UDC 628.161:66.081.63
DOI 10.35776/VST.2024.01.02
Pervov A. G., Spitsov D. V., Tet Zo Aung, Medved’ko Viktoriia
Use of the reverse osmosis method for the preparation of concentrated sodium chloride solutions for the production of sodium hypochlorite
Summary
The use of membrane reverse osmosis and nanofiltration plants for the production of drinking water is described. It is noted that using hypochlorite obtained by the electrolysis of concentrated solutions of table salt is an effective method of disinfection in drinking water supply systems. A new area of application of reverse osmosis systems is considered, i. e., the preparation, in addition to clean water, of concentrated solutions of sodium chloride used for the production of sodium hypochlorite to reduce the operating costs of a drinking water treatment plant eliminating the purchase of the chemical, i. e., table salt. A process flow scheme of the proposed technology is presented, that involves cascade processing of the source water using nanofiltration membranes of low selectivity to provide for separating the concentrate into the solutions of monovalent and divalent ions. The experimental procedure is described and experimental dependencies are presented to determine the efficiency of the concentrate separation. Based on the results of the experiments, an economic calculation of the costs of designing an additional system for producing concentrated solutions was performed proving the economic efficiency of the proposed process compared to the use of table salt.
Key words
disinfection , sodium hypochlorite , reverse osmosis , reverse osmosis unit , nanofiltration , concentrate utilization , water treatment , electrolysis method
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UDC 628.16.6
Pervov A. G., Efremov R. V., Spitsov D. V., Andrianov A. P., Gorbunova T. P.
Membrane methods in drinking water supply: membrane selection, water quality prediction, concentrate utilization
Summary
It is shown that the use of membrane reverse osmosis and nanofiltration units for drinking water treatment is complicated by the presence of large amounts of concentrates subject to the discharge into the sewer. To reduce water use for local needs the technology of concentrate treatment at the additional stage with the use of nanofiltration membranes was developed and tested. The flow of the generated concentrate is less than 1–6% of the total water flow rate whereas the second stage filtrate can be blended with either treated or incoming water depending on the hardness or presence of such pollutants as iron, ammonium, fluorine, arsenic etc. Process flow schemes, mass balance and the composition of incoming water, filtrate and concentrate at different treatment stages are presented.
Key words
filtrate , reverse osmosis , nanofiltration , drinking water supply , membrane method , concentrate utilization
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UDC 628.1.2:62-278
Frenkel V. S.
Membrane Technologies: Past, Present and Future (the North America as an Example)
SUMMARY
Basic tendencies in the field of development of membrane processes for water and wastewater treatment in the North America are covered. Main characteristics, basic trends and features of the use of membranes including membrane bioreactors are presented. Characteristics necessary for assessment and selection of the best membrane technologies for each certain project are compared. Membrane treatment has become the fastest growing sector in water treatment, wastewater treatment and water desalination. Four types of membranes are used according to membrane pore size: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). All four principal types of membrane guarantee the removal of the entire spectrum of water pollutants and can be used as a stand-alone technology for a majority of applications. Integrated membrane processes combining different membrane types are becoming a cutting edge approach to meet strict water/wastewater quality regulations because they allow the smallest possible system size, minimize chemical consumption, and provide the most cost-effective solution for the greatest number of applications.
Key words
potable water , wastewater treatment , reverse osmosis , ultrafiltration , desalination , membranes , microfiltration , nanofiltration , membrane bioreactor
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UDC 628.161.2:614.777:546.47/.49
Larionov S. Iu., Panteleev Aleksei, Riabchikov Boris, Shilov Mikhail, Kasatochkin A. S.
Removal of natural radionuclides from underground water sources
Summary
Natural radionuclides are present in underground water sources of some Russian regions in the concentrations exceeding the maximum permissible level for drinking water. Natural water radioactivity is caused by the presence of uranium 238U and thorium 232Th isotope decay products including radium and radon. For the purification of radium containing water lime softening, sorption on special adsorbents (e. g. zeolites), ion exchange softening and active aluminium oxide or active alumina, manganese containing media are used. The given methods of treatment are described in a number of publications that state the possible use of reverse osmosis or nanofiltration, however, lack the information on their application. Membrane technologies in combination with the traditional methods allow designing the flow scheme of radionuclides removal from underground water. During the tests on producing water of the required quality for an open-cycle heat supply system no radionuclides accumulation was observed. For the operation period (1.5 month) of the ultrafiltration plant during the interval between backwash cycles the radiation background straight at the membrane increased insignificantly; whereas, after the backwash it returned to the initial level. Backwash number was more than 100 providing for the statistically valid data. The reverse osmosis plant was operating with ultrafiltration permeate. The total radionuclides in the parent solution was about 1.4 Bq/l, in reverse osmosis filtrate – 0.005 Bq/l, i. e. much lower than the maximum permissible level. In reverse osmosis concentrate this value does not exceed 1 Bq; therefore, it can be discharged into the open hydraulic networks in compliance with the established standards. No activity accumulation on the reverse osmosis membranes was observed.
Key words
aeration , reverse osmosis , ultrafiltration , nanofiltration , membrane technology , water treatment , radionuclides , radioactive wastes
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UDC 628.112.23:628.168.4
Tsabilev O. V., Strelkov A. K., Bykova P. G., Zanina Zh. V., Vasiliev V. V.
Treatment of Artesian Water for Domestic Water Supply
Summary
An example of solving the task of improvement of artesian water quality up to normative values with the help of baromembrane technologies is given. A flow chart of water treatment for household needs of a settlement optimal from the ecological and economical points of view is described. The comparative results of the technological calculation of various schemes of water demineralization and softening including the processes of ion exchange, nanofiltration and reverse osmosis are presented.
Key words
deferrization , reverse osmosis , softening , selectivity , nanofiltration , ion exchange
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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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UDC 628.165:66.081.63
Chigaev I. G.
The use of nanofiltration in brackish water softening
Summary
The results of the experimental studies with real water are presented that showed the perspectiveness of using the purification technology based on polymer nanofiltration membranes in underground brackish water desalination as compared to reverse osmosis. The basic characteristics of nanofiltration membranes were studied. Possible concentrating of influent water by partial concentrate recycling was evaluated; the maximum salt concentrations in recycling water were determined. The studies on evaluating the effect of deposit formation on the basic membrane characteristics did not discover any noticeable permeability reduction; herewith the zones of intensive salt deposit formation on membranes were identified. It was determined that salt concentration in recycling water supplied on the membrane shall not exceed 42 mg-equ/l to obtain permeate with up to 6 mg-equ/l and for permeate with 2 mg-equ/l hardness the salt concentration shall not exceed 18 mg-equ/l. Influent water concentrating provides for the substantial reduction of discharged concentrate.
Key words
reverse osmosis , membranes , nanofiltration , desalination , underground brackish water , deposit formation
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DOI 10.35776/MNP.2020.01.01
UDC 628.16:62-278
Pervov A. G., Golovesov V. A., Spitsov D. V., Rudakova G. Ya.
Ways of reducing the operating costs of membrane units
for the preparation of drinking water from underground water sources
Summary
Experimental investigations have been conducted to determine the main process parameters of membrane units (filtrate yield, the rate of scaling on membrane surface). Basing on the results of the experimental studies the total costs of purification of underground water of various chemical composition were obtained. The studies were conducted on laboratory benches with the use of nanofiltration membranes with various selectivity rates. The consumption of service chemicals and operational costs for the equipment were calculated by the software designed earlier by the authors for determining the process parameters of membrane units. While designing membrane units, nanofiltration membranes with low values of selectivity, power consumption and expenditures for chemicals are preferred. The dependencies of the calcium carbonate scaling rates on membrane types and the multiplicity of volumetric concentration of source water were obtained. A comparison of costs shows that the use of membranes even for cases of water deferrization is more economical than the known traditional technologies.
Key words
calcium carbonate , ground water , concentrate , reverse osmosis , nanofiltration , water softening , scaling on membranes , deposits of slow-soluble salts in water , scaling inhibitors , scaling rate
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DOI 10.35776/VST.2022.12.06
UDC 621.395.623.3
Strelkov A. K., Tsabilev O. V., Gridneva M. A.
Vibromembrane filtration technology: eliminating the negative effect of concentration polarization (international experience)
Summary
Представлена уникальная технология мембранного разделения жидкостей VSEP, которая позволяет минимизировать негативное влияние концентрационной поляризации. Отличие технологии заключается в вибрации поверхности мембран. В результате достигается ряд ключевых преимуществ технологии. Все это существенно раздвигает границы использования мембранных методов и делает возможным применение мембран там, где ранее это было невозможно. Кроме того, процесс разделения различных жидкостей не требует использования антискалянтов, а рабочие значения удельной производительности установок и выхода фильтрата значительно превышают таковые в традиционных системах мембранного разделения. Технология уже находит массовое применение в мировой инженерной практике для самых различных отраслей промышленности.
Key words
membranes , nanofiltration , membrane filtration , VSEP technology , concentration polarization
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