Treatment system and method for low-COD (Chemical Oxygen Demand) degradation-resistant wastewater

Abstract

The invention provides a treatment system and method for low-COD (Chemical Oxygen Demand) degradation-resistant wastewater. The treatment system comprises a gas-liquid mixing unit, and a raw water supply unit, an ozone supply unit and an ozone oxidation reaction unit which are connected with the gas-liquid mixing unit, the raw water supply unit is used for conveying the low-COD degradation-resistant wastewater to the gas-liquid mixing unit; the ozone supply unit is used for conveying ozone gas to the gas-liquid mixing unit; the gas-liquid mixing unit is configured to perform gas-liquid mass transfer on the low-COD degradation-resistant wastewater and ozone gas to form ozone micro-nano bubble water, and convey the ozone micro-nano bubble water to the ozone oxidation reaction unit; the ozone oxidation reaction unit is configured to enable the ozone micro-nano bubble water to be subjected to ozone oxidation reaction under preset reaction conditions. According to the treatment system and method for the low-COD degradation-resistant wastewater provided by the invention, equipment blockage caused by the fact that the wastewater directly enters the ozone oxidation reaction unit can be avoided, and COD in the wastewater can be stably and efficiently removed.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a system and method for treating low-COD refractory wastewater. Background Art

[0002] The composition of steel wastewater is complex and varied, and its ingredients and properties vary with the composition and properties of the incoming water, as well as the steel rolling process and purification process. Iron and steel joint enterprises usually collect the treated effluent from the entire plant's production wastewater and regional characteristic wastewater (such as coking wastewater and cold rolling wastewater) at the comprehensive wastewater treatment station of the entire plant, and then conduct final treatment on the collected effluent, and make it meet the "Iron and Steel Industry Water Pollutant Discharge Standard" (GB13456-2012, Table 3-Special Limits) or "Surface Water Environmental Quality Standard" (GB3838-2002 Table 1-Surface Water Class V Limits), and COD (Chemical Oxygen Demand) is not higher than 40mg / L before it can be discharged.

[0003] At present, the national and local ecological environment construction planning requirements are gradually tightened, and higher requirements are put forward for the COD index of the effluent after comprehensive wastewater treatment of steel joint enterprises. The COD needs to be lower than 30mg / L, and even in some cases, the COD is required to be lower than 20mg / L. Therefore, in order to further improve the standard, it is urgent to deeply remove the COD of the effluent after the treatment of comprehensive wastewater of steel joint enterprises.

[0004] However, although there are many methods for removing COD from steel wastewater, the technology for further deep removal of COD from low-COD steel comprehensive wastewater after biochemical treatment is still an unsolved problem. The COD removal methods commonly used in the prior art have certain restrictions or defects in terms of use conditions. For example, although electrocatalytic oxidation technology can effectively remove COD, due to its high cost, it is very economical for the treatment of wastewater with large water volume and low COD concentration; the fluidized bed granular activated carbon adsorption method faces the problems of high investment, large floor space and secondary pollution of solid and hazardous waste mainly composed of waste carbon, which limits its widespread application. In contrast, although ozone oxidation is a widely used treatment method in the unit operation of water treatment process, it does not produce secondary pollution and has low investment and operating costs. Advanced oxidation processes are often used for deep treatment of industrial wastewater. However, in the actual application of industrial wastewater treatment, improper ozone addition and catalytic ozone process selection can easily lead to unstable ozone treatment effect. In recent years, the promotion of ozone oxidation technology in the field of wastewater treatment has been limited due to the short half-life and low mass transfer efficiency of traditional aerated ozone, which leads to low oxidation efficiency and high operating costs. Especially when treating wastewater with low COD concentration, the average COD removal effect of aerated ozone is low and unstable. In addition, in the field of industrial wastewater treatment, due to the complex pollution factors and high hardness in wastewater, conventional microporous aeration discs and perforated aeration heads are prone to blockage. Moreover, the traditional positive pressure aeration method easily causes the ozone pipeline to fall off or leak, posing a safety hazard. For example, the effluent of steel comprehensive wastewater after biochemical treatment (referred to as biochemical effluent) has the characteristics of low COD, high chloride ions, high hardness and difficult degradation. If the biochemical effluent is directly sent to the aeration disc ozone contact tank system for treatment, not only is the COD removal effect low (COD removal rate is about 10%), but the removal effect is also unstable. In addition, the aeration plate and the heterogeneous catalyst are easily affected by the high hardness and scaled, which makes the aeration plate easy to be blocked and the heterogeneous catalyst easy to be hardened and deactivated. Summary of the invention

[0005] The object of the present invention is to provide a system and method for treating low-COD difficult-to-degrade wastewater, so as to solve one or more problems existing in the prior art, such as low and unstable average COD removal effect of traditional aerated ozone when treating wastewater with low COD concentration, and easy clogging of conventional microporous aeration plates and perforated aeration heads.

[0006] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions: a treatment system for low-COD difficult-to-degrade wastewater, the treatment system comprising a gas-liquid mixing unit and a raw water supply unit, an ozone supply unit and an ozone oxidation reaction unit connected to the gas-liquid mixing unit; the raw water supply unit is configured to transport the low-COD difficult-to-degrade wastewater to the gas-liquid mixing unit; the ozone supply unit is configured to transport ozone gas to the gas-liquid mixing unit; the gas-liquid mixing unit is configured to: perform gas-liquid mass transfer between the low-COD difficult-to-degrade wastewater and the ozone gas to form ozone micro-nano bubble water, and transport the ozone micro-nano bubble water to the ozone oxidation reaction unit; the ozone oxidation reaction unit is configured to: cause the ozone micro-nano bubble water to undergo an ozone oxidation reaction under preset reaction conditions.

[0007] Optionally, the raw water supply unit includes a raw water tank and a water supply pump which are arranged in sequence, and an output end of the water supply pump is connected to the gas-liquid mixing unit.

[0008] Optionally, the ozone supply unit includes an ozone generator and a chiller connected to the ozone generator, and the gas outlet end of the ozone generator is connected to the gas-liquid mixing unit.

[0009] Optionally, the gas-liquid mixing unit includes a micro-nano bubble generating device and a circulating pump connected to the output end of the micro-nano bubble generating device, and the output end of the circulating pump is connected to the ozone oxidation reaction unit; the liquid inlet end of the micro-nano bubble generating device is connected to the raw water supply unit, and the gas inlet end of the micro-nano bubble generating device is connected to the ozone supply unit.

[0010] Optionally, the liquid inlet end of the micro-nano bubble generating device is also connected to the reflux outlet of the ozone oxidation reaction unit.

[0011] Optionally, the ozone oxidation reaction unit includes an ozone contact tank, a control component, and a water quality monitoring component and a water quality regulating component connected to the ozone contact tank and the control component; a secondary injector is provided in the ozone contact tank, and the secondary injector is connected to the gas-liquid mixing unit; the secondary injector is configured to inject the ozone micro-nano bubble water into the ozone contact tank; the water quality monitoring component is configured to monitor the water quality parameters of the ozone micro-nano bubble water in the ozone contact tank in real time; the control component is configured to: according to the water quality parameters monitored by the water quality monitoring component, control the water quality regulating component to adjust the water quality parameters until the preset reaction conditions are met.

[0012] Optionally, the water quality monitoring component includes a pH meter and an ORP detector, the pH meter is used to monitor the pH value of the ozone micro-nano bubble water in the ozone contact tank in real time, and the ORP detector is used to monitor the ORP value of the ozone micro-nano bubble water in the ozone contact tank in real time; the water quality adjustment component includes an acid-base agent dosing device and a hydrogen peroxide dosing device, the acid-base agent dosing device is used to add acid or alkali to the ozone contact tank, and the hydrogen peroxide dosing device is used to add hydrogen peroxide to the ozone contact tank; the control component is configured to: control the acid-base agent dosing device to adjust the pH value of the ozone micro-nano bubble water to a first preset target range according to the pH value of the ozone micro-nano bubble water monitored by the pH meter; and control the hydrogen peroxide dosing device to adjust the ORP value of the ozone micro-nano bubble water to a second preset target range according to the ORP value of the ozone micro-nano bubble water monitored by the ORP detector.

[0013] Optionally, the first preset target range includes 6 to 8; the second preset target range includes 300 mV to 600 mV.

[0014] Optionally, the control component is connected to the raw water supply unit, the ozone supply unit and the gas-liquid mixing unit; the control component is also configured to: control the dosage of the acid-base agent dosing device, the dosage of the hydrogen peroxide dosing device and the ozone generation amount of the ozone supply unit according to the water supply flow of the raw water supply unit; and when the raw water supply unit starts to supply water, control the ozone supply unit and the gas-liquid mixing unit to start.

[0015] To achieve the above object, the present invention also provides a method for treating low COD refractory wastewater, wherein the low COD refractory wastewater is treated by using any of the above-mentioned low COD refractory wastewater treatment systems, and the treatment method comprises:

[0016] The low-COD refractory wastewater and ozone gas are simultaneously transported to a gas-liquid mixing unit;

[0017] The low-COD refractory wastewater and the ozone gas are subjected to gas-liquid mass transfer to form ozone micro-nano bubble water, and the ozone micro-nano bubble water is transported to an ozone oxidation reaction unit;

[0018] The ozone micro-nano bubble water is subjected to an ozone oxidation reaction under preset reaction conditions.

[0019] Compared with the prior art, the system and method for treating low COD refractory wastewater provided by the present invention have the following beneficial effects:

[0020] The present invention provides a treatment system for low-COD refractory wastewater, the treatment system comprising a gas-liquid mixing unit and a raw water supply unit, an ozone supply unit and an ozone oxidation reaction unit connected to the gas-liquid mixing unit; the raw water supply unit is configured to transport the low-COD refractory wastewater to the gas-liquid mixing unit; the ozone supply unit is configured to transport ozone gas to the gas-liquid mixing unit; the gas-liquid mixing unit is configured to: perform gas-liquid mass transfer between the low-COD refractory wastewater and the ozone gas to form ozone micro-nano bubble water, and transport the ozone micro-nano bubble water to the ozone oxidation reaction unit; the ozone oxidation reaction unit is configured to: cause the ozone micro-nano bubble water to undergo an ozone oxidation reaction under preset reaction conditions. Therefore, the treatment system for low COD difficult-to-degrade wastewater provided by the present invention forms ozone micro-nano bubble water by transferring the low COD difficult-to-degrade wastewater provided by the raw water supply unit and the ozone gas provided by the ozone supply unit through the gas-liquid mixing unit, which not only lays a good foundation for improving the COD removal effect in low COD difficult-to-degrade wastewater, but also can avoid low COD difficult-to-degrade wastewater directly entering the ozone oxidation reaction unit and causing equipment blockage. Furthermore, the ozone oxidation reaction unit is used to make the ozone micro-nano bubble water undergo ozone oxidation reaction under preset reaction conditions, which can stably and efficiently remove COD in low COD difficult-to-degrade wastewater.

[0021] Further, the gas-liquid mixing unit includes a micro-nano bubble generator and a circulation pump connected to the output end of the micro-nano bubble generator, the output end of the circulation pump is connected to the ozone oxidation reaction unit; the liquid inlet end of the micro-nano bubble generator is connected to the raw water supply unit, and the gas inlet end of the micro-nano bubble generator is connected to the ozone supply unit. Thus, the treatment system for low-COD difficult-to-degrade wastewater provided by the present invention can form ozone micro-nano bubble water by gas-liquid mass transfer between the received low-COD difficult-to-degrade wastewater and ozone gas through the micro-nano bubble generator; by connecting the circulation pump to the output end of the micro-nano bubble generator, the ozone micro-nano bubble water can be transported to the ozone oxidation reaction unit, and the size of the ozone bubbles can be further reduced, thereby laying a good foundation for further improving the COD removal effect in low-COD difficult-to-degrade wastewater.

[0022] Since the method for treating low-COD difficult-to-degrade wastewater provided by the present invention and the system for treating low-COD difficult-to-degrade wastewater provided by the present invention belong to the same inventive concept, the method for treating low-COD difficult-to-degrade wastewater provided by the present invention at least has all the advantages of the system for treating low-COD difficult-to-degrade wastewater provided by the present invention. For the advantages of the method for treating low-COD difficult-to-degrade wastewater provided by the present invention, please refer to the relevant description of the beneficial effects of the system for treating low-COD difficult-to-degrade wastewater provided by the present invention, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A structural block diagram of a system for treating low-COD refractory wastewater provided in Example 1 of the present invention;

[0024] Figure 2 A process flow chart of a system for treating low-COD refractory wastewater provided in Example 1 of the present invention;

[0025] Figure 3 A schematic flow chart of a method for treating low-COD refractory wastewater provided in Example 2 of the present invention;

[0026] The following are the descriptions of the reference numerals:

[0027] 1-raw water supply unit, 11-raw water tank, 12-water feed pump, 2-ozone supply unit, 21-ozone generator, 22-chiller, 3-gas-liquid mixing unit, 31-micro-nano bubble generating device, 3101-liquid inlet, 3102-gas inlet, 32-circulation pump, 4-ozone oxidation reaction unit, 41-ozone contact tank, 4101-reflux outlet, 411-secondary ejector, 42-water quality monitoring component, 421-pH meter, 422-ORP detector, 43-control component, 44-water quality adjustment component, 441-acid and alkali agent dosing device, 442-hydrogen peroxide dosing device. DETAILED DESCRIPTION

[0028] The following is a further detailed description of the treatment system and method for low COD refractory wastewater proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Any modification of the structure, change of the proportional relationship or adjustment of the size, in the case of the same or similar effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific environment to be applied and used. And, in the embodiments described below, sometimes the same figure mark is used to represent the same part or part with the same function between different drawings, and its repeated description is omitted.

[0029] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] It should be understood that, unless otherwise stated or obvious from the context, as used herein, the term "about" is understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the value. Unless otherwise clear from the context, all numerical values ​​provided herein are modified by the term "about".

[0031] Embodiment 1

[0032] This embodiment provides a treatment system for low COD refractory wastewater. Figure 1 , Figure 1 The structural block diagram of the treatment system of low COD difficult-to-degrade wastewater provided in this embodiment. Figure 1 It can be seen that the treatment system includes a raw water supply unit 1, an ozone supply unit 2, a gas-liquid mixing unit 3 and an ozone oxidation reaction unit 4, and the raw water supply unit 1, the ozone supply unit 2 and the ozone oxidation reaction unit 4 are all connected to the gas-liquid mixing unit 3; the raw water supply unit 1 is configured to transport the low-COD difficult-to-degrade wastewater to the gas-liquid mixing unit 3; the ozone supply unit 2 is configured to transport ozone gas to the gas-liquid mixing unit 3; the gas-liquid mixing unit 3 is configured to: perform gas-liquid mass transfer between the low-COD difficult-to-degrade wastewater and the ozone gas to form ozone micro-nano bubble water, and transport the ozone micro-nano bubble water to the ozone oxidation reaction unit 4; the ozone oxidation reaction unit 4 is configured to: cause the ozone micro-nano bubble water to undergo ozone oxidation reaction under preset reaction conditions.

[0033] Thus, the treatment system for low COD refractory wastewater provided in this embodiment forms ozone micro-nano bubble water by gas-liquid mass transfer between the low COD refractory wastewater provided by the raw water supply unit 1 and the ozone gas provided by the ozone supply unit 2 through the gas-liquid mixing unit 3, which not only lays a good foundation for improving the COD removal effect in low COD refractory wastewater, but also can avoid low COD refractory wastewater directly entering the ozone oxidation reaction unit 4 and causing equipment blockage. Further, the ozone oxidation reaction unit 4 is used to make the ozone micro-nano bubble water undergo ozone oxidation reaction under preset reaction conditions, so that COD in low COD refractory wastewater can be stably and efficiently removed.

[0034] In addition, ozone oxidation technology has its unique advantages. First, ozone treatment does not introduce other ions or pollutants, and does not require excessive adjustment of the pH of the target water. In addition, due to the strong oxidizing property of ozone, the hydroxyl radicals produced by its indirect oxidation can indiscriminately degrade most pollutants. For wastewater with low COD concentration, ozone treatment has the advantages of low cost and small footprint.

[0035] Statistics show that: compared with the traditional aeration plate treatment, the COD removal rate can be increased to 40% to 60%, the oxygen-carbon ratio is 3.1 to 4.5, and no ozone tail gas is generated by using the low COD refractory wastewater treatment system provided in this embodiment to treat low COD refractory wastewater. It should be noted that the present invention does not make too many restrictions on the specific type of the low COD refractory wastewater, and the low COD refractory wastewater may include but is not limited to the effluent of the steel comprehensive wastewater after biochemical treatment, and the effluent water quality indicators are: COD is about 40mg / L to 50mg / L, TDS (Total dissolved solids) is about 2000mg / L to 4000mg / L, chloride ion concentration is about 800mg / L to 1500mg / L, and total hardness is about 1000mg / L to 2000mg / L.

[0036] Preferably, see Figure 2 , Figure 2 The process flow chart of the treatment system of low COD refractory wastewater provided in this embodiment. Figure 2 It can be seen that the raw water supply unit 1 includes a raw water tank 11 and a water supply pump 12 which are arranged in sequence, and the output end of the water supply pump 12 is connected to the gas-liquid mixing unit 3. Thus, low COD difficult-to-degrade wastewater can be collected through the raw water tank 11; and the low COD difficult-to-degrade wastewater in the raw water tank 11 can be transported to the gas-liquid mixing unit 3 through the water supply pump 12.

[0037] For more information, please see Figure 2 ,from Figure 2It can be seen that the ozone supply unit 2 includes an ozone generator 21 and a chiller 22 connected to the ozone generator 21, and the gas outlet of the ozone generator 21 is connected to the gas-liquid mixing unit 3. Therefore, the ozone generator 21 can be used to discharge high voltage to excite oxygen in the air and form ozone gas; and by connecting the gas outlet of the ozone generator 21 to the gas-liquid mixing unit 3, the ozone gas can be transported to the gas-liquid mixing unit 3. In addition, by connecting the chiller 22 to the ozone generator 21, the ozone generator 21 can be cooled, thereby effectively ensuring that the ozone generator 21 works efficiently.

[0038] For further information, please see Figure 2 ,from Figure 2 It can be seen that the gas-liquid mixing unit 3 includes a micro-nano bubble generator 31 and a circulation pump 32 connected to the output end of the micro-nano bubble generator 31, and the output end of the circulation pump 32 is connected to the ozone oxidation reaction unit 4; the liquid inlet end 3101 of the micro-nano bubble generator 31 is connected to the raw water supply unit 1, and the gas inlet end 3102 of the micro-nano bubble generator 31 is connected to the ozone supply unit 2. Thus, the received low-COD difficult-to-degrade wastewater and ozone gas can be subjected to gas-liquid mass transfer through the micro-nano bubble generator 31 to form ozone micro-nano bubble water; by connecting the circulation pump 32 to the output end of the micro-nano bubble generator 31, the ozone micro-nano bubble water can be transported to the ozone oxidation reaction unit 4, and the size of the ozone bubbles can be further reduced, thereby laying a good foundation for further improving the COD removal effect in the low-COD difficult-to-degrade wastewater.

[0039] Preferably, the liquid inlet end 3101 of the micro-nano bubble generating device 31 is also connected to the reflux outlet 4101 of the ozone oxidation reaction unit 4. Thus, by connecting the reflux outlet 4101 of the ozone oxidation reaction unit 4 to the liquid inlet end 3101 of the micro-nano bubble generating device 31, not only the gas-liquid mass transfer efficiency can be enhanced, but also the wastewater resource utilization can be realized, thereby reducing the system operation cost.

[0040] For further information, please see Figure 2 ,from Figure 2It can be seen that the ozone oxidation reaction unit 4 includes an ozone contact tank 41, a water quality monitoring component 42 connected to the ozone contact tank 41, a control component 43 connected to the water quality monitoring component 42, and a water quality regulating component 44 connected to both the control component 43 and the ozone contact tank 41; a secondary injector 411 is provided in the ozone contact tank 41, and the secondary injector 411 is connected to the gas-liquid mixing unit 3; the secondary injector 411 is configured to inject the ozone micro-nano bubble water into the ozone contact tank 41; the water quality monitoring component 42 is configured to monitor the water quality parameters of the ozone micro-nano bubble water in the ozone contact tank 41 in real time; the control component 43 is configured to: according to the water quality parameters monitored by the water quality monitoring component 42, control the water quality regulating component 44 to adjust the water quality parameters until the preset reaction conditions are met. Thus, the water quality parameters of the ozone micro-nano bubble water in the ozone contact tank 41 can be monitored in real time through the water quality monitoring component 42; the water quality adjustment component 44 can be controlled by the control component 43 to adjust the water quality parameters of the ozone micro-nano bubble water until the preset reaction conditions are met, so that the ozone micro-nano bubble water can undergo ozone oxidation reaction under suitable reaction conditions, thereby improving the COD removal effect in low-COD difficult-to-degrade wastewater.

[0041] For example, please see Figure 2 ,from Figure 2It can be seen that the water quality monitoring component 42 includes a pH meter 421 and an ORP detector 422. The pH meter 421 is used to monitor the pH value of the ozone micro-nano bubble water in the ozone contact tank 41 in real time, and the ORP detector 422 is used to monitor the ORP value of the ozone micro-nano bubble water in the ozone contact tank 41 in real time; the water quality adjustment component 44 includes an acid-base agent dosing device 441 and a hydrogen peroxide dosing device 442. The acid-base agent dosing device 441 is used to add an acid agent or an alkali agent to the ozone contact tank 41. The hydrogen peroxide dosing device 442 is used to add hydrogen peroxide to the ozone contact tank 41; the control component 43 is configured to: control the acid-base agent dosing device 441 to adjust the pH value of the ozone micro-nano bubble water to a first preset target range according to the pH value of the ozone micro-nano bubble water monitored by the pH meter 421; and control the hydrogen peroxide dosing device 442 to adjust the ORP value of the ozone micro-nano bubble water to a second preset target range according to the ORP value of the ozone micro-nano bubble water monitored by the ORP detector 422. Thus, the pH value of the ozone micro-nano bubble water in the ozone contact tank 41 can be monitored in real time by the pH meter 421, and the ORP value of the ozone micro-nano bubble water in the ozone contact tank 41 can be monitored in real time by the ORP detector 422; the control component 43 can control the acid-base agent dosing device 441 to adjust the pH value of the ozone micro-nano bubble water to a first preset target range, and can control the hydrogen peroxide dosing device 442 to adjust the ORP value of the ozone micro-nano bubble water to a second preset target range, so that the ozone oxidation reaction can be carried out efficiently and stably.

[0042] It should be noted that, as can be understood by those skilled in the art, the present invention does not impose too many restrictions on the specific implementation methods of the acid-base agent dosing device 441, the hydrogen peroxide dosing device 442 and the control component 43. For example, the acid-base agent dosing device 441 includes but is not limited to an acid-base agent dosing variable frequency pump, the hydrogen peroxide dosing device 442 includes but is not limited to a hydrogen peroxide dosing variable frequency pump, and the control component 43 includes but is not limited to a PLC controller (Programmable Logic Controller).

[0043] Preferably, the first preset target range includes 6 to 8; the second preset target range includes 300 mV to 600 mV. Thus, by controlling the pH value of the ozone micro-nano bubble water to 6 to 8, the introduction of salt and the cost can be reduced while ensuring the COD removal effect; by controlling the ORP value of the ozone micro-nano bubble water to 300 mV to 600 mV, the consumption of ozone by excessive addition of hydrogen peroxide can be avoided, thereby improving the COD removal effect.

[0044] It should be noted that the present invention does not impose too many restrictions on the connection position between the water quality monitoring component 42 and the ozone contact tank 41. For example, in some exemplary embodiments, the water quality monitoring component 42 is connected to the drain port of the ozone contact tank 41.

[0045] It should be noted that the present invention does not impose too many restrictions on the reaction time set in the ozone oxidation reaction unit 4, and the reaction time of the ozone oxidation reaction unit 4 can be set according to the specific application scenario.

[0046] For example, in some exemplary embodiments, the control component 43 is connected to the raw water supply unit 1, the ozone supply unit 2, and the gas-liquid mixing unit 3; the control component 43 is also configured to: control the dosage of the acid-base agent dosing device 441, the dosage of the hydrogen peroxide dosing device 442, and the amount of ozone generated by the ozone supply unit 2 according to the water supply flow of the raw water supply unit 1; and control the ozone supply unit 2 and the gas-liquid mixing unit 3 to start when the raw water supply unit 1 starts to supply water. Thus, by connecting the control component 43 to the raw water supply unit 1, and connecting the control component 43 to the water quality monitoring component 42 and the water quality regulating component 44, the control component 43 can control the dosage of the acid-base agent dosing device 441 and the dosage of the hydrogen peroxide dosing device 442 according to the water supply flow of the raw water supply unit 1 and the water quality parameters monitored by the water quality monitoring component 42, thereby reducing the operating agent consumption cost and manual operation intervention. Furthermore, by connecting the control component 43 to the ozone supply unit 2 and the gas-liquid mixing unit 3, the amount of ozone generated by the ozone supply unit 2 can be automatically controlled according to the water supply flow of the raw water supply unit 1, and when the raw water supply unit 1 starts to supply water, the ozone supply unit 2 and the gas-liquid mixing unit 3 can be controlled to start, thereby improving the degree of automation of the treatment system and further improving the wastewater treatment efficiency.

[0047] Embodiment 2

[0048] This embodiment provides a method for treating low COD refractory wastewater, using the low COD refractory wastewater treatment system described in any of the above embodiments to treat the low COD refractory wastewater. Figure 3 , Figure 3 The following is a schematic diagram of the process for treating low COD refractory wastewater provided in this embodiment. Figure 3 It can be seen that the processing method includes:

[0049] S100: The low-COD refractory wastewater and ozone gas are simultaneously transported to the gas-liquid mixing unit 3;

[0050] S200: performing gas-liquid mass transfer between the low-COD refractory wastewater and the ozone gas to form ozone micro-nano bubble water, and transporting the ozone micro-nano bubble water to the ozone oxidation reaction unit 4;

[0051] S300: causing the ozone micro-nano bubble water to undergo an ozone oxidation reaction under preset reaction conditions.

[0052] Since the method for treating low-COD difficult-to-degrade wastewater provided in this embodiment and the system for treating low-COD difficult-to-degrade wastewater provided in any of the above-mentioned embodiments belong to the same inventive concept, the method for treating low-COD difficult-to-degrade wastewater provided in this embodiment has at least all the advantages of the systems for treating low-COD difficult-to-degrade wastewater provided in the above-mentioned embodiments. For the advantages of the method for treating low-COD difficult-to-degrade wastewater provided in this embodiment, please refer to the relevant description of the beneficial effects of the systems for treating low-COD difficult-to-degrade wastewater provided in the above-mentioned embodiments, which will not be repeated here.

[0053] In order to make the present invention more easily understood, the method for treating low-COD difficult-to-degrade wastewater provided by the present invention is explained by taking the treated effluent process of a comprehensive wastewater treatment station of a steel joint enterprise with a treatment scale of 25,000 cubic meters per day as an example.

[0054] Originally, the COD concentration of the treated effluent was required to be no higher than 40 mg / L. In order to respond to the latest local environmental protection requirements, it is now required to be raised to a COD concentration of no higher than 20 mg / L. By modifying the original aeration plate ozone contact tank 41 system, a micro-nano bubble generator 31 and a corresponding circulating pump 32 are set on the top of the ozone contact tank 41. The output end of the circulating pump 32 is connected to the secondary ejector 411 in the ozone contact tank 41, the liquid inlet end 3101 of the micro-nano bubble generator 31 is connected to the raw water supply unit 1 that provides the treated effluent, and the ozone generator 21 is connected to the gas inlet end 3102 of the micro-nano bubble generator 31. The ORP detector 422 is interlocked with the hydrogen peroxide dosing frequency conversion pump through the PLC controller to realize the automatic dosing of hydrogen peroxide. The COD of the treated effluent is 31 mg / L to 46 mg / L, and the pH is 6 to 8.

[0055] First, the treated effluent and the ozone gas generated by the ozone generator 21 are simultaneously delivered to the micro-nano bubble generator 31. Then, the treated effluent and the ozone gas are subjected to gas-liquid mass transfer through the micro-nano bubble generator 31 to form ozone micro-nano bubble water, and the ozone micro-nano bubble water is delivered to the ozone contact tank 41 through the circulation pump 32. Finally, the ORP value in the ozone contact tank 41 is automatically controlled to be 400 mV to 600 mV through the PLC controller, and the residence time of the wastewater in the ozone contact tank 41 is set to 3.5 hours.

[0056] After 24 hours of continuous operation for 2 months, the COD removal rate was 51.4% to 71.9%, and the average COD removal rate was 60%; the oxygen-carbon ratio was 3.1 to 4.4, and the average oxygen-carbon ratio was 4.1; the effluent COD was 9 mg / L to 19 mg / L, and the average effluent COD was 15 mg / L, which was lower than 20 mg / L. It can be seen that the treatment method for low-COD refractory wastewater provided by the present invention is used to further treat the effluent after treatment of steel wastewater, which can effectively remove COD in the wastewater and achieve stable compliance.

[0057] In summary, the treatment system and method for low-COD refractory wastewater provided by the present invention have the following advantages: the treatment system for low-COD refractory wastewater provided by the present invention, the treatment system includes a gas-liquid mixing unit and a raw water supply unit, an ozone supply unit and an ozone oxidation reaction unit connected to the gas-liquid mixing unit; the raw water supply unit is configured to transport the low-COD refractory wastewater to the gas-liquid mixing unit; the ozone supply unit is configured to transport ozone gas to the gas-liquid mixing unit; the gas-liquid mixing unit is configured to: perform gas-liquid mass transfer between the low-COD refractory wastewater and the ozone gas to form ozone micro-nano bubble water, and transport the ozone micro-nano bubble water to the ozone oxidation reaction unit; the ozone oxidation reaction unit is configured to: cause the ozone micro-nano bubble water to undergo an ozone oxidation reaction under preset reaction conditions. Therefore, the treatment system for low COD difficult-to-degrade wastewater provided by the present invention forms ozone micro-nano bubble water by transferring the low COD difficult-to-degrade wastewater provided by the raw water supply unit and the ozone gas provided by the ozone supply unit through the gas-liquid mixing unit, which not only lays a good foundation for improving the COD removal effect in low COD difficult-to-degrade wastewater, but also can avoid low COD difficult-to-degrade wastewater directly entering the ozone oxidation reaction unit and causing equipment blockage. Furthermore, the ozone oxidation reaction unit is used to make the ozone micro-nano bubble water undergo ozone oxidation reaction under preset reaction conditions, which can stably and efficiently remove COD in low COD difficult-to-degrade wastewater.

[0058] Further, the gas-liquid mixing unit includes a micro-nano bubble generator and a circulation pump connected to the output end of the micro-nano bubble generator, the output end of the circulation pump is connected to the ozone oxidation reaction unit; the liquid inlet end of the micro-nano bubble generator is connected to the raw water supply unit, and the gas inlet end of the micro-nano bubble generator is connected to the ozone supply unit. Thus, the treatment system for low-COD difficult-to-degrade wastewater provided by the present invention can form ozone micro-nano bubble water by gas-liquid mass transfer between the received low-COD difficult-to-degrade wastewater and ozone gas through the micro-nano bubble generator; by connecting the circulation pump to the output end of the micro-nano bubble generator, the ozone micro-nano bubble water can be transported to the ozone oxidation reaction unit, and the size of the ozone bubbles can be further reduced, thereby laying a good foundation for further improving the COD removal effect in low-COD difficult-to-degrade wastewater.

[0059] Since the method for treating low-COD difficult-to-degrade wastewater provided by the present invention and the system for treating low-COD difficult-to-degrade wastewater provided by the present invention belong to the same inventive concept, the method for treating low-COD difficult-to-degrade wastewater provided by the present invention at least has all the advantages of the system for treating low-COD difficult-to-degrade wastewater provided by the present invention. For the advantages of the method for treating low-COD difficult-to-degrade wastewater provided by the present invention, please refer to the relevant description of the beneficial effects of the system for treating low-COD difficult-to-degrade wastewater provided by the present invention, which will not be repeated here.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A treatment system for low COD refractory wastewater, characterized in that: The treatment system includes a gas-liquid mixing unit and a raw water supply unit, an ozone supply unit and an ozone oxidation reaction unit connected to the gas-liquid mixing unit; The raw water supply unit is configured to transport the low-COD refractory wastewater to the gas-liquid mixing unit; The ozone supply unit is configured to deliver ozone gas to the gas-liquid mixing unit; The gas-liquid mixing unit is configured to: perform gas-liquid mass transfer between the low-COD refractory wastewater and the ozone gas to form ozone micro-nano bubble water, and transport the ozone micro-nano bubble water to the ozone oxidation reaction unit; The ozone oxidation reaction unit is configured to: cause the ozone micro-nano bubble water to undergo an ozone oxidation reaction under preset reaction conditions.

2. The low COD refractory wastewater treatment system according to claim 1, characterized in that: The raw water supply unit includes a raw water tank and a water supply pump which are arranged in sequence, and the output end of the water supply pump is connected to the gas-liquid mixing unit.

3. The low COD refractory wastewater treatment system according to claim 1, characterized in that: The ozone supply unit comprises an ozone generator and a chiller connected to the ozone generator, and the gas outlet end of the ozone generator is connected to the gas-liquid mixing unit.

4. The low COD refractory wastewater treatment system according to claim 1, characterized in that: The gas-liquid mixing unit includes a micro-nano bubble generating device and a circulation pump connected to the output end of the micro-nano bubble generating device, the output end of the circulation pump is connected to the ozone oxidation reaction unit; the liquid inlet end of the micro-nano bubble generating device is connected to the raw water supply unit, and the gas inlet end of the micro-nano bubble generating device is connected to the ozone supply unit.

5. The low COD refractory wastewater treatment system according to claim 4, characterized in that: The liquid inlet end of the micro-nano bubble generating device is also connected to the reflux outlet of the ozone oxidation reaction unit.

6. The low COD refractory wastewater treatment system according to claim 1, characterized in that: The ozone oxidation reaction unit includes an ozone contact tank, a control component, and a water quality monitoring component and a water quality regulating component connected to the ozone contact tank and the control component; The ozone contact tank is provided with a secondary injector, and the secondary injector is connected to the gas-liquid mixing unit; the secondary injector is configured to inject the ozone micro-nano bubble water into the ozone contact tank; The water quality monitoring component is configured to monitor the water quality parameters of the ozone micro-nano bubble water in the ozone contact tank in real time; The control component is configured to: according to the water quality parameters monitored by the water quality monitoring component, control the water quality regulating component to adjust the water quality parameters until the preset reaction conditions are met.

7. The low COD refractory wastewater treatment system according to claim 6, characterized in that: The water quality monitoring component includes a pH meter and an ORP detector, wherein the pH meter is used to monitor the pH value of the ozone micro-nano bubble water in the ozone contact tank in real time, and the ORP detector is used to monitor the ORP value of the ozone micro-nano bubble water in the ozone contact tank in real time; The water quality adjustment component includes an acid and alkali agent dosing device and a hydrogen peroxide dosing device, wherein the acid and alkali agent dosing device is used to add an acid agent or an alkali agent to the ozone contact tank, and the hydrogen peroxide dosing device is used to add hydrogen peroxide to the ozone contact tank; The control component is configured to: control the acid-base agent dosing device to adjust the pH value of the ozone micro-nano bubble water to a first preset target range according to the pH value of the ozone micro-nano bubble water monitored by the pH meter; and control the hydrogen peroxide dosing device to adjust the ORP value of the ozone micro-nano bubble water to a second preset target range according to the ORP value of the ozone micro-nano bubble water monitored by the ORP detector.

8. The low-COD refractory wastewater treatment system according to claim 7, characterized in that: The first preset target range includes 6 to 8; the second preset target range includes 300 millivolts to 600 millivolts.

9. The low COD refractory wastewater treatment system according to claim 7, characterized in that: The control component is connected to the raw water supply unit, the ozone supply unit and the gas-liquid mixing unit; The control component is also configured to: control the dosage of the acid-base agent dosing device, the dosage of the hydrogen peroxide dosing device and the ozone generation amount of the ozone supply unit according to the water supply flow of the raw water supply unit; and when the raw water supply unit starts to supply water, control the ozone supply unit and the gas-liquid mixing unit to start.

10. A method for treating low COD refractory wastewater, characterized in that: The low COD refractory wastewater is treated by using a treatment system for low COD refractory wastewater according to any one of claims 1 to 9, wherein the treatment method comprises: The low-COD refractory wastewater and ozone gas are simultaneously transported to a gas-liquid mixing unit; The low-COD refractory wastewater and the ozone gas are subjected to gas-liquid mass transfer to form ozone micro-nano bubble water, and the ozone micro-nano bubble water is transported to an ozone oxidation reaction unit; The ozone micro-nano bubble water is subjected to an ozone oxidation reaction under preset reaction conditions.

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