Aerial view of Coppermills Water Treatment Works

The Coppermills Water Treatment Works is a large

water treatment Water treatment is any process that improves the Water quality, quality of water to make it appropriate for a specific end-use. The end use may be drinking water, drinking, industrial water supply, irrigation, river flow maintenance, water recrea ...

works in the Lea Valley in east London. Completed in 1969 by the

Metropolitan Water Board The Metropolitan Water Board was a municipal body formed in 1903 to manage the water supply in London, UK. The members of the board were nominated by the local authorities within its area of supply. In 1904 it took over the water supply functi ...

, it is now owned and operated by

Thames Water Thames Water Utilities Ltd, known as Thames Water, is a large private utility company responsible for the public water supply and waste water treatment in most of Greater London, Luton, the Thames Valley, Surrey, Gloucestershire, north Wiltshir ...

. In 2009, Coppermills was connected to the

Thames Water Ring Main The Thames Water Ring Main (TWRM, formerly the London Water Ring Main) is a system of approximately of concrete tunnels which transfer drinking water from water treatment works in the Thames and River Lea catchments for distribution within cen ...

via the Northern Extension Tunnel, enabling the facility to be a major supplier of water to the whole

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

area. It is capable of supplying a maximum of of water per day.

Water source

The facility draws water from the Lee Valley Reservoir Chain located directly to the north, which sources its water from the

River Lea The River Lea ( ) is in South East England. It originates in Bedfordshire, in the Chiltern Hills, and flows southeast through Hertfordshire, along the Essex border and into Greater London, to meet the River Thames at Bow Creek. It is one of t ...

, the New River, and the

River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, se ...

(via the

Thames-Lee Water Main London's water supply infrastructure has developed over the centuries in line with the expansion of London. For much of London's history, private companies supplied fresh water to various parts of London from wells, the River Thames and the Rive ...

). Water flows to Coppermills directly through channels from the East Warwick, Low Maynard, and Walthamstow No. 5 reservoirs. It is also supplied via the

Coppermill Stream The Coppermill Stream is a short waterway near Walthamstow in the Lea Valley. Originally a minor tributary of the River Lea, the approximately long stream is now used as an aqueduct to transport water from the reservoirs in the Lea Valley to C ...

and the ‘Spine Tunnel’ which is fed from the Lockwood,

King George V George V (George Frederick Ernest Albert; 3 June 1865 – 20 January 1936) was King of the United Kingdom and the British Dominions, and Emperor of India, from 6 May 1910 until his death in 1936. Born during the reign of his grandmother Que ...

William Girling William James Girling (9 March 1882 – 7 September 1973) was a Reform Party Member of Parliament in New Zealand. He was elected to the Wairau electorate in the 1922 general election, but was defeated in 1928 by Edward Healy of the Un ...

and Banbury reservoirs further north.

Operations

The first water treatment process at Coppermills works is rapid gravity filtration. There are 24 rectangular open topped tanks containing sand. Water enters the top of the tanks and flows down through the sand layer under gravity. The water residence time in the filters is about 15 minutes. The filters remove particulates and the cleaned water flows from the bottom of the filters. Periodically, every 6 to 24 hours each filter is shut in and clean water is pumped up through the bed together with compressed air to scour the sand and remove material caught during the filtration phase. When the backwashing process is complete the filter is bought back into service.

Ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

gas is then added to the water to oxidise contaminants such as pesticides and organic material. The process of ozonization also kills bacteria. Water then flows to the next stage Slow Sand Filtration. There are 33 slow sand filter beds at Coppermills water treatment works, which occupy much of the site. The sand bed in the filters support a gelatinous

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

or hypogeal layer in the top few millimetres of the sand. The surface biofilm provides an effective biological treatment. Water passes through the hypogeal layer where contaminants are retained and metabolised by the bacteria, fungi and protozoa. Over several weeks the biofilm becomes thicker and the flow of water reduces. The filter bed is drained and the biofilm layer is scraped off and replaced with fresh sand. The water then passes through fine 400-micron (400 μm) stainless steel mesh screens. The water is then dosed with

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

in contact tanks which contain baffles to ensure that chlorine is completely mixed with the water. Chlorine destroys harmful micro-organisms. The water is pumped into the distribution system supplying customers directly or through covered service reservoirs. Problems occur at treatment works during periods of algal bloom in the reservoirs, which reduce the cycle time of the rapid gravity filters. At Coppermills works this reduces the capacity of the plant from its normal throughput of 560 million litres per day to 380 Ml/d. A new (£46 million) plant was commissioned in 2014 providing 12 rapid gravity filters with a capacity of 200 Ml/d.

References

{{Thames Water London water infrastructure Thames Water 1969 establishments in England