In the traditional view of sludge structure, a two-phase system is visualized. The solid phase is often illustrated as consisting of uniform, spherical, negatively charged particles. This simplistic picture limits the understanding of both conditioning and dewatering. Specifically, it limits us to only two strategies for destabilization: charge neutralization (using cationic coagulant species with either uniform or patch effects), and bridging (using polymeric flocculants). In fact, the situation is more complex in many respects. In this paper, we compared chemical conditioning of anaerobically digested biosolids using (1) conventional polymeric flocculation, and (2) treatment by chemical oxidants. Since these strategies may alter dewatering behavior by very different mechanisms, we report comparisons using a lab-scale simulator of belt press dewatering, including separate steps for the drainage and filtration processes. This allows greater insight into the effects of these conditioning methods and how they might be properly employed.

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