Inorganic composition and microbial characteristics of methanogenic granular sludge grown in a thermophilic upflow anaerobic sludge blanket reactor
1995
Uemura, S. | Harada, H.
An upflow anaerobic sludge blanket reactor was operated under thermophilic conditions (55 degrees C) for 160 days by feeding a wastewater containing sucrose as the major carbon source. The reactor exhibited a satisfactory performance due to the formation of well-settling granulated sludge, achieving a total organic carbon (TOC) removal of above 80% at an organic loading rate of 30 kg total organic C m-3 day-1. Structural and microbial properties of the methanogenic granular sludge were examined using scanning electron microscope X-ray analyses and serum vial activity tests. All the thermophilic granules developed showed a double-layered structure, comprised of a black core portion and a yellowish exterior portion. The interior core portion contained abundant crystalline precipitates of calcium carbonate. Calcium-bound phosphorus was also present more prominently in the core portion than in the exterior portion. Methanogenic activities of the thermophilic granules both from acetate and from H2 increased with increasing vial-test temperature in the range of 55-65 degrees C [from 1.43 to 2.36 kg CH4 chemical oxygen demand (COD) kg volatile suspended solids (VSS)-1 day-1 for acetate and from 0.85 to 1.11 kg CH4 COD kg VSS-1 day-1 for H2]. On the other hand, propionate-utilizing methanogenic activity was independent of vial-test temperature, and was much lower (0.1-0.12 kg CH4 COD kg VSS-1 day-1) than that from either acetate or H2. Acetate consumption during vial tests was considerably inhibited by the presence of H2 in the headspace, indicating that a syntrophic association between acetate oxidizers and H2-utilizing methane-producing bacteria was responsible for some portion of the overall acetate elimination by the theromophilically grown sludge.
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