Use of Carboxylated Microspheres to Assess Transport Potential of Cryptosporidium parvum Oocysts at the Russian River Water Supply Facility, Sonoma County, California

Abstract

Carboxylated microspheres were employed as surrogates to assess the transport potential of Cryptosporidium parvumoocysts during forced- and natural-gradient tests conducted in July and October 2004. The tests involved poorly-sorted, near-surface sediments where groundwater is pumped from an alluvial aquifer underlying the Russian River, Sonoma County, CA. In an off channel infiltration basin and within the river, a mixture (2-, 3-, and 5- μm diameters) of fluorescently-labeled carboxylated microspheres and bromide tracers were used in two injection and recovery tests to assess sediment removal efficiency for the microspheres. Bottom sediments varied considerably in their filtration efficiency for Cryptosporidium.

Keywords:

• bank filtration
• microbiology
• Cryptosporidium parvum
• water quality

Acknowledgments

The authors would like to acknowledge support provided by the Sonoma County Water Agency (SCWA), reviews and comments by Rula Abudalo, Blaine McCleskey, and Steven Harris. Thanks to Rick Taylor for construction of the in situ column and to Joseph Ryan at the University of Colorado for use of equipment used to generate electrokinetic data for the microspheres and oocysts. Any use of trade, firm, or product names is for descriptive purpose only and does not imply endorsement by the U.S. Government.

Notes

*Not determined.

⁺Estimated from water chemistry data.

⁺⁺Estimated from specific conductance equation: Ionic Strength = 0.000025*0.59*specific conductance (Hem 1992).

*Determined by epifluorescent microscopy with computer coupled image analysis ratio of longest axis to shortest axis.

+Percoll gradient Method (Harvey et al. 1997).

**Significant Student's t-test differences between Cryptosporidium parvum and FMS measured zeta potentials ranged from p values of 0.002–0.02.