KR20200055191A - Non-discharge wastewater treatment using multi-step vacuum decompression evaporation concentration of high concentration wastewater - Google Patents

Abstract

A zero liquid-discharge wastewater treatment system using multistep vacuum evaporation concentration of high-concentration wastewater, and a method for the same according to the present invention relate to zero liquid-discharge treatment for treating pollutants contained in the wastewater in high concentrations, such as nutritive salts including nitrogen and phosphorus, by multistep vacuum evaporation and concentration. More specifically, the present invention is configured with processes of pre-treatment, evaporation concentration, and post-treatment in order to treat high concentrations of nutritive salts such as nitrogen and phosphorus, wherein in order to process organic matters or highly concentrated concentrates generated from each process, a crystallization process is included. Thus, the present invention minimizes the volume of solids finally obtained and reuses condensed water for the processes, thereby reducing the amount of water used and alleviating environmental pollution.

Description

Non-discharged wastewater treatment system using multi-stage vacuum evaporation concentration of high concentration wastewater {NON-DISCHARGE WASTEWATER TREATMENT USING MULTI-STEP VACUUM DECOMPRESSION EVAPORATION CONCENTRATION OF HIGH CONCENTRATION WASTEWATER}

The present invention relates to a non-discharged wastewater treatment system that treats high concentration contaminants in wastewater such as nutrient salts containing nitrogen and phosphorus using vacuum evaporation concentration, and more specifically, treatment of high concentration of concentrated water generated in various wastewater treatment processes. It relates to a non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high-concentration wastewater to increase reuse and reuse, and to minimize environmental pollution by high-concentration concentrated water.

In general, high-concentration pollutants containing nutrients such as nitrogen and phosphorus are contained in high concentration non-degradable wastewater such as industrial wastewater and livestock wastewater.

In the process of removing these contaminants, high-concentration concentrated water generated as a byproduct deteriorates the water quality in the treatment plant when it flows into the sewage treatment plant and affects the function of the sewage treatment facility, thereby lowering the treatment efficiency.

Accordingly, various studies have been conducted to increase the recovery rate of the concentrated water so that the concentrated water can be recycled as water for a wastewater treatment process or used as living water.

Korean Patent Registration No. 465885, "Evaporation and Concentration System for Wastewater / Wastewater" (2005.01.05) Korean Patent Publication No. 2016-26783, "Wastewater Treatment Method" (2016.03.09) Korean Patent Publication No. 2001-65008 "Reverse Osmosis System and Evaporation Concentration Method to Treat Landfill Leachate" (2001.07.11)

The present invention is to solve the above problems, through a multi-stage high-concentration reduced pressure evaporation and concentration process to efficiently recover and recover high-concentration concentrated water to be recycled as industrial water, and also reduce environmental problems caused by high-concentration concentrated water It is to provide a non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high-concentration wastewater.

In order to achieve the above object, a non-discharged wastewater treatment system using multi-stage vacuum evaporation of high concentration wastewater according to the present invention is pre-treated, concentrated by evaporation, and post-treated to remove nutrients containing nitrogen and phosphorus at high concentrations in the wastewater. And four stages of crystallization, which solves the problem caused by the scale occurring in each concentrator during high concentration through multi-stage concentration, that is, primary evaporation concentration and secondary evaporation concentration after primary heat exchange of wastewater. Concentrated water can be concentrated to 5% or less, and condensed water can be reused depending on the nature of the wastewater.

As described above, according to the present invention, the pre-treated wastewater is subjected to primary evaporation concentration and secondary evaporation concentration after heat exchange, followed by post-treatment, and concentrated to a high concentration of 5% or less of moisture content through crystallization in each process to finally It is possible to minimize the volume of solid content obtained by and reuse the condensed water in the process, thereby reducing the amount of water used and reducing environmental pollution.

In addition, it is possible to solve the scale problem occurring in the concentrator of each process in this process, and also has the advantage of being eco-friendly because no chemicals for preventing scale are used in each vacuum evaporation and concentration process.

1 is a view schematically showing a non-discharged wastewater treatment system according to the present invention.
Figure 2 is a schematic view showing a multi-stage evaporation concentrator of the present invention
Figure 3 is a view showing a pre-processing unit of the present invention
Figure 4 schematically shows the crystallization unit of the present invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings so that those skilled in the art to which the present invention pertains can easily implement the technical spirit of the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

1 is a view schematically showing a zero-discharge wastewater treatment system according to the present invention, and FIG. 2 is a view schematically showing a multi-stage evaporative concentration unit of the present invention.

According to the drawings, a non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high-concentration wastewater of the present invention decompresses wastewater to high concentration through multi-stage vacuum evaporation and concentration to remove contaminants containing nutrients such as high concentration nitrogen and phosphorus in the wastewater. It is concentrated and concentrated with 5% of highly concentrated concentrated water, and 95% is condensed with steam and reused as treated water, which treats sludge in wastewater and treats the total amount of ions in the concentrated water discharged from it. Pre-processing unit (1) for controlling within 1 to 2%; The supernatant treated from the pre-treatment unit is multi-stage evaporative concentration, that is, multi-stage evaporation and concentration to maximize the evaporation through primary low-pressure evaporation, and condensate and discharge the moisture content of the high-concentration wastewater to 5% or less through secondary high-vacuum decompression. (2); A post-processing unit (3) for filtering the condensate obtained by the multi-stage evaporation concentration unit through reverse osmosis to be usable as reused water; And a pre-treatment unit, a multi-stage evaporation concentration unit, and a crystallization unit 4 that crystallizes sludge / concentrated water discharged from the post-treatment unit to minimize the volume.

This will be described in detail as follows.

[1] preprocessing unit

The pretreatment unit 1 treats wastewater containing nutrient salts containing high concentrations of nitrogen and phosphorus, but separates and removes sludge solids such as suspended solids or organic substances in the wastewater by chemical aggregation and pressurized injury. It is a reaction tank that controls the concentration of 1 ~ 2%.

The pre-treatment unit 1 is a pressurized floating unit 11 for separating flocs obtained by adding flocculants by pressurized flotation, a sludge removing unit 12 for removing flocculent floats by using pressurized flotation, and organic substances remaining in the wastewater. It includes a microbubble tank 13 that oxidizes the back with microbubble ozone, and an electrolysis tank 14 that electrolyzes and removes dissolved organic compounds present in the wastewater, but this configuration is well known and detailed description is omitted. Shall be

[2] multistage evaporative concentrators

The multi-stage evaporation and concentration section 2 is a multi-stage evaporation and concentration so that the high concentration nutrient wastewater from which the sludge solids (floc) is removed in the pre-treatment section 1 is concentrated to 5% or less and evaporated more than 95%. The part 2 is composed of a first weak vacuum concentrator 10 and a second high vacuum concentrator 20.

Here, the first weak vacuum concentrating device 10 and the second high vacuum concentrating device 20 are vacuum evaporation concentrators equipped with the function of removing scale and foam, as described in the application number 2017-54143 filed by the present applicant. As an application of ", circulating pump (11,21), concentrator (12,22), gas-liquid separator (13,23), micro-bubble generators (14,24), steam recompressor (15,25) , Defoamer (16,26) and condenser (17,27) as a basic configuration.

The circulation pumps 11 and 21 are provided in the wastewater inlet pipe connected to the pre-treatment unit to supply wastewater to the inside of the concentrators 12 and 22, and to concentrate the concentrated liquid separated by the gas-liquid separators 13 and 23 described later as a concentrator. To cycle.

The concentrators 12 and 22 heat the wastewater supplied by the circulation pump by heat exchange and evaporate to condense the moisture in the wastewater while cooling and condensing the heated steam.

The gas-liquid separators 13 and 23 separate wastewater preheated in the concentrator into evaporated vapor and concentrated water in a vacuum.

The micro-bubble generators 14 and 24 are water-mill type and are installed between the circulation pump and the concentrator to supply microbubbles to prevent the generation of scale adhered inside the concentrator.

That is, when the wastewater is supplied to the concentrators 12 and 22 by the circulation pumps 11 and 21, the microbubbles are periodically injected, but the shock wave by the microbubbles is concentrated using the flow velocity and pressure of the wastewater transferred by the circulation pump. Remove the scale stuck inside and inside the connecting pipe.

These micro-bubble generators 14 and 24 are respectively installed at the front end of the concentrators 12 and 22 installed in the first and second concentrators constituting the multi-stage evaporative concentrator to divide the scale problem generated during heat exchange in each concentrator into two stages. By removing, the efficiency is increased, but the scale accumulated in the pipe is additionally removed by the shock wave generated by the microbubbles generated by the water-mill type non-power generators 14 and 24, and the scale is generated by lowering the frequency of the scale to reduce the operating efficiency of the device. And reduce the number of CIPs (Clean In Places) to reduce maintenance costs.

The defoamers 16 and 26 are installed at the rear end of the gas-liquid separator to remove a large amount of bubbles contained in the steam discharged from the gas-liquid separator in the process of being separated into steam and concentrated water in a vacuum state and return to the gas-liquid separator.

The steam recompressors 15 and 25 are installed at the rear end of the gas-liquid separator, and the evaporated steam from which bubbles have been removed is heated to heated steam by recompression and supplied to the concentrator again. At this time, the compressed air from the steam recompressors 15 and 25 functions as a saturated steam to heat up the temperature of wastewater circulating inside the concentrator by heat-exchanging all of the latent heat of the steam when entering the concentrator ().

The condensers 17 and 27 are connected to a concentrator (evaporator) so that the compressed steam flowing into the condenser passes through the steam recompressors 15 and 25 to be discharged as condensate. It consists of a structure through which the supplied cooling water passes.

As described above, the multi-stage evaporation concentrating unit 2 is composed of two stages, and each of the first weak vacuum concentrator 10 maximizes the amount of evaporation by controlling different vacuum concentration conditions, and the second high-vacuum concentrator ( In 20), it is concentrated to 95%.

In the drawings, reference numeral 18 is a heat exchanger.

[3] post-processing unit

The post-treatment unit 3 is a reaction tank that obtains 20% RO concentrated water by filtering the condensate condensed by the multi-stage evaporation concentration unit 2 to be used as reuse water, and a reverse osmosis device is used as the post-treatment unit.

[4] crystallization unit

The crystallization section 4 indirectly dried the sludge generated in the pre-treatment section 1, concentrated water evaporated by 95% or more by the multi-stage evaporation concentration section 2, and 20% RO concentrated water generated in the post-treatment section 3 It is a device that minimizes the volume by crystallization by a method (dry thin film).

The crystallization unit 4 is a cylindrical reactor 41 in which a crystallization target such as 5% high concentration concentrated water is inputted, and is arranged to surround the outside of the reactor and steam in the reactor to evaporate moisture contained in the concentrated water (heat source ) Is made of a heater (42) for supplying and a rotating body (43: impeller) that rotates concentrated water, installed inside the reactor, and sludge accumulated to a certain thickness on the inner wall of the rotating body by the heating rotation of the reactor is discharged to the outside. do.

That is, while the hot steam supplied by the heater (steam supply unit) makes contact with the wall surface of the reactor 41 where the concentrated water is stored and is dried, crystals can be generated on the wall surface, and the concentrated water is supplied by the impeller 43 installed therein. It is made to accumulate by falling down in a crystalline state, and this drying method has good drying efficiency, and can also perform powder drying by allowing metal ions, etc., contained in a trace amount in concentrated water to grow into crystals. It can be discharged by minimizing the volume of sludge / concentrated water, and depending on the application, the crystallized powder can be reused.

Next, a method of treating high concentration wastewater using a zero-discharge wastewater treatment system using multi-stage vacuum evaporation concentration according to the present invention will be described.

[1] pretreatment

First, pretreatment is performed to efficiently treat wastewater containing nutrient salts containing high concentration nitrogen and phosphorus.

In other words, the sludge in the wastewater is flocculated with a floc using a chemical (polymer flocculant) and then pressurized to the top to separate solids and remove solids contained in the high concentration wastewater to treat the solids concentration to 1% or less and remain organic in the wastewater The substances and volatile substances are oxidized with microbubble ozone to make them harmless, and by electrolysis, the scale-causing substances in the wastewater are stabilized with salt to minimize the induction of scale.

Accordingly, the concentration of total ions in the concentrated water is adjusted to be about 1 to 2%.

[2] multi-stage evaporative concentration

Subsequently, the wastewater (supernatant) from which solids have been removed through the pretreatment process is concentrated to a moisture content of 5% or less by multi-step evaporative concentration to obtain a highly concentrated nutrient wastewater.

① Primary weak vacuum concentration

The waste water from which solids have been removed is concentrated by evaporation at a vacuum degree of 500 mmHg and a temperature of 80 to 85 ° C. to perform 65 to 70% concentration.

That is, as shown in Figure 2, the wastewater supplied by the circulation pump 11 is microbubbled through the microbubble generator 14, and heat exchange is performed in the concentrator 12 according to the above conditions, and the gas-liquid separator 13 ) Is separated into liquid and steam, and the liquid is circulated together with the wastewater flowing through the circulation pump, and the steam is separated from the foam through the foam separator 16 and then at a temperature of 100 ° C. through the steam recompressor 15. Pressurized to 107 ° C and transferred to the concentrator 12 again, and exchanged with micro-bubble wastewater to be reused.

② Secondary high vacuum concentration

The wastewater evaporated about 65 ~ 70% through low pressure evaporation in the first weak vacuum concentration process and the process of ① in vacuum condition and lower temperature, ie, vacuum degree 700㎜Hg, temperature 65 ~ 70 ℃. It is concentrated by evaporation in the same manner and concentrated to 95% or more.

As described above, as the water content is evaporated and concentrated to remove more than 95% of the moisture content through the multi-stage evaporative concentration process, high-concentrated water (high-concentrated nutrient wastewater) is obtained.

In addition, the present invention performs concentration by dividing into a first weak vacuum concentration and a second high vacuum concentration as described above, which, when concentrated from the beginning to high vacuum, causes a large scale due to ions and solids contained in the wastewater. This is to prevent the rapid decrease in concentration efficiency, and accordingly, it is possible to remove the scale problem that occurs during vacuum evaporation and to concentrate at a high concentration.

[3] Post-treatment

Next, volatiles are removed using reverse osmosis (RO) filtration and ozone microbubble to reuse the condensed effluent in the multi-stage evaporative concentration process.

That is, the hot condensate generated during evaporation and concentration may be immediately re-used, but since volatile substances contained in high-concentration wastewater are COD-inducing substances, CO filtration is performed by performing RO filtration or oxidizing with microbubble ozone for approximately 10 minutes. By treating chromaticity or the like, it can be completely made harmless and reused.

In addition, about 20% of concentrated water may be generated during RO filtration using a reverse osmosis membrane, and the generated concentrated water can be sent to a crystallization process, which is a subsequent process, to be reprocessed to self-treat highly concentrated wastewater generated outside. .

[4] Crystallization: Indirect drying

In addition, the sludge / concentrated water generated in the pre-treatment, multi-stage evaporation concentration, and post-treatment processes is crystallized by an indirect drying method to lower the moisture content (minimize the volume).

That is, the sludge generated in the pre-treatment process, 95% or more concentrated concentrated water (highly concentrated nutrient wastewater) obtained through the multi-stage evaporative concentration process, and 20% RO concentrated water generated in the post-treatment process are introduced into the reactor and the reactor wall surface. When rotating while applying steam to the water, the moisture contained in the concentrated water forms a thin film on the wall, and drying is performed. When the film becomes more than a certain thickness on the wall, it falls down to the crystal state by the impeller inside the reactor and accumulates. Drain when dry. At this time, the dried product (crystallized powder) to be discharged is completely sterile dried.

As described above, the condensate obtained through the pre-treatment, multi-stage evaporation concentration, and post-treatment process can be reused in factories, etc., as it has almost the same water quality as the raw water, and these systems and methods include high-concentration wastewater, high-concentration washing wastewater, and thermal power. It can be applied to wastewater discharged from power plants or desulfurization scrubbers, concentrated water from RO processes for reuse of sewage treatment water, RO concentrated water from seawater desalination plants, food desalination wastewater, cutting oil wastewater from processing processes, and washing fluid wastewater from electroplating processes. .

DESCRIPTION OF SYMBOLS 1 Pre-processing part 2 Multi-step evaporation concentration part
3: post-processing unit 4: crystallization unit
10: 1st weak vacuum concentrator 20: 2nd high vacuum concentrator
11,21: Circulation pump 12,22: Concentrator (evaporator)
13,33: gas-liquid separator 14,24: micro-bubble generator
15,25: steam recompressor 16,26: defoamer
17,27: condenser

Claims (5)

A pre-treatment unit (1) for treating sludge in the wastewater and adjusting the total amount of ions of the concentrated water discharged therefrom to within 1 to 2%;
A multi-stage evaporation concentrating unit (2) for condensing and draining the supernatant treated from the pre-treatment unit under reduced pressure to a high concentration by vacuum evaporation concentration in two stages to a moisture content of 5% or less;
A post-processing unit (3) for filtering the condensed water obtained by the multi-stage evaporation concentration unit through reverse osmosis to be usable as reused water; And
Includes a crystallization unit (4) to minimize the volume by crystallization of the sludge / concentrated water discharged from the pre-treatment unit, the multi-stage evaporation concentration unit, and the post-treatment unit.
The multi-stage evaporation concentration unit (2) is a first weak vacuum concentrator (10) and a second high vacuum concentrator (20), characterized in that it consists of a multi-stage vacuum evaporation of high-concentration wastewater using a non-discharged wastewater treatment system. According to claim 1,
The first weak vacuum concentrator 10 and the second high vacuum concentrator 20,
Circulation pumps connected to the pre-treatment unit to supply and circulate wastewater (11,21);
A concentrator (12,22) for evaporating and concentrating the wastewater supplied by the circulation pump to evaporate moisture in the wastewater and cooling and condensing the heated steam;
A gas-liquid separator (13,23) for separating the wastewater preheated in the concentrator into evaporated steam and concentrated water in a vacuum;
A microbubble generator (14,24) installed between the circulation pump and the concentrator to supply microbubbles to prevent generation of scale adhered inside the concentrator;
A steam recompressor (15,25) installed at a rear end of the gas-liquid separator to heat the evaporated steam to heated steam by recompression and supply it to a concentrator; And
Non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high-concentration wastewater, characterized in that it comprises; condensers (17,27) connected to the condenser to condensate and discharge the compressed steam flowing through the steam recompressor. According to claim 2,
The first weak vacuum concentrator 10 is a multi-stage vacuum of high-concentration wastewater characterized in that it is configured to evaporate and concentrate the wastewater from which solids have been removed at a vacuum degree of 500 mmHg and a temperature of 80 to 85 ° C to perform 65 to 70% concentration. Effluent-free wastewater treatment system. According to claim 2,
The second high vacuum concentrator 20 is configured to perform 95% concentration by evaporating and condensing the reduced pressure evaporated wastewater through the first weak vacuum concentrator at a vacuum degree of 700 mmHg and a temperature of 65 to 70 ° C. Non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high concentration wastewater. The crystallization unit (4) according to claim 1,
A cylindrical reactor 41;
A heater 42 disposed to surround the outside of the reactor and supplying steam to the reactor to evaporate moisture contained in the concentrated water; And
Non-discharged wastewater treatment system using multi-stage vacuum evaporation and concentration of high-concentration wastewater, comprising; a rotating body (43) installed inside the reactor to rotate the concentrated water.

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