Heavy water process evaluation

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. 

The unit operations in the miniplant employ proven emulsion-treatment principles free-water knockout, dual-polarity electrostatic treatment (DPET), heavy-oil evaporation (HOE) dehydration, and induced gas flotation (IGF). The overall process configuration provides maximum flexibility and allows for performance evaluation of units on either an individual basis or in various combinations. 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

We were anxious to evaluate the use of supercritical carbon dioxide (scCOj) to remediate an urban soil. A two-stage approach was prompted by our efiforts to make the process continuous. SCCO2 extraction of particulate media is inherently a batch process. Pressure within the extractor is maintained with a capillary restrictor (in our case a 50 pm diameter silica tube) that is prone to fouling. The non-polar organic Section of an aqueous (surfactant) extract can be removed continuously (either on site or off site) with scCOj in a counter current liquid-liquid like process. The heavy metal contaminants remain with the water fraction for subsequent treatment. The organics fraction is the subject of this short review on SCCO2 processing. 

Abstract It is necessary for environmental evaluation of surface finishing processes. From the viewpoint of current environmental protection acts and laws in various countries (which seem to be getting stricter) surface finishing industries are facing serious challenges. These industries tend to release heavy metals and other pollutants into our air, water, and soil. Therefore, to meet the demands of the environmental protection laws, they will need to modify current processes and propose some new ones to replace their traditional methods. In order for these new processes to be adequate and effective, appropriate environmental evaluations are needed to test them. This chapter describes several ways to evaluate and treat harmful contaminants in air and water (especially those from the surface finishing industry). 

Mahmoud, A. Hoadley, A.F. (2012) An evaluation of a hybrid ion exchange electrodialysis process in the recovery of heavy metals from simulated dilute industrial wastewater. Water Research, 46, 3364-3376. 

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