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Hornsey Water Treatment Works
Newland Road, Hornsey, London, UK
associated engineer
Not known
date  1878 - 1880, 1903, 2002, 2004 - 2009
UK era  Victorian  |  category  Water Supply/Pipes  |  reference  TQ303898
ICE reference number  HEW 2215
The Hornsey Treatment Works are associated with the New River, the water supply system begun in the 17th century that brings water from Hertfordshire to London. The brick buildings associated with the works were the last constructed by the New River Company before the Metropolitan Water Board took over in 1904.
The New River brought untreated water to the capital, although following the promulgation of the 1852 Metropolis Water Act, some treatment, such as filtration, became mandatory. The New River system still delivers Hertfordshire water to London to this day.
The river arrives at the Hornsey works through the 1,006m long 4.27m diameter Wood Green Tunnel, built by William Chadwell Mylne senior in 1852 to replace a meandering part of the original contoured river course. Leaving the tunnel, the river passes under an arch of the original Great Northern Railway into the Hornsey Reservoir (TQ303899), which has an area of 0.4ha. South of the reservoir, it can be seen running beside the railway line until it once again passes under it, making for the East and West reservoirs at Stamford Hill.
Hornsey has been home to filtration works since the mid 19th century. Six new square filter beds were constructed immediately downstream of the reservoir in 1878-80.
On the west bank of the river course, south of the modern works, is the red brick sluice house, which is rectangular and has a flat roof. The main pumping station (TQ306894) is on New River Avenue at High Street, also of red brick, with white stone dressings, ground floor arched windows and hipped slated roofs with raised light wells along the ridge lines. Its original oil engines could pump 126 million litres of water per day.
Hornsey Water Treatment Works has been recently upgraded and is now operated by Thames Water. However, the pumping station had became obsolete and was sold. In 2002, the building was redeveloped by St James's Homes and the Royal Academy of Art into a restaurant and gallery.
The treatment works also processes water from by aquifer. In 2000, the aquifer was found to be affected by algal blooms that blocked the sand filters and slowed the production process. Thames Water, Costain and Black & Veatch combined to carry out a £42m scheme to upgrade the works while the existing plant remained in continuous operation.
The slow sand filters have been replaced with a bromate pre-treatment plant of 50 million litres per day capacity, a bromate removal and wash water recovery plant, improved disinfection and control facilities, and a filtration system using catalytic granular activated carbon. This makes it possible to supply potable water even if algal blooms or high bromate levels are present. Excavations for the new equipment extended to almost 8m below river level.
The new plant became operational on the 18th December 2008 and was working fully by the 31st January 2009.
Contractor (1878-80, 1903): Thomas Docwra
Contractor (2004-9): Costain
Oil engines: W.H. Allen, Bedford
Research: ECPK
"Obituary: James Muir, 1847-1889" in ICE Proceedings, Vol.96, pp.323-326, London, January 1889
"Obituary: Charles Cressy Horsley, 1856-1894" in ICE Proceedings, Vol.118, p.46, London, January 1894
"Obituary: John Addy, 1847-1896" in ICE Proceedings, Vol.127, pp.361-362, London, January 1897
"A Little Book on Water Supply" by William Garnett, Cambridge University Press, London, 1922
reference sources   CEH Lond

Hornsey Water Treatment Works