Solar Inactivation of Enterococci and Escherichia coli in Natural Waters: Effects of Water Absorbance and Depth.
The decay of sewage-sourced Escherichia coli 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 E. coli were between 1 and 2 d(-1) under low light conditions and as high as 6 d(-1) 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 Enterococcus faecalis, but depressed photoinactivation of sewage-sourced enterococci and E. coli after correcting for UVB light screening, suggesting that although the exogenous indirect photoinactivation mechanism may be active against Ent. faecalis, 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.
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.|Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt).
Peter A
PA
Maraccini
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.
Mia Catharine M
MC
Mattioli
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.
Lauren M
LM
Sassoubre
Southern California Coastal Water Research Project, 3535 Harbor Blvd Suite 110, Costa Mesa, California 92626, United States.
Yiping
Y
Cao
Southern California Coastal Water Research Project, 3535 Harbor Blvd Suite 110, Costa Mesa, California 92626, United States.
John F
JF
Griffith
Earth Research Institute and Bren School of Environmental Science & Management, University of California , Santa Barbara, California 93106, United States.
Jared S
JS
Ervin
Earth Research Institute and Bren School of Environmental Science & Management, University of California , Santa Barbara, California 93106, United States.
Laurie C
LC
Van De Werfhorst
Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.|Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt).
Alexandria B
AB
Boehm
D016983:Enterococcus; D004926:Escherichia coli; D013472:Sunlight; D014867:Water; D014871:Water Microbiology
D014867:Water