Abstract
Physical, chemical and biological changes in the upflow anaerobic sludge blanket (UASB) granules were investigated after the substrate was changed from brewery to methanolic waste. The granular sludge required 5-6 weeks for acclimatization (start-up) and this period accounted for the changes that the granules exhibited. Sharp decrease in settling velocity was accompanied by decrease in ash content and a reciprocal increase in the volatile solids content. The mineral content and the extracellular polymer fraction of the granular sludge reduced to 67%and 74%of the initial value respectively. Hydrogenotrophic and acetoclastic methanogenic groups seemed to be the two predominant methane forming groups in the granular sludge before and after the substrate shift. The results of this study demonstrate that change in substrate bring about physical, chemical and biological changes in the granular methanogenic sludge but may not impede its biological conversion capabilities provided that favorable environmental conditions are maintained.
