METHOD OF SOFTENING WATER Russian patent published in 1998 - IPC

FIELD: water treatment. SUBSTANCE: tripotassium phosphate is added to water under boiling and stirring. Amount of additive is determined by formula: K=H_t-H_r where K is amount of additive needed to lower total hardness of water by 1 mmol (equal to 0.032-0.035 g/l); H_t total hardness of water in given region, mmol/l; and H_r residual hardness of water, mmol/l. Precipitate is settled down, stirred once again, and settled for further 5-10 min. Clarified water is separated. Once tripotassium phosphate added, boiling can be resumed for no longer than 1 min. After repeated settling, upper layer can be additionally stirred and settling continued. EFFECT: enabled softening water with total hardness 30 mmol/l and higher, and eliminated use of toxic reagents. 3 cl