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Application of helical Couette Á Taylor flow (CTF) for reduction of membrane fouling in the process of radioactive wastes treatment was considered. The experiments were carried out with model solutions of cobalt ions (Co2+). Ultrafiltration process combined with complexation with polyacrylic acid or adsorption on activated carbon seeds was applied. The influence of hydrodynamic conditions in the module on the permeate flux and separation efficiency was tested. It was noticed that the helical flow influenced filtration efficiency: with increase of rotation frequency of the inner cylinder in the module, up to 3-fold enhancement of permeate flux was observed. The estimated thickness of residual polymer layer developed on the membrane surface depended on rotation frequency, too. Slight increase of retention factors was observed when dynamic conditions were applied.

The new construction of the membrane module that promotes turbulence allows reduction of the membrane fouling and slight increase of separation efficiency when UF/complexation hybrid process is applied for cobalt ions removal. By application of CFT in the apparatus, in some cases, 3-fold increase of permeate flux in comparison with the static filtration (rotation frequency W 00) corresponding with cross-flow filtration conditions was obtained. The experiments showed that increase of the frequency above 1900 rpm did not result in significant increase of the permeate flux. The variation of estimated value of residual layer formed by the polymer on the membrane surface showed unambiguous influence of rotation motion. High rotation frequency caused the reduction of polymer layer thickness on the membrane surface. The stabilisation of the layer was attained after 30 Á 60 min of operation of the apparatus, while at lower frequencies the layer thickness stabilized after 8 h. The retention factors for Co2+ slightly increased in dynamic filtration in comparison with static conditions. It is expected that the apparatus can be used as a filtration stage after formation of precipitate or metal complexes, as well as a membrane contactor in the process of solvent extraction applied for radioactive waste processing [23]. The implementation of the apparatus in a large scale in nuclear industry requires involvement of battery of such modules. The advantages of helical apparatus with porous tubular membrane are expected in: / . . .