Plastic as a pollutant of the water environment
The quantities of plastic waste entering the environment are staggering. It has been estimated that up to 12 million tons of plastic litter could be entering the ocean every year. In the lead feature article in the June 2018 issue of National Geographic staff writers Laura Parker and Randy Olson have done an excellent job describing the problems of plastic in the oceans, and the associated issues for uses, product specifications and recycling challenges. Whilst they don’t explicitly say [but we should] it is a classic diffuse pollution issue: weather mobilised transport of contaminants from the air or landscape into the water environment, they have created stark maps showing the major inputs of plastic waste to the oceans, with a scale for inputs in thousands of tonnes per year. Perhaps not surprisingly, the rivers of eastern Asia contribute a disproportionate amount of plastic to the oceans. Rapid economic development out-stripping environmental protection, and expanding very poor populations of megacities probably explains that. That region is a source area for many of the powerful visual images published in the magazine (National Geographic, 06.2018, pp40-69). The guest editor for that issue is record breaking circumnavigator Ellen MacArthur, who has launched a foundation to accelerate the transition to a circular economy, after seeing at first hand the problems. Urging a wholesale shift to a circular economy is certainly the correct primary focus for action; want it now and push hard and consistently to shift business production from multiple mutually exclusive plastic products to ones which can be recycled, as well as encourage re-use by consumers (as is happening).
But in the short and medium term, the plastic waste blowing around the landscapes and getting into watercourses and the sea needs to be captured as close to source as possible. In an earlier foray into this subject we wrote about the use of trash screens in South Africa and USA on stormwater drains, and I noted that whilst I was impressed by the collection and removal of the vast litter accumulations (especially in the California site), it didn’t seem like much of an innovation to me at the time. My first thought more recently was yes, we need to add trash screens to SUDS design. Ironic that one of the grumbles of many detractors of swales/detention basins and ponds is that “they are litter traps” . Well, the oceans publicity will perhaps have an additional benefit and encourage more litter collection form landscapes sumps such as SUDS features. It’s not a negative failure of the technology that the pollution capture includes plastic and other litter. As regards plastic, the next research topic for SUDS (LID/WSUD/Urban BMPs etc) is how effective they are capturing microplastic contamination. How will that affect sediment disposal/recovery? What to do with the sediment? If you have research underway or published on this please get in touch and we shall feature it in a future issue please.
Reproduced with permission from the Summer 2018 issue of the newsletter of the IWA Diffuse Pollution & Eutrophication Specialist Group
Chair, IWA Land Use & Water Quality Task Group