Technical Bulletin No. 0158: Evaluation of Fly Ash as a Filter Aid for Precoat Vacuum Filtration of Papermill Sludges

The attached Technical Bulletin was originally distributed in July 1962. It was noted then that the hydrous sludges produced by clarification of some paper mill effluents and biological treatment processes were not readily dewaterable by common methods of vacuum filtration or solid bowl centrifugation. It was believed that their vacuum filter dewatering could be enhanced by precoat filtration using diatomaceous earth or carbonaceous filter aids. Since the cost of such materials is quite high, it was felt that fly ash generated at those mills burning pulverized coal might find application as a substitute precoat filter aid, particularly since the fly ash itself required disposal.  A group of Ohio and Michigan member mills assisted the study by making available additional technical personnel, and providing samples of deinking and board mill sludges and fly ash for the project. The laboratory results obtained then appeared sufficiently promising to warrant larger scale trials than possible with leaf test filter units.