A simple and low cost technique for determining the granulometry of upflowanaerobic sludge blanket reactor sludge

Four techniques (microscope sizing, calculation from settling velocities, i mage and laser analysis) are available nowadays for determining the particl e size distribution of upflow anaerobic sludge blanket (UASB) reactor sludg e. These techniques present however the disadvantage of being either tediou s, imprecise or expensive and hardly applicable in full scale treatment pla nts. There was then the need for a simple and low cost technique. In this s tudy, a granulometry procedure based on manual humid sieving was evaluated. It was shown that no solid loss occured during the screening and that the particle size profiles were reproducible when performed with sludge samples of 5, 10, 25 and 150 mi, but not I mi. Only the results between 10 and 25 mi were however fully identical. It was shown also that the sieving could b e performed on sludge samples stored for as long as 50 days at refrigerator temperature and that tap water could be use for the wash and backwash oper ations without any impact on the particle size profile. The granulometry ob tained by image analysis was not comparable to that given by sieving. Never theless, no evidence of granule erosion could be found. In any case, the te chnique allowed us to follow the evolution of sludge granulometry perfectly over time. As a consequence, the manual humid sieving appears to be an ade quate technique for determining the granule size distribution of UASB sludg es. (C) 1999 Published by:Elsevier Science Ltd on behalf of the IAWQ. All r ights reserved.