investigations of this study agreed with the
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Department of Water and Sanitation's 2022 Green Drop report. The latter found that more
than 60% of South Africa's WWTPs have been categorised as ‘poor to critical’, as the average
MP removal efficiency of MPs from WWTPs for this study was observed to be less than 47%.
The findings of this study enhance our understanding of the role played by WWTPs as
transport vectors of MP contaminants. While the realisation of MP remediation may be timeconsuming,
prevention is an immediate possibility. For preventive measures to be effective,
it is crucial to understand the escape routes of MPs, especially those within existing
wastewater management systems.