CN113501608A - Wastewater zero-discharge treatment system and process - Google Patents

Wastewater zero-discharge treatment system and process Download PDF

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Publication number
CN113501608A
CN113501608A CN202110756811.4A CN202110756811A CN113501608A CN 113501608 A CN113501608 A CN 113501608A CN 202110756811 A CN202110756811 A CN 202110756811A CN 113501608 A CN113501608 A CN 113501608A
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China
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wastewater
treatment
reverse osmosis
unit
osmosis membrane
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Inventor
田中宏
赵冬
张祥海
谷磊
徐宝田
洪峰
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Inner Mongolia Jinhe Environmental Protection Technology Co ltd
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Inner Mongolia Jinhe Environmental Protection Technology 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
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
    • 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
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • 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
    • C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/02—Odour removal or prevention of malodour
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents

Abstract

The invention relates to a wastewater zero-discharge treatment system and a process, which comprises a pretreatment unit, a membrane concentration unit, an evaporation crystallization unit, a solid salt treatment unit and a product water pool, wherein the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are used for sequentially treating raw wastewater; wherein the raw material wastewater is wastewater subjected to aerobic treatment; the pretreatment unit comprises a collecting water tank and ultrafiltration equipment, the membrane concentration unit comprises a first reverse osmosis membrane device, a high-density softened water tank, a multi-medium filter, nanofiltration equipment and a second reverse osmosis membrane device which are sequentially connected, and the evaporative crystallization unit comprises multi-effect evaporative crystallization equipment; the invention combines the sub-osmosis membrane with medium-high pressure reverse osmosis for the first time to be applied to the treatment of multi-source mixed complex wastewater in industrial parks, thereby realizing zero discharge of wastewater, waste gas and waste residues.

Description

Wastewater zero-discharge treatment system and process
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a wastewater zero-discharge treatment system and process.
Background
A large amount of wastewater is generated in the chemical and biological pharmaceutical processes, including production wastewater of 6-aminopenicillanic acid, aureomycin, abamectin, coenzyme Q10, amoxicillin, ampicillin, piperacillin, sulbactam and the like, and the wastewater is usually concentrated in a sewage treatment plant in a park for pretreatment and biochemical treatment to meet the industrial discharge requirement. Because the components of the waste water are complex, the waste water contains sulfate radicals, various organic matters, alcohols, hydrogen sulfide and raw materials which are not utilized in fermentation, in the process of treating the waste water, unorganized discharged waste gas containing bad smell, bad smell and peculiar smell can be generated, certain influence is caused on the health of human bodies and animals, the waste water treatment does not reach the standard, soil and water bodies can be polluted after the waste water is discharged, and in addition, the influence can be caused to the peripheral environment of a factory due to improper treatment of solid waste such as sludge generated by concentration in the waste water treatment process.
The current treatment mode of zero discharge of wastewater mainly combines the wastewater after biochemical treatment with membrane concentration and multiple-effect evaporation technology, thereby realizing the grading treatment and the maximum reuse of the wastewater. However, in the existing reverse osmosis membrane process, the requirement of a reverse osmosis membrane working section on water inlet is too high, hardness (calcium and magnesium ions) removal needs to be carried out before the reverse osmosis membrane working section enters a medium-high pressure reverse osmosis membrane working section, the formula of a medicament used for hardness removal is complex, the operation cost is high, a two-level high-density softening water tank needs to be established, and the investment is large. Therefore, a simple and convenient treatment process with low investment, good effect and zero wastewater discharge is found to realize the regeneration and reuse of the sewage, save water resources and protect the water environment.
Disclosure of Invention
The invention aims to provide a wastewater zero-discharge treatment system and a wastewater zero-discharge treatment process aiming at the defects and shortcomings of the prior art so as to realize zero discharge of wastewater treatment.
In order to achieve the aim, the invention provides a wastewater zero-discharge treatment system, which comprises a pretreatment unit, a membrane concentration unit, an evaporation crystallization unit, a solid salt treatment unit and a product water pool, wherein the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are used for sequentially treating raw wastewater; wherein the content of the first and second substances,
the raw material wastewater is wastewater subjected to aerobic treatment;
the pretreatment unit comprises a collecting water tank and ultrafiltration equipment, the membrane concentration unit comprises a first reverse osmosis membrane device, a high-density softened water tank, a multi-medium filter, nanofiltration equipment and a second reverse osmosis membrane device which are sequentially connected, and the evaporative crystallization unit comprises multi-effect evaporative crystallization equipment;
the first reverse osmosis membrane equipment is sub-osmosis membrane equipment, and the operation conditions are as follows: the working pressure is 1.2-2.3 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 65-80%.
The invention also provides a wastewater zero-discharge treatment process, which comprises the following steps:
s1: raw material wastewater enters a pretreatment unit and is pretreated by a collecting tank and ultrafiltration equipment;
s2, introducing the wastewater treated in the step S1 into a membrane concentration unit for wastewater concentration and reverse osmosis treatment to form concentrated water and produced water, wherein the formed produced water enters a product water pool;
s3, carrying out evaporative crystallization treatment on the concentrated water formed after the treatment in the step S2 in an evaporative crystallization unit to form solid salt and produced water, wherein the formed produced water enters a product water pool;
and S4, carrying out salt separation treatment on the solid salt formed after the treatment of the step S3 in a solid salt treatment unit.
Compared with the prior art, the invention has the following beneficial effects:
1) the invention combines the sub-osmosis membrane and the medium-high pressure reverse osmosis to be applied to the treatment of multi-source, mixed and complex wastewater in an industrial park for the first time, but not the treatment of single-source wastewater, thereby realizing the zero discharge of industrial wastewater. The invention also breaks through the limitation that the membrane concentration unit in the prior art needs to remove hardness of wastewater before concentration, and simplifies the process flow.
2) According to the invention, the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are operated in a totally-enclosed manner when treating wastewater, so that the odor is eliminated on site, no odor is discharged in the whole process, and zero emission of waste gas in the whole process of wastewater treatment can be realized.
3) According to the invention, the concentrated water after membrane concentration enters the high-density softening tank for hardness removal treatment, so that the reduction and hardness removal of wastewater are realized, the quantity of hardness removal agents is greatly reduced, the formula of the hardness removal agents can be simplified, the PAC, the sodium hydroxide, the sodium carbonate and the PAM in the prior art are not needed, the sodium hydroxide, the sodium carbonate and the PAM are changed, the cost (large dosage and high cost) can be reduced, the water quality treatment effect is not reduced, and the calcium and magnesium ion treatment of water can reach the standard.
4) According to the invention, the hardness removal effect of the two-stage high-density softening water tank required by the traditional wastewater medium-high pressure reverse osmosis treatment process can be achieved only by arranging the single-stage high-density softening water tank before nanofiltration, and the construction cost and the operation cost are both reduced because the second-stage high-density softening water tank is arranged after nanofiltration is eliminated.
5) According to the invention, the nanofiltration membrane is concentrated and then subjected to MVR evaporation crystallization, so that the efficiency can be improved by 50%, namely 50% of nanofiltration concentrated water is concentrated by 50%.
6) The sludge formed after the wastewater treatment is subjected to precipitation concentration and then is subjected to dehydration treatment, the sludge dehydration equipment adopts a high-pressure plate-and-frame filter press, the pressing pressure is more than or equal to 3.0MPa, the water content of the sludge is reduced to below 50 percent, the main components of the sludge are inorganic salts such as calcium carbonate, magnesium carbonate and the like, the sludge is common industrial solid waste, and the sludge is treated in a landfill mode or used as an auxiliary material of a building material. The solid salt formed in the evaporation section can be separated to prepare inorganic salt (sodium chloride and sodium sulfate), and the reduction and discharge of waste residues are realized.
7) Different from the traditional wastewater treatment method in which sodium hypochlorite is added for sterilization and microorganism removal, the method provided by the invention has the advantages that the raw material wastewater is pretreated by adding the sodium hypochlorite before entering the sub-osmosis membrane equipment for treatment, so that the purpose is to remove Fe in the wastewater2+Oxidation to form Fe3+So as to achieve the synergistic and flocculation effect and protect the subsequent sub-permeable membrane equipment. Preferably before ultrafiltration (interception of a part of the Fe)3 +To reduce the processing load of the sub-osmotic membrane device).
8) Aiming at the problem that the effect is influenced by insufficient reaction time after sodium hypochlorite is added, the retention time is prolonged by adopting methods of lengthening a feeding pipeline, increasing a pipeline mixer or increasing the volume of an ultrafiltration water production tank and the like, and the effect of the sodium hypochlorite is best played.
Drawings
FIG. 1 is a schematic diagram of a wastewater treatment zero-discharge system according to embodiment 1;
FIG. 2 is a schematic diagram of a wastewater treatment zero-emission process according to embodiment 1;
FIG. 3 is a schematic diagram of a wastewater treatment zero-discharge system according to embodiment 2;
FIG. 4 is a schematic flow diagram of a wastewater treatment zero-emission process according to embodiment 2;
FIG. 5 is a schematic view of a wastewater treatment zero-discharge process flow according to comparative embodiment 1.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
The embodiment of the invention provides a wastewater zero-discharge treatment system, which comprises a pretreatment unit, a membrane concentration unit, an evaporation crystallization unit, a solid salt treatment unit and a product water pool, wherein the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are used for sequentially treating raw wastewater; wherein the content of the first and second substances,
the raw material wastewater is wastewater subjected to aerobic treatment;
the pretreatment unit comprises a collecting water tank and ultrafiltration equipment, the membrane concentration unit comprises a first reverse osmosis membrane device, a high-density softened water tank, a multi-medium filter, nanofiltration equipment and a second reverse osmosis membrane device which are sequentially connected, and the evaporative crystallization unit comprises multi-effect evaporative crystallization equipment;
the first reverse osmosis membrane equipment is sub-osmosis membrane equipment, and the operation conditions are as follows: the working pressure is 1.2-2.3 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 65-80%.
Further, the second reverse osmosis membrane equipment comprises a medium-pressure reverse osmosis membrane equipment and a high-pressure reverse osmosis membrane equipment which are sequentially connected, the produced water produced by the medium-pressure reverse osmosis membrane equipment and the high-pressure reverse osmosis membrane equipment is injected into the product water pool, and the concentrated water produced by the high-pressure reverse osmosis membrane equipment enters the evaporation crystallization unit.
Further, an intermediate water tank is arranged between at least two of the ultrafiltration equipment, the first reverse osmosis membrane equipment, the high-density softened water tank, the multi-medium filter, the nanofiltration equipment, the second reverse osmosis membrane equipment and the multi-effect evaporation crystallization equipment, and the intermediate water tank is at least used for containing the output produced water after being treated by the ultrafiltration equipment, the first reverse osmosis membrane equipment, the high-density softened water tank, the multi-medium filter, the nanofiltration equipment or the second reverse osmosis membrane equipment.
Further, the operating conditions of the medium-pressure reverse osmosis membrane equipment are as follows: the working pressure is 3-3.6 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 60-70%.
Further, the operating conditions of the high-pressure reverse osmosis membrane equipment are as follows: the working pressure is 5-6.5 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 50-60%.
Further, the operating conditions of the ultrafiltration device are as follows: the quality of inlet water is less than 5NTU, the screening aperture is 0.005-0.1um, the working pressure is 0.1-0.4MPa, the operating temperature is 15-35 ℃, and the water recovery rate is 90%.
Further, the operation mode of the ultrafiltration equipment is full-flow filtration and cross-flow filtration.
Further, the concentrated water generated by the sub-permeable membrane device enters the high-density softened water tank.
Further, the wastewater zero-discharge treatment system also comprises a sludge treatment unit for collecting sludge generated by the high-density softened water tank of the membrane concentration unit.
Further, the operating conditions of the nanofiltration equipment are as follows: the working pressure is 2-2.3 MPa; the operation temperature is 5-35 ℃; the water recovery rate is 70-75%.
Furthermore, the multi-effect evaporation crystallization equipment receives concentrated water generated by the high-pressure reverse osmosis membrane equipment and concentrated water generated by the nanofiltration equipment, the produced water generated after evaporation crystallization enters the product water pool, and formed solid salt enters the solid salt treatment unit.
Further, the operating conditions of the multi-effect evaporation crystallization equipment are as follows: PH 5.5-6.5, TDS less than or equal to 10% (mass ratio), COD less than 1500mg/l, SS less than 50mg/l, and hardness less than or equal to 300mg/l (by calcium carbonate).
Further, the water quality indexes of the raw material wastewater are as follows: pH of 6.5-8.5, COD of 60-150 mg/L, Cl-1500-3000 mg/L of SO4 2-100-3500 mg/L of Na+500-2000 mg/L, F-1-10 mg/L of total nitrogen, 10-100 mg/L of total nitrogen, 100-1000 mg/L of calcium, 10-1000 mg/L of magnesium, 3000-9000 mg/L of TDS and 10-50 mg/L of suspended matters.
Further, the sludge treatment unit comprises a sludge tank and sludge dewatering equipment.
Further, the sludge dewatering equipment is used for concentrating the sludge to prepare auxiliary materials used as building materials.
Furthermore, the main equipment for sludge dewatering adopts a high-pressure plate-and-frame filter press.
Furthermore, the squeezing pressure of the high-pressure plate-and-frame filter press is more than or equal to 3.0 MPa.
Furthermore, the raw material wastewater is multi-source mixed wastewater with complex components in an industrial park.
Furthermore, the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are operated in a fully closed mode when treating wastewater.
Further, the solid salt treatment unit can be used for preparing sodium chloride and sodium sulfate in a separating way.
Further, the solid salt treatment unit is a solid salt landfill.
Further, adding a strong oxidant into the pretreatment unit to remove Fe in the raw material wastewater2+Oxidation to form Fe3+The dosage of the strong oxidant is as follows: 1 to 4 ppm.
Further, the strong oxidant is sodium hypochlorite or hydrogen peroxide.
Further, the sodium hypochlorite is added in front of the ultrafiltration equipment, and preferably, the sodium hypochlorite is added on a wastewater pipeline connected with the raw wastewater entering the collecting water tank.
Further, the sodium hypochlorite is added into a waste water pipeline connected with the water collecting pool through a metering pump by flowing through a feeding pipe.
Further, the concentration of the residual chloride ions in the ultrafiltration water production tank is as follows: 0.1-0.5 ppm.
Further, the wastewater pipeline is 70-100 meters long, and the preferred pipeline is DN 200.
Furthermore, the capacity of an ultrafiltration water generating pool connected behind the ultrafiltration device is at least 20 cubic meters.
Further, wastewater hardness removal treatment is carried out after the first reverse osmosis membrane equipment and before the second reverse osmosis membrane equipment.
Further, wastewater hardness removal treatment is performed after the sub-osmosis membrane device.
Further, the wastewater hardness removal treatment is to add a hardness removal medicament of sodium hydroxide, sodium carbonate and PAM into the high-density softened water tank to remove hardness of wastewater.
Further, the formula of the hardness-removing medicament comprises the contents of sodium hydroxide, sodium carbonate and PAM, and the contents are calculated according to the hardness of calcium and magnesium ions in the sub-osmotic concentrated water.
Further, after the wastewater is concentrated by the nanofiltration membrane equipment, all concentrated wastewater enters the evaporative crystallization unit to be subjected to evaporative crystallization treatment, wherein the control conditions of the evaporative crystallization treatment are that the PH is 5.5-6.5, the TDS is less than or equal to 10% (mass percent), the COD is less than 1500mg/l, the SS is less than 50mg/l, and the hardness (by calcium carbonate) is less than or equal to 300 mg/l.
Further, the product water pool has the following water quality indexes: and the requirement of water replenishing quality of open circulating cooling water in GB/T19923-2005 is met, and TDS is less than or equal to 350 mg/l.
The embodiment of the invention also provides a wastewater zero-discharge treatment process, which comprises the following steps:
s1: raw material wastewater enters a pretreatment unit and is pretreated by a collecting tank and ultrafiltration equipment;
s2, introducing the wastewater treated in the step S1 into a membrane concentration unit for wastewater concentration and reverse osmosis treatment to form concentrated water and produced water, wherein the formed produced water enters a product water pool;
s3, carrying out evaporative crystallization treatment on the concentrated water formed after the treatment in the step S2 in an evaporative crystallization unit to form solid salt and produced water, wherein the formed produced water enters a product water pool;
and S4, carrying out salt separation treatment on the solid salt formed after the treatment of the step S3 in a solid salt treatment unit.
Further, in step S1, the raw wastewater is wastewater after aerobic treatment; the water quality indexes of the raw material wastewater are as follows: pH of 6.5-8.5, COD of 60-150 mg/L, Cl-1500-3000 mg/L of SO4 2-100-3500 mg/L of Na+500-2000 mg/L, F-1-10 mg/L of total nitrogen, 10-100 mg/L of total nitrogen, 100-1000 mg/L of calcium, 10-1000 mg/L of magnesium, 3000-9000 mg/L of TDS and 10-50 mg/L of suspended matters.
Further, in the step S1, adding a strong oxidant to the pretreatment unit to remove Fe from the raw material wastewater2+Oxidation to form Fe3+The dosage of the strong oxidant is as follows: 1-4 ppm.
Further, in step S1, sodium hypochlorite is added before the ultrafiltration apparatus, and the sodium hypochlorite is added to a wastewater pipeline connected to the water collection tank by a metering pump through a feeding pipe.
Further, in step S2, the membrane concentration unit includes first reverse osmosis membrane equipment, high-density softened water tank, multi-media filter, nanofiltration equipment and second reverse osmosis membrane equipment that connect gradually, wherein, first reverse osmosis membrane equipment is sub-osmosis membrane equipment, second reverse osmosis membrane equipment is middling pressure reverse osmosis membrane equipment and high pressure reverse osmosis membrane equipment that connect gradually, the product water that sub-osmosis membrane equipment, middling pressure reverse osmosis membrane equipment and high pressure reverse osmosis membrane equipment produced pours into the product water tank.
Further, in step S2, wastewater hardness removal treatment is performed after the first reverse osmosis membrane device and before the second reverse osmosis membrane device.
Further, in the step S2, the wastewater hardness removal treatment is to add a hardness removal agent of sodium hydroxide, sodium carbonate and PAM into the high-density softened water tank to perform wastewater hardness removal.
Further, step S2 includes a sludge treatment unit for collecting sludge generated by the high-density softened water tank of the membrane concentration unit, and treating the sludge to form general industrial solid waste (dried sludge) with a water content of less than or equal to 50% and solid salt, wherein the solid salt enters the solid salt treatment unit for salt separation treatment.
Further, the operating conditions of the sub-osmosis membrane device are as follows: the working pressure is 1.2-2.3 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 65-80%.
Further, the operating conditions of the medium-pressure reverse osmosis membrane equipment are as follows: the working pressure is 3-3.6 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 60-70%.
Further, the operation condition of the high-pressure reverse osmosis membrane equipment is that the working pressure is 5-6.5 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 50-60%.
Further, the operating conditions of the nanofiltration equipment are as follows: the working pressure is 2-2.3 MPa; the operation temperature is 5-35 ℃; the water recovery rate is 70-75%.
Further, the operating conditions of the multi-effect evaporation crystallization equipment are as follows: PH 5.5-6.5, TDS less than or equal to 10% (mass ratio), COD less than 1500mg/l, SS less than 50mg/l, and hardness less than or equal to 300mg/l (by calcium carbonate).
Further, the operating conditions of the ultrafiltration device are as follows: the quality of inlet water is less than 5NTU, the screening aperture is 0.005-0.1um, the working pressure is 0.1-0.4MPa, the operating temperature is 15-35 ℃, and the water recovery rate is 90%.
Further, the operation mode of the ultrafiltration equipment is full-flow filtration and cross-flow filtration.
The present invention is described in detail below with reference to the drawings and the specific embodiments, which are not repeated herein, but the embodiments of the present invention are not limited to the following embodiments.
Embodiment mode 1
Fig. 1 is a schematic view of a wastewater treatment zero discharge system according to embodiment 1 of the present invention; fig. 2 is a schematic diagram of a wastewater treatment zero-emission process flow according to embodiment 1.
As shown in fig. 1, the wastewater treatment zero-discharge system comprises a pretreatment unit, a membrane concentration unit, an evaporation crystallization unit, a solid salt treatment unit and a product water tank for collecting water produced by the membrane concentration unit and the evaporation crystallization unit, wherein the pretreatment unit, the membrane concentration unit, the evaporation crystallization unit and the solid salt treatment unit are used for sequentially treating raw wastewater; the pretreatment unit comprises a collecting water tank and ultrafiltration equipment, the membrane concentration unit comprises first reverse osmosis membrane equipment (sub-osmosis membrane equipment), a high-density softened water tank, a multi-medium filter, nanofiltration equipment and second reverse osmosis membrane equipment (medium-pressure reverse osmosis membrane equipment and high-pressure reverse osmosis membrane equipment) which are sequentially connected, and the evaporative crystallization unit comprises multi-effect evaporative crystallization equipment; the processing units are connected through pipelines; an intermediate water tank is arranged between the ultrafiltration equipment, the first reverse osmosis membrane equipment, the high-density softened water tank, the multi-medium filter, the nanofiltration equipment, the second reverse osmosis membrane equipment and the multi-effect evaporation crystallization equipment, and is used for containing the produced water which is output after being treated by the equipment, so that the buffer effect is achieved.
In the embodiment, the raw wastewater is wastewater after aerobic treatment, and the water quality indexes are as follows: pH of 6.5-8.5, COD of 60-150 mg/L, Cl-1500-3000 mg/L of SO4 2-100-3500 mg/L of Na+500-2000 mg/L, F-1-10 mg/L of total nitrogen, 10-100 mg/L of total nitrogen, 100-1000 mg/L of calcium, 10-1000 mg/L of magnesium, 3000-9000 mg/L of TDS and 10-50 mg/L of suspended matters.
The first reverse osmosis membrane equipment is sub-osmosis membrane equipment, and the operation conditions are as follows: the working pressure is 1.2-2.3 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 65-80%.
The operating conditions of the ultrafiltration apparatus were: the quality of inlet water is less than 5NTU, the screening aperture is 0.005-0.1um, the working pressure is 0.1-0.4MPa, the operating temperature is 15-35 ℃, and the water recovery rate is 90%. The operation mode of the ultrafiltration equipment is full flow filtration and cross flow filtration. The full-flow filtration has low energy consumption and low operation pressure, thereby having low operation cost. Crossflow filtration can treat more suspended matter content.
The second reverse osmosis membrane equipment comprises medium-pressure reverse osmosis membrane equipment and high-pressure reverse osmosis membrane equipment which are sequentially connected, produced water produced by the medium-pressure reverse osmosis membrane equipment and the high-pressure reverse osmosis membrane equipment is injected into a product water pool, and concentrated water produced by the high-pressure reverse osmosis membrane equipment enters the evaporative crystallization unit.
As shown in fig. 2, the wastewater after aerobic treatment enters the collection pool of the pretreatment unit through the water inlet pipe, and in embodiment 1, before entering the ultrafiltration device, sodium hypochlorite is added to the wastewater pipe connected with the collection pool through the metering pump via the feed pipe according to 1-4ppm of the wastewater proportion so as to facilitate Fe in the raw material wastewater2+Oxidation to form Fe3+So as to achieve the effects of synergy and flocculation, and the wastewater after oxidation treatment flows into the ultrafiltration equipment again for filtration and impurity removal, and can intercept part of Fe3+To reduce the processing load of subsequent sub-permeable membrane devices. In the embodiment, the water inlet amount of the raw material wastewater is 200-3At the time of/h, the sub-osmosis membrane equipment can stably operate and produce reclaimed water with qualified quality. In order to ensure the effect of wastewater pretreatment, the wastewater pipeline for feeding sodium hypochlorite is lengthened, the pipeline length is 70-100 m, and the pipeline is a DN200PVC pipe.
In this embodiment 1, because adopt the sub-osmosis membrane equipment at the first reverse osmosis membrane equipment of membrane concentration unit, the sub-osmosis membrane is higher to the hardness that the system was intake, and waste water need not carry out waste water and removes hard processing before getting into the sub-osmosis membrane equipment, and non-traditional middling pressure or high pressure reverse osmosis membrane equipment need can guarantee middling pressure or high pressure reverse osmosis membrane system's steady operation after preceding removes hard, and the hard effect of sub-osmosis membrane equipment is better, also can reduce membrane treatment cost. Therefore, the limitation that the hardness of the wastewater needs to be removed before concentration in the membrane concentration unit in the prior art is broken through, and the process flow is simplified.
In addition, compared with the traditional medium-pressure or high-pressure reverse osmosis system, the water inlet control index hardness and COD of the sub-osmosis membrane equipment are much higher than those of the conventional reverse osmosis membrane equipment, water with the same water quality is treated, and the water inlet operation pressure (the normal operation working pressure, the medium pressure is 3-3.6MPa, and the high pressure is 5-6.5MPa) and the concentrated water pressure of the sub-osmosis membrane equipment are lower than those of the traditional medium-pressure or high-pressure reverse osmosis membrane equipment, so that the operation cost can be reduced.
In embodiment 1, the wastewater is treated by the sub-permeable membrane equipment to form concentrated water (20-30% of the raw material inlet ratio), and the water quality index of the concentrated water is 3500 + 4500mg/L hardness, TDS: 25000mg/L-35000 mg/L. The concentrated water after membrane concentration enters a high-density softening tank for hardness removal treatment, so that the reduction and hardness removal of wastewater are realized, the quantity of hardness removal agents is greatly reduced, the formula of the hardness removal agents can be simplified, the addition of PAC, sodium hydroxide, sodium carbonate and PAM in the prior art is not needed, the sodium hydroxide, sodium carbonate and PAM are changed into the method, the cost can be reduced (the agent quantity is large, the cost is high), the water quality treatment effect is not reduced, the calcium and magnesium ion treatment of water can reach the standard (the calcium and magnesium ion treatment can reach the standard) (the standard of a nanofiltration membrane is reached, and the standard index is that the hardness is controlled below 35 mg/l).
In embodiment 1, the index of hardness (concentration of calcium and magnesium ions) of the raw material wastewater is 1300mg/l, the index of hardness (concentration of calcium and magnesium ions) of the concentrated water concentrated by the first reverse osmosis membrane device (sub-osmosis membrane device) is 3500mg/l and 4500mg/l, and the index of hardness (concentration of calcium and magnesium ions) of the produced water subjected to the hardness removal treatment by the high-density softening tank is less than 35mg/l, so that the calcium and magnesium ion treatment of the water quality treated in embodiment 1 can reach the standard.
The water produced after the hardness removal treatment in the high-density softening tank enters a multi-medium filter for filtration and impurity removal, and then enters a nanofiltration device for filtration, the wastewater after the nanofiltration treatment is divided into two streams, one stream (75%) of the produced water enters a medium-pressure reverse osmosis membrane device and a high-pressure reverse osmosis membrane device for membrane concentration to form produced water and further concentrated water, the second stream (25%) of the produced water and the further concentrated water enter an MVR multi-effect evaporation crystallization unit for combined evaporation crystallization and evaporation crystallization to form qualified produced water and solid salt, wherein the solid salt enters a solid salt treatment unit for treatment and then is subjected to salt separation to obtain primary salt (sodium sulfate) and secondary salt (sodium chloride).
In this embodiment 1, the raw material wastewater is concentrated by the first reverse osmosis membrane device (sub-osmosis membrane device), then is shunted by the nanofiltration device, and part of the concentrated water is subjected to membrane concentration treatment by the medium-pressure and high-pressure reverse osmosis membrane devices, so that the treatment efficiency of the MVR evaporative crystallization device can be greatly improved, and compared with the traditional high-pressure reverse osmosis treatment process in wastewater, the efficiency can be improved by 50%. In embodiment 1, the operating conditions of the MVR evaporative crystallization apparatus are as follows: PH 5.5-6.5, TDS less than or equal to 10% (mass ratio), COD less than 1500mg/l, SS less than 50mg/l, hardness (calculated by calcium carbonate) less than or equal to 300 mg/l.
In embodiment 1, the raw wastewater is concentrated by the first reverse osmosis membrane device (sub-osmosis membrane device), so that the wastewater is reduced, and calcium and magnesium ions are further enriched, therefore, the hardness removal effect of the traditional wastewater medium-high pressure reverse osmosis treatment process requiring the establishment of a two-stage high-density softened water tank can be achieved only by arranging a single-stage high-density softened water tank for hardness removal before nanofiltration, the arrangement of a second-stage high-density softened water tank after nanofiltration is eliminated, and both the construction cost and the operation cost are reduced.
In embodiment 1, the pretreatment unit, the membrane concentration unit, the evaporative crystallization unit and the solid salt treatment unit are operated in a totally closed manner when treating wastewater, so that odor is eliminated on site, no odor is emitted in the whole process, and zero emission of waste gas in the whole process of wastewater treatment can be realized.
In embodiment 1, the product water quality index of the product water tank formed after the raw material wastewater passes through the wastewater zero discharge treatment system of embodiment 1 is as follows: and (3) executing the water replenishing quality requirement of open circulating cooling water in GB/T19923-2005, wherein the hardness of main indexes is less than or equal to 35mg/l, and the TDS is less than or equal to 350 mg/l.
Embodiment mode 2
FIG. 3 is a schematic diagram of a wastewater treatment zero-discharge system according to embodiment 2; fig. 4 is a schematic diagram of a wastewater treatment zero-emission process flow according to embodiment 2. The difference from embodiment 1 is mainly as follows:
as shown in fig. 3, the wastewater zero discharge treatment system further includes a sludge treatment unit for collecting sludge generated by the membrane concentration unit, and the sludge treatment unit includes a sludge tank and a sludge dewatering device.
In the present embodiment, as shown in fig. 4, the sludge treatment unit receives sludge from the high-density softened water tank of the membrane concentration unit and processes the sludge, and in the present embodiment, the sludge dewatering equipment concentrates the sludge to prepare an auxiliary material for building materials, and the control conditions for concentrating the sludge dewatering equipment are as follows: the sludge is dehydrated after being precipitated and concentrated, a sludge dehydration device adopts a high-pressure plate-and-frame filter press, the squeezing pressure is more than or equal to 3.0MPa, the water content of the sludge is reduced to be below 50 percent, the main components of the sludge are inorganic salts such as calcium carbonate, magnesium carbonate and the like, the sludge is common industrial solid waste, and the sludge is disposed in a landfill mode or used as an auxiliary material of building materials.
In addition, in the present embodiment, in order to ensure the effect of wastewater pretreatment by adding sodium hypochlorite, a large capacity ultrafiltration water production tank is constructed, the capacity is at least 20 cubic meters, and the concentration of residual chloride ions in the ultrafiltration water production tank is controlled by detection as follows: 0.1-0.5 ppm. So as to ensure the effect of the pretreatment of the wastewater of the sodium hypochlorite and save the cost at the same time.
In embodiment 2, after the raw wastewater passes through the wastewater zero discharge treatment system of embodiment 2, the product water pool has the following water quality indexes: the hardness is less than or equal to 35mg/l, and the TDS is less than or equal to 350 mg/l.
After treatment, zero discharge of waste gas, zero discharge of waste water and reduced discharge of waste residues (sludge and solid salt) are realized.
Comparative embodiment 1
In order to compare the improvement effects of the present invention, the applicant replaced the first reverse osmosis membrane apparatus, i.e., the sub-osmosis membrane apparatus, with a conventional medium-pressure reverse osmosis membrane apparatus with reference to the process flow of embodiment 1 of the present invention, and operated the apparatus under the following conditions: the working pressure is 3-3.6 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 60-70%, and a second-stage high-density softening water tank is added after the nanofiltration equipment. The process flow of wastewater treatment of this comparative example is shown in FIG. 5.
According to comparative embodiment 1, when the quality and quantity of the raw material wastewater influent water and the operation conditions of the same units as those of embodiment 1 are controlled to be consistent as much as possible, comparative embodiment 1 cannot operate stably, and the following results are found in the experiment:
1. after the medium-pressure reverse osmosis membrane equipment connected behind the ultrafiltration equipment runs for 7-10 days, the phenomenon that the membrane separation effect is rapidly reduced occurs, and the separated produced water cannot meet the water quality requirement of the product water.
2. When the second-stage high-density softened water tank does not operate, the hardness of water entering the reverse osmosis membrane equipment is higher, and the normal operation of the reverse osmosis membrane equipment is seriously influenced.
3. The system can not realize stable operation basically, the phenomenon that the membrane holes are blocked by impurities of the separation membrane is serious, the product water quality can not be ensured, and the zero discharge of waste water can not be realized.
The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and it is apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A wastewater zero-discharge treatment system is characterized by comprising a pretreatment unit, a membrane concentration unit, an evaporative crystallization unit, a solid salt treatment unit and a product water tank, wherein the pretreatment unit, the membrane concentration unit, the evaporative crystallization unit and the solid salt treatment unit are used for sequentially treating raw wastewater; wherein the content of the first and second substances,
the raw material wastewater is wastewater subjected to aerobic treatment;
the pretreatment unit comprises a collecting water tank and ultrafiltration equipment, the membrane concentration unit comprises a first reverse osmosis membrane device, a high-density softened water tank, a multi-medium filter, nanofiltration equipment and a second reverse osmosis membrane device which are sequentially connected, and the evaporative crystallization unit comprises multi-effect evaporative crystallization equipment;
the first reverse osmosis membrane equipment is sub-osmosis membrane equipment, and the operation conditions are as follows: the working pressure is 1.2-2.3 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 65-80%.
2. The wastewater zero emission treatment system of claim 1, wherein the second reverse osmosis membrane device comprises a medium-pressure reverse osmosis membrane device and a high-pressure reverse osmosis membrane device which are connected in sequence, produced water produced by the medium-pressure reverse osmosis membrane device and the high-pressure reverse osmosis membrane device is injected into the product water pool, and concentrated water produced by the high-pressure reverse osmosis membrane device enters the evaporative crystallization unit; the operating conditions of the medium-pressure reverse osmosis membrane equipment are as follows: the working pressure is 3-3.6 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 60-70%; the operating conditions of the high-pressure reverse osmosis membrane equipment are as follows: the working pressure is 5-6.5 MPa; the operation temperature is 5-35 ℃; the desalination rate is more than 98 percent; the water recovery rate is 50-60%.
3. The zero emission wastewater treatment system of claim 1, wherein the concentrated water produced by the sub-osmotic membrane device enters the high-density softened water tank.
4. The zero discharge wastewater treatment system according to claim 2, further comprising a sludge treatment unit for collecting sludge generated from the high-density softened water tank of the membrane concentration unit.
5. The wastewater zero emission treatment system of claim 2, wherein the multi-effect evaporation and crystallization device receives concentrated water generated by the high-pressure reverse osmosis membrane device and concentrated water generated by the nanofiltration device, the produced water after evaporation and crystallization enters the product water tank, and formed solid salt enters the solid salt treatment unit.
6. The wastewater zero-discharge treatment system according to claim 1,the method is characterized in that the indexes of the water quality of the raw material wastewater are as follows: pH of 6.5-8.5, COD of 60-150 mg/L, Cl-1500-3000 mg/L of SO4 2-100-3500 mg/L of Na+500-2000 mg/L, F-1-10 mg/L of total nitrogen, 10-100 mg/L of total nitrogen, 100-1000 mg/L of calcium, 10-1000 mg/L of magnesium, 3000-9000 mg/L of TDS and 10-50 mg/L of suspended matters.
7. The wastewater zero discharge treatment system of claim 1, characterized in that the Fe in the raw wastewater is added by a strong oxidant to the pretreatment unit2+Oxidation to form Fe3+The dosage of the strong oxidant is as follows: 1 to 4 ppm.
8. The wastewater zero-discharge treatment system according to any one of claims 1 to 7, characterized in that wastewater hardness removal treatment is performed after the first reverse osmosis membrane device and before the second reverse osmosis membrane device; and the wastewater hardness removal treatment is to add a hardness removal medicament of sodium hydroxide, sodium carbonate and PAM to remove hardness of wastewater.
9. A zero discharge wastewater treatment process using the zero discharge wastewater treatment system according to any one of claims 1 to 8, comprising the steps of:
s1: raw material wastewater enters a pretreatment unit and is pretreated by a collecting tank and ultrafiltration equipment;
s2, introducing the wastewater treated in the step S1 into a membrane concentration unit for wastewater concentration and reverse osmosis treatment to form concentrated water and produced water, wherein the formed produced water enters a product water pool;
s3, carrying out evaporative crystallization treatment on the concentrated water formed after the treatment in the step S2 in an evaporative crystallization unit to form solid salt and produced water, wherein the formed produced water enters a product water pool;
and S4, carrying out salt separation treatment on the solid salt formed after the treatment of the step S3 in a solid salt treatment unit.
10. Zero waste water discharge according to claim 9A treatment process, wherein in the step S1, a strong oxidizing agent is added into the pretreatment unit to remove Fe in the raw material wastewater2+Oxidation to form Fe3+The sodium hypochlorite dosage is as follows: 1 to 4 ppm.
CN202110756811.4A 2021-07-05 2021-07-05 Wastewater zero-discharge treatment system and process Pending CN113501608A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104944636A (en) * 2015-06-07 2015-09-30 长春黄金研究院 Non-ferrous metal mine acid wastewater treatment method
US20170081217A1 (en) * 2014-05-19 2017-03-23 Bateman Advanced Technologies Ltd. Selective separation process
CN108529802A (en) * 2018-04-03 2018-09-14 山东玉鑫环保科技股份有限公司 Titanium white production discharges high slat-containing wastewater zero-emission technique
CN216472672U (en) * 2021-07-05 2022-05-10 内蒙古金河环保科技股份有限公司 Wastewater zero-discharge treatment system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170081217A1 (en) * 2014-05-19 2017-03-23 Bateman Advanced Technologies Ltd. Selective separation process
CN104944636A (en) * 2015-06-07 2015-09-30 长春黄金研究院 Non-ferrous metal mine acid wastewater treatment method
CN108529802A (en) * 2018-04-03 2018-09-14 山东玉鑫环保科技股份有限公司 Titanium white production discharges high slat-containing wastewater zero-emission technique
CN216472672U (en) * 2021-07-05 2022-05-10 内蒙古金河环保科技股份有限公司 Wastewater zero-discharge treatment system

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