Effect of Some Coal Gasification and Tar Sand Process Waters on the Viability of Indicator Bacteria of Fecal Contamination

Abstract

AbstractThis research was undertaken to determine if a spill of either coal gasification or tar sand process waters could have detrimental effects on the numbers of indicator bacteria in receiving waters. The objectives were (i) to determine the effect of mixing process waters with “natural” waters on the numbers of fecal coliforms and fecal streptococci after storage of these mixtures at 4 and 20°C, (ii) to determine if the growth phase at the time of exposure was important to the survival of Escherichia coli, and (iii) to determine the importance of pH in the toxicity of a process water. Addition of 10% (vol/vol) of one coal gasification water to river water resulted in approximately 90% reduction in numbers of fecal coliforms within 5 h of storage at 4°C, whereas there was a 65% reduction during this time when storage was at 20°C. An additional coal gasification water and two tar sand process waters were not toxic to fecal coliforms. Survival of fecal streptococci was not adversely affected in any of the waters. Stationary phase cells of E. coli were killed within 5 h of exposure to a 10% concentration of Hanna IV B‐1 coal gasification water, whereas lag and exponential phase cells were unaffected during this exposure time. Further, after 24 h of exposure, 40% of the lag phase cells were viable, while live cells from the other two phases of growth were reduced by 99.9%. There was a 12% reduction in viable cells of E. coli after 120 h of exposure to a 10% concentration of Hanna IV B‐1 process water adjusted to pH 7.0. In contrast, during this same time period there was a 5 log reduction in viable cells that were exposed to the process water (pH 8.6), which had not been neutralized.