UDC 628.167.069.84
Fedotov R. V., Shchukin S. A., Kniazeva Natal’ia, Onkaev Viktor
Study and engineering and economic comparison of chemical methods of softening the Bolshoi Kinel River water
Summary
Softening water for domestic water supply can be carried out by different methods including the addition of alkaline agents into water. Experimental studies of the use of lime-soda and caustic soda methods for softening the Bolshoi Kinel River water that is the source of drinking water supply for the city of Otradny, Samara Region, have been carried out by the employees of EKOFES SPE LLC in the laboratory and working environment. A diagram of a laboratory setup has been developed consisting of a mixer with aeration and an air separator, a vertical sedimentation tank with laminar modules, and a rapid filter. Experimental studies on the effect of chemical doses on the values of residual water hardness and total dissolved solids have been carried out. It has been established that the caustic soda method provides for efficient water softening, however results in an increase in the total dissolved solids, thus limiting the area of application. The results obtained in the study of the lime-soda method allow to conclude that the technology is advantageous owing to the elimination of extra water salinization and to recommend it for softening the water of the Bolshoi Kinel River. The engineering and economic calculation of the cost of 1 m3 of processed water depending on the softening method is presented.
Key words
drinking water supply , chemical softening , water hardness , lime-soda softening method , caustic soda softening method
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UDC 628.16.087
FESENKO L. N., Skryabin A. Yu., Bessarabov S. Iu., Pchel'nikov I. V., Ignatenko S. I.
Utilization of concentrate from reverse osmosis units in the production of electrolytic sodium hypochlorite
Summary
Owing to high efficiency and minimum chemical consumption reverse osmosis and nanofiltration have been widely used in process flow schemes of drinking water demineralization and softening and water preparation for industrial use (in steam boiler-houses, recycling cooling circuits, heat network make up etc.). However, the methods of membrane separation are accompanied by concentrate generation which is very difficult to process and utilize. The data on utilization of concentrates of membrane separation units with obtaining chloride-sodium raw material for the production of electrolytic low-concentrated sodium hypochlorite is presented. Since the waste stream of reverse osmosis units contains elevated concentrations not only of chloride ions but also of Са2+, Mg2+, НCO3- and SO42- ions it would be reasonable at the first stage to reduce the amount of process concentrate by repeated concentrating as per flowchart «nanofiltration-reverse osmosis». Further on the concentrate of nanofiltration containing mainly Са2+, Mg2+ and SO42- divalent ions is subject to chemical treatment as per flowchart: at the first stage with barium compounds; at the second stage with sodium carbonate and hydroxide. This will allow separating practically insoluble BaSO4 from the solution with its precipitation in a vortex reactor or first-stage lamellar separator; then CaCO3 and Mg(OH)2 low-soluble in alkaline environment are precipitated in the second stage reactor. BaSO4, CaCO3 and Mg(OH)2 insoluble salts removed from the mass balance are dewatered in a filter-press and sold as commodity or raw products. Aqueous solution of sodium chloride is repeatedly concentrated by three-stage reverse osmosis to obtain 2–2.5% aqueous solution of table salt – high-grade raw material for the production of electrolytic sodium hypochlorite with 6–8 g/l chlorine equivalent concentration. Chlorine-containing product can be used for drinking and waste water disinfection, biocidal processing of cooling towers, heat exchanging units for preventing and removing biofouling, washing ultra-and microfiltration membranes, disinfecting water treatment facilities and equipment, pipelines and other components used in the production of drinking and process water.
Key words
sodium hypochlorite , concentrate , reverse osmosis , nanofiltration , desulfatation , chemical softening
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DOI 10.35776/VST.2022.03.02
UDC 628.164
Kasatochkin A. S., Larionov S. Iu., Panteleev Aleksei, Riabchikov Boris, Shapovalov Dmitrii, Kharitonov Nikolai, Shilov Mikhail
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
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DOI 10.35776/VST.2022.09.01
UDC 628.166.094.3(477.75)
Skryabin A. Yu.
Ecological safety of Crimea: advanced technologies
of water management complexes
Summary
The main problems of the Crimean water supply are related to the shortage of drinking water, low technological and sanitary reliability of water treatment systems, the lack of a sufficient number of demineralization, softening and disinfecting water plants in the shoreland and rural areas, and the unsatisfactory state of the water distribution network and treatment facilities. In the circumstances concerned, an urgent task is to provide the population of Crimea with high-quality drinking water when increasing the environmental safety of the operation of engineering and water management complexes, including facilities, plants and installations for the treatment and disinfection of natural and waste water. The aspects and ways of solving the problems of recycling and reusing as a commercial product the concentrate of desalination and water softening plants, as well as electrolysis wastes of sodium hypochlorite production at the water treatment facilities for water disinfection are considered. Environmentally friendly technological solutions for the operation of the plants for chemical softening, reverse osmosis and sodium hypochlorite production from aqueous solutions of common salt are recommended.
Key words
disinfection , sodium hypochlorite , desalination , decarbonization , chemical softening , water scarcity , no-waste technology
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