Transport and Retention of Cryptosporidium Parvum Oocysts in Sandy Soils

Abstract

A series of miscible-displacement experiments was conducted to examine the retention and transport behavior of oocysts in natural porous media. Three soils and a model sand were used that differed in physical and geochemical properties. Transport behavior was examined under various treatment conditions to help evaluate retention mechanisms. Significant retention of oocysts was observed for all media despite the fact that conditions were unfavorable for physicochemical interactions with respect to DLVO theory. The magnitude of retention was not influenced significantly by alterations in solution chemistry (reduction in ionic strength) or soil surface properties (removal of soil organic matter and metal oxides). On the basis of the observed results, it appears that retention by secondary energy minima or geochemical microdomains was minimal for these systems. The porous media used for the experiments exhibited large magnitudes of surface roughness, and it is suggested that this surface roughness contributed significantly to oocyst retention.

Effect of low‐concentration rhamnolipid biosurfactant on Pseudomonas aeruginosa transport in natural porous media

“…It also possesses high particle angularity and surface roughness as demonstrated by SEM images (supporting information Figure S2B). Such features have been observed to result in enhanced retention through significantly higher straining potential [ Bradford et al ., ; Díaz et al ., ; Ding et al ., ; Santamaría et al ., ; Tufenkji et al ., ]. In addition, the surface roughness may also increase the collision efficiency and decrease electrostatic repulsion energy barriers between cells and porous media, and thus enhance cell deposition [ Hoek et al ., ; Santamaría et al ., ; Shellenberger and Logan , ].…”

“…In addition, the soil has much rougher surfaces (supporting information Figure S2C), and significantly higher specific surface area and organic matter content (Table ) than the sand. Such properties may result in elevated adsorption capacity [ Dai and Hozalski , ; Hoek et al ., ; Parent and Velegol , ; Shellenberger and Logan , ] and enhanced straining potential for bacterial cells [ Bradford and Bettahar , ; Bradford et al ., ; Díaz et al ., ; Ding et al ., ; Santamaría et al ., ; Tufenkji et al ., ], which are responsible for the nearly complete retention of cells in the soil. Despite the great retention potential of the soil, breakthrough of the cells is still observed in the presence of rhamnolipid at a concentration of 40 mg/L (Figure ), with a reduction of retention rate from >99% to 97% and an increase of recovery from ∼1% to 5% (Table ).…”

Pore‐Scale Modeling of Fluid‐Fluid Interfacial Area in Variably Saturated Porous Media Containing Microscale Surface Roughness

“…However, researchers have raised concerns that this approach does not adequately represent the fractal geometry of rough surfaces (e.g., Ghanbarian et al, 2016), in which the actual surface structures may have a fractal growth that greatly exceeds the scale of traditional roughness. An alternative approach to define the effective roughness of a surface has been suggested as a "surface roughness factor," which defines the magnitude of "actual or effective" surface area vs. the geometric-base smooth surface area in one unit surface (e.g., Kamusewitz & Possart, 2003;Santamaría et al, 2012;Wenzel, 1936;Zheng et al, 2015). By definition, the geometric-base surface area is a low-resolution characteristic and is typically treated as smooth, whereas the actual surface area incorporates the effects of surface roughness across a range of higher-resolution scales.…”

Fate and transport of Cryptosporidium parvum oocysts in repacked soil columns: Influence of soil properties and surfactant

“…Although their resistance to many environmental stressors can ensure their potentially infectious viability for months (Fayer, 2004; Fayer et al., 1997; Jenkins et al., 2002; Kato et al., 2004; King & Monis, 2007; Robertson et al., 1992), dessication, heat, and ultraviolet (UV) light have been reported to decrease the infectivity of C. parvum oocysts (Brookes et al., 2004; Jenkins et al., 2002; Li et al., 2005; Olson et al., 1999; Robertson et al., 1992). The release of Cryptosporidium in the environment through direct excretion and application of manure or wastewater to farm fields is a potential source of contamination of the soil‐subsurface environment as well as surface water and groundwater resources (Darnault et al., 2017; Harter et al., 2000; Mawdsley, Brooks, & Merry, 1996; Mawdsley, Brooks, Merry, & Pain, 1996; Santamaria et al., 2012; Zopp et al., 2016). Once released at the soil surface, C. parvum oocysts can be transferred by runoff to surface water or by infiltration to groundwater.…”