Abstract
It is now well established that the oceans contain significant accumulations of plastic debris but only very recently have studies began to look at sources of microplastics (MPs) in river catchments. This work measured MPs up- and downstream of six wastewater treatment plants (WWTPs) in different catchments with varying characteristics and found that all led to an increase in MPs in rivers. Nevertheless, the data collected indicated that there were other important sources of MPs in the catchments studied and that these may include atmospheric deposition, agricultural land to which sewage sludge has been applied, and diffuse release of secondary MPs following the breakdown of larger plastic items. MPs were comprised mainly of fibres, fragments, and flakes with pellets and beads only dominating at one site. Variation in MP pollution occurred over time and this difference was greater at some sites than others. A key research need is the further study of MP sources in river catchments to facilitate management efforts to reduce their presence in freshwater and marine environments.
Highlights
The ‘plastic age’ comes with significant benefits and problems, including the accumulation of microplastics (MPs) in the aquatic environment (Wagner et al 2014)
It has been postulated that wastewater treatment plants (WWTPs) are the main source of MPs to river catchments (Roex et al 2013) as they receive waste from industries manufacturing and using MPs, for instance as scrubbers in cleaning and cosmetic products, as well as domestic effluent from households using products containing MPs (Zbyszewski et al 2014; Eerkes-Medrano et al 2015)
Contribution of wastewater treatment plants to microplastic loading of receiving waters The quantity of microplastics generally increased downstream of each WWTP monitored with the mean ratio up- and downstream always being greater than 1 (Fig. 1)
Summary
The ‘plastic age’ comes with significant benefits and problems, including the accumulation of microplastics (MPs) in the aquatic environment (Wagner et al 2014). Various reasons have been postulated as to why research has focused almost entirely on the marine environment, including MPs being more visible on oceans and beaches and effects having been observed in marine biota (Ryan et al 2009). MPs are defined as pieces of plastic with a diameter < 5 mm and can come from a diverse range of sources, including personal care products, textiles, and Responsible editor: Philippe Garrigues packaging. It has been postulated that wastewater treatment plants (WWTPs) are the main source of MPs to river catchments (Roex et al 2013) as they receive waste from industries manufacturing and using MPs, for instance as scrubbers in cleaning and cosmetic products, as well as domestic effluent from households using products containing MPs (Zbyszewski et al 2014; Eerkes-Medrano et al 2015).
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