RU2188169C1 - Method of preparation of potable water - Google Patents

Abstract

FIELD: methods of multi-stage purification of badly contaminated water. SUBSTANCE: method includes filtration of water, preliminary treatment, sterilization by ultra- violet radiation and subsequent conditioning through introduction of silver ions; preliminarily treatment is performed by chlorination; sterilization is performed by pulse ultra-violet continuous spectrum radiation in at least one submersible plant with the aid of xenon lamps mainly generating ultra-violet radiation at wave length of 200 to 400 nm, specific power requirements of 1 to 10 J per cubic centimeter of water and flux density of 1 to 10 W/sq.cm; conditioning is performed by means of solution containing diammine argentate ions obtained at electrolysis of water in electrolyzer at periodic change of electrode polarity containing no less than 99 mas.% of argentum followed by introducing gaseous ammonia or ammonia water at 3-5% excess of ammonia relative to stoichiometry; said solution is proportined in water in the amount corresponding to content of argentum of 0.001-0.02 mg/l at required concentration of chlorine introduced at chlorination stage and concentration of argentum added at last stage in the amount of 100-500:1, respectively. EFFECT: extended functional capabilities; facilitated procedure of preparation of water; enhanced ecological safety and operational reliability without considerable amount of decontaminants; possibility of storage of water thus prepared for extended period of time without impairment of its property. 8 cl, 1 tbl, 4 ex

Description

 The invention relates to multistage methods for treating highly contaminated water, including chlorination, ultraviolet (UV) irradiation and the introduction of heavy metal ions. It can be used, for example, for the purification and disinfection of drinking water in the water supply systems of settlements, including in local water treatment plants for collective use, at food industry enterprises, as well as in special mobile installations used in emergency situations and in areas with adverse environmental and epidemiological conditions for supplying disinfected drinking water to residential buildings, apartments, catering establishments, medical and children's institutions.

 One of the most common ways to disinfect water is to chlorinate it. However, when using chlorine, water acquires an unpleasant taste and smell, the danger of its negative effect on the human body increases due to the appearance of organochlorine compounds in it. Nevertheless, complete sterilization of water does not occur, because single microorganisms resistant to the action of chlorine remain in it. In addition, chlorine does not have a lasting aftereffect, because after a drop in its concentration, water may undergo secondary bacterial contamination.

 In connection with the above circumstances, it is relevant to reduce the concentration of chlorine due to its use in combination with other methods of water treatment.

 For example, a combination of chlorination with treatment with ions of copper, silver or zinc is known (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.

 Known multi-stage methods of processing natural water, in which there is no stage of chlorination. One of these methods involves two sequentially mechanical cleaning stages, pulsed UV irradiation of the continuous spectrum, reverse osmosis desalination, transmission through a carbon fiber sorbent, and repeated pulsed UV irradiation of the continuous spectrum (RU, 2033976, 1995). The disadvantage of this method is its complexity and high cost.

 A known method of producing drinking water from heavily infected, including bacteriologically, water sources, including the first stage of coarse and then fine mechanical filtration, the second stage of removal of toxic anions and cations using ion-exchange resins, the third stage of treatment on activated carbon, the fourth stage of sterilization using UV radiation and the final stage of conditioning (giving preservative properties) by passing water through silver-coated sand (RO 116545, 03/30/2001). This method, in combination of essential features and the achieved result, is the closest analogue of the proposed invention. Its disadvantages: complexity and long implementation time, high cost, as well as the need for periodic regeneration of ion exchange resins and silver sand treatment.

 The technical problem to which the present invention is directed was to expand the arsenal of effective means of treating drinking water and to create a relatively easy-to-use, environmentally friendly and reliable method that does not require the use of a large number of reagents for disinfecting water, including from heavily infected sources, and also providing the possibility of storing the obtained water for a long period without deterioration of its quality.

The problem is solved in that the method of producing drinking water, including its filtration, pre-treatment, sterilization with UV radiation and subsequent conditioning with the introduction of silver ions, is characterized in that the pre-treatment is chlorinated, sterilization is carried out by pulsed UV radiation of a continuous spectrum, at least one submersible installation using xenon lamps, mainly generating UV radiation with a wavelength of 200-400 nm, with specific energy consumption of 1-10 J per 1 cm ³ in rows and flux density of 1-10 W / cm ^2, and the conditioning is carried out by using a solution containing ions diamminargenat [Ag (NH _{z) 2]} ^+, obtained by water electrolysis in an electrolytic cell with periodic polarity reversal of electrodes containing at least 99 weight % silver, and the subsequent introduction of gaseous ammonia or ammonia water under the condition of a 3-5% excess of ammonia relative to stoichiometry, while this solution is dosed in water in an amount corresponding to a silver concentration of 0.001-0.02 mg / l in it, and observe the ratio of chlorine concentration, drive on the chlorination step and the silver concentration, added at the last stage in the range of 100-500: 1, respectively.

Preferably, during operation of the electrolyzer, the polarity of the electrodes is changed after 5-10 minutes, and the electrolysis is carried out at a water temperature of 20-30 ^o C and a pH of 6.5-8.5.

It is also preferable to sterilize with UV radiation at a water flow rate of 0.1-0.8 m ³ / h and a UV pulse frequency of 1-1.3 Hz.

 In the particular case when the water infestation is high, an additional stage of sorption purification of water is carried out before the stage of introducing the solution containing dimminagenate ions.

 In cases where previously chlorinated water is used in the process (for example, tap water, which has undergone secondary bacterial infection), the preliminary treatment is carried out by post-chlorination, preferably at a chlorine concentration of 2-4 mg / L.

 In another particular case, the method is carried out in a mobile installation.

 One embodiment of the invention provides that the resulting water is bottled and corked.

 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 chlorination of water, its treatment with continuous-spectrum ultraviolet xenon lamps and the introduction of diminminagenate ions at the optimal parameter values indicated in the formula provides effective purification and almost complete disinfection of heavily contaminated water. At the same time, the concentration of chlorine and silver ions is significantly reduced in comparison with most known methods of water treatment.

The diammminargenate ions [Ag (NH ₃ ) ₂ ] ⁺ used in the proposed solution are reduced more slowly than simple Ag ⁺ ions; therefore, the bactericidal effect is manifested over a longer period of time, and the effective concentration of Ag ⁺ obtained during the dissociation of diminminagenate ions
[Ag (NH ₃ ) ₂ ] ⁺ ⇄Ag ⁺ + 2NH ₃ , (1)
even lower than their MAC in water. As a result of dissociation, small amounts of silver ions and ammonia molecules are found in water. The latter also exhibits bactericidal properties. Since there are always Сl ^- ions in natural waters, silver ions bind them to a slightly dissociating AgCl salt; therefore, the equilibrium of reaction (1) is shifted to the right and new portions of Ag ⁺ ions constantly pass into the water, thereby maintaining the bacterial stability of the water for a long period of its storage .

 The advantage is that diamminargenate ions can be obtained directly in the disinfected water by electrolysis, with additional activation of the water and thereby increases the bactericidal effect. The use of a pure silver anode virtually eliminates the addition of additional harmful impurities to the water and reduces the risk of precipitation on the electrodes. This is also facilitated by periodic changes in the polarity of the electrodes.

The synergistic effect when using the proposed multistage method of water disinfection is also associated with the fact that in a highly oxidized environment conditions arise for the transition of Ag ⁺ to Ag ²⁺ . The resulting Ag ²⁺ cations, possessing increased individual oxidizing ability, are also characterized by increased (compared to Ag ⁺ ) bactericidal properties. Moreover, even after the reverse transition of Ag ²⁺ to a more stable state (Ag ⁺ ), the resistance of the treated water to secondary bacterial contamination remains.

 The proposed quantitative restrictions on the parameters of water irradiation, as well as the concentration of chlorine and silver ions, are optimal for this water treatment scheme. Recommended concentration ratios of silver and ammonia ions, corresponding to an excess of ammonia relative to stoichiometry, correspond to the maximum stability of complex compounds.

 The use of continuous-spectrum xenon lamps, preferably emitting in the 200-400 nm region of the ultraviolet spectrum, which includes a "bactericidal" and corresponding to the destruction of organic compounds, allows to obtain a high disinfecting and cleaning effect, reduces processing time and ensures environmental cleanliness, since replacing mercury lamps with xenon eliminates the possibility of mercury contamination of water when the lamp is destroyed.

 The simplification and acceleration of the proposed method in comparison with the prototype is associated with a reduction in the number of stages of water treatment, using relatively easily prepared reagents, with high productivity and efficiency of the UV sterilization unit.

Below are examples of the implementation of the proposed method
Example 1
The method was carried out in a mobile installation. The source water (the main indicators are shown in the table) with a volume of 200 l at a temperature of 18 ^o C 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 column loaded with quartz sand, after which liquefied chlorine from a cylinder in an amount of 1 mg / l and kept for 1.5 hours. Then the water was sterilized, passing at a speed of 5 l / min (0.3 m ³ / h) through a UV treatment unit containing pulsed pulsed in the water layer continuous spectrum xenon lamps, predominantly emitting in a range of 200-400 nm with a pulse frequency of 1 Hz, a flux density of 2 kW / cm ² and specific energy consumption of 5 J / cm ^{3 of} water. The water temperature at the outlet of the installation was 30 ^o C. The sterilized water was collected in a separate tank in which the dispenser was introduced using a solution containing ions diamminargenat [Ag (NH _{z) 2]} ⁺ to achieve silver concentration in water equal to 0.005 mg / l .

The specified solution (concentrate) containing diminminarate ions was preliminarily prepared by passing water at a speed of 0.2 m / s at a temperature of 20 ^° C and a pH of 7.0 through an ionizer. As electrodes in the ionizer, plates of pure silver Ср 999.9 (GOST 6836-80) were used. The distance between the electrodes is 10 mm, the current density is 1 mA / cm ² , the voltage at the electrodes is 6 V, the frequency of change of polarity of the electrodes is 10 min. As a result of electrolysis, the concentration of silver ions in water was 0.5 mg / L. This water is fed to the mixing vessel and the ammonia is simultaneously injected from the cylinder at a weight ratio Ag: ⁺ NH _z, respectively equal to 3: 1, which corresponded to ~ 3% excess relative to the stoichiometry of the ammonia.

 The treated water was kept for 24 hours, and then its main indicators were determined.

 The measurement results are shown in the table.

 The data presented indicate a high quality water treatment carried out by the proposed method. At the same time, not only is disinfection of water achieved, but also other indicators are improved - taste, smell, color, inorganic and organic impurities. The resulting water was bottled in 20 L bottles and corked. When storing treated water for 3 months, pathogenic microorganisms were not found in it.

Example 2
The water obtained in Example 1 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 forms were not found. There was no smell and unpleasant taste near the water. The effect lasted for 3 months.

For comparison, we evaluated the effect of each stage of water treatment separately (only chlorination at a concentration of 1 mg / L or only UV treatment with the parameters specified in Example 1, or only the introduction of a solution containing diminminagenate ions to an Ag ⁺ content of 0.005 in water mg / l) on the quality of water purification and disinfection. Moreover, after 24 hours after the completion of each stage, repeated bacteriological infection of water was carried out as described above. In none of these cases was it possible to obtain a stable disinfecting, cleaning and preserving effect.

Example 3
Water treatment was carried out analogously to example 1, with the exception of the following. Used a stationary device, the volume of water 5 m ³ . The source water instead of bac turigiensis contained botulinum toxin in the concentration indicated in the table (other indicators of water coincided). Chlorination was carried out with sodium hypochlorite obtained by electrolysis of a 10% aqueous NaCl solution. The concentration of active chlorine in water during its preliminary treatment was 2.0 mg / L. Also, the difference was that the UV treatment was carried out in a submersible reactor at a water flow rate of 0.3 m ³ / h using continuous-spectrum pulsed xenon lamps with a pulse frequency of 1.3 Hz, a flux density of 5 kW / cm ² and specific energy consumption of 6 J / cm ^{3 of} water. The water temperature at the outlet of the installation was 32 ^o C.

To prepare a bactericidal solution, part of the water was passed with a flow rate of 0.1 l / s through an electrolyzer with electrodes containing 99% Ag in floats. The distance between the electrodes made in the form of plates is 8 mm, the current density is 2 mA / cm ² , the voltage at the electrodes is 6 V, the frequency of change of polarity of the electrodes is 5 min. As a result of electrolysis, the concentration of silver ions in water was 0.2 mg / L. Ammonia gas was introduced into the resulting water at a temperature of 20 ^o With a mass ratio of Ag ⁺ :
NH ₃ , respectively, equal to 2.9: 1 (~ 5% excess of ammonia). The prepared concentrated solution was introduced into the treated water until the concentration of Ag ⁺ in it was equal to 0.004 mg / L.

 The results are presented in the table. The resulting water met all accepted quality standards.

Example 4
Similar to example 1, except that the source water instead of botulinum toxin was infected with hepatitis A virus at the concentration indicated in the table. The difference also consisted in the fact that before the introduction of the solution containing diamminargenate ions, water was passed through a sorbent - activated carbon. The results obtained indicate a high degree of purification and bactericidal action of water obtained by this method. The water prepared in accordance with the proposed method according to sanitary standards is suitable for use in drinking, medical and household purposes.

 The advantage of the proposed method is its effectiveness in cases where available water sources have a strong bacterial infection and significant concentrations of organic impurities, as well as the possibility of its implementation in compact mobile units to ensure the supply of drinking water in emergency situations.

Claims (8)

1. The method of producing drinking water, including its filtration, pre-treatment, sterilization with UV radiation and subsequent conditioning with the introduction of silver ions, characterized in that the pre-treatment is chlorinated, sterilization is carried out by pulsed UV radiation of a continuous spectrum in at least one submersible type using xenon lamps, mainly generating UV radiation with a wavelength of 200-400 nm, with a specific energy consumption of 1-10 J per 1 cm ^{3 of} water and a flux density of 1-10 W / cm ² , and air conditioning The positioning is carried out using a solution containing di-aminargenate ions [Ag (NH ₃ ) ₂ ] ⁺ obtained by electrolysis of water in an electrolyzer with periodic polarity reversal of electrodes containing at least 99 wt.% silver, and subsequent introduction of gaseous ammonia or ammonia water at the condition of a 3-5% excess of ammonia relative to stoichiometry, while this solution is dosed into water in an amount corresponding to a silver concentration of 0.001-0.02 mg / l in it, and the ratio of the concentration of chlorine introduced in the chlorination stage is observed, and the concentration of silver added in the last stage, in the range of 100-500: 1, respectively. 2. The method according to claim 1, characterized in that during operation of the electrolyzer, the polarity of the electrodes is changed after 5-10 minutes, and the electrolysis is carried out at a water temperature of 20-30 ^o C and a pH of 6.5-8.5. 3. The method according to claim 1 or 2, characterized in that the sterilization by UV radiation is carried out at a water flow rate of 0.1-0.8 m ³ / h  4. The method according to any one of claims 1 to 3, characterized in that the pulse frequency of the UV radiation is 1-1.3 Hz.  5. The method according to any one of paragraphs. 1-4, characterized in that before the stage of introduction of the solution containing dimminagenate ions, an additional stage of sorption purification of water is carried out.  6. The method according to any one of claims 1 to 4, characterized in that the pre-treatment is carried out by post-chlorination, while the chlorine concentration is 2-4 mg / L.  7. The method according to any one of claims 1 to 6, characterized in that it is carried out in a mobile installation.  8. The method according to any one of claims 1 to 7, characterized in that the resulting water is bottled and corked.

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