CHANGES IN DEWATERING PROPERTIES BETWEEN THE THERMOPHILIC AND MESOPHILIC STAGES IN TPAD SYSTEMS
Abstract:Temperature-phased anaerobic digestion (TPAD) has become increasingly appealing in recent years due to the pathogen destruction capabilities of the system. However, there has also been concern about the dewatering properties of the sludges created by these systems. A laboratory study was conducted at Virginia Tech to determine the effect of thermophilic solids retention time (SRT) on sludge dewatering properties, to characterize system parameters associate with dewatering, and to understand the mechanisms causing changes in dewatering properties between the thermophilic and mesophilic phases. The study showed that while anaerobic digestion caused dewatering properties to deteriorate, sludges varied little with thermophilic SRT. Acidogenesis was essentially complete with 1.5 days of thermophilic digestion. Subsequent mesophilic digestion resulted in little change in dewatering properties and modest reductions in conditioning doses, but substantial reductions in biopolymer (protein + polysaccharides) occurred. It appears that thermophilic anaerobic digestion creates or releases materials that cause dewatering to be poor and mesophilic digestion for 15 days did little to improve sludge properties.
Document Type: Research Article
Publication date: January 1, 2000
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