Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | XXXX 20XX | 13 the water and wastewater sector do to help address the issue? Sources of microplastics Mention microplastics to the average member of the public and they will tend to think of tiny plastic pellets that have been intentionally added to products – such as microbeads in cosmetics, which were the subject of a UK ban which came into force in January 2018. However, there are other categories that contribute much more significantly to the total load of microplastic - including thin plastic fibres that detach from synthetic clothing during washing, and plastic flakes that are created when larger items of plastic packaging waste break down. Plastic-based items being flushed down the toilet - such as wet wipes and plastic-stemmed cotton buds and sanitary products - can contribute to the problem, as can industrial discharges to sewers, and even tyre fragments and road paint from roads when there is surface water run-off to combined sewers. One revealing study from the Univer- sity of Leeds, published in June 2018, analysed the microplastic concentrations found in 28 river water samples across six field sites in Northern England, upstream and downstream of wastewater treatment plants. It categorised the types of micro- plastics found into pellets/beads, fibres and fragments/flakes. Fragments and fibres made up nearly 90 per cent of the microplastic found in the river samples. "By categorising the types of micro- plastics, we can identify what aspects of our lifestyle are contributing to river pollution," said Dr Paul Kay of the School of Geography at Leeds, author of the research. "Not that long ago microbeads in toiletries and cosmetics were the micro- plastics getting all the public attention. Seeing the amount of plastic microfibres from clothing and textiles polluting our rivers, we need to think seriously about the role of our synthetic fabrics in long- term environmental harm." Domestic and commercial wastewater is certainly a major route for microplastics entering the environment – but by no means the exclusive one. When compar- ing the samples upstream of the wastewa- ter treatment plants with those down- stream, the Leeds study found that all of the plants were linked to an increase in microplastics in the rivers – on average up to three times higher, but in one instance by a factor of 69. "Finding key entry points of microplas- tics, such as wastewater treatment plants, can provide focus points to combating their distribution," said Dr Kay. "However, pervasive microplastics were also found in our upstream water samples. So while strengthening environmental procedures at treatment plants could be a big step in halting their spread, we cannot ignore the other ways microplastics are getting into our rivers." Microfibres and source control Environmental charity Hubbub recently launched a campaign to raise awareness of the plastic microfibres that are shed into wastewater when clothes made from materials such as nylon, acrylic or polyes- ter are washed. According to the charity, half a million tonnes of plastic microfibres a year are now ending up as pollution in the ocean – 16 times more than the plastic microbeads from cosmetics. It believes that over a third (35 per cent) of primary microplastics entering oceans are released through the washing of textiles, and microfibres are more likely than other types of microplastic to absorb toxic chemicals, which may be injurious to health. Many people's preference would be to tackle this issue at source, as has hap- pened with the microbeads ban. But it is not realistic to ban synthetic clothing, which accounts for around 60 per cent of clothes produced globally, and measures that manufacturers could take to reduce the shedding of microfibres, such as mak- ing clothes with less blended material and tighter yarns, are also seen by many as prohibitively expensive. Engaging the public to change their washing practices – fewer microfibres are shed when clothes are washed at low tem- peratures, in a full washing machine and with no tumble drying – is one approach that could help, while it has also been proposed that improving filter technology in washing machines is a solution that should be explored. Treatment possibilities So is it possible for the wastewater industry to up its game on treatment to remove microplastics, and microfibres in particular? It's estimated that wastewater treat- ment plants remove something between 65 per cent and 95 per cent of microfibres. One reason for this wide range of perfor- www.wwtonline.co.uk | WWT | FEBRUARY 2019 | 13 • MICROPLASTICS RESEARCH • Every year, between eight and twelve million tonnes of plastic are thought to be entering the world's oceans, and around four million tonnes of it passes along rivers. In some cases, there can be over half a million plastic fragments per square metre of river bed • Research led by Cardiff University's School of Biosciences (September 2018) found that 50 per cent of freshwater insects tested in South Wales had microplastic inside them • A University of Manchester study in March 2018 not only found high concentrations of microplastic in UK rivers, but also found that these levels reduced by 70% a er a flooding incident, illustrating how the plastic was washed by heavy rain into the sea • The World Health Organisation (WHO) announced a review into the potential risks of plastic in bottled water in March 2018 a er an analysis of popular brands found that more than 90% contained microplastic • UKWIR's research project into the issue: Sink to River – River to Tap: A review of Potential Risks from Nano- particles and Microplastics, began in April 2018 as part of its 2018/19 research programme. UKWIR has made the removal of harmful plastics from water one of its 12 'big questions' for research in the industry.