Why are Coagulants Used in the Lime-Soda Process?
Just as coagulants are used for removing suspended matter in clarification processes, they serve to clump togehter precipi-tates in the softening process. Coagulants can speed up settling of sludge as much as 25 – 50 per cent. Sodium aluminate has a special advantage as a coagulant in lime-soda softening since unlike most other coagulants it is alkaline and also contributes to the softening readtions, particularly in reducing magnesium. Effective use of coagulants helps remove silica in hte softening process. Silica tends to be absorbed in the floc produced by coagulation of sludge.
