Degree Type

Dissertation

Date of Award

1988

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

First Advisor

Richard R. Dague

Abstract

Three different configurations of cylindrical submerged media anaerobic reactors (SMARs) with packing volumes of 85 L were operated at 35°C for 415 days with COD loading rates varying from 1 to 12 g/L/d and three retention times of 0.5, 1, and 2 days. A synthetic waste consisting of a milk solution with a mineral supplement was used for the feed;Tracer studies on clean-bed and dirty-bed SMARs indicate that reactor configuration, biogas mixing, and biomass accumulation all have a significant effect on SMAR hydraulics and cause short-circuiting. The actual retention time can be reduced to as low as 0.6 of the theoretical retention time;Based on the isothermal energy dissipation theory, the higher hydrostatic pressures resulting from higher SMAR heights increases self-induced biogas mixing and improves the contact efficiency between substrate and organisms;Based on TCOD removal rate, the tallest SMAR performed slightly better at COD loading rates above 4 g/L/d. At COD loading rates equal to or below 4 g/L/d, there was little difference in TCOD removal rate between the three SMARs;The acetoclastic methanogenic activity (AMA) test developed in this study is reproducible within 6.5% at a mean of 0.39 L CH[subscript]4 (STP)/gm VSS/d. For VSS less than 1 g/L, a higher AMA is associated with lower VSS concentrations. For VSS greater than 1 g/L, AMA varies within a narrow range of 0.1 to 0.2 L CH[subscript]4 (STP)/gm VSS/d;Exit gas recycle at a ratio of 3.5-7.0% of exit gas flowrate resulted in a 5-13% increase in the methane content of the exit gas at a COD loading rate of about 10 g/L/d and a detention time of about 2 days. This suggests that, at high loading rates, hydrogen dissolution rate may be the rate-limiting step in anaerobic digestion.

DOI

https://doi.org/10.31274/rtd-180813-12566

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Chow-Feng Chiang

Language

en

Proquest ID

AAI8825378

File Format

application/pdf

File Size

287 pages

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