Pathogens, toxic metals, and toxic organics occur at low concentrations in municipal wastewaters, but many of these materials are concentrated thousands of times in the resulting primary and secondary biological sludges. A review of the Environmental Protection Agency's (EPA's) "safe sludge" designation for use in food production shows that nearly half of all sludges generated cannot be defined as "safe," thus eliminating the cost-effective ultimate disposal alternative of land application. A process that could eliminate the toxic constituents of sludge would be of benefit to many municipalities and industries.Previous research has developed a process that promises to be capable of detoxifying sewage sludge in a cost-effective manner. This project outlines the next phase that is needed to bridge research information with commercial application.Aerobic digestion with unique highly efficient self-aspirating aerators was shown to be capable of autoheating sludges to pasteurization temperatures (50øC+) by Jewell in a full scale facility in 1979. Further development showed that modifications to the process have the potential of removing pathogens, toxic metals, and possibly toxic organics in a cost-effective, simple process.Autoheating slurry temperatures can easily achieve 60øC with most sludges without heat energy additions (higher temperatures would be possible with heat exchangers), thus killing all pathogens. Manipulation of the pH in these hot aerobic slurries showed that greater than 80% of most toxic metals could be rapidly solubilized (in less than 3 hours). Although not tested aeration at these temperatures would be likely to result in volatilization of some toxic organics. Finally, it was shown that the process could also be applied to anaerobically digested sludge. This latter application is important not only because of the large installed digestion capacity, but short term aeration (6 hours) of anaerobically digested sludge results in rapid temperature increases, and significantly increased settleability and dewatering characteristics, thus achieving up to 50% volume reduction. Thus a hypothetical system with hydraulic retention time of less than 24 hours should be capable not only of substantially reducing sludge volumes but also of producing sludge that would meet EPA's "safe" designation for virtually all organic sludges either as an add-on process or as a new installation.This study will examine the impact of the unique self aspirating aerators on the settle ability dewaterability, autoheating, and metal removal characteristics of anaerobically digested sewage sludge in a 28 m3 full scale unit located at the Binghamton, New York, sewage treatment facility (a 190 million l/d capacity plant). Three other sludges representing a wide range of contaminants, will be trials will be used to estimate design requirements and to estimate the feasibility of the process
