Crossness Sewage Treatment Works Upgrade, United Kingdom

Crossness Sewage Treatment Works

Crossness Sewage Treatment Works (STW), Europe's second biggest waste treatment plant, is currently being upgraded with an investment of £220m ($365m). The facility, owned by Thames Water, currently serves approximately two million people in east London.

The upgrade project is part of the £675m ($1.12bn) London Tideway Tunnels programme, which aims to enhance the treatment capacity of London's five major STWs including Mogden, Crossness, Beckton, Long Reach and Riverside. The larger project also includes two tunnelling projects, Lee Tunnel and Thames Tunnel.

The contract for the Crossness STW upgrade was awarded to Tamesis, a joint-venture (JV) of Imtech Process and Laing O'Rourke. The work is scheduled to be completed in 2014.

Benefits of the Crossness STW upgrade

Ongoing upgrade works will enable the plant to treat 44% more sewage, which will considerably reduce storm sewage flowing into the River Thames during heavy rainfall.

"The upgrade is designed to meet the environmental standards required by the Environment Agency."

The upgrade also involves the installation of new renewable energy sources including a wind turbine and thermal hydrolysis plant (THP) on-site, an advanced digestion plant and an advanced odour control treatment system.

The upgrade is designed to meet the environmental standards required by the Environment Agency (EA). Environmental enhancements to the Crossness Nature Reserve are also being carried out as part of the project. The 20ha Crossness Nature Reserve on the eastern boundary of the site maintains one of the last areas of grazing marshland in Greater London. Enhancement work at Crossness Nature Reserve and the southern marshes will create a suitable habitat for water voles and birds.

History of Crossness Sewage Treatment Works

Crossness STW was built in 1865 as part of Sir Joseph Bazalgette's plan to manage London's sewage. The facility is spread across 70ha of land situated on the south bank of the Thames in Abbey Wood, London.

The sludge-powered generator has been functioning since 1998 producing up to 6MW of energy, sufficient to meet three quarters of the site's electricity requirements.

Project details of the Crossness upgrade

The project will enable the plant to treat 13m³/s of sewage by incorporating new inlet works, primary settlement tanks, secondary biological treatment implementing the activated sludge process and final settlement tanks. It will also include installation of the associated sludge thickening and odour treatment facilities.

The wind turbine, to be installed at a hub height of 78.5m, will provide 2.3MW of renewable energy sufficient to power approximately 1,300 homes. Two Monashell biofiltration systems by Anua are being installed at the site to treat air emissions.

On completion, the THP will burn the highly combustible sludge flakes created after waste water treatment to 160°C, to produce 50% more biogas prior to the anaerobic digestion (AD) process. The biogas will be used to generate renewable energy.

The upgrade project will also replace 12 vertical shaft pumps, valves, actuators and pipework of the inlet pumping station with 13 new dry well submersible pumps, valves and pipework.

Elevated preliminary treatment works will have a capacity of 6.5m³/s and will comprise five band screens, as well as handling and washer compactors with a capacity of 43m³/h.

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The project also includes the installation of eight new primary settlement tanks (PST) where sewage is collected to remove primary sludge passing through two 1.2km-long culverts of 2m diameter. The new PSTs will use alternate Zikkert scrapers for desludging.

Sewage will pass through a pair of new aeration lanes into 12 final settlement tanks of 40m diameter each to undergo the activated sludge process.

The activated sludge plant will include six aeration lanes of 69m with total volume of 86,000m³ and a treatment capacity of 564 million litres per day. It will include anoxic zone mixers, a fine bubble diffused aeration (FBDA) system and five centrifugal blowers giving an air flow of up to 21,000m³/h.

Additional sludge storage and thickening facilities will store all the added sludge. The five raw sludge gravity belt thickeners will have a capacity of 6,055m³/day each.

Screening and degritting will be done with four new velocity grit channels. The project also involves large-scale restoration and upgrade of the existing aeration lanes and final settlement tanks.

A new process control network integrating a supervisory control and data acquisition (SCADA) system will also be installed as part of the project. Three standby MWM TCG2020V20 generators by Edina will be installed on site, which will provide 2MW of power each during power shortages.

Contractors involved with the Crossness project

The subcontractor for the THP plant is Cambi. Imtech is constructing the AD plant, while the digesters to be used in the THP are being supplied by Jet-Vac Systems. The multiple PLC, SCADA and instrumentation solutions for the THP were provided by Capula.

Geotechnical, civil and structural design for the project was provided by Hyder, and Evolution5 was appointed as the commercial manager for Tamesis. The power management system of the plant is being modified by Regulateurs Europa.

Roxtec is supplying the multi-cable transit seals, which can support extremely high water pressures to prevent water ingress. The PST, de-sludge and aeration applications were installed with Val-matic eccentric plug valves.

DH Stainless signed a £1.5m ($2.5m) contract to supply stainless steel pipes and fittings to the Crossness and Beckton projects. The valves, pipeworks and coarse screens for the inlet pumping station are being supplied by JK Fabrications.

Aquaflow supplied 250 valves ranging in size from 100mm to 900mm to Crossness STW. The package included manual and actuated wedge gate valves, swing check valves, air valves, pinch valves, butterfly valves and operating equipment.

NRI Energy Technology