RU2122524C1 - Water treatment process - Google Patents

Abstract

FIELD: water treatment. SUBSTANCE: invention is intended to chemically treat water containing large amounts of fluoride. Sediment resulting from coagulation treatment of water is treated with hydrofluoric acid to give ashes that is controlled by potentiometric or conductometric. Insoluble residue is separated by mechanical filtration. Filtrate sol is further used for coagulation of water involving fluoridation, and solid residue is used in manufacture of building materials. Method enables isolation of natural fluoride from water for fluoridation of fluoride- deficient water, whereas coagulant is reused for peptization of metal hydroxide sediment. EFFECT: reduced reagent intake and simplified process. 1 dwg, 8 tbl

Description

 The invention relates to the field of chemical water purification using coagulation, disinfection and sedimentation of suspended solids and can be used in the purification of water containing a large amount of fluorine.

 Water is the pillar of life and at the same time it often carries death, most of all diseases are associated with contamination of water sources. Both small and large concentrations of fluoride in drinking water are harmful to the human body. With a lack of fluoride in the diet of people, the spread of dental caries of the population is observed, often leading to tooth loss and, as a result, to chronic internal diseases. Therefore, for the fluorination of water, an increase in fluoride ions in water is used by dosing fluorine-containing compounds, for example, sodium silicofluoride, sodium fluoride, aluminum silicon fluoride, etc. These reagents are toxic to humans in case of an overdose. The increased fluorine content in water of an unacceptable concentration also leads to tooth fluorosis and skeletal fluorosis, de-delineation of tendons and ligaments, limitation of body mobility, pain. Water is defluorinated with reagents, followed by filtration. Reagent methods for the removal of fluorine from water are based on sorption of it with magnesium or aluminum hydroxides (V. A. Klyachko, I. E. Apeltsin. Purification of natural waters. Publishing house lit., p. , GG Rudenko, IT Goronovsky. Removal of impurities from natural waters at waterworks, K, 1976).

 The closest in technical essence is a method of purifying water containing a large amount of fluorine, including treating it with a coagulant and subsequent discharge of sludge (SU, copyright certificate 261996, class C 02 F 1/58, 1970). The disadvantage of this method is the large irretrievable loss of reagents and large areas of land for storing the formed hardly dehydrated precipitation, in which the fluorine of natural water and metal hydroxides are irretrievably lost.

 The objective of the invention is the extraction of natural fluorine from water, followed by its use for water fluoridation, as well as the reuse of the coagulant after peptization of the metal hydroxide precipitate, the reduction of capacities for storing hard-dehydrated coagulates, the reduction of the consumption of reagents for cleaning, the ecological purity of the method, the manufacture of building products from tailings after peptization.

 The problem is solved by the proposed method, in which, after purification of water by coagulation, a coagulum precipitate is collected by 3-5 hours return and treated with hydrofluoric acid until a sol is formed, the insoluble part of the precipitate is separated by filtration and used in the production of building materials, and the filtrate is used as a fluorination reagent and coagulation of water depleted in fluorine. The process of pentization of the coagulant precipitate is controlled by potentiometric or conductometric titration until the second jump of the metal hydroxide transition, followed by separation of the insoluble acid precipitate by mechanical filtration and feeding it to the manufacture of various building products.

 The total amount of acid to obtain a sol is 0.3-0.8 equivalents with respect to the content of metal hydroxide in the coagulum, its age, and the physicochemical composition of the precipitate.

 The invention is illustrated by a water treatment scheme according to the proposed method. The scheme contains the following apparatuses, interconnected by a piping system: a sump 1 for water enriched in fluorine, after coagulation, a container 2 for coagulate, mechanical filters 3, a clean water tank 4, a sludge thickener reactor 5, a regeneration device 6, a disposal workshop 7 acid-insoluble precipitates that are periodically processed, a wash water sump 8 from the filtrates, a sump 9, a tank for sol oxidizing agents 10.

 The method is as follows.

 Sump 1 receives water from an art well that contains a large amount of fluorine. Defluorizing coagulant is added to the water. Settled water through filters 3 enters the reservoir of clean water 4 for supply to the consumer. The precipitated precipitate — the coagulum is thickened in thickener 5, and then fed to hydrofluoric acid regeneration in the amount necessary to convert the coagulum to sol before the third stage of metal hydroxide transition, which is controlled by a pH meter, after stirring for 5 minutes. The process can be controlled with a conductivity meter. The regeneration mixture is fed for dehydration, and then the filtrate enters the coagulation of the water fluorination station. In the case of accumulation of a coagulant-regenerate, it is fed to granulation. A disinfecting agent is fed to the filtrate. The filter wash water is collected in a settling tank 9, from where it is also fed to a thickener 5. An acid-insoluble precipitate from the regenerator and a cleaning precipitate are periodically dumped onto the seal. To clarify the regenerated coagulant, oxidizing agents are fed into the regenerator, after which the coagulant is used for its intended purpose. If there is a water treatment plant nearby that requires the addition of fluorine, the proposed water treatment treatment scheme is applied. If the water fluoridation station is located at a certain distance from the water defluorination station, then the regenerated coagulant is transported in the same way as other reagents used for water purification.

 The amount of return of basic salts from hydroxides by regeneration depends on the amount of acid in stoichiometry to metal hydroxide and the age of the precipitate, as can be seen from the experimental results in table. one.

 The dose of the regeneration product is calculated from the amount of salts transferred to the solution, and is determined experimentally in each case. The research results are summarized in table. 1-8.

 Example. The studies were carried out at the Institute of Colloidal Chemistry and Water Chemistry of the Academy of Sciences of the Ukrainian SSR, as well as at sewage treatment plants on the river. Dnieper, Desna. Physico-chemical characteristics of the water changed according to the seasons of the year. The specific characteristics of water are given in table. 2, 3. To study the sanitary-hygienic properties of the regenerated coagulant with hydrofluoric acid, portions of the samples were sown on MPA. Colony counting was carried out according to the method in accordance with GOST 18963-73. During the cleaning process, water is mainly freed from fungi and bacteria, while the Coli group of bacteria is more resistant to the action of coagulants and requires the disinfection of water by oxidizing agents.

 The results of the disinfection of water purified by regenerated coagulant are given in table. 4.

 To study water quality, water analysis methods were used, described in the book "Unified Methods of Water Analysis", ed. Yu.Yu. Lurie, M .: Chemistry, 1971. Technological schemes for water purification were used from the methods "Fundamentals and technology of water conditioning", Kiev, 1983. Coagulants for regeneration were taken directly from existing facilities at treatment plants, and also obtained from model waters necessary for composition studies. To compare the methods of water purification, water was also processed according to the prototype (as.with. 261996).

 From a comparison of the data obtained it follows that the proposed method of purification may reuse natural fluoride for water purification, saving coagulant and increasing the economic effect of water purification.

Claims (1)

 A water treatment method comprising treating water with a high fluorine content with a coagulant and separating the precipitate, characterized in that the precipitate is treated with hydrofluoric acid to form a sol, the insoluble part of the precipitate is separated by filtration and used in the production of building materials, and the filtrate is used as a reagent for fluorination and coagulation of water, depleted in fluorine.

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