Originally, water flowed by gravity into the settling tanks where it! was allowed to lie quiescent and the partly clarified water was then pumped to a. service reservoir Whence it flowed by gravity to slow] sand filter beds, the filtrate then passing to the pump wells, whence Te was pumped to Shanghai, As' the demand increased, the walls the settling tanks were raised to Increase their capacity and the tanks were filled partly by gravity and partly by centrifugal pumps installed on the river bank.
Five yours ago it was decided to obtain a quicker and more effectual Clarification in the settling tanks by' the use of a coagulant, sulphate of alumina being found ta be the most efficient and suitable; this coagulant added to the raw river water at point at which it leaves the] river' pumps. An additional reason for employing a coagulant was that the filters could be, with the clearer water, speeded up and at the same time the clarity and purity of the] filtrate improved; experience has} proved that our expectations were more than fulfilled.
The alum is fed to the river pump deliveries by dry feed machines! riven electrically; it is considered that this method is more suited to Toeal conditions than the more usual Nos. 1 and 2 tank—velocity 1.0 one of feeding in solution. In order} that native alum may be used small crusher, which has proved most successful in every way, has been installed. A coagulant house will be built in the near future to feontain the alum handling, crushing] fond feeding plant.
With the demand for more water jand the increasing cost of land, it was this year decided that the output from the works could most economically be increased by adapting the existing intermittent settling [tanks for continuous settlement and by replacing some of the. existing slow sand beds by rapid or mechanical filters; the construction of these new works is now well advanced and will be completed in time for the heavy demand this summer.
Text read from the printed page and cleaned; old type leaves the occasional error.