Improving activated sludge floc structure and aggregation for enhanced settling and thickening performances

The effluent quality of a sewage plant using the activated sludge process depends upon the flocculation efficiency. Intensive research work has been devoted to understanding flocculation phenomena and to correct biological disorders, The addition of very fine but dense mineral particles to the aeration tank immediately improves flee formation and increases the weight of the new flocs created. The first consequence is an effective separation between the solid and the liquid phases in the secondary clarifier. In the longer term, the fine particles improve floc structuring and Form stable and strong flocs. This has been demonstrated by sending a modified activated sludge through the high shear strength of pumps and hydrocyclones. The mineral of choice is a natural blend of talc and related minerals. These fine talc particles offer a solution to solve flee settleability problems which so frequently arise when biological disorders appear in waste water treatment plants. Despite the addition of insoluble particles the amount of sludge expelled does not increase. The thickening and dewatering properties are improved. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.