1 research outputs found
Solar Inactivation of Enterococci and <i>Escherichia coli</i> in Natural Waters: Effects of Water Absorbance and Depth
The decay of sewage-sourced <i>Escherichia coli</i> and
enterococci was measured at multiple depths in a freshwater marsh,
a brackish water lagoon, and a marine site, all located in California.
The marine site had very clear water, while the waters from the marsh
and lagoon contained colored dissolved organic matter that not only
blocked light but also produced reactive oxygen species. First order
decay rate constants of both enterococci and <i>E. coli</i> were between 1 and 2 d<sup>–1</sup> under low light conditions
and as high as 6 d<sup>–1</sup> under high light conditions.
First order decay rate constants were well correlated to the daily
average UVB light intensity corrected for light screening incorporating
water absorbance and depth, suggesting endogenous photoinactivation
is a major pathway for bacterial decay. Additional laboratory experiments
demonstrated the presence of colored dissolved organic matter in marsh
water enhanced photoinactivation of a laboratory strain of <i>Enterococcus faecalis</i>, but depressed photoinactivation of
sewage-sourced enterococci and <i>E. coli</i> after correcting
for UVB light screening, suggesting that although the exogenous indirect
photoinactivation mechanism may be active against <i>Ent. faecalis,</i> it is not for the sewage-source organisms. A simple linear regression
model based on UVB light intensity appears to be a useful tool for
predicting inactivation rate constants in natural waters of any depth
and absorbance