Site 6, a multiple hearth furnace was tested under two operating conditions, normal combustion was compared with improved combustion conditions as indicated by reduced CO and THC emissions. The effect of lime conditioning on the conversion of total chromium in the sludge to hexavalent chromium emissions was also a primary concern at Site 6. Secondary objectives included comparing the results for chromium and nickel subspecies determined by different analytical procedures, gathering data on other metals and inorganic/organic gases in incinerator emissions, and assessing pollutant removal efficiencies by measuring emissions at both the inlet and outlet to the control system. The Site 6 plant treats 30 million gallons a day of municipal and industrial wastewater. The blended primary/secondary sludge is dewatered to approximately 28% solids using recessed plate cloth filters. The metal mass emissions rate for the outlet runs averaged: As - not detected (< 508 mg/hr), Be - not detected (< 2.2 mg/hr), Cd - 1,450 mg/hr, Cr - 83.3 mg/hr, Pb - 21,100 mg/hr, and Ni - 73.9 mg/hr. The particulate mass emission rates averaged 42 kg/hr and 0.7 kg/hr, respectively for the inlet andoutlet. A positive correlation between the CO/CO2 ratios (an indication of combustion conditions) and the hexavalent to total chromium ratio was demonstrated for the outlet location. At low CO levels (good combustion) the ratio of hexavalent chromium to trivalent chromium was highest, with approximately 10% of the total chromium in the form of hexavalent chromium. It was anticipated that the nickel subsulfide emissions from multiple hearth incinerators would constitute less than 1% of the total nickel emissions. A wet chemical analysis indicated that within the detection limit (< 10%), no nickel subsulfide was present.

"EPA/600/R-92/003c." Microfiche.