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Failure monitoring of full scale and laboratory scale anaerobic digesters and evaluation of recovery options
Conference paper   Open access

Failure monitoring of full scale and laboratory scale anaerobic digesters and evaluation of recovery options

G. Chiew and R. Cord-Ruwisch
Murdoch University
International Conference on "Appropriate Waste Management Technologies" (Perth, Western Australia, 27/11/1991–28/11/1991)
1991
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Abstract

Laboratory scale experiments and measurements on full scale, overloaded, anaerobic digesters showed that large levels of volatile fatty acids can accumulate leading to digester acidification, although the hydrogen partial pressure was relatively low <120 ppm). However, the exact hydrogen measurements showed a significant difference between failing and healthy digester sludge: the hydrogen partial pressure in healthy digesters was between 10 and 40 ppm, whereas hydrogen partial pressures of 60 to 120 ppm indicated digester failure. In the full scale digesters the raised hydrogen level did not allow propionate degradation resulting in propionate buildup to more than 60 mM over a period of 40 days. Propionate degradation was never observed as long as the hydrogen level was higher than 50 ppm. On the other hand, propionate accumulation was triggered by small increases in hydrogen partial pressures from 20 to 70 ppm. The findings show that the measurement of fluctuations in trace concentration of hydrogen but not the accumulation of large hydrogen concentrations (> 1,000 ppm) is a useful tool for digester monitoring. In the laboratory, the addition of concentrates of hydrogen consuming methanogenic bacteria, or of starved anaerobic sludge (30 to 50%) from secondary digesters, resulted in recovery of the failed digester sludge.

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