Potential Use of Ultrafiltration for Groundwater Remediation and Aqueous Speciation of 60Co and 137Cs from A Contaminated Area

Abstract

The potential for colloid-facilitated migration in contaminated sites is well known, and remediation techniques such as ultrafiltration are often considered for contaminant removal. Although this approach could be successful, the stability of the contaminant species in groundwater and the removal efficiency need to be investigated to ensure proper decontamination of moving aquifers. In our study, we have sampled contaminated groundwater near a former radioactive liquid disposal area at Chalk River, Ontario, Canada. Samples were taken in 2002 and 2004 to determine the behaviour of radiocontaminants by size fractionation using ultrafiltration, with emphasis on 60 Co and 137 Cs. The contaminant concentrations varied significantly for both contaminants in the two samples (34.5 and 25.5 Bq/l for 60 Co, 25.5 and 97.2 Bq/l for 137 Cs). On the other hand, the size fractionation (5,000 Da a nominal cut-off) remained consistent between the 2002 and 2004 samples, as most of the 60 Co (72%-83%) remained in the filtrate, while almost all of the 137 Cs (>98%) was retained along with the colloidal-sized material. Release of 60 Co and 137 Cs from the colloidal material yielded desorption coefficients (K D-des ) of 7.8 × 10 5 and 1.7 × 10 8 ml/g for 60 Co and 137 Cs, respectively.

Fluorescence Analysis of Natural Organic Matter Fractionated by Ultrafiltration: Contrasting Between Urban-Impacted Water, and Radio-Contaminated Water from a Near-Pristine Site

“…In comparison, the signal decrease for C1 and C2 was much smaller. Knowing that the SPE preferentially removes hydrophobic NOM (Caron and Mankarios 2004;Caron et al 2007), in our context, these observations mean that the NOM containing the protein-like components C3 have a higher hydrophobic character than the NOM containing either the C1 or C2 components. The changes in C1 and C2 intensities can also indicate differences in the hydrophobic character of the allochtonous NOM, and this could be useful in differentiating between the natural and wasteimpacted NOM.…”

“…The samples at the locations downstream from the LDA at Chalk River contain low levels of radioactive contaminants in the groundwaters (Caron and Mankarios 2004;Caron et al 2007). The LDA has been out of commission for well over 10 years, and the percolating water from rain or snowfall is expected to have "flushed out" the NOM that could have been disposed of in the coarse aggregate soil filling the pit.…”

“…This correction is needed to compare and relate the TOC among the isolated fractions (also see Caron and Mankarios 2004;Caron et al 2007). For example, ultrafiltration using a 5-kDa pore size cartridge will concentrate the coarse material larger than 5 kDa, plus some unfiltered fine material (retentate fraction).…”

“…It is used in ultrafiltration to determine the approximate size of macromolecules for which a rigorous molecular mass is inappropriate. Caron et al 2007;Schafer et al 2002;Ludwig et al 1997;Mounier et al 1999), and also helps define the range of colloidal-sized material. The technique, however, suffers from artifacts such as membrane charges and influences of ionic content (Schafer et al 2002).…”

“…The technique, however, suffers from artifacts such as membrane charges and influences of ionic content (Schafer et al 2002). Isolation of the colloidal matter is not complete and correction needs to be applied to represent the true colloidal content (Caron and Mankarios 2004;Caron et al 2007;this work).…”