RU2408541C2 - Method of effluents treatment - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to methods of effluents treatment and can be used for production of water suitable for agriculture, communal services, etc. In compliance with this invention, water preliminary cleaned of mechanical impurities is forced through electrolyser made up of cylindrical electrolyser chamber representing an insert into main pipeline with its axis aligned with that of the chamber. Then water is forced through sand. Here, gas liberated from water is withdrawn and sediment is washed off sand particle surface, said sediment comprising stuck sediment of metal compounds and other impurities. Note also that electrolytic chamber consists of sections accommodating cylindrical electrodes, one arranged along the axis of cylindrical chamber and another one mounted on chamber inner surface. Besides, said chamber is divided by common cylindrical ion-permeable web into anode and cathode spaces. Note that initial water flow is, first, forced through one section and, then through another sections with electrode charge signs opposite those of the first chamber.

EFFECT: high quality of water treatment, higher process efficiency.

3 cl, 1 dwg

Description

1. The technical field

The present invention relates to methods for treating wastewater, as well as waters unsuitable for use due to the high content of iron and other elements, and can be used to produce water required by the agricultural, municipal and other industries, while protecting the ecological environment from pollution .

2. The level of technology

Technological progress associated with the growing consumption of fresh drinking and industrial water in municipal, mining, agricultural and other branches of technology causes the growing need for clean water, which, due to technogenic pollution of the environment, is becoming an ever greater deficit. At the same time, there is an urgent problem of wastewater and other contaminated water treatment, including those located in the bowels of the Earth.

There is a method of simultaneous softening and iron removal of water, including passing water through a filling consisting of a mixture of activated carbon and ion exchangers: carboxylic cation exchanger in the Na ⁺ form, sulfonic acid cation exchanger in the H ⁺ form, sulfonic acid cation exchanger in the Ag ⁺ form and strongly basic cation exchanger in HCC ^- ₃ form (RU No.2010007, class C02F 1/28, 1994).

The disadvantage of this method is that with a small depth of softening, it does not provide the required degree of water purification.

The closest analogue of the claimed proposal, adopted as a prototype, is a method for simultaneous softening and iron removal of water, including passing the feed water through a backfill consisting of KU-2-8 cation exchanger in a Na ⁺ form treated with a weakly acid solution of Trilon B followed by regeneration of the spent cation exchanger first, by loosening and washing with water the precipitate of iron compounds from the surface of cation exchange resin grains, then by treatment with sodium chloride solution and weakly acid solution of Trilon B (RU No. 2176988, class C02F 1/42, 1997).

The disadvantages of the prototype are as follows:

- the use of backfill as electric charges, the charges of which do not correspond to the charges (pH) of the source water and can fluctuate over a wide range, which will require operational changes in the technology;

- the known method is technologically complex and time-consuming, in particular, due to the use of expensive and bulky materials.

3. Disclosure of invention

The objective of the invention is to increase the depth and degree of wastewater treatment due to the controlled use in the process of purification of an active chemical reagent - a hydrated electron (e _aq ^- ).

The problem is solved due to the fact that the method of wastewater treatment involves passing pre-cleaned from mechanical impurities source water through an electrolyzer, which is a cylindrical electrolytic chamber made in the form of an insert into the main pipeline, the axis of which coincides with the axis of the chamber, and the electrolytic chamber consists of sections, in each of which cylindrical electrodes are installed, one of which is installed along the axis of the electrolytic chamber, and the second on its inner surface it is divided by a common cylindrical ion-permeable partition for sections into anode and cathode spaces, while the flow of source water is sequentially passed first through one and then through another section, the electrodes of which have opposite charges relative to the electrodes of the first section, followed by passing water through sand at simultaneous selection of gases released from water and periodic washing out of the adhering sediment of iron compounds and other impurities from the surface of sand particles.

As a backfill, sand with high surface energy is used.

To intensify the release of methane-containing and other gases, the initial wastewater is preheated (40-60) ° C. The heating of the source water is carried out by passing through a chamber containing electric tene.

4. The invention

As the source of wastewater, wastewater is used that is preheated and purified from mechanical impurities (fin, solid and fiber-silt inclusions, etc.), using known means (gratings, nets, sedimentation tanks), and sand is used as backfill with high surface energy.

A diagram of the implementation of the inventive method is shown in the attached drawing, where 1 is a pipeline supplying pre-cleaned from mechanical impurities source water, 2 is a cylindrical electrolytic chamber made in the form of an insert into the main pipeline, the axis of which coincides with the axis of the chamber, consisting of two sections 3 and 4, in each of which cylindrical electrodes are installed, one of which is installed in the form of a rod 5 along the axis of the electrolytic chamber, and the second, in the form of a cylinder 6 - on its inner surface, inner diameter p of the cylinder of which coincides with the inner surface of the pipeline, and is divided by a common cylindrical, permeable to electric charges septum 7 into anode and cathode spaces having the same geometric dimensions and which are a continuation of one another, and the polarity of the signs of the electrodes in each section is opposite. 8 is a filter filled with backfill 9 in the form of sand with high surface energy, which ensures the acceptance of water-insoluble compounds of iron and other elements, with a device for the selection of released gases and gas impurities 10. In section 3, electrode 5 is the anode and electrode 6 is the cathode, and in section 4, the electrodes 5 and 6 are connected to opposite poles of the DC source.

The initial wastewater is preheated (up to 40-60) ° C using, for example, electric heaters.

The described device operates as follows.

The purified water is an electrolyte in which it is present in the most noticeable concentrations, mol / kg: H ₂ O - 53.6; Cl ^- - 0.546; Na ⁺ - 0.469; Fe ³⁺ 0.60; Mg ²⁺ - 0.0528, - ions that determine the conductivity of the electric current of electrolytes (Izmailov N.A. Electrochemistry of solutions. 3 ed., M., 1976).

Ionic conductivity is provided as follows. Under the influence of the electric field created by connecting the anode (+) and the cathode (-) of the electrolyzer to the direct current source, positive ions (cations) go to the cathode 6 of section 3 (in section 4 the direction of electrons is opposite) of the cylindrical electrolytic chamber 2, divided by a common ion-permeable septum 7 for both sections, mounted on the water supply pipe 1, where the positive ions that make up the purified water receive the electrons that they lack, while negative ions (a nions) go to anode 5, to which they give away excess electrons.

Thus, providing the ionic conductivity of the solution, the electrodes neutralize the ions that came to them, which lose their electrical connection with them, turning into atoms of the corresponding substances, leaving the sampler 10 or precipitating on the sand surface 9 of the sump 8, located behind section 4, t. e. the anions and cations of the water being purified give away excess electrons to the anode or anions and receive the missing electrons from the cathode or from cations, as a result of electron replacement reactions with the simultaneous neutralization of the corresponding charges of both the anions and cations deposited from the solution in the filter 8 located behind the electrolytic chamber 2 and gases are taken away by device 10, and solid waste settles on the surface of sand 9, from which they are periodically washed off by a reverse current of water (not shown in the drawing, so as not to clutter the process th scheme).

The physical essence of the process of adhesion of solid ionized impurities to the sand surface is as follows. As is known, the surface layer of solids bordering a liquid is usually composed of electrons, i.e. it is negative, in connection with which each grain of sand is enveloped in positive ions (FeO ²⁺ , etc.). In turn, the formed surface layer of positive ions attracts negative ions, etc. Thus, on the surface of the sand, all solid impurities are accumulated, which were previously ionized in the electrolytic chamber 2. In this case, the iron compounds and other impurities are in a hydrolyzed form and are easily washed off by the reverse water flow (not shown in the diagram).

Water in the anode zone is saturated for a fraction of a second with highly active oxidizing agents: HClO, O ₃ , H ₂ O ₂ , etc., which ensure the destruction of impurities and bacteria.

When hydrated electrons (e ^- _aq ) enter the wastewater, i.e. surrounded by the solvation shell of electrons e ^- , the source of which is the cathode of the electrolyzer, in the cathodic and anodic zones (partly in the volume of water, where there are exchange reactions caused by different electron affinities of certain substances), chemical reactions such as the following occur (Hart E., Anbar M. Hydrated electron. M.: Atomizdat, 1973. 268 p.):

Cathodic reactions: A ^{n +} + e ^- _aq → A ⁿ , for example:

2Na ⁺ + 2e ^- _aq + SO ₄ ^2- → Na ₂ SO ₄ ↓ (e ^- _aq plays an associative role);

Na ⁺ + Cl ^- + e ^- _aq → NaCl ↓ (e ^- _aq plays an associative role);

Ca ²⁺ + 2e ^- _aq + 2H ₂ O → Ca (OH) ₂ ↓ + H ₂ ↑ (e ^- _aq plays an associative role).

NH ₃ ⁺ + e ^- _aq → NH ₃ ↑

Anode reactions: A ^n- -e ^- _aq → A ⁿ , for example:

2Cl ^- -2e ^- _aq → Cl ₂ ↑

4OH ^- -4e ^- _aq → 2H ₂ ↑ + 2O ₂ ↑

2Al + 3H ₂ O-6e ^- _aq → Al ₂ O ₃ + 3H ₂ ↑

Considering that in devices for wastewater treatment (aeration tanks, digesters) mainly oxidative reactions, “burning” impurities take place, it is advisable to pass wastewater mainly through the anode chambers of the electrolyzer, where oxidative reactions take place, removing ions of impurities from solutions, such as the following :

- for CH ₂ - groups of ethylene and hydrogen: 2H ⁺ + CH ₂ ^2- → CH ₄ ↑;

- for calcium oxide and methane: CaO ²⁺ CH ₄ ^2- → CH ₄ ↑ + CaO ↓

To obtain predominantly oxidative (anodic) reactions, such as the above, various techniques are known from the prior art, such as repeated passage of catholyte through an electrolyzer, different sizes of anode and cathode chambers, etc. (V.M. Bakhir, Yu.G. Zadorozhny. Installations for electrochemical conditioning and purification of drinking water. Electrochemical activation. Second International Symposium. M., 1999, p.342-356).

During the flow of water through the anode space, anodic oxidation products are formed, for example, HClO, ClO ^- , as well as ozone and oxygen, oxidizing microorganisms and organic impurities of the type:

HCHO + 2OH ^- 2e ^- _aq → H ₂ ↑ + CO ₂ + H ₂ O

Thus, passing first through the anodic (cathodic), and then the cathodic (anodic) cells of the electrolyzer, the purified water undergoes neutralization of both cations and anions, simultaneously ensuring the dissociation of organic impurities into more accessible forms.

Considering that water with one or another degree of hydrogen index (pH) is desirable for the corresponding technological processes, the necessary water can be obtained by appropriately adjusting the parameters of the electrolyzer, in particular its electric field strength or increasing the electrode contact area. It is known that, for example, alkaline water is needed for washing oil or gas wells, acidic for leather processing or for room disinfection, and for most crops, irrigation water with pH> 7.0 is the most favorable, which agronomists call "Living water", in contrast to water with a pH <7.0 ("dead water"). At the same time, certain plant species prefer water with different pH, up to pH <7.0, which is consumed by solonchak plants that bloom and bear fruit only on solonchaks (Genkel P.A. The main ways of studying the salt tolerance of plants. Agricultural biology, 1970, t .5, No. 2).

To intensify the release of methane-containing and other gases, the initial wastewater is preheated (up to 40-60) ° C, for which purpose electric heaters are placed in it.

As you can see, the method according to the invention can be carried out by inserting into a pipe in which cylindrical electrodes are installed, to which a constant electric current is connected. Given the high conductivity of wastewater, a thousand times higher than the conductivity of ordinary drinking water, anode and cathode processes will occur in the entire volume of water passed through the electrolytic chamber.

5. Technical results

The present invention provides a cheap method of producing large volumes of purified wastewater without the use of expensive chemicals and without significant energy costs, such as electrodialysis or reverse osmosis.

An additional effect may be the production of (combustible) gases capable, in particular, of generating electrical energy.

Solid sediments falling in the sump located after the electrolytic chamber are removed in large quantities (the ratio of water to sludge is approximately 100: 5) and can be used in the mining industry (up to gold mining) and as building materials.

At the same time, the sectional design of the electrolyzer provides effective separation of the media with minimal hydraulic resistance.

The advantage of the claimed method compared to the prototype is that it provides more opportunities for both anodic and cathodic neutralization of harmful substances that are removed from the purified water, at higher technical and economic indicators of the cleaning process.

Claims (3)

1. The method of wastewater treatment, including passing pre-purified from mechanical impurities source water through an electrolyzer, which is a cylindrical electrolytic chamber, made in the form of an insert into the main pipeline, the axis of which coincides with the axis of the chamber, and the electrolytic chamber consists of sections, in each of of which cylindrical electrodes are installed, one of which is installed along the axis of the electrolytic chamber, and the second on its inner surface, and is divided by a common cylinder for sections ion-permeable septum to the anode and cathode spaces, while the flow of the source water is sequentially passed first through one and then through another section, the electrodes of which have opposite charges relative to the electrodes of the first section, followed by passing water through the sand while removing gases released from the water and periodic washing away from the surface of sand particles of adhering sediment of iron compounds and other impurities. 2. The method according to claim 1, characterized in that the source wastewater is preheated. 3. The method according to claim 2, characterized in that the initial wastewater is preheated with electric heaters.

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