The removal of the protozoan parasite, Cryptosporidium parvum, from wastewaters is becoming of increasing importance in the UK, especially since contamination of raw waters by sewage effluents has been implicated in major waterborne outbreaks of cryptosporidiosis in recent years. Compared to conventional wastewater-treatment processes, constructed wetlands have demonstrated favourable removal rates for Cryptosporidium oocysts. The removal mechanisms, however, remain unknown. Predation by free-living ciliated protozoa, which are commonly found in constructed wetlands, was investigated as a possible mechanism for oocyst removal. In laboratory feeding experiments, ciliates (Euplotes patella, Stylonychia mytilus, Paramecium caudatum and an unidentified wetland ciliate species), were exposed to doses ranging from 10 to 106 oocysts/ml for between 5 and 60 minutes. Ciliate predatory activities were assessed by enumerating fluorescently labelled ingested oocysts using epifluorescence microscopy. Oocysts were found to be ingested by all species investigated. Paramecium demonstrated the highest mean ingestion rates (up to 170 oocysts/hr) followed by Stylonychia (up to 60 oocysts/hour). Euplotes and the wetland ciliate had lower mean grazing rates (4 and 10 oocysts/hr respectively). These results indicate that protozoan predation may be an important factor in the removal of Cryptosporidium oocysts from wastewaters in constructed wetlands.
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Research Article|
December 01 2001
Protozoan predation as a mechanism for the removal of cryptosporidium oocysts from wastewaters in constructed wetlands
R. Stott;
R. Stott
*Department Civil Engineering, University of Portsmouth, Portsmouth, PO1 3QL, UK
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E. May;
E. May
**School of Biological Sciences, University of Portsmouth, PO1 2DY, UK
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E. Matsushita;
E. Matsushita
***Biologie Cellulaire et Physiologie, Université Pierre et Marie Curie, Paris VI, France
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A. Warren
A. Warren
****Dept Zoology, Natural History Museum, London, SW7 5BD, UK
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Water Sci Technol (2001) 44 (11-12): 191–198.
Citation
R. Stott, E. May, E. Matsushita, A. Warren; Protozoan predation as a mechanism for the removal of cryptosporidium oocysts from wastewaters in constructed wetlands. Water Sci Technol 1 December 2001; 44 (11-12): 191–198. doi: https://doi.org/10.2166/wst.2001.0828
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