Effect of organic polyelectrolytes on sedimentation properties of post-coagulation sludge

A study was carried out into sedimentation of sludge obtained in the process of coagulation-flocculation of pulp and paper wastewater with the use of PAC and organic polymers. An attempt was made to evaluate the effect of various organic polyelectrolytes on phase separation effectiveness. It was found that the application of cationic polymers at a dose of 1 mg dm –3 and 1.5 mg dm –3 (Z 63 and Z 92, respectively) in combination with PAC had a positive effect on the reduction in the sludge volume when compared with the sludge volume obtained in the process of coagulation with PAC without a flocculant. It was also noted that following the application of the optimum dose of either cationic or anionic polymers the sedimentation period was considerably reduced from 60 min (sample without flocculants) to even 30–35 min.