Inactivation ofBacillusspores in decontamination wash down wastewater using chlorine bleach solution

Abstract

Bacillus anthracis spores are highly resistant to disinfection. The effectiveness of sodium hypochlorite (bleach) solution for the inactivation of Bacillus atrophaeus subspecies globigii spores (a surrogate for Bacillus anthracis) in wash down wastewater was evaluated by a series of bench-scale and pilot-scale experiments. The wastewater was generated from a simulated decontamination of interior laboratory surfaces and personal protective equipment. A concentration of approximately 5% (v/v) bleach solution was adequate for a ≥7 log 10 inactivation of Bacillus spores spiked in wastewater after 10 min of contact time at room temperature. This sodium hypochlorite dose is less than the U.S. National Response Team-recommended formulation of 10% (v/v) bleach solution with 10% (v/v) vinegar. For the wash down waters evaluated, the addition of vinegar was not required. Inactivation of Bacillus spores was faster when a detergent was added to the wash down waters tested.

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

“…The target NaOCl concentration in the bleach/wash water solution was 3000 mg NaOCl/L. Muhammad et al (2014) showed that this concentration provided the desired amount of inactivation (6 log) in approximately 30 minutes for the wash waters tested. The NaOCl solution used in this current study was made from Clorox regular bleach that had either 6% NaOCl or 8.25% NaOCl.…”

“…The procedures for preparing and enumerating B. globigii spores were conducted as described in Muhammad et al (2014) and are briefly summarized below.…”

“…The work described in this article expanded upon the studies reported in Muhammad et al (2014). The current study evaluated a larger variety of wash waters at room temperature and at 4 8C.…”

“…The recommended U.S. NRT treatment was derived from inactivation procedures developed for B. anthracis spores on solid surfaces and had not been specifically tested in water matrices. In light of this lack of testing, Muhammad et al (2014) tested the inactivation of Bacillus spores in simulated wash water using different levels of bleach and vinegar. In the study, a surrogate for B. anthracis spores was used: Bacillus atrophaeus subspecies globigii (B. globigii).…”

“…In a water matrix, B. globigii spores have been observed to be more resistant to chlorine than B. anthracis spores (Sivaganesan et al, 2006) and thus served as a conservative surrogate for this study. Muhammad et al (2014) initially showed that the recommended dose (1 part bleach, 1 part vinegar, and 10 parts wash water) yielded ! 5 log 10 (log) or 99.999% inactivation in less than 1 minute.…”