Ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater

Abstract

The application relates to the technical field of sewage treatment, in particular to an ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater, which mainly comprises the following steps: removing suspended particles in the wastewater in coagulation and sedimentation, and realizing ozone coupling hydrogen peroxide pre-oxidation treatment of the wastewater in an ozone pre-oxidation contact tank. The pharmaceutical wastewater meeting the pipe standard is subjected to pre-oxidation treatment before biochemical treatment, hydroxyl radicals generated by ozone coupling hydrogen peroxide are used to efficiently remove biotoxicity-containing organic matters in the pharmaceutical wastewater, the wastewater COD is obviously reduced, the secondary biodegradability of the pharmaceutical wastewater is improved, the removal efficiency of pollutants in the subsequent biochemical treatment process is improved, and the carbon source adding amount in the subsequent biochemical treatment is reduced, so that the biochemical treatment can meet the discharge standard without increasing the deep treatment process, thereby reducing the investment, operation cost and effluent exceeding risk of the sewage treatment plant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to an ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater. BACKGROUND

[0002] Generally, the sewage treatment plant in an industrial park is responsible for treating the wastewater discharged by surrounding enterprises, and the enterprises need to transport the wastewater treated to the pipe-in standard to the sewage treatment plant. With the increasing improvement of wastewater treatment and discharge standards in China, more and more sewage treatment plants begin to be reconstructed to meet the standards.

[0003] At present, the treatment process of the wastewater treatment plant in the industrial park mainly learns from the process of the municipal sewage treatment plant, and the treatment process is generally “adjustment tank + coagulation sedimentation + biochemical treatment + advanced treatment”. Since some enterprises have treated the wastewater to the pipe-in standard through biochemical treatment, the proportion of large-molecule organic matter that is difficult to biodegrade in the wastewater is large, and the biodegradability is poor, which increases the difficulty of biochemical treatment in the downstream sewage treatment plant. Especially the wastewater in the pharmaceutical industrial park, some organic matter may contain biological toxicity. After component detection, the main components of this kind of wastewater include ethyl oleate, isobutyl tetrahydrofurfuryl fumarate, squalane and long-chain alkane and other substances.

[0004] In the prior art, in order to meet the increasingly strict discharge standards, the common reconstruction measures of the sewage treatment plant are to increase the advanced treatment measures such as high-level oxidation and double membrane after the biochemical treatment effluent. However, the investment and treatment cost or operation and maintenance of the ozone, Fenton and other high-level oxidation and double membrane process are high, and due to the non-degradability of pollutants, the effect of the advanced treatment is unstable, and the sewage treatment plant faces a high risk of exceeding the standard of effluent. SUMMARY

[0005] The purpose of the present application is to improve the problems of high investment and treatment cost or operation and maintenance and the risk of exceeding the standard of effluent in the prior art, and the present application provides an ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater.

[0006] In a first aspect, the ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater provided by the present application adopts the following technical solution:

[0007] An ozone pre-oxidation treatment process for improving secondary biodegradability of pharmaceutical wastewater, comprising the following steps:

[0008] S1, discharging the wastewater treated to meet the pipe-in standard to the raw water tank, and the COD in the wastewater is less than or equal to 150 mg / L;

[0009] S2. Wastewater from the raw water tank is pumped into the coagulation sedimentation tank. The coagulation sedimentation tank includes a coagulation zone and a sedimentation clarification zone. The pH of the wastewater in the coagulation zone is adjusted to 6-9. Then, coagulant and flocculant are added to the coagulation zone in sequence and stirred thoroughly. Then, the wastewater overflows into the sedimentation clarification zone and settles for 3 hours to remove suspended particulate matter from the wastewater.

[0010] S3. The wastewater treated by the coagulation sedimentation tank is fed into the ozone pre-oxidation contact tank. The ozone pre-oxidation contact tank includes a mixing zone and an ozone contact reaction zone. The wastewater enters through the bottom of the mixing zone and hydrogen peroxide is added to the bottom of the mixing zone. Before being added to the mixing zone, the hydrogen peroxide is mixed with liquid alkali. Then the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone.

[0011] S4. A portion of the wastewater in the mixing zone is drawn into the static mixer by a circulating pump. Ozone is added to the static mixer, and the negative pressure generated by the static mixer is used to mix the ozone into the wastewater. The ozone-containing wastewater enters the ozone contact reaction zone through the release device and is fully mixed with the wastewater in the ozone contact reaction zone, realizing the ozone-coupled hydrogen peroxide pre-oxidation treatment of the wastewater. The wastewater is discharged after the pre-oxidation treatment.

[0012] By adopting the above technical solution, this application treats wastewater by passing it into a coagulation sedimentation tank, which can effectively remove suspended particulate matter from the wastewater and reduce interference during subsequent ozone pre-oxidation treatment. In the ozone pre-oxidation contact tank, the negative pressure generated by the static mixer can mix the wastewater containing hydrogen peroxide with ozone. The ozone coupled with hydrogen peroxide generates a large number of highly oxidizing hydroxyl radicals, which can more effectively decompose the recalcitrant organic matter in pharmaceutical wastewater, such as ethyl oleate, isobutyltetrahydrofurfuryl fumarate, squalane, and long-chain alkanes, and break down large organic molecules into smaller, easily biodegradable substances, while also destroying the biotoxicity of some organic matter. Before adding hydrogen peroxide to the wastewater, it is first mixed with liquid alkali, because hydrogen peroxide is easily decomposed into hydrogen peroxide anion in an alkaline environment, which is an initiator for the generation of hydroxyl radicals and can better promote the production of hydroxyl radicals, thereby improving the efficiency of pre-oxidation treatment. Ozone has low solubility in water (and is easily dispersed). If wastewater containing ozone is directly discharged into the reaction tank, a large amount of ozone will dissipate because it cannot combine with the water in time, resulting in a decrease in ozone utilization. Therefore, wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone, and then wastewater containing ozone is released into the ozone contact reaction zone to form convection with the wastewater in the tank, prolonging the residence time of ozone in the water, reducing dissipation, and improving ozone utilization.

[0013] This application pre-oxidizes pharmaceutical wastewater before it undergoes biological treatment, utilizing hydroxyl radicals generated by ozone coupled with hydrogen peroxide to efficiently remove biotoxic organic matter from the wastewater. This significantly reduces COD, improves the secondary biodegradability of the wastewater, enhances the removal efficiency of subsequent biological treatment processes, and reduces the amount of carbon source required for subsequent biological treatment. Therefore, without adding advanced treatment processes, biological treatment alone can meet discharge standards, thereby reducing the investment, operating costs, and risk of effluent exceeding standards at wastewater treatment plants.

[0014] Preferably, in step S2, the coagulant is PAC with a mass concentration of 10%, an addition amount of 1 ml to 3 ml / L, and a stirring time of 8 to 15 minutes; the flocculant is PAM with a mass concentration of 0.1%, an addition amount of 1 ml / L, and a stirring time of 5 to 10 minutes.

[0015] By adopting the above technical solution, this application first uses PAC for coagulation and stirring, and then uses PAM for flocculation and stirring, which can efficiently remove suspended particulate matter in pharmaceutical wastewater, initially reduce COD, and reduce interference during subsequent ozone pre-oxidation treatment.

[0016] Preferably, in step S4, the amount of ozone added is determined according to the amount of COD to be removed, and the ratio of the amount of ozone added to the amount of COD removed is 0.9-1.5:1.

[0017] Preferably, in step S4, the ozone concentration is 148 mg / L.

[0018] By adopting the above technical solution, the amount of ozone used is matched with the amount of organic matter in the wastewater to be removed (COD of the effluent from the coagulation and clarification tank minus COD of the effluent from the ozone pre-oxidation contact tank). The COD of the effluent from the ozone pre-oxidation contact tank is determined according to the needs of subsequent biochemical treatment. This ratio can ensure that the amount of ozone coupled with the hydroxyl radicals generated by hydrogen peroxide can fully oxidize and decompose the recalcitrant organic matter in the pharmaceutical wastewater, thus avoiding both insufficient ozone leading to incomplete oxidation and excessive ozone causing waste.

[0019] Preferably, in step S3, the mass concentration of hydrogen peroxide is 8%, and the mass ratio of hydrogen peroxide dosage to ozone dosage is 1.2-3:1.

[0020] By adopting the above technical solution and reasonably controlling the mass ratio of hydrogen peroxide to ozone, it is possible to ensure that ozone and hydrogen peroxide react fully, maximize the production efficiency of hydroxyl radicals, and improve the pre-oxidation treatment efficiency. This avoids limiting the ozone oxidation capacity due to insufficient hydrogen peroxide, and also prevents waste or side reactions with free radicals due to excessive amounts.

[0021] Preferably, in step S3, the pH of the liquid alkali is 9.5-10.

[0022] Preferably, the mass ratio of hydrogen peroxide dosage to liquid alkali dosage is 6:1.

[0023] By adopting the above technical solution, liquid alkali can provide a suitable alkaline environment, which promotes the decomposition of hydrogen peroxide into hydrogen peroxide anions, thereby enhancing the synergistic effect of ozone and hydrogen peroxide.

[0024] Preferably, in step S4, the release device is located at the bottom of the ozone contact reaction zone.

[0025] Preferably, in step S3, after the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone and at least covers the release device, the circulation pump is started to extract part of the wastewater in the mixing zone.

[0026] Preferably, in step S3, the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone and is completely filled, and then the circulation pump is started to extract part of the wastewater in the mixing zone.

[0027] By adopting the above technical solution, the release device can disperse ozone-containing wastewater into the wastewater, increasing the contact area between ozone and wastewater. The overflow of wastewater into the ozone contact reaction zone, at least covering the release device, allows the ozone-containing wastewater to form convection currents with the wastewater in the tank. Even better, filling the ozone contact reaction zone before introducing the ozone-containing wastewater maximizes the residence time of ozone in the wastewater and reduces its dissipation. When the circulating pump is started to extract some wastewater from the mixing zone, the wastewater still overflows into the ozone contact reaction zone. The circulating pump primarily powers the static mixer for ozone aeration; therefore, controlling the timing of the circulating pump's start-up is crucial for improving ozone utilization.

[0028] Preferably, in step S4, the wastewater residence time in the ozone contact reaction zone is not less than 45 minutes.

[0029] By adopting the above technical solution, it is possible to ensure that the hydroxyl radicals generated by ozone coupled with hydrogen peroxide fully contact and react with the recalcitrant organic matter in the wastewater, decompose the macromolecular organic matter in the wastewater, and avoid incomplete pre-oxidation treatment of wastewater due to insufficient reaction time.

[0030] Preferably, in step S4, the effluent is subjected to a biological treatment process to achieve Class A discharge standards.

[0031] Preferably, the biological treatment process includes one of the following: activated sludge process, sequencing batch reactor (SBR), anaerobic-aerobic process (A / O), anaerobic-anoxic-aerobic process (A² / O), biofilm process (such as aerated biological filter), and membrane bioreactor.

[0032] By adopting the above technical solution, the biodegradability of wastewater after ozone pre-oxidation treatment is significantly improved. Recalcitrant macromolecular organic matter is decomposed into small, easily biodegradable substances, and some of the biotoxicity is destroyed. After further biochemical treatment, pollutants can be efficiently removed. Therefore, there is no need to add advanced oxidation, dual membrane or other deep treatment measures to make the wastewater meet the Class A discharge standard. This achieves the goal of meeting the discharge standard without adding deep treatment processes, reducing the amount of carbon source added, and lowering the investment, operating costs and risk of effluent exceeding standards of the wastewater treatment plant.

[0033] In summary, this application includes at least one of the following beneficial technical effects:

[0034] (1) This application pre-oxidizes pharmaceutical wastewater that is to be treated to meet the discharge standards before biochemical treatment. It utilizes hydroxyl radicals generated by ozone coupled with hydrogen peroxide to efficiently remove biotoxic organic matter in pharmaceutical wastewater, significantly reduce wastewater COD, improve the secondary biodegradability of pharmaceutical wastewater, improve the removal efficiency of pollutants in subsequent biochemical treatment processes, and reduce the amount of carbon source added in subsequent biochemical treatment. Therefore, without adding advanced treatment processes, biochemical treatment can meet the discharge standards, thereby reducing the investment, operating costs and risk of effluent exceeding standards of wastewater treatment plants.

[0035] (2) The amount of ozone used is matched with the amount of organic matter in the wastewater to be removed (COD of the effluent from the coagulation and clarification tank minus COD of the effluent from the ozone pre-oxidation contact tank). The COD of the effluent from the ozone pre-oxidation contact tank is determined according to the needs of the subsequent biochemical process. This ratio can ensure that the amount of ozone coupled with the hydroxyl radicals generated by hydrogen peroxide can fully oxidize and decompose the recalcitrant organic matter in the pharmaceutical wastewater, thus avoiding incomplete oxidation due to insufficient ozone and preventing waste due to excessive ozone.

[0036] (2) The release device can disperse the ozone-containing wastewater into the wastewater, increasing the contact area between ozone and wastewater; while the wastewater overflows into the ozone contact reaction zone and at least covers the release device, so that the ozone-containing wastewater can form convection with the wastewater in the pool. It is even better to fill the ozone contact reaction zone before introducing the ozone-containing wastewater, which can maximize the residence time of ozone in the wastewater, reduce dispersion, and improve ozone utilization. Attached Figure Description

[0037] Figure 1 This is a schematic flowchart of the ozone pre-oxidation treatment process of this application;

[0038] Explanation of reference numerals in the attached drawings: 1. Hydrogen peroxide dosing device; 2. Liquid alkali dosing device; 3. Static mixer; 4. Release device. Detailed Implementation

[0039] The following is in conjunction with the appendix Figure 1The present application will be further described in detail with reference to the embodiments and comparative examples.

[0040] The wastewater treated in this application is wastewater from a sewage treatment plant in a pharmaceutical industrial park. It has undergone preliminary biological treatment to meet the standards for discharge into the municipal sewer system. The wastewater contains a large amount of recalcitrant organic matter, has poor biodegradability, and some organic matter may contain biotoxic substances. According to the component analysis, the main components of this type of wastewater include ethyl oleate, isobutyltetrahydrofurfuryl fumarate, squalane, and long-chain alkanes. The water quality of the wastewater after preliminary biological treatment is shown in Table 1.

[0041] Table 1 Wastewater Quality

[0042]

[0043] like Figure 1 As shown in the flowchart of the ozone pre-oxidation treatment process of this application, it includes a raw water tank, a coagulation sedimentation tank, and an ozone pre-oxidation contact tank. The coagulation sedimentation tank includes a coagulation zone and a sedimentation clarification zone. The ozone pre-oxidation contact tank includes a mixing zone and an ozone contact reaction zone. The raw water tank is connected to the coagulation zone, and the coagulation zone is connected to the sedimentation tank. Wastewater can overflow from the coagulation zone to the sedimentation tank. The sedimentation tank is connected to the mixing zone, and the mixing zone is connected to the ozone contact reaction zone. Wastewater can overflow from the mixing zone to the ozone contact reaction zone. An outlet is provided at the top of the ozone contact reaction zone, and the outlet can be connected to an external biochemical treatment system. The bottom of the mixing zone is connected to a hydrogen peroxide dosing device 1 and a liquid alkali dosing device 2 via pipes. The liquid alkali dosing device 2 is connected to the pipes of the hydrogen peroxide dosing device 1. Before being added to the mixing zone, the hydrogen peroxide is mixed with the liquid alkali in the pipes. A static mixer 3 is installed at the top of the ozone pre-oxidation contact tank. A circulation pump is installed on the static mixer 3. The static mixer 3 is connected to an ozone generator for providing ozone (O3). The ozone dosing requirement is met by controlling the gas carrying capacity of the circulation pump and the static mixer. The inlet of the static mixer 3 is connected to the mixing zone. The inlet of the static mixer 3 is located above the outlet of the hydrogen peroxide dosing device 1 pipe, ensuring that the wastewater drawn by the static mixer 3 contains hydrogen peroxide. The outlet of the static mixer 3 is connected to a release device 4. The release device 4 is located at the bottom of the ozone contact reaction zone. It can disperse and release the ozone-containing wastewater into the wastewater, increasing the contact area between ozone and wastewater and improving the pre-oxidation efficiency.

[0044] In some specific implementations of ozone pre-oxidation treatment processes, PAC includes one or more of aluminum salts and iron salts;

[0045] In some specific implementations of ozone pre-oxidation treatment processes, aluminum salts include one or more of aluminum sulfate, aluminum chloride, and aluminum nitrate; iron salts include one or more of ferrous chloride and ferrous sulfate.

[0046] In some specific implementations of ozone pre-oxidation treatment processes, the biological treatment process includes one of the following: activated sludge process, sequencing batch reactor (SBR), anaerobic-aerobic process (A / O), anaerobic-anoxic-aerobic process (A² / O), biofilm process (such as aerated biofilter), and membrane bioreactor.

[0047] To avoid unnecessary details, unless otherwise specified, all items used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0048] Example 1

[0049] An ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater includes the following steps:

[0050] S1. A pharmaceutical industrial park discharges wastewater that has been treated to meet the standards for pipe network access into a raw water tank.

[0051] S2. Wastewater from the raw water tank is pumped into the coagulation sedimentation tank. Dilute sulfuric acid or liquid alkali is added to the coagulation zone to adjust the pH of the wastewater to 6-9. 10% PAC coagulant is added at a dosage of 2 ml / L. Coagulation is carried out for 10 minutes. Then, 0.1% PAM is added at a dosage of 1 ml / L. Flocculation is carried out for 8 minutes to remove suspended particulate matter in the wastewater. The wastewater then overflows into the sedimentation tank and settles for 3 hours.

[0052] S3. The wastewater treated by the coagulation sedimentation tank is introduced into the ozone pre-oxidation contact tank. The wastewater enters from the bottom of the mixing zone. Hydrogen peroxide with a mass fraction of 8% and liquid alkali with a pH value of 10 are added to the bottom of the mixing zone respectively. The amount of hydrogen peroxide added is 0.6 ml / L and the amount of liquid alkali added is 0.1 ml / L. Before the hydrogen peroxide is added to the mixing zone, it is mixed with the liquid alkali in the pipeline. Then the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone.

[0053] S4. After the wastewater containing hydrogen peroxide overflows to the cover release device and is above 0.5m, the circulation pump is started to extract part of the wastewater in the mixing zone into the static mixer. Ozone is added to the static mixer through the ozone dosing device at a concentration of 148mg / L and a dosage of 50mg / L. The static mixer generates negative pressure to mix the ozone with the wastewater. The ozone-containing wastewater is released through the release device at the bottom of the ozone contact reaction zone and fully mixed with the wastewater in the ozone contact reaction zone. The residence time of the wastewater in the ozone contact reaction zone is 60 minutes, realizing the ozone-coupled hydrogen peroxide pre-oxidation treatment of the wastewater. The effluent is discharged after the pre-oxidation treatment.

[0054] In this embodiment, the ozone dosage of 150 mg / L is the dosage in the ozone contact reaction zone, the ratio of ozone dosage to COD to be removed is approximately 0.9:1, and the ratio of hydrogen peroxide dosage to ozone dosage is 1.2:1.

[0055] In this embodiment, in step S4, the effluent after pre-oxidation treatment is then subjected to a biochemical treatment process, and the wastewater after biochemical treatment meets the Class A discharge standard of GB 18918-2002.

[0056] Example 2

[0057] The difference from Example 1 is that in step S3, the amount of hydrogen peroxide added is 1.05 ml / L, the amount of liquid alkali added is 0.175 ml / L, and the mass ratio of hydrogen peroxide added to ozone added is 2.1:1. The rest is the same as in Example 1.

[0058] Example 3

[0059] The difference from Example 1 is that in step S3, the amount of hydrogen peroxide added is 1.5 ml / L, the amount of liquid alkali added is 0.25 ml / L, and the mass ratio of hydrogen peroxide added to ozone added is 3:1. The rest is the same as in Example 1.

[0060] Example 4

[0061] The difference from Example 1 is that in step S4, the ozone dosage is 67 ml / L, the ratio of ozone dosage to COD is approximately 1.2:1, the hydrogen peroxide dosage is 0.8 ml / L, and the alkali dosage is 0.13 ml / L. The rest are the same as in Example 1.

[0062] Example 5

[0063] The difference from Example 1 is that in step S4, the ozone dosage is 83 ml / L, the ratio of ozone dosage to COD is approximately 1.5:1, the hydrogen peroxide dosage is 1.0 ml / L, and the alkali solution dosage is 0.16 ml / L. The rest are the same as in Example 1.

[0064] Example 6

[0065] The difference from Example 1 is that in step S4, the wastewater residence time in the ozone contact reaction zone is 45 minutes, while the rest is the same as in Example 1.

[0066] Example 7

[0067] The difference from Example 1 is that in step S4, the wastewater residence time in the ozone contact reaction zone is 75 minutes, while the rest is the same as in Example 1.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that in step S3, only hydrogen peroxide is added to the mixing zone, and no liquid alkali is added; otherwise, it is the same as Example 1.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that in step S3, hydrogen peroxide and liquid alkali are not added to the mixing zone, while the rest is the same as in Example 1.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that in step S3, the wastewater containing hydrogen peroxide does not overflow into the ozone contact reaction zone. That is, all the wastewater in the mixing zone is pumped into the ozone contact reaction zone through a circulation pump. The rest is the same as in Example 1.

[0074] Performance testing

[0075] The wastewater from each stage of the above embodiments and comparative examples was subjected to relevant tests, and the test results are shown in Table 2. The relevant tests included measuring COB and BOD in the effluent from the coagulation sedimentation tank and the ozone contact reaction zone, and calculating the BOD to COD ratio.

[0076] Table 2 Test Results

[0077]

[0078] Referring to Table 2, although the wastewater and treatment process are the same in the coagulation sedimentation tanks of the examples and comparative examples, the coagulation sedimentation operation is carried out separately in each case. The same coagulation sedimentation tank effluent is not used uniformly. Moreover, COD and BOD detection are affected by the environment and there is a certain detection error. Therefore, the detection results of the coagulation sedimentation tank effluent of the examples and comparative examples have a certain error, but the error value is within ±5%, which is an acceptable error and does not affect the judgment of the treatment effect of this application.

[0079] As shown in Table 2, the ozone pre-oxidation treatment process in Examples 1-7 of this application can improve the biochemical performance of pharmaceutical wastewater. Compared with the effluent from the coagulation sedimentation tank, the COD removal rate of the wastewater can reach 45%, and the biodegradability is improved by 190%. This indicates that the hydroxyl radicals generated by ozone coupled with hydrogen peroxide can efficiently remove biotoxic organic matter in pharmaceutical wastewater, significantly reduce the COD of the wastewater, improve the biodegradability of pharmaceutical wastewater, and increase the removal efficiency of pollutants in subsequent biochemical treatment processes, thereby reducing the amount of carbon source added in subsequent biochemical treatment.

[0080] The difference between Examples 1-3 lies in the amount of hydrogen peroxide added. The ratio of hydrogen peroxide to ozone is 1.2-3:1, which ensures that ozone can couple with sufficient hydrogen peroxide to maximize the production efficiency of ozone hydroxyl radicals.

[0081] The difference between Example 1 and Examples 4-5 lies in the amount of ozone added. The amount of ozone added is matched to the amount of organic matter in the wastewater to be removed (COD of the coagulation and clarification tank effluent minus COD of the ozone pre-oxidation contact tank effluent). The COD of the ozone pre-oxidation contact tank effluent is determined by the requirements of subsequent biological treatment processes. Therefore, as shown in Table 2, as the amount of ozone added increases, the improvement in COD removal rate and B / C ratio also decreases. Therefore, controlling the ratio of ozone addition to COD removal to 0.9-1.5 results in better ozone pre-oxidation treatment effect, and the treated wastewater can meet the standards of subsequent biological treatment.

[0082] The difference between Example 1 and Examples 6-7 lies in the wastewater retention time in the ozone contact reaction zone. It can be seen that the wastewater retention time in the ozone pre-oxidation stage should be no less than 45 minutes to ensure the ozone pre-oxidation treatment effect. As the wastewater retention time increases, most of the oxidizable organic matter in the water has already decomposed; further extending the time will significantly slow the increase in COD removal rate and B / C ratio. Therefore, controlling the wastewater retention time in the ozone contact reaction zone to within 75 minutes can achieve a good ozone pre-oxidation treatment effect. The preferred example is Example 1, with a retention time of 60 minutes.

[0083] The difference between Example 1 and Comparative Example 1 lies in the addition of liquid alkali. Comparative Example 1 did not add liquid alkali, and its COD removal rate and biodegradability were significantly affected. Hydrogen peroxide is difficult to decompose into hydrogen peroxide anions in a neutral or weakly acidic environment. Ozone lacks sufficient initiator and cannot efficiently generate hydroxyl radicals, thus affecting the efficiency of ozone pre-oxidation treatment.

[0084] The difference between Example 1 and Comparative Example 2 lies in the addition of hydrogen peroxide and liquid alkali. It can be seen that Comparative Example 2 only adds hydrogen peroxide and liquid alkali. Since ozone itself has a weak oxidizing ability, when ozone acts alone, it can only decompose some easily oxidized organic matter, and its ability to break down large molecules and difficult-to-degrade components is obviously insufficient.

[0085] The difference between Example 1 and Comparative Example 3 is that in Comparative Example 3, the wastewater containing hydrogen peroxide does not overflow into the ozone contact reaction zone, and the wastewater that is introduced into the ozone is directly released into the ozone contact reaction tank by the release device. The ozone lacks sufficient wastewater buffer and dissipates rapidly. Although the impact decreases as the amount of wastewater in the ozone contact reaction zone increases, the overall utilization rate of ozone decreases and the pre-oxidation treatment efficiency also decreases.

[0086] In Examples 1-7, the secondary biodegradability of the effluent from the ozone pre-oxidation contact tank is significantly improved. With the addition of an external biological treatment process, it can meet the Class A discharge standard, thus eliminating the need for advanced oxidation, dual-membrane, or other deep treatment measures at the downstream end. Compared to existing technologies, the cost of the ozone pre-oxidation treatment process in this application is significantly lower than conventional deep treatment processes. Furthermore, this application demonstrates stable treatment effects on high concentrations of recalcitrant organic matter, reducing the investment and operating costs of wastewater treatment plants and the risk of effluent exceeding standards.

[0087] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. An ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater, characterized in that, Includes the following steps: S1. Discharge the treated wastewater that meets the standards for pipe network access to the raw water tank. The COD in the wastewater is less than or equal to 150 mg / L. S2. The wastewater in the raw water tank is pumped into the coagulation sedimentation tank. The coagulation sedimentation tank includes a coagulation zone and a sedimentation clarification zone. The pH of the wastewater in the coagulation zone is adjusted to 6-9. Then, coagulant and flocculant are added to the coagulation zone in sequence and stirred thoroughly. Then, the wastewater overflows into the sedimentation clarification zone and settles for 3 hours to remove suspended particulate matter from the wastewater. S3. The wastewater treated by the coagulation sedimentation tank is fed into the ozone pre-oxidation contact tank. The ozone pre-oxidation contact tank includes a mixing zone and an ozone contact reaction zone. The wastewater enters through the bottom of the mixing zone. Hydrogen peroxide is added to the bottom of the mixing zone. Before being added to the mixing zone, the hydrogen peroxide is mixed with liquid alkali. Then the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone. S4. A portion of the wastewater in the mixing zone is drawn into a static mixer by a circulating pump. Ozone is added to the static mixer, and the negative pressure generated by the static mixer is used to mix the ozone into the wastewater. The ozone-containing wastewater enters the ozone contact reaction zone through a release device and is fully mixed with the wastewater in the ozone contact reaction zone to achieve ozone-coupled hydrogen peroxide pre-oxidation treatment of the wastewater. The wastewater is then discharged after pre-oxidation treatment. In step S4, the release device is located at the bottom of the ozone contact reaction zone; In step S3, after the wastewater containing hydrogen peroxide overflows into the ozone contact reaction zone and at least covers the release device, the circulation pump is then started to extract part of the wastewater in the mixing zone.

2. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 1, characterized in that, In step S2, the coagulant is PAC with a mass concentration of 10%, an addition amount of 1 ml to 3 ml / L, and a stirring time of 8 to 15 minutes; the flocculant is PAM with a mass concentration of 0.1%, an addition amount of 1 ml / L, and a stirring time of 5 to 10 minutes.

3. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 1, characterized in that, In step S4, the amount of ozone added is determined according to the amount of COD to be removed, the ratio of ozone added to COD removed is 0.9-1.5:1, and the ozone concentration is 148 mg / L.

4. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 3, characterized in that, In step S3, the mass concentration of hydrogen peroxide is 8%; the mass ratio of hydrogen peroxide dosage to ozone dosage is 1.2-3:

1.

5. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 4, characterized in that, In step S3, the pH of the liquid alkali is 9.5-10.

6. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 1, characterized in that, In step S4, the wastewater in the ozone contact reaction zone shall remain for no less than 45 minutes.

7. The ozone pre-oxidation treatment process for improving the secondary biodegradability of pharmaceutical wastewater according to claim 1, characterized in that, In step S4, the effluent is subjected to a biochemical treatment process to achieve Class A discharge standards.

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