4Microplastic prevention and solutions
Tackling microplastic pollution
63.Dr van Sebille, Imperial College, argued that tackling microplastic pollution is about identifying intervention points, “where it is most efficient to intervene and where it is most efficient to do something about the release.”177 Professor Thompson said:
Plastics are persistent contaminants; even if it were feasible to cease inputs of plastic debris to the oceans with immediate effect, the quantity of microplastic would continue to increase because of the fragmentation of larger items that are already present in the environment. Hence research is needed to fully understand the abundance, distribution and potential environmental impacts of microplastics. However, it is also important to move toward the solutions which are already widely recognised.178
The BPF argued, “preventing further plastic from entering the ocean is key to dealing with this issue as removing existing plastics would not prevent future problems and would be expensive.”179 Similarly, Professor Richard Thompson argued that “the fragmentation of larger items of debris is likely to be a more important source of microplastics than the direct release of microbeads from cosmetics.”180 He said:
The overarching solution is to ensure greater quantities of plastic waste are captured in recycling streams; this will reduce their potential to become litter (large items of plastic litter become microplastic).181
64.The Marine Conservation Society argued that filtering microplastics from the marine environment would be “extremely challenging, expensive and impractical.” They suggested:
Stopping the microplastics at source is undoubtedly and significantly more efficient than trying to remove it once in the aquatic environment.182
Similarly, Fauna & Flora International’s Microplastic Programme has focussed on those sources of microplastic that they deemed easily preventable. They state:
[Although] secondary microplastics may represent a larger source of input than primary microplastic ingredients, we are motivated to work on the latter […] because we would consider the potential solution to the former (e.g. harmonised waste management reform) to be more vastly longer-term than the latter (changing corporate decision-making).183
Neal’s Yard Remedies, argued that “removing plastics from personal care products is the most efficient and cost-effective way of stopping this pollution. ‘End of pipe’ solutions through upgrading of sewage treatment plants would be far more costly.”184 Veolia UK, a wastewater management service agreed that it would be more effective to stop microplastic pollution at the source than through wastewater treatment.185 This is because the wastewater plants are not equipped to filter out microplastics and equipping the plants with ultrafine filters would be costly. In addition it would not eliminate the problem, as not all waste water passes through a plant.186
65.The most effective solution to tackling microplastic pollution in the marine environment is to tackle it at the source. This means stemming the flow of primary microplastics, and general plastics, entering the marine environment in the first place. We heard that taking action to tackle ocean plastic pollution at source is the best strategy, and we believe that this is also the most feasible option in the short-term.
Waste and water treatment solution
66.Currently waste water treatment plants are not designed to retain microplastics, and the resulting sewage effluent can carry fibres and microbeads out to rivers, lakes, estuaries and the sea.187 A Eunomia report for the European Commission found that the percentage of microplastic particles captured in waste water treatment sewage sludge ranges from 65% to 100%.188 The British Plastics Federation said:
All countries in the world need to have adequate waste management facilities to deal with the waste they are producing and ensure it is used to its maximum value. Ensuring education on litter takes place globally will also be essential.189
67.Surface water treatment processes generally have three stages of treatment which includes coagulation, flocculation and filtration. These processes do not specifically monitor for microplastics, however, they may coincidentally capture extremely small particles.190 United Utilities stated that, for drinking water, particles over 0.5µm were filtered out through this process so microplastics above this size will not enter drinking water.191 Following these processes, wastewater and sludges from the water treatment plant are treated and then the waste streams are subsequently discharged to sewer, local water course or the sludge is thickened and spread on land or sent to sewer.192
68.In relation to sewage sludge containing microplastics washing back into the river, Severn Trent Water highlighted:
100% of the sludge bioproduct generated by Severn Trent Water is safely recycled to land. Whilst there are no specific measures targeted at preventing microplastics in sludge from washing back into rivers, there is an industry wide code of practice [the DEFRA published Code of Practice for Agricultural Use of Sewage Sludge] in place that covers the recycling of bioproduct to land. This code covers protection of the aquatic environment.193
Dr van Sebille, Imperial College London, identified a study of water treatment plants in the Chicago area, and suggested sand filters may be effective in capturing both fibres and microbeads.194 Thomas Maes, CEFAS, did a study on the sewage treatment works in Crossness which looked at the incoming water, the outgoing water and the sediments in front of the pipe to ascertain the amount of microplastics and it found an “almost 85% reduction [in microplastics].”195 However, Dr van Sebille added:
A sand filter might work very well, but the problem is once you go into that, at some point you have to backflush your sand filter, you have to push it back, and then what do you do with that sludge?196
Sludge was also a concern from Anglian Water, which stated that:
This sludge forms a vital biosolid product that is recycled to agricultural land. Increased concentrations of plastics in this product would not just return the plastics back to the environment through spreading, but could also raise concerns about quality of the biosolid product and therefore put at risk a valuable source of nutrients for the agricultural sector.197
69.We received evidence from water companies that there are no specifically designed sewage treatment processes to capture very small particles.198 Many plants, such as Southern Water, have methods of capturing plastics above 6mm, which will not be able to further degrade into microplastics.199 There are also limits set relating to treatment processes for other organic and inorganic solids.200
70.Furthermore, all water companies highlighted that there is currently no agreed methodology for taking plastic pollution measurements. South West Water said, “We do not measure plastic content in our sewage treatment works influent or in treated effluent, and are not currently required by any regulations to do so.”201 Yorkshire water reiterated this and said “Currently our sewerage systems and treatment processes are not designed to remove microplastics and we are not regulated by the Environment Agency to do so.”202 This was reaffirmed by Dr Foster, Marine Conservation Society, who said, “When I talked to the Environment Agency they do not monitor [microplastics]. There are no permissions required. You can effectively emit as much pellets as you like legally as far as I understand from the Environment Agency, because it is not considered a hazardous substance.”203 We wrote to The Environment Agency who stated that they:
[Do] not currently explicitly consider micro-plastic in its environmental permits to discharge liquid effluent or waste water to surface water or onto the ground. […] Regulation at end of pipe would be premature before there is a better understanding of sources and environmental impacts of microplastics and the costs and benefits of supply-side or end-of-pipe controls. There is a need for better information on the source apportionment of microplastics in the environment and potential effectiveness of control measures.204
71.Water UK said, “the water industry has no current experience or technologies to separate out microplastics […] and treatment of micro plastics by the water industry has never been explored.”205 They argued that a key challenge is to separate the microplastics from the organic content on available operational scale and at reasonable cost. There are significant investment needs to add any additional filtration to pump effluent or sludges against a series of fine mesh.
72.Similarly, the Government argues that installing filtration systems will be an expensive option. George Eustice, Minister at DEFRA, said:
Filtration goes through various phases and filters out more and more of the plastics. Frankly, it is incredibly difficult and a big undertaking to filter microbeads out, because you need quite expensive sand filtration systems. It is therefore probably easier to try to stop putting them in the sewer in the first place, rather than putting them in and trying to work out how to take them out.206
However, the Government told us that they had not been in contact with any water companies but were open to the suggestion. George Eustice, Minister at DEFRA, said:
We have not [called a summit of water companies]. […] We will want to digest this evidence digest and take it on board to see whether lessons can be learned. If there are issues that we should build into the pricing plans that Ofwat is looking at in the future, we can do that, if it can be done in a cost-effective way.207
73.We heard that prevention at source by reducing the number of microplastics flushed into the oceans is most viable. However, there are also opportunities to capture microplastics through effective waste and water sewage treatment processes which currently do not require the monitoring of microplastics. We recognise the heavy investment needed in this area, and that there is difficulty in filtering microplastics. Therefore, we recommend that the Government and Environment Agency work with Water Companies to understand what feasible options there are to monitor and ultimately reduce microplastic pollution.
177 Q40
180 Q263
186 As above
187 Veolia (EIM0039), United Utilities (EIM0047), Northumbrian Water (EIM0049), Thames Water (EIM0051), Yorkshire Water (EIM0052), Water UK (EIM0055)
194 Q16
195 Q332
196 Q16
198 Veolia (EIM0039), Wessex Water (EIM0044), United Utilities (EIM0047), Northumbrian Water (EIM0049), Thames Water (EIM0051), Yorkshire Water (EIM0052), Water UK (EIM0055)
200 As above
203 Q97
206 Q327
207 Q340
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26 July 2016