Evolution of microbial activities and population in granular sludge from an UASB reactor

Summary With granular sludges grown in an UASB reactor fed with a mixture of acetate and proplonate, it is shown that (I) growth of proplonate-utilizing bacteria is responsible for the increase of the VSS content of the granular sludge, acetoclastic microfiora did not grow or little, (II) there is not a stolchlometric relationship between substrate removal and observed methane production, and (III) contrary to the common practice the best way to present data on bacterial concentrations in sludges is: bacteria/g VSS, which will provide a reliable basis for comparisons between different works from various authors.