RU2330815C2 - Method of purification of sewage and natural waters from sulfate ions of divalent iron - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: purification method involves clarification and normalisation of hydrogen rate, when source water with concentration of divalent iron sulfate ions under 100 mg/l is aerated at redundant pressure of 1-4 atmospheres for 1-5 minutes, at that the water is fed to aeration in the form of wet air pulp. After the aeration the water is sent to clarification.

EFFECT: elimination of reagent preparation, consumption and neutralisation costs; streamlining of technology and reduction of costs for obtaining precipitation with improved structure and smaller volume, and of water treatment before discharge to the fishery pools due to the absence of a reagent.

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Description

The invention relates to a method for treating wastewater and natural waters and can be used in various industries, including mining, chemical and engineering.

A known method of iron removal (purification) of natural and wastewater from iron using aeration of water in atmospheric conditions, if iron ions are presented in bicarbonate form, which is typical for most groundwater [1]. However, the known method of aeration does not provide water purification from iron ions, if they are presented in sulfate form. This form of iron can be removed from both groundwater and surface water at present only by the reagent method using strong alkalis.

The closest method of the same purpose to the claimed combination of features is a method of purification from sulfate ferrous ions by precipitation into the solid phase in the form of hydroxide at an increase in pH to 9.7 using alkaline reagents [2].

The cheapest highly alkaline reagent is lime, the use of which is widespread and recommended by a number of regulatory documents for use in water treatment technology [3, 4].

The disadvantage of this method is the formation of a precipitate of an amorphous structure, which causes a slow rate of clarification of neutralized water and compaction of the sediment. As well as the need to increase the land area for storage (or burial) of this bulk sediment, which leads to increased costs and inhibits the widespread adoption of this technology, especially for large volumes of highly contaminated wastewater, where sulfate-containing iron ions are mainly present in divalent form (for example, mine water flowing from waste mines).

The objective of the present invention is to reduce costs and provide deep purification of water with an iron content of not more than 100 mg / dm ³ from sulfate ferrous ions, regulated for the discharge of water into water objects of fishery purposes (MPC ≤0.005 mg / dm ³ ), by a non-reagent method.

The technical result is the exclusion of the preparation and dosing of an alkaline reagent, a decrease in the volume of sludge formed and the provision of wastewater and natural water purification from ions of ferrous sulfate with an iron content of not more than 100 mg / dm ³ to discharge water into fishery water bodies without using a reagent.

The above technical result is achieved in that the wastewater and natural waters from ions of ferrous sulfate, including clarification and normalization of the hydrogen index, according to the invention with a concentration of ferrous sulfate ions of not more than 100 mg / DM ³ aerate for 1-5 min at overpressure while it is served for aeration in the form of a water-air pulp, and after aeration it is sent for clarification.

The use of excess pressure in the process of aeration of water and its supply in the form of a water-air pulp provides an increase in the solubility of air compared with atmospheric conditions and, accordingly, an increase in the solubility of the oxygen contained in it, which accelerates the oxidation of ferrous to ferric iron, which allows the treatment of waste and natural waters sulfate ions from ferrous iron with an iron content of not more than 100 mg / dm ³ for water discharge into water fishery n values without the use of the reagent.

Thus, the water supply for purification from sulfate ferrous ions with an iron content of not more than 100 mg / dm ³ in the form of a water-air pulp at excess pressure with subsequent clarification eliminates the cost of preparation and consumption of the reagent, the neutralization process, simplify the technology and reduce costs on the process of sludge formation with improved structure and smaller volume and to provide purification for discharge of water into fishery water bodies without the use of a reagent.

As a result, a compact precipitate is formed instead of a larger amorphous precipitate, characteristic of water purification by known methods using alkaline reagents, including lime. At the same time, water purification from sulfate ferrous iron, oxidized to Fe ³⁺ ions, is achieved at pH≤4.1-5.0.

In the patent and scientific and technical literature unknown technical solutions containing features similar to those claimed, therefore, the proposal meets the criterion of "novelty." Also, for the first time on the basis of the developed method, the purification of wastewater and natural waters from sulfate ferrous ions with an iron ion content of not more than 100 mg / dm ^{3 was} determined, which provides deep purification from ferrous sulfate ions regulated for discharge of water into fishery water bodies without using the reagent method , i.e. The claimed technical solution meets the criterion of "inventive step".

The proposed method to obtain the above technical result is as follows.

Wastewater is pumped into the inlet of which air is sucked in through the ejector, is supplied in the form of a water-air pulp to the saturator and aeration is carried out at an overpressure, for example, for 1-5 minutes. Then the water is sent to a sump or sludge collector for the subsequent completion of purification from dissolved iron, normalization of the hydrogen index and clarification (contact clarification)

In the contact clarifier, the oxidation of ferrous iron is completed due to the increased content of dissolved oxygen with simultaneous normalization of pH due to precipitation of Fe (OH) ₃ and purification of water from suspended solids.

Verification of the proposed method for treating wastewater from sulfate ferrous ions was carried out on natural mine water with a change in overpressure.

Example 1. Mine water with a pH of 5.03 and a concentration of Fe ^{2+ ions of} 200 mg / dm ³ was supplied by a pump, into which air was sucked into the saturator through an ejector, where the air-air mixture was subjected to aeration without using an alkaline reagent.

Aeration was carried out for five minutes at a pressure of 4 atm and continuous bleeding of excess air. After the specified time, the test water sample was unloaded and divided into two parts: the first one was immediately analyzed for determination of Fe ^{2+ ions} and the pH value, the second one was sent for clarification, after which after a predetermined time interval (after 1 hour, 17 hours, 48 hours, 72 hours) samples were taken to control Fe ^{2+ ions} and pH.

The analysis results showed that during aeration in the saturator, the concentration of Fe ^{2+ ions} decreased to 167 mg / dm ³ , with further contact in the clarifier for about 1 hour, the concentration of Fe ²⁺ decreased by about half, and the subsequent clarification time for three days, the residual concentration of ferrous ion was 27.9 mg / dm ³ at pH = 5.25 (table, series of experiments 1), i.e. for this runoff composition without an alkaline reagent, purification is not achieved in terms of pH and residual concentration of Fe ²⁺ to discharge water into fishery water bodies.

Example 2. Mine water with pH = 5.03 and a concentration of Fe ^{2+ ions} = 100 mg / dm ³ was supplied by a pump, into which air was sucked into the saturator through an ejector, where it was aerated into the air mixture without using an alkaline reagent, and a pressure of 4 atm was maintained during aeration for 5 min (table, series of experiments 2).

Chemical analysis of samples taken after the saturator and further clarification at the time intervals indicated in the table showed that the concentration of iron ions during aeration in the saturator decreases to 150 mg / dm ³ . With subsequent clarification of the water for 48 hours, ferrous iron is not present in the treated water sample. At the same time, the pH increased to 6.5, which allows water to be discharged into water bodies for fishery purposes.

Example 3. Mine water with a pH of 5.03 and a concentration of Fe ^{2+ ions} = 80 mg / dm ³ was supplied by a pump, into which air was sucked into the saturator through an ejector, and the air-water mixture was subjected to aeration without using an alkaline reagent, at a pressure of 1 atm with aeration for one minute. After such treatment and clarification for 72 hours, there are no ferrous ions in the purified water, the pH value is 7.46 (table, series of experiments 3), which allows the discharge of purified water into fishery water bodies.

The proposed technology will reduce the cost of neutralization, as well as subsequent processes of clarification of water, compaction and storage of sludge in sludge collectors (or settling ponds) in connection with the formation of a denser and more compact sludge compared to the sludge formed during water treatment using lime.

The use of the proposed technology is especially favorable for the purification of large volumes of mine water pouring out from flooded waste mines, where the main polluting component is ferrous ions, represented by sulfate salts.

Table
Indicators of wastewater treatment from sulfate ferrous ions using atmospheric oxygen at excess pressure Experience Series No. Source water Processing options The cleaning performance after processing water under pressure with subsequent clarification for, hour. t ° C pH Fe ²⁺ mg / dm ³ pressure, ati processing time, min 0 one 17 48 72 pH Fe ²⁺ mg / dm ³ pH Fe ² , mg / dm ³ pH Fe ² , mg / dm ³ pH Fe ²⁺ , mg / dm ³ pH Fe ² , mg / dm ³ one 19.5 5.03 200 four 5 5,4 167 - 97.7 5.46 50,2 - 33.5 5.25 27.9 2 19.5 5.03 one hundred four 5 5.8 81 6 70.0 - - 6.5 0 - - 3 18.0 5.03 80 one one 5.73 72 - - 5.85 67.0 - 6.0 7.46 0

Information sources

1. L.A. Kulsky, P.P. Strokach Technology for the purification of natural waters. - Kiev: Vichy School, 1986, p. 211.

2. Yu.B. Lurie Handbook of analytical chemistry. - M., Chemistry, M. 1971, p. 248

3. Building Norm and Rules, Part II, Chapter 32 (SNiP-32-74)

4. The main provisions for the design of facilities for the treatment of acid mine water, approved by the Ministry of Coal Industry and agreed with the Ministry of CCC and the Ministry of Fisheries of the USSR, 1978

Claims (1)

A method of purifying wastewater and natural waters from sulfate ferrous iron, including clarification and normalization of the hydrogen index, characterized in that water with a concentration of sulfate ferrous ions of not more than 100 mg / dm ^{3 is} aerated at a pressure of 1-4 atm for 1-5 minutes while it is served for aeration in the form of a water-air pulp and after aeration it is sent for clarification.