Water purification method and device for carrying out same

Abstract

The present invention relates to methods and devices for purifying industrial and natural water of iron, manganese and petroleum products by oxidation of the contaminants with ozone, followed by dissolved air flotation and filtration. The method and device according to the present invention provide for efficient purification of water, while minimizing the costs of carrying out the purification process and maintaining equipment.

Description

[0001] Method of water purification and device for its implementation

[0002] Field of technology.

[0003] The present invention relates to methods and devices for purifying industrial and natural waters from iron, manganese and petroleum products by oxidizing impurities with ozone, flotation and subsequent filtration.

[0004] State of the art.

[0005] Purification of industrial and natural waters from manganese, iron, and petroleum products is a pressing issue for chemical industry production, requiring a systematic approach and the use of effective methods.

[0006] A method for purifying water from iron compounds is known from the prior art according to patent US4780215A [1] “Water Purification Device”, which includes obtaining ozone-enriched air by passing an air stream through an electric arc, supplying an ozone-enriched air stream to water located in a well (borehole), removing water after oxidation of impurities from the well (borehole) and filtering it.

[0007] The disadvantages of this method include low impurity oxidation efficiency due to the short contact time and surface area between ozone and water. After a short passage through a water layer (bubbling), the ozone freely escapes into the surrounding area. A high ozone flow rate is required to ensure the required degree of impurity oxidation. It is noted that an air vent is located at the top of the well (borehole), which leads to the free escape of ozone that has not had time to react in the water column. This arrangement can be harmful to human health. The method does not disclose the preferred filtration method or the procedure for removing the sediment formed in the well during impurity oxidation. The method also does not include methods for removing impurities in the form of petroleum products.

[0008] A method for purifying groundwater from iron and manganese is known from the prior art according to patent RU2105729C1 [2] “Method for purifying groundwater from iron and manganese”, which includes ozonation and sequential two-stage filtration through a granular bed with water supplied from the bottom up in the first stage and from the top down in the second stage, characterized in that before water is supplied to the first stage, it is subjected to simplified aeration, and ozonation is carried out before the second stage of the filter in an amount of 3.5-5.5 mg / dm3. 3 , and the diameter of the porous loading of the first stage of the filter is 1.25-2.5 mm, the second stage 0.63-1.25 mm.

[0009] The disadvantage of this method is the need for periodic replacement of the granular media and two-stage oxidation, which is not always technologically feasible. The method does not remove impurities such as petroleum products from the water.

[0010] A method for purifying industrial wastewater using electrochemical methods and processes of additional oxidation is known from the prior art according to patent RU2624643C2 [3] “Method and device for electrochemical treatment of industrial wastewater and drinking water”, which includes a phase of preparing the contaminated medium by sedimentation, a reaction phase in the first reactor vessel, where the contaminated medium is treated with reactor electrodes made of fixed stainless steel plates, through which direct current is passed with electrocoagulation, electrooxidation, electroflotation and disinfection of the medium by means of ozone circulation and UV irradiation with circulation and electromagnetic and ultrasonic treatment, a reaction phase in the second reactor vessel, where the contaminated medium is treated with reactor electrodes made of fixed steel plates,through which a direct current is passed with subsequent passage through an additional set of reactor electrodes made of fixed aluminum plates with electrocoagulation, electrooxidation, electroflotation and disinfection of the medium by means of ozone circulation and UV irradiation with circulation and electromagnetic and ultrasonic treatment, a coagulation and flocculation phase, a separation phase by sedimentation, an additional oxidation phase with simultaneous ozonation and ultraviolet radiation treatment, a filtration phase through a sand filter and an activated carbon filter.

[0011] The disadvantages of this method include the complex design of the equipment required for its implementation and its excessive use for water purification from impurities, primarily iron and manganese. The use of reactors with electrodes for electrocoagulation, electrooxidation, and electroflotation is energy-intensive and requires regular electrode replacement. This method also does not remove impurities such as petroleum products.

[0012] A device for purifying wastewater from detergents, oil, and scale is known from the prior art, according to patent KR100538347B 1 [4]. The device provides ozonation followed by flotation and filtration. The flotation operation allows for the separation of petroleum product impurities.

[0013] The device allows for the oxidation of impurities, as well as the separation of impurities in the form of petroleum products, but the patent does not disclose optimal methods for ozonation, separation, and filtration of solid impurities, which is necessary for the industrial processing of water contaminated with iron and manganese.

[0014] A device for water purification is known from the prior art according to patent CN214031993U [5], in which flotation is carried out together with ozonation.

[0015] The disadvantages of the device are its complex design, which is not adapted for the purification of water from iron, manganese and petroleum products; the device serves the purpose of processing water obtained during the process of growing aquaculture.

[0016] The prior art discloses a method and device according to patent RU281 1343C1 [6], which provide reagent-free purification of water from iron and manganese.

[0017] The method includes treating water with ozone by mixing water and ozone in an ejector, mixing water and ozone in a static mixer, directing water into a settling tank for sedimentation, filtering water using at least one disc filter with a filtration rating of at least 20 μm, and tangential microfiltration of water using the cross-flow method.

[0018] The device comprises an ozone generator, an ozone supply line, a water supply pump, a water supply line, an ejector for mixing water with ozone, a static mixer located downstream of the ejector, a sedimentation tank for sedimentation, at least one disc filter with a filtration rating of at least 20 µm, and at least one tangential microfiltration filter installed downstream of the disc filter, providing tangential microfiltration using a cross-flow method. This method and device fully satisfy the requirements for water purification from iron and manganese, but do not effectively remove petroleum contaminants.

[0019] This patent was selected as a prototype.

[0020] Finding an effective method for purifying water from iron, manganese, and petroleum products is a pressing issue for the petrochemical industry.

[0021] The essence of the invention.

[0022] Natural waters and brines produced during oil and gas production contain petroleum-based impurities, which negatively impact the processing of waters and brines to extract valuable chemical components or produce water suitable for industrial use. Manganese and iron are also undesirable impurities; their presence affects the purity of the final products and leads to increased stress on equipment and contamination.

[0023] The aim of the present invention is to ensure efficient purification of water from iron, manganese and petroleum products while reducing the costs of the purification process and equipment maintenance.

[0024] The stated objective is achieved by treating water with ozone by mixing water and ozone in an ejector, mixing water and ozone in a static mixer, directing water into a settling tank for sedimentation, filtering water using at least one disc filter with a filtration rating of at least 20 μm and tangential microfiltration of water using the cross-flow method, while after mixing water and ozone in a static mixer and before directing water into a settling tank for sedimentation, adding a flocculant to the water and pressure flotation are carried out.

[0025] The stated objective is achieved by implementing the method using a device comprising an ozone generator, an ozone supply line, a water supply pump, a water supply line, an ejector for mixing water with ozone, a static mixer located downstream of the ejector, a pressure flotation device, a sedimentation tank for sedimentation, at least one disc filter with a filtration rating of at least 20 μm, and at least one tangential microfiltration filter installed downstream of the disc filter and providing tangential microfiltration using a cross-flow method. The claimed technical result: efficient purification of water from iron, manganese, and petroleum products, reduced purification costs, reduced labor intensity and frequency of filter equipment maintenance, efficient oxidation of impurities, and economical ozone consumption.

[0026] The technical result is achieved by the fact that during the water purification process, the mixing of water with ozone is carried out in an ejector and then in a static mixer, which ensures the most complete mixing and the greatest possible contact of impurities with ozone, which ensures their most complete oxidation and savings in ozone consumption.

[0027] The device for implementing this method also ensures mixing of water with ozone in the ejector and then in the static mixer.

[0028] The technical result is achieved by using pressure flotation in the water purification process, which ensures the effective removal of petroleum product impurities by saturating the treated water with air bubbles supplied from a compressor.

[0029] The technical result is achieved by introducing a flocculant into the water before pressure flotation to ensure the operation of the flotation unit. The flocculant dosage depends on the amount of pollutants, which ensures the effective separation of petroleum products.

[0030] The technical result is achieved by using a settling tank to settle and separate insoluble sediment during the process of water purification from iron and manganese. This increases the continuous operation time of the filters by separating some of the impurities before filtration. This also reduces hydraulic resistance and increases the overall service life of the filter elements.

[0031] The device for implementing this method is also equipped with a settling tank for sediment settling; the device can also be equipped with a sediment discharge system.

[0032] The technical result is achieved by using at least one disc filter with a filtration rating of at least 20 µm in the first filtration stage. The use of such disc filters reduces the load on the tangential filters by filtering coarse contaminants. This filtration rating does not create excessive flow resistance or excessive load on the pumping equipment. Furthermore, the disc filters can be cleaned without disassembling or removing them. The device for implementing this method is also equipped with at least one disc filter with a filtration rating of at least 20 µm.

[0033] The technical result is achieved by the fact that at the second stage of filtration, tangential microfiltration is carried out using the cross-flow method, which ensures a high degree of purification from suspended and colloidal substances, achieving less than 3 mg / dm3. 3by the total content of iron and manganese, while the tangential microfiltration unit does not require frequent maintenance due to the fact that in the tangential scheme the membrane walls are less susceptible to fouling with impurities due to the flow movement along them.

[0034] The device for implementing this method is also equipped with a cross-flow tangential microfiltration unit.

[0035] The technical result is achieved by treating the water with an alkaline solution before ozone treatment, ensuring a pH of at least 5. This ensures water purification with minimal reagent (flocculant) dosage. If the source water pH is above 5, no alkaline addition is required, which is cost-effective. Maintaining the required pH positively impacts the efficiency of ozonation and pressure flotation water purification processes.

[0036] For these purposes, the device for implementing this method can also be equipped with a flocculant supply line, which provides the supply of flocculant into the water flow, or a line that provides the supply of flocculant into the pressure flotation device.

[0037] Description of drawings.

[0038] Fig. 1. General diagram of the water purification plant.

[0039] Fig. 2. Schematic diagram of a water purification plant. Example 1.

[0040] Fig. 3. Schematic diagram of a water purification plant. Example 2.

[0041] In the most general form, the purification of water from iron, manganese and petroleum products according to the present invention is carried out as follows.

[0042] Contaminated water is sent to the ejector with the simultaneous supply of ozone to it, where due to the increase in the cross-section of the channel in the ejector a vacuum zone is created, where ozone is sucked in, which ensures the uniformity of its supply and distribution in the water flow, from the ejector the ozone-saturated water enters the static mixer, where additional mixing of the flow occurs, which increases the efficiency of oxidation by increasing the uniformity of the distribution of ozone in the volume of water, from the static mixer the water enters the pressure flotation unit, where due to the supply of gas to the water and the formation of bubbles, the separation of water and oil products occurs, the oil products are removed, and a partial sediment of iron and manganese impurities precipitates, and the water then enters the settling tank for sedimentation, where sedimentation occurs in the form of iron and manganese oxides, the settling tank is made in the form of a container with a conical bottom, which has an outlet for unloading the sediment, for example, using a screw,In a tailings storage facility. Excess ozone is removed from the top of the settling tank into a thermal catalytic destructor. From the settling tank, water enters a filtration unit with disc filters, where the final filter has a filtration rating of 20 μm, which ensures the removal of most insoluble impurities, including manganese and iron oxides. After the filtration unit with disc filters, the water enters tangential cross-flow filtration using a filter element with a filtration rating of 0.2 μm. This separates the solutions into a concentrate containing the bulk of the impurities and a permeate in the form of purified water, which enters a purified water tank. The concentrate is discharged into the settling tank. To improve the separation of petroleum products, a flocculant is mixed into the flotation tank or the liquid stream after ozonation.

[0043] Water purification can be carried out in the manner specified, but is not limited to it.

[0044] In its most general form, the diagram of the installation for implementing the method is shown in Fig. 1 and includes: an ozone generator (1), an ozone supply line (2), a water supply pump (3), a water supply line (4), an ejector for mixing water with ozone (5), a static mixer (6), a pressure flotator (7), a flocculant source (8), an oil product accumulator (9), a sedimentation tank for settling sediment (10), a disc filtration unit (11) equipped with a filter with a filtration rating of 20 μm, a tangential microfiltration circuit (12), and a container for collecting purified water (13).

[0045] The aforementioned water purification system can be implemented using the claimed elements, but is not limited to them. Examples of its implementation are provided for a more detailed disclosure of the invention.

[0046] Example 1.

[0047] To purify water, an installation was mounted according to the diagram shown in Fig. 2. The installation included: an ozone generator (1), an ozone supply line (2), a water supply pump (3), a water supply line (4), an ejector for mixing water with ozone (5), a static mixer (6), a pressure flotation tank (7), an oil product storage tank (9), a sedimentation tank for settling sediment (10), a disc filtration unit (I), a tangential microfiltration circuit (12), and a container for collecting purified water (13).

[0048] The purification of formation water was carried out with a manganese content of 15 mg / l, iron 75 mg / l and oil products 50 mg / l.

[0049] Water purification was carried out as follows.

[0050] A stream of water for purification was supplied through the water supply line (4) to the ejector (5), where ozone from the ozone generator (1) was supplied through the ozone supply line (2), the ozone was dosed, and from the ejector the stream of water with ozone was supplied to the static mixer (6), from where the water was supplied to the pressure flotator (7).

[0051] Before feeding water into the flotation tank (7), a flocculant was mixed into it.

[0052] The flocculant was a 0.2% aqueous solution of polyacrylamide and was dosed at a rate of 1-2 liters per 1 m 3 water.

[0053] The flotation unit operated using a recirculation system that recirculated a portion of the purified water, saturated with air. Water was supplied under pressure by a pump (flow rate was controlled by a flow meter). When the pressure was released, dissolved air was released from the water as microbubbles. The microbubbles adhered to contaminant particles, including oil products, and lifted them to the upper part of the flotation chamber (the flotation zone), forming a froth layer. Purified water from the flotation zone entered the separation zone, located at the bottom of the flotation chamber and equipped with thin-layer elements. In this section, the final separation of dissolved air occurred; the presence of thin-layer elements accelerated the ascent of microbubbles. Upon exiting the thin-layer elements, the purified water flow reversed direction and entered the purified water chamber, from where it was discharged by gravity. A portion of the purified water was fed by a circulation pump to the saturator, where it was saturated with air.Air was introduced into the water through the ejector of the circulation pump. From the saturator, air-saturated water was fed to the inlet of the flotation chamber. Flotopene, containing oil products and suspended solids, was removed from the water surface by an electrically driven scraper mechanism into a receiving tray, from which it was discharged by gravity. The resulting sediment collected in the lower conical section of the flotation chamber and was periodically discharged from the unit.

[0054] As a result of flotation, the separation of oil products occurred, they were sent to the oil product storage tank (9), from the pressure flotation tank (7) the water entered the sedimentation tank (10), from where it entered the disc filtration unit (11), which was made in the form of two disc filters installed in series with a filtration rating of 50 (first filter) and 20 (last filter) µm.

[0055] As the disc filters became clogged, they were backwashed. Backwashing was performed only when a pressure differential of more than 2 kgf / cm was achieved. 2 .

[0056] From the filtration unit (11), water entered the tangential microfiltration circuit (12), where permeate was obtained, which was sent to a container for collecting purified water (13) and concentrate was obtained, which was sent to a settling tank (10).

[0057] Membranes with a filtration rating of 0.2 µm were used for the cross-flow tangential filtration stage. Air backwashing was periodically performed to clean the membranes to restore performance. Periodically, as the air backwash efficiency decreased, chemical backwashing with hydrochloric acid was performed.

[0058] Ozone consumption was controlled at the minimum level necessary for effective oxidation of impurities. Filter cleaning was accomplished without disassembling or removing them.

[0059] The purified water contained no more than 2.5 mg / l of iron and manganese and 0.05 mg / l of petroleum products.

[0060] Example 2.

[0061] Water purification was carried out in a manner similar to Example 1, with the difference that the installation additionally included a source of flocculant (8), connected to the water supply line to the pressure flotator (7) and connected to the pressure flotator (7), which provided the possibility of automated introduction of flocculant during the purification process.

[0062] The installation diagram is shown in Fig.3.

[0063] Flocculant was mixed into the water flow entering the pressure flotator (7) from the flocculant source (8), and flocculant was also fed from the flocculant source (8) directly into the pressure flotator (7).

[0064] Example 3.

[0065] Water purification was carried out similarly to Example 2, with the difference that excess ozone was additionally removed from the upper part of the pressure flotator (7) into a thermal catalytic ozone destructor, where the ozone was utilized.

[0066] Example 4.

[0067] Water purification was carried out similarly to Example 2, with the difference that excess ozone was additionally removed from the upper part of the sedimentation tank (10) into a thermal catalytic ozone destructor, where the ozone was utilized.

[0068] Example 5.

[0069] Water purification was carried out similarly to Example 2, with the difference that the water entering the purification had a pH of 4; before purification, the pH of the water was adjusted by introducing a 10% sodium hydroxide solution through a mixer to ensure a pH of 5 units, which ensured effective ozonation and flotation.

[0070] Example 6.

[0071] Water purification was carried out in a similar manner to Example 2, with the difference that the water supplied for purification was a natural calcium chloride brine.

[0072] Sources of information used.

[0073] 1. Patent US4780215A. IPC C02F 1 / 78. Water purification device / Russell L. Carlson / Application dated 06 / 08 / 1987. Published 10 / 25 / 1988. 2. Patent RU2105729C1. C02F 1 / 64. Method for purifying groundwater from iron and manganese / Fomin S.N., Antonov L.A. Application dated 10 / 03 / 1996. Published 02 / 27 / 1998.

[0074] 3. Patent RU2624643C2. C02F 9 / 00, C02F 1 / 00, C02F 1 / 28, C02F 1 / 32, C02F 1 / 36, C02F 1 / 463, C02F 1 / 465, C02F 1 / 467, C02F 1 / 52, C02F 1 / 78, BOID 21 / 00. Method and device for electrochemical treatment of industrial wastewater and drinking water / Oreshchanin V., Mikulich N., Petlyak D. Application dated 27.03.2013. Published 25.04.2017.

[0075] 4. Patent KR100538347B 1. IPC C02F1 / 78. Wastewater treatment apparatus / Chon Ho-Sam. Application dated 12.12.2003. Published 17.06.2005.

[0076] 5. Patent CN214031993U. IPC C02F 103 / 20. Integrated wastewater treatment system for rock / Wu Yiqun, Zhang Bin. Application dated 04.11.2020. Published 24.08.2021.

[0077] 6. Patent RU2811343C1. IPC C02F 1 / 64, C02F 1 / 78, BOID 61 / 14. Method for reagent-free water purification from iron and manganese and device for its implementation / Bogatyrev Svyatoslav Igorevich, Shkabura Aleksey Petrovich, Yarutkin Evgeny Nikolaevich, Lazarev Dmitry Aleksandrovich, Stepankin Aleksandr Sergeevich, Ignatov Anton Olegovich. Application dated 07.11.2023. Published 11.01.2024.

Claims

CLAUSES OF THE INVENTION 1. A method for purifying water from iron, manganese and petroleum products, including treating water with ozone by mixing water and ozone in an ejector, mixing water and ozone in a static mixer, directing water into a settling tank for sedimentation, filtering water using at least one disc filter with a filtration rating of at least 20 μm and tangential microfiltration of water using the cross-flow method, characterized in that after mixing water and ozone in a static mixer and before directing water into a settling tank for sedimentation, a flocculant is added to the water and pressure flotation is carried out.

2. The method according to paragraph 1, characterized in that before treating the water with ozone, it is treated with an alkali solution to ensure that the pH of the water is at least 5 units.

3. A device for implementing the method according to claim 1, comprising an ozone generator, an ozone supply line, a water supply pump, a water supply line, an ejector for mixing water with ozone, a static mixer located after the ejector, a settling tank for sedimentation, at least one disc filter with a filtration rating of at least 20 μm and at least one tangential microfiltration filter installed after the disc filter and providing tangential microfiltration using the cross-flow method, characterized in that it further comprises a pressure flotation device located after the static mixer and before the settling tank for sedimentation.

4. The device according to paragraph 3, characterized in that after the static mixer and before the pressure flotation device, a flocculant supply line is installed, which ensures the supply of flocculant into the water flow.

5. The device according to paragraph 3, characterized in that the pressure flotation device has a flocculant supply line that ensures the supply of flocculant to the pressure flotation device.

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