Author(s)

R.J. Davies-Colley, R.G. Bell & A. Donnison

Abstract

Depth-dependence of Enterococcus inactivation by solar UV in seawater R.J. Davies-Colley," R.G. Bell/ A. Donnison* o Water Quality Centre, National Institute of Water and Atmospheric Research, PO Box 11-115, Hamilton, New Zealand * Environmental Management Section, Meat Industry Research Institute of New Zealand, PO Box 617, Hamilton, New Zealand ABSTRACT The inactivation of two faecal indicator bacteria, enterococcus and the traditional faecal coliform indicator, were measured in silica flasks exposed to sunlight at different depths in the water column. Enterococci were found to be appreciably more persistent than faecal coliforms (e.g., Tgo of about 70 minutes for enterococci compared with about 23 minutes for faecal coliforms, under midday, midsummer irradiances at the water surface). The slower inactivation of enterococci is largely a result of the pronounced shoulder occurring on inactivation curves, in contrast to the more-nearly exponential inactivation

Keywords