LONDON'S WATER SUPPLY

Press, Volume LXIX, Issue 21050, 29 December 1933, Page 14

LONDON'S WATER SUPPLY

FILTERING APPARATUS EXTENDED SCIENTIFIC METHODS LONDON, November 24. The Metropolitan Water Board is now extending its filtering plant at the Green Lanes pumping station, Stoke Newington, which is a reminder that from the point of view of water supply London, with a population of more than 7,500,000, is one of the outstanding towns of the •world. This applies equally to the scientific methods of purification adopted and the huge volumes of water consumed as well as the reserves in hand, so that, for example, an ample suppty has always been available in spite of the recent abnormally dry summer in England. For the Green Lanes extensions the Paterson Engineering Co., Ltd., of London, has in hand a contract ior the design and erection of the essential mechanical equipment for the rapid gravity primary filters which are being installed. These have a capacity of 34,000,000 gallons in 24 hours, comprising 12 large filter units, each with 900 square feet of effective filtering area, with control of the filter apparatus hydraulically from central panels in the main operating floor of the niter house. Undoubtedly the researches of Sir Alexander Houston, director of water examination for the Metropolitan Water Board, have played a great part in the development of .Tnodern scientific methods of water purification. Thus his investigations, as outlined in manv reports, have dealt with such subjects as the extent of purification resulting from long storage, the excess lime method of purification and sterilisation, the use of chlorine for sterilising as well as methods of derhlorinatin.e and the resistance to filtration offered by water under Various conditions. Water from the Thames. In general, the Metropolitan "Water Board takes about 58 per cent, of its total supply from the river Thames, while the remainder comes from various sources, including the river Lee and New River, and also wells, the average total consumption throughout the year being approximately 280,000,000 galJons a day. For normal operation the main method of purification adopted was slow sand filtration according to the usual practice, but in 1931 there was installed at Barn Elms a Paterson rapid gravity primary filtration plant with a capacity of 9,000,000 gallons in 24 hours, following upon the successful results obtained with the use of small experimental plant. As a consequence, the standard practice of the Metropolitan Water Board has since consisted in the general principle of using rapid graviiy sand filtration in primary filters, followed by the use of the existing slow sand filters to finish off the process, in this manner making use of the whole of the equipment already installed. An outstanding example in_ London of such combined filtration is the Metropolitan Water Board plant at KemDton Park, having 24 Paterson rapid eravitv filters with a caDacitv of 48.000,000 gallons a dav, officially opened in October, 1929. and operating in conjunction with 12 secondary slow sand filters, each measuring approximately threequarters of an acre, working at a rate of lli inches an hour. The final filtered water is treateci with ammonia and chlorine gas. using the Chloronome apparatus for sterilisation. A large number of modern plants of this tyr>e for town water sudoJv are also oneratinw in T Mia, as well as Epvpt. the Sudan, China, Hong Knn?. South Africa, and the Malay States.