RU2749416C1 - Filter medium of water treatment plant - Google Patents

Abstract

FIELD: water treatment.

SUBSTANCE: invention relates to the field of water treatment, namely to purify water from contamination in water treatment plants of power plants, industrial and heating boilers and other industrial enterprises, as well as in the preparation of drinking water, in addition, to purify steam condensate, to purify waste water of various composition, and can be used as a filter medium in any mechanical clarifying filters to reduce the amount of suspended solids. The filter medium of the water treatment plant contains a layer of quartz sand and a layer of anthracite and additionally includes garnet sand with a fraction of 0.4-0.6 mm and a density of 2.8-4.2 g / cm³ as a lower filtering layer. The top layer of the filter medium is anthracite and the quartz sand is the middle layer of the filter medium. Anthracite is used in fractions of 0.8-1.6 mm with a density of 1.4-1.45 g / cm³, and quartz sand is used in fractions of 0.5-1.2 mm and a density of 2.0-2.7 g / cm³. The ratio of layers in the filter medium is at least: the top layer is 50-55%, the middle layer is 30-35% and the bottom layer is 5-15%.

EFFECT: increased filter performance and filter cycle duration, decreased wash water consumption with better filtrate quality.

1 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of water treatment, namely, to purify water from contamination in the circuit of water treatment plants of power plants, industrial and heating boilers and other industrial enterprises, as well as in the preparation of drinking water, in addition, to purify steam condensate, to purify waste water of various composition , and can be used as a filter media in any mechanical clarifying filters to reduce the amount of suspended solids.

Materials used as filter media in mechanical clarifying filters to reduce suspended solids are generally known.

These include materials such as anthracite (or hydroanthracite), quartz sand, expanded clay and other mechanically and chemically resistant materials. Filtering materials have different physical and chemical properties, which allows them to be used in filters as a filtering load not only individually, but also as part of a composition of two-, three- and multi-layer multimedia loads of one filter.

Such multimedia loading of filtering material allows increasing the dirt holding capacity of the filter (the amount of retained substances in kg per operating cycle per 1 m3 of filtering material), increasing the rate of water filtration through the filter, and improving the quality of the filtrate.

In addition, a multilayer filter bed in a mechanical filter can be made of materials of various sizes, stacked with a decreasing particle size from top to bottom so that in the upper part the particle size is largest and light, and at the bottom it is small and heavy. In this case, the porosity and, consequently, the dirt holding capacity of the upper layer is significantly increased, which contributes to an increase in the duration of the filtration cycle.

For example, the known filter material for water treatment filters according to the author's certificate of the USSR No. 267581, class. B01D 39/02, 1970, as which it is proposed to use the well-known building material expanded clay instead of quartz sand. This improves the quality of the filtrate and the performance of the filters, since expanded clay has a higher porosity, specific surface area and filtration coefficient.

The disadvantages of this filter material are its low efficiency, insufficient dirt holding capacity, and hence the low degree of purification.

Known filter material for water treatment filters according to the author's certificate of the USSR No. 639576, class. В01D 39/02, 1978, as which it is proposed to use burnt rocks. Crushed burnt rocks are used as aggregates for concrete, mortars and as materials for road construction.

However, in terms of their physicochemical properties and composition, burnt rocks are close to filtering materials such as quartz sand or expanded clay. The filter material from burnt rocks has high mechanical strength, good permeability and high efficiency, which makes it possible to increase the productivity of existing pumping and filtering stations by 1.5-2 times, and reduce the volume of capital investments by 1.5-2 times during the construction of new stations.

Due to the optimal geometric structure, developed surface area and high sorption capacity, the filter material from burnt rocks is universal. It is successfully used for purification of drinking and industrial water with a reduced amount of reagents or no reagents at all. The use of burnt rocks as a filtering material made it possible to solve the problem of treating industrial wastewater, highly concentrated in sediment, for example, mine water, sludge water from coal preparation, etc.

However, this filter material does not allow to sufficiently effectively purify the wash water, has a low filtration rate, which is insufficient for modern high-tech water treatment plants, and has a high turbidity of the filtrate at the filter outlet.

Known loading of a contact filter for natural water purification according to the patent of the Russian Federation No. 2238787, class. B01D 39/02, 2004 accepted by the applicant as a prototype. It contains a layer of quartz sand, in addition to which the loading additionally includes, as an upper layer, a filtering sorbent material - crushed flasks of modified ODM-2F grades with a grain size of 2.3-3.5 mm, as a middle layer - crushed anthracite with a grain size of 1, 5-2.3 mm, and the lower layer of quartz sand is used with a grain size of 0.7-1.5 mm with an equal ratio of components.

This load has a higher dirt holding capacity than similar analogues, as a result of which the duration of the filtration cycle is increased, which in turn helps to save clean water and energy required for washing the load.

In addition, when used in the composition of the loading of the material - crushed modified grades ODM-2F, which has higher adsorption properties than sand and anthracite, a deeper effect of water purification is noted according to the following indicators: hardness, calcium, sodium, chlorides, sulfates, dry residue, oil products.

However, this composition does not allow cleaning quickly enough and has a rather large consumption of wash water and an insufficient degree of purification.

The technical problem of filtering compositions of filters, including water treatment, is its influence on filter performance, filter cycle duration, wash water consumption, and the ability to purify water from fine impurities.

The problem posed is solved by the fact that, in contrast to analogues and prototype, in the proposed solution, the filter loading of the water treatment plant, containing a layer of quartz sand and a layer of anthracite, additionally includes garnet sand with a fraction of 0.4-0.6 mm and a density 2.8 -4.2 g / cm ³ , and the top layer of the load is anthracite, and quartz sand is the middle layer of the load, while anthracite uses fractions of 0.8-1.6 mm with a density of 1.4-1.45 g / cm ³ , and quartz sand is used fractions with a size of 0.5-1.2 mm and a density of 2.0-2.7 g / cm ³ .

In addition, the ratio of layers in the filter loading is at least: top layer 50-55%, middle layer 30-35% and bottom layer 5-15%.

The technical result from the use of the proposed solution, thanks to the use of crushed garnet sand, is to increase the filter performance and the duration of the filter cycle, to reduce the consumption of wash water with a better quality of the filtrate.

The drawing schematically shows a multilayer loading in a mechanical clarifying filter "FOMZ" (clarifying filter with multimedia loading) of a water treatment plant.

The filtering load is a vertical three-layer filling: the lower filtering layer 1, the middle filtering layer 2 and the upper filtering layer 3. In the volume of the filter in its lower part under the lower filtering layer 1 there is a bedding layer 4, and free space 5 is also left, this is 30- 50% of the total filter volume for expansion of the filter material during backwashing or backwashing.

It is necessary to use pomegranate sand as a filtering layer in conjunction with a bedding layer 4, which is made, for example, of gravel with a layer thickness of 15-20 cm, to prevent abrasion of the filtering elements of the lower filter distributor.

Such a three-layer multimedia loading of filtering material allows increasing the dirt holding capacity of the filter (the amount of retained substances in kg per operating cycle per 1 m of filtering material), increasing the rate of water filtration through the filter, and improving the quality of the filtrate by the amount of suspended solids in the water. Filters with multimedia loading can be used in technological water purification schemes, where high requirements are imposed on the quality of water in terms of the content of suspended solids. For example, in front of reverse osmosis plants or ion exchange plants operating according to the countercurrent technology of water purification and desalination.

And also the proposed three-layer filtering load is made of materials of various sizes, stacked with a decreasing size from top to bottom so that in its upper part the particle size is greatest. In this case, the porosity and, consequently, the dirt holding capacity of the upper layer is significantly increased, which contributes to an increase in the duration of the filtration cycle.

In addition, the mechanical clarifying filter of the water treatment plant is loaded in layers with materials that not only differ in size, namely, in size, but also in density from top to bottom. Namely, the upper layer is made of a material of larger size and lower density - a light material, and the lower layer is made of a material of smaller size and higher density - a heavy material.

Therefore, in order to achieve the set technical result, crushed pomegranate sand with a fraction of 0.4-0.6 mm and a density of 2.8-4.2 g / cm ³ is proposed as the lower heavy layer of the filtering load.

In this case, the upper light layer of the filtering charge is anthracite with a fraction of 0.8-1.6 mm and a density of 1.4-1.45 g / cm ³ , which is much lighter and larger than the crushed fraction of garnet sand. And quartz sand, which is part of the filter media, makes up the middle layer of the media. It is used with a size of 0.5-1.2 mm and a density of 2.0-2.7 g / cm ³ .

A significant difference in the density of the granules of filtering materials also makes it possible to create loads in filters with a size decreasing in the direction of flow of the treated water. It is important to note that, thanks to the use of filter media for filter loading of different bulk density and an increase in the porosity of the upper layers, it is possible to achieve uniformity of operation of the entire thickness of the loading.

Moreover, the ratio of layers in a three-layer filter load is, for example: the upper layer is about 50-55% of the entire load with light material, the middle layer is about 30-35% with a material with medium density and the bottom layer is about 5-15% with material with a high density.

Water purification in a mechanical clarifying filter with a multilayer loading of a water treatment plant is as follows.

The water coagulated in clarifiers for further additional purification is fed to mechanical filters with the direction of the flow of purified water from top to bottom.

First, water is filtered and clarified (cleaning from suspended solids). When the pressure drop of the purified water reaches 0.1 MPa on the filter, or when the content of suspended solids in the filtrate increases, or when a certain amount of clarified water per filter cycle is reached, the filter is turned off. And then they switch it to regeneration, that is, to flush and remove substances trapped in it. Flushing is carried out with a reverse flow of water "from the bottom up". An intensive flow of flushing water lifts up the filter material of the load layer by layer, loosens it, transferring it into a suspended state. The filter material of each layer moves in a stream of water, colliding with each other and being cleared of adhered suspended matter. Such intensive flushing ensures that sediments, suspended solids and impurities are washed out from the filter material, but not the removal of the filter material itself.

After backwashing, carried out by the reverse flow of water "from the bottom up", the filter material due to the difference in density is distributed along the height of the filter while maintaining the original layer-by-layer loading, is deposited under the action of gravitational forces, thereby restoring the filtering properties of the filter. The first is laid on the bedding layer 4, the lower layer 1 of garnet sand, as heavier and finer, then the middle layer 2 of quartz sand is laid on the lower layer 1, and the last is the upper layer 3 of anthracite, as lighter and larger, on the middle 2 and bottom 1 layers.

Therefore, in order to prevent mixing of layers of filtering material of different sizes during backwashing, the material in each of the layers must be heterogeneous, suitable in terms of bulk weight, density and other technical characteristics for a particular water filtration unit.

To increase the efficiency and economy of the mechanical filtration process, the applicant proposed to use crushed garnet sand of a fraction with a size of 0.4-0.6 mm and a density of 2.8-4.2 g / cm ³ as the lower layer of a multimedia load. It has a number of advantages. So, as a result of backwashing, its particles with a high specific gravity and small size are distributed in the lower part of the filter media and form a so-called fine cleaning zone, which allows water to be purified from fine impurities. While larger particles of other filtering material (anthracite, sand) are located in the upper layers of the load. Due to this, the most complete removal of suspended mechanical particles of various sizes is achieved.

Garnet sand is a chemically inactive, non-metallic natural mineral that does not pollute the environment and working conditions. Garnet sand is an extremely tough (see table below) and heavy material. The hardness of garnet sand is related to its crystalline structure, which provides high resistance to fracture. Thanks to this ability, garnet sand is virtually wear-resistant over its entire life cycle.

In terms of filtering properties, garnet sand is very close to quartz sand, but somewhat surpasses it in mechanical strength to abrasion, chemical resistance and porosity of the layer. Its use in multilayer filters in combination with other materials increases productivity, dirt holding capacity and cleaning efficiency.

The table shows comparative data on quality characteristics.

In the case of industrial application of the proposed loading in mechanical filters of water treatment plants, the following ratio of layers is recommended: with a three-layer loading, the upper layer is about 50-55% - light material, the middle layer is about 30-35% - material with an average density, the bottom layer is about 5-15% - high density material.

The use of the proposed technical solution made it possible to increase the filter productivity and the duration of the filter cycle, to reduce the consumption of wash water with a better quality of the filtrate.

Namely, the use of crushed pomegranate sand made it possible to increase the productivity of the filters and the duration of the filtration cycle, to reduce the consumption of wash water with a better quality of the filtrate.

The filtration rate on filters loaded with pomegranate sand is 30-50% higher than that of other filter media, which makes it possible to increase the productivity of the filtration unit accordingly.

The use of pomegranate sand allows you to reduce the dose of the applied coagulant in clarifiers, which saves reagents.

The duration of the filtration cycle when using garnet sand is 15-30% higher, which reduces the consumption of flushing water.

In general, the proposed filtering load in the FOMZ filter has the following advantages:

• high flow rate during filtration;

• the ability to use as part of combined downloads for multimedia filters;

• has a long service life of the material due to the high strength of the particles;

• increases the degree of water purification from fine impurities;

• has increased dirt holding capacity.

Claims (2)

1. Loading a filter of a water treatment plant containing a layer of quartz sand and a layer of anthracite, characterized in that the loading additionally includes garnet sand with a fraction of 0.4-0.6 mm and a density of 2.8-4.2 g / cm ³ , and the upper layer of the load is anthracite, and quartz sand is the middle layer of the load, while anthracite uses fractions 0.8-1.6 mm in size with a density of 1.4-1.45 g / cm ³ , and quartz sand uses fractions size 0.5-1.2 mm and density 2.0-2.7 g / cm ³ . 2. Loading according to claim 1, characterized in that the ratio of layers in the filter loading is at least: the top layer is 50-55%, the middle layer is 30-35% and the bottom layer is 5-15%.

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