Thames Water: creating a cleaner, healthier River Thames
Sewage works upgrade from Thames Water see improvements across the board.
In the 1850s over 400,000 tonnes of sewage were flushed into the River Thames each day. The river was biologically ‘dead’ and the stench was overpowering. In summer 1858 Parliament had to be suspended because of the vile smell, which has been named the ‘Great Stink’. As a result, Parliament passed an enabling act to raise £3M to build a network of giant intercepting sewers, pumping stations and treatment works, designed by the Engineer Sir Joseph Bazalgette. This network has been much improved and extended over the years, but still forms the backbone of London’s sewerage system today.
In 2000, the Thames Tideway Strategic Study was set up to consider the environmental impact of storm discharges to the tidal River Thames, and to propose potential solutions that would ensure compliance with the requirements of the EC Urban Wastewater Treatment Directive concerning the collection, treatment and discharge of urban wastewater.
Thames Water, the Environment Agency, the Greater London Authority, Defra and Ofwat (as an observer) all contributed to the study, which was independently chaired by engineering consultant Professor Chris Binnie.
The study concluded that preventing discharges from combined sewer overflows alone would not be enough to achieve new water quality standards. It was agree that London’s major sewage treatment works would also need to be expanded as they needed to create considerably more wastewater.
Two of the major problems with the current systems are that, one, in heavy rainfall they can become overloaded. Excess flows are diverted to storm tanks, for treatment when flows subside. But once the tanks are full, the only option is to discharge any additional excess flows to the river, to avoid sewage backing up onto the streets or even into people’s homes.
Two, Bazalgette’s sewerage system was constructed with 57 combined sewer overflow points along the tidal River Thames.
When the sewers fill to capacity after heavy rainfall, any excess sewage is discharged into the river via these overflows, to prevent flooding to buildings and streets. Around 39M tonnes of untreated sewage is discharged annually, and a little as two millimetres of rainfall can trigger a discharge.
In line with the recommendations of the Thames Tideway Strategic Study, Thames Water are developing three separate schemes to address these problems; • A £675M investment to improve London’s five principal sewage works – Mogden, Crossness, Beckton, Long Reach and Riverside.
• The Lee Tunnel, to deal with the largest combined sewer overflow point at Abbey Mills Pumping Station, which discharges into the River Lee.
• The Thames Tunnel, to deal with the 34 most polluting combined sewer overflows along the River Thames between west London and Beckton Sewage Treatment Works.
The £675M investment to modernise and extend London’s sewage treatment works began in summer 2010.
The first of the upgrades of London’s five principal sewage works were completed during 2012 and saw upgrades at Long Reach Sewge Treatment Works and Riverside Sewage Treatment Works. These involved the delivery of additional treatment processes at both sites, the construction of a new 1,000cu m covered and odour control building at Long Reach and anaerobic digestion facilities at Riverside, enabling the plant to turn solid waste into enough renewable energy to power the site.
Mogden Sewage Treatment Works
Following the completion of the first two sites, a £140M upgrade at Mogden Sewage Treatment Works in west London began to extend sewage treatment capacity by 50%.
The project involved installing new equipment and upgrading the existing plant. To make space for this, the western embankment, which is within the existing site boundary was reshaped.
The landscape to the west of the site was also enhanced to benefit local wildlife.
As well as significantly reducing sewage discharges, these improvements helped reduce odour at the site, as the use of storm tanks will be reduced during heavy rain, and new and existing equipment will be covered over.
Now complete, Mogden generates up to 40% of its power requirements from renewable energy generated from ‘poo power’ – where electricity is generated by burning methane derived from sewage.
The Mogden site, in Isleworth, currently serves 1.9M people and covers an area of about 120 acres. Work on this upgrade completed in March 2013.
Beckton Sewage Treatment Works
The £190M improvements at Beckton, Europe’s largest sewage works, will enable the site to treat 60% more sewage than it does now and allow for a ten per cent population increase until 2021 so it can:
• fully treat increased flows during heavy rainfall, which currently discharge into the River Thames when the site becomes overloaded to prevent streets and homes from flooding
• treat additional storm flows from the Lee Tunnel, a new four-mile sewer which will capture storm sewage that currently overflows into the River Lee when the sewerage system gets overwhelmed during heavy rainfall
• accommodate additional flows from the proposed Thames Tunnel.
As well as helping to protect the River Thames, other benefits resulting from this scheme include:
• the installation of a 1.5MW wind turbine that will help generate eight per cent of the energy needed to power the site
• enhancing the landscape within the sewage works site and improving the Barking Creekside habitat to encourage wildlife, including creating a new nature trail
• opening footpaths around the site and river and creating new paths along the northern edge of the site by the River Roding and River Thames.
In addition, a further £67m will be invested as part of a separate project to cover the smelliest parts of the site, including all 16 primary settlement tanks – an area the size of ten football pitches – to significantly reduce odour emissions by 50%.
Beckton, located in the London Borough of Newham, is one of Europe’s largest sewage treatment works, and currently serves 3.5M people.
The upgrade is due for completion during 2014.
Crossness Sewage Treatment Works
A £220M upgrade scheme at Crossness is underway to help prevent sewage entering the River Thames during heavy rainfall.
The improvements will enable the site to treat 44% more sewage than it does now, significantly reducing the amount of storm sewage that overflows into the River Thames during heavy rainfall when the site becomes overloaded.
The project will also include the installation of a wind turbine that will help generate up to half the energy needed to power the site when combined with the energy generated from processing sewage sludge.
This wind turbine – which will be capable of powering 1,000 homes – will be the first ever to power a major British sewage works.
The upgrade at Crossness will also see new odour-controlled treatment processes and environmental enhancements.
Enhancement work is also taking place at Crossness Nature Reserve and the Southern Marshes – including creating a suitable habitat for water voles and birds.
Other work includes installing a temporary 70m high anemometer, which will provide information on wind speed ahead of detailed design of the new wind turbine, planned to be installed in 2013.
Crossness currently serves two million Londoners. The project is due for completion in 2014, and allows for a six per cent population increase until 2021.
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