Pathogens in sludge: occurrence, inactivation, and potential for regrowth

Abstract

The USEPA has set forth regulations specifying the processes for pathogen control which are acceptable for both restricted and unrestricted use of sewage sludge. For unrestricted use, processes which disinfect sludge - eliminate its ability to cause infection - are required. However, there is still concern about the public health risks of unrestricted sludge use, principally because under favorable conditions, certain patho- gens can regrow in disinfected sludge. A careful examination of pathogen behavior in sludge was undertaken. It revealed that the only bacterial pathogens likely to regrow are associated with gastroenteritis, rather than more serious diseases, and that ingestion of a large number of these baceria would be required to cause illness in healthy individuals. A fungal health hazard is posed by Aspergillus fumigatis. It is already widely distributed in the environment, but is a hazard only to infants, the elderly, and those whose health is compromised. The authors conclude that the unrestricted use of disinfected sludge poses at most a modest health hazard, much less serious than than the use of non-disinfected sludge. Further steps are discussed which can be taken to prevent or control regrowth of those few pathogens which may pose a problem. 91 references, 6more » tables.« less