Tools for Modeling Sludge Digestibility
Abstract:The objective of this study was to identify methods for estimating the anaerobic digestibility of waste activated sludges. Waste activated sludge streams were generated in three sequencing batch reactors treating screened municipal wastewater. The wastewater and waste activated sludge properties were initially determined through fitting of the Biowin process simulator to data that was collected during a 15 day intensive sampling event. Samples of the waste activated sludge streams from the SBR's were subsequently characterized through aerobic respirometry and batch anaerobic digestion. Respirometry proved to be an effective tool for characterizing the active heterotrophic fraction of waste activated sludges and could serve as a suitable technique for determining sludge composition for input to anaerobic models where reliable simulation of the wastewater treatment plant is not possible. Anaerobic digestion of the waste activated sludges revealed decreasing CH4 production and correspondingly lower COD removals as the SRT of the sludge increased. The Biowin simulator was capable of accurately describing the digestion of the waste activated sludge samples for SRTs that are typically employed in practice. For extended digestion times (i.e. greater than 30 days) model simulations consistently underpredicted the extent of digestion. Incorporation of a first order decay mechanism for the endogenous decay products with a rate constant of 0.0075 d−1 into the model resulted in accurate simulations for all sludge SRTs.
Document Type: Research Article
Publication date: January 1, 2008
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