SU947066A1 - Process for defluorination of effluents - Google Patents

Description

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The invention relates to methods for purifying natural waters from fluorine for drinking-water supply systems.

A known method of contact coagulation for the defluorization of natural substances is as follows: a solution of aluminum salt is added to the treated water before the filtration charge for 1.52, 0 hours with a concentration of 130-150 mg / l (charge) and further until the end of the filtration cycle with a dose of 15-20. mg / l according to ACOZ Cl.

However, this method is highly efficient in defluorization of relatively soft waters (with hardness up to 7 mEq / l), since when using it the rigidity of the baud does not decrease and in these cases (with increased hardness) additional water softening is necessary.

The closest in technology. essence and achievable re-.

As a result, a sorption metric is used for the removal of hard waters, in which magnesium hydroxide is used as a sorbent. The use of this method in comparison with others does not require a subsequent water drain. The process of removal of fluorine with magnesium hydroxide pr (1 x scoop as follows; treated water is mixed with alkaline reagents (lime, soda), then passed through a suspended layer of formed magnesium hydroxide flakes and filtered through a granular charge. The process of defluorization proceeds at a concentration of 2000 mg). mg / l The load on the brightener cross section is not more than 0.7-1.1 m / h / 0.20, 3 mm / s. The process of defluorization proceeds at a pH of water of 10-11 C2.

The disadvantages of this method are 1dts high specific consumption of re-. for example, when the concentration of fluorine in water is 3 mg / l, the consumption per 1 mg / l of removable fluorine is 158,800 mg / l, high. The pH of the water after its treatment, which requires subsequent acidification, has a longer duration (water drainage (4-6 hours), caused by low specific loads on the brightener cross section. The purpose of the invention is to increase the process economics by reducing the dose of reagents and the duration of water treatment .. This goal is achieved by the fact that in the method of defluorization of natural waters, including the treatment with alkaline reagents, sorption in a suspended layer in a contact chamber and the subsequent separation of an o.sad, concentration of the suspended layer in the contact chamber, 50000100000 mg / l is maintained for a duration of water stay of 12-18 minutes and a pH of 9-9. The method is carried out as follows. Water after the introduction of alkaline reagents in doses that ensure release of magnesium hydroxide is processed sequentially in a contact-positioning chamber. a conically expanding type, directly passing into a settling tank with inclined thin-layer elements, sand filter. (At this, thin-layer elements are installed in such a way as to ensure continuous transportation and recycling Street tion necessary part of the sediment back into contact to the measure. The concentration of the suspended layer in the contact chamber should be 50100 g / l. To conduct the process at a concentration of less than 50 g / l is not technologically feasible, since at the same time the degree of fluorine removal decreases. The concentration of more than 100 g / l leads to overspending of the reagents, since the degree of fluorine removal does not increase. The pH of the treated water is in the range of 9-9.5. At pH less than 9, the amount of precipitated hydroxide is not enough to adsorb fluorine. When the pH is over 9.5 and the concentration of the suspended layer is more than 50 g / l, almost the entire amount of hydroxide si falls out, i.e. an increase in pH of 64 does not produce an effect and leads to an overrun of reagents. The processing time of the water in the contact sorption chamber is at least 12–18 min. With shorter treatment time, the volume of the contact chamber becomes insufficient to provide the desired flocculation effect, and with longer treatment time, the process becomes uneconomical. The treatment time for water in thin-layer elements is 20-30 minutes. This time is justified, on the one hand, by the requirement for the quality of clarified water, and on the other, by its cost-effectiveness, as well as by the largest ones. time values, the consumption of materials from which thin-layer elements are made becomes high. The angle of inclination of the cells is not less than 60, which ensures continuous transportation and recirculation of the sediment. With a smaller inclination angle, the complete creeping and recirculation of the precipitate is not provided and its accumulation in the cells is possible. The main purpose of the inclined thin-layer elements is the transportation of the precipitate released on their surface into the contact sorption chamber, which allows the concentration of the sorbent in the chamber to be up to 50,000-100,000 mg / l, i.e. 30-50 times higher than in the known method. At the same time, thin-layer elements provide deep water clarification, as well as stable and reliable equipment operation. Example. The quality of the source water of the object, on which pilot tests are carried out, is the following: fluorine 2.0 mg / l, hardness 13.7 meq / l; Ca 5.3 mEq / L; MD 8, mEq / l; alkalinity k, J mg-eq / lsulfate 380 mg / L, chlorides H if mglt} iron 0.38 mg / l. The studies were carried out on an industrial plant with a capacity of 5 MVcyT, which consists of a conical contact-sorption chamber, a thin layer inclined cellular sedimentation tank, a fast sand filter, tanks for preparing reagent solutions and devices for their dosing. During the tests, the required quantities of soda and lime are injected into the treated water, causing the release of hardness salts, including sorbent, magnesium hydroxide. The results of the experiments are given in table. one .

T a b l i. c a 1

PRI mme R 2. The water quality of the object is iron 2.3 mg / l. The installation on the test bed, the swarm is conducted experiment, similar

the following: fluorine 3, mg / l; stiffness zo given in example 1, E mEq / l; Ca 6.1 mEq / L} Md

8.7 mEq / L, alkalinity 5.1 mEq / l; The results of the experiment reduced the sulfates to 95 mg / l; 2bO mg / l chlorides; 2

Claims (2)

Table 2 The proposed method allows-: to obtain high technical and economic indicators. Approximate calculations show that, for example, at one of the objects with a capacity of 1000), economic efficiency is 115 thousand rubles for reduced costs, thousand rubles for capital investments, and the cost decreases from 35 kopecks. up to 9 kopecks per 1 m. As a result of applying the proposed method, the sorption index, i.e. the ratio of the amount of fluoride retained and the concentration of the selected magnesium hydroxide increases and reaches values of 0.055-0.042, i.e. 2.0-2.5 times higher than in the known method. At the same time, the water treatment time is dramatically reduced to 50-60 minutes, i.e. 5-6 times. The advantage of this method is also that there is no need to use additional methods of reducing the rigidity. 668 The invention method of defluorizing natural waters, including treatment with alkaline reagents, sorption in a suspended layer in the contact chamber and subsequent separation of sediment, different. By the fact that, in order to increase the economics of the process by reducing the dose of reagents and the duration of water treatment, the concentration of the suspended layer in the contact chamber is below 50000-100000 mg / l with a duration of water stay of 12-18 minutes, and a pH of 9-9.5. Sources of information taken into account at. examination 1.Kl chko VA, Apeltsin NE. Purification of natural waters. M., stroiizdat, 1971, p. k 8-kSO, 2.Zolotova EF, Ase G. Yu, Water purification from iron, fluorine, manganese and hydrogen sulfide. M., Sgroyizdat, 1975, p. 135-H2.