Waste treatment Liquid membranes

Since 1995, the Chemical and Nuclear Engineering Department of the Polytechnic University of Valencia in Spain has been working on the application of membrane technology to the treatment of low and medium level radioactive liquid wastes. In this chapter, we describe two practical cases of radioactive liquid waste treatment using membrane processes the treatment of Cs-contaminated water generated after a radioactive incident in a stainless steel production factory, and the treatment of 1 liquid wastes from nuclear medicine services at hospitals. 

This section describes some case studies carried out by the authors, which are related to radioactive liquid waste treatment using membrane processes a study about the influence of radiation on reverse osmosis membranes, a practical case about concentration of I radioactive liquid wastes by ultrafiltration and reverse osmosis processes, and a practical experience about decontamination of Cs liquid waste by reverse osmosis, including a study of radiological protection during the treatment. 

Amal JM, Sancho M, Campayo JM, Villaescusa JI, and Verdii G. Cs-137 Radioactive Liquid Wastes Treatment using Membrane Techniques. 10th International Congress of the International Radiation Protection Association, Hiroshima, May 14—19, 2000. 

G. Zakrzewska-Trznadel, M. Harasimowicz, A. Miskiewicz, A. Jaworska-Sobczak, Liquid low-level radioactive waste treatment by membrane processes. Mater. Res. Soc. Symp. Proc. 1475, 2012, 623-628. 

The development of liquid-membrane extraction has been mainly in the fields of hydrometallurgy and waste-water treatment. There are also potential advantages for their use in biotechnology, such as extraction from fermentation broths, and biomedical engineering, such as blood oxygenation. 

Hill, C., Dozol, J.-F., Lamare, V., Rouquette, H., Eymard, S., Tournois, B., Vicens, J., Asfari, Z., Bressot, C., Ungaro, R., Casnati, A. Nuclear waste treatment by means of supported liquid membranes containing calixcrown compounds. J. Incl. Phenom. Maerocyclic Chem. (1994), 19 (1—4), 399 -08. 

It has been demonstrated that membrane separation processes can be successfully used in the removal of radioactive substances, with some distinct advantages over conventional processes. Following the development of suitable membrane materials and their long-term verification in conventional water purification, membrane processes have been adopted by the nuclear industry as a viable alternative for the treatment of radioactive liquid wastes [1]. In most applications, membrane processes are used as one or more of the treatment steps in complex waste treatment systems, which combine both conventional and membrane treatment technologies. These combined systems have proved more efficient and effective for similar tasks than conventional methods alone. 

For radioactive effluent treatment, the relevant membrane processes are microfiltration, ulfrafiltration (UF), reverse osmosis, electrodialysis, diffusion, and Donnan dialysis and liquid membrane processes and they can be used either alone or in conjunction with any of the conventional processes. The actual process selected would depend on the physical, physicochemical, and radiochemical nature of the effluents. The basic factors which help in the design of an appropriate system are permeate quality, decontamination, and VRFs, disposal methods available for secondary wastes generated, and the permeate. 

Radioactive waste treatment applications have been reported [3-9] for the laundry wastes from nuclear power plants and mixed laboratory wastes. Another interesting application of reverse osmosis process is in decontamination of boric acid wastes from pressurized heavy water reactors (PHWRs), which allows for the recovery of boric acid, by using the fact that the latter is relatively undissociated and hence wdl pass with water through the membrane while most of the radioactivity is retained [10]. Reverse osmosis was evaluated for treating fuel storage pool water, and for low-level liquid effluents from reprocessing plants. 

Membrane Processes Employed for Liquid Radioactive Waste Treatment.850... 

MEMBRANE PROCESSES EMPLOYED FOR LIQUID RADIOACTIVE WASTE TREATMENT... 

Despite of some technical and process limitations, membrane techniques are very useful methods for the treatment of different types of effluents. They can be applied in nuclear centers processing low- and intermediate-level liquid radioactive wastes or in fuel reprocessing plants. All the methods reported in the chapter have many advantages and can be easily adapted for actual, specific needs. Some of them are good pretreatment methods the other can be used separately as final cleaning steps, or can be integrated with other processes. Membrane methods can supplement or replace techniques of distillation, extraction, adsorption, ion exchange, etc. Evaluation of membrane processes employed for liquid radioactive waste treatment is presented in Table 30.17. 

Chmielewski, A.G., Harasimowicz, M., and Zakrzewska-Trznadel, G., Membrane technologies for liquid radioactive waste treatment, Czech. J. Phys., 49, 979, 1999. 

Membrane technologies have a great potential in the treatment of radioactive liquid wastes, as it has been proved throughout this chapter. In this sense, it is expected a growing use of the membrane processes in the radioactive field, with different possibilities alone, combined between them (microfiltration or ultrafiltration and reverse osmosis) or combined with other conventional processes like evaporation or ion exchange. Furthermore, some special membrane processes, like membrane distillation or liquid membranes, could be applied for the specific treatment of radioactive wastes. 

Membrane bioreactors have finally also been applied to the treatment of gaseous phase wastes with a membrane used as a contactor, e.g., for the removal of organics (e.g., propene, chlorinated solvents, etc.) or inorganics (SO2, NO etc.). A biomass film is mostly grown on or within the membrane, or the bacteria can be homogeneously dispersed in the receiving liquid. 

Treatment of Cyanide-Containing Waste Water from Gold Mine Operation by Liquid Membrane Technology. News release in Kexue Bao (Newspaper of Science), China, October 16, 1987. 

Chaudry, M. A., Bukhari, N., Mazhar, M., Abbasi, W. (2007). Coupled transport of chromium(III) ions across triethanolamine/cyclohexanone based supported liquid membranes for tannery waste treatment. Sep. Purif. Technol., 55, 292-9. 

Wan, Y.H., Wang, X.D. and Zhang, X.J. (1997).Treatment of high concentration phenolic waste water by liquid membrane with N503 a.s mobile carrier. J. Membr. Sci., 135, 263-70. 

Bhavani, R., Neena, T. and John, W. (1994). Emulsion liquid membranes for waste-water treatment Equilibrium models for some typical metal-extractant systems. Environ. Sci. Technol., 28, 1090-8. 

Commercial eind laboratory applications of liquid membrane technology are discussed including gas transport, sensor development, metal ion recovery, waste treatment, biotechnology and biomedical engineering. Immobilized liquid membranes, emulsion or liquid surfactant membranes, and membrane reactors are discussed. Economic data from the literature for liquid membrane processes are presented and compared with existing processes such as solvent extraction and cryogenic distillation of air. 

---