Evaluation of Odor Characteristics of Heat-Dried Pellets

Heat drying of wastewater solids from municipal wastewater treatment plants is becoming prevalent as biosolids management regulations become more restrictive, since it produces an exceptional quality (EQ) pellet product. The product from heat drying is sometimes odorous as dry pellets or as ‘wetted’ pellets. The odors, although not regulated, can be important for marketability and public acceptance of the product. The reasons for the odors are usually a result of upstream processing and management of wastewater solids prior to drying. The goals of the study were to determine the odor characteristics and to compare the odors produced from different types of heat dried pellets. This study evaluated the odors from four types of heat dried biosolids. These pellets included 1). All undigested, 2). Primary digested, waste activated sludge (WAS) undigested, 3). All digested, and 4). WAS lime stabilized. The results are described in the paper.