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Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates
Journal article   Open access   Peer reviewed

Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates

W. Charles, N.P. Carnaje and R. Cord-Ruwisch
Water Science & Technology, Vol.64(2), pp.534-539
2011
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Abstract

The anaerobic digestion process is globally applied to the treatment of highly concentrated wastes such as industrial and rural effluents, and sewage sludge. However, it is known to be relatively unstable. When loaded with high concentrations of organic material, unwanted volatile fatty acids (VFA) are often produced rather than methane (CH(4)) gas which can lead to digester acidification and failure. This study investigated digester behaviour under high loading rates, testing the usefulness of stoichiometric methane conversion efficiency as a digester control parameter at high loading rates. Our results show that, in general, the CH(4) production rate was proportional to the feed rate (loading rate). However, at very high loading rates, the CH(4) production rate was not proportional to the increase in the feeding rate. Consequently, VFA accumulated and the H(2) partial pressure increased. The proportionality of the loading rate and gas production rate is stoichiometrically expressed as the conversion efficiency. We found that conversion efficiency was a useful indicator as an early warning of digester imbalance. The digester remained stable at conversion efficiencies above 75%. Dropping below 70% signified the onset of digester failure. As loading rate and methane production data are readily available on-line in most anaerobic digestion plants, the conversion efficiency can be monitored on-line and used as an efficient control technique to maintain safe operation of anaerobic digesters at high loading rates.

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Citation topics
3 Agriculture, Environment & Ecology
3.83 Bioengineering
3.83.416 Anaerobic Digestion
Web Of Science research areas
Engineering, Environmental
Environmental Sciences
Water Resources
ESI research areas
Environment/Ecology
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