BIOASSAY FOR GLYCOGEN DETERMINATION IN BIOLOGICAL PHOSPHORUS REMOVAL SYSTEMS

Glycogen plays an important role in biological phosphorus removal from wastewaters. Existing measurement techniques often overestimate the g lycogen content of the biomass due to the presence of glucose and/or e ther carbohydrates than glycogen in the cell material. As an alternati ve to conventional methods a bioassay for glycogen determination in bi ological phosphorus removal systems was developed. The bioassay is bas ed on the strict stoichiometric coupling between anaerobic acetate upt ake and glycogen consumption. In other words, the glycogen concentrati on of the sludge was determined indirectly by measuring the maximal to tal acetate uptake by the activated sludge in anaerobic batch tests. T he bioassay was successfully tested for the determination of glycogen content of the sludge taken from the lab-scale, acetate-fed, anaerobic -aerobic-settling sequencing batch reactor operating at pH 7+/-0.1 and temperature of 20 degrees C. This determination of glycogen requires that glycogen (not poly-P) is the limiting factor for anaerobic acetat e uptake. A method to verify this assumption based on the effect of pH on phosphate/acetate ratio is proposed and used. The bioassay is easy to apply and gives a direct measure of the glycogen content of bio-P bacteria, but its reliability still needs to be verified at full-scale biological P-removal plants. (C) 1998 IAWQ. Published by Elsevier Sci ence Ltd.