Abiotic factors affecting inactivation of pathogens in sludge

Abstract

Pathogen inactivation tests on anaerobically digested and dewatered sludge consisted of long-term incubation/storage of a mixture of sludge solids and lime at various doses in closed containers at several temperature levels. The containers simulated anoxic conditions that would exist in a landfill or a sludge monofill. After rapid initial increase of pH, and due to containment of the sludge, the alkaline conditions prevailed during the remainder of the storage. This led to inactivation of pathogen indicators at doses much below those traditionally recommended for alkaline disinfection and production of biosolids, i.e. properly treated sludge. Fecal coliform and Salmonella bacteria were inactivated to the US EPA's class A levels at quicklime doses as low as 20 g CaO/kg TS or about 6 g CaO/kg of wet solids. The pH 12 lasted for the entire storage time in containers with lime doses at or above 120 g/kg TS, regardless of the incubation temperature. Such high pH allowed elimination of the spores of pathogenic Cl. perfringens bacteria from the solute.