CN112028348A - Zero-emission treatment method and device for high-salinity wastewater - Google Patents

Zero-emission treatment method and device for high-salinity wastewater Download PDF

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CN112028348A
CN112028348A CN202010830204.3A CN202010830204A CN112028348A CN 112028348 A CN112028348 A CN 112028348A CN 202010830204 A CN202010830204 A CN 202010830204A CN 112028348 A CN112028348 A CN 112028348A
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reverse osmosis
salt
electrodialysis
unit
ozone
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CN112028348B (en
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许昌相
刘小冕
王丹
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Beijing Yu Tao Environmental Engineering Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention relates to a zero discharge treatment method and a device for high-salinity wastewater, wherein the method comprises the following steps: deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method; performing reverse osmosis desalination on effluent after electrochemical hardness and organic pollutants removal, and recycling fresh water after reverse osmosis desalination; carrying out catalytic ozonation on the reverse osmosis concentrated water; and (4) carrying out salt separation and recovery on the effluent after the catalytic oxidation of ozone. The zero-emission treatment method for the high-salinity wastewater, provided by the invention, utilizes an electrochemical method to deeply remove hardness, and compared with the traditional resin softening method, the method avoids secondary discharge of resin backwashing waste liquid, degrades partial organic matters while deeply removing hardness, and greatly reduces the membrane pollution problem of subsequent reverse osmosis.

Description

Zero-emission treatment method and device for high-salinity wastewater
Technical Field
The invention belongs to the technical field of wastewater treatment, particularly relates to a high-salinity low-organic-matter recycling zero-emission treatment technology, and particularly relates to a high-salinity wastewater zero-emission treatment method and device.
Background
3/4 covering the ground with water, wherein fresh water accounts for about 2.53%, and more than 60% of the fresh water on the ground is insufficient; the average water resource of China is 1/4 in the average level of the world, and the water quantity is seriously insufficient.
The high-salinity wastewater refers to wastewater with the total salt content of at least 1 percent, and is mainly from chemical plants, petroleum and natural gas collection and processing and the like. High salt wastewater is harmful: 1) leading to high osmotic pressure of the water body and causing dehydration and death of microbial cells; 2) the activated sludge is easy to float and run off, so that the purification effect of a biological treatment system is seriously influenced; 3) the mineralization degree of the water quality of the river is improved, and soil is hardened; 4) causing corrosion of the pipeline and causing the water body to generate malodorous gas.
The high-salinity wastewater recycling treatment mainly comprises two technologies, namely a membrane separation technology and a thermal evaporation technology. The mode of directly adopting the thermal evaporation technology to obtain the reuse water from the high-salinity wastewater has huge energy consumption, so the membrane separation technology is the mainstream technology in the field. The membrane separation technology mainly comprises ultrafiltration, nanofiltration, reverse osmosis, electrodialysis and the like, and can adopt one membrane technology or a combination of membrane technologies to treat wastewater from different sources. The key technical problem of the application of the membrane technology is the problem of membrane pollution, and the components of the wastewater are complex, so that the membrane has great influence on the service efficiency and the service life, and even can not be reversed. Some existing combination techniques can achieve higher recycled water yield, but do not solve the problems of membrane fouling and membrane lifetime.
The aim of the high-salinity wastewater treatment technology is zero discharge of wastewater, which needs to recover salt in the wastewater in a solid form, and salt meeting the selling quality standard is difficult to obtain due to complex salt components in the wastewater. The existing method obtains more mixed salt, is difficult to sell and use, and forms solid waste which is difficult to treat.
The prior art discloses a zero discharge treatment method and a device for coal chemical industry wastewater, NaOH and Na are added into the water produced by iron-carbon micro-electrolysis2CO3Precipitating calcium and magnesium in the high-salinity wastewater, ultrafiltering and nanofiltering the obtained wastewater, and sending the nanofiltered concentrated solution to evaporation crystallizationAnd the nanofiltration fresh water is sent into reverse osmosis, and the reverse osmosis concentrated solution is sent into a second evaporator for evaporation and crystallization. The method adopts the addition of NaOH and Na2CO3Namely, the hardness is removed by a medicament method, and the introduced salt is not beneficial to recycling; secondly, the salt recovery section of the method adopts an evaporative crystallization method, the purity of the produced salt is not high, the salt is difficult to sell or use, and the energy consumption is high.
The prior art also discloses a zero-discharge treatment method system for high-salt-content wastewater in coal chemical industry, wherein the hardness removal adopts a microfiltration hardness removal system and an ion exchange system, and after the ion exchange operation is saturated, acid and alkali regeneration is needed, so that secondary pollution is easily generated.
The main steps of the method are that firstly, pretreatment is carried out, the pretreated effluent is subjected to reverse osmosis treatment, the reverse osmosis concentrated water is oxidized by Fenton, the Fenton effluent is subjected to biochemical treatment, then electrodialysis concentration is carried out, and finally, cyclic crystallization is carried out. The reverse osmosis concentrated water is treated by Fenton oxidation (hydrogen peroxide and ferrous sulfate), acid and alkali are required to be adjusted in the reaction process, a lot of salt is introduced, the recycling is not facilitated, and secondary pollution of iron mud is easily caused. Secondly, the salt recovery section of the method adopts an evaporative crystallization method, the purity of the generated salt is not high, the salt is difficult to sell or use, the operating cost of the evaporative crystallization is 60-70 yuan/ton of water, and the energy consumption is high.
Disclosure of Invention
In view of the above, the main object of the present invention is to provide a method and a device for zero discharge treatment of high salinity wastewater, which solve the problems of secondary discharge of backwash liquid and use of chemical agent caused by traditional resin hardness removal or chemical agent hardness removal, degrade part of organic matters while deeply removing hardness, greatly reduce the pollution problem of the subsequent reverse osmosis membrane, realize the recycling of salt, increase the additional value of salt, and protect and recycle the whole method.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The invention provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps of:
a, deeply removing hardness and organic pollutants from high-salinity wastewater by an electrochemical method;
b, performing reverse osmosis desalination on the effluent after electrochemical hardness and organic pollutant removal, and recycling fresh water after reverse osmosis desalination;
c, carrying out catalytic ozonation on the reverse osmosis concentrated water;
d, performing salt separation and recovery on the effluent after the catalytic oxidation of the ozone.
The purpose of the invention and the technical problem to be solved are further realized by adopting the following technical scheme.
Further, in the method for zero emission treatment of high-salinity wastewater, in step a, the high-salinity wastewater is wastewater containing salt with a mass fraction of more than 1%, the wastewater contains sodium salt, calcium salt and magnesium salt, the sodium salt is at least one selected from sodium sulfate and sodium chloride, and the content of the sodium salt accounts for more than 90% of the total mass of the sodium salt, the calcium salt and the magnesium salt.
Further, in the method for zero emission treatment of high-salinity wastewater, in step a, the parameters of the electrochemical method are set as follows, and the current density is 5-30mA/cm2The retention time is 5-30 min.
Further, in the step b, the reverse osmosis desalination adopts one-stage high-pressure reverse osmosis or two-stage low-pressure reverse osmosis, the operating pressure of the high-pressure reverse osmosis is 2.8-4.2MPa, and the operating pressure of the low-pressure reverse osmosis is 1.4-2.0 MPa.
Further, in the aforementioned zero-emission treatment method for high-salinity wastewater, in step c, the parameters of the catalytic oxidation by ozone are set as follows: the selected ozone catalyst is a supported mesoporous activated carbon catalyst; the concentration of ozone and CODCrThe concentration ratio is (1.2-1.5) to 1 (mg/L); the water inlet parameters of the ozone catalytic oxidation are as follows, wherein Cl is more than 0-:CODCrLess than 15:1(mg/L), the pH value is 6-9, and the retention time is 30-90 min; the ratio of the ozone catalyst to water is 0.5:1-1:1 (v/v).
Further, in the method for zero emission treatment of high-salinity wastewater, in step c, the supported mesoporous activated carbon catalyst comprises a carrier and an active component; the carrier is mesoporous spherical activated carbon with the diameter of 3-5mm, and the active component is transition metal oxide; the transition metal oxide is selected from at least one of manganese dioxide, copper oxide, nickel oxide and cobalt oxide; the mass ratio of the carrier to the active component is (90-93): (7-10).
Further, in the zero-emission treatment method of the high-salinity wastewater, in the step c, the pH value of the inlet water subjected to catalytic oxidation by ozone is 6-9, and Cl is more than 0-:CODCrLess than 15:1(mg/L) and the retention time is 30-90 min.
Further, in the zero emission treatment method of the high salinity wastewater, in the step c, the concentration of the ozone is 80-100 mg/L.
Further, in the zero discharge treatment method of high-salinity wastewater, when the salt is sodium chloride, the salt separation and recovery in step d specifically includes:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali.
Further, in the zero discharge treatment method of high-salinity wastewater, when the salt is sodium sulfate, the salt separation and recovery in step d specifically includes:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and (4) carrying out salt separation conversion on the electrodialysis concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
Further, in the aforementioned zero discharge treatment method for high-salinity wastewater, when the salt includes sodium sulfate and sodium chloride, the salt separation and recovery in step d specifically includes:
carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
subjecting the nanofiltration fresh water to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali;
and (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
Further, the zero discharge treatment method of the high salinity wastewater is described, wherein the electrodialysis current density is 20-70mA/cm2(ii) a The bipolar membrane electrodialysis has current intensity of 2-4A, voltage of 15-40V, and current density of 20-100mA/cm2The retention time is 30-90 min; the pressure of concentrated water, polar water and fresh water of the bipolar membrane electrodialysis is 0.01-0.02 MPa; the total amount of the water inflow soluble solid of the bipolar membrane electrodialysis is 80000-120000 mg/L.
Further, the high-salinity wastewater zero-emission treatment method is characterized in that the operating pressure of the nanofiltration is 0.5-1.0 MPa.
Further, in the zero discharge treatment method of high-salinity wastewater, the salt separation conversion specifically includes: introducing excessive ammonium carbonate into the sodium sulfate solution to perform double decomposition reaction to generate ammonium sulfate, sodium carbonate or sodium bicarbonate; the molar ratio of the ammonium carbonate to the sodium sulfate is more than or equal to 5: 1.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. According to the zero-emission treatment device for the high-salinity wastewater provided by the invention, the zero-emission treatment device comprises an electrochemical unit, a reverse osmosis unit, an ozone catalytic oxidation unit and a salt separation recovery unit which are independently fixed on a steel structure frame to form a whole and are sequentially connected.
Further, in the zero-emission treatment device for high-salinity wastewater, the salt separation and recovery unit comprises an electrodialysis unit, and an outlet of the electrodialysis unit is connected with the bipolar membrane electrodialysis unit and the reverse osmosis unit.
Further, the zero-emission treatment device for high-salinity wastewater further comprises a PLC control unit which is respectively connected with the electrochemical unit, the reverse osmosis unit, the ozone catalytic oxidation unit, the electrodialysis unit and the bipolar membrane electrodialysis unit and is fixed on the steel structure frame.
Further, in the zero-emission treatment device for high-salinity wastewater, the salt separation recovery unit includes an electrodialysis unit, and an outlet of the electrodialysis unit is connected with a salt separation conversion unit and a reverse osmosis unit.
Further, the zero-emission treatment device for high-salinity wastewater further comprises a PLC control unit which is respectively connected with the electrochemical unit, the reverse osmosis unit, the ozone catalytic oxidation unit, the electrodialysis unit and the salt separation conversion unit and is fixed on the steel structure frame.
Further, in the zero-discharge treatment device for high-salinity wastewater, the salt separation recovery unit comprises a nanofiltration unit, and an outlet of the nanofiltration unit is connected with an electrodialysis unit and a salt separation conversion unit; the outlet of the electrodialysis unit is connected with a bipolar membrane electrodialysis unit and a reverse osmosis unit.
Furthermore, the zero-emission treatment device for high-salinity wastewater further comprises a PLC control unit which is respectively connected with the electrochemical unit, the reverse osmosis unit, the ozone catalytic oxidation unit, the nanofiltration unit, the electrodialysis unit, the bipolar membrane electrodialysis unit and the salt separation conversion unit and is fixed on the steel structure frame.
Further, the aforementioned zero-emission treatment device for high-salinity wastewater, wherein the electrochemical unit may be selected from electrochemical reactors in the prior art; the reverse osmosis unit comprises a first reverse osmosis subunit and a second reverse osmosis subunit, and the first reverse osmosis subunit and the second reverse osmosis subunit both comprise a plurality of reverse osmosis membranes; the ozone catalytic oxidation unit comprises an ozone generating device and a catalytic tower, the ozone generating device comprises an oxygen generating device and an ozone generator, the oxygen generating device is connected with the ozone generator, and the ozone generating device is connected with the catalytic tower through a pipeline; the nanofiltration unit is selected from a plurality of nanofiltration membranes; the electrodialysis unit is selected from electrodialysis equipment; the bipolar membrane electrodialysis unit is selected from electrodialysis equipment; the salt separation conversion unit is selected from a closed tank.
Compared with the prior art, the zero-discharge treatment method and device for high-salinity wastewater have the following beneficial effects:
1. according to the zero-emission treatment method for the high-salinity wastewater, disclosed by the invention, hardness is deeply removed and organic pollutants are degraded by using an electrochemical method, compared with the traditional resin softening or medicament softening, the secondary discharge of resin backwashing waste liquid and the use of a medicament are avoided, partial organic matters are degraded while hardness is deeply removed, the pollution problem of a subsequent reverse osmosis membrane is greatly reduced, and the service life of the reverse osmosis membrane is prolonged;
2. the effluent hardness of the high-salinity wastewater treated by the method is less than 30mg/L, the removal rate of calcium and magnesium ions is more than 90 percent, and the removal rate of organic matters is 5-35 percent; the recovery rate of fresh water is more than 88%, the concentration of acid and alkali prepared by bipolar membrane electrodialysis is 4-8%, the sodium carbonate can be used for resin regeneration, the purity of the sodium carbonate is more than 97%, the sodium carbonate can be used by oneself or sold, the ammonium sulfate nitrogen content is more than 20.5%, and the requirement of qualified products of the ammonium sulfate national standard GB535-1995 is met.
3. The invention realizes zero discharge of high-salinity wastewater, simultaneously prepares the sodium chloride mixed salt into acid and alkali, converts the sodium sulfate into a large amount of chemical raw materials such as sodium carbonate or sodium bicarbonate, and uses the ammonium sulfate as a fertilizer, thereby realizing the recycling of waste salt and solving the problem that the traditional evaporative crystalline sodium sulfate can not be utilized.
The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.
Drawings
FIG. 1 is one of the schematic views of the high-salinity wastewater zero-discharge treatment apparatus of the present invention;
FIG. 2 is a second schematic view of the high-salinity wastewater zero-discharge treatment apparatus according to the present invention;
FIG. 3 is a third schematic view of the high-salinity wastewater zero-discharge treatment apparatus of the present invention;
FIG. 4 is a fourth schematic view of the high-salinity wastewater zero-discharge treatment apparatus according to the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be made on the specific implementation, features and effects of a method and an apparatus for zero discharge treatment of high salinity wastewater according to the present invention with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features or characteristics of one or more embodiments may be combined in any suitable manner.
The technicians in the field can carry out routine adjustment according to the water quality to obtain the optimal control conditions of different water qualities, so that each unit meets the requirements of the controlled effluent water quality and the optimal method effect is realized.
The following materials or reagents, unless otherwise specified, are all commercially available.
The invention further details a zero-emission treatment method of the high-salinity wastewater, which comprises the following steps:
a, deeply removing hardness and organic pollutants from high-salinity wastewater by an electrochemical method;
the high-salinity wastewater is wastewater with the salt content of more than 1 percent by mass, and the high-salinity wastewater is wastewater with the salt content of more than 1 percent by mass (such as wastewater containing Cl)-、SO4 2-、Na+、Ca2+And the like), the wastewater contains sodium salt, calcium salt and magnesium salt, the sodium salt is selected from at least one of sodium sulfate and sodium chloride, the content of the sodium salt accounts for more than 90 percent of the total mass of the sodium salt, the calcium salt and the magnesium salt, and in addition, a small amount of organic pollutants (such as phenols, benzene and derivatives thereof, pyridine and the like) are also contained.
The parameters of the electrochemical method are set as follows, and the current density is 5-30mA/cm2The retention time is 5-30 min; the current density is preferably 10-15mA/cm2The preferred residence time is 10-15min, and the range ensures the descaling rate and simultaneously has low energy consumption.
The hardness of effluent after deep hardness removal and organic pollutant removal by the electrochemical method is less than 30mg/L, the removal rate of calcium and magnesium ions is more than 90%, and the removal rate of organic matters is 5-30%.
The step a is mainly to remove calcium and magnesium ions in the water by an electrochemical method and pre-degrade organic matters in the waterA compound (I) is provided. The principle is as follows: the water dissociates near the cathode to form a high concentration of hydroxyl radicals, and the Ca in the water is present in such high pH environments (up to pH 13)2+(aq)、Mg2+(aq) ions form Ca (OH)2、Mg(OH)2And CaCO3And precipitating, namely: cathode hardness removal process; ozone (O) generated by OH generated by discharging water molecules on the surface of the anode3) Hydroxyl radical (HO), active oxygen free radical (O), hydrogen peroxide (H)2O2) Forming a composite oxidant, degrading or mineralizing organic matters in the wastewater, and realizing electrochemical pre-degradation treatment of the organic matters. Ca2+、Mg2+The presence of ions at the same time increases the degree of membrane fouling, and calcium ions increase the lethality of the organic fouling layer.
b, performing reverse osmosis desalination on the effluent after electrochemical hardness and organic matter removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts one-stage high-pressure reverse osmosis or two-stage low-pressure reverse osmosis, the operating pressure of the high-pressure reverse osmosis is 2.8-4.2MPa, and the operating pressure of the low-pressure reverse osmosis is 1.4-2.0 MPa.
After the first-stage high-pressure reverse osmosis or the two-stage low-pressure reverse osmosis separation, the Total Dissolved Solids (TDS) of the reverse osmosis concentrated water can reach 50000mg/L, and CODCrIs 150-200 mg/L.
c, carrying out catalytic ozonation on the reverse osmosis concentrated water;
the reverse osmosis concentrated water mainly comprises sodium chloride, sodium sulfate and organic pollutants. The parameters of the catalytic oxidation of ozone are set as follows: the selected ozone catalyst is a supported mesoporous activated carbon catalyst, the loss rate of the supported mesoporous activated carbon catalyst is less than 3 percent per year, the catalyst is replaced once in 5 years, and the ozone concentration and the COD (chemical oxygen demand) areCrThe concentration ratio is (1.2-1.5): 1(mg/L), preferably 1.4:1(mg/L), which is favorable for reducing CODCrThe concentration of (c). The ratio of the ozone catalyst to the feed water is 0.5:1 to 1:1(v/v), preferably 0.7:1, which preferably helps to improve the catalytic efficiency of the catalyst. The pH value of the inlet water of the ozone catalytic oxidation is 6-9,0＜Cl-:CODCrless than 15:1(mg/L), the retention time is 30-90min, the concentration of the ozone is 80-100mg/L, and the COD is obtained by catalytic oxidation of the ozoneCr30-80% of degradable; preferably, the pH value of the inlet water is 7, Cl-:CODCrThe retention time is 60min and the concentration of the ozone is 100mg/L, so that the COD after catalytic oxidation by ozone is preferredCr75% of degradation, and the ozone energy consumption and the operation cost are more reasonable.
The supported mesoporous activated carbon catalyst comprises a carrier and an active component; the carrier is mesoporous spherical activated carbon with the diameter of 3-5mm, the active component is transition metal oxide, the transition metal oxide is at least one selected from manganese dioxide, copper oxide, nickel oxide and cobalt oxide, and the combination of manganese dioxide, copper oxide, nickel oxide and cobalt oxide is preferred; the catalytic effect of the multi-component is better than that of a single component, and under a proper proportion, a rule that the ternary component is better than the binary component and the binary component is better than the monobasic component is provided, which is related to the synergistic effect formed by different physicochemical properties of the multi-component metal oxide. The mass ratio of the carrier to the active component is (80-93): (7-10), preferably (90-93): (7-10), more preferably 93:7, under specific conditions, the loading amount of the active ingredients of the catalyst has a proper value, and the loading amount is lower or higher than the proper value, so that the specific surface area of the catalyst, the adsorption of ozone and pollutants on the catalyst and the like are influenced, and the catalytic capability is reduced; this is preferred to facilitate the catalytic ability of the catalyst.
When the active component is selected from the combination of manganese dioxide, copper oxide, nickel oxide and cobalt oxide, the preparation method of the supported mesoporous activated carbon catalyst comprises the following steps:
a1 placing the mesoporous spherical activated carbon in anhydrous nickel acetate (Ni (CH)3COO)2) Anhydrous copper acetate (Cu (CH)3COO)2) Cobalt acetate (Co (CH)3COO)2) Manganese acetate ((CH)3COO)2Mn) for 20-24h to obtain a mixed solution;
b1, air-drying the mixed solution obtained in the step a1 at normal temperature for 24-28h to obtain a semi-finished catalyst product;
c1, roasting the catalyst semi-finished product obtained in the step b1 in a resistance furnace at 1200-1400 ℃ for 6-8 hours under the nitrogen atmosphere, forming, and naturally cooling to the normal temperature.
Wherein, in the step a1, the anhydrous nickel acetate (Ni (CH)3COO)2) Anhydrous copper acetate (Cu (CH)3COO)2) Cobalt acetate (Co (CH)3COO)2) Manganese acetate ((CH)3COO)2Mn) is (1.4-4.5) to (1-3): (1-3): (1-2); 2:1:2:1 is preferred, so that the catalytic capability of the preferred post-catalyst is further improved, and COD (chemical oxygen demand) subjected to catalytic oxidation by ozone can be further improvedCrCan be degraded by 80 percent.
And c, degrading organic matters in the reverse osmosis concentrated water through ozone catalytic oxidation, wherein the existence of the organic matters can aggravate the subsequent membrane pollution and influence the performance and the service life of the membrane, so that the membrane must be degraded to the maximum extent.
When the salt is sodium chloride, the salt separation recovery in step d may specifically include:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali.
When the salt is sodium sulfate, the salt separation recovery in step d may specifically include:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and (4) carrying out salt separation conversion on the electrodialysis concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
When the salt includes sodium sulfate and sodium chloride, the salt separation recovery in step d may specifically include:
carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
subjecting the nanofiltration fresh water to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali;
carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate; the fresh water is sodium chloride, and the concentrated water is sodium sulfate.
The operating pressure of nanofiltration is 0.5-1.0 MPa; the yield of fresh water and concentrated water of the nanofiltration membrane can be controlled by adjusting the water inlet pressure of the nanofiltration membrane. The main purpose of nanofiltration is to separate monovalent ions and divalent ions, and after passing through a nanofiltration membrane, the nanofiltration fresh water is monovalent salt NaCl, and the nanofiltration concentrated water is divalent salt Na2SO4；
The current density of the electrodialysis is 20-70mA/cm2(ii) a The bipolar membrane electrodialysis has current intensity of 2-4A, voltage of 15-40V, and current density of 20-100mA/cm2The retention time is 30-90 min; the pressure of concentrated water, polar water and fresh water of the bipolar membrane electrodialysis is 0.01-0.02 MPa. The bipolar membrane electrodialysis has the current intensity of 2.5-3.0A and the current density of 30-50mA/cm2The residence time is preferably 50-60min, and the current efficiency and the energy consumption in the range are higher.
After electrodialysis concentration, the TDS of the concentrated water can reach 150000mg/L, the recovery rate of fresh water is more than 85 percent, and the COD isCrLess than 50mg/L for bipolar membrane acid-base regeneration; the electrodialyzed fresh water enters the front reverse osmosis, NaCl in the nanofiltration fresh water contains certain impurities and can pollute an ionic membrane when being used for preparing sodium hypochlorite or chlorine dioxide by the electrolysis of the ionic membrane, so that the NaCl is further concentrated by the electrodialyzing and is prepared into acid and alkali with the concentration of 6-8 wt% by the electrodialysis of a bipolar membrane;
bipolar membrane principle: under the action of DC electric field, the bipolar membrane can convert H into H2O ionization to H+And OH-. By utilizing the characteristic, the bipolar membrane electrodialysis system formed by combining the bipolar membrane and other anion-cation exchange membranes can convert the salt in the aqueous solution into corresponding acid and alkali without introducing new components.
And (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
The main component of the nanofiltration concentrated water is Na2SO4，Na2SO4The market is limited, so sodium sulfate is converted to sodium carbonate or bicarbonate. The salt separation conversion specifically comprises: introducing excessive ammonium carbonate into the sodium sulfate solution to generate ammonium sulfate, sodium carbonate or sodium bicarbonate, wherein carbonate ions and ammonium ions interact to promote hydrolysis to generate ammonia water and bicarbonate radicals or carbonic acid, and carrying out double decomposition reaction; the molar ratio of the ammonium carbonate to the sodium sulfate is more than or equal to 5: 1; the purity of the obtained sodium carbonate is more than 97%, the nitrogen content of the obtained ammonium sulfate is more than 20.5 wt%, and the requirement of qualified products of the ammonium sulfate national standard GB535-1995 is met.
The operation of the steps is controlled by a PLC (programmable logic controller), specifically, the steps comprise: operation of each pump, reverse osmosis membrane backwashing, electrodialysis reversal and the like. In order to prevent the adverse effect which may be generated on the final treatment effect of the method under the abnormal working condition, a control system is also provided with precautionary measures such as high (low) water level alarm (prompt) and pressure abnormity alarm, so as to ensure the accuracy of necessary control parameters in the actual operation process, and simultaneously, the control system can also guide the correctness of the operation behavior of an operator to a certain extent and avoid adverse factors brought by the misoperation behavior to the system operation.
Preparation before operation:
it is determined whether the power supply is 380V, 50 Hz.
(1) The fuses of MCB (circuit breaker for wiring) of an operation loop in the electric control cabinet are closed, and the fuses of the following CP loops are closed at the same time: universal socket, fluorescent lamp in electric control cabinet, scavenger fan power supply, timer loop (100V), PC power supply, control power supply
(2) And a switch for switching on the MCB and ELB (electrical leakage breaker) of each motor.
(3) Closing the switch of the MCB of the main line.
(4) And closing switches of the power supplies of the instruments in the cabinet.
Operation preparation:
the control switches on the power distribution cabinet except the cleaning water pump are all switched to the 'automatic' position, the operation condition is completed by the control of a computer program,
after the device stops operating, the air switches of all electromechanical devices and control circuits are disconnected, the air switch of the main circuit is disconnected, and all control switches on the panel of the power distribution control cabinet are shifted to a stop position.
As shown in figure 1, the zero-emission treatment device for high-salinity wastewater provided by the invention comprises an electrochemical unit 1, a reverse osmosis unit 2, an ozone catalytic oxidation unit 3 and a salt separation recovery unit 9 which are independently fixed on a steel structure frame to form a whole and are sequentially connected.
In a specific implementation, as shown in fig. 2, the salt separation and recovery unit 9 may include an electrodialysis unit 5, and an outlet of the electrodialysis unit 5 is connected to a bipolar membrane electrodialysis unit and a reverse osmosis unit 6, 2; and the device also comprises a PLC control unit 8 which is respectively connected with the electrochemical unit 1, the reverse osmosis unit 2, the ozone catalytic oxidation unit 3, the electrodialysis unit 5 and the bipolar membrane electrodialysis unit 6 and is fixed on the steel structure frame.
In a specific implementation, as shown in fig. 3, the partial salt recovery unit 9 may include an electrodialysis unit 5, and an outlet of the electrodialysis unit 5 is connected to the partial salt conversion unit 7 and the reverse osmosis unit 2; and the device also comprises a PLC control unit 8 which is respectively connected with the electrochemical unit 1, the reverse osmosis unit 2, the ozone catalytic oxidation unit 3, the electrodialysis unit 5 and the salt separation conversion unit 7 and is fixed on the steel structure frame.
In specific implementation, as shown in fig. 4, the salt separation recovery unit 9 may further include a nanofiltration unit 4, and an outlet of the nanofiltration unit 4 is connected to an electrodialysis unit 5 and a salt separation conversion unit 7; the outlet of the electrodialysis unit 5 is connected with a bipolar membrane electrodialysis unit 6 and a reverse osmosis unit 2; and the device also comprises a PLC control unit 8 which is respectively connected with the electrochemical unit 1, the reverse osmosis unit 2, the ozone catalytic oxidation unit 3, the nanofiltration unit 4, the electrodialysis unit 5, the bipolar membrane electrodialysis unit 6 and the salt separation conversion unit 7 and is fixed on the steel structure frame.
Wherein the electrochemical unit 1 can be selected from electrochemical reactors in the prior art, and the specific structure thereof is not described in detail herein; the reverse osmosis unit 2 comprises a first reverse osmosis subunit and a second reverse osmosis subunit, and the first reverse osmosis subunit and the second reverse osmosis subunit both comprise a plurality of reverse osmosis membranes in the prior art, and the specific structure thereof is not described herein again; the ozone catalytic oxidation unit 3 is selected from the prior art, and for example, may include an ozone generating device, a pipeline and a catalytic tower, the ozone generating device includes an oxygen generating device and an ozone generator, the oxygen generating device is connected with the ozone generator, the ozone generating device is connected with the catalytic tower through the pipeline, and the specific structure thereof is not described herein again; the nanofiltration unit 4 can be selected from a plurality of nanofiltration membranes in the prior art, and the specific structure thereof is not described herein; the electrodialysis unit 5 can be selected from electrodialysis devices in the prior art, and the specific structure of the electrodialysis unit is not described in detail herein; the bipolar membrane electrodialysis unit 6 can be selected from electrodialysis devices in the prior art, and the specific structure of the bipolar membrane electrodialysis unit is not described in detail herein; the salt separation conversion unit 7 can be selected from closed tanks in the prior art, and the specific structure thereof is not described in detail herein.
Example 1
The embodiment provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps:
1) deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method;
the high-salinity wastewater is coking high-salinity wastewater, and the main water inlet indexes are as follows: CODCr：55mg/L，Cl-:1100mg/L，SO4 2-：800mg/L，Ca2+：41mg/L，Mg2+:20mg/L，Na+2168 mg/L; the parameters of the electrochemical method are as follows: the current density is 20mA/cm2The retention time is 20 min;
2) performing reverse osmosis desalination on effluent after electrochemical hardness and organic pollutants removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts two-stage low-pressure reverse osmosis, and the operating pressure is 1.8 MPa;
3) carrying out catalytic ozonation on the reverse osmosis concentrated water;
said odorCatalyst volume for oxygen-catalyzed oxidation: the volume of water is 1:1 (volume ratio); the concentration of the ozone is 80mg/L, the retention time is 60min, and the COD is obtained by catalytic oxidation of the ozoneCr78% of degradable;
the preparation process of the catalyst is as follows:
taking 100g of catalyst as an example, the mass ratio of the carrier to the active component is 90:10, the mesoporous activated carbon is 90g, and the copper (4.5 wt%): 4.5g, manganese (3 wt%): 3g, cobalt (0.5 wt%): 0.5g, nickel (2 wt%): 2g, namely: copper acetate: 12.9g, manganese acetate: 9.4g, cobalt acetate: 1.5g, nickel acetate: 6g of a mixture; soaking 90g of mesoporous activated carbon in a mixed solution consisting of 12.9g of copper acetate solution (50 wt%), 9.4g of manganese acetate solution (50 wt%), 1.5g of cobalt acetate solution (50 wt%) and 6g of nickel acetate solution (50 wt%) for 24 hours; after soaking, air-drying for 24h at normal temperature to obtain a semi-finished catalyst; and under the protection of nitrogen, roasting the obtained catalyst semi-finished product in a resistance furnace at 1300 ℃ for 8h for forming, and naturally cooling to room temperature.
4) Carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
the operating pressure of nanofiltration is 0.9MPa, the freshwater of nanofiltration accounts for 80% (v/v) of the nanofiltration water inflow, and the concentrated water accounts for 20% (v/v) of the nanofiltration water inflow;
5) subjecting the nanofiltration fresh water to electrodialysis for further concentration; then carrying out reverse osmosis on the fresh water subjected to electrodialysis, and carrying out bipolar membrane electrodialysis on the concentrated water subjected to electrodialysis to prepare acid and alkali;
the current density of the electrodialysis is 60mA/cm2(ii) a The bipolar membrane electrodialysis has a current intensity of 3.6A, a voltage of 30V and a current density of 60mA/cm2The retention time is 50 min; the concentrated water pressure of the bipolar membrane electrodialysis is 0.02MPa, the fresh water pressure is 0.01MPa, and the fresh water pressure is equal to the polar water pressure and is 0.01 MPa;
6) and (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
The salt separation conversion is specifically as follows: and (3) introducing excessive ammonium carbonate (the molar ratio of the ammonium carbonate to the sodium sulfate is 5:1) into the nanofiltration concentrated aqueous sodium sulfate solution to perform double decomposition reaction to obtain sodium carbonate or sodium bicarbonate.
After electrochemical deep hardness removal and organic matter pre-removal, the reverse osmosis membrane is cleaned once in 10 months, generally cleaned once in 3-12 months, so that the performance and the service life of the membrane are improved, the recovery rate of fresh water is 93%, the concentration of acid and alkali prepared by bipolar membrane electrodialysis is 5 wt%, the high-salinity wastewater treated by the method can be used for resin regeneration, the purity of sodium carbonate is more than 98.7%, the high-salinity wastewater can be used by oneself or sold, the nitrogen content of ammonium sulfate is more than 22.6 wt%, and the high-salinity wastewater meets the qualified product requirement of the national standard GB535-1995 of ammonium sulfate.
The performance results of the treatments at each step of the process described in this example are shown in table 1 below.
TABLE 1
CODCr(mg/L) TDS(mg/L) Hardness (mg/L)
Raw water 55 4520 185
Electrochemistry method 45 4460 18
Reverse osmosis 180 22600 -
Catalytic oxidation with ozone 40 22409 -
Nanofiltration of fresh water - 11331 -
Electrodialysis concentrated water - 114280 -
Nanofiltration concentrated water - 30850 -
As can be seen from the data in Table 1, in the zero-emission treatment method described in this example, the electrochemical hardness removal rate is 90%, the effluent hardness is 18mg/L, and the organic pollutants (COD) are presentCr) The degradation rate is 18 percent, and the pollution of the subsequent reverse osmosis membrane is reduced; organic pollutant (COD) after catalytic oxidation by ozoneCr) The degradation rate of the bipolar membrane electrodialysis membrane is 78%, the TDS of the electrodialysis concentrated water is 114280mg/L, and the acid-base concentration of the subsequent bipolar membrane electrodialysis is ensured to be 5 wt%.
Example 2
The embodiment provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps:
1) deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method;
the high saltThe wastewater is coal gasification high-salinity wastewater, and the main water inlet indexes are as follows: CODCr：40mg/L，Cl-:1200mg/L，SO4 2-：960mg/L，Ca2+：50mg/L，Mg2+:43mg/L，Na+2052 mg/L; the parameters of the electrochemical method are as follows: the current density is 15mA/cm2The retention time is 30 min;
2) performing reverse osmosis desalination on effluent after electrochemical hardness and organic pollutants removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts two-stage low-pressure reverse osmosis, and the operating pressure is 1.8 MPa;
3) carrying out catalytic ozonation on the reverse osmosis concentrated water;
the catalyst for catalytic oxidation by ozone (the composition and the preparation steps are the same as those of the example 1) is as follows: the volume of water is 0.8:1 (volume ratio); the ozone concentration is 80mg/L, the retention time is 40min, and COD is obtained by catalytic oxidation of ozoneCr78% of degradable;
4) carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
the operating pressure of the nanofiltration membrane for separating salt is 0.5MPa, the nanofiltration fresh water accounts for 90% (v/v) of the nanofiltration water inflow, and the nanofiltration concentrated water accounts for 10% (v/v) of the nanofiltration water inflow;
5) subjecting the nanofiltration fresh water to electrodialysis for further concentration; then carrying out reverse osmosis on the fresh water subjected to electrodialysis, and carrying out bipolar membrane electrodialysis on the concentrated water subjected to electrodialysis to prepare acid and alkali;
the current density of the electrodialysis is 68mA/cm2(ii) a The bipolar membrane electrodialysis has a current intensity of 4A, a voltage of 33V and a current density of 50mA/cm2The retention time is 55 min; the concentrated water pressure of the bipolar membrane electrodialysis is 0.02MPa, the fresh water pressure is 0.01MPa, and the fresh water pressure is equal to the polar water pressure and is 0.01 MPa;
6) and (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
The salt separation conversion is specifically as follows: and (3) introducing excessive ammonium carbonate (the molar ratio of the ammonium carbonate to the sodium sulfate is 7:1) into the nanofiltration concentrated aqueous sodium sulfate solution to perform double decomposition reaction to obtain sodium carbonate or sodium bicarbonate.
The recovery rate of fresh water of the high-salinity wastewater treated by the method of the embodiment is 90%, the concentration of acid and alkali prepared by bipolar membrane electrodialysis is 6%, the high-salinity wastewater can be used for resin regeneration, the purity of sodium carbonate is more than 97.6%, the sodium carbonate can be used by oneself or sold, the ammonium sulfate nitrogen content is more than 23.2%, and the high-salinity wastewater meets the qualified product requirement of the ammonium sulfate national standard GB 535-1995.
The performance results of the treatments at each step of the process described in this example are shown in table 2 below.
TABLE 2
Figure BDA0002637667370000141
Figure BDA0002637667370000151
As can be seen from the data in Table 2, in the zero-emission treatment method described in this example, the electrochemical hardness removal rate is 90%, the effluent hardness is 30mg/L, and the organic pollutants (COD) are presentCr) The degradation rate is 10 percent, and the pollution of the subsequent reverse osmosis membrane is reduced; organic pollutant (COD) after catalytic oxidation of ozoneCr) The degradation rate of (2) is 78%, and the TDS of electrodialysis concentrated water is 109305mg/L, so that the acid-base concentration of the subsequent bipolar membrane electrodialysis is 6 wt%.
Example 3
The embodiment provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps:
1) deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method;
the high-salinity wastewater is coal gasification high-salinity wastewater, and the main water inlet indexes are as follows: CODCr：40mg/L，Cl-:830mg/L，SO4 2-：580mg/L，Ca2+：46mg/L，Mg2+:34mg/L，Na+2122 mg/L; the parameters of the electrochemical method are as follows: the current density was 30mA/cm2The retention time is 15 min;
2) performing reverse osmosis desalination on the effluent after electrochemical hardness and organic matter removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts two-stage low-pressure reverse osmosis, and the operating pressure is 1.5 MPa;
3) carrying out catalytic ozonation on the reverse osmosis concentrated water;
the catalyst for catalytic oxidation by ozone (the composition and the preparation steps are the same as those of the example 1) is as follows: the volume of water is 0.6:1 (volume ratio); the concentration of the ozone is 100mg/L, the retention time is 40min, and COD is obtained by catalytic oxidation of the ozoneCrCan be degraded by 79.8 percent;
4) carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
the operating pressure of the nanofiltration membrane for separating salt is 0.7MPa, the nanofiltration fresh water accounts for 80% (v/v) of the nanofiltration water inflow, and the nanofiltration concentrated water accounts for 20% (v/v) of the nanofiltration water inflow; case(s)
5) Subjecting the nanofiltration fresh water to electrodialysis for further concentration; then carrying out reverse osmosis on the fresh water subjected to electrodialysis, and carrying out bipolar membrane electrodialysis on the concentrated water subjected to electrodialysis to prepare acid and alkali;
the current density of the electrodialysis is 40mA/cm2(ii) a The bipolar membrane electrodialysis current intensity is 3A, the voltage is 25V, and the current density is 55mA/cm2The retention time is 60 min; the concentrated water pressure of the bipolar membrane electrodialysis is 0.02MPa, the fresh water pressure is 0.01MPa, and the fresh water pressure is equal to the polar water pressure and is 0.01 MPa;
6) and (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
The salt separation conversion is specifically as follows: and (3) introducing excessive ammonium carbonate into the nanofiltration concentrated aqueous sodium sulfate solution, wherein the molar ratio of the ammonium carbonate to the sodium sulfate is 5.5:1), and carrying out double decomposition reaction to obtain sodium carbonate or sodium bicarbonate.
The recovery rate of fresh water of the high-salinity wastewater treated by the method of the embodiment is 88 percent, the concentration of acid and alkali prepared by bipolar membrane electrodialysis is 4.4 percent, the high-salinity wastewater can be used for resin regeneration, the purity of sodium carbonate is more than 97.8 percent and can be used by oneself or sold, the content of ammonium sulfate nitrogen is more than 20.9 percent, and the high-salinity wastewater meets the qualified product requirement of the national standard GB535-1995 of ammonium sulfate.
The performance results of the treatments at each step of the process described in this example are shown in table 3 below.
TABLE 3
CODCr(mg/L) TDS(mg/L) Hardness (mg/L)
Raw water 40 3925 256
Electrochemistry method 36 3840 22
Reverse osmosis 144 15700 -
Catalytic oxidation with ozone 29 15500 -
Nanofiltration of fresh water - 9062 -
Electrodialysis concentrated water - 91390 -
Nanofiltration concentrated water - 22500 -
As can be seen from the data in Table 3, in the zero-emission treatment method described in this example, the electrochemical hardness removal rate is 91%, the effluent hardness is 22mg/L, and the organic pollutants (COD) are presentCr) The degradation rate is 10 percent, and the pollution of the subsequent reverse osmosis membrane is reduced; organic pollutant (COD) after catalytic oxidation of ozoneCr) The degradation rate of (2) was 80%, and the TDS of the electrodialysis concentrate was 91390mg/L, so that the acid-base concentration of the subsequent bipolar membrane electrodialysis was 4.4 wt%, which was lower than that in examples 1 and 2.
Example 4
The embodiment provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps:
1) deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method;
the high-salinity wastewater is fermentation biochemical effluent, the main index of water inlet is fermentation biochemical effluent in the west of the river, and the indexes are as follows: concentration of sodium sulfate: 1.5 wt%, CODCr: 40mg/L, hardness 260: mg/L;
the parameters of the electrochemical method are as follows: the current density was 30mA/cm2The retention time is 15 min;
2) performing reverse osmosis desalination on the effluent after electrochemical hardness and organic matter removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts first-stage high-pressure reverse osmosis, and the operating pressure of the high-pressure reverse osmosis is 3.0 MPa;
3) carrying out catalytic ozonation on the reverse osmosis concentrated water;
the catalyst for catalytic oxidation by ozone (the composition and the preparation steps are the same as those of the example 1) is as follows: the volume of water is 1:1 (volume ratio); the concentration of the ozone is 100mg/L, the retention time is 40min, and COD is obtained by catalytic oxidation of the ozoneCrThe degradable material can be degraded by 80 percent;
4) carrying out electrodialysis on the ozone catalytic oxidation effluent to further concentrate; then carrying out reverse osmosis on the electrodialyzed fresh water;
the current density of the electrodialysis is 40mA/cm2；
5) And (4) carrying out salt separation conversion on the electrodialysis concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
The salt separation conversion is specifically as follows: and (3) introducing excessive ammonium carbonate into the nanofiltration concentrated aqueous sodium sulfate solution, wherein the molar ratio of the ammonium carbonate to the sodium sulfate is 5.5:1), and carrying out double decomposition reaction to obtain sodium carbonate or sodium bicarbonate.
The high-salinity wastewater treated by the method of the embodiment has the fresh water recovery rate of 90 percent, the purity of sodium carbonate of 98.3 percent, can be used by oneself or sold, and the ammonium sulfate nitrogen content of more than 20.9 percent, and meets the qualified product requirement of the ammonium sulfate national standard GB 535-1995.
The performance results of the treatments at each step of the process described in this example are shown in table 4 below.
TABLE 4
CODCr(mg/L) Sodium sulfate (1.5%) Hardness (mg/L)
Raw water 40 1.5％ 260
Electrochemistry method 33 1.5％ 25
Reverse osmosis 144 3％ -
Catalytic oxidation with ozone 28 3％ -
Electrodialysis concentrated water - 15％ -
As can be seen from the data in Table 4, in the zero-emission treatment method described in this example, the electrochemical hardness removal rate is 90%, the effluent hardness is 25mg/L, and the organic pollutants (COD) are presentCr) The degradation rate is 18 percent, and the pollution of the subsequent reverse osmosis membrane is reduced; organic pollutant (COD) after catalytic oxidation by ozoneCr) The degradation rate of (2) was 81%, and the salt concentration of the electrodialysis concentrate was 15%, which was 5 times more concentrated than before.
The sodium salt in the high-salt wastewater of the embodiment is only sodium sulfate, so that a nanofiltration unit is not provided, and bipolar membrane electrodialysis is not further provided.
Example 5
The embodiment provides a zero-emission treatment method of high-salinity wastewater, which comprises the following steps:
1) deeply removing hardness and organic pollutants from the high-salinity wastewater by an electrochemical method;
the high-salinity wastewater is biochemical effluent of amino acid fermentation, and the main water inlet indexes are as follows: CODCr: 45mg/L, sodium chloride concentration: 2.3 wt%, hardness: 185mg/L, the parameters of the electrochemical method are as follows: the current density is 20mA/cm2The retention time is 15 min;
2) performing reverse osmosis desalination on the effluent after electrochemical hardness and organic matter removal, and recycling fresh water after reverse osmosis desalination;
the reverse osmosis desalination adopts first-stage high-pressure reverse osmosis, and the operating pressure of the high-pressure reverse osmosis is 3.0 MPa;
3) carrying out catalytic ozonation on the reverse osmosis concentrated water;
the catalyst for catalytic oxidation by ozone (the composition and the preparation steps are the same as those of the example 1) is as follows: the volume of water is 0.8:1 (volume ratio); the concentration of the ozone is 100mg/L, the retention time is 50min, and the COD is obtained by catalytic oxidation of the ozoneCr78% of degradable;
4) subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration; then carrying out reverse osmosis on the fresh water subjected to electrodialysis, and carrying out bipolar membrane electrodialysis on the concentrated water subjected to electrodialysis to prepare acid and alkali;
the current density of the electrodialysis is 40mA/cm2(ii) a The bipolar membrane electrodialysis has a current intensity of 3A, a voltage of 25V and a current density of 55mA/cm2The retention time is 60 min; the concentrated water pressure of the bipolar membrane electrodialysis is 0.02MPa, the fresh water pressure is 0.01MPa, and the fresh water pressure is equal to the polar water pressure and is 0.01 MPa;
the recovery rate of fresh water of the high-salinity wastewater treated by the method in the embodiment is 89%, and the concentration of acid and alkali prepared by bipolar membrane electrodialysis is 7.8%, so that the high-salinity wastewater can be used for resin regeneration.
The performance results of the treatments at each step of the process described in this example are shown in table 5 below.
TABLE 5
Figure BDA0002637667370000181
Figure BDA0002637667370000191
As can be seen from the data in Table 5, in the zero-emission treatment method described in this example, the electrochemical hardness removal rate is 88%, the effluent hardness is 22mg/L, and the organic pollutants (COD) are presentCr) The degradation rate is 29 percent, and the pollution of the subsequent reverse osmosis membrane is reduced; organic pollutant (COD) after catalytic oxidation by ozoneCr) The degradation rate of (2) was 81%, and the salt concentration of the electrodialysis concentrate was 17.8%, which was 4 times concentrated from before.
Example 4 and example 5 are single salts, so no nanofiltration was performed. Therefore, the treatment method belongs to a platform type technology and can be adjusted according to different salt types.
In the description of the present invention, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.

Claims (13)

1. A zero-emission treatment method of high-salinity wastewater is characterized by comprising the following steps:
a, deeply removing hardness and organic pollutants from high-salinity wastewater by an electrochemical method;
b, performing reverse osmosis desalination on the effluent after electrochemical hardness and organic pollutant removal, and recycling fresh water after reverse osmosis desalination;
c, carrying out catalytic ozonation on the reverse osmosis concentrated water;
d, performing salt separation and recovery on the effluent after the catalytic oxidation of the ozone.
2. The method of claim 1, wherein in the step a, the high-salinity wastewater is wastewater containing salt with a mass fraction of more than 1%, the wastewater contains sodium salt, calcium salt and magnesium salt, the sodium salt is at least one of sodium sulfate and sodium chloride, and the content of the sodium salt accounts for more than 90% of the total mass of the sodium salt, the calcium salt and the magnesium salt; the parameters of the electrochemical method are set as follows, and the current density is 5-30mA/cm2The retention time is 5-30 min; in the step b, the reverse osmosis desalination adopts one-stage high-pressure reverse osmosis or two-stage low-pressure reverse osmosis, the operating pressure of the high-pressure reverse osmosis is 2.8-4.2MPa, and the operating pressure of the low-pressure reverse osmosis is 1.4-2.0 MPa.
3. The method of claim 1, wherein in step c, the parameters for the catalytic ozonation are set as follows: the selected ozone catalyst is a supported mesoporous activated carbon catalyst; the concentration of ozone and CODCrThe concentration ratio is (1.2-1.5) to 1 (mg/L); the water inlet parameters of the ozone catalytic oxidation are as follows, wherein Cl is more than 0-:CODCrLess than 15:1(mg/L), the pH value is 6-9, and the retention time is 30-90 min; the ratio of the ozone catalyst to water is 0.5:1-1:1 (v/v).
4. The method of claim 3, wherein in step c, the supported mesoporous activated carbon catalyst comprises a support and an active component; the carrier is mesoporous spherical activated carbon with the diameter of 3-5mm, and the active component is transition metal oxide; the transition metal oxide is selected from at least one of manganese dioxide, copper oxide, nickel oxide and cobalt oxide; the mass ratio of the carrier to the active component is (90-93): (7-10).
5. The method according to claim 2, wherein when the salt is sodium chloride, the fractional salt recovery in step d specifically comprises:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali.
6. The method according to claim 2, wherein when the salt is sodium sulfate, the fractional salt recovery in step d specifically comprises:
subjecting the ozone-catalyzed oxidation effluent to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
and (4) carrying out salt separation conversion on the electrodialysis concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
7. The method according to claim 2, wherein when the salt comprises sodium sulfate and sodium chloride, the fractional salt recovery in step d specifically comprises:
carrying out nanofiltration on the effluent after the catalytic oxidation of ozone;
subjecting the nanofiltration fresh water to electrodialysis for further concentration;
carrying out reverse osmosis on the electrodialyzed fresh water;
performing bipolar membrane electrodialysis on the electrodialysis concentrated water to prepare acid and alkali;
and (4) carrying out salt separation conversion on the nanofiltration concentrated water so as to convert sodium sulfate into sodium carbonate or sodium bicarbonate.
8. The process according to any of claims 5 to 7, wherein the electrodialysis has a current density of 20 to 70mA/cm2(ii) a The bipolar membrane electrodialysis has current intensity of 2-4A, voltage of 15-40V, and current density of 20-100mA/cm2The retention time is 30-90 min; the pressure of concentrated water, polar water and fresh water of the bipolar membrane electrodialysis is 0.01-0.02 MPa; the total amount of the water inflow soluble solid of the bipolar membrane electrodialysis is 80000-120000 mg/L.
9. The method of claim 7, wherein the operating pressure of nanofiltration is 0.5 to 1.0 MPa; the salt separation conversion specifically comprises: introducing excessive ammonium carbonate into the sodium sulfate solution to perform double decomposition reaction to generate ammonium sulfate, sodium carbonate or sodium bicarbonate; the molar ratio of the ammonium carbonate to the sodium sulfate is more than or equal to 5: 1.
10. The zero-emission treatment device for the high-salinity wastewater is characterized by comprising an electrochemical unit, a reverse osmosis unit, an ozone catalytic oxidation unit and a salt separation recovery unit which are independently fixed on a steel structure frame to form a whole and are sequentially connected.
11. The zero-emission treatment device of claim 10, wherein the salt separation recovery unit comprises an electrodialysis unit, and an outlet of the electrodialysis unit is connected with a bipolar membrane electrodialysis unit and a reverse osmosis unit.
12. The zero-emission treatment apparatus of claim 10, wherein the partial salt recovery unit comprises an electrodialysis unit, and an outlet of the electrodialysis unit is connected with a partial salt conversion unit and a reverse osmosis unit.
13. The zero-emission treatment apparatus of claim 10, wherein the salt separation recovery unit comprises a nanofiltration unit, and an outlet of the nanofiltration unit is connected with an electrodialysis unit and a salt separation conversion unit; the outlet of the electrodialysis unit is connected with a bipolar membrane electrodialysis unit and a reverse osmosis unit.
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