Microbiological Safety Evaluation of a Solid and Liquid Pathological Incinerator

Abstract

A semiportable oil or gas-fired incinerator was designed, fabricated and installed for use at a primate research laboratory. The incinerator was challenged with Bacillus subtilis var. niger spores to determine minimum operating temperatures to prevent the release of spores to the atmosphere when contained in either solid or liquid refuse. The theoretical spore challenge concentration when mixed with the incinerator combustion air for the solid refuse was 3 x 10^7 spores/ft^3 (8.4 x 10^5 spores/m^3), and 7.2 x 10^2 spores/ ft3 (20 spores/m^3) for the liquid refuse. To prevent the release of viable microorganisms to atmosphere the maintained sterilization temperatures for this incinerator were determined to be 760 °C (1,400°F) in the primary chamber and 871 °C (1,600 °F) in the secondary chamber.

Decontamination technologies for release from bioprocessing facilities. Part V. decontamination of sludge

“…The EEC recommends 500 krads for disinfection of liquid sludge and 1000 krads (1 Mrad) for disinfection of dry sludge. 2 Similar standards may be applicable to treatment of rDNA sludge. Downloaded by [Monash University Library] at 01:49 02 November 2014…”

Emission of Airborne Bacteria from a Hospital Incinerator

“…4 Surviving spores in the stack gas were collected on a glass fiber filter with a 99.995 percent filtration efficiency for particles of 0.3 micron diameter. After sampling, the filters were placed in blender bowls with a known quantity of nutrient broth.…”

“…It was noted that although temperatures (location unspecified) of incinerators in continuous operation average 1200 to 1700°F, any one or a combination of the following factors could interfere with the necessary time and or temperature exposure for the sterilization of microorganisms: temperature gradients as a result of intermittent use, linear velocities that exceed incinerator design, internal conveyors, automatic vibrating grates, charging beyond incinerator capacity, moisture content of refuse, height of stack and type of refractory lining. 4 In another study, two large volume (mass per unit time not given) incinerators were challenged with aerosols of Bacillus subtilis spores and vegetative cells of Serretia marcescens. 6 Stack gas samples were collected by filtration as described previously.…”

“…4 In another study, two large volume (mass per unit time not given) incinerators were challenged with aerosols of Bacillus subtilis spores and vegetative cells of Serretia marcescens. 6 Stack gas samples were collected by filtration as described previously. Sterilization of dry Serretia marcescens cells was achieved in both incinerators at 525°F (firebox temperature) with a retention time of 8.6 to 19.2 seconds (based on incinerator volume and stack gas flowrates).…”

“…5 The temperature required to sterilize the emissions from this incinerator were 1400°F in the primary chamber, 1600°F in the secondary chamber, and 1050°F at the top of the stack. Based on incinerator dimensions and gas flowrate, the retention time was 12.5 seconds at 1050°F.…”