MASS-TRANSFER AND TEMPERATURE EFFECTS ON SUBSTRATE UTILIZATION IN BREWERY GRANULES

Liquid film and diffusional resistances of brewery granules during ace tate, propionate, and ethanol utilization were investigated. Substrate utilization rate increased with decreased granule size. Effectiveness factors for acetate, propionate, and ethanol were calculated by compa ring the maximum rates of substrate utilization of whole granules (1.8 to 3.0 mm) and fine flocs (20 to 75 mu m) derived by disrupting whole granules. For acetate, propionate, and ethanol, maximum specific subs trate utilization rates (k(m), g/g VS.d) for the flocs, were 5.11, 6.2 5, and 5.49, respectively, and half-velocity coefficients (K-s, mM) we re 0.45, 0.40, and 3.37, respectively. Calculated effectiveness factor s were 0.32, 0.41, and 0.75 for acetate, propionate, and ethanol, resp ectively. The effect of temperature on substrate utilization was exami ned at 26 degrees C, 31 degrees C, and 37 degrees C using acetate as s ole carbon source. Utilization rates increased with temperature. Flocs were most sensitive to temperature, and whole granules were least aff ected. The behavior of flocs was well described by the Van't Hoff-Arrh enius equation. Effectiveness factors for acetate utilization by the g ranules were 0.36, 0.35, and 0.32 at 26 degrees C, 31 degrees C, and 3 7 degrees C, respectively, indicating little effect of temperature. Ba sed on these results, we conclude that both liquid film and diffusiona l resistances influenced the rate of substrate utilization in a UASB r eactor with granular sludge. Temperature effects were much less import ant than diffusional limitations within the granules. (C) 1995 John Wi ley & Sons, Inc.