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 628.165:66.081.63
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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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 628.165:66.081.63
Removing calcium carbonate from reverse osmosis concentrate
by crystallization with seeding agent
Summary
The technology of removing calcium carbonate from reverse osmosis concentrate in the process of crystallization with seeding agent is described. Seed crystals are suspended in recycling concentrate flow. Owing to calcium carbonate depositing on the seeding agent the total salt content of concentrate decreases and high filtrate flow rate is provided that facilitates concentrate disposal. To implement the technology membrane apparatus with «open channel» are used that are resistant to the impact of membrane transfer of slightly water-soluble salts and suspended matter. Seed crystal growing is provided by dosing into concentrated caustic soda solution. Grown seed crystals were partially removed by sedimentation after hydraulic membrane wash. With the help of experimental diagrams it is possible to determine calcium carbonate crystallization rate depending on the influent water composition, the number of the seeded crystals, and filtrate yield. Process flow diagram of a continuously operating reverse osmosis plant is suggested. The methods of the process design are described: selecting the amount of recycling seed crystals, determining caustic soda consumption and tank size for calcium carbonate sludge precipitation. The estimations showed that to provide for calcium carbonate crystallization during continuous operation of the reverse osmosis plant caustic soda solution in amount of less than 5% of its stoichiometric amount required for the precipitation of the same amount of calcium carbonate from the influent water shall be regularly dosed into the recycling concentrate flow.
Key words
concentrate , water stabilization , concentrate utilization , reverse osmosis unit , calcium carbonate crystallization , seed crystals
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UDC 628.165
Pervov A. G., Andrianov A. P., Efremov R. V., Spitsov D. V.
Utilization of reverse osmosis concentrate with removing from it calcium and magnesium ions
Summary
The possible use of pre-developed technology of removing calcium carbonate with seeding agent to reduce the consumption of concentrate from large-scale units operating at the heat power facilities was studied. Concentrate of the operating reverse osmosis units contains inhibitors that inhibit the rate of seed crystal growth and impede the process of its utilization. The correlations between the calcium carbonate growth rate in the concentrate containing inhibiting substances and the dosage of the introduced seed, pH value and permeate yield were studied. For the implementation of the technology membrane apparatus with open channels are used that are resistant to the impact of membrane transfer of low-soluble salt deposits and suspended substances on the process. The developed by the authors technology of the concentrate utilization from reverse osmosis units installed at the heat power facilities for boiler feed water preparation is described. With the help of the developed technology softened water with lowered alkalinity and salt content can be produced. Herewith no chemicals are needed, and the unit does not consume water for its own needs. The technology provides for the complete utilization of reverse osmosis concentrate by improving its quality (in terms of hardness, alkalinity and total dissolved solids) to the requirements that allow using it for engineering purposes (for adding into a heat supply system or a circulation water supply system). Herewith any saline discharges into the environment are eliminated.
Key words
concentrate , inhibitor , reverse osmosis unit , concentrate utilization , calcium carbonate crystallization , seed crystals
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