ABSTRACT
The most common hurdle to the beneficial reuse of sludge is the presence of unacceptably high levels of heavy metals. High metals concentrations in sludge that is land applied may limit the site life or reduce the application rate to the point where land application is uneconomical. When metals concentrations exceed the maximum regulatory limitations, land application is prohibited. Digestion and processing significantly reduces the number of coliform bacteria, bacterial pathogens, and parasites in sludge and the amount of volatile and semivolatile toxic organics, but it does not reduce levels of heavy metals. In theory, point source contaminants, or contaminants that are discharged to the sewer system at a single or few locations, are easier to control than non-point source contaminants. In practice, contaminant reduction is a multifaceted problem.
