WO2011015041A1

WO2011015041A1 - Wastewater treatment method and system using the method

Info

Publication number: WO2011015041A1
Application number: PCT/CN2010/001210
Authority: WO
Inventors: 刘继斌; 汲江; 丁志伟; 胡晓宏; 单德生; 谭清; 陆海锋
Original assignee: 无锡尚德太阳能电力有限公司; 无锡江天高新纳米技术材料有限公司
Priority date: 2009-08-07
Filing date: 2010-08-09
Publication date: 2011-02-10
Also published as: CN101987765B; CN101987765A

Abstract

A wastewater treatment method is provided. In the method, firstly the wastewater is concentrated by a nanofiltration membrane, so that the concentration of divalent or polyvalent metallic ion in the wastewater is close to the saturation state. Then a crystal seed is added for inducing crystallization. Furthermore, residual metallic ions and other impurities in the wastewater are filtered by a reverse osmosis membrane, so that reuse water is obtained. At the same time, a system using the method is provided. By the method, the divalent or polyvalent metallic ions in the wastewater are removed more effectively, and zero discharge is realized.

Description

Sewage treatment method and system used in the same

The present invention relates to the field of industrial wastewater treatment, and more particularly to a method for treating heavy metal ion-containing sewage in the solar industry, electroplating industry, semiconductor and microelectronics industries. In particular, the present invention relates to a sewage treatment method and a system for use in the treatment method.

BACKGROUND OF THE INVENTION In the manufacturing process of photovoltaic products, the solar industry uses a large amount of harmful substances such as hydrofluoric acid and heavy metal organic substances, such as heavy metal ions such as nickel, copper, silver, chromium, and mercury, or polyacrylic acid and polypyrrole. An organic substance formed by a ketone, polyethylene glycol, polystyrene acid, polyethylenediamine or the like. The composition of the wastewater produced by the above manufacturing process is complex and extremely difficult to handle. The current environmental protection requirements for industrial wastewater discharge standards are extremely strict. At present, there is no effective way to truly achieve zero discharge of industrial wastewater containing heavy metal ions. Since the concentration of heavy metal ions in industrial wastewater is generally low, these heavy metal ions cannot be effectively removed using only conventional precipitation methods. In the current sewage treatment, nanofiltration membranes or reverse osmosis membranes have been introduced into the sewage treatment process, but they are generally used alone. When the nanofiltration membrane is used alone, the interception rate of metal ions such as copper ions is too low due to a large flux, and the ion removal rate is not greatly improved. The reverse osmosis membrane alone uses a low flux, a low flux, a high operating pressure, and a high energy consumption, so the overall efficiency is low and uncompetitive. It can be said that the method of separately using membrane filtration not only fails to achieve the purpose of completely removing heavy metal ions, but also causes membrane fouling, and therefore is not practical. When the sewage is treated by the method of concentration and reprecipitation first, the reverse osmosis membrane is generally selected for the purpose of concentration without selecting the nanofiltration membrane, but this will seriously contaminate the reverse osmosis membrane. In the solar, electroplating, semiconductor and microelectronics industries, there is an urgent need to develop a treatment that achieves zero discharge of wastewater.

Summary of the invention

Purpose of the invention It is an object of the present invention to provide a sewage treatment method capable of effectively achieving zero discharge of sewage in the solar energy industry and related industries. Another object of the present invention is to provide a system capable of effectively implementing the above sewage treatment method. Technical Solution In order to achieve the above object, the present invention provides a sewage treatment method, which comprises the following steps:

1) Concentrate the raw sewage water with a nanofiltration membrane at room temperature so that the concentration of the two or more valence metal ions is close to saturation, wherein the pressure during filtration is 0.1 to 10 MPa, preferably 1 to 5 Mp, Preferably about 2 Mpa;

2) adding an appropriate amount of seed crystals to the concentrated sewage obtained in the above step 1) and adjusting the pH value of the sewage to induce crystallization of metal ions to crystallize out from the sewage;

3) Using a reverse osmosis membrane at room temperature to filter the metal ions and other impurities remaining in the sewage filtered by the nanofiltration membrane to obtain recyclable water, wherein the filtration pressure is 0.1 to 10 MPa, preferably It is 1 to 5 Mp, more preferably about 2 MPa. In the above step 1), the nanofiltration membrane is not particularly limited, and any commercially available nanofiltration membrane having a sodium chloride intercept rate of 40% or more can be used as the nanofiltration membrane of the present invention. Further, in the range of pH 3 to 10, the higher the pH, the higher the shutoff rate for various ions. The best separation results when the pH is in the range of 6 to 10. In this step, if the copper-containing sewage is treated, when the initial concentration of copper ions is about 0.2 _W t% to 0.4 wt%, the concentration is concentrated by about 40 to 20 times after being filtered by the nanofiltration membrane. The final concentration of copper ions is about 8 wt%, which is close to saturation. If the nickel-containing wastewater is treated, when the initial concentration of nickel ions is about 0.8 wt% 1.6 wt%, the concentration is concentrated about 10 to 5 times after filtration through the nanofiltration membrane, and the final concentration of nickel ions is about It is 8 wt%, close to saturation. In the above step 2), the seed crystal is one or several chemicals, and the substances are added to the solution containing heavy metal ions, so that the concentration of the heavy metal ions is close to saturation, so that the solution is crystallized and precipitated to be heavy metal ions. separate from. For example, sodium hydroxide can be used as a heavy metal ion Seed crystal. However, the seed crystal which can be used in the present invention is not limited to sodium hydroxide, such as lithium hydroxide, potassium hydroxide, iron chloride, aluminum chloride or the like. The separated heavy metal precipitate can be post-treated for recycling. In this step, in the case where the temperature (room temperature) and the pH (pH value of 3 to 10) are substantially determined, it can be determined according to the solubility product constant of the heavy metal ion to be removed, the concentration, the volume of the raw sewage water, and the pH value. The amount of seed crystal to be added. For different metal ions, the concentration is close to saturation or the pH of the precipitate is different. The pH required to precipitate different metal ions can be determined according to Figure 1; when the solution contains different metal ions at the same time, A suitable pH can be chosen to simultaneously precipitate multiple metal ions. In the above step 3), the reverse osmosis membrane is not particularly limited, and any commercially available reverse osmosis membrane having a sodium chloride intercept rate of 90% or more can be used as the reverse osmosis membrane of the present invention. Further, in the range of pH 3 to 10, the higher the pH value, the higher the shutoff rate for various ions. Preferably, in order to further improve the recovery rate of the metal and reach the discharge standard, the sewage treatment method of the present invention further includes the following steps according to the concentration of the metal ions in the raw water of the sewage:

4) Add appropriate amount of seed crystals to the filtered sewage containing metal ions and other impurities obtained in the above step 3) and adjust the pH of the sewage to induce crystallization of metal ions to crystallize out from the sewage. The seeds used in this step are similar to those in step 2). The separated heavy metal precipitate can be post-treated for recycling. In order to obtain better sewage treatment effect and achieve zero discharge of sewage, the nanofiltration membrane of the first step 1) may be filtered one or more times after the solution of the induced crystallization step 2) and/or the step 4). Times. In order to produce ultrapure water from sewage containing heavy metal ions, the sewage treatment method of the present invention may further comprise any one or two of steps 5) and 5):

5) using a cation exchange resin or / and an anion exchange resin to further treat the water obtained in the step 3);

6) Use activated carbon to treat the water obtained in step 3) or step 5). In the above step 5), the ion exchange resin is not particularly limited, and any commercially available anion/cation exchange resin can be used as the ion exchange resin of the present invention. In addition, the sewage treatment method of the present invention further comprises the following steps: filtering the suspended particles in the sewage by using a filtering unit before the step 1) and/or the step 3) to protect the corresponding filter membrane . The filter unit achieves the corresponding protection purpose by adding a protective filter medium (such as sand filter, polypropylene filter, etc.). In order to effectively implement the above sewage treatment method, another aspect of the present invention provides a system for the above sewage treatment method, the system comprising: a primary feed water tank unit for storing raw sewage water, the unit may be included as needed One or more inlet water storage tanks; a nanofiltration membrane unit connected to the first-stage water storage tank unit for performing the first-stage nanofiltration membrane concentration filtration on the sewage, wherein there is no particular limitation on the nanofiltration membrane, As long as it is a commercial nanofiltration membrane having a sodium chloride intercept rate of 40% or more, it can be used as the nanofiltration membrane of the present invention; the first stationary storage tank unit is connected to the nanofiltration membrane unit for passing Seed crystals are added to the concentrated sewage of the nanofiltration membrane to induce crystallization. The unit may include one or more static storage tanks as needed; a secondary water storage tank unit connected to the nanofiltration membrane unit for storing the above The sewage filtered by the nanofiltration membrane is a water inlet tank for secondary reverse osmosis filtration. The unit may include one or more inlet water storage tanks as needed; reverse osmosis membrane single And the second inlet water storage tank unit is connected to the second reverse osmosis filtration of the sewage filtered by the nanofiltration membrane, and the reverse osmosis membrane is not particularly limited as long as the sodium chloride intercept rate is More than 90% of commercially available reverse osmosis membranes can be used as the reverse osmosis membrane of the present invention; the effluent tank unit is connected to the reverse osmosis membrane unit for storing water filtered through two stages, the water Recycling standards can be recycled. Preferably, the sewage treatment system of the present invention further comprises: a second stationary storage tank unit connected to the reverse osmosis membrane unit for passing Seed crystals are added to the sewage filtered by the reverse osmosis membrane to induce crystallization, and the metal ions are crystallized and precipitated to separate the metal ions. The unit may include one or more static storage tanks as needed. In order to achieve better sewage treatment effect and achieve zero discharge of sewage, the first stationary storage tank unit and/or the second stationary storage tank unit may be connected to the primary water storage tank unit through The pump introduces the solution remaining after the induced crystallization into the primary feed water tank unit to repeat the nanofiltration membrane filtration one or more times. In order to purify the water subjected to the two-stage filtration to produce ultrapure water satisfying special use requirements, the sewage treatment system of the present invention may further comprise any one or two of the following two units: an ion exchange treatment unit, which The effluent tank unit is connected, the unit comprising a cation exchange resin or/and an anion exchange resin, wherein any commercially available anion/cation exchange resin can be used as the ion exchange resin of the present invention; and an activated carbon treatment unit, which is combined with an effluent storage tank The unit or ion exchange processing unit is connected. In order to protect the corresponding filter membrane, the sewage treatment system of the present invention may further comprise: a filtration unit, which may be disposed before the nanofiltration membrane unit and/or the reverse osmosis membrane unit for removing suspended particles and corresponding The filter membrane provides protection and may include a sand filter and/or a polypropylene depth filter. The filter unit achieves the corresponding protection purpose by adding a protective filter medium (such as sand filter, polypropylene filter, etc.). Advantageous Effects The sewage treatment method provided by the present invention has the following advantages: First, the raw water of the sewage is concentrated by using a nanofiltration membrane, so that the concentration of the metal ions of two or more valences is close to a saturated state, and then the seed crystal is added to induce crystallization. This can remove the divalent or multivalent heavy metal ions in the sewage more effectively than the traditional precipitation method, and can also avoid the contamination of the reverse osmosis membrane by the next enthalpy; secondly, the reverse osmosis membrane is used to further filter the residue. Metal ions and other impurities in the sewage filtered by the nanofiltration membrane to obtain recyclable water and achieve zero discharge; Third, optionally pass the anion/cation exchange resin and/or activated carbon after the reverse osmosis membrane The treatment can realize the purpose of producing ultrapure water from the sewage industry containing heavy metal ions. Therefore, the method and system provided by the present invention can not only effectively remove heavy metal ions from sewage, thereby achieving zero discharge of sewage in the solar industry and related industries, but also providing recyclable water (recycling:) and ultrapure water. Reduce production costs accordingly. The sewage treatment method provided by the invention and the system used in the treatment method can be applied to the treatment of sewage in the solar energy industry, the electroplating industry, the semiconductor and the microelectronics industry, in particular, the treatment of sewage in the manufacturing process of photovoltaic products, Good practical processing results, thus providing an effective treatment method and system for the photovoltaic cell wastewater treatment industry. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing a relationship between a pH value and a metal concentration when a metal hydroxide forms a precipitate; FIG. 2 is a schematic view of a system for sewage treatment according to a preferred embodiment of the present invention; A schematic diagram of a system for wastewater treatment provided by another preferred embodiment of the invention; and Figure 4 is a schematic illustration of a system for wastewater treatment provided by a further preferred embodiment of the present invention. Wherein, 1 is the water inlet pipeline; 2 and 3 are the first-stage water storage tank; 4 is the control valve; 5 is the first stationary storage tank; 6 is the second stationary storage tank; 7 is the pump;

8 and 14 are filters;

9 is a nanofiltration membrane unit;

10 and 11 are secondary feed water storage tanks;

15 is a reverse osmosis membrane unit; 16 is the water storage tank; 18 pipeline;

19A is a cation exchange resin; 19B is an anion exchange resin; 19C is an activated carbon treatment unit; and 20 is a water outlet line.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail. It is to be understood that the following examples are merely illustrative and are not intended to limit the invention. Embodiment 1.1 FIG. 2 is a schematic diagram of a system for sewage treatment provided by the present invention. The sewage treatment system of the present invention comprises: a first-stage water storage tank 2 and 3 for storing sewage raw water; a nanofiltration membrane unit 9 connected to the primary feed water storage tanks 2, 3 for performing the sewage The nanofiltration membrane is concentrated and filtered, wherein the nanofiltration membrane uses a commercially available commercial nanofiltration membrane with a sodium chloride intercept rate of 40% or more; the first stationary storage tank 5 is connected to the nanofiltration membrane unit 9 for Seed crystals are added to the sewage concentrated by the nanofiltration membrane to induce crystallization; secondary water storage tanks 10 and 11 are connected to the nanofiltration membrane unit 9 for storing the above-mentioned sewage filtered through the nanofiltration membrane, which is a reverse osmosis filtration water inlet tank; a reverse osmosis membrane unit 15 connected to the secondary water storage tanks 10, 11 for performing secondary reverse osmosis filtration on the sewage filtered by the nanofiltration membrane, wherein The reverse osmosis membrane adopts a commercially available reverse osmosis membrane with a sodium chloride intercept rate of 90% or more; The effluent storage tank 16, which is connected to the reverse osmosis membrane unit 15, is used for storing water that has been filtered through two stages, and the water reaches the reuse standard and can be recycled. Preferably, the sewage treatment system of the present embodiment further comprises: a second stationary storage tank 6 connected to the reverse osmosis membrane unit 15 for reverse osmosis filtration according to the concentration of the metal ions in the raw water of the sewage. Seed crystals are added to the membrane-filtered sewage to induce crystallization, and the metal ions are crystallized and precipitated to separate the metal ions. In order to achieve a better sewage treatment effect and achieve zero discharge of sewage, the first stationary storage tank 5 and/or the second stationary storage tank 6 described above are connected to the primary water storage tanks 2, 3, The solution remaining after the induced crystallization is introduced into the primary feed water tank 2, 3 by a pump, and the nanofiltration membrane is repeatedly filtered one or more times. Preferably, the sewage treatment system of the present embodiment further includes filters 8 and/or 14 disposed before the nanofiltration membrane unit 9 and/or the reverse osmosis membrane unit 15, depending on the degree of contamination of the sewage to be treated, It is used to remove suspended particles to protect the filter behind it, including sand filters and/or polypropylene depth filters. The sewage treatment system of the present embodiment first concentrates the raw sewage water to be treated with a nanofiltration membrane to make it saturated or nearly saturated, and then induces crystallization by using ferric chloride, sodium hydroxide or the like to make it from the solution. The crystals are precipitated; the water passing through the nanofiltration membrane is filtered by a reverse osmosis membrane to remove residual metal ions and other impurities. In addition, the saturated solution remaining after induction of crystallization can be transferred to the primary feed water tank for recycling, so that the treated water can meet the specified discharge standards or recyclable standards, thereby achieving zero emissions. Embodiment 1.2 FIG. 3 is a schematic view of another sewage treatment system provided by the present invention. The sewage treatment system shown in Fig. 3 further includes a cation exchange resin 19A, an anion exchange resin 19B, and a water discharge line 20, and a cation exchange resin 19A is connected to the water discharge tank 16 through a line 18, anion, as compared with the system shown in Fig. 2. The exchange resin 19B is connected to the water outlet line 20. Embodiment 1.3 FIG. 4 is a schematic view of still another sewage treatment system according to the present invention. Compared with the system shown in Fig. 3, the sewage treatment system shown in Fig. 4 further includes an activated carbon treatment unit 19C in which the cation is separated The sub-exchange resin 19A is connected to the outlet tank 16 via a line 18, the cation exchange resin 19A, the anion exchange resin 19B and the activated carbon treatment unit 19C are connected, and the activated carbon treatment unit 19C is connected to the outlet line 20. It should be understood that the activated carbon treatment unit 19C of the present embodiment and the cation exchange resin 19A and the anion exchange resin 19B of the embodiment 1.2 may be used at different times, that is, the activated carbon treatment unit 19C of the present embodiment may be separately combined with the system shown in FIG. In conjunction with. The sewage treated by the treatment systems of Examples 1.2 and 1.3 can reach the standard of ultrapure water. Example 2.1 Table 1 below shows an example of the results of treatment of copper-containing wastewater in the solar industry using the sewage treatment system of Example 1.1. In this example, the raw water of the sewage has a pH of 5 to 8. At room temperature, the NF270 nanofiltration membrane of Dow Chemical Company is used to concentrate the raw sewage water, so that the concentration of copper ions in the sewage is close to saturation, wherein the pressure during filtration is 0.1~2 MPa, and the seed crystal added to the sewage is Sodium hydroxide, using sodium hydroxide to adjust the pH of the sewage to about 9.5, thereby inducing the crystallization of copper ions to crystallize out of the sewage. The solution remaining after the induced crystallization was again subjected to nanofiltration membrane filtration. Next, the Dow Chemical Company's SW30 reverse osmosis membrane was used at room temperature to remove copper ions and other impurities remaining in the sewage to obtain recyclable water. The results of the effluent water quality obtained by the treatment of the sewage treatment system of Example 1.1 are shown in Table 1: Table 1

Example 2.2 Table 2 below shows an example of the results of treatment of wastewater containing various metal ions in the solar industry using the sewage treatment system of Example 1.1. In this example, the raw water of the sewage has a pH of 5 to 6, and the raw water of the sewage is concentrated at room temperature using the NF270 nanofiltration membrane of the Dow Chemical Company, so that the concentration of the metal ions in the sewage is close to saturation, wherein when filtering The pressure is 0.1~2 MPa, the seed crystal added to the sewage is sodium hydroxide, and the pH of the sewage is adjusted to about 10.2 by using sodium hydroxide, thereby inducing crystallization of each ion to crystallize it out from the sewage. The solution remaining after the induced crystallization was again subjected to nanofiltration membrane filtration. Next, the Dow Chemical Company's SW30 reverse osmosis membrane was used at room temperature to remove metal ions and other impurities remaining in the sewage to obtain recyclable water. The results of the effluent water quality obtained after the treatment process of the sewage treatment system of Example 1.1 are shown in Table 2: Table 2

The above description is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. It is to be understood that those skilled in the art, without departing from the spirit and scope of the invention, are still within the scope of the invention.

Claims

Rights request

1. A sewage treatment method, the method comprising the following steps:

1) Concentrating the raw sewage water with a nanofiltration membrane at room temperature, so that the concentration of the metal ions above and below the two valences is close to saturation, wherein the pressure during filtration is 0.1 to 10 MPa _;

3) The metal ions and other impurities remaining in the sewage which has been filtered by the nanofiltration membrane are filtered at room temperature using a reverse osmosis membrane to obtain recyclable water, wherein the pressure at the filtration is 0.1 to 10 MPa.

The sewage treatment method according to claim 1, wherein the seed crystal used in the step 2) is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide, iron chloride, aluminum chloride, and a mixture thereof.

3. The sewage treatment method according to claim 1, further comprising the following steps:

4) Add appropriate amount of seed crystals to the filtered sewage containing metal ions and other impurities obtained in the above step 3) and adjust the pH of the sewage to induce crystallization of metal ions to crystallize out from the sewage.

The sewage treatment method according to any one of claims 1 to 3, which further comprises any one or two of the steps 5) and 6):

6) Use activated carbon to treat the water obtained in step 3) or step 5).

The sewage treatment method according to any one of claims 1 to 3, further comprising the step of repeating the solution remaining after the induced crystallization step 2) and/or the step 4) The nanofiltration membrane of step 1) is filtered one or more times.

6. A sewage treatment method according to any one of claims 1 to 3, further comprising the step of using a filtration unit for suspended particles in the sewage prior to step 1) and/or step 3) Filter.

The sewage treatment method according to any one of claims 1 to 3, wherein, in the steps 1) and 3), the pressure at the time of filtration is 1 to 5 Mpa.

The sewage treatment method according to any one of claims 1 to 3, wherein, in the steps 1) and 3), the pH at the time of filtration is 3 to 10.

9. A system for use in a sewage treatment method according to any one of claims 1 to 8, the system comprising: a primary feed water storage tank unit for storing raw sewage water; a nanofiltration membrane unit, and a primary The water storage tank unit is connected to perform the first-stage nanofiltration membrane concentration filtration on the sewage; the first static storage tank unit is connected to the nanofiltration membrane unit for adding to the sewage concentrated by the nanofiltration membrane. The seed crystal is induced to crystallize; the secondary water storage tank unit is connected to the nanofiltration membrane unit for storing the above-mentioned sewage filtered by the nanofiltration membrane, and is a water inlet tank for secondary reverse osmosis filtration; reverse osmosis membrane a unit connected to the secondary feed water storage tank unit for performing secondary reverse osmosis filtration on the sewage filtered by the nanofiltration membrane; and a effluent storage tank unit connected to the reverse osmosis membrane unit for storage Two levels of filtered water.

10. The sewage treatment system according to claim 9, further comprising: a second stationary storage tank unit connected to the reverse osmosis membrane unit for adding to the sewage filtered through the reverse osmosis membrane The seed crystals are induced to crystallize.

The sewage treatment system according to claim 10, wherein the first stationary storage tank unit and/or the second stationary storage tank unit are connected to the primary feed water storage tank unit.

12. A sewage treatment system according to any one of claims 9 to 11 further comprising one or both of the following two units: an ion exchange treatment unit coupled to the outlet tank unit, The unit comprises a cation exchange resin or/and an anion exchange resin; and an activated carbon treatment unit connected to the effluent tank unit or the ion exchange treatment unit.

13. A sewage treatment system according to any one of claims 9 to 11, the system further comprising: a filtration unit disposed in front of the nanofiltration membrane unit and/or the reverse osmosis membrane unit for removing the suspension particle.

The sewage treatment system according to claim 13, wherein the filtration unit comprises a sand filter and/or a polypropylene depth filter.