Evaluation of Bacillus Spore Survival and Surface Morphology Following Chlorine and Ultraviolet Disinfection in Water

The objective of this paper is to evaluate the change in Bacillus subtilis spore survival and dimensions following ultraviolet and chlorine disinfection in water. Disinfection was monitored by using tools such as atomic force microscopy (AFM), particle sizing by the electrozone sensing technique and fluorescence of spores after staining with an optical brightener. Results indicated that there was a change in the adsorbed fluorescence following chlorine; however, the magnitude of this change was only approximately twofold at 90% of spore kill. In addition, changes in spore particle-size distribution following chlorine occur at above 99.9% of spore kill. Even the roughness (RMS), width, and length of spores as measured by AFM change only after about 99% of spore killing with chlorine. Use of optical brighteners, AFM, and sizing are not sensitive enough for detecting the disinfection of chlorine-resistant spores and as expected no changes occurred with ultraviolet treated spores. Even though, these techniques may have the potential for determining oxidative disinfection and for the development of monitors and sensors of chemical disinfection for chlorine-sensitive microorganisms.