Mogden Sewage Treatment Works is a

sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding envir ...

plant in the

Ivybridge Ivybridge is a town and civil parish in the South Hams, in Devon, England. It lies about east of Andy Hughes’ new house in Ivybridge now he’s forgotten Ugborough. It is at the southern extremity of Dartmoor, a National Park of England an ...

section of

Isleworth Isleworth ( ) is a town located within the London Borough of Hounslow in West London, England. It lies immediately east of the town of Hounslow and west of the River Thames and its tributary the River Crane, London, River Crane. Isleworth's or ...

, West

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 ...

, formerly known as Mogden. Built in 1931–36 by

Middlesex County Council Middlesex County Council was the principal local government body in the administrative county of Middlesex from 1889 to 1965. The county council was created by the Local Government Act 1888, which also removed the most populous part of the coun ...

and now 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 ...

, it is the third largest sewage works in the United Kingdom. It treats the waste water from about 1.9 million people served by three sewers in North and West London. The plant has been extended to its geographical boundaries and is constantly being upgraded with new process, most recently in OfWat Amp6 by the Costain Atkins Joint venture who delivered 6MW of Combined Heat and Power (CHP) generation, New process air blowers for Batterys A&B and 6 new gravity sludge thickening streams. The site now covers .

History

The plant was built in 1931–36 for £1.7 million by Middlesex County Council, replacing 28 small sewage treatment facilities as part of the West Middlesex (Mogden-Perry Oaks) Main Drainage Scheme.Philip Howard, ''London's River'', London: Hamilton, 1975,
p. 223"> p. 223
The council purchased Mogden Farm for the purpose after the public objected to the proposed site in

Syon Park Syon Park is the garden of Syon House, the London home of the Duke of Northumberland in Isleworth in the London Borough of Hounslow The London Borough of Hounslow () is a London borough in West London, England, forming part of Outer London. ...

. of sewers were built to connect to it,''Environmental Accomplishments to Date: A Reason for Hope: International Symposium II, July 16–18, 1974'', ed. George M. Dalen and Clyde R. Tipton, Jr., The Environmental symposium series, Columbus, Ohio: Battelle Memorial Institute,

974 Year 974 ( CMLXXIV) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. Events By place Europe * Battle of Danevirke: Emperor Otto II defeats the rebel forces of King Harald I, who has ...

p. 50
and the

Duke of Northumberland's River The Duke of Northumberland's River or D. O. N. River consists of separate upper and lower artificial watercourses in west London, United Kingdom. The older name Isleworth Mill Stream/River more accurately describes the economic motivation behi ...

was diverted to flow through it as a source of coolant.Mogden
Hidden London, retrieved 12 November 2013. The plant began operations in late 1935 and was formally opened with the rest of the scheme on 23 October 1936 by the then

Minister of Health A health minister is the member of a country's government typically responsible for protecting and promoting public health and providing welfare and other social security services. Some governments have separate ministers for mental health. Coun ...

, Sir

Kingsley Wood Sir Howard Kingsley Wood (19 August 1881 – 21 September 1943) was a British Conservative politician. The son of a Wesleyan Methodist minister, he qualified as a solicitor, and successfully specialised in industrial insurance. He became a membe ...

.Philip T. Sherwood, ''Heathrow: 2000 Years of History'', Stroud: Sutton, 1999,
p. 33
In its first year of operation it treated an average of 60,020,000 gallons of sewage per day. From 1935 the treatment facilities at Mogden comprised storm water tanks, primary sedimentation, sewage aeration, final separation and sludge digestion. The plant was designed to treat three million cubic metres per day of sewage.Leslie B. Wood, ''The Restoration of the Tidal Thames'', Bristol: Adam Hilger, 1982, , pp. 74–84. The works were expanded in 1962, 1989 and 1991 and upgraded in 1996–2002. The 1962 extension included commutators, grit chambers and pre-aeration tanks, together with the following additional tanks. The most recent expansion, in 2011–13, increased the treatment capacity by more than half and increased the plant's size by , as part of the

Thames Tideway Scheme The Thames Tideway Tunnel is a combined sewer under construction running mostly under the tidal section (estuary) of the River Thames across Inner London to capture, store and convey almost all the raw sewage and rainwater that currently ove ...

to improve water quality in 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 ...

. It was completed in summer 2013.

Technical approach

When built, the Mogden works were very modern, one of the first large-scale applications of the

activated sludge The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganisms ...

technique for sewage treatment. The plant was also advanced in having a central control board for measurements and in using the

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

generated by sewage treatment to generate electricity and heat from the processing to heat the sludge. It was originally equipped with oil and spark-ignition gas engines; a heat and power plant was added in 1993. In 1974 the works were selling surplus methane for £12,000 a year (); the latest upgrade enables them to meet 40% of their energy requirements from methane. Initially, after approximately 25 days at Mogden, sludge was piped to settling ponds at the Perry Oaks Sludge Treatment Works near

Heathrow Airport Heathrow Airport (), called ''London Airport'' until 1966 and now known as London Heathrow , is a major international airport in London, England. It is the largest of the six international airports in the London airport system (the others be ...

.''Journal of the Institution of Civil Engineers'' 27–28 (1946
377
In 1989 the Perry Oaks site was closed and the land reclaimed for Heathrow Terminal 5 with new sludge dewatering provided at nearby Iver South. There is a plant for dosing the effluent with

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

before the outfall pipes. This is operated on the instruction of the Environment Agency if the stormtanks are overflowing and discharging into the effluent channel. The peroxide prevents low oxygen conditions developing in the tidal sections of the river that receive the flows. During dry weather with low flows the effluent from Mogden can constitute the main part of the flow in the river. There is also an effluent oxygenation plant under construction, due to be commissioned 2020. This consists of an array of aerators that can be lowered into the effluent channel to increase the dissolved oxygen levels in the effluent. This would only operate during very dry weather to ensure that when flows in the river Thames are low oxygen levels in the Upper Thames Tideway are kept high enough to encourage salmonid migrations and ensure a healthy aquatic ecosystem. This will be the first such effluent aeration plant in the UK.

Environmental complaints

The Mogden works discharge effluent at

Isleworth Ait Isleworth Ait, also known as Isleworth Eyot, is a between and teardrop-shaped island in the River Thames in England. The long ait is on the Tideway facing Old Isleworth and the towpath alongside the Royal Mid-Surrey Golf Club. These places a ...

, on the

Tideway The Tideway is a part of the River Thames in England which is subject to tides. This stretch of water is downstream from Teddington Lock. The Tideway comprises the upper Thames Estuary including the Pool of London. Tidal activity Depending on ...

in the upper reaches of the

Thames Estuary The Thames Estuary is where the River Thames meets the waters of the North Sea, in the south-east of Great Britain. Limits An estuary can be defined according to different criteria (e.g. tidal, geographical, navigational or in terms of salini ...

. Between 1956 and the completion of an expansion in 1962, some of this had not received secondary treatment. Also during heavy rain, the plant was sometimes overwhelmed and released untreated sewage into the river; in summer 2011, 200,000

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s of untreated sewage from Mogden contributed to a large fish kill. Nearby residents have also complained about odour: the Borough of Hounslow served an odour abatement notice on Thames Water in 2001, and in 2011 complainants won a court judgement that the company had failed since 1990 to adequately manage odour and thereby violated human rights; £19,000 in damages to ten people were assessed. In January 2022 a report published by the

Environmental Audit Committee The Environmental Audit Select Committee is a select committee of the House of Commons in the Parliament of the United Kingdom. The remit of the committee is to examine how government departments' policies and programmes will affect both the envir ...

found that Mogden discharged enough sewage to fill 400 Olympic-sized swimming pools on 3 and 4 October 2020. It added that during the whole of 2020, 3.5 billion litres of untreated sewage entered the Thames from Mogden - seven times as much as was dumped in 2016.

Mogden formula

The plant gave its name to the Mogden formula, a measure of the volume and strength of industrial effluent used in treatment pricing. The Mogden formula is: where: = charge per volume of effluent (£/m³) = reception and conveyance charge �/m³ = primary treatment (volumetric) charge �/m³ = additional volume charge for biological treatment �/m³ = treatment and disposal charge where effluent goes to sea outfall �/m³ = biological oxidation of settled sewage charge �/m³ = chemical oxygen demand (COD) of effluent after one hour of quiescent settlement at pH 7 g/litre = chemical oxygen demand (COD) of effluent after one hour of quiescent settlement g/litre = treatment and disposal of primary sewage sludge charge �/m³ or £/kg = total suspended solids of effluent at pH 7 g/litre = total suspended solids of effluent g/litre The Mogden formula indicates that the more contaminated the wastewater or effluent is, and the greater the volume of suspended solids, the higher the charge will be for treating it.

References

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External links

Mogden Sewage Treatment Works
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