RU2203226C2 - Device for electrochemical cleaning of potable water - Google Patents

Abstract

FIELD: cleaning potable water; improvement of physico-chemical and organoleptic properties of potable water. SUBSTANCE: proposed device has floatation chamber, electrolyzer and filter. Flat bottom of floatation chamber has hole which is matched with outlet hole of electrolyzer. Filter is made in form of vertical filtration baffle located at distance no less than 5 mm along walls of floatation chamber forming closed cavity for receiving cleaned water together with its walls; water escapes through hole found in wall of floatation chamber. Other hole made in cover of floatation chamber is used for discharge of gas and sludge formed during process. EFFECT: enhanced efficiency of cleaning; optimization of hydrodynamic characteristics of process. 6 cl, 2 dwg

Description

 The invention relates to the field of drinking water purification, specifically to electrochemical water purifiers.

 The scope of the present invention can be water purification in domestic conditions, in public institutions (nurseries, kindergartens, offices, etc.), and also as a group means of water purification in field water supply.

 Known devices for electrochemical water treatment have the widest range of contaminants removed from water. In this case, unlike devices that implement sorption, ion-exchange, or membrane technologies, in the devices of electrochemical water after treatment the salt composition of the water characteristic of the region practically does not change, i.e. mainly anthropogenic impurities are removed from the water. Due to the simplicity of adjustment and control, electrochemical water treatment technologies make it possible to obtain high-quality drinking water regardless of the physicochemical and organoleptic properties of the treated water. Unlike the most common sorption technologies, during the electrochemical treatment of water there is no accumulation of removed impurities in the device, therefore, the quality of the treated water remains unchanged throughout its life.

 There are various designs of devices for electrochemical water treatment described in the monograph by M. G. Granovsky, I. S. Lavrov, O. V. Smirnova "Electrical treatment of liquids (L., Chemistry, 1976).

 Known devices for cleaning liquids, including water, containing sequentially installed electrolyzer, flotator and filter (ed. Certificate. 1761676, 1761677, 1761678).

 Closest to the proposed technical solution for the technical essence is the "Device for cleaning liquid" according to ed. testimonial. USSR 1028603 (class C 02 F 1/24, 12/11/81). This device comprises a housing with a receiving and flotation chambers, an electrolyzer (electrocoagulator) and a cylinder with filtering material coaxially mounted in the flotation chamber.

 By the maximum number of similar essential features (flotation chamber, electrolyzer and filter) with the proposed device, it is selected for the prototype.

 The prototype device operates as follows. The processed liquid is supplied to the electrolyzer, where it is saturated with hydroxides of the metal of the electrode (anode) and gas bubbles generated during the electrolysis of the liquid at the cathodes and anodes of the electrolyzer, and enters the flotation chamber, in which flakes of hydroxides are formed and gas bubbles stick to the flakes. The resulting dispersions (flakes and other suspensions) move (float) to the surface, and the liquid through the flooded holes in the cylinder enters the filter (filter chamber) and then to the exit.

The disadvantage of the prototype is the lack of cleaning efficiency due to the features of hydrodynamics:
- through the flooded holes in the cylinder located below the foam collector, most of the floated contaminants (due to an increase in the flow rate when flowing into the cylinder) flows into the cylinder, where it settles on the filter partition;
- the area of the filter, corresponding in size to the cylinder, and the small height of the liquid layer above the filter baffle (especially taking into account the above drawback) allow us to assume that in the prototype auxiliary operations (washing the filter) will take at least equal to the main operation (filtering);
- flushing the prototype device may not be effective, because the pressure of water moving from top to bottom, even at a height of the working part of the device of 10 meters, will not exceed 1 atm, as a result, washing the filter material and the cell will be insufficient.

 The aim of the proposed technical solution is to increase the efficiency of treatment (improving the physicochemical and organoleptic properties of water), which is achieved by optimizing the hydrodynamic characteristics of the processes of electrochemical processing.

 This goal is achieved by the fact that in the device containing the flotation chamber, the electrolyzer and the filter, according to the invention, the bottom of the flotation chamber is made flat with an opening that is aligned with the outlet of the electrolyzer, while the filter, made in the form of a vertical filter wall, is located along the walls of the flotation chamber at a distance of at least 5 mm, forming a closed cavity with its walls to collect purified water with its outlet through an opening made in the wall of the flotation chamber. Another hole is made in the cover of the flotation chamber to discharge the generated gases and sludge.

 For a more complete achievement of the goal immediately above the outlet of the electrolyzer, above the bottom plane of the flotation chamber no more than 3 mm, a shielding plate is installed that overlaps the outlet around the perimeter by at least 10 mm.

 In addition, it is proposed that the lower edge of the vertical filter baffle be positioned at least 1/3 of the wall height of the flotation chamber.

 In addition, the device is additionally equipped with a final fine filter.

 Since the main formative unit of the device is a flotation chamber (as the largest unit in volume), it is also the most attractive for design. Based on this position, the shape of the flotation chamber can be cylindrical or in the form of a straight multifaceted (three, four, five or more faces) prism.

 The introduction of the above essential features provides, when combining the processes of electrolytic and electrochemical coagulation, electroflotation and filtering in one device, due to the hydrodynamic features of the process at each level of the processing process, an increase in the cleaning efficiency manifested in the improvement of the physicochemical and organoleptic properties of water.

 It is known that electrolytic coagulation occurs due to the dissolution of the anodes of the electrodes located in the electrolyzer, and electrochemical coagulation due to the influence of an electric field on metal ions (if they are present in water), for example, ions of iron, zinc, nickel, mercury, chromium, etc. The resulting metal hydroxides , including anodosoluble ones, move in the electrolyzer in the direction of flow to its outlet, combined with the hole in the bottom of the flotation chamber. During this movement, the resulting hydroxides (micelles) are mixed, especially when leaving the combined hole, due to a sharp expansion of the flow section and turbulization. Simultaneously with mixing, coagulants mature (flocculation). The flow of treated water at the exit to the flotator moves at a calculated low speed, which leads to laminarization of the flow. At a level no higher than 1/3 of the flotator wall height, the treated water moves laminarly, and flocculation is already completed. Since in the case of laminar flow, the near-wall water velocity approaches zero, conditions arise for a gradient perpendicular to the flow, and since the wall is a vertical filter wall at this level, water seeps through the specified wall: the process of filtering water into a closed cavity between the wall flotator and vertical filter baffle. Water leaves a closed cavity through an opening in the upper part of the flotator wall and is then used by a consumer. Coagulant flakes, continuing to move upward under the pressure of the flow, are collected under the flotator cover above the water level above the hole in the upper part of the flotator wall and are gradually displaced through the hole in the flotator cover into the drain.

 It is known that “with the help of the smallest gas bubbles, almost all fine dispersed substances, heavy metal hydroxides, polymers, oil fats, oil products, latexes, organic synthesis products, PVA, etc. are floated (Flotation methods in water treatment technology and experience in their application Baku, AzNIINTI, 1990. It is also known that all electrolysis processes are accompanied by the formation of gases at the electrodes: hydrogen at the cathode, atomic oxygen at the anode.

 In known electrochemical coagulation devices, this process is undesirable: a certain amount of energy is expended on the production of gases, the presence of gases (for example, oxygen at the anode) in the electrode space accelerates passivation.

 The combination of the electrolyzer and flotator vertically allowed these gases to be used as flotation reagent.

 In addition, taking into account the laminarity of the flow in the flotator and the unidirectional movement of the water flow and floated suspensions, the effect of concentrating the suspensions closer to the axis of the flotator arises, which greatly facilitates and improves the filtering process through the vertical partition.

 The introduction of a shielding plate covering the hole in the bottom of the flotation chamber increases the active mixing zone, optimizing the flow mixing process to more fully cover the entire treated volume of water by coagulation.

 The location of the lower boundary of the vertical filter septum at a level not lower than 1/3 of the wall height of the flotation chamber provides sufficient volume for the coagulant to mature, so that its flakes do not penetrate the filter septum.

 The implementation of the device with a flotation chamber in the form of a cylinder or a multifaceted direct prism is determined by the requirements of the consumer (location in the room, size of the area, etc.) and does not affect the quality of the treated water.

 The described technological methods can significantly improve the physico-chemical and organoleptic properties of the treated water.

 From the prior art, no technical solutions have been identified that have features that match the distinguishing features of the proposed technical solution, therefore, we can assume that the proposed device meets the condition of an inventive step.

 The essence of the proposed device is illustrated by drawings, where figure 1 shows a schematic illustration of the proposed device in section, figure 2 shows the internal hydrodynamics of the working device.

 The proposed device (figure 1) as well as the prototype contains an electrolyzer 1 with a package of soluble electrodes, a flotation chamber 2 and a filter 3, which are combined in a common housing. When this cell 1 is installed directly under the flotation chamber 2.

 Unlike the prototype, the bottom of the flotation chamber 2 is made flat with an opening that is aligned with the outlet of the electrolyzer 1. The implementation of the filter 3 in the form of a vertical filter wall with an arrangement along the walls of the flotation chamber 2 at a certain distance forms a closed cavity 4 between it and the walls of the flotation chamber 2 to collect purified water. The exclusion of the filter housing from the flotation chamber 2 improves the hydrodynamic parameters of the filtering process. The resulting closed cavity 4 is equipped with a nozzle 5 for the outlet of purified water through an outlet in the wall of the flotation chamber 2. To nozzle the gases and sludge through another hole in the cover 6 of the flotation chamber 2, a nozzle 7 is installed.

 The vertical filter wall 3 with the lower edge can be located at a height not lower than 1/3 of the wall height of the flotation chamber 2.

 Directly above the outlet 8 of the electrolyzer 1 in the bottom of the flotation chamber 2 is installed a shielding plate 9, the surface of which overlaps the hole 8.

 The device is equipped with an additional filter 10 connected by a pipeline to the outlet pipe 5 of the purified water outlet.

 To enter the treated (source) water in the lower part of the electrolyzer 1 there is a hole with a pipe 11.

 It is known that the formation of a coagulant in an electrolyzer is accompanied by the release of gases on the electrodes (hydrogen - at the cathode, oxygen and other gases - at the anode). Typically, these associated gases are undesirable. It is also known that there is an electroflotation technology in which the emitted gases are used to extract suspended impurities from water. The present invention allows for the implementation of electrolytic and electrochemical coagulation processes and electroflotation in the most favorable hydrodynamic mode. This is achieved by the fact that in the proposed device, the electrolyzer 1 is placed in the lower part of the device with the output of the resulting gases and metal hydroxides (coagulants) directly into the lower part of the flotation chamber 2 with their active mixing, since the flow leaves the narrow cell 1 in a wide cross-section flotation tank chambers 2 - "reverse currents - eddies arise" (AG Kasatkin. The main processes and apparatuses of chemical technology. M.: Chemistry, 1973). In chemical apparatus, this phenomenon leads to a waste of energy. In the proposed device, it is in the right place of the device that the flow is mixed, which is necessary for more complete coverage of all treated water by coagulation.

 To enhance this effect, a shielding plate 9 serves, which increases the active mixing zone.

 It is known that for the maturation of the coagulant (the formation of flakes) a certain time is needed. During this period, the filtering process is fraught with passage of hydroxide molecules through the filter baffle, followed by flocculation in the volume of purified water. The location of the lower boundary of the vertical filter walls 3 at a level not lower than 1/3 of the wall height of the flotator 2 provides the necessary and sufficient time interval for the maturation of the coagulant. To this level of flotator height, fluctuations of the velocity gradients in the flow (turbulization) cease, and its further movement is strictly laminar. This means that the principle of ideal displacement is implemented. Since in the laminar flow, the wall layers move at a minimum speed, the proposed device creates conditions under which the water being treated is filtered with a minimum velocity gradient perpendicular to the main flow, and the contaminants go to the top of the flotator, carried away by flotation reagents, and do not create any obstacles to filtering (figure 2).

 The implementation of the flotator in the section round, oval or polygonal does not affect the ongoing processes of water treatment, which ultimately does not affect the physico-chemical and organoleptic properties of the main product.

 The device operates as follows. The source water enters the device through the inlet pipe 11 in the lower part of the cell 1, in which it is exposed to the electric field of the electrodes of the cell. Moreover, since the electrodes (anodes) are soluble (as a rule, they are made of aluminum alloys), metal hydroxides of the anodes, for example aluminum hydroxide, are formed. Together with the gases formed, the aluminum hydroxide micelles are carried out by a stream from the electrolyzer 1 through the opening 8 and due to the sharp expansion of the outlet flow section and the influence of the shielding plate 9 above the outlet from the electrolyzer 1, the treated water is actively mixed. Further, the flow is directed vertically upwards and is laminated. When moving between the walls of the flotator 2 during the movement of the treated water to the lower edge of the filter vertical partition 3, coagulant flakes are formed and mature, to which gas bubbles in water adhere, i.e. the process of electroflotation begins. Given the unidirectional flow of the treated water and the flotation phase of the coagulant, a gradient of the vertical velocity of the water and flotation flakes of the coagulant occurs. This contributes to the development of a number of sorption processes on coagulant flakes that do not violate the laminarity of the main stream.

 Starting from a height of 1/3 of the flotator wall, where the lower boundary of the vertical filter baffle 3 is located, a velocity gradient arises perpendicular to the direction of flow towards the filter baffle, i.e. water is filtered into the closed cavity 4, limited by the walls of the flotator 2 and the vertical filter baffle 3. Filtered water leaves the closed cavity 4 through the pipe 5 for use by the consumer or is sent to the final (thin) filter 10. As a final filter (if necessary ) apply sterilizing filters based on bacterial (i.e. biophase retarding) filter baffles. At the same time, the process of electroflotation occurs - migration of coagulated impurities under the top cover 6 of the flotator 2. At the same time, under the cover 6, a constantly increasing volume of sludge is formed, which under the influence of the pressure of the treated water through the pipe 7 continuously exits (extrudes) from the device into the drain.

 A prototype of the inventive device with a capacity of 20 l / h. In the manufactured sample according to the invention, the electrolyzer 1 with a set of parallel soluble electrodes (the anodes are made of aluminum alloy) is installed under the bottom of the flotator 2. The exit from the cell 1 is aligned with the hole 8 in the bottom of the flotator 2. Directly above the hole 8 at a distance of 2 mm from the bottom of the flotator 2 a plate is fixed, the surface of which overlaps the specified hole by 15 mm around the entire perimeter of the hole (plate 9). The flotator casing is made of stainless steel square section. The lower part of the flotator has thickened walls up to a height of 1/3 of the flotator. At this level, from the thickened walls to the cover 6 at a distance of 8 mm from the walls of the flotator, a vertical polyester filter screen is installed. A closed cavity 4 is formed between it and the flotator walls. In the upper part of the sample, the outlet from the cavity 4 is made in the form of a pipe 5, and a pipe 7 is installed in the cover 6, connected by a hose to a drain.

 The tests of the sample and laboratory studies showed that during long-term operation of the device, the surface of the vertical filter baffle remains clean, and the performance of the device does not change (does not decrease). The discharge of sludge from the pipe 7 is stably uniform, which confirms the improvement of the hydrodynamic characteristics of the process.

 Laboratory tests also confirmed the improvement in the physicochemical and organoleptic properties of water after such treatment.

 For a number of devices of a similar design, but of different capacities, implementing the described water treatment technology, a hygienic certificate of water quality has been obtained.

 The most characteristic indicators of improving water quality obtained during testing of the sample are shown in the table.

 Improving the physicochemical and organoleptic properties of water after treatment has confirmed the concept of a significant effect of optimizing the hydrodynamic characteristics of the process on the quality of the treated water.

 Thus, the proposed device can be used for electrochemical treatment of drinking water, significantly improving its quality.

Claims (6)

 1. A device for the electrochemical purification of drinking water, containing a flotation chamber, an electrolyzer with a package of soluble electrodes, mounted directly below the flotation chamber, and a filter, characterized in that the bottom of the flotation chamber is made flat with an opening that is aligned with the outlet of the electrolyzer, while the filter made in the form of a vertical filter wall is located along the walls of the flotation chamber at a distance of not less than 5 mm, forming a closed cavity with its walls for collecting eyes water and its output through the hole made in the wall of the flotation chamber, another hole is made in the cover of the flotation chamber to discharge the resulting gases and sludge.  2. The device according to claim 1, characterized in that a plate is installed above the outlet of the electrolyzer in the bottom of the flotation chamber at a level not higher than 3 mm from the bottom plane, covering the outlet at least 10 mm around the entire perimeter.  3. The device according to paragraphs. 1 and 2, characterized in that the lower edge of the vertical filter walls is located at least 1/3 of the height of the wall of the flotation chamber.  4. The device according to claims 1, 2 and 3, characterized in that the flotation chamber is made in the form of a vertical cylinder.  5. The device according to claims 1, 2 and 3, characterized in that the flotation chamber is made in the form of a direct multifaceted prism.  6. The device according to claims 1 to 5, characterized in that it is additionally equipped with a final fine filter.

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