RU2581870C1 - Method of purifying waste water - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: invention relates to methods of purifying waste water and can be used for cleaning water from oil products, fats and suspended substances. Method of purifying waste water is sequential processing of water by passing it through sand trap 2, oil trap-settling tank 3, flotator-settling tank, granular 5 and sorption filters 6 integrated into single housing 1 of plant. Sand trap combines elements tangential and vertical sand catchers. Intensive-settler is inclined both in direction of water, and from Center to periphery. Floating in flotation water flows in settling zone 11, enclosed from clarified water with cylindrical baffle 12, which increases effect of cleaning due to complete passage of floatation process and precipitation is not released into cleaning of impurities. Additionally purified water in filtering unit on granular and sorption filters with movement of water from above downwards and upwards respectively.

EFFECT: higher efficiency of purifying waste water from petroleum products, fats and suspended substances, reduced cost of their cleaning and maximum use of capabilities of treatment facilities.

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Description

The invention relates to methods for wastewater treatment and can be used to purify water from oil products, fats and suspended solids.

A known method of purification of wastewater by flotation by saturating the wastewater with air or some gas dissolved in water under pressure. When pressure is released from wastewater, air dissolved in it or some other gas in the form of bubbles is released. At the same time, finely dispersed hydrophobic substances adhere to the bubbles and, in the form of particle-bubble complexes, float, forming a foam layer that contains particles of impurities. The foam layer by gravity or using a special device is periodically or continuously removed into the sludge collector. The purified liquid is discharged from the zone below the formation of particle-bubble flotation complexes / Gvozdev V.D., Ksenofontov B.S. Industrial wastewater treatment and sludge recovery. - M.: Chemistry, 1988, p. 60-76 / [1].

The disadvantage of this method is the low floating rate of the particle-bubble flotation complexes due to the small size of the bubbles. The low floating rate of these flotation complexes leads to the fact that some of them follow the flow of discharged cleaned liquid, which leads to a sharp decrease in cleaning efficiency.

A known method of wastewater treatment by flotation, including wastewater treatment by flotation, carried out by aeration of wastewater with air bubbles and other gases and further separation of the resulting particle-bubble flotation complexes from water. In this case, the dispersion of air and other gases in water occurs mechanically, for example, by ejection of air due to the movement of a fluid flow at a speed of about 8 ... 12 m / s or during suction in a zone of reduced pressure during rotation of the fluid flow using a mixer (impeller). The gas (air) bubbles formed behind the ends of the rotating blades of the mixer come into contact with the particles of contamination, which in most cases leads to the appearance of particle-bubble flotation complexes. The size of the resulting bubbles is more than 0.01 mm When air or other gases are dispersed using a mixer, natural coalescence of bubbles occurs, which leads to a significant change in their size, and in the rotation zone of the mixer (impeller) the size of the bubbles is about 0.01 ... 0.5 mm or more, and in the upper zone, where there is separation from water and their transition into the foam layer, the size of the bubbles reaches 1.0 ... 10.0 mm or more. At the same time, water purified from particles of contaminants is discharged from the floatation zone of the particle-bubble flotation complexes. / Ksenofontov B.S. Wastewater treatment: flotation and thickening. - M.: Chemistry, 1992, p. 44-46 / [2].

The disadvantage of this method is that as a result, the diverted water stream captures part of the particle-bubble complexes, as well as individual particles and bubbles not loaded with pollution particles, which leads to a decrease in the efficiency of wastewater treatment in this way.

There is a method of treating wastewater by successively lagging, flotation and filtering, and flotation is carried out in the forced (artificial) coalescence of microbubbles by adding a saturated solution of gas readily soluble in water, such as carbon dioxide or hydrogen sulfide, to the wastewater, as well as placing hydrophobic surface bubbles . Microbubbles not trapped in clarified water coalesce at the inlet of a filter charge consisting of particles of coal and peat, and a flotation concentrate of high peat is used. The foam product formed at the flotation stage and the filtration - foam cake are combined and sent for separation by decantation into light and heavy fractions, and the latter is returned to the settling stage. / Patent RU No. 2108974, M. cl. C02F 1/24. The method of wastewater treatment. // Ksenofontov B.S. Publ. April 20, 1998 / [3].

The disadvantage of this method is that the flotation process is accompanied by the addition of a water-air mixture to the wastewater, the preparation of which requires the use of additional equipment. This entails an increase in operating costs and complexity of the process.

The closest in technical essence to the claimed method is a method of treating wastewater from petroleum products, including pre-treatment and post-treatment by filtration through a layer of a stationary sorbent, where natural apatite is used as a sorbent. / Patent RU No.2010008, M. cl. C02F 1/28. The method of wastewater treatment from petroleum products. // Alekseev M.I., Svetashova E.S., Panov S.N. Publ. March 30, 1994 Bul. No. 28 / [4] - taken as a prototype.

The disadvantage of this method is the relatively insignificant absorption capacity of adsorption systems (materials), which implies the short-term operation and a comparative increase in the cost of their maintenance.

The invention consists in the following. The problem to which the claimed invention is directed, is to improve the quality of wastewater treatment with minimal operating costs for their treatment.

The technical result is an increase in the efficiency of the method of treating wastewater from oil products, fats and suspended solids, cheapening the method of their treatment and maximizing the use of treatment facilities.

The specified technical result is achieved due to the fact that in the known method of wastewater treatment, including sequential treatment of water by mechanical treatment through a sand trap, oil trap-settler, flotator and after-treatment on a sorption filter, the feature of which is that the water is further purified on a granular filter, while initially it is passed through a sand trap, combining in its design elements of a tangential and vertical sand trap, an oil trap-sump, the bottom of which has a slope from center to the periphery in the direction of movement of the water, which ensures sedimentation with subsequent removal, then the purified water is subjected to aeration with air in a flotator, which has cylindrical baffles, dividing it into flotation and sedimentation zones of flotated water, represented by a conical bottom and a pipe for drainage, which increases the cleaning effect due to the completeness of the flotation process and precipitation of contaminants that did not stand out at the previous stages of cleaning; after removing contaminants and sediments, the flotated and settled water is passed through a granular filter, where the water, moving from top to bottom, passes through it, then makes a 180 degree turn, rises up to the overflow hole formed by a partition installed between the granular and sorption filters, and falls down, then enters the sorption filter, where it rises from the bottom up until it reaches the pipe for the removal of purified water located in the upper part of the sorption filter, while precipitation from the ters removed through nozzles for discharging sediments at the bottom of the bottom slopes to each filter. As a granular filter load, crushed expanded clay is used, for washing of which there is a pipe in its upper part. Activated carbon is used as a sorption filter charge.

The drawings show:

In FIG. 1 shows the layout of treatment facilities (side view); The following designations are accepted: 1 - device body; 2 - sand trap; 3 - oil trap sump; 4 - flotator settler; 5 - granular filter; 6 - sorption filter; 7 - pipe outlet of purified water; 8 - overflow pipeline; 9 - flotation chamber; 10 - zone of clarified water; 11 - settling zone; 12 - a cylindrical partition; 13 - pipe discharge sediment oil trap-sump; 14 - pipeline discharge of floating sediment; 15 - pipeline supplying water to the filter unit; 16 - a partition separating the filters; 17 - sedimentation tray; 18 - tray for collecting foam; 19 - pipe discharge foam; 20 - partitions for fluid flow; 21 - overflow hole; 22 - pipe discharge sediment granular filter; 23 - pipe outlet sludge sorption filter; 24 - pocket; 25 - disk aerator; 26 - compressor; 28 - pipe outlet sediment sand trap; 29 - pipe outlet wash water granular filter;

In FIG. 2 is a top view (section AA); The following designations are accepted: 2 - sand trap; 3 - oil trap sump; 4 - flotator settler; 8 - overflow pipeline; 9 - flotation chamber; 10 - zone of clarified water; 11 - settling zone; 12 - a cylindrical partition; 18 - tray for collecting foam; 19 - pipe discharge foam; 25 - disk aerator; 26 - compressor; 27 - sewage supply pipe;

In FIG. 3 shows a filter unit (section BB); The following designations are accepted: 5 - granular filter; 6 - sorption filter; 16 - a partition separating the filters; 20 - partitions for fluid flow; 22 - pipe discharge sediment granular filter; 23 - pipe outlet sludge sorption filter; 24 - pocket;

In FIG. 4 shows a schematic flow chart of wastewater treatment; The following designations are accepted: 2 - sand trap; 3 - oil trap sump; 4 - flotator settler; 5 - granular filter; 6 - sorption filter; 7 - pipe outlet of purified water; 27 - sewage supply pipe.

The proposed method is as follows. Wastewater is fed by gravity to the primary treatment unit 27 by gravity, where it is subsequently treated on a sand trap 2, equipped with a sludge discharge pipe 28, oil trap 3 and through an overflow pipe 8 from oil trap 3 are fed into the flotation chamber 9, which together with water through the disk aerator 25 from the compressor 26 is supplied with air; coarse and finely dispersed substances dissolved in water are captured by air bubbles and carried to the surface of the water to be cleaned, where foam is formed, which is collected in the foam collecting tray 18 and is discharged through the branch pipes for the sedimentation of the oil trap-settler 13. The floated water from the flotation chamber 9 flows into a settling zone 11 equipped with a cylindrical partition 12. In the settling zone 11, air bubbles dispersed in water are completely released after flotation, after which the water flows into the clarified water zone 10 Through the drainage pipe of the floating sludge 14, the sludge falling to the bottom of the flotation tank-settler is removed 4. The clarified water is discharged from the primary treatment unit through the water supply pipeline and fed to the lower filter unit. The purified water is supplied to the granular filter 5. The water, moving from top to bottom, passes through the granular filter 5, makes a 180 ° rotation and, through the pocket 24 formed by the partition separating the filters 16 and the liquid transfer partition 20, rises to the overflow hole 21 and falls to the bottom of the structure, after which it again changes direction and undergoes post-treatment on the sorption filter 6 with an upward flow of water. The purified water is discharged through the outlet pipe of the purified water 7. The filter block is flushed by supplying washing water through the pipe 7 and discharged through the outlet pipe of the washing water of the granular filter 29. Precipitated precipitates after washing the granular and sorption filters are discharged respectively through the branch pipe of the sediment of the granular filter 22 and the pipe sediment removal sorption filter 23.

Example 1. Purification of surface wastewater with a suspended solids concentration of 1832 mg / l, oil products 151.5 mg / l, iron (total) 1.56 mg / l. As a result of surface runoff cleaning by the proposed method, clarified water was obtained with a concentration of suspended solids of 16.49 mg / l, petroleum products of 4.53 mg / l, and iron (total) 0.34 mg / l.

Example 2. Purification of surface wastewater with a concentration of suspended solids 2030.0 mg / l, oil products 77.0 mg / l, iron (total) 1.24 mg / l. As a result of surface runoff cleaning by the proposed method, clarified water with a concentration of suspended solids of 18.27 mg / l, petroleum products of 2.3 mg / l, iron (total) 0.27 mg / l was obtained.

Example 3. Purification of surface wastewater with a suspended solids concentration of 1756.0 mg / l, oil products 31.6 mg / l, iron (total) 1.29 mg / l. As a result of surface runoff cleaning by the proposed method, clarified water with a concentration of suspended solids of 15.8 mg / l, oil products of 0.95 mg / l, and iron (total) of 0.28 mg / l was obtained.

The claimed invention when used will improve the speed, efficiency and quality of treatment due to double filtering of the purified water: a granular filter and sorption.

The compactness of the proposed wastewater treatment plant can significantly reduce the production space it occupies, thereby expanding the possibilities for its use.

Information sources

1. Gvozdev V.D., Ksenofontov B.S. Industrial wastewater treatment and sludge recovery. - M.: Chemistry, 1988, p. 60-76.

2. Xenophon B.S. Wastewater treatment: flotation and thickening. - M.: Chemistry, 1992, p. 44-46.

3. Patent RU No. 2108974, M. cl. C02F 1/24. The method of wastewater treatment. // Ksenofontov B.S. Publ. 04/20/1998

4. Patent RU No.2010008, M. cl. C02F 1/28. The method of wastewater treatment from petroleum products. // Alekseev M.I., Svetashova E.S., Panov S.N. Publ. March 30, 1994 Bul. No. 28.

Claims (3)

1. A method of wastewater treatment, including sequential treatment of water by mechanical cleaning through a sand trap, oil trap-settler, flotator and tertiary treatment on a sorption filter, characterized in that the water is further purified on a granular filter, while initially it is passed through a sand trap, combining the elements are tangential and vertical sand traps, an oil trap-settler, the bottom of which has a slope from the center to the periphery in the direction of water movement, which ensures sedimentation from by removing them, then the water to be purified is subjected to aeration with air in a flotator, which has cylindrical baffles, dividing it into flotation and sedimentation zones of flotated water, represented by a conical bottom and a pipe for drainage of sediments, which increases the cleaning effect due to the completeness of the flotation process and precipitation sediment that did not stand out at the previous stages of purification of contaminants; after removing contaminants and sediments, the flotated and settled water is passed through a granular filter, where the water, moving from top to bottom, passes through it, then makes a 180 degree turn, rises up to the overflow hole formed by a partition installed between the granular and sorption filters, and falls down, then enters the sorption filter, where it rises from the bottom up until it reaches the pipe for the removal of purified water located in the upper part of the sorption filter, while precipitation from the ters removed through nozzles for discharging sediments at the bottom of the bottom slopes to each filter. 2. The method according to p. 1, characterized in that crushed expanded clay is used as a granular filter load. 3. The method according to p. 1, characterized in that activated carbon is used as a sorption filter charge.

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