Purification of water with high permanent hardness and salinity

Summary

Chemical softening methods have been widely used in the practice of water treatment, primarily in the energetics and industry for softening, decarbonization and decoloration of water. In combination with reverse osmosis, they provide for preparing water of the required qualitative composition. In drinking water supply softening methods are used quite rarely due to a number of circumstances, such as the need to use various chemicals that are not typical for public water supply; generation of a large volume of sludge subject to subsequent processing, and, what is most important, resulting in highly alkaline water with pH of more than 10 unacceptable for drinking water. However, in case only but water sources with such a complex composition are available, then chemical methods have to be used. In Mediana-Filter Research and Production Company, JSC studies were carried out to obtain high-quality water from an underground source of uncharacteristic salt composition, with a high content of sulfates and low alkalinity, provided that the purification technology should generate minimum liquid waste. After testing several technology options in pilot plants, a scheme was proposed that met the requirements of the customer. It should be noted that underground water of the southern regions of the country has a partially similar salt composition, so the results of pilot tests can also be applied to obtain drinking water from similar sources.

Key words

reagent treatment , flow chart of treatment , reverse osmosis , desalination , hardness , pilot plant , sulphates , water , dynamic softening system , liming , sodium liming , soda softening , sludge blanket , dynamic softening system water conditioning

Development of a dynamic water softening system – DSS

Summary

Underground water sources with a high concentration of hardness salts are often used for drinking water supply. The known methods of softening result in the formation of a significant amount of liquid and solid waste – saline wastewater or sludge that cannot be subject to utilization. Chemical softening of drinking water in clarifiers is rarely used due to the difficulty of preparing chemicals, maintaining the required and constant water temperature, to the complexity of installations and their maintenance. Since the 1990s, the technology of chemical softening in intensified reactors (vortex and in a blanket) has been widely used in drinking water supply. Such apparatuses have been widely used in Europe and the USA. Currently, Mediana-Filter Research and Production Company, JSC has been working on the development and study of this reactor type. They have a high specific capacity – 50–100 m³/(m²·h) and are much easier to maintain compared to clarifiers. The capacity of such equipment reaches thousands of cubic meters per hour. Their main advantage is the absence of liquid discharges, generation of solid waste, which can be subject to utilization, as well as an almost 100% yield of
clean water.

Key words

potable water , pilot plant , chemical water softening , calcic pellets , fluidized bed , intensified reactor , dynamic softening system , contact media blanket

Comparison of the options of systems for adjusting the salt composition of water from underground sources

Summary

Underground water sources with a high content of hardness salts are often used for drinking water supply. To achieve drinking water quality reducing its hardness is required. Known methods of softening result in the formation of a significant amount of liquid and solid wastes, i. e. mineralized wastewater or sludge that cannot be disposed of. Chemical water softening in clarifiers is used quite rarely owing to the difficulty of preparing chemicals, maintaining the constant required water temperature, and the complexity and maintenance of the equipment. In the 1990s, the technology of chemical softening in intensified reactors (vortex and blanket) was developed that gained widespread use in drinking water supply. Such units are quite frequently used in Europe and USA. At present Mediana-Filter Research and Production Company JSC is taking on the task of designing and testing reactors of this type. They have a high specific output of 50–100 m³/(m²·h), and their maintenance is much easier compared to clarifiers. The capacity of such plants reaches thousands of cubic meters per hour. Their main advantage is the elimination of liquid discharges and generation of solid wastes that can subject to utilization, while the yield of clean water is about 100%.

Key words

potable water , reverse osmosis , suspended layer , pilot plant , chemical softening , water softening , contact media , calcic pellets , fluidized bed , intensified reactor , dynamic softening system , sodium cycle