The influence of hydraulic retention time (HRT) and gelatin concentration on the acidification of gelatinaceous
wastewater in an upflow anaerobic reactor was investigated at pH 5.5 and 37 °C. The degree of gelatin degradation
increased with the HRT, from 84.1% at 4 h to 89.6% at 24 h, but decreased with the increase of the gelatin
concentration in the influent from 65.2% at 2 g-COD l−1 to 51.9% at 30 g-COD l−1
. The degradation of gelatin
followed the Monod kinetics with a maximum rate of 1.10 g (g-VSS·d)−1 and a half-rate constant of 0.23 g l−1
. The
overall production rate of VFA and alcohols decreased with HRT, from 0.33 g (g-VSS·d)−1 at 4 h to 0.15 g
(g-VSS·d)−1 at 24 h, but increased with gelatin concentration in the influent, from 0.10 g (g-VSS·d)−1 at 4
g-COD l−1 to 0.58 g (g-VSS·d)−1 at 30 g-COD l−1
. The key acidification products were acetate, propionate and
butyrate, plus i-butyrate, valerate, i-valerate, caproate and ethanol in smaller quantities. Formate, methanol,
propanol and butanol were found only in certain runs. Only 4.5–7.8% of COD in wastewater was converted to
hydrogen and methane. The sludge yield was estimated as 0.3200.014 g-VSS (g-COD)−1
. © 2002 Elsevier Science
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