Inactivation of Bacillus Spores in Wash Waters Using Dilute Chlorine Bleach Solutions at Different Temperatures and pH Levels

Abstract

Inactivation of Bacillus globigii spores in wash water was studied to simulate chlorine inactivation of Bacillus anthracis spores in water generated during biological cleanups. Eight waters were studied, with six containing detergent. Chlorine levels were approximately 3000 mg/L. Results across different waters showed decreasing inactivation with increasing pH. Inactivation did not appear to be influenced by chemical oxygen demand, suspended solids, turbidity, or dissolved solids. Inactivation efficacy was expressed as the time calculated to yield 6 log10 inactivation at 3000 mg NaOCl/L. This time ranged from 5 to 51 minutes at ~21 °C and from 11 to 209 minutes at ~5 °C. For one wash water, inactivation was conducted when there was no pH adjustment, and when the pH was buffered at 7 and 8. Inactivation in these buffered waters was rapid, but inactivation decreased sharply at a pH above ~9.3.

Biosafety during a pandemic: shared resource laboratories rise to the challenge

“…Local regulations and institution guidelines vary considerably and must be considered when developing a protocol for biohazardous waste disposal (54). A number of publications detailing wastewater pathogen inactivation are available and may be used as a guide when developing local protocols (54)(55)(56)(57)(58)(59). It should be noted that the stability of bleach is impacted by a number of factors including, but not limited to, pH, temperature, exposure to light, and dilution (59).…”

Automotive wastes

“…Ground and surface water at biologically contaminated sites may also contain petroleum chemicals from roadway runoff. Gallardo, Schupp, Heckman, Krishnan, and Rice (2018) tested automobile wash waters to determine the contact time necessary to yield 6 log 10 inactivation with 3,000 mg/L NaOCl, using Bacillus globigii spores to simulate Bacillus anthracis. To yield 6 log 10 inactivation, car wash water required 28 and 94 min of contact time at temperatures of 22.4 and 3.5°C, respectively.…”