Estimating the mass transfer coefficient using the floating soluble probes technique: a laboratory study

ABSTRACT

The floating solid soluble probe is a low-cost technique for estimating the mass transfer coefficient of oxygen in the air-water interface (K_a). This technique is based on the fact that K_a can be correlated with the dissolution rate of a soluble solid (V_S), since both parameters are influenced by the surface turbulence. The aim of this study was to calibrate a new floating solid soluble probe configuration. Surface reaeration experiments and dissolution of the soluble solid probe were performed in two experimental apparatus (jets stirred tank and a circular hydraulic channel), in which different levels of turbulence were produced. The results showed a strong correlation between K_a and V_S, r = 0.953 for experiments performed on the tank and r = 0.895 for experiments performed on the channel. The new floating solid soluble probe configuration provided an increasing K_a.V_S ^-1 ratio as a function of the Reynolds number, indicating that the relationship between these two parameters depends on the surface turbulence. We conclude that the floating solid soluble probe technique has a high potential, despite calibrations in natural water bodies and equipment with a turbulence structure different from those used in this study are still necessary to definitive utility.

Keywords:
K_a; surface reaeration; dissolved oxygen; solid soluble probe