[en] The acidic solid/liquid tailings from the mill are neutralized with lime and transferred to the tailings pond. The overflow waters released from the pond at the point of discharge contain manganese and radium in quantities that exceed drinking water tolerance. This paper describes the results of studies carried out on the concentration/removal of the pollutants from mill effluents, particularly from the barren solutions and from the tailings pond overflow waters. Factors influencing solution conditions and the pollutants in the pond are discussed. Insolubilization/stabilization of Mn₂⁺ by oxidation to higher oxides and radium by coprecipitation have also been investigated. (author)

[en] The effluent treatment plant at Trombay has been in successful operation for about a decade. However, based on operational experience gained so far, a programme was initiated to further improve performance and operational ease. An account of the process plant modifications done as well as the new processing techniques introduced is given. Treatment of effluents resulting from decontamination operations, removal of I¹³¹, treatment of uranium mill effluents and other radioactive liquid effluents from processing of uranium concentrates, etc. are discussed in detail. (K.B.)

[en] Short communication

[en] Centralised Waste Management Facility collects, treats and disposes within permissible levels of low and intermediate level liquid effluent generated at Kalpakkam. Solid wastes are collected, volume reduced if possible, and disposed in engineered disposal facilities. It has provided uninterrupted service to all the operating plants at Kalpakkam, ensuring that the requirements on radioactive waste management are adequately met. 5 tabs

[en] The paper describes the operational innovations in the effluent treatment plant at Trombay, which has been in successful operation for about nine years. The effluent treatment plant, which is a combined facility for providing chemical and ion-exchange treatments for liquid effluents, has undergone a few modifications in the recent years. They have been carried out with a view to improving the plant performance and reducing some operational problems experienced earlier. The innovations implemented include, among others, the commissioning of a settling plant, installation of an efficient in-line mixing system and design and installation of a sludge transfer system for handling the transfer of highly active sludge concentrates from the settling plant. It has been observed from subsequent operations of the modified system that the quantity of sludge obtained had been consistently in the order of 0.6% of the volume of the effluents treated as against 1.9% earlier. Because of the much smaller volume of sludge obtained, it has been decided to fix the sludge directly in a suitable matrix after reducing the volume further by solar evaporation at the final storage site. Modifications being carried out at the radioactive storage site for the fixation of the above sludge and various other types of waste are also described. This paper also covers the new R and D activities being pursued for establishing technically and economically more viable chemical processes in treating such wastes. A process was developed for the removal of radioiodine from liquid effluents. It involves coprecipitation of iodine on bismuth hydroxide thus avoiding the use of costly silver salts. In addition, a method involving pretreatment with permanganate followed by precipitation of hydrous manganese dioxide was developed for the elimination of interfering organic matters and scavenging of important radionuclides. (author)

[en] Short communication

[en] This paper covers comparative merits of evaporation, comparison of the evaporators tested for volume reduction of radioactive effluent and the design characteristics of the plant

[en] Short communication

[en] Backfill system has become an important component in the multi barrier concept of radioactive waste disposal system. The present study has been undertaken to suggest a suitable backfill system for shallow ground disposal facility at Kalpakkam. The approach has been to determine coefficient of permeability (k) and cation exchange capacity (CEC) for various proportions of soil, clay and vermiculite and to arrive at suitable backfill compositions. An optimum proportion of 80:10:10 for soil, clay and vermiculite has been recommended as a backfill in the construction of reinforced concrete (RC) trenches and tile-holes at Kalpakkam. (author). 7 refs., 2 figs

[en] Overflow waters from the tailings pond in which liquid effluents in the form of barren liquors from uranium mill are discharged may contain 10 pci/litre of radium activity as against the maximum permissible discharge limit of 3 pci/litre and 10 mg/litre of soluble manganese as against the allowable limit of 0.3 mg/litre. These contaminants must be removed and/or made insoluble to ensure environmental safety. Studies were, therefore, carried out to develop methods for: (1) decontamination of both barren liquors and overflow waters and (2) their insolubilisation prior to their release in the pond. Based on the results, a scheme of treatment is formulated. Radium activity in the barren liquor is insolubilised by addition of 25 mg Ba²⁺/litre and precipitation. The liquor is then neutralised with lime. The sludges on liquid-solid separation are subjected to air digestion to stabilise manganese(II) to highly insoluble manganese(IV) oxide. Supernatant and the digested sludges are discharged to the tailings pond. Overflow waters from the pond are treated with 5 to 10 mgs/litre of permanganate to remove manganese and radium. The precipitates resulting in the process may be disposed as solid radioactive wastes and decontaminated water may be released to the environment or if it meets the mill specification, may be reused as process water thus ruling out even the slightest possibility of environmental pollution. The overall cost of chemicals required for the treatment mentioned above works out to be Rs. 0.30 per cubic metre of effluent. (M.G.B.)