Volatile fatty acids as indicators of process imbalance in anaerobic digestors

In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators.

[1]  D. L. Day,et al.  Effects of temperature change on the stability of thermophilic fermentation of swine manure , 1986 .

[2]  P. Westermann,et al.  Product Inhibition of Butyrate Metabolism by Acetate and Hydrogen in a Thermophilic Coculture , 1988, Applied and environmental microbiology.

[3]  R. Gourdon,et al.  Effects of propionic acid concentration on anaerobic digestion of pig manure , 1987 .

[4]  F. G. Pohland,et al.  Anaerobic Biological Treatment Processes , 1971 .

[5]  J. Zeikus,et al.  Metabolic properties and kinetics of methanogenic granules , 1993, Applied Microbiology and Biotechnology.

[6]  R. Mah.  Anaerobic biological treatment processes , 1971 .

[7]  G. Vogels,et al.  Inhibition of propionate degradation by acetate in methanogenic fluidized bed reactors , 2005, Biotechnology Letters.

[8]  W. Gujer,et al.  Conversion processes in anaerobic digestion , 1983 .

[9]  D. T. Hill,et al.  A Comprehensive Dynamic Model for Animal Waste Methanogenesis , 1982 .

[10]  Irini Angelidaki,et al.  Anaerobic thermophilic digestion of manure at different ammonia loads: Effect of temperature , 1994 .

[11]  K. Wuhrmann,et al.  Kinetic parameters and relative turnovers of some important catabolic reactions in digesting sludge , 1978, Applied and environmental microbiology.

[12]  H. R. Isaacson,et al.  Thermophilic methane production from cattle waste , 1977, Applied and environmental microbiology.

[13]  D. T. Hill,et al.  Long chain volatile fatty acid relationships in anaerobic digestion of swine waste , 1988 .

[14]  Robert F. Hickey,et al.  Monitoring of the anaerobic methane fermentation process , 1990 .

[15]  B. Ahring,et al.  A mathematical model for dynamic simulation of anaerobic digestion of complex substrates: Focusing on ammonia inhibition , 1993, Biotechnology and bioengineering.

[16]  D. Lovley,et al.  Intermediary Metabolism of Organic Matter in the Sediments of a Eutrophic Lake , 1982, Applied and environmental microbiology.

[17]  E. Samain,et al.  Isomerization between n‐butyrate and isobutyrate in enrichment cultures , 1988 .

[18]  D. Boone,et al.  Terminal Reactions in the Anaerobic Digestion of Animal Waste , 1982, Applied and environmental microbiology.

[19]  F. W. Gilcreas,et al.  Standard methods for the examination of water and waste water. , 1966, American journal of public health and the nation's health.

[20]  E. L. Iannotti,et al.  Anaerobic digestion of swine manure at various influent solids concentrations , 1984 .

[21]  B. Schink,et al.  Anaerobic degradation of isobutyrate by methanogenic enrichment cultures and by a Desulfococcus multivorans strain , 2004, Archives of Microbiology.

[22]  D. T. Hill,et al.  Digester stress as related to iso-butyric and iso-valeric acids , 1989 .

[23]  D. T. Hill,et al.  Using volatile fatty acid relationships to predict anaerobic digester failure. , 1987 .

[24]  M. J. Allison.  Production of branched-chain volatile fatty acids by certain anaerobic bacteria , 1978, Applied and environmental microbiology.