A near-zero discharge treatment process for wastewater in a chemical park

Abstract

The invention discloses a near-zero emission treatment process for wastewater in a chemical park. The process firstly mixes organic wastewater and inorganic wastewater of secondary biochemical effluent of the chemical park in a volume ratio (1:1), then uses Ca(OH)2 to soften the wastewater, and after the softened effluent is removed by an ultrafiltration system with part of suspended solids and macromolecular colloids, first enters a first-stage reverse osmosis system for desalination, controls the recovery rate at 70%, produces water for reuse, and obtains first-stage reverse osmosis concentrated water and then enters the reverse osmosis system for treatment. After the first-stage and second-stage reverse osmosis treatment, the total water recovery rate can reach about 90%, produces water for reuse, and the generated first-stage and second-stage reverse osmosis concentrated water enters a catalytic ozone oxidation unit to mineralize part of organic matter, and the effluent enters a biological activated carbon unit, and utilizes the synergistic effect of activated carbon adsorption and microbial oxidation and decomposition of organic matter to further remove the organic matter content in the first-stage and second-stage reverse osmosis concentrated water, so that the concentrated water meets the discharge standards.

Description

Technical Field

[0001] The invention belongs to an industrial wastewater deep treatment process, and in particular relates to a near-zero emission treatment process for wastewater in a chemical park. Background Art

[0002] At present, my country is facing a serious water shortage problem. In order to save water resources, my country has put forward higher requirements for industrial wastewater treatment. In this context, the emergence of the concept of near-zero emission provides guidance for industrial wastewater treatment. Applying the concept of near-zero emission to the research of industrial wastewater treatment technology can promote the development and progress of industrial wastewater treatment technology, thereby completely changing the extensive mode of industrial wastewater treatment and achieving effective control of water pollution. In recent years, my country has also explored and practiced the field of near-zero emission of industrial wastewater. For example, the Ordos coal-to-liquid unit of Shenhua Group, as the world's first million-ton coal direct liquefaction project, adopts enhanced catalytic degradation pretreatment, concentration, evaporation and crystallization and other technical means, becoming the first near-zero emission demonstration project of high-concentration wastewater in my country's coal chemical industry.

[0003] However, at present, the technical support for deep treatment and reuse of wastewater in typical water-consuming industries (such as microelectronics, chemicals, etc.) in my country's high-tech parks is insufficient, and there is still a large gap from near-zero discharge, which restricts the efficient recycling of water resources in high-tech parks. How to break through the key technical bottlenecks of wastewater treatment and recycling in chemical parks based on the construction needs of near-zero discharge of wastewater in chemical parks, combined with the current status and future development trends of the parks, and establish a wastewater near-zero discharge pollutant reduction and water reuse technology system is of great significance to the green and sustainable development of the parks.

[0004] Therefore, in view of the characteristics of chemical park wastewater, such as complex composition, difficult biodegradation, and high salt content, the present invention develops a combined process for chemical wastewater treatment based on the ultrafiltration-reverse osmosis double membrane method, as well as a technology for deep reduction of typical pollutants in the concentrate of the membrane system. This forms a combined wastewater treatment process for the purpose of pollutant reduction and water reuse, and achieves near-zero discharge of wastewater from chemical parks. Summary of the invention

[0005] In response to the above problems, the present invention provides a treatment process for near-zero discharge of wastewater in chemical parks. The process is coupled by multiple technical means and can specifically remove the hardness and organic matter in the wastewater, thereby achieving the goal of near-zero discharge of wastewater.

[0006] The technical solution of the present invention is: a near-zero discharge treatment process for wastewater in a chemical park, which comprises the following steps:

[0007] (1) Mix the organic wastewater and inorganic wastewater from the secondary biochemical effluent of the chemical park in a volume ratio of (1:1).

[0008] (2) Use Ca(OH)2 to soften the mixed water sample in step (1) to remove Ca in the wastewater. 2+ Mg 2+ , the dosage of Ca(OH)2 is 300 mg / L, and the hardness in the wastewater is reduced to 66 mg / L (measured in CaCO3), creating good conditions for the efficient operation of the subsequent membrane system.

[0009] (3) The water sample softened in step (2) is passed through an ultrafiltration system to remove some suspended solids and macromolecular colloids as a pretreatment process for reverse osmosis.

[0010] (4) The water treated in step (3) enters the first-stage reverse osmosis system, with the system pressure controlled at 6 bar, the produced water flow rate at 3 L / min, the concentrate flow rate at 700 L / h, and the first-stage reverse osmosis recovery rate at 70%. The produced water is reused, and the concentrate enters the reverse osmosis system for further concentration.

[0011] (5) The first-stage reverse osmosis concentrate obtained in step (4) enters the reverse osmosis system for second-stage reverse osmosis treatment. At this time, the reverse osmosis system operates under high pressure conditions, with a control system pressure of 14 bar, a water production flow rate of 2.6 L / min, and a concentrate flow rate of 700 L / min. After the first-stage and second-stage reverse osmosis, the total water recovery rate can reach about 90%, the produced water can be directly reused, and the reverse osmosis concentrate is further treated in the next step.

[0012] (6) The reverse osmosis concentrate produced in step (5) is treated by a catalytic ozone oxidation unit using a Fe-Al2O3 supported catalyst to remove part of the organic matter in the concentrate.

[0013] (7) The effluent from the catalytic ozone oxidation produced in step (6) enters the biological activated carbon unit, where the adsorption capacity of the activated carbon and the degradation capacity of the microorganisms are used to further remove organic matter, so that the concentrated water meets the discharge standards.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. Removal of Ca from wastewater by Ca(OH)2 softening 2+ Mg 2+ , so that water entering the reverse osmosis device is not easy to scale, extend the service life of the reverse osmosis membrane, and at the same time improve the recovery rate of the reverse osmosis system.

[0016] 2. Using Ca(OH)2 to soften wastewater reduces the operating cost of the entire treatment process.

[0017] 3. The "double membrane method" is used to treat wastewater, the desalination rate can reach about 99%, and the total water recovery rate can reach about 90%. It has the advantages of good effluent water quality, easy self-control, small footprint, water saving and environmental protection.

[0018] 4. Through the coordinated use of a variety of technical means, the hardness and organic matter of wastewater can be removed in a targeted manner. Each system plays a different role and cooperates with each other to achieve the goal of near-zero emissions, reduce environmental pollution and save water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a process flow chart of a near-zero discharge treatment process for wastewater in a chemical park according to the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below with reference to the accompanying drawings and examples:

[0021] like Figure 1 As shown in the figure, a near-zero emission treatment process for wastewater from a chemical park is used. The organic wastewater and inorganic wastewater from the chemical park are first mixed in a volume ratio (1:1), and the wastewater is softened by using Ca(OH)2. The softened effluent then enters an ultrafiltration system to remove part of the suspended solids and macromolecular colloids. The ultrafiltration effluent first enters a first-stage reverse osmosis system for desalination, and the recovery rate is controlled at 70%. The produced water is reused, and the first-stage reverse osmosis concentrated water obtained enters a reverse osmosis system for treatment. After a first-stage and second-stage reverse osmosis, the total water recovery rate can reach about 90%, and the produced water is reused. The reverse osmosis concentrated water enters a catalytic ozone oxidation unit to mineralize part of the organic matter, and the effluent enters a biological activated carbon unit. The synergistic effect of activated carbon adsorption and microbial oxidation and decomposition of organic matter is used to further remove the organic matter content in the reverse osmosis concentrated water, so that the concentrated water meets the discharge standards.

[0022] The specific implementation process of this embodiment is as follows:

[0023] The organic wastewater and inorganic wastewater of the secondary biochemical effluent of Shanghai Chemical Park were mixed in a volume ratio of 1:1, with a COD of 55 mg / L and a hardness of 268 mg / L (calculated as CaCO3). The wastewater was first softened with Ca(OH)2, and the dosage of Ca(OH)2 was 300 mg / L, which reduced the hardness of the wastewater to 66 mg / L (calculated as CaCO3). The softened effluent was then removed by the ultrafiltration system to remove some suspended solids and macromolecular colloids. The COD of the ultrafiltration effluent was 40 mg / L. The ultrafiltration effluent first entered the first-stage reverse osmosis system for desalination. The control system pressure was 6 bar, the water production flow rate was 3 L / min, the concentrated water flow rate was 700 L / h, and the recovery rate was 70%. The produced water was reused, and the concentrated water COD was about 90 mg / L. The first-stage reverse osmosis concentrated water then entered the reverse osmosis system for treatment. The control system pressure was 14 bar, the water production flow rate was 2.6 L / min, and the concentrated water flow rate was 700 L / h. L / min, water is reused, and after the first-stage and second-stage reverse osmosis, the total water recovery rate can reach about 90%, and the COD of the first-stage and second-stage reverse osmosis concentrated water produced is about 200 mg / L. The first-stage and second-stage reverse osmosis concentrated water enters the catalytic ozone oxidation unit, which is loaded with Fe-Al2O3 supported catalyst, with a catalyst dosage of 100 g / L, a reaction time of 10 min, an ozone concentration of 30 mg / L, and COD reduced to about 120 mg / L. The effluent enters the biological activated carbon unit to further reduce the organic matter content. The empty bed residence time is 60 min, and the COD can be reduced to below 60 mg / L, reaching the secondary discharge standard (COD≤60 mg / L) of the Shanghai "Comprehensive Wastewater Discharge Standard" (DB31 / 199-2018) implemented by the Shanghai Chemical Industry Park.

[0024] This embodiment adopts this method to treat the wastewater from Shanghai Chemical Industry Park, which can effectively remove organic matter in the wastewater. While solving the difficulty of wastewater treatment, it can maximize the recovery of water resources and achieve near-zero discharge of wastewater from the chemical industry park.

Claims

1. A near-zero discharge treatment process for wastewater in a chemical park, characterized in that: The organic wastewater and inorganic wastewater of the chemical park are mixed in a volume ratio of (1:1), and the wastewater is first softened by Ca(OH)2. The softened effluent enters the ultrafiltration system to remove part of the suspended solids and macromolecular colloids. The ultrafiltration effluent first enters the first-stage reverse osmosis system for desalination. At this time, the reverse osmosis system operates under low pressure conditions, and the recovery rate is controlled at 70%. The produced water is reused, and the first-stage reverse osmosis concentrated water obtained enters the reverse osmosis system for treatment. At this time, the reverse osmosis system operates under high pressure conditions. After the first-stage and second-stage reverse osmosis, the total water recovery rate can reach about 90%, and the produced water is reused. The reverse osmosis concentrated water enters the catalytic ozone oxidation unit to mineralize part of the organic matter, and the effluent enters the biological activated carbon unit. The synergistic effect of activated carbon adsorption and microbial oxidation and decomposition of organic matter is used to further remove the organic matter content in the reverse osmosis concentrated water, so that the concentrated water meets the discharge standards; The first stage reverse osmosis control working pressure is 6 bar, the concentrated water flow rate is 700 L / min, and the produced water flow rate is 3 L / min; The second-stage reverse osmosis is controlled to have a working pressure of 14 bar, a concentrated water flow rate of 700 L / min, and a produced water flow rate of 2.6 L / min.

2. A near-zero discharge treatment process for wastewater from a chemical park as claimed in claim 1, characterized in that: Ca(OH)2 was used to soften the wastewater from the chemical park. The dosage of Ca(OH)2 was 300 mg / L, and the hardness of the wastewater was reduced to 66 mg / L (measured in CaCO3).

3. A near-zero discharge treatment process for wastewater from a chemical park as claimed in claim 1, characterized in that: The working pressure of the ultrafiltration system is 0.1-0.15MPa, the concentrate flow rate is 1800L / h, and the produced water flow rate is 140L / h.

4. A near-zero discharge treatment process for wastewater in a chemical park as claimed in claim 1, characterized in that: The generated reverse osmosis concentrated water directly enters the catalytic ozone oxidation unit to remove some organic matter.

5. A near-zero discharge treatment process for wastewater in a chemical park as claimed in claim 1, characterized in that: The catalytic ozone oxidation reaction time is 10 min, the ozone concentration is 30 mg / L, the added catalyst is a Fe-Al2O3 supported catalyst, and the addition amount is 100 g / L.

6. A near-zero discharge treatment process for wastewater in a chemical park as claimed in claim 1, characterized in that: The effluent from catalytic ozone oxidation directly enters the biological activated carbon unit. The empty bed residence time of the biological activated carbon unit is 60 minutes. The synergistic effect of activated carbon adsorption and microbial oxidation and decomposition of organic matter is further utilized to remove the organic matter content in the reverse osmosis concentrate, so that the concentrate meets the discharge standards.

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