Variation of bulk properties of anaerobic granules with wastewater type

Development of a granular sludge with high strength, high biological activi ty and a narrow settling distribution is necessary for optimal operation of high-rate upflow anaerobic treatment systems. Several studies have compare d granules produced from different wastewaters but these have largely been from laboratory-fed reactors or compared granules from full-scale reactors fed similar wastewater types. Though two authors have commented on the infe riority of granules produced by a protein-based feed, the properties of the se granules have not been characterised. In this paper, granules from full- scale reactors treating fruit and vegetable cannery effluent, two brewery e ffluents and a pig abattoir (slaughterhouse) were compared in terms of basi c composition, size distribution, density, settling velocity, shear strengt h, and EPS content. The results supported previous qualitative observations by other researchers that indicate granule properties depend more on waste water type rather than reactor design or operating conditions such as pre-a cidification level. The cannery-fed granules bad excellent shear strength, settling distribution and density. Granules from the two brewery-fed reacto rs had statistically the same bulk properties, which were still acceptable for upflow applications. The protein-grown granule had poor strength and se ttling velocity. (C) 2001 Elsevier Science Ltd. All rights reserved.