To remarkably the regenerating salt to be supplied to a salt water tank and lighten the man power necessary to throw a salt to the tank, by selectively recovering a portion containing an unused regenerated salt from wastewater at the time of regenerating a cation-exchange resin and reusing the recovered salt as a regenerated salt.
In the water softening apparatus 1 comprising a resin cylinder 2 filled with a cation exchange resin and a salt water tank 3, after a prescribed amount of raw water (hard water) is converted into soft water by the function of a cation exchange resin, the cation exchange resin is regenerated by carrying out processes of back washing, regenerating with salt water, washing with water, etc. At that time, the discharged salt concentration in the wastewater (containing unused salt for regeneration) flowing in a water discharging line 6 is detected by an electric conductivity meter 9 and at the time when the discharged salt concentration reaches a prescribed concentration, an automatic valve 10 is closed and an automatic valve 12 is opened to store the wastewater in a regenerating wastewater tank 13. After that, the wastewater is separated into unused salt water for regeneration and dewatered salt by an electrodialyser 14 and the separated unused salt water for regeneration is turned back to the treatment tank from a regenerating and recovering tank 16.
WAKASA AKIRA
UKIANA YUJI
ASAMURA HITOSHI
OGURA TAKEKAZU
MIHARA ATSUSHI
MIURA KENKYUSHO KK
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