PURPOSE: To prevent bacteria contamination of the hollow yarn separating membranes in a potable water forming device by eliminating the need for a carbon dioxide dissolving tank and diluting stage of the conventional potable water producing apparatus.
CONSTITUTION: A water feed piping 10 to a carbonate-contg. material packed column 50 is provided with a flow meter 12 and a carbon dioxide supply piping 14 to this carbonate- contg. material packed column 50 is provided with a valve 20. Opening and closing of the valve 20 are controlled in accordance with the measured value of the flow meter 12 by a controller 30. The potable water forming device 50 is provided with a washing water introducing port for supplying city water to the hollow yarn separating membranes 64 in this device and a drain port. Then, low-concn. carbonate water of ≤200ppm is sufficiently obtd. in a piping and the stagnating part in the upper part in the carbonate-contg. material packed column 50. The amt. of the carbon dioxide is adjusted according to the volume of the feed water and the low-concn. carbonated water adjusted in concn. is supplied into the carbonate- contg. material packed column 50, by which the water of the sufficiently low carbon dioxide concn. is obtd. even at the desired concn. of the heavy carbonate hardness component. The hollow yarn separating membranes are washed by the city water, by which the contamination with bacteria and the generation of the smells occurring in propagation of the bacteria are effectively prevented.
NAKANO YOSHIMASA
NOZUE MITSURU
