Comprehensive air emission tests were conducted on two multiple-hearth incinerators equipped with venturi scrubbers, aftercoolers, and zero-hearth afterburners. A pilot wet electrostatic precipitator was also tested for its ability to reduce emissions from existing systems. Particulate matter, metals, organics, and acid gas emissions were measured by rigorous test procedures. Tests of existing systems indicated that the equipment was capable of reducing particulate emissions to less than 0.38 kg/Mg of dry sludge input. More than half of the particulate mass penetrating the existing equipment was less than 0.6-mu-m in diameter. Analysis indicated these submicron particles were enriched with volatile metals. The existing equipment demonstrated cadmium and lead control efficiencies that were significantly higher than those assumed in proposed regulations. Despite low sludge concentrations and high site-specific control efficiencies, arsenic and cadmium emissions will exceed limits proposed in recent regulations. Dispersion factor corrections or reductions in cadmium and arsenic emissions will be needed to satisfy proposed regulations. Emission tests indicated that a wet electrostatic precipitator can greatly enhance the removal of particulate matter, metals, and total hydrocarbons that penetrated the existing systems.
