Evaluation of odor characteristics of heat-dried biosolids product

Because it produces an exceptional quality pellet product, heat drying of wastewater solids from municipal wastewater treatment plants is becoming more prevalent as biosolids management regulations become more restrictive. The product from heat drying is sometimes odorous as dry or 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 this study were to determine odor characteristics and to compare the odors produced by evaluating odors from four types of heat-dried biosolids products: all undigested; primary digested-waste activated sludge (WAS) undigested; all digested; and WAS lime stabilized pellets. The results are described in this paper.