Hollow fiber concentrator for water quality monitoring: role of surfactant based elution fluids

Abstract

Simple and efficient concentrators are indispensable to the development of portable biosensor based detection platforms for the determination of microbial contamination in water. This requires the design of a concentrator which could operate for large liquid volume yet maintain the desired microbial concentration in the resultant concentrate. In the present study, we have utilized a commercially available hollow fiber filter modules to test for the concentration and recovery of Escherichia coli (E. coli) from water with the aid of a combination of surfactants and a chemical dispersant as the elution fluid. The process involves the tangential flow filtration of contaminated water through the hollow fiber filter to reduce the sample volume, followed by an elution step to facilitate the transfer of the concentrated mixture onto a portable hand-held water monitoring device. The effect of using two non-ionic surfactants (Tween-20 and Tween-80) and a chemical dispersant, sodium hexametaphosphate (SHMP), as elution fluids have been discussed in the present work. The lowest recovery efficiencies were associated with the case of concentration without elution. Recovery efficiencies using a mixture of SHMP and surfactants (1 : 1 ratio) were found to be greater than when the surfactants were used individually as the elution fluid. A mixture of Tween 20 and Tween 80 (1 : 1 ratio) was even more efficient with greater than 80% recovery being observed. The best results were obtained using the elution fluid made up of a combination of Tween 20, Tween 80 and SHMP (1 : 2 : 1 ratio) with greater than 90% efficiency of bacteria recovery associated with it. Recovery efficiencies increased by 25% using this combination as elution fluid as compared to the case where no elution fluid was used.