Environ. Sci. Technol. 2006, 40, 1371
2005, Volume 39, Pages 7860-7868 Wim A. M. Hijnen, Anke J. Brouwer-Hanzens, Katrina J. Charles, and Gertjan Medema: Transport of MS2 Phage, Escherichia coli, Clostridium perfringens, Cryptosporidium parvum, and Giardia intestinalis in a Gravel and a Sandy Soil. Due to a typing error in one of the formulas, the collector efficiencies η and consequently the sticking efficiencies R in Table 3 were incorrect. In the new Table 3 the correct values are presented; η increased with a factor of 3-5 and consequently R decreased to the same extent. The published R-values for E. coli, C. perfringens, and C. parvum in the Roosteren columns were above unity. On the basis of this observation it was argued that straining played a significant role in the removal of these microorganisms by the Roosteren soil. The correct R-values cannot be used to illustrate the role of straining, since only for E. coli removal in the column operated at 2.5 m‚d-1 is the R slightly above unity. The sticking efficiency, however, was not the only parameter used to put forward the additional role of straining to explain the difference in removal of microorganisms observed in the gravel soil of Roosteren and the sandy soil of the Castricum infiltration site (Table 3). The lower uniformity and porosity with a higher (in)organic sediment content in the Roosteren soil were used to emphasize that straining contributes more to the removal in Roosteren soil than in the Castricum soil. Due to these different soil characteristics Roosteren soil will have a higher fraction of smaller pore sizes and consequently a lower hydraulic conductivity. This was actually observed in samples from both sites as documented in the published paper. Finally, the low influence of the flow rate on the MER is an observation which is mentioned in the published paper and supports the role of straining in the removal process. Despite the fact that the corrected sticking efficiencies are below unity, we still conclude that straining needs further attention in microbial transport models and simple extrapolation of grain size and particle size to the extent of microbial transport in the underground is inappropriate.
TABLE 3. Microorganisms Elimination Rate (MER; log) of the Soil Columns Spiked with Microorganisms, and the Calculated Collector Efficiency η and Sticking Efficiency r (T&E model; ref 1) Castricum 0.5 m d-1 MS2a E. coli C. perfringens C. parvum G. intestinalis a
Roosteren 0.9 m d-1
0.9 m d-1
2.5 m d-1
MER
η;r
MER
η;r
MER
η;r
MER
η;r
3.3 4.7 g5.0 3.9 6.2
1.035;0.003 0.048;0.085 0.067;0.064 0.084;0.040 0.250;0.021
2.2 4.2 g4.5 3.3 >6.2
0.680;0.003 0.032;0.113 0.042;0.092 0.059;0.048 0.172;0.031
3.4 4.8 g2.4 >6.7 >7.4
0.390;0.019 0.019;0.562 0.032;0.169 0.038;0.402 0.120;0.140
1.8 4.1 g3.0 >7.2 >6.8
0.188;0.021 0.009;1.023 0.013;0.516 0.017;0.959 0.051;0.299
Corrected for elimination caused by inactivation (10 and 5% for Castricum and Roosteren, respectively).
Literature Cited (1) Tufenkji, N.; Elimelech, M. Correlation equation for predicting single-collector efficiency in physicochemical filtration in satured porous media. Environ. Sci. Technol. 2004, 38, 529-536.
ES0580237 10.1021/es0580237 Published on Web 01/11/2006
