RU2147014C1 - Drinking water purification process - Google Patents

Abstract

FIELD: water treatment. SUBSTANCE: in order to remove manganese from drinking water, sodium hypochlorite is added to water prior to be passed through filter bed of sorbent (manganese oxide-coated sand grains), which is further regenerated with higher-concentration hypochlorite solutions. Dose of chlorinating agent is chosen such as to provide sanitary level of active chlorine in treated drinking water. EFFECT: prolonged operation time of sorption filter and avoided utilization of permanganate in the sorbent regeneration stage. 1 tbl, 5 ex

Description

 The invention relates to the field of water treatment, namely the purification of drinking water from manganese compounds.

A known method of purification of drinking water by filtering through a layer of "black sand" or an oxidizing mineral sorbent (COM), which is sand, the grains of which are coated with a film of manganese dioxide, catalytically accelerating the oxidation of manganese compounds dissolved in water to insoluble oxides Mn ⁺³ and Mn ⁺⁴ , deposited on COM. In this case, the valency of manganese in the surface film on sand grains decreases and the catalytic effect ceases. The layer thus worked out can be regenerated by washing with a KMnO ₄ solution.

 After the sorbent layer, the purified water is usually disinfected by introducing chlorine or sodium hypochlorite for supply to the water supply network.

 The disadvantage of this method is the short duration of the sorbent, the use of scarce and expensive salt of manganese during regeneration, pollution of the waste water during registration with manganese compounds.

 The objective of the invention is to increase the duration of water purification from manganese compounds with a filter loaded with such a sorbent, as well as the elimination of environmental pollution by manganese compounds that make up the regeneration solution.

 This problem is solved by the fact that a chlorinating agent, mainly sodium hypochlorite, is introduced into the purified water before the layer of COM-1, and the regeneration of the sorbent after the layer is depleted is also carried out with sodium hypochlorite solution.

 Sodium hypochlorite increases the sorption-catalytic ability of COM-1 at a concentration close to that used for chlorination of water (1-2 mg / l). With an increase in the concentration of hypochlorite to 10-15 g / l (calculated as active chlorine), its oxidative effect increases so that its catalytic properties return to the depleted layer of sorbent treated with such water, and regeneration occurs.

 Example 1

Under laboratory conditions, tap water was passed through a layer of COM-1 in a glass tube into which manganese chloride was added. Its concentration in water to reduce the duration of the experiment was established 5 mg / l (calculated on Mn ²⁺ ), i.e. higher than occurs in some underground sources of drinking water (0.2 - 1.5 mg / l) Mn ²⁺ ); part of the tests - at 1 mg / l Mn ²⁺ . The concentration of sodium hypochlorite added to the purified water is 4-5 mg / l (at a concentration of Mn ²⁺ 5 mg / l) and 1.5 - 2 mg / l (at a concentration of Mn ²⁺ 1 mg / l). We measured the time until the appearance of a Mn ²⁺ concentration behind the sorbent layer equal to 0.1 mg / L (sanitary norm).

 Part of the experiments for comparison was carried out without the addition of sodium hypochlorite.

The diameter of the sorbent layer is 2 cm
Layer height - 20 cm
Water transmission speed - 5 m / h
The cleaning time at C _o = 5 mg / L Mn ²⁺ was with the addition of hypochlorite - 64 hours, without adding - 12 hours. At an initial concentration of C _o = 1 mg / L Mn ^{2+, the} cleaning time without adding sodium hypochlorite is 42 hours, and with the addition of manganese was not detected for 120 hours, the experiment was terminated without a “slip”. The test results are shown in the table.

 Example 2

Sample COM-1, depleted after water purification for 64 hours, is poured with a solution of sodium hypochlorite concentration of 10-15 g / L. To accelerate the process, the solution was heated to 40 ^o C. After 2 hours, the solution was poured, the sorbent was poured with a new portion for 2 hours. Then the COM-1 layer was washed with water to a neutral medium and tested under the conditions of Example 1. The time of the protective action of the layer was practically the same as in Example 1. The test results are shown in the table.

 Example 3

 Obtained in Example 2, the sorbent layer depleted after testing was repeatedly regenerated by the above method and used to purify water under the same conditions. The test results are shown in the table.

 Example 4

 Obtained in example 3, the depleted layer of the sorbent was regenerated a third time in the above manner and was used to purify water under the same conditions. The test results are shown in the table.

 Example 5

 The tests were carried out in the production conditions of a water station at a bench installation.

 Purified water with an average manganese content of 0.35 mg / L was passed through a layer of COM-1 with a diameter of 7 cm and a height of 35 cm at a speed of 4-5 m / h. With an accuracy of 0.05 mg / L, manganese was not detected in purified water. After 1200 hours, traces of Mn with a concentration of less than 0.1 mg / L were detected (onset). After that, sodium hypochlorite was added to water until it was 1.5 mg / L in water. Traces of manganese disappeared. Before the "slip", the layer worked for another 1000 hours, i.e. the total working time was 2200 hours. The results of all the tests described in the example are shown in the table.

 Thus, with the addition of sodium hypochlorite in drinking water before the COM-1 layer, the duration of the layer increases many times, and the addition of the same substance in high concentration during filter washing allows the sorbent layer to be regenerated many times.

 This creates the opportunity not only for the long-term use of a relatively expensive sorbent, but also for obtaining new technical solutions, for example, using the SOM-1 sorbent in shorter layers, which will allow, for example, loading a sorbent layer together with a sand layer into quartz filters, which are available on almost all water treatment plants.

Claims (1)

 A method of purifying drinking water from manganese compounds, including treating water by filtration through a layer of oxidizing sorbent with its subsequent regeneration, characterized in that the water is chlorinated, mainly sodium hypochlorite, before it is fed to the filter and the dose of the chlorinating agent is set so as to ensure the content of active chlorine in purified water at the level of sanitary standards, and the layer of sorbent after its depletion is regenerated with sodium hypochlorite solution.

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