Method for treating photovoltaic cell production wastewater

Abstract

The invention discloses a photovoltaic cell production wastewater treatment method which comprises the following steps: step S1, high-ammonia-nitrogen wastewater generated in photovoltaic production firstly enters a homogenizing tank, sulfuric acid is added into the homogenizing tank, the pH is adjusted to 5-7.5, and relatively stable incoming water is formed; s2, enabling effluent of the homogenizing tank to enter a high-density sedimentation tank, and adding a coagulation aid agent into the high-density sedimentation tank to precipitate original particles and dust in the effluent so as to form supernate; s3, colloid impurities in the supernate are intercepted through an ultrafiltration membrane, and purified produced water is formed; and step S4, concentrating the purified produced water through a nanofiltration membrane, concentrating ammonium sulfate salt in the produced water, feeding the produced permeate into a wastewater station, and discharging to obtain a concentrated solution, namely a high-ammonium liquid which is used as a nitrogen fertilizer. The ammonia-nitrogen wastewater is converted into a recyclable nitrogen fertilizer raw material, so that a biochemical process route with large occupied area and long operation time is avoided.

Description

Technical Field

[0001] The invention relates to a method for treating photovoltaic cell production wastewater. Background Art

[0002] At present, the treatment of photovoltaic wastewater mostly adopts the method of physical and chemical + biochemical treatment. The physical and chemical system uses chemicals (mainly calcium salts) to remove fluoride ions in the wastewater, and the biochemical uses A / O process or anaerobic ammonia oxidation process to remove ammonia nitrogen / COD in the wastewater to achieve standard discharge. The traditional treatment process requires a large amount of chemicals, a long process flow, and a large area. The most important thing is that the treated water can only be discharged as wastewater to the downstream sewage treatment plant, and it does not play a role in resource reuse. Hundreds of millions of tons of water are discharged from this industry every year, which is a great test for my country, where water resources are relatively uneven.

[0003] my country's photovoltaic industry ranks first in the world in terms of production volume. In the entire photovoltaic industry chain, the production of cells is the core process segment. Micron-level thin silicon wafers go through a series of chemical etching, soaking, chemical deposition, cleaning, and printing processes to become photovoltaic cells that can perform photoelectric conversion. In the production process of photovoltaic cells, a large amount of chemicals such as hydrofluoric acid, liquid alkali, ammonia, and hydrogen peroxide are used. Unfortunately, these chemicals do not enter the products of the cells, but are discharged as wastewater along with the cleaning. The production plant needs to add a large amount of agents to treat the wastewater and finally discharge it. According to incomplete statistics, my country's photovoltaic cell production capacity is about 1,000GW, and every 10GW of production capacity generates 15,000 tons of wastewater per day. The entire photovoltaic cell industry discharges more than 500 million cubic meters of wastewater each year, which is equivalent to 1 / 8 of the water volume of Taihu Lake. This is a huge test of the country's water resource supply capacity. Reducing wastewater discharge through technical means, and even ultimately achieving full water reuse, has far-reaching significance for the ecological environment where photovoltaic production is located and for the photovoltaic industry itself.

[0004] The wastewater from photovoltaic cell production bases can be divided into fluorine-containing dilute acid, dilute alkali, concentrated acid, and concentrated alkali wastewater, exhaust cleaning wastewater containing particulate matter, ammonia-containing silane discharge wastewater, and domestic sewage and ROR concentrated water containing organic matter and salt. It is a complex wastewater source with many pollution factors, fluctuating water quality, and uneven water volume. To solve this problem from the process technology end, we must start from the perspective of source quality classification and resource utilization, gradually reduce wastewater and ultimately achieve zero emissions. In addition, the zero-emission treatment path that exists in the field of water treatment will result in sky-high costs if it is directly used in photovoltaic wastewater, which is not feasible from an economic perspective.

[0005] Therefore, in order to solve the above problems, a method for treating photovoltaic cell production wastewater is provided. Summary of the invention

[0006] The purpose of the present invention is to overcome the existing defects and provide a method for treating photovoltaic cell production wastewater, which converts ammonia nitrogen wastewater into recyclable nitrogen fertilizer raw materials, avoiding the biochemical process route that occupies a large area and has a long operating time.

[0007] The technical solution to achieve the above purpose is: A method for treating photovoltaic cell production wastewater, comprising: Step S1, high ammonia nitrogen wastewater generated in photovoltaic production first enters a homogenization tank, sulfuric acid is added to the homogenization tank, and the pH is adjusted to between 5-7.5 to form a relatively stable inflow; Step S2, the effluent from the homogenization tank enters the high-density sedimentation tank, where coagulant aids are added to precipitate the original particles and dust in the water to form a supernatant; Step S3, the colloidal impurities in the supernatant are intercepted by an ultrafiltration membrane to form purified product water; Step S4, the purified produced water is concentrated through a nanofiltration membrane to concentrate the ammonium sulfate in the produced water, and the generated permeate enters the wastewater station for discharge. The concentrated liquid is a high-ammonium liquid, which is used as a nitrogen fertilizer.

[0008] Preferably, in step S2, the coagulant aid is one or a combination of polyaluminium chloride, ferric chloride and polyacrylamide.

[0009] Preferably, in step S3, the operating pressure of the ultrafiltration membrane is between 0.1-0.4 MPa.

[0010] Preferably, in step S3, the intercepted colloidal impurities are returned to the high-density sedimentation tank, wherein the colloidal impurities include but are not limited to silicon dioxide, aluminum hydroxide and iron hydroxide.

[0011] Preferably, in step S4, the operating pressure of the nanofiltration membrane is between 0.1-0.4 MPa, and the nanofiltration membrane is made of polyamide material.

[0012] Preferably, in step S4, the ammonium sulfate salt in the produced water is concentrated to a concentration of 10%-15%.

[0013] The beneficial effects of the present invention are as follows: the present invention converts ammonia nitrogen wastewater into recyclable nitrogen fertilizer raw materials through a homogenization tank, a high-density sedimentation tank, an ultrafiltration membrane and a nanofiltration membrane, thereby realizing resource recovery, avoiding the original biochemical treatment cost of several dozen yuan per ton, and avoiding the construction of large-scale biochemical treatment pools and the construction land occupation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of a method for treating photovoltaic cell production wastewater. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0016] The present invention will be further described below in conjunction with the accompanying drawings.

[0017] like Figure 1 As shown, a method for treating photovoltaic cell production wastewater comprises: Step S1, high ammonia nitrogen wastewater generated in photovoltaic production first enters the homogenization tank, sulfuric acid is added to the homogenization tank, and the pH is adjusted to between 5-7.5 to form a relatively stable incoming water.

[0018] Step S2, the effluent from the homogenization tank enters the high-density sedimentation tank, where coagulant aids are added to precipitate the original particles and dust in the water to form a supernatant.

[0019] In the embodiment, the coagulant aid is one or a combination of polyaluminium chloride, ferric chloride and polyacrylamide.

[0020] In step S3, the colloidal impurities in the supernatant are intercepted by an ultrafiltration membrane to form purified product water.

[0021] In the embodiment, the operating pressure of the ultrafiltration membrane is between 0.1-0.4 MPa.

[0022] In the embodiment, the intercepted colloidal impurities are returned to the high-density sedimentation tank, wherein the colloidal impurities include but are not limited to silicon dioxide, aluminum hydroxide and iron hydroxide.

[0023] Step S4, the purified produced water is concentrated through a nanofiltration membrane to concentrate the ammonium sulfate in the produced water, and the generated permeate enters the wastewater station for discharge. The concentrated liquid is a high-ammonium liquid, which is used as a nitrogen fertilizer.

[0024] In the embodiment, the operating pressure of the nanofiltration membrane is between 0.1-0.4 MPa, and the nanofiltration membrane is made of polyamide material.

[0025] In the embodiment, the ammonium sulfate salt in the produced water is concentrated to a concentration of 10%-15%.

[0026] The invention converts ammonia nitrogen wastewater into a nitrogen fertilizer raw material that can be recycled, thus avoiding a biochemical process route that occupies a large area and has a long operating time.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating photovoltaic cell production wastewater, characterized in that: include: Step S1, high ammonia nitrogen wastewater generated in photovoltaic production first enters a homogenization tank, sulfuric acid is added to the homogenization tank, and the pH is adjusted to between 5-7.5 to form a relatively stable inflow; Step S2, the effluent from the homogenization tank enters the high-density sedimentation tank, where coagulant aids are added to precipitate the original particles and dust in the water to form a supernatant; Step S3, the colloidal impurities in the supernatant are intercepted by an ultrafiltration membrane to form purified product water; Step S4, the purified produced water is concentrated through a nanofiltration membrane to concentrate the ammonium sulfate in the produced water, and the generated permeate enters the wastewater station for discharge. The concentrated liquid is a high-ammonium liquid, which is used as a nitrogen fertilizer.

2. The method for treating photovoltaic cell production wastewater according to claim 1, characterized in that: In step S2, the coagulant aid is one or a combination of polyaluminium chloride, ferric chloride and polyacrylamide.

3. The method for treating photovoltaic cell production wastewater according to claim 1, characterized in that: In step S3, the operating pressure of the ultrafiltration membrane is between 0.1-0.4 MPa.

4. The method for treating photovoltaic cell production wastewater according to claim 1, characterized in that: In step S3, the intercepted colloidal impurities flow back into the high-density sedimentation tank, wherein the colloidal impurities include but are not limited to silicon dioxide, aluminum hydroxide and iron hydroxide.

5. The method for treating photovoltaic cell production wastewater according to claim 1, characterized in that: In step S4, the operating pressure of the nanofiltration membrane is between 0.1-0.4 MPa, and the nanofiltration membrane is made of polyamide material.

6. The method for treating photovoltaic cell production wastewater according to claim 1, characterized in that: In step S4, the ammonium sulfate in the produced water is concentrated to a concentration of 10%-15%.

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