Thames Water, the UK's largest utility, provides water to 9 million people and wastewater services to 14 million in southern England, including parts of London. In 2010, the utility was authorized by its regulator, Water Services Regulation Authority (Ofwat), to invest $8.1 billion over five years in its water and wastewater network under a national asset management plan known as AMP 5. The plan included a broad array of upgrades to improve service quality, control costs and mitigate the company's environmental footprint.
Thames Water is charged with controlling odor from the Beckton facility, which is surrounded by thousands of homes and businesses. Covering the sedimentation tanks -- with a total area of 600,000 square feet, or the size of about 10 football fields -- was a major challenge. CST Industries reviewed the project specifications and worked with GBM and other contractors to deliver a cover for each of the 16 tanks. "Aluminum covers are environmentally benign, structurally robust and operator-friendly, and they require little to no maintenance," said John Delaney, senior vice president of sales with CST.
Each sedimentation tank now has a low-profile aluminum cover with a slight pitch to allow water drainage. The low profile minimizes the air space under the covers, lowering the volume of air to be treated. Less air to treat means the utility can install a smaller odor control system at lower capital, operation and energy costs.
The covers have a series of inspection hatches that operators can safely access from any point on the cover system. Operators can conduct routine maintenance without entering the tanks and being exposed to odorous air. The 150-pound modular panels can be easily removed by two operators.
In addition to containing odors, the covers had to accommodate a system of scrapers inside each tank that gather settled sludge and push it to a collection tank. The scrapers were to be suspended from the covers' primary support beams. The challenge was to incorporate the dynamic loads from the scraper system into the cover design without compromising the performance of the scrapers or the covers. The hanging support system design ensured that the scraper systems could be placed at the required elevations while providing some flexibility during installation.
"The design of the support columns in the trough area required input from GBM, the scraper equipment supplier, and CST," said David Brahm, P.E., lead structural engineer with CST. "We came up with a solution that satisfies the scraper system clearance envelope and maintains the structural integrity of the entire cover system."
The upgraded Beckton plant with its new odor control capability plays an important role in Thames Water's performance, sustainability and customer satisfaction and serves as a model for treatment works throughout Europe.
CST Industries is an exhibitor at WEFTEC.15 and can be found at Booth 2339. For more information, visit www.cstindustries.com.
