Association and decontamination of Bacillus spores in a simulated drinking water system

• Published in: Water research (Oxford) 2008-12, Vol.42 (20), p.5011-5021
• Main Authors: Morrow, J.B., Almeida, J.L., Fitzgerald, L.A., Cole, K.D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bacillus anthracis; Bacillus anthracis - drug effects; Bacillus anthracis - growth & development; Bacillus anthracis - isolation & purification; Bacillus anthracis - physiology; Bacillus spores; Bacillus thuringiensis; Bacillus thuringiensis - drug effects; Bacillus thuringiensis - growth & development; Bacillus thuringiensis - isolation & purification; Bacillus thuringiensis - physiology; bacterial spores; Biofilm; Bioreactors; Chlorine; Copper; disinfectants; Disinfectants - pharmacology; disinfection; drinking water; Drinking water disinfection; Exact sciences and technology; microbial contamination; Monochloramine; Other industrial wastes. Sewage sludge; plastic pipes; Pollution; poly(vinyl chloride); Polyvinyl Chloride; Potable water; public health; Spores, Bacterial - drug effects; Spores, Bacterial - growth & development; Spores, Bacterial - isolation & purification; Spores, Bacterial - physiology; Wastes; Water Purification - methods; Water Supply - standards; water treatment; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2008.09.012

The objective of this work was to elucidate the disinfectant susceptibility of Bacillus anthracis Sterne (BA) and a commercial preparation of Bacillus thuringiensis (BT) spores associated with a simulated drinking water system. Biofilms composed of indigenous water system bacteria were accumulated on copper and polyvinyl chloride (PVC) pipe material surfaces in a low-flow pipe loop and uniformly mixed tank reactor (CDC biofilm reactor). Application of a distributed shear during spore contact resulted in approximately a 1.0 and 1.6 log 10 increase in the number of spores associated with copper and PVC surfaces, respectively. Decontamination of spores in both free suspension and after association with biofilm-conditioned pipe materials was attempted using free chlorine and monochloramine. Associated spores required 5- to 10-fold higher disinfectant concentrations to observe the same reduction of viable spores as in suspension. High disinfectant concentrations (103 mg/L free chlorine and 49 mg/L monochloramine) yielded less than a 2-log 10 reduction in viable associated spores after 60 min. Spores associated with biofilms on copper surfaces consistently yielded higher Ct values than PVC.