WATER FILTRATION

Sun (Auckland), Volume 1, Issue 8, 31 March 1927, Page 6

WATER FILTRATION

STARTS IN MAY INSPECTION BY MAYOR Auckland residents cannot expect to receive filtered water from the Waitakere and Nihotupu reservoirs until early in May. The works were inspected yesterday by the mayor, Mr. G. Baildon, the chairman of the Works Committee, Mr J. Dempsey, and the assistant city engineer, Mr. J. Tyler, in company with other members of the council. The buildings to house the plant should be out of the hands of the contractors within a week, and the installation of the plant, most of which is on the ground, will occupy another six weeks. The water will pass through successive; layers of prepared sand and gravel, until cleansed, and will then be distributed to the city reservoirs. The actual process is far from as simple as it sounds. A coagulent to concentrate fine foreign matter in the water is necessary so that the sand can retain it. The water and coagulent are mixed through special races. After filtration it is necessary to neutralise acidity in the water. Lime will be used for this. Otherwise corrosion of the pipes is probable. There will be six filtration beds at Waitakere, and sev* a n at Nihotupu. Once every day each tank will be cleared for cleaning, a process taking an hour. This will be done by air pressure, followed by water from underneath the beds. Electric motors for driving the plant and to supply the alarms will have to be installed. A two-storeyed brick building will house the plant. ~