RU2182129C1 - Method of water treatment using silver complex compound - Google Patents

Abstract

FIELD: technology of water treatment. SUBSTANCE: invention relates to water treatment by chlorination and heavy metal ions, in part, with silver ions. Method of water treatment involving its chlorination and the following addition of silver complex compounds characterized in that in the separated capacity 0.1-1.0% solution of Ag₂SO₄ or AgNO₃ is prepared preliminary where gaseous ammonia or ammonium hydroxide is added at stirring up to mass ratio Ag⁺ : NH₃ = 2.8-3.0. Then the prepared solution of ammonia complex silver compound is added to chlorinated water using a dispenser up to silver concentration 0.005-0.05 mg/l. Preferably, for preparing ammonia silver complex to prepare 0.1% solution of Ag₂SO₄ of 0.2% solution of AgNO₃. Method provides a possibility of prevention of secondary bacterial infection of water for a long time using stabilized solution of silver ammonia complex used at silver concentration lower of its maximal admissible concentrations in water. Invention can be used for drinking water disinfection in water supply systems of towns and other settlements. EFFECT: development of relatively simple effective method of water disinfection. 2 cl, 1 dwg, 1 tbl, 1 ex

Description

 The invention relates to techniques for treating water with chlorination and heavy metal ions, in particular silver. It can be used for disinfection of drinking water in the water supply systems of cities and other settlements, as well as for disinfection of recycled water pools.

 The most common way to disinfect water at water treatment plants is to chlorinate it. At the same time, the long practice of using this method has revealed a number of its significant shortcomings. Chlorination of water increases the risk of neoplasms in the person, diseases of the genitourinary tract, etc. In addition, the water treated with chlorine acquires an unpleasant taste and smell; the content of iron ions in it increases due to increased corrosion of pipelines. Chlorine does not have a lasting aftereffect: after a drop in its concentration in water, the latter undergoes secondary bacterial contamination. As a result, with a large length of the distribution networks before supplying the consumer, additional chlorination of water is required on the other hand, the used chlorinated tap water, which is drained into water bodies, can disrupt the biocenosis and exclude the possibility of their effective self-purification. In this regard, it is relevant to reduce the concentration of chlorine used for water treatment, as well as reduce its content in wastewater.

 For these purposes, chlorine treatment is combined using other reagents, such as copper, silver or zinc ions (US 5858246, C 02 F 1/50, 1999). However, this method is effective only when the concentration of heavy metal ions exceeds their MAC in water.

 The closest analogue of the claimed invention is known from US 5149354, A 01 N 25/08, 1992, a method of disinfecting water, including its preliminary chlorination to oxidize various organic and biological impurities and subsequent treatment with a composition exhibiting bactericidal, algicidal and fungicidal activity, containing soluble in water, copper salts in an amount of more than 50% of all other active ingredients, an organic amine capable of forming complex compounds with copper ions, a silver compound, glucon ie, capable of forming complexes with silver ions, and water. The composition is placed in a special container with walls permeable to water and installed in a swimming pool. Using the above composition allows to reduce the dose of chlorine while increasing the disinfecting effect. However, this method involves the use of a large number of different reagents and is not applicable for the treatment of drinking water.

 The technical problem to which the present invention is directed was the creation of a relatively simple, effective method of disinfecting water, ensuring the possibility of preventing its secondary bacterial infection for a long time using a stabilized solution of silver ammonia complex, used at a silver concentration below its MAC in water.

The problem is solved in that a method of treating water, including its chlorination and subsequent introduction of a silver complex compound, is characterized in that a 0.1-1.0% solution of Ag ₂ SO ₄ or AgNO ₃ , in which with stirring, gaseous ammonia or ammonia water is introduced until the mass ratio Ag ⁺ : NH _{3 of} 2.8-3.0 is reached, then the resulting solution of the ammonia complex silver compound is introduced into the chlorinated water using a batcher until it reaches a silver concentration of 0.005 -0.05 mg / l.

Preferably, to obtain an ammonia silver complex, a 0.1% solution of Ag ₂ SO ₄ or a 0.2% solution of AgNO _{3 is} prepared.

 It is the set of essential features of the invention, reflected in the independent claim, that provides the above technical result, and the features of the dependent claims reinforce this result.

The combination of water chlorination and its treatment with complex silver ions eliminates the need for re-chlorination, which means that the amount of chlorine used is reduced and, accordingly, the environmental safety of the method is increased. The introduction of ammonia in solutions of silver salts increases their solubility due to the formation of complex compounds Ag (NH ₃ ) ₂ NO ₃ or [Ag (NH ₃ ) ₂ ] ₂ SO ₄ . The proposed mass ratio between silver ions and ammonia exceeds by approximately 5% stoichiometric and is necessary to obtain the most stable compound. The indicated concentration range of solutions of silver salts used for the preparation of complexes is optimal for the storage of these reagents. Silver ammonia complexes have high bactericidal activity at a concentration of Ag ⁺ ions even lower than their MPC in water. The recovery of the complexes is slower than Ag ⁺ , therefore, the maximum bactericidal effect is manifested over a longer period of time. The presence of such anions as Cl ^- in the presence of silver complex compounds in water does not lead to the precipitation of insoluble AgCl.

 Below are examples of the implementation of the proposed method.

Example 1
The source water was treated with a coagulant - aluminum sulfate in an amount of 8 mg / l (in terms of Al ₂ O ₃ ) and filtered through a sand filter, then chlorine was introduced in an amount of 1.5 mg / l. The resulting water was kept for 2 hours, after which it had the following indicators: pH 7.0, suspended solids 0.35 mg / l, color 4.5 degrees, alkalinity 0.35 mEq / l, permanganate oxidation 4, 5 mg / l O ₂ , coli-titer 400, coli-index 4.

In a separate container, 10 L of the solution was prepared, feeding 20 g AgNO ₃ and water using dispensers. The resulting 0.2% AgNO ₃ solution was mixed with 4.2 g of ammonia gas, which was introduced from the balloon. Moreover, the mass ratio of Ag ⁺ : NH ₃ in the prepared solution was 3: 1, respectively. The resulting ammonia silver complex was introduced into the treated water until a silver concentration of 0.005 mg / L was reached.

The water treated with the ammonia silver complex was held for 48 hours, and then the coli index was determined. It amounted to 2. After that, the water was subjected to repeated bacteriological infection with a culture of E. coli 1257 in an amount of 10 ³ cells / ml and after 24 hours a bacteriological analysis of water was carried out. If the index has not changed. There was no smell and unpleasant taste near the water. The effect lasted for 3 months.

Example 2
To study the stability of disinfectant solutions, the initial water was chlorinated, then 0.5 mg / L of residual chlorine was removed with nitrogen. Water had the following composition: pH 7.2, total hardness 8.0, Ca ²⁺ 98.5 mg / L, Cl ^- 125.2 mg / L, SO ₄ ^2- 385.0 mg / L, NO ₃ ^- 5 , 1 mg / l, HCO ₃ ^- 3.4 mmol / l, dry residue 1085 mg / l. Prepared water was stored in a sealed, pre-disinfected container at a temperature of 20 ^o C. A culture of the sanitary indicative microorganism E.coli 1257 was introduced into the test portion of water in an amount of 10 ³ cells / ml, and then a disinfectant solution was added both freshly prepared and after 2, 10, 20, 30, 40 and 50 days of storage in a hermetically sealed container made of dark glass. As a disinfectant, we used a 0.8% solution of Ag ₂ SO ₄ or a solution of the ammonia complex Ag ₂ SO ₄ • 4NH ₃ , prepared by mixing in a separate container a 0.8% solution of Ag ₂ SO ₄ and ammonia water until a mass the ratio of Ag ⁺ : NH ₃ equal to 2.8, i.e. with an excess of ammonia about 5% relative to stoichiometry. Disinfection experiments were carried out at a silver concentration in the solution of 0.01 mg / L and a temperature of 20 ^o С. For disinfectants of different storage periods, the time was determined at which the complete death of microorganisms was achieved, while the specific activity of the freshly prepared bactericidal preparation was taken as 100%.

The drawing shows the dependence of the bactericidal activity of a solution of Ag ₂ SO ₄ (curve 1) and a solution of the ammonia complex [Ag (NH ₃ ) ₂ ] ₂ • SO ₄ (curve 2). As can be seen from the obtained data, the decrease in the bactericidal activity of the Ag ₂ SO ₄ solution occurs faster than the solution of [Ag (NH ₃ ) ₂ ] ₂ • SO ₄ , while the latter even loses only a third of its activity after 50 days, which indicates a stabilizing the role of ammonia. In addition, it was found that the solubility of the silver salt in ammonia water increases compared with pure water. This circumstance can be used to prepare more concentrated disinfectant solutions and reduce the size of consumable containers at water treatment plants.

Example 3
Water to study the resistance of tap water to secondary bacterial contamination was prepared and stored analogously to example 2, except that the residual chlorine was distilled off by heating to 50 ^o C and subsequent exposure for 3 hours.

The control sample - water without disinfectants - already on the 3rd day of storage exceeded the level of bacterial contamination: if index> 3. Water samples into which silver preparations were introduced successfully resisted pollution even when it was artificially infected with E. coli 1257 bacteria. The table shows the time required for disinfecting water by 99.9% depending on the concentration of bacteria (10-10 ⁵ cells / l) and Ag ⁺ concentrations (10 ^-3 -10 ^-2 mg / l). The measurements were carried out at a temperature of 30 ^o With, the most favorable for the development of microorganisms. Silver was introduced in the form of an ammonia complex of silver sulfate using a 0.1% solution of Ag ₂ SO ₄ into which ammonia water was added with stirring until a mass ratio between Ag ⁺ and NH _{3 of} 3.0 was reached.

Studies have shown that even 0.001 mg / L Ag ⁺ for 131.2 minutes completely neutralized the water into which E. coli was added in an amount of 10 ⁵ cells / L. With a tenfold increase in the concentration of Ag ^+, this time is reduced to 51.8 minutes.

 Thus, the proposed method of disinfecting water is effective, relatively simple and affordable. It is most expedient to use it for water treatment in hot climates, when there is a danger of secondary pollution of water that has been stored for a long time after the first stage of oxidative treatment with chlorination. The high bactericidal activity of silver sulfate or silver nitrate solution stabilized by ammonia, preserved for a long time (tens of days), makes it possible to stockpile this disinfectant, in particular, to ensure the possibility of their use in emergency situations, for example, in case of failure of the main disinfection unit or in case of contact in water a significant amount of pathogenic microflora.

Claims (2)

1. A method of treating water, including its chlorination and subsequent administration of a silver complex compound, characterized in that a 0.1-1.0% solution of Ag ₂ SO ₄ or AgNO ₃ is prepared in a separate container, into which a gaseous solution is introduced ammonia or ammonia water until the mass ratio of Ag ⁺ : NH ₃ equal to 2.8-3.0 is reached, then the resulting solution of the ammonia complex silver compound is introduced into the chlorinated water using a batcher until the silver concentration in it is equal to 0.005-0.05 mg / l 2. The method according to p. 1, characterized in that for the preparation of a solution of ammonium complex compounds of silver using a 0.1% solution of Ag ₂ SO ₄ or 0.2% solution of AgNO ₃ .

Images