Editing River Thames (section)

==Pollution==
===Treated and untreated sewage===
Treated [[sewage|waste water]] from all the towns and villages in the Thames catchment flow into the Thames via sewage treatment plants. This includes all that from Swindon, Oxford, Berkshire and almost all of Surrey.

However, untreated sewage still often enters the Thames during wet weather. When [[London sewerage system|London's sewerage system]] was built, sewers were designed to overflow through discharge points along the river during heavy storms. Originally, this would happen once or twice a year, however overflows now happen once a week on average.<ref>{{Cite news |url=https://www.tideway.london/the-tunnel/history/ |website=Reconnecting London with the River Thames |publisher=Tideway |title=History |access-date= |language=en |archive-date=14 September 2017 |archive-url=https://web.archive.org/web/20170914165600/https://www.tideway.london/the-tunnel/history/ |url-status=dead}}</ref> In 2013, over 55{{abbreviation|m|million}} tonnes of dilute raw sewage overflowed into the tidal Thames. These discharge events kill fish, leave raw sewage on the riverbanks, and decrease the water quality of the river.<ref>{{Cite news |url=https://www.theguardian.com/environment/2011/jun/09/fish-thames-sewage |title=Thousands of fish dead after Thames sewerage overflow |last=Vidal |first=John |date=9 June 2011 |work=The Guardian |language=en |access-date=18 February 2018 |archive-date=27 August 2020 |archive-url=https://web.archive.org/web/20200827085623/https://www.theguardian.com/environment/2011/jun/09/fish-thames-sewage |url-status=live}}</ref><ref>{{Cite news |url=https://www.theguardian.com/environment/2014/jul/22/water-thames-victorian-london-150-years-sewer-system |title=Water, super-sewers and the filth threatening the River Thames |last=Jeffries |first=Stuart |date=22 July 2014 |work=The Guardian |language=en |access-date=18 February 2018 |archive-date=27 August 2020 |archive-url=https://web.archive.org/web/20200827085636/https://www.theguardian.com/environment/2014/jul/22/water-thames-victorian-london-150-years-sewer-system |url-status=live}}</ref> A 2022 investigation by the Environment Agency found "widespread and serious non-compliance with the relevant regulations".<ref>{{Cite news |last=Laville |first=Sandra |date=13 May 2022 |title=Sewage dumps into English rivers widespread, criminal inquiry suspects |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2022/may/13/sewage-dumps-into-english-rivers-widespread-criminal-inquiry-suspects |access-date=21 April 2023 |issn=0261-3077}}</ref><ref>{{Cite web |title=Update on Environment Agency Investigation - Creating a better place |url=https://environmentagency.blog.gov.uk/2022/05/12/update-on-environment-agency-investigation/ |access-date=21 April 2023 |website=environmentagency.blog.gov.uk |date=12 May 2022 |language=en}}</ref> Thames Water has also published an interactive map showing discharges as they happen.<ref>{{Cite news |last=Laville |first=Sandra |date=23 January 2023 |title=Thames Water's real-time map confirms raw sewage discharges |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2023/jan/23/thames-waters-real-time-map-raw-sewage-discharges-rivers |access-date=21 April 2023 |issn=0261-3077}}</ref><ref>{{Cite web |title=EDM Map {{!}} Storm discharge data {{!}} River health |url=https://www.thameswater.co.uk/edm-map |access-date=21 April 2023 |website=Thames Water |language=en}}</ref>

To reduce the release of this into the river, the [[Thames Tideway Scheme]] was constructed at a cost of £5&nbsp;billion. It was completed in February 2025 after delays and additional costs because of the COVID-19 Pandemic.<ref>{{Cite web |title=Tideway sewer hits nine-month delay |url=https://www.theconstructionindex.co.uk/news/view/tideway-sewer-hits-nine-month-delay |access-date=2025-04-25 |website=www.theconstructionindex.co.uk |language=en}}</ref> This project collects sewage from the Greater London area before it [[Combined sewage overflow|overflows]], channelling it down a 25&nbsp;km (15&nbsp;mi) tunnel underneath the tidal Thames, so that it can be treated at [[Beckton Sewage Treatment Works]].<ref>{{Cite news |url=https://www.tideway.london |title=Reconnecting London with the River Thames |work=Tideway |access-date=18 February 2018 |language=en |archive-date=19 February 2018 |archive-url=https://web.archive.org/web/20180219090209/https://www.tideway.london/ |url-status=live}}</ref><ref>{{Cite news |url=https://www.bbc.co.uk/news/uk-england-london-29175607 |title='Super sewer' plans to go ahead |date=12 September 2014 |work=BBC News |access-date=18 February 2018 |language=en-GB |archive-date=27 August 2020 |archive-url=https://web.archive.org/web/20200827085643/https://www.bbc.com/news/uk-england-london-29175607 |url-status=live}}</ref> The project is intended to reduce sewage discharges into the Thames in the Greater London area by 90%, dramatically increasing water quality.<ref>{{Cite news |url=https://www.tideway.london/the-tunnel/river-ecology/ |title=River Ecology |website=Reconnecting London with the River Thames |publisher=Tideway |access-date= |language=en |archive-url=https://web.archive.org/web/20180218210432/https://www.tideway.london/the-tunnel/river-ecology/ |archive-date=18 February 2018 |url-status=dead }}</ref> It is estimated that two million tonnes of sewage will still enter the Thames each year.<ref>{{Cite magazine |title=London's super sewer won't solve the city's epic poop problem |language=en-GB |magazine=Wired UK |url=https://www.wired.co.uk/article/sewage-environment-climate-change-london |access-date=21 April 2023 |issn=1357-0978}}</ref>

===Mercury levels===
[[Mercury (element)|Mercury]] (Hg) is an environmentally persistent heavy metal which can be toxic to [[marine life]] and humans. Sixty sediment cores of 1 m in depth, spanning the entire tidal River Thames between [[Brentford]] and the [[Isle of Grain]], have been analysed for total Hg. The sediment records show a clear rise and fall of Hg pollution through history.<ref name="Rise and fall of Mercury (Hg) pollution in sediment cores of the Thames Estuary, London, UK.">{{Citation |url=http://nora.nerc.ac.uk/511959/1/Vane%20etal.%202015_RSE_Thames%20Hg.pdf |title=Rise and fall of Mercury (Hg) pollution in sediment cores of the Thames Estuary, London, UK. |last1=Vane |first1=C.H. |last2=Beriro |first2=D. |last3=Turner |first3=G. |date=2015 |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |doi=10.1017/s1755691015000158 |volume=105 |issue=4 |pages=285–296 |access-date=17 June 2016 |archive-date=12 August 2016 |archive-url=https://web.archive.org/web/20160812021715/http://nora.nerc.ac.uk/511959/1/Vane%20etal.%202015_RSE_Thames%20Hg.pdf |url-status=live |doi-access=free}}</ref> Mercury concentrations in the River Thames decrease downstream from London to the outer Estuary, with the total Hg levels ranging from 0.01 to 12.07&nbsp;mg/kg, giving a mean of 2.10&nbsp;mg/kg which is higher than many other UK and European river estuaries.<ref name=" Mercury contamination in surface sediments and sediment cores of the Mersey Estuary, UK. ">{{cite journal |url=http://nora.nerc.ac.uk/id/eprint/7405/1/Vane_et_al__2009_Mersey_Hg_9_3_09.pdf |title=Mercury contamination in surface sediments and sediment cores of the Mersey Estuary, UK. |last1=Vane |first1=C. H. |last2=Jones |first2=D. G. |last3=Lister |first3=T. R. |date=2009 |journal=Marine Pollution Bulletin |doi=10.1016/j.marpolbul.2009.03.006 |pmid=19356771 |volume=58 |issue=6 |pages=940–946 |bibcode=2009MarPB..58..940V |access-date=27 August 2020 |archive-date= |archive-url= |url-status=}}</ref><ref name=" Rise and fall of Mercury (Hg) pollution in sediment cores of the Thames Estuary, London, UK."/>

The most sedimentary-hosted Hg pollution in the Thames estuary occurs in the central London area between Vauxhall Bridge and Woolwich.<ref name=" Rise and fall of Mercury (Hg) pollution in sediment cores of the Thames Estuary, London, UK."/> The majority of sediment cores show a clear decrease in Hg concentrations close to the surface, which is attributed to an overall reduction in polluting activities as well as improved effectiveness of recent environmental legalisation and river management (e.g. Oslo-Paris convention).

=== Plastic pollution ===
The Thames has relatively high levels of plastic pollution, with an estimated 94,000 [[microplastics]] per second moving through some parts of the river. These microplastics come from the breakdown of larger items but also glitter and microbeads from cosmetics.<ref>{{Cite news |date=21 July 2020 |title=River Thames 'severely polluted with plastic' |language=en-GB |work=BBC News |url=https://www.bbc.com/news/science-environment-53479635 |access-date=21 April 2023}}</ref>

One study found one-fifth of macroplastics found in the river were from food packaging.<ref>{{Cite web |last=Quadri |first=Sami |date=22 November 2022 |title=Food wrappers make up '20 per cent of lightweight plastic in Thames' |url=https://www.standard.co.uk/news/uk/food-wrappers-river-thames-london-plastic-pollution-b1041511.html |access-date=21 April 2023 |website=Evening Standard |language=en}}</ref>