Effect of feed composition and upflow velocity on aggregate characteristics in anaerobic upflow reactors |
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Authors: | V O'Flaherty P N L Lens D de Beer E Colleran |
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Institution: | (1) Environmental Research Unit, Department of Microbiology, University College, Galway, Ireland. Fax: 353 91 525700 e-mail: emer.colleran@ucg.ie, IE;(2) Laboratory of Microbial Ecology, Faculty of Agricultural Science, Coupure L-653, Gent, Belgium, BE |
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Abstract: | Two upflow anaerobic hybrid reactors treated lactose and a mixture of ethanol, propionate and butyrate, respectively, at
a volumetric loading rate of 3.7 kg chemical oxygen demand (COD) m−3day−1, a hydraulic retention time of 5 days and a liquid upflow velocity of 0.01 m/h. Under steady-state conditions, the lactose-fed
sludge had much higher (20%–100%) specific methanogenic conversion rates than the volatile-fatty acid␣(VFA)/ethanol-fed sludge
for all substrates tested, including VFA. In both reactors, a flocculant sludge developed, although a much higher content
of extracellular polysaccharide was measured in the lactose-fed sludge 1900 μg compared to 305 μg uronic acid/g volatile
suspended solids (VSS)]. When the liquid upflow velocity of a third, VFA/ethanol-fed reactor was increased to 0.5 m/h, granulation
of the sludge occurred, accompanied by a large increase (200%–500%) in the specific methanogenic conversion rates for the
syntrophic and methanogenic substrates studied. Granulation reduced the susceptibility of the sludge to flotation. Glucose
was degraded at a high rate (100 mg glucose gVSS−1h−1) by the sludge from the third reactor, despite not having been exposed to a sugar-containing influent for 563␣days.
Received: 7 June 1996 / Received revision: 23 September 1996 / Accepted: 29 September 1996 |
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