Influence of Biocolloids and Biocolloidal Structure on the Dewaterability of Anaerobically Digested SludgeEPA Grant Number: R823486
Title: Influence of Biocolloids and Biocolloidal Structure on the Dewaterability of Anaerobically Digested Sludge
Investigators: Darby, Jeannie L.
Current Investigators: Darby, Jeannie L. , Poxon, Theresa L. , Tsuchihashi, Ryujiro
Institution: University of California - Davis
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1995 through September 1, 1997
Project Amount: $132,678
RFA: Exploratory Research - Engineering (1995) Recipients Lists
Research Category: Engineering and Environmental Chemistry , Land and Waste Management
Description:This project will be carried out based on a new conceptual model of digested sludge, in which it is hypothesized that in anaerobically digested sludge, extracellular biocolloids are present in concentrations sufficient to form gel-like structures that significantly restrict water mobility within the sludge.
The objectives of this project are to gain a better understanding of the influence of biocolloids and biocolloidal structure on sludge dewatering characteristics and conditioning mechanisms and to investigate the practical significance of the new conceptual model. Specific research objectives are: (1) to determine the existence and extent of biocolloidal structure in anaerobically digested sludges; (2) to define correlations between structure, particle size, and dewaterability in digested sludges under differing conditions; and (3) to determine the effect of various conditioning agents on sludge structure. The emphasis on biocolloidal structure central to this research represents a shift away from the currently accepted particle based model of sludge dewaterability.
Physical characteristics of anaerobically digested sludges from wastewater treatment plants before and after conditioning will be examined as well as the visualization of the sludges through light and scanning electron microscopy. Ammonium sulfate and ruthenium red will be used as conditioning agents.
The results of these experiments will provide evidence to test the new conceptual model as well as insights regarding mechanisms of sludge dewatering and conditioning. These results will have potential ramifications in the areas of design and operation of anaerobic digestion processes and the development of new sludge conditioning strategies. The research will be of benefit to design engineers and municipalities considering approaches to dewater digested sludge.