A TREND IN BIOSOLIDS PROCESSING: THERMAL DRYERS REPLACE MULTIPLE HEARTH INCINERATORS

Thermal drying of sludge provides many of the same advantages, volume and pathogen reduction, that are attributed to incineration. Further, thermal drying systems have some additional advantages in comparison with incineration:Production of a Class A biosolids product suitable for beneficial reuse.No combustion of sludge resulting in lower air emissions.Compatibility with anaerobic digestion, including use of digester gas for dryer fuel and potential recovery of waste heat from dryer for digester heating.Also, in many cases, a cost savings can be achieved for thermal dryer installations by reusing existing incinerator buildings, since there are similar space requirements for drying and incineration. While incineration remains a viable option for many facilities, this paper examines cases where incineration was replaced by heat drying with a discussion of the factors that led to the decision.