RU2500625C1 - Method of electro-chemical processing of water and device - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to method of electro-chemical processing of water by disinfectants, which can be applied for processing of drinking water, domestic and industrial sewages, and water of swimming pools. Method includes introduction into processed water of disinfectants, obtained by direct electrolysis in flowing regimen of processed water, which contains sodium chloride, with application of water, which contains 0.1÷20 mg/l of sodium chloride. Invention also relates to device for electro-chemical processing of water by disinfectants, which contains body with input and output branch pipes, polarity-changing titanium electrodes, means for supply of current to electrodes, and change of polarity takes place with pause from several seconds to several hours, and inter-electrode distance constitutes less than 1 mm.

EFFECT: possibility of reagent-free control of water properties with low content of chlorides, resulting in direct disinfection.

3 cl, 1 tbl, 2 dwg

Description

The invention relates to methods for electrochemical treatment of water. It can be used for the treatment of drinking water, domestic and industrial wastewater, swimming pool water.

The technical result of the invention is the possibility of reagent-free (without the addition of chemicals) management of the properties of water with a low chloride content of 0.1 ÷ 20 mg / l, leading to direct disinfection.

A known method of treating water with sodium hypochlorite, implemented in RU 2100483 from 02.19.1996, in which the disinfectant is produced at the place of consumption by direct electrolysis of underground saline water with a sodium chloride content of from 1.5 to 15 g / l. The disadvantage of this technical solution is the inability to use water with a sodium chloride content of less than 1.5 g / l.

Also known is a method of producing ultrapure drinking water, including the synthesis of ozone from air and passing it through a layer of treated water, implemented in RU 2114790 of 04.17.1998, in which the current density in the electrolytic cell is regulated depending on the concentration of substances in the water and the change in the polarity of the electrodes. It has one significant drawback: the synthesis of ozone from air, which significantly reduces the safety of this method.

A device for electrolysis is known, implemented in RU 2139956 from 06/04/1997 in which titanium anodes and cathodes with an oxide-ruthenium coating with current reversal are used. The device sharply limits the life of the electrolyzer since changing polarity reduces the service life of the electrodes.

The closest technical solution is the installation of the "Potok" type manufactured by the Kommunalnik plant for disinfection of water by direct electrolysis, presented in the Guide to SNiP 2.04.02-84. The disadvantage of the "Stream" type installation is the inability to disinfect natural waters with a chloride content of less than 20 mg / l.

Also, from BG 66016 B1 of 10.29.2009, a method for carrying out electrolysis and a device for conducting it are known, which involves the use of groups of electrodes EK1 - EKn electrically connected to a power source (1), each of which contains at least one pair of oppositely charged electrodes, while in the process of electrolysis, the electrical circuit is switched through the switching unit (3), which provides alternate connection to the power source and disconnecting groups of electrodes from it. According to an example implementation of the known method, the frequency and duration of connecting the power source to the groups of electrodes is determined by the control unit (5), which monitors the power of the direct current supplied to the groups of electrodes (page 3, zone 30 to the right). Thus, in BG 66016 B1, the principle of disconnecting the power supply and subsequent switching on is used to maintain the necessary direct current strength on the groups of electrodes without changing the polarity.

The problem to which this invention is directed, is to provide a water treatment method and a device for implementing the method in which water with a small amount of chlorides could be used to disinfect water to reduce the cost of water treatment technology while ensuring environmental safety, as well as eliminating the resulting deposits hardness salts on electrodes of electrolysis devices with a significant increase in the service life of electrolysis devices.

The essence of the invention lies in the fact that to obtain disinfectants - hydroxyl radical (OH), atomic oxygen (O), oxygen (O ₂ ), ozone (O ₃ ), hydrogen peroxide (H ₂ O ₂ ), chlorine radicals (hypochlorous acid HClO and hypochlorite ion ClO ^- ) by direct electrolysis in a flowing mode using treated water containing 0.1 ÷ 20 mg / l sodium chloride. In this case, the interelectrode distance is less than 1 mm. Moreover, between the moment of power failure and the moment of switching on with opposite polarity there is a pause from a few seconds to several hours.

Repolarization is used to remove deposits of hardness salts on the surface of the electrodes. The pause between the periods of the power supply of the device eliminates the negative effect of transients on the active metal oxide coating of the electrodes and extends the life of the coating in the mode of repolarization by 3-5 times.

The authors theoretically discovered and experimentally confirmed that the electrolysis of water with a small amount of chlorides (0.1 ÷ 20 mg / l) activates not only the salt dissolved in drinking water to produce chlorine radicals (hypochlorous acid HClO and hypochlorite ion ClO ^- ), but and oxygen bonds into effective disinfection. The process provides the splitting of water molecules (H ₂ O) into several powerful non-toxic oxidizing agents - free radicals (O, O ₂ , O ₃ , OH, H ₂ O ₂ ), each of which has a much greater oxidative potential than chlorine. Radicals powerfully strengthen each other, and act simultaneously in bacteriological, physical and organic terms.

Figure 1 shows the results of an experiment to obtain free chlorine Cl ₂ and oxygen O ₂ by direct electrolysis of the treated water in flowing mode at a speed of 200 m ³ / h with a 6 kW device.

It can be seen from the graph that during direct electrolysis of water with a chloride content of less than 20 mg / l, oxygen O ₂ is formed mainly, and in water with a chloride content of more than 20 mg / l, reactions with the formation of dissolved chlorine Cl ₂ prevail.

Table 1 shows the indicators of analysis of the source and processed by direct electrolysis of water in the flow mode of the northwestern part of the Krasnodar Territory.

Table 1 Water quality indicators Units rev. Normative Source water Treated water Smell 20 ⁰ point 2 3 0 60 ⁰ point 2 3 0 Smack point 2 3 0 Color hail twenty 51.3 12 Turbidity mg / dm ³ 1,5 2,5 <1.0 Permanganate oxidation mg O ₂ / dm ³ 5,0 7.2 0.54 Iron (general) mg / dm ³ 0.3 0.28 0.2 Ammonium ion, ammonia mg / dm ³ 1,5 2,35 0.01 Nitrate ion mg / dm ³ 45.0 0.604 0.5 Nitrite ion mg / dm ³ 3.0 0.016 0.003 Hydrogen sulfide mg / dm ³ 0.003 1,2 0 Sulphates mg / dm ³ 500,0 489 485.1 Chlorides mg / dm ³ 350,0 17 6 Chlorine residual free mg / dm ³ 0.3-0.5 0 0.34 Chlorine Residual Bound mg / dm 0.8-1.2 0 0.5 Oxygen mg / dm ³ - 5 9

As can be seen from the table, obtained in the process of direct electrolysis, disinfectants not only destroy organics - spores, viruses, bacteria and other microorganisms, which is guaranteed by the presence of residual chlorine, while providing clean, drinkable water quality, but also affect the content of dissolved iron, ammonia and hydrogen sulfide.

In the process of direct electrolysis, a number of oxidizing agents are synthesized, and the following reactions occur:

Iron removal

Ferrous iron is oxidized by electrolysis oxygen to ferric hydroxide.

4Fe ²⁺ + O ₂ + 8OH ^- + 2H ₂ O → 4Fe (OH) ₃

Ammonia removal

Ammonia is oxidized by electrolysis ozone to nitrate.

NH ₃ + 4O ₃ → NO ₃ ^- + 4O ₂ + H ₃ O ⁺

Hydrogen sulfide removal

Hydrogen sulfide is oxidized by electrolysis of hydrogen peroxide to colloidal sulfur.

H ₂ S + H ₂ O ₂ → S + 2H ₂ O

In a simplified form, the processes of the formation of disinfectants from fresh water are as follows.

During the electrolysis of water, oxygen and ozone are released:

2H ₂ O → O ₂ + 4H ⁺ + 4е ^- ; 3H ₂ O → O ₃ + 6e ^- + 6H ⁺

Dissolving in water, oxygen can form hydrogen peroxide:

O ₂ + 2H ₂ O + 2e ^- → H ₂ O ₂ + 2OH ^-

In water, even with a very low chloride content, chlorine can be produced:

2Cl ^- → Cl ₂ + 2е ^-

Hydrolysis of chlorine produces hypochlorous acid (HClO) and hypochlorite ion (ClO ^- ):

Cl ₂ + H ₂ O → HClO + HCl;

The sum of the concentrations of hypochlorous acid and hypochlorite ion is usually called free chlorine.

The above oxidation reactions are only a small part of the complex processes and reactions that occur during the electrolysis of water. But in the end result, all of them lead to a decrease in the concentration of these substances to the MPC standards and, as a result, to the removal of color and turbidity.

Direct electrolysis differs from common disinfection methods in that it combines their positive effects and does not contain their negative properties: it has an aftereffect and does not create by-products.

Oxygen, as the most powerful oxidizing agent, predominates in disinfection reactions, and free chlorine plays a secondary role, and having “fulfilled the mission” of a prolonged action, it again turns into chlorides.

Thus, disinfectants are produced from the water itself and, having fulfilled their function, are transferred to their previous state without introducing by-products into the water.

From the prior art (see Medrish G.L., Teisheva A.A., Basin D.L. Disinfection of natural and waste water using electrolysis, Moscow, Stroyizdat, 1982, p. 10) it is known that to create small-sized and high-performance installations it is most appropriate to provide the minimum possible interelectrode distances. For the existing level of device performance in 1982, it was 3-6 mm. The smaller the interelectrode gap in the cell, the more energy efficient the electrolysis process. With the current existing level of high-tech device design, an interelectrode gap of less than 1 mm can be achieved without the danger of contact between the electrode surfaces. For example, electrolyzers produced by NPF Nevsky Crystal LLC have an interelectrode distance of 0.9 mm and are successfully operated in many regions of Russia and the CIS countries.

Figure 2 shows the results of an experiment to study the life of the coatings of the electrodes when working with pauses and without a pause between the periods of the power supply of the electrolyzer.

A sharp increase in voltage on the electrolysis cell indicates the complete activation of the active coating and the exhaustion of the electrode life. Among the studied electrodes, the shortest life of six months was found for electrodes operating without a pause. Pause electrodes have demonstrated a life of more than 2 years. In this case, the formation of deposits of hardness salts on the electrodes was eliminated when they were reversed, and the interelectrode space was not overgrown with sediment during the entire experiment.

The above example indicates that in the case of the application of the proposed technical solution, it is possible to produce a sufficient amount of disinfectants from a small amount of natural mineral salts that are present in any source of fresh water.

From the above description it is clear that the present invention can be implemented in other specific forms without departing from the essence of the invention defined by its formula.

Claims (3)

1. The method of electrochemical treatment of water with disinfectants, including the introduction of disinfectants into the treated water, obtained by direct electrolysis in a continuous flow mode of treated water containing sodium chloride, characterized in that water containing 0.1 ÷ 20 mg / l sodium chloride is used. 2. The method of electrochemical treatment of water according to claim 1, characterized in that the disinfectants are hydroxyl radical (OH), atomic oxygen (O), oxygen (O ₂ ), ozone (O ₃ ), hydrogen peroxide (H ₂ O ₂ ), chlorine radicals (hypochlorous acid HClO and hypochlorite ion ClO ^- ). 3. A device for electrochemical treatment of water with disinfectants according to the method according to claim 1, comprising a housing with inlet and outlet nozzles, polarity-changing titanium electrodes, means for supplying current to the electrodes, characterized in that the polarity changes in a pause from a few seconds to several hours, wherein the interelectrode distance is less than 1 mm.

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