Sewage Works, Louds Mill Dorchester

Image: © Nigel Mykura Taken: 1 Feb 2010

This is a radial flow sludge settlement tank with half bridge scraper. The tank is circular and is used in one of the primary stages of sewage treatment to separate sludge from the effluent. The sewage enters the tank at the centre and flows to the outside. The decrease in velocity allows heavier sludge to settle out to the bottom of the tank. The bottom of the tank is saucer shaped and the cleaner effluent flows out of the tank to the next stage in the process over the serrated weirs on the outer lip of the tank which can be seen in the foreground. There is a half bridge which connects the centre to the rim of the tank. Although this is out of picture it can be seen reflected in the water at the top of the picture. The purpose of the half bridge is to support the rotating scraper blade. This blade, mounted on the diagonal struts that can be seen attached to the half bridge, rotates round the bottom of the tank scraping the sludge and pushing it towards the centre of the saucer shaped tank bottom where the sludge is extracted through a central hole. A more complete picture of this tank is atImage

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