Fluorescent wastewater treatment process
By introducing an acidification and activation tank and a Fenton main reaction tank into the fluorescent wastewater treatment process, and utilizing the reflux and redissolution of iron sludge, the problems of high ferrous sulfate consumption and iron sludge treatment costs in the Fenton process are solved, thus realizing resource recycling and cost reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-03-27
AI Technical Summary
In existing fluorescent wastewater treatment processes, the Fenton method requires continuous addition of hydrogen peroxide and ferrous sulfate, resulting in high consumption and costs. Furthermore, the iron sludge produced requires treatment, and repeated acid-base adjustments waste resources and increase costs.
The process combines primary pretreatment, acidification activation tank and Fenton main reaction tank. By refluxing the iron sludge under acidic conditions, it is redissolved into Fe³⁺/Fe²⁺ ions to participate in the catalytic reaction, reducing the amount of ferrous sulfate used. Iron sludge is also recovered during the neutralization process, thus reducing the cost of iron sludge treatment.
The amount of ferrous sulfate used was reduced, which lowered the processing cost, reduced the amount of iron sludge to be treated, improved the oxidation efficiency, simplified the acid-base adjustment steps, and reduced the overall process cost.
Smart Images
Figure CN121735478A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment technology, specifically a fluorescent wastewater treatment process. Background Technology
[0002] In the production of some high-precision equipment and components, fluorescent testing is often required after production to ensure the service life or production accuracy of the components or equipment. Fluorescent testing typically involves first treating the surface of the component, then applying a fluorescent penetrant, followed by a developer to form a thin film. Capillary action is used to adsorb the fluorescent liquid from defects onto the surface, where it diffuses and amplifies. Then, in a dark room, ultraviolet light is used to irradiate the defect, causing it to emit a bright yellow-green fluorescence. This allows for the identification of damaged areas that are difficult to detect with the naked eye. However, this process often generates a large amount of fluorescent wastewater. Direct discharge of this wastewater would impact water resources, so pretreatment is often necessary to bring it up to the required discharge standards before release. This process involves fluorescent wastewater treatment technology.
[0003] However, existing technologies still have significant shortcomings, such as:
[0004] The core step in treating fluorescent wastewater is the oxidation degradation step, commonly using the Fenton process. This requires the continuous addition of hydrogen peroxide and ferrous sulfate. Ferrous sulfate consumption is high, leading to excessive costs. The treated water after oxidation then enters the subsequent biological system. The Fenton reaction requires a strongly acidic environment, and the effluent must be adjusted to neutral before entering the biological system. This repeated adjustment of the strongly acidic and neutral environments necessitates the repeated addition of acidic and alkaline substances, which is wasteful and increases the overall cost of the process. Furthermore, the entire process generates a large amount of iron sludge, Fe(OH)3, which requires treatment and also incurs significant costs. Summary of the Invention
[0005] The purpose of this invention is to provide a fluorescent wastewater treatment process to solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A fluorescent wastewater treatment process includes the following steps:
[0008] S1: Primary pretreatment: Wastewater first passes through a screen to remove large floating and suspended solids, and then enters an equalization tank to adjust the water quality and quantity.
[0009] S2: Secondary pretreatment: The effluent from the equalization tank is pumped to the coagulation reaction tank using a metering pump. A 10% concentration of polyaluminum chloride solution is added to the pipeline mixer or the first section of the coagulation reaction tank. A 0.1% concentration of anionic polyacrylamide solution is added to the flocculation reaction zone. The flocculated wastewater enters the inclined plate sedimentation tank. The clear liquid at the top enters the next step for oxidation, and the colloidal sediment at the bottom is sent to the sludge treatment unit for treatment.
[0010] S3: Core oxidation and iron sludge reflux: In the secondary treatment step, the upper clear liquid is introduced into the acidification and activation tank at a flow rate of 30%-50% through the diversion valve. At the same time, the concentrated iron sludge from the iron sludge storage tank is pumped into the acidification and activation tank at a set reflux ratio through the screw reflux pump.
[0011] In the acidification and activation tank, start the mechanical stirrer and introduce the mixed liquid from the acidification and activation tank along with the remaining 50%-70% of the pretreated effluent into the Fenton main reaction tank. Then, add oxidant to the Fenton main reaction tank through a metering pump to carry out the oxidation reaction.
[0012] The oxidized wastewater enters the neutralization flocculation sedimentation tank, and sodium hydroxide is added in the first compartment to adjust the pH of the effluent to 8-9, so that iron ions are converted into iron sludge and precipitate. The iron sludge settles at the bottom of the tank, part of which is sent to the iron sludge storage tank through a return pump, and part of which is discharged as the remaining iron sludge. The supernatant after neutralization enters the next step.
[0013] S4: In step S3, the upper clear liquid flows into the hydrolysis acidification tank by gravity. After hydrolysis and acidification, the effluent enters the aerobic biological tank, where oxygen is supplied by a blower and microporous aeration. The mixed liquid in the aerobic tank enters the secondary sedimentation tank for mud-water separation.
[0014] S5: In step S4, the supernatant is pumped into the activated carbon adsorption tower for adsorption. The adsorbed water then enters the clean water disinfection tank for disinfection and is discharged.
[0015] Preferably, the chemical sludge from step S2, the residual iron sludge from step S3, and the residual activated sludge from step S4 are separately or mixed and then dewatered by a plate and frame filter press.
[0016] Preferably, the oxidant is hydrogen peroxide.
[0017] Preferably, in step S3, the ratio of the upper clear liquid and the return flow rate of the iron sludge in the secondary treatment step are controlled by a battery flow meter and a return pump frequency converter.
[0018] Preferably, the regulating tank is equipped with an aeration system or an underwater agitator.
[0019] Preferably, the acidic activation tank is equipped with an online pH monitor and a stirring device.
[0020] Preferably, the Fenton main reaction tank is equipped with an online ORP monitor, and the dosage of the oxidant is controlled by monitoring the oxidation-reduction potential during the oxidation reaction step.
[0021] Preferably, if insufficient oxidation efficiency is detected in step S3, ferrous sulfate solution needs to be replenished.
[0022] Compared with the prior art, the beneficial effects of the present invention are:
[0023] 1. A portion of the iron sludge produced during the reaction is recycled to the acidic activation tank. In the acidic activation tank, acidic agents are added to dissolve the iron sludge back into catalytically active Fe³⁺ / Fe²⁺ ions, which then participate in the Fenton catalytic reaction again. The mixed solution in the acidification tank is then introduced into the Fenton main reaction tank. This reduces the amount of ferrous sulfate added in the Fenton catalytic reaction and allows some of the acidic substances in the acidic activation tank to enter the Fenton main reaction tank, thus reducing the amount of acidic substances required for the Fenton reaction to be carried out in a strongly acidic environment.
[0024] 2. By adding an acidic activation tank, the iron sludge that needs to be treated and discarded can be reused, which not only reduces the amount of reactants used but also greatly reduces the amount of iron sludge that needs to be treated, further reducing process costs.
[0025] 3. During the repeated dissolution and precipitation of iron sludge, its catalytic activity may decrease. Maintaining an appropriate amount of ferrous sulfate supplementation can ensure the effectiveness of the Fenton catalytic reaction. Attached Figure Description
[0026] Figure 1 This is a process flow diagram of the fluorescent wastewater treatment process of the present invention. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Please see Figure 1 The present invention provides a technical solution:
[0029] A fluorescent wastewater treatment process includes the following steps:
[0030] S1: Primary pretreatment: Wastewater first passes through a screen to remove large floating and suspended solids, and then enters an equalization tank to adjust the water quality and quantity. The equalization tank is equipped with an aeration system or an underwater mixer.
[0031] When fluorescent wastewater is discharged, it is filtered through a screen to remove large floating and suspended solids. The filtered wastewater then enters the equalization tank. In the equalization tank, the wastewater is stirred or aerated to ensure that water of different concentrations is fully mixed. The continuous stirring and aeration prevents the sedimentation of suspended solids and ensures uniform water quality.
[0032] S2: Secondary pretreatment: The effluent from the equalization tank is pumped to the coagulation reaction tank using a metering pump. A 10% concentration of polyaluminum chloride solution is added to the pipeline mixer or the first section of the coagulation reaction tank. A 0.1% concentration of anionic polyacrylamide solution is added to the flocculation reaction zone. The flocculated wastewater enters the inclined plate sedimentation tank. The clear liquid at the top enters the next step for oxidation, and the colloidal sediment at the bottom is sent to the sludge treatment unit for treatment.
[0033] The influent volume for the secondary pretreatment is determined by a metering pump. A polyaluminum chloride (PAC) solution matching the influent volume is added to the coagulation reaction tank at a dosage of 200-500 grams per liter (calculated based on a fixed weight of the reactants). After dissolving in water, the PAC solution hydrolyzes into numerous positively charged complexes, neutralizing the negative charges on the surfaces of colloidal particles in the wastewater. The aluminum hydroxide colloids produced after the hydrolysis of the PAC solution have strong adsorption capacity, adsorbing a large number of particles in the wastewater to form flocs. These flocs aggregate the difficult-to-settle suspended solids in the wastewater into heavier, more easily settled flocs within the inclined plate sedimentation tank, thus achieving sedimentation. In this embodiment, an anionic polyacrylamide solution is added to the wastewater after the reaction to further ensure the coagulation and sedimentation effect, amplifying the flocculation effect of the PAC solution.
[0034] S3: Core Oxidation and Iron Sludge Recirculation: In the secondary treatment step, the upper clear liquid is introduced into the acidification and activation tank at a flow rate of 30%-50% through a diversion valve. At the same time, the concentrated iron sludge from the iron sludge storage tank is pumped into the acidification and activation tank at a set recirculation ratio through a screw recirculation pump. The acidification and activation tank is equipped with an online pH monitor and a stirring device. The ratio of the upper clear liquid and the iron sludge recirculation flow rate in the secondary treatment step are controlled by a battery flow meter and a recirculation pump frequency converter.
[0035] By using an electromagnetic flowmeter and a frequency converter for the reflux pump, the ratio of raw water flow and the reflux flow of iron sludge are precisely controlled. If all the supernatant from the secondary treatment step is introduced into the acidification and activation tank at once, the pH value of the supernatant will be close to 7. If it is to be reduced to below 2.5, a large amount of acid will be required. Diverting the flow can reduce the amount of acid used in the acidification and activation tank and shorten the time it takes for the pH value to drop from 7 to below 2.5. A portion of the iron sludge is pumped into the acidification and activation tank through the reflux pump. The iron sludge Fe(OH)3 can dissolve into Fe³⁺ under acidic conditions, which can catalyze the subsequent hydrogen peroxide to produce highly active hydroxyl radicals, which are used to break the chromophores and benzene ring structures of fluorescent organic molecules, thereby achieving decolorization and organic mineralization.
[0036] Simultaneously, the pH value changes are monitored by an online pH monitor inside the acidification and activation tank, and the addition of concentrated sulfuric acid is precisely controlled. When the pH value peaks above 2.5, the concentrated sulfuric acid dosing pump is activated to stabilize the pH value within the range of 2.0-3.5. The water retention time here is no less than 50 minutes to ensure that Fe(OH)3 in the iron sludge can be fully dissolved and converted into Fe³⁺ with catalytic activity. Then, the mixed solution enters the Fenton main reaction tank, where the mixed solution is an acidic mixture with activated iron ions.
[0037] In the acidification and activation tank, the mechanical stirrer is started, and the mixed liquid from the acidification and activation tank, together with the remaining 50%-70% of the pretreated effluent, is introduced into the Fenton main reaction tank. An oxidant, hydrogen peroxide, is added to the Fenton main reaction tank through a metering pump to carry out the oxidation reaction. The Fenton main reaction tank is equipped with an online ORP monitor. During the oxidation reaction step, the amount of oxidant added is adjusted by monitoring the oxidation-reduction potential. If the oxidation efficiency is insufficient, ferrous sulfate solution needs to be added.
[0038] After acidification and activation, the mixed solution from the acidification and activation tank, along with the remaining pretreated effluent, is introduced into the Fenton main reactor. The overall pH will rise, but it can be maintained within the optimal pH range for the Fenton reaction, which is 2.5-4.0. This reduces the need for pH adjustments within the Fenton main reactor and decreases the overall acid consumption. If the online ORP monitor in the Fenton main reactor detects insufficient oxidation efficiency, ferrous sulfate solution needs to be added. This is a safety redundancy design. During repeated dissolution and precipitation of iron sludge, the catalytic activity may decrease, potentially leading to ineffective hydrogen peroxide catalysis. Simultaneously, the online ORP monitor enables precise hydrogen peroxide dosing. The ORP value directly reflects the remaining oxidant level and oxidation capacity within the reactor.
[0039] The oxidized wastewater enters the neutralization flocculation sedimentation tank, and sodium hydroxide is added in the first compartment to adjust the pH of the effluent to 8-9, so that iron ions are converted into iron sludge and precipitate. The iron sludge settles at the bottom of the tank, part of which is sent to the iron sludge storage tank through a return pump, and part of which is discharged as the remaining iron sludge. The supernatant after neutralization enters the next step.
[0040] The effluent from the Fenton main reactor, after oxidation, enters the flocculation sedimentation tank. Sodium hydroxide is added to the flocculation sedimentation tank via an online pH meter and sodium hydroxide dosing pump to adjust the pH of the effluent to the range of 8-9, meeting the pH requirements for biochemical treatment or discharge. At this time, iron ions are converted into Fe(OH)3 precipitate again. The treated water and iron sludge are then separated. The water enters the next unit, while a portion of the iron sludge is sent to the iron sludge storage tank to prepare raw materials for the next process cycle. A portion is directly discharged. Periodically discharging a certain proportion of the remaining iron sludge can remove some inorganic salts, heavy metals, and other impurities that cannot be indirectly removed from the wastewater. If the iron sludge is constantly being recycled and reused, it will lead to an increase in impurities in the iron sludge, affecting the catalytic effect on subsequent hydrogen peroxide.
[0041] S4: In step S3, the upper clear liquid flows into the hydrolysis acidification tank by gravity. After hydrolysis and acidification, the effluent enters the aerobic biological tank, where oxygen is supplied by a blower and microporous aeration. The mixed liquid in the aerobic tank enters the secondary sedimentation tank for mud-water separation.
[0042] The supernatant from the oxidation process in the Fenton main reactor enters the hydrolysis-acidification tank. During this step, the effluent from the Fenton main reactor is not yet fully treated and still contains large organic molecules with complex structures. In the anaerobic environment inside the hydrolysis-acidification tank, the large organic molecules are further decomposed into small organic acids. The effluent from the Fenton main reactor remains in the hydrolysis-acidification tank for 8-12 hours. Hydrolysis-acidification is a relatively slow biological process and requires sufficient time for the microorganisms to fully contact and react with the substrate.
[0043] The effluent from the hydrolysis and acidification process enters the aerobic biological tank, where the metabolic activity of aerobic microorganisms oxidizes and decomposes the small-molecule organic matter provided by the hydrolysis and acidification process into carbon dioxide and water. Oxygen is supplied through blowers and microporous aeration, creating the conditions for an aerobic reaction.
[0044] Then, the mixed liquid flowing out of the aerobic biological tank is subjected to sedimentation and separation to obtain clear biochemical effluent.
[0045] S5: In step S4, the supernatant is pumped into the activated carbon adsorption tower for adsorption. The adsorbed water then enters the clean water disinfection tank for disinfection and is then discharged.
[0046] The effluent from the aerobic biological tank enters the activated carbon adsorption tower to deeply remove trace amounts of difficult-to-biodegrade organic matter remaining in the effluent after biological treatment. During the biological treatment process, a large number of bacteria will multiply, and the microbial indicators carried by the effluent usually cannot meet the discharge standards. The adsorbed water needs to be disinfected in the clear water disinfection tank before being discharged. Common disinfectants or ultraviolet light can be used for disinfection until the corresponding discharge standards are met.
[0047] Chemical sludge from step S2, residual iron sludge from step S3, and residual activated sludge from step S4 are either separately or mixed and then fed into a sludge thickening tank. The sludge is then dewatered by a plate and frame filter press. Adding a certain amount of lime during the iron sludge treatment step can improve the dewatering performance of the sludge, control the filter press time, and ensure that the moisture content of the sludge cake is not too high.
[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A fluorescent wastewater treatment process, characterized in that, Includes the following steps: S1: Primary pretreatment: Wastewater first passes through a screen to remove large floating and suspended solids, and then enters an equalization tank to adjust the water quality and quantity. S2: Secondary pretreatment: The effluent from the equalization tank is pumped to the coagulation reaction tank using a metering pump. A 10% concentration of polyaluminum chloride solution is added to the pipeline mixer or the first section of the coagulation reaction tank. A 0.1% concentration of anionic polyacrylamide solution is added to the flocculation reaction zone. The flocculated wastewater enters the inclined plate sedimentation tank. The clear liquid at the top enters the next step for oxidation, and the colloidal sediment at the bottom is sent to the sludge treatment unit for treatment. S3: Core oxidation and iron sludge reflux: In the secondary treatment step, the upper clear liquid is introduced into the acidification and activation tank at a flow rate of 30%-50% through the diversion valve. At the same time, the concentrated iron sludge from the iron sludge storage tank is pumped into the acidification and activation tank at a set reflux ratio through the screw reflux pump. In the acidification and activation tank, start the mechanical stirrer and introduce the mixed liquid from the acidification and activation tank along with the remaining 50%-70% of the pretreated effluent into the Fenton main reaction tank. Then, add oxidant to the Fenton main reaction tank through a metering pump to carry out the oxidation reaction. The oxidized wastewater enters the neutralization flocculation sedimentation tank, and sodium hydroxide is added in the first compartment to adjust the pH value of the effluent to 8-9, so that iron ions are converted into iron sludge and precipitate. The iron sludge settles at the bottom of the tank, part of which is sent to the iron sludge storage tank through the return pump, and part of which is discharged as the remaining iron sludge. The supernatant after neutralization enters the next step. S4: In step S3, the upper clear liquid flows into the hydrolysis acidification tank by gravity. After hydrolysis and acidification, the effluent enters the aerobic biological tank, where oxygen is supplied by a blower and microporous aeration. The mixed liquid in the aerobic tank enters the secondary sedimentation tank for mud-water separation. S5: In step S4, the supernatant is pumped into the activated carbon adsorption tower for adsorption. The adsorbed water enters the clean water disinfection tank for disinfection and then is discharged.
2. The fluorescent wastewater treatment process according to claim 1, characterized in that: Chemical sludge from step S2, residual iron sludge from step S3, and residual activated sludge from step S4 are either separately or mixed and then dewatered by a plate and frame filter press.
3. The fluorescent wastewater treatment process according to claim 1, characterized in that: The oxidant is hydrogen peroxide.
4. The fluorescent wastewater treatment process according to claim 1, characterized in that: In step S3, the ratio of the upper clear liquid and the return flow rate of the iron sludge in the secondary treatment step are controlled by the battery flow meter and the return pump frequency converter.
5. The fluorescent wastewater treatment process according to claim 1, characterized in that: The regulating tank is equipped with an aeration system or an underwater agitator.
6. The fluorescent wastewater treatment process according to claim 1, characterized in that: The acidic activation tank is equipped with an online pH monitor and a stirring device.
7. The fluorescent wastewater treatment process according to claim 1, characterized in that: The Fenton main reaction tank is equipped with an online ORP monitor. In the oxidation reaction step, the dosage of the oxidant is controlled by monitoring the oxidation-reduction potential.
8. The fluorescent wastewater treatment process according to claim 1, characterized in that: If insufficient oxidation efficiency is detected in step S3, ferrous sulfate solution needs to be replenished.