Article Abstract:
A novel approach for the high-rate anaerobic treatment of wastewater at low temperatures is presented. The proposed method is tested on a volatile fatty acid mixture under psychrophilic conditions in two laboratory-scale expanded granular sludge bed reactor stages in series. Results show that good removal of fatty acids is made possible in the two-stage system, with relative high concentrations of propionate present in the effluent of the first stage. Propionate is efficiently eliminated in the second stage, in which there is a low hydrogen partial pressure and a low acetate level that boost propionate oxidation.
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Article Abstract:
The enrichment of syntrophic, thermophilic propionate-oxidizing bacteria was discussed. The cultures were grown with either Methanobacterium hermoautotrophicum deltaH and M. thermoficicum Z245 from the granular methanogenic sludge of an anaerobic sludge bed reactor at 55 degrees centigrade using volatile fatty acids as feed. The study showed that the formates prevent the oxidation of succinates to fumarates which is a critical step in propionate oxidation. However, addition of methanogens neutralized the inhibitory action of formates on propionate oxidaiton.
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Article Abstract:
Changes in the thermophylic oxidation of propionate in continuous-flow methanogenic sludge bed systems and in defined propionate-oxidizing cultures due to acetate, propionate and butyrate were discussed. Gas chromatography and kinetic analysis were conducted on the resulting data from the inhibition experiments. The inability of hydrogen as a control parameter for propionate degradation was esablished.
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