Date of Award

Summer 2007

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Civil, Construction, and Environmental Engineering

First Advisor

Zitomer, Daniel H.

Second Advisor

Switzenbaum, Michael S.

Third Advisor

Crandall, Clifford J.


When increased organic loading occurs in anaerobic treatment systems, volatile fatty acids (VFAs) build up in the system, causing a decrease in pH that leads to the cessation of methane production and a "stuck" digester that can no longer meet treatment requirements. Methods for recovery from this type of upset would be very useful and increase the attractiveness of the anaerobic process as a treatment option. In this study, nitrate, a substance released by common industrial and agricultural practices, which is knowm to inhibit methanogenesis was added to serum bottle anaerobic digesters and the organic loading was increased to stress the systems. Bioaugmentation with an enrichment culture of methanogenic organisms acclimated to nitrate was then applied to study it as an option for increasing the rate of system recovery. There were three sets of reactors in the study, each with five replicates. The control set received only nutrients and non-fat dry milk, as a source of COD. An autoclaved augmentation set and a bioaugmentation set received those same substances and an augmentation of either an autoclaved sample of the enrichment culture or a live sample of the enrichment culture, respectively. These reactors were rum at a 10-day solids retention time (SRT). Over the course of the study, the effluent pH, VFA and soluble COD concentrations, volume of biogas production, and percent methane in headspace gas were measured...



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