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The role of intermediate and product gases as regulators and indicators of anaerobic digestion
Abstract
The anaerobic treatment of wastewaters and sludges, in many instances, offers significant advantages on both cost and efficiency bases. The historical perception of unreliability coupled the very real potential for significant deterioration of process efficiency, as a consequence of toxicant induced inhibition, and concominant protracted recovery period has retarded the application of anaerobic treatment. There exists a need to better monitor the anaerobic digestion process so that process control options can be implemented in a timely fashion to avoid or mitigate upset of the process due to toxicant addition as well as organic and hydraulic overloads. A combination of short-term batch assays and longer term continuous experiments were performed with anaerobic sludge digester inocula and laboratory digesters monitored in an on-line mode, respectively. Two trace gases, hydrogen and carbon monoxide, were investigated as potential process indicators. The responses of these trace gases to upsets causes by pulse addition of a series of organic and inorganic toxicants as well as step changes in organic and hydraulic loading were investigated. The hydrogen response pattern appeared to be indicative of where the interruption or back-up in substrate flow occurred. Hydrogen displayed characteristic but different response patterns for inorganic and organic toxicant induced inhibition but did not provide significant indication of upset due to organic overloading. Carbon monoxide also displayed characteristic response patterns to toxicant induced inhibition. In addition, it was observed that under normal and overload (organic and hydraulic) conditions carbon monoxide concentrations were directly related to acetate concentrations. Because of this, carbon monoxide appears to be an excellent surrogate measure of acetate levels in digester systems that can be quickly and conveniently measured either discretely or in an on-line mode. A thermodynamic model that accurately describes the behavior of carbon monoxide as a function of acetate and several other gases was constructed. Based on this preliminary research it appears monitoring both hydrogen and carbon monoxide lends significant insight into the metabolic status of the digestion process. Trace gas monitoring, therefore, appears to hold promise as a technique to better monitor and control anaerobic treatment systems.
Subject Area
Civil engineering
Recommended Citation
Hickey, Robert Francis, "The role of intermediate and product gases as regulators and indicators of anaerobic digestion" (1987). Doctoral Dissertations Available from Proquest. AAI8805926.
https://scholarworks.umass.edu/dissertations/AAI8805926