Concentration of Cryptosporidium oocysts from river water by coagulation and foam separation combined with acid dissolution of ferric flocs

Abstract

Cryptosporidium is an extremely virulent microorganism; contamination of water works systems by Cryptosporidium oocysts is a serious issue in public health. However, a great deal of effort is required to detect oocysts in source water for drinking, because the oocysts have to be concentrated from a large volume of water before detection. In this study, the concentration of oocysts in oocyst-polluted artificial river water was examined by coagulation and foam separation. The oocysts concentrated in the foam water were purified using immunomagnetic separation and assessed using epifluorescence microscopy. When ferric coagulation was performed prior to foam separation, oocysts were effectively removed from the river water and concentrated in the foam within 10 min. The removal efficiency was greater than 96% at the optimum iron and casein concentrations of 5 mg-Fe L⁻¹ and 20 mg L⁻¹, respectively. Furthermore, the number of recovered oocysts in the solution obtained by the dissolution of the collected ferric flocs from foam water was the same as that obtained using the Japanese standard procedure for detection of Cryptosporidium in water using membrane filtration. This is a novel method of concentrating Cryptosporidium oocysts for detection in river water using a coagulation and foam separation combined with acid dissolution of ferric flocs; the method is easy to use, rapid, and efficient.

Keywords:

• Concentration method
• Cryptosporidium oocysts
• ferric flocs dissolution
• foam separation

Acknowledgments

The assistance of Prof. Akira Sawaguchi (Faculty of Medicine, University of Miyazaki) in the identification of Cryptosporidium oocysts using microscopy is gratefully acknowledged.