PURPOSE: To efficiently coagulate and separate suspended solids from highly suspended solid-contng. water, by adding an inorganic compound, which can form Al and/or Fe hydroxide(s), to the water, separating the resultant coagulating precipitate from the water, and then letting the water flow through a sand filter layer.
CONSTITUTION: An inorganic salt, which can form Al and/or Fe hydroxide(s) by hydrolysis, is added to highly suspended solid-contng. water, and most of suspended solids are separated as coagulating precipitate by the coagulating precipitation or the like with the hydroxide(s). Thereafter, the obtained purified water is let flow through a sand filter layer in the presence of 200ppm or less of the inorganic salt, which can form the Al and/or Fe hydroxide(s), to reduce an amount of Al and/or Fe having a particle size of 0.45μ or less in the water. The inorganic salt may be aluminum sulfate, poly(aluminum chloride) or the like. Sand particles in the sand filter layer are preferably those having an averaged particle size of 0.4W1.0mm.
NAGASHIMA TAKEO
MIZUMA MASAHIKO
SATOU KIMIHIKO
KOBAYASHI SHIGEYOSHI
OKADO SADAO
ASAHI GLASS CO LTD