The effect of grain size on flocculant preparation

[Display omitted] •Filtration of flocculant solutions could improve the reproducibility of results.•With grain size the ageing required for flocculant preparation increased.•Size reduction of flocculant grains could decrease the required ageing.•A larger maximum gel size resulted from a coarser grain requires a longer ageing. High molecular weight polymers used in flocculation are manufactured mostly as dry granules. The efficiency of solid–liquid separation and polymer consumption are both affected by flocculant solution preparation. In this research, the effects of grain size, grain size reduction and solution ageing of an anionic high molecular weight flocculant on its preparation were investigated. Settling rate with a standard slurry was used as a measure of flocculant preparation effectiveness. The heterogeneity of solutions due to the presence of polymer gels was reduced by filtration. Results indicated that with smaller grain sizes, a shorter ageing would be required to achieve a certain settling rate. Furthermore, it was concluded that size reduction of a coarse grain flocculant could decrease the appropriate time for ageing.