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UDC 628.165:62-278:621.311.21

Tsabilev O. V., Strelkov A. K.

Influence of Water Acidation Degree on Quality of Permeate of a Reverse Osmosis Plant

Summary

The results of industrial tests of the plant of reverse osmosis water desalination installed in the chemical water treatment shop of the Samara hydropower station are presented. Influent water is subjected to pre-treatment in clarifiers with liming, filtering on mechanical filters and two-stage Na-cation exchange. The influence of acid doses in the course of influent water acidification and the value of permeate output on its quality is studied. The evaluation of convergence of calculated data performed with the help of specialized software with the actually received values of permeate quality is made. Оbserved dependences allow us to make adjustments of the permeate quality obtained by the calculation method.

Key words

reverse osmosis , selectivity , desalination , membrane technology

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UDC 628.162:62-278

Andrianov A. P., Pervov A. G., Efremov R. V., Spitsov D. V.

Selection of efficient inhibitors for process flow schemes of the Black Sea water desalination

Summary

Sea water desalination by reverse osmosis has been widely used in drinking and domestic water supply. However, one of the major problems that complicate the operation of desalination facilities is the deposition of low solubility salts in membrane apparatus. In order to control the formation of crystal sediments on membranes different methods are used. Inhibitor dosing to raw water is the most efficient method. A variety of efficient inhibiting agents has been developed. Lately one of the main directions of studies in this field has been new types of phosphorus free and easily biodegradable inhibitors. Tests of six new phosphorus free inhibitors were carried out; the comparison with traditionally used Aminat-K inhibitor is given. The experimental dependencies that allow determining the rate of calcium carbonate scale formation in membrane apparatus are presented. Basing on the obtained results the optimal operational expenditures for sea water desalination were calculated. The study was aiming mainly at comparing the efficiency of newly developed and traditional inhibitors in the process of their use in sea water desalination schemes (by the example of the Black Sea water simulant). The conclusion of the efficiency of the inhibitors used is made on the basis of the minimum operational expenditures for desalination.

Key words

water treatment , reverse osmosis , inhibitor , desalination , membrane unit , sea water , low solubility salt deposit

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UDC 628.316:66.081.63

Pervov A. G., Matveyev N. A.

The use of membranes for surface runoff and recycling car wash water treatment

Summary

The results of investigating the technology of surface runoff and recycling car wash water treatment with the use of reverse osmosis systems equipped with specially designed membrane units with «open» channel that provide for processing water with high concentration of suspended matter are presented. For processing raw wastewater in the membrane unit two concentrating stages are used: at the first stage – reverse osmosis membranes that ensure high quality treatment, and at the second stage – nanofiltration membranes that ensure concentrating solutions with high salt content with the minimum power consumption. The specific feature of the technology is in the utilization of the reverse osmosis concentrate that is removed from the system together with wet sludge. The results of the laboratory studies of storm water membrane treatment with the use of special roll elements with «open» channel and new BLF membranes are presented. It is stated that increasing permeate output to 0.9 results in 2.5–3-fold decrease of the equipment capacity. Car wash water undergoes the same treatment. The pilot tests show that increasing salt concentration in recycling water higher than 17 000 mg/l is impractical. The relationships of the increase of pollutant concentration in permeate and membrane capacity depending on the increase of the salt content in water under treatment and the ratio of volume concentrating in a reverse osmosis unit are presented. The parameters of membrane units operating with wastewater of this type with efficient removal of oil products, detergents and other pollutants are determined. Possible utilization of concentrate is shown.

Key words

suspended substances , filtrate , oil products , concentrate , reverse osmosis , surface runoff

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

DOI 10.35776/MNP.2019.09.02
UDC 628.16:62-278

Pervov A. G., Andrianov A. P.

The mechanisms of action of inhibitors in the process of calcium carbonate precipitate formation in reverse osmosis apparatus

Summary

Knowledge of the mechanism of precipitation of slightly-soluble salts on reverse osmosis membranes is extremely important while choosing measures to prevent it and reduce the consumption of concentrate. The conducted studies provided for enunciating a fresh approach to the mechanism of crystalline deposit formation and the role of inhibitors in preventing this process. The development of the experimental technique is based on the idea that the first crystallization phase — crystal nucleation is homogeneous, that is, occurs in stagnant zones in the concentrate volume at high oversaturation with calcium carbonate. Upon the formation the crystals are removed from the stagnant zones and settled on the membrane surface like other suspended particles present in the treated water. The results of studying the adsorption of polymer inhibitor molecules on the crystal surface during nucleation and crystalline growth on the membrane are presented. The experimentally obtained dependences of the rate of adsorption of inhibitors on the dose of inhibitors, the rate of formation of calcium carbonate, the rate of nucleation, and on the total surface of the germinal crystals are given. The study of micrographs of crystals showed the dependence of the size and number of crystals on the oversaturation value in the stagnant zone during nucleation as well as on the effectiveness of the inhibitor. A method is presented that allows determining the concentration of dissolved salts in the stagnant zones of the membrane apparatus and the oversaturation values corresponding to the onset of the crystallization process eliminating the addition and use of various inhibitors.

Key words

calcium carbonate , reverse osmosis , inhibitor , mechanism of precipitation on membranes , stagnant zones , nucleation rate , crystal growth rate , adsorption of inhibitor

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UDC 168.165

Tsabilev O. V., Strelkov A. K.

Optimization of the scheme of preparing demineralized water at the existing machine building enterprise

Summary

Machine building industry needs demineralized water for moisturizers, washing and other processes. To prepare demineralized water the method of reverse osmosis is used. The advantages of this method of water demineralization are as follows: low chemical consumption, compact size of the plants and possible flexibility of the process automation. Considering the scale of reverse osmosis use and diversity of the solvable problems designing a versatile installation meeting all the requirements is practically impossible and economically unjustified. It is evident that engineering calculations and design adaptation shall be carried out in each case. An example of upgrading the demineralization scheme with the purpose of improving the capacity and conditioned water quality is presented. The result is achieved by the use of the two-stage reverse osmosis scheme that provides for the minimum chemical costs during the operation. The modernization of the facilities was carried out in continuous-duty service. Half year operation of the upgraded two-stage scheme the sustained quality of the demineralizaed water has been observed.

Key words

reverse osmosis , membrane module , permeate , two-stage scheme , water demineralization

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UDC 628.16.085:544.478.12

Petranovskii A. B., Nosenko V. A., Pugin A. I., Butorova I. A., Bol'shakova I. A.

Pilot testing of aqua®Lik technology

Summary

The description of the operation principle and results of using aqua®Lik new chemical free photocatalytic technology for preventing biological growth of cartridge filters, reverse osmosis membranes and inside surface of equipment is presented. The principle of the method consists in the activation of catalyzer that consists of an array of parallel catalytic plates by a visible light source. As a result of activation positive charge appears on the catalyzer plates. Negatively charged microorganisms present in treated water gravitate towards catalytic plates. On the plate surface the microorganism covers degrade and further oxidation of the degradation products takes place. In the process of photocatalytic rea ction the formation of biotenzides – surfactants of biological origin happens. Biotenzides break hydrogen bridging bonds that provide for the fixation of biological growth on wet surfaces; at that previously formed biofilms are washed out with water flow. Such treatment results in the formation of a thin film of biotenzides that prevent further biological growth on the equipment inside surfaces. The introduction of the given technology in reverse osmosis units provides for abandoning traditional biocidal chemicals, improving the permeate conversion of the unit, reducing the operational pressure on membranes, improving the operational life of cartridge filters before their replacement, increasing the period between regular chemical washings. When using this method the acclimatization of microorganisms to the biotenzide effect is absent compared to the cases of using biocidal chemicals.

Key words

reverse osmosis , biologic fouling , chemical washing , biotezides , cartridge filter , biofilms , biocidal treatment

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UDC 628.161.2.66.081.63

Askerniia A. A., Khamizov R. Kh., Migol' V. G.

Specific features of mass transfer of silicon compounds through reverse osmosis membranes

Summary

In the process of siliferous natural water treatment with different mineralization levels in two-stage reverse osmosis units the transfer of colloid (polymer) silica forms through permselective membranes at the second stage of water desiliconization takes place. Based on the results of the studies carried out in industrial-scale two-stage reverse osmosis units an attempt to analyze the results obtained in the model that took into account the efficiency of sediment formation on the active surface of a reverse osmosis membrane was made. The summary of the experimental results on siliferous natural water treatment with reverse osmosis is presented. A physico-chemical model of colloid silicon transfer through membranes is suggested that provides for precoat filtration effects and silicon depolymerization and polymerization processes during the solution passing through the corresponding filtering layers. In case of dynamic phase equilibrium availability precoat filtration results in the increase of dissolved silicon concentration fed on the effective membrane surface and subsequent (backward) recovery of the equilibrium composition in permeate. A proximate mathematical model for stable conditions of mass transfer is suggested.

Key words

sorption , reverse osmosis , natural water , colloid silicon , precoat filtration , membrane transfer

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UDC 628.165:66.081.63

Kurdiumov V. R., Timofeev K. L., Kraiukhin S. A.

Specific features of using reverse osmosis for mine water treatment

Summary

The possibility of using reverse osmosis for treatment of mine water from dead copper-nickel pits was studied. The composition of mine water was, mg/dm³: Mn 0,6–1; Fe 0,01–0,1; Ni 0,8–1,5; Cu 0,3–0,5; Zn 0,05–0,25; Co 0,02–0,07; Na 35–50; Ca 125–150;
Mg 35–45; SO4 100–200; Cl 65–75; Al 0,02–0,05; Si 9–11; Se 0,1–0,2; As < 0,005; Te < 0,005; Pb < 0,005; Hg < 0,00005; salt content 750–850; total hardness 9.5–11.5 °dGH; рН 7–7.5. The studies were carried out in a pilot plant with a capacity of 1 m³/h with original mine water. The plant included ultrafiltration and reverse osmosis modules. The permeate yield varied in the range of 50–75% of the original water volume. The method of chemical mine water demanganation and de-ironing at the primary treatment stage was tested. The quality of effluent (permeate) fully conforms to the drinking water requirements. The operating conditions of the pilot plant are described; the chemical unit consumption is presented. The specific features of using reverse osmosis technology for mine water treatment are described. The basic performance indicators of the reverse osmosis unit in terms of the equivalent amount of 1 m³/h at
the effluent output of 75% of the inflow are presented. The method of concentrate utilization is described providing its yield is reduced to 5% which makes it possible to extract valuable admixtures (non-ferrous metals).

Key words

deferrization , reverse osmosis , ultrafiltration , stability index , demanganization , concentrate utilization , mine water , non-ferrous metals

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UDC 628.165:62-278:621.311.21

Tsabilev O. V., Strelkov A. K.

Evaluation of full-scale reverse osmosis unit operational parameters

Summary

Undissolved and dissolved substances present in the water supplied to a reverse osmosis unit can form deposits. To minimize their negative effect the equipment for water pretreatment that ensures the water quality meeting the requirements set by the membrane elements manufacturers has been retrofitted into the general process flow scheme. The basic operational parameters of a full-scale reverse osmosis unit with spiral wound reverse osmosis elements are presented. Mathematical processing of the operational parameter values was carried out, the results gained were plotted. The changes in the operational parameters before and after chemical washing of the membrane elements are shown. The evaluation of the convergence of the design and actual data under the conditions considered is given. The quoted relationships allow evaluating the operational parameters of the membrane elements, determining the washing interval and efficiency of the chemical washing. The use of the presented method of evaluating the operational characteristics will also allow substantiating the warranty claims to the manufacturers of reverse osmosis units and membrane elements.

Key words

reverse osmosis , desalination , membrane technology , permeate , chemical washing , membrane element

DOI 10.35776/MNP.2020.05.06
UDC 628.32:66.081.63

Pervov A. G., Tikhonov Konstantin

Domestic wastewater treatment by reverse osmosis

Summary

Possible treatment of domestic wastewater by the reverse osmosis with the purpose of producing high-quality effluent suitable for the discharge into fishery water bodies or for the use as process water has been investigated. Possible recycling of reject water from a reverse osmosis unit by drastically reducing the flow rate to the value less than 0.5–1% of the incoming flow and removing the reject water as a moisture component of the dewatered sludge is presented. Experiments have been carried out to determine the change in the concentration of dissolved solids in the filtrate of the membrane apparatus and a decrease in the membrane capacity in the process of wastewater treatment and reject water flow reduction. The obtained dependencies allow to determine the following: the required flow rate of the reject water depending on the concentration of suspended solids and COD; the required filtrate yield depending on the concentration of ammonium in raw wastewater. The methodology for determining the surface area of membranes and the number of membrane apparatus at each stage of wastewater treatment is described. The optimal values of working pressure, economic indicators of the unit in comparison with other wastewater treatment technologies were determined.

Key words

reverse osmosis , concentrate utilization , domestic wastewater , reduction of reject water flow , apparatus with an open channel , membrane selectivity

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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

UDC 628.164-92:66.081.63
DOI 10.35776/VST.2023.05.01

Kasatochkin A. S., Larionov S. Iu., Kharitonov Nikolai, Shilov Mikhail, Савочкин А. Ю., Riabchikov Boris

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

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UDC 628.35:62-278

Pervov A. G., Matveyev N. A., Karasyev P. L., Motovilova N. B.

Removing oil products and detergents from surface runoff with the use of reverse osmosis systems

Summary

The studies of developing advanced technologies of surface runoff treatment from oil products and detergents are presented. The technologies are based on the process of reverse osmosis with the use of membrane units of a new type with an «open channel». Eliminating the causes of deposit formation can provide for ten-fold increase of the incoming water concentration in the units. The amount of concentrate (aqueous solution containing concentrated pollutants) is reduced to less than 1% of the initial water amount. With such small amount the concentrate is removed together with sludge. The estimations of the economic benefit of the rational utilization of surface runoff for technical purposes are presented.

Key words

suspended substances , oil products , reverse osmosis , surface runoff , water treatment , membrane unit , concentration factor

DOI 10.35776/VST.2022.08.07
UDC 628.32:66.081.63

Shirkova T. N.

Solid waste landfill leachate treatment and utilization of reverse osmosis reject water

Summary

The leachate of solid water municipal landfills contains high concentrations of organic waste decomposition products and mineral salts. COD concentrations in organic substances can reach 5,000 mg/l; of ammonium ions – 2,500 mg/l; of total dissolved salts – 15,000 mg/l. In order to meet the current regulations on the discharges into the environment including fishery water bodies, the treatment of such wastes by two- or three-stage reverse osmosis is required. The performance of modern reverse osmosis membranes designed for demineralization of groundwater and sea water is low due to high salinity and COD levels ​​in wastewater. Experimentally, the main dependences of the required reject water flow on the degree of ammonium ion removal were obtained. The use of nanofiltration membranes provides for reducing the reject water flow and operating costs. For the utilization of the reverse osmosis reject water, separating the waste flow into the following streams is proposed: with a high concentration of organic substances and with a high concentration of mineral salts, such as sodium and ammonium chlorides.

Key words

reverse osmosis , membrane selectivity , municipal solid waste landfill leachate , permeate yield increase , membrane performance decrease , membrane replacement expenditures

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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⁺, НCO^3- and SO₄^2- 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 SO₄^2- 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