Advanced treatment system for petrochemical high-salinity wastewater

Abstract

The invention relates to an advanced treatment system for petrochemical high-salinity wastewater, and belongs to the technical field of sewage treatment.The advanced treatment system comprises an ozone oxidation reaction tank, a denitrification deep-bed filter tank and an ultrafiltration-reverse osmosis treatment system.The ozone oxidation reaction tank is used for treating refractory organics in petrochemical wastewater and enhancing biodegradability of the wastewater; the denitrification deep-bed filter adopts an up-flow structure, salt-tolerant denitrifying bacteria are inoculated to start and domesticate the denitrification deep-bed filter, a heterotrophic denitrification deep-bed filter can be adopted, a sulfur autotrophic denitrification deep-bed filter can also be adopted, and an ultrafiltration-reverse osmosis treatment system is mainly used for treating soluble solids, so that the regeneration and reuse of petrochemical wastewater are facilitated; the problems that organic matters in the high-salinity wastewater are difficult to degrade and the denitrification efficiency is low are solved through coupling of ozone oxidation and denitrification processes, the method has the advantages of low operation cost, low sludge yield, high salinity impact resistance and the like, and the wastewater mainly treated by the ultrafiltration-reverse osmosis treatment system can be recycled.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment and reuse, and particularly relates to a deep treatment system for petrochemical high-salt wastewater. Background Art

[0002] The petrochemical industry generates a large amount of high-salt wastewater during the production process, and it contains high concentrations of nitrate nitrogen and refractory organic compounds such as benzene series, phenols, polycyclic aromatic hydrocarbons, etc. After the petrochemical wastewater is treated by secondary biological treatment, the COD and total nitrogen in the wastewater are difficult to meet the effluent quality requirements, and usually need to be deeply treated to ensure that the effluent meets the discharge standards.

[0003] Usually, advanced oxidation treatment processes are used to treat refractory organic compounds, and COD up-to-standard discharge can be achieved. However, it is difficult to remove nitrate nitrogen only relying on advanced oxidation treatment processes, and it is difficult to achieve up-to-standard discharge of the total nitrogen in the effluent. Therefore, a deep denitrification process usually needs to be combined.

[0004] Traditional deep denitrification processes mainly adopt heterotrophic denitrification, which requires adding organic carbon sources (such as methanol, sodium acetate, etc.) as electron donors. The denitrification performance is stable, and the total nitrogen in the effluent can meet the effluent requirements after heterotrophic denitrification. In addition, autotrophic denitrification technology is also commonly used for deep denitrification, especially the sulfur autotrophic denitrification process, which uses sulfide (S 2- ) or elemental sulfur (S 0 ) as electron donors to reduce nitrate nitrogen to nitrogen gas (N2). This process does not require external carbon sources, has less sludge production, and low operating costs.

[0005] However, there are still some refractory organic compounds in the petrochemical wastewater after advanced oxidation treatment, which will inhibit the activity of denitrifying bacteria, resulting in low denitrification efficiency. In addition, advanced oxidation technology is difficult to remove the salinity in petrochemical wastewater, and high-salt wastewater easily causes the activity of denitrifying bacteria to decline, affecting the nitrogen removal performance. Based on this, how to develop a deep treatment process that meets the discharge standards of petrochemical wastewater is of great significance for achieving the discharge standards of petrochemical wastewater and the reuse of reclaimed water. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention proposes a deep treatment system for petrochemical high-salt wastewater, which realizes the deep treatment and regeneration reuse of refractory organic compounds and high-salt wastewater in petrochemical wastewater.

[0007] The present invention adopts the following technical solutions to solve the above problems:

[0008] A deep treatment system for petrochemical high-salt wastewater, comprising an ozone catalytic oxidation unit, a denitrification deep bed filter, and an ultrafiltration-reverse osmosis treatment system. The outlet of the ozone catalytic oxidation unit is connected to the bottom of the denitrification deep bed filter. The steps for deep treatment of wastewater using this system are as follows:

[0009] S1: After secondary biochemical treatment of the wastewater, it enters the ozone catalytic oxidation unit to remove refractory organic matter.

[0010] S2: The wastewater treated in step S1 enters the denitrification deep bed filter to remove nitrate nitrogen.

[0011] S3: The wastewater after step S2 enters the ultrafiltration-reverse osmosis treatment unit to remove dissolved solids.

[0012] Further, in S1, the ozone catalytic oxidation unit adopts an activated carbon ozone catalytic oxidation process, including an air compressor and an ozone generator.

[0013] Further, in S1, the process of treating wastewater is as follows: The wastewater enters from the lower part of the ozone oxidation reactor, the ozone gas is introduced from the bottom of the reactor, the ozone gas is evenly mixed with water through the gas distribution plate in the reactor, and the water and ozone gas flow upward through the activated carbon layer filled in the reactor for 20 minutes of reaction.

[0014] Further, in S2, the denitrification deep bed filter adopts a heterotrophic denitrification deep bed filter process. Ceramsite is filled in the filter as the filter material, sodium acetate is used as the carbon source, and an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

[0015] Further, in S2, the denitrification deep bed filter adopts a sulfur autotrophic denitrification deep bed filter process. Iron sulfide particles are filled in the filter as the filter material, and the iron content of the iron sulfide particles is 5%. At the same time, an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

[0016] Further, salt-tolerant denitrifying bacteria (at the genus level) are inoculated in the deep bed filter to start and domesticate the denitrification deep bed filter. The types are mainly Thiobacillus and Thauera. The bacteria are evenly inoculated into the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted by means of circulating flow.

[0017] Further, the ultrafiltration-reverse osmosis treatment system includes an ultrafiltration membrane system and an RO reverse osmosis membrane system. The ultrafiltration membrane system adopts a ceramic membrane filtration device, and the RO reverse osmosis membrane system is used to remove dissolved solid impurities to achieve the recycling and reuse of wastewater.

[0018] Advantages of the present invention:

[0019] 1. The present invention adopts the ozone oxidation coupled with denitrification deep bed filter process, which can effectively treat petrochemical high-salt wastewater and achieve the dual goals of organic matter degradation and nitrogen removal.

[0020] 2. Ozone oxidation can improve the biodegradability of wastewater and provide favorable conditions for subsequent deep denitrification. The denitrification deep bed filter can choose either heterotrophic denitrification or autotrophic denitrification. The system has a simple structure, convenient operation and stable operation, and is suitable for the advanced treatment of petrochemical high-salt wastewater.

[0021] 3. The ultrafiltration-reverse osmosis device can realize the regeneration and reuse of wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] With reference to the accompanying drawings, the exemplary embodiments of the present invention will be described in more detail, making the above-mentioned objects, features and advantages of the present invention more obvious. In the exemplary embodiments of the present invention, the same reference numerals generally denote the same components.

[0023] Figure 1 It is a schematic diagram of the connection structure of this system;

[0024] Figure 2 It is a schematic diagram of the influent and effluent water quality of the ozone oxidation coupled with heterotrophic denitrification deep bed filter process for treating petrochemical saline wastewater in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following describes the specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are within the spirit and scope of the present invention defined and determined by the appended claims, and these changes are obvious. All inventions created using the concept of the present invention are within the scope of protection.

[0026] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0027] Such as Figure 1As shown in the figure, the system includes an ozone catalytic oxidation unit, a denitrifying deep bed filter, and an ultrafiltration-reverse osmosis treatment system. The outlet of the ozone catalytic oxidation unit is connected to the bottom of the denitrifying deep bed filter. Salt-tolerant denitrifying bacteria (genus level) are inoculated in the deep bed filter to start and domesticate the denitrifying deep bed filter. The main types are Thiobacillus and Thauera. The bacteria are evenly inoculated in the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted through the way of circulating flow. The steps for advanced treatment of the system wastewater are as follows:

[0028] S1: After the wastewater is treated by secondary biochemical treatment, it enters the ozone catalytic oxidation unit to remove refractory organic matters.

[0029] The ozone catalytic oxidation unit adopts the activated carbon ozone catalytic oxidation process, including an air compressor and an ozone generator. The process of treating wastewater is as follows: The wastewater enters from the lower part of the ozone oxidation reactor, and ozone gas is introduced from the bottom of the reactor. The ozone gas is evenly mixed with water through the air distribution plate in the reactor. The water and ozone gas flow upward through the activated carbon layer filled in the reactor and react for 20 minutes.

[0030] S2: The wastewater treated in step S1 enters the denitrifying deep bed filter to remove nitrate nitrogen.

[0031] The denitrifying deep bed filter can adopt the heterotrophic denitrifying deep bed filter process. Ceramsite is filled in the filter as the filter material, and sodium acetate is used as the carbon source. At the same time, an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

[0032] The denitrifying deep bed filter can also adopt the sulfur autotrophic denitrifying deep bed filter process. Iron sulfide particles are filled in the filter as the filter material, and the iron content of the iron sulfide particles is 5%. At the same time, an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

[0033] S3: The wastewater after step S2 enters the ultrafiltration-reverse osmosis treatment unit to remove dissolved solids.

[0034] The ultrafiltration-reverse osmosis treatment system includes an ultrafiltration membrane system and an RO reverse osmosis membrane system. The ultrafiltration membrane system adopts a ceramic membrane filtration device, and the RO reverse osmosis membrane system is used to remove dissolved solid impurities to realize the recycling of the wastewater.

[0035] The process flow of the present invention is as follows: After the wastewater is treated by secondary biochemical treatment, it enters the ozone catalytic oxidation system to remove refractory organic matters, then enters the deep bed filter system to remove nitrate nitrogen, and finally enters the ultrafiltration-reverse osmosis treatment unit to remove dissolved solids. The above steps are described in detail below in combination with embodiments:

[0036] Example 1

[0037] The high-salt wastewater treatment project of a petrochemical enterprise adopts the ozone oxidation coupled with heterotrophic denitrification deep bed filter process. The influent is the wastewater after secondary treatment, with the water quality characteristics of high salinity (chloride 3000 - 4000 mg / L) and containing a certain amount of refractory organic matter, mainly trace oil and benzene series (TOC concentration is 60 - 80 mg / L).

[0038] For the wastewater after secondary treatment, the TOC value is 30 - 50 mg / L, the COD value is 65 - 90 mg / L, and the TN value is 25 - 30 mg / L. After ozone catalytic oxidation treatment, the effluent TOC value is 20 - 35 mg / L, the COD value is 50 - 55 mg / L, and the TN value is 25 - 30 mg / L.

[0039] After the wastewater is treated by ozone catalytic oxidation, it enters the heterotrophic denitrification deep bed filter for advanced nitrogen removal.

[0040] The heterotrophic denitrification deep bed filter uses ceramsite as the filter material and lays pebbles at the bottom as the support layer.

[0041] Pressure sensors are set at the inlet and outlet of the heterotrophic denitrification deep bed filter. When the monitored pressure difference exceeds 0.02 Mpa, air-water backwashing is carried out.

[0042] After being treated by the heterotrophic denitrification deep bed filter, the effluent TOC is 10 - 15 mg / L, the COD value is 30 - 40 mg / L, and the TN is less than 18 mg / L.

[0043] The influent and effluent water quality of the ozone oxidation coupled with heterotrophic denitrification deep bed filter process for treating petrochemical saline wastewater is as Figure 1 shown.

[0044] After the petrochemical wastewater is deeply treated by the ozone oxidation coupled with heterotrophic denitrification deep bed filter process, the effluent meets the first-class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918 - 2002), that is, the COD is less than 60 mg / L and the total nitrogen in the effluent is less than 20 mg / L.

[0045] Subsequently, for the petrochemical wastewater treated by the ultrafiltration - reverse osmosis device, the COD is less than 20 mg / L, the TDS is less than 500 mg / L, and the chloride ion concentration is less than 50 mg / L.

[0046] Example 2

[0047] The high-salt wastewater treatment project of a petrochemical enterprise adopts the ozone oxidation coupled with sulfur autotrophic denitrification deep bed filter process. The influent is the wastewater after secondary treatment, with the water quality characteristics of high salinity (chloride 3000 - 4000 mg / L) and containing a certain amount of refractory organic matter, mainly trace oil and benzene series (≤10 mg / L, TOC concentration is 40 - 50 mg / L).

[0048] The wastewater after secondary treatment has a TOC value of 25 - 55 mg / L, a COD value of 60 - 95 mg / L, and a TN value of 25 - 30 mg / L. After ozone catalytic oxidation treatment, the effluent has a TOC value of 15 - 40 mg / L, a COD value of 50 - 55 mg / L, and a TN value of 25 - 30 mg / L.

[0049] After the wastewater is treated by ozone catalytic oxidation, it enters a sulfur autotrophic denitrification deep bed filter for advanced nitrogen removal.

[0050] The sulfur autotrophic denitrification deep bed filter uses sulfur-iron particles as filter media and lays pebbles at the bottom as a support layer.

[0051] The sulfur autotrophic denitrification deep bed filter is equipped with pressure sensors at the inlet and outlet. When the monitored pressure difference exceeds 0.02 Mpa, air-water backwashing is carried out.

[0052] After being treated by the sulfur autotrophic denitrification deep bed filter, the effluent has a TN lower than 15 mg / L and a COD lower than 40 mg / L.

[0053] The petrochemical wastewater after advanced treatment by the ozone oxidation coupled with sulfur autotrophic denitrification deep bed filter process meets the first-class B standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918 - 2002), that is, the COD is lower than 60 mg / L and the total nitrogen in the effluent is lower than 20 mg / L. In some cases, the effluent can reach the first-class A standard, that is, the COD is lower than 50 mg / L and the total nitrogen in the effluent is lower than 15 mg / L.

[0054] Subsequently, the petrochemical wastewater treated by the ultrafiltration - reverse osmosis device has a COD lower than 15 mg / L, a TDS lower than 400 mg / L, and a chloride ion concentration lower than 60 mg / L. This water quality can be used for greening irrigation in the plant area.

[0055] The above has described the present invention in detail through examples, but the content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the patent coverage scope of the present invention.

Claims

1. A deep treatment system for petrochemical high-salt wastewater, characterized in that: It includes an ozone catalytic oxidation unit, a denitrifying deep bed filter, and an ultrafiltration-reverse osmosis treatment system. The outlet of the ozone catalytic oxidation unit is connected to the bottom of the denitrifying deep bed filter. The steps for advanced wastewater treatment using this system are as follows: S1: After secondary biochemical treatment, the wastewater enters the ozone catalytic oxidation unit to remove refractory organic compounds. S2: The wastewater treated in step S1 enters the denitrifying deep bed filter to remove nitrate nitrogen. S3: The wastewater after step S2 enters the ultrafiltration-reverse osmosis treatment unit to remove dissolved solids.

2. The deep treatment system for petrochemical high-salt wastewater according to claim 1, characterized in that: In S1, the ozone catalytic oxidation unit adopts an activated carbon ozone catalytic oxidation process, including an air compressor and an ozone generator.

3. The deep treatment system for petrochemical high-salt wastewater according to claim 2, wherein: In S1, the process of treating wastewater is as follows: The wastewater enters from the lower part of the ozone oxidation reactor, and the ozone gas is introduced from the bottom of the reactor. The ozone gas is evenly mixed with water through the air distribution plate in the reactor. The water and ozone gas flow upward through the activated carbon layer filled in the reactor and react for 20 minutes.

4. The deep treatment system for petrochemical high-salt wastewater according to claim 1, wherein: In S2, the denitrifying deep bed filter adopts a heterotrophic denitrifying deep bed filter process. Ceramsite is filled in the filter as the filter material, and sodium acetate is used as the carbon source. At the same time, an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

5. The deep treatment system for petrochemical high-salt wastewater according to claim 1, wherein: In S2, the denitrifying deep bed filter adopts a sulfur autotrophic denitrifying deep bed filter process. Sulfur iron particles are filled in the filter as the filter material, and the iron content of the sulfur iron particles is 5%. At the same time, an acid-base adjustment device is equipped for the influent to ensure that the influent pH is 7-8.

6. The deep treatment system for petrochemical high-salt wastewater according to claim 4 or 5, characterized in that: In the deep bed filter, salt-tolerant denitrifying bacteria (genus level) are inoculated to start and domesticate the denitrifying deep bed filter. The main types are Thiobacillus and Thauera. The bacteria are evenly inoculated into the deep bed filter in the form of suspended bacteria, and their attachment and reproduction are promoted through the way of circulating flow.

7. A deep treatment system for petrochemical high-salt wastewater according to claim 1, characterized in that: The ultrafiltration-reverse osmosis treatment system includes an ultrafiltration membrane system and an RO reverse osmosis membrane system. The ultrafiltration membrane system adopts a ceramic membrane filtration device. The RO reverse osmosis membrane system is used to remove dissolved solid impurities and realize the regeneration and reuse of wastewater.

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