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The effect of pH on the inactivation of Nitrosomonas europaeaby chloramines was testedfor a range of chloramine concentrations. Cell viability was assessed using the most probablenumber (MPN) technique and a culture-independent bacterial viability test. For pH 7 to 9, N.europaea inactivation followed Chick-Watson kinetics with n= 1 and k ranging from 2.5 x 10-(03)L/(mgCl2.min) at pH 7 to 2.4 x 10-(04) L/(mgCl2.min) at pH 9 in the bacterial viability-based tests.For the MPN-based tests, k was approximately 1,000-fold higher. Although CT99 values fromthe MPN-based experiments agreed with CT99 reported elsewhere for ammonia-oxidizingbacteria (AOB), the lower inactivation rates estimated from the bacterial viability tests weremore consistent with AOB persistence in distribution systems, suggesting that MPN mayoverestimate chloramine biocide effectiveness. Finally, the counteracting effect of pH on N.europaea inactivation and chloramine decay indicates that pH control is likely to have asite-specific effect on nitrification. Includes 36 references, tables, figures.

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Edition: Vol. 94 - No. 10 Published: 10/01/2002 Number of Pages: 11File Size: 1 file , 310 KB