Efficient anaerobic wastewater treatment in UASB-reactors (Lettinga et al., 1980) requires a sludge possessing good methanogenic activities and good settling characteristics. Under certain conditions a granular sludge was developed in this type of reactor, meeting both these requirements. Our research is focused on the microbiological aspects of this granulation.
A method was developed for determination of the methane production rate by gas chromatography. Using the usual anaerobic techniques, small amounts of sludge were suspended into a phosphate-bicarbonate buffer (pH 7) in 130-ml serum-vials under a CO2-atmosphere. Gas analyses were performed using a pressure-lock syringe to prevent problems with pressure build-up. For the determination of maximal methanogenic activities on a variety of substrates this method provides a rapid and reliable tool. It may also be of use for the control of sludges after serious overloading, or after their exposure to toxic compounds.
Granular and non-granular methanogenic sludge was grown on wastewater from a sugar factory. There were no significant differences between the methanogenic activity patterns of the two types of sludge as measured on formate, acetate, propionate and ethanol. On sucrose, however, though not a direct substrate for methanogenic bacteria, differences were found suggesting a possible role of carbohydrate-decomposing organisms in the formation of a granular methanogenic sludge.