Elmore-Meegan Effect of agitation, turbidity, aluminium foil reflectors and container volume on the inactivation efficiency of batch-process solar disinfectors

Effect of agitation, turbidity, aluminium foil reflectors and container volume on the inactivation efficiency of batch-process solar disinfectors
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S. C. Kehoe1, T. M. Joyce2, P. Ibrahim3, J. B. Gillespie4, R. A. Shahar1 and K. G. McGuiganCorresponding Author Contact Information, E-mail The Corresponding Author, 1

1 Department of Physics, Royal College of Surgeons in Ireland, 123 St. Stephens Green, Dublin 2, Ireland

2 Tropical Medicine, Royal College of Surgeons in Ireland, 123 St. Stephens Green, Dublin 2, Ireland

3 Department of Pharmacy, University of Science, Penang, Malaysia

4 Department of Industrial Microbiology, National University of Ireland, Dublin 4, Ireland
Received 4 October 1999;
accepted 28 June 2000.
Available online 22 December 2000.

Abstract

We report the results of experiments designed to improve the efficacy of the solar disinfection of drinking water, inactivation process. The effects of periodic agitation, covering the rear surface of the container with aluminium foil, container volume and turbidity on the solar inactivation kinetics of Escherichia coli (starting POPULATION=106 CFU ml−1) were investigated. It was shown that agitation promoted the release of dissolved oxygen from water with subsequent decrease in the inactivation rates of E. coli. In contrast, covering the rear surface of the solar disinfection container with aluminium foil improved the inactivation efficiency of the system. The mean decay constant for bacterial populations in foil-backed bottles was found to be a factor of 1.85 (std. dev.=0.43) higher than that of non-foil-backed bottles. Inactivation rates decrease as turbidity increases. However, total inactivation was achievable in 300 NTU samples within 8 h exposure to strong sunshine. Inactivation kinetics was not dependent on the volume of the water container for volumes in the range 500–1500 ml.

Author Keywords: solar disinfection, dissolved oxygen, agitation, water
Nomenclature

CFU
colony forming unit

HPLC
high-performance liquid chromatography

NTU
nephelometric turbidity unit

Article Outline

• Nomenclature

• Introduction

• Materials and methods
• Bacterial preparation and enumeration
• Optical irradiation measurements
• Laboratory simulations

• Results
• Agitation
• Foil-backing
• Turbidity
• Volume

• Discussion

• Acknowledgements

• References