FIG. 7.

Enterobacterial thermal tolerance after secondary clarification. The number of surviving cells was normalized to the number of viable cells in an untreated but otherwise identical sample. The values are the averages for three duplicate samples, and the error bars indicate the standard errors. The inset shows the percentage of survival for 2 min after the initial exposure. ○, submerged aeration basin secondary clarifier samples; •, trickling filter secondary clarifier samples; ▾, surface aeration secondary clarifier samples.