RU2181109C2 - Underground water deferrization method - Google Patents

Abstract

FIELD: water treating. SUBSTANCE: method is based on passing water through sprinkler onto charge bed, bringing it into contact with water-air mixture fed in countercurrent mode by circulation pomp through ejector, and blowing off by air gases dissolved in initial water, which is simultaneously saturated with air. Volume of water-air mixture is 2-3- fold superior to that of water stream to under treatment. EFFECT: intensified iron oxidation process, increased productivity, and reduced power consumption. 3 cl, 1 dwg

Description

 The invention relates to methods for purification of groundwater from iron and can be used in water treatment for drinking and industrial water supply.

 There is a method of purifying water from iron by deep aeration before it enters the contact tank, oxidizing oxygen of soluble 2-valence iron to 3-valence iron, and filtering the precipitate of iron hydroxide formed on clarification filters [1].

 The disadvantages of this method are the low speed of the iron oxidation process, especially in the presence of dissolved carbon dioxide, the need to use large-sized aeration plants for its blowing, and high energy costs.

 Closest to the proposed invention is a method of purifying water from iron, including evacuating the water, mixing it with air at atmospheric pressure, processing in a contact tank, filtering with constant circulation of part of the water for mixing with dispersed air bubbles at the design pressure of the water-air mixture and saturation time [ 2].

The disadvantages of this method are: the process of water purification under pressure of a water-air mixture, because the radius of dispersed air bubbles should be minimal, the need to have a large specific surface and a sufficient phase contact time, inefficiency of removal of dissolved gases (CO ₂ , H ₂ S) from water in the vacuum zone of the confuser. In the above example, with a bubble diameter of 1 mm, the phase contact surface should be about 300 m ² / m ^{3 of} water. Using an ejector to saturate water with air even with a dispersant does not give such a contact surface, and an increase in the pressure of the air-water mixture during ejection of atmospheric air without a compressor cannot exceed 1.5 ata. Additional, capital and operating costs for the compressor are required.

 The technical result of the invention is to intensify the process of oxidation of iron, increase productivity, simplify the scheme of water purification, reduce energy consumption by 1.5 times and the simplicity of the process control scheme.

 The technical result of this method is achieved by increasing the specific surface contact of the phases achieved on a special nozzle with a large geometric surface, increasing the oxidation rate, eliminating the confuser from the circuit to create a vacuum zone and an air dispersant.

 The essence of the method of water purification from iron consists in the passage of the source water through the sprayer to the nozzle, its contact with the air-water mixture supplied by the countercurrent circulation pump through the ejector, and air blowing of the gases dissolved in the water to the nozzle while it is saturated with oxygen.

 The drawing shows a diagram of an installation for implementing the proposed method for purifying water from iron. The installation consists of a column 1 with a nozzle 2 and a sprayer 3, a tank 4 with water, a circulation circuit including an ejector 5, valves 6 and 7, a pump 8, and a filter 9.

 The method is as follows. The source water through a sprinkler 3 is fed into the column 1 on the layer of the nozzle 2 with a large specific surface area. In countercurrent source water, air enters the column 1 through the ejector 5 with circulating water supplied by the pump 8 from the reservoir 4. Changing the circulation flow of water, representing a water-air mixture, the volume of which is equal to or 2-3 times the volume of the flow of the source water, allows you to set the desired ratio of water-air ", set depending on the concentration of iron, and the contact time of the phases. The air released during separation from the circulation stream interacts with the source water on the surface of the upper layers of the nozzle 2 and displaces the gases dissolved in it, which prevent the oxidation of iron (carbon dioxide, hydrogen sulfide, etc.), while saturating the water with oxygen. The oxidation of 1 mg of ferrous iron requires 0.7 mg of oxygen [1]. On the surface of the middle and lower layers of nozzle 2, ferrous iron is intensively oxidized to insoluble ferric iron, which enters reservoir 4 with a stream of water, from where water is returned to column 1 by pump 8. A portion of its flow equal to the feed water stream is supplied to the filter through valve 7 9 onwards to the consumer.

With various types of nozzles, the specific contact surface of the phases has a different value. For example, when loading the nozzle from Rashig ceramic rings (15 • 2 mm), the specific contact surface of the phases Fud = 300 m ² / m ³ necessary for effective dissolution of air and blowing of gases dissolved in water is created. When loading with a spiral-wire nozzle, the specific surface of which reaches 2200 m ² / m ³ , the volume of the contact column and its height respectively decrease, and the necessary saturation of water with air is achieved at a contact part height of 0.5-2 m. When gas is absorbed by a liquid, the main mass transfer equation:
M = K • F • ΔC,
where M is the mass of gas (air) absorbed by the liquid (water) per unit time, kg / h;
K is the absorption coefficient, m / h;
F is the surface area of the contact phase, m ³ ;
ΔC- is the driving force of the absorption process, expressed by the difference in gas concentrations in the liquid at its full saturation, and the current value, kg / m ³ .

From the equation it follows that at constant K and ΔC the amount of air dissolved per unit time is directly proportional to the size of the phase contact surface. When changing the height of the contact part with a spiral-wire nozzle from 0.5 to 2 m, the contact surface F in the column with a diameter of 300 mm varies from 78 to 310 m ² (F = Fud • Vn = 2200 m ² / m ³ • 0.035 m ³ = 77.7 m ² ). To ensure such a surface on Rashig ceramic rings, the column height should be from 3.5 to 14 m, respectively, and in the claimed solution using a spiral-wire nozzle - less than 1 meter.

 Thus, the invention is new, because it has an inventive step because it does not explicitly follow from the prior art for a specialist.

 The technical result of the present invention is to intensify the process of oxidation of iron, increasing the throughput of the column, simplifying the scheme of water purification and process control.

Sources of information
1. Nikoladze G.I. Iron removal from natural and circulating waters. M, Stroyizdat, 1978, p.26.

 2. RF patent 2119892, M. Cl. 6 C 02 F 1/64, 1993 - prototype.

Claims (3)

 1. The method of purification of groundwater from iron, including mixing them with air at atmospheric pressure, processing in a contact tank, filtering with constant selection of water for mixing with dispersed air at a certain pressure of the water-air mixture and saturation time and circulation through a contact tank, characterized in that the source water is contacted on a nozzle with a large specific surface with a water-air mixture supplied to the mixture by a circulation pump through an ejector, the volume of which is equal to or 2-3 times greater a volume flow of water supplied to the purification.  2. The method according to p. 1, characterized in that the gas dissolved in the source water is removed by countercurrent contact with the air released from the circulation stream on the surface of the upper layers of the spiral wire nozzle with a large specific surface.  3. The method according to p. 1, characterized in that the saturation of water with air, depending on the iron content in it, occurs in a packed or plate column at a contact part height of 0.5-2 m.