Abstract: An alkaline stabilization process for treating partially dewatered sludge while reducing lime consumption, increasing nutrient values and applicability of the product, and enhancing physical handling characteristics such as dryness, granularity and spreadability including feeding a predetermined amount of partially dewatered sludge to a first mixer, adding a predetermined amount of alkaline material to the sludge in the first mixer, mixing the sludge and alkaline material together in the first mixer to form a mixture, discharging the mixture from the first mixer, directing the mixture to a second mixer, adding a predetermined amount of end product enhancing additive to the second mixer, mixing the mixture and end product enhancing additive in the second mixer to form an end product and discharging the end product from the second mixer.

Abstract: A process for the production of a durable granular or pelletized sludge product is disclosed whereby a minimal amount of high calcium oxide material is utilized for pathogenic stabilization, a portion of the resulting hot mixture being recycled back to the mixing stage to reduce the requisite lime consumption by utilizing unreacted lime, for energy recovery and to increase dryness.

Abstract: A process for the production of a durable granular or pelletized sludge product is disclosed whereby a minimal amount of high calcium oxide material is utilized for pathogenic stabilization, the resulting material being further processed through an agglomeration stage. A portion of the agglomerated material is further processed in a moisture reduction or drying stage and recycled back to the agglomeration stage for percent solids adjustment and promotion of agglomeration. An apparatus for performing the process is also disclosed.

Abstract: Dewatered municipal sludge is dried and simultaneously pelletized in an indirect dryer. A sweep air is introduced into the dryer to extract a water vapor and air mixture. The water vapor and air mixture is condensed and cleaned in a condensor and a scrubber to obtain a clean non-condensable gas. The non-condensable gas is heated and recycled to the dryer after heating for use as the sweep air. Since air leakage into the system is inevitable, an excess amount of air accumulates that does not need to be recycled to the dryer. The excess amount of air is diverted from the recycled sweep air and thermally treated to destroy any malodorous gaseous constituents contained therein. Preferably, the indirect dryer is a horizontal drum dryer that is heated by the hot flue gases from a combustion furnace.

Abstract: An automated, non-polluting process and apparatus for mechanically dewatering and heat drying liquid sewage sludge of widely varying solids content to form a pelletizable, dried sludge of predetermined uniform solids content without requiring recycling of previously heat processed sludge. Prior to being dried, the sludge is mixed with flocculation and coagulation promoting chemicals and is dewatered in a belt-type press. Drying takes place within an indirect heat dryer including an enclosed housing for capturing all gases and particles entrained in the gas driven off during the drying process. The gases and particles are advanced by means of a fan first through a cyclone separator for removing dust particles and next through a water jet scrubber prior to being exhausted or burned in order to control odor. The dust removed by the cyclone separator is recombined with the output from the indirect dryer prior to being pelletized.