| Waste activated sludge is a concentrated dispersion of mostly microorganisms in bulk water. The physical properties of this biologically active suspension make it difficult to separate the liquid portion of sludge from the solids. Today the most challenging aspect of sludge treatment is to reduce enough of its liquid portion in an effective manner so that sludge behaves as a solid.;Water distribution in sludge is worthy of investigation due to its importance in the sludge dewatering process. Sludge contains various fractions of water associated with sludge solids. These water fractions affect the dewaterability of the sludge. Removal of some of these water fractions is not possible with conventional dewatering techniques.;In this study, sludge cell disruption is introduced as a new method to improve the compactibility of sludge. Sludge cells are disrupted by different methods including alkali treatment (chemical), NaCl treatment (osmotic), heat (thermal) and sonication (mechanical). The effect of cell disruption on water distribution and compactibility of waste activated sludge is investigated.;The results of this study indicated that the disruption of the sludge cells changes the water distribution in sludge and improves the compactibility of sludge. Disruption apparently releases from 60% to 80% of interstitial water (depending on the disruption method used) trapped in the crevices and interstitial spaces of the sludge microorganisms or within the floc structure. On the other hand, it causes creation of extra surfaces for water binding and leads to a 70% to 80% increase in the unfreezable water content (vicinal water, water of hydration, and a fraction of interstitial water) in sludge.;The cell disruption increases the solid content of the compacted sludge up to 87% depending on the cell disruption method used.;There is no strong correlation between unfreezable water content in sludge and sludge compactibility. |
