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. 1994 Jun;60(6):2049–2058. doi: 10.1128/aem.60.6.2049-2058.1994

Sunlight Inactivation of Enterococci and Fecal Coliforms in Sewage Effluent Diluted in Seawater

Robert J Davies-Colley 1,*, Robert G Bell 1, Andrea M Donnison 2
PMCID: PMC201600  PMID: 16349290

Abstract

Inactivation (loss of culturability) by sunlight of enterococci and fecal coliforms within sewage effluent diluted in seawater was investigated in field experiments. In most experiments, 500-ml flasks of pure silica were used to confine activated sludge effluent diluted to 2% (vol/vol) in seawater. Inactivation of bacteria in these flasks (diameter, 0.1 m) was faster than in either open chambers (depth, 0.25 m) or patches of dyed effluent (depth of order, 1 m), probably because of the longer light paths in the latter two types of experiment, which caused greater attenuation of sunlight. Inactivation of 90% of enterococci generally required 2.3 times the insolation required for 90% inactivation of fecal coliforms, because of both the presence of larger initial shoulders on survival curves and a lower final inactivation rate. Two parameters are required to model inactivation of enterococci, a shoulder constant as well as a rate coefficient. The depth dependence of inactivation rate for both fecal indicators matched the attenuation profile of UV-A radiation at about 360 nm. Inactivation by UV-B radiation (290 to 320 nm), which penetrates much less into seawater, is of minor importance compared with the UV-A and visible radiation in sunlight, contrary to expectations in consideration of published action spectra for bacterial inactivation.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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