RU1834851C - Method for ionic exchanging denitrification of water - Google Patents

Abstract

Usage: in the treatment of water by ion exchange and can be used in the practice of household-drinking water supply. SUBSTANCE: water treatment is carried out in three stages: on the first H-cationization prior to the passage of bicarbonates, on the second Na-CI or Cl-ionization prior to the passage of sulfates, on the third Cl-anionation prior to the passage of nitrates, while the spent regeneration solutions of the 1st and the 2nd stage is treated with the release of calcium sulfate and sent to the preparation of a regeneration solution. The regeneration of anion exchange resin of the 3rd-2nd stage of water treatment is carried out with a saturated solution of sodium chloride with separation of the spent regeneration solution. The method allows to reduce the consumption of reagents for water treatment from 3.24 kg / m to 245 g / m3, 1 zpf-l. SL C

Description

The invention relates to the treatment of water by ion exchange and can "be used in the practice of domestic drinking water supply.

The aim of the invention is to reduce the consumption of reagents, and the cost of the process due to the discharge of mineralized wastewater.

This goal is achieved by the fact that in the known method of ion-exchange water denitrification, including C1-anionization, the treatment is carried out in three stages: on the first H-cationization to the passage of a bicarbonates, on the second - Na-CI or Opposition to the passage of sulfates, on the

the third - by Cl-anionization for the passage of nitrates, while the spent regeneration solutions of the 1st and 2nd stages are treated with the release of calcium sulfate and sent to the preparation of the regeneration solution. The regeneration of anion exchange resin of the 3rd stage of water treatment is carried out with a saturated solution of sodium chloride with separation of the spent regeneration solution. 8 related fields of science and technology of the known technical solution with signs of water treatment in three stages: on the first H-cationization to the passage of bicarbonates, on the second Na-CI or Cl-ionization to the passage of sulfates,

with

b

00

ate

with

third, by Cl-anionization to a nitrate slip during processing of the spent regeneration solution of the 1st and 2nd stages with the release of calcium sulfate with subsequent use to prepare the regeneration solution.

The method is carried out as follows.

Source water is treated in three stages. In the first stage, water is filtered on an H-cation exchange filter until the bicarbonates break through. Calcium and magnesium bicarbonate are removed from this water. Regeneration of the H-cation filter is carried out with sulfuric acid. The spent regeneration solution containing CaSO-q and MgSCM is treated with lime with the release of calcium sulfate in solid form:

MaS04 + Ca (OH) 2 CaSCM + Mg (OH) 2l. When excess sulfuric acid is contained in the solution, it is neutralized with the release of calcium sulfate: H2S04 + Ca (OH) 2 CaS04 + 2H20 .. Under various technological options, as well as depending on the quality of the initial water, the treatment of the spent regeneration solution can be carried out without liming, t .e. without removing Mg2 + ions, by precipitation of excess calcium sulfate.

The post-treatment solution is used to prepare a sulfuric acid regeneration solution.

In the second stage of the treatment, water is passed through a Na-Cl or Ct-ionite filter until the sulfate flows through. In this case, sulfates are removed from the treated water (in case of No-Cl ionization, also Ca + and Md +). Preferably, chlorides and nitrates will be contained in the treated water at the filter outlet. The spent regeneration solution of the Ci-anion exchange filter containing Na2S04 and NaCI is treated with calcium chloride with the release of calcium sulfate:

Na2S04 + CaCIs i CaSO / i + 2NaCI. When using a Na-Cl-ion exchanger filter, the spent ions will contain: Ca2 +. Mg2 Na +. SO / j, SG. This solution is treated with lime with the release of calcium sulfate and magnesium hydroxide:

 MgSOo + Ca (OH) 2 CaS04 $ + Mg (OH) 2i

After treatment, the solutions are fortified with technical table salt and used for subsequent filter regenerations.

In the third stage of the treatment, water containing predominantly chloride l

nitrates are passed through a C1-anion exchange filter until the nitrates slip. Preferably, chlorides will be contained in the treated water. Earned filter

regenerate with saturated sodium chloride solution. During the regeneration, the spent regeneration solution, which contains sodium chloride and sodium nitrate, is separated. Moreover, the above conditions of regeneration of the filter provide high concentrations of these components in the spent regeneration solution, which facilitates its subsequent disposal. Disposal

5 solutions are possible in 2 versions: use in agriculture as a liquid nitrogen fertilizer or evaporation with separation of salts. In the latter case, sodium chloride is returned to the regeneration of the filters, and crystalline sodium nitrate is sold to consumers.

Example 1. Water of the following quality, mEq / l: Ca 4.0, Md21 0.57, Na + 0.5, HCO3 1.8, is fed to the treatment.

5 S042 - 0.94, CU 0.8, Moh 1.53.

This water is treated in three stages. In the first stage, water is passed through an H-cation exchange filter until the bicarbonates in the average filtrate reach 0.2 mEq / L.

0 In this case, the Ca2 content in the filtrate is reduced to 2.4 mEq / L. The selected regeneration solution of the H-cation exchange filter is treated by stirring and settling (with the release of crystalline calcium sulfate, after which this solution is used to prepare the regeneration solution of sulfuric acid. In the second stage, water is passed through the Cl-anion exchange filter until the content of anions in the treated the water will be the following, mEq / l: HCO3 0.2, S042 traces, SG 1.74, MoH 1.53, The spent regeneration solution of the Cl-anion exchange filter is treated

5 with calcium chloride with the release of calcium sulfate. After treatment, a solution containing predominantly sodium chloride is used for subsequent filter regenerations.

0 In the third stage, water is passed through a Cl-anion exchange filter operating in the nitrate removal mode. The filter is turned off for regeneration when the nitrate concentration in the averaged

5 filtrate 0.45 mEq / L, with a chloride content of 2.82 mEq / L with virtually no other anions.

The treated water meets the requirements of GOST 2874-82 for drinking water. According to the specified state standard specification

nitrates in drinking water should not exceed 45 mg / l (0.726 mEq / l), chlorides - 350 mg / l (9.86 mEq / l}.

The filter of the third stage of water treatment is regenerated with saturated sodium chloride solution. The separated spent regeneration solution contains 80 g / L sodium nitrate and 100 g / L sodium chloride. This solution was evaporated to separate crystalline salts. Sodium chloride is returned to the regeneration of the filters, and sodium nitrate is sold as a commercial reagent.

Example 2. The quality of the source water and the implementation of its treatment - see example 1 with the difference that in the second stage the water is passed not through a Cl-anion exchange resin, but through a Na-CI-ionite filter loaded with a mixture of highly basic anion exchange resin and strongly acid cation No. a. After the second stage of treatment, D-a: contains ions, mEq / L: Ca2 + 1.46, Md2 + - 0.57, Na + 0.5, HCO3 0.2, S042 traces, SG 1.74, N03 1.53.

The filter of the 2nd stage of water treatment is regenerated with a NaCI solution. The spent regeneration solution is treated by stirring and settling (without adding reagents) with the release of calcium sulfate, after which it is further fortified with technical table salt and used for subsequent regenerations.

Example 3. The quality of the source water, mEq / l: Ca2 - 1.0, Md2 + 2.0, Na 2.07, HCO3 1.8, 0.94, SG 0.8, Moh 1.53.

Water treatment technologies - see example 2 with the difference that lime is dosed into the spent regeneration solution of H-cation exchange resin and Na-CI-ionite filter (stages 1 and 2 of water treatment) based on magnesium deposition.

The quality of the filtrate after the 1st processing step (after the H-cation exchange filter), mEq / L: Ca2 + 0.5, Md2 + - 0.9, Na + 2.07, HCO3 0.2, S042 h 0.94. SG 0.8, N03 1.53.

Water quality after the 2nd stage of treatment (after Na-CI-ionite filter), mg-Sq / L: Ca24 0.2, Md2 + 0.26, Na + 2.07, HCO3 0.50 / trace, SG 1.74 , Moh 1.53.

After the 3rd processing step (after the CI-anion exchange filter), the nitrate content in water decreases to 0.45 mEq / l, and

the amount of chloride increases to 2.82

MGtekv / L.

Reagent consumption for water treatment stoichiometric: 1.6 g-equiv / m

5 (78.4 g / m3), CaO 100% - 1.74 g-eke / m3 (48.7 g / m3), NaCl 2.02 g-equiv / m3 (118.2 g / m3). Total reagent consumption - 245.3 g / m

According to a known method adopted for the prototype for the regeneration of anion exchange resin

0 first, a 100 g / L NaCI solution in an amount of 5 m3 / m3 is used, then the same amount of solution containing 85.9 g / L N32SO4 and 14.1 g / L NOHCO3 is used. Total consumption of reagents for regeneration - 1000 kg

5 on 1 m of loading. With an anion exchange capacity of 327.2 g-eq / m, the specific consumption of salts for regeneration will be 3 kg / m. With a decrease in the nitrate content in water from 1.53 to 0.45 mEq / L, the consumption of reagents is 3.24 kg per 1 m3 of treated water.

Thus, the proposed method allows reducing the consumption of reagents for water treatment from 3.24 kg / m to 245.3 g / m and eliminating the discharge of mineralized wastewater.

Claims (2)

1. A method of ion-exchange denitrification of water, including passing it through a Cl-anion exchange filter to a breakthrough of nitrate ions, followed by regeneration of the filter with a solution of sodium chloride, characterized in that, in order to reduce the consumption of reagents and reduce the cost of the process by reducing the discharge of mineralized wastewater, water is preliminarily passed through an H-cation exchange filter until the stiffness ions pass into the filtrate, then through Na-CI or Cl-ion exchange filter until the sulfate ions escape, the spent regeneration solution of N-ka a thionate filter containing calcium and magnesium sulfate and a spent Na-CI or Cl-ionite filter solution containing sodium sulfate and sodium chloride, after the separation of calcium sulfate, they are sent to regenerate the filters. 2. The method according to p. 1, characterized in that the spent regeneration The 0 Cl-anion exchange filter solution was evaporated to give the sodium nitrate salt as a commercial product and the sodium chloride solution used to regenerate the filter.