Lime as a flocculation agent

 

One of the purposes of using lime is to enhance liquid-solid separation efficiency of sludge, i.e. remove bound water incorporated in the structure in which fine particles are dispersed (mutual repulsion by negative surface charges), in order to obtain a dryer and better workable sludge with enhanced storage properties (angle of repose).

 

By lime addition, particles are neutralised, destabilised and form micro-flocks first and then bulky floccules, which will settle. 

 

 

 

	Lime addition as a chemical cationic agent

This flocculation effect is reinforced through the additional use of metal salts (from iron or alumina) and/or polymers.  

 

Combined with lime, salts of Fe₃₊ and Al₃₊ through pH increase transform into amorphous gels Fe(OH)₃ and Al(OH)₃ which perform as inorganic polymers acting as bridge between particles.

 

Polymers high molecular weight   Floc reinforcement by bridging