Although plastics in the marine environment have received worldwide attention, it is estimated that more than half of microplastics released remain on land. This happens when wastewater sewage sludge is applied to soil, and when particulates are washed from road surfaces. Unfortunately, there is no simple solution to the microplastic problem; once released into the environment there are few, if any, practicable means by which these pollutants can be removed. As many microplastics are produced from the degradation of larger items, we should be looking further upstream for both pollution and its prevention.
Whilst the damage to the marine environment should not be overlooked, we must equally focus our attention to impacts that microplastics could have on freshwater and terrestrial environments. They have the potential to accumulate in these environments, impacting upon nature and the human food chain, as well as providing a platform for pathogens.
Microplastics can be any particles smaller than 5mm, including microscopic particles. They form from the weathering and breakdown of larger plastics, or are released intentionally or unintentionally in the form of manufactured beads, granules and fibres. Most microplastics have been found to arise from the washing of synthetic textiles and from the breakdown of plastic road markings and tyres from driving. Once released into the environment, they can then be transported via the wind, through surface waters and sewers, and by rivers.
At CIWEM, our new report has reviewed the latest evidence on microplastic removal processes at water and wastewater treatment plants. We found that wastewater treatment processes could reduce microplastics from 97-99%. Whilst this sounds promising, the large volumes of wastewater processed each day means that millions of microplastics are still being released back into the freshwater environment.
The high proportion of particles that are removed at wastewater treatment works become trapped in sewage sludge. These can then be transferred back into the environment when sewage sludge is spread on land to provide the nutrients needed for agriculture. EU legislation requires sludge to be treated to protect against health hazards, for example by lime stabilisation, anaerobic digestion, composting or thermal drying, but there is limited evidence of these being able to remove microplastics and no current specific regulation.
Data on the environmental and health impacts of microplastics on land are sparse. Our report calls for much greater research into the impacts associated with the application of sewage sludge containing microplastics to farmland.
The Government has recently published draft legislation that will ban the sale of products that include microbeads in ‘wash off’ personal care products by January, and ban their manufacture by June 2018. Whilst this is a welcome ‘upstream’ intervention, these are a minor contributor to the overall problem – it is estimated that these make up just 0.01 to 4.1% of plastics in the marine environment.
Every-day disposable items, such as plastic bottles and coffee cups, are particularly problematic. Only around half of the 35 million plastic bottles sold in Britain every day are currently collected for recycling. Moreover, around 7 million cardboard coffee cups are thrown away each day, many with a single use plastic lid. Only 1 in 400 cups are recycled, leaving over 6.98 million for landfill, or ending up in the environment.
To tackle this growing mountain of waste, our report calls for the Government to implement a new plastics strategy to improve product design and substitution, extend producer responsibility and support plastic bottle deposit return schemes.
Laura Grant, Senior Policy Adviser
CIWEM (the Chartered Institution of Water and Environmental Management)
CIWEM’s report ‘Addicted to Plastic’ and a policy position statement ‘Microplastic pollution’ can be found at www.ciwem.org/waste-resources.