COD / organophosphorus wastewater treatment method based on cooperation of UV / H2O2 and coagulating sedimentation

Abstract

The invention relates to a UV / H2O2 and coagulative precipitation synergetic COD / organophosphorus wastewater treatment method which comprises the following steps: pretreating COD / organophosphorus wastewater to remove suspended solids and oil substances in the wastewater; detecting the COD value and the organophosphorus content of the pretreated wastewater, and calculating the dosage of H2O2 according to the detection result; introducing the wastewater added with H2O2 into a photocatalytic oxidation circulation system, starting a UV lamp tube to carry out circulation oxidation treatment, and sampling and detecting according to a preset time interval during the period; introducing the wastewater subjected to UV / H2O2 photocatalytic oxidation treatment into a coagulation reaction tank, adding a coagulant and stirring; and introducing the wastewater subjected to the coagulation reaction into a sedimentation tank for solid-liquid separation. The invention aims to provide the COD / organophosphorus wastewater treatment method with synergism of UV / H2O2 and coagulating sedimentation, which has the advantages of strong suitability, no secondary pollution, simple process and stable treatment effect.

Description

Technical Field

[0001] This invention relates to a wastewater treatment method, and more particularly to a COD / organophosphorus wastewater treatment method that combines UV / H2O2 with coagulation and sedimentation. Background Technology

[0002] With the continuous development of science and technology and the increasing social demand, various industrial sectors have flourished, and the amount of wastewater discharged during various industrial production processes has also increased exponentially. In particular, organophosphorus wastewater, which is highly harmful to the ecology and human beings, has a complex composition and is highly toxic. If discharged directly, it will seriously pollute the water environment. Therefore, it needs to be treated in depth to meet the standards before being discharged.

[0003] Currently, the main methods for removing organophosphates and COD from wastewater on the market include the following categories: Biological treatment technology: It utilizes the metabolic activities of polyphosphate-accumulating bacteria to convert organic phosphorus and organic matter. However, this method is only suitable for wastewater with low toxicity and easy degradation. For wastewater containing toxic and harmful substances (such as heavy metals and recalcitrant organic matter), the microorganisms are easily inactivated, resulting in extremely poor treatment effects. In addition, it requires the cultivation of specific bacterial strains, which leads to high operation and maintenance costs. Chemical precipitation method: Phosphorus is removed by adding agents such as iron salts and aluminum salts to generate precipitates. However, this method is only effective for inorganic phosphorus and has a low removal rate for organic phosphorus. In addition, it generates a large amount of chemical sludge, causing secondary pollution and high subsequent sludge treatment costs. Adsorption method: This method uses adsorbents such as activated carbon and resin to adsorb organic phosphorus and organic matter. However, once the adsorbent is saturated, it needs to be regenerated or replaced, resulting in high operating costs and difficulty in achieving deep treatment, making it difficult for the effluent to meet standards. Single advanced oxidation technologies (such as Fenton oxidation and ozone oxidation): Although they can oxidize organic phosphorus into inorganic phosphorus, they cannot separate inorganic phosphorus from water. They require additional phosphorus removal processes, and some processes (such as Fenton oxidation) will generate sludge, increasing the treatment process. Reverse osmosis membrane separation: Although it can separate phosphorus and organic matter, the membrane modules are expensive, prone to clogging, and difficult to maintain. It is only suitable for high-requirement, small-volume treatment scenarios and is difficult to apply on a large scale.

[0004] Therefore, there is still a lack of a wastewater treatment method that is suitable for toxic and harmful organophosphorus wastewater, does not produce secondary pollution, and has a good treatment effect. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for treating COD / organic phosphorus wastewater that combines UV / H2O2 with coagulation and sedimentation, exhibiting strong adaptability, no secondary pollution, simple process, and stable treatment effect.

[0006] This invention discloses a method for treating COD / organophosphorus wastewater using a synergistic effect of UV / H2O2 and coagulation sedimentation, comprising the following steps: Pretreatment of COD / organophosphorus wastewater removes suspended solids and oily substances from the wastewater; The COD value and organic phosphorus content of the pretreated wastewater are tested, and the amount of H2O2 to be added is calculated based on the test results. The H2O2 is then added to the wastewater in one go. The wastewater after adding H2O2 is introduced into a photocatalytic oxidation cycle system, and the UV lamps are started for cyclic oxidation treatment. During this period, samples are taken and tested at preset time intervals until the COD value and organic phosphorus content of the wastewater meet the preset indicators. The wastewater treated by UV / H2O2 photocatalytic oxidation is introduced into a coagulation reaction tank, coagulant is added and stirred, and the preset residence time is maintained. The wastewater after coagulation reaction is introduced into a sedimentation tank for solid-liquid separation. The qualified wastewater after separation is discharged, and the sludge generated by sedimentation is solidified.

[0007] This invention discloses a method for treating COD / organophosphorus wastewater by synergistic use of UV / H2O2 and coagulation sedimentation, wherein the pretreatment process is one or more combinations of filtration, oil separation, or air flotation.

[0008] This invention discloses a method for treating COD / organophosphorus wastewater by synergistic use of UV / H2O2 and coagulation sedimentation, wherein the dosage of H2O2 is calculated based on a molar ratio of H2O2 to COD of the wastewater of 0.5 to 2:1.

[0009] This invention discloses a method for treating COD / organophosphorus wastewater using a synergistic effect of UV / H2O2 and coagulation sedimentation, wherein the power of the UV lamp is 200-350W, and the circulation time of the wastewater in the UV / H2O2 photocatalytic oxidation cycle system is 30-120min.

[0010] This invention discloses a method for treating COD / organophosphorus wastewater by synergistic use of UV / H2O2 and coagulation sedimentation, wherein the preset time interval for interval sampling and detection is 30 to 60 minutes.

[0011] This invention discloses a method for treating COD / organophosphorus wastewater by synergistic use of UV / H2O2 and coagulation sedimentation, wherein the coagulant is ferrous sulfate, polyaluminum chloride, or a composite of PAC and PAM, the dosage of the coagulant is 50-200 mg / L, and the retention time is 15-30 min.

[0012] This invention discloses a method for treating COD / organic phosphorus wastewater by synergistic use of UV / H2O2 and coagulation sedimentation, wherein the sedimentation tank is an inclined tube sedimentation tank or a horizontal flow sedimentation tank, and the solid-liquid separation time is 30-60 min.

[0013] The difference between this invention and the prior art is that this invention uses a pretreatment process to remove large particulate matter and oil from organophosphorus wastewater, uses an advanced oxidation process to oxidize the organophosphorus in the wastewater into inorganic phosphorus, and then uses a coagulation and sedimentation process to settle the inorganic phosphorus, thereby achieving the removal of organophosphorus. In addition, the UV / H2O2 photocatalytic oxidation process can remove COD while oxidizing organophosphorus, and no sludge is generated in the process of removing organophosphorus and COD.

[0014] The present invention provides a method for treating COD / organophosphorus wastewater using a synergistic effect of UV / H2O2 and coagulation sedimentation, which includes at least the following beneficial effects: This treatment method overcomes the shortcomings of existing technologies, such as poor adaptability of biological treatment methods, secondary pollution caused by chemical precipitation methods, and the inability of single advanced oxidation methods to completely remove phosphorus. It achieves deep treatment of toxic and harmful organophosphorus wastewater, without the generation of sludge, with simple process and low cost. In addition, it can also treat toxic and harmful wastewater that is not suitable for activated sludge treatment to meet the standards, and has great promotional value.

[0015] The invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of a COD / organic phosphorus wastewater treatment method based on the synergistic effect of UV / H2O2 and coagulation sedimentation according to the present invention. Detailed Implementation

[0017] like Figure 1 As shown, the present invention discloses a method for treating COD / organophosphorus wastewater using a synergistic effect of UV / H2O2 and coagulation sedimentation, comprising the following steps: Pretreatment of COD / organophosphorus wastewater removes suspended solids and oily substances from the wastewater; The COD value and organic phosphorus content of the pretreated wastewater are tested, and the amount of H2O2 to be added is calculated based on the test results. The H2O2 is then added to the wastewater in one go. The wastewater after adding H2O2 is introduced into a photocatalytic oxidation cycle system, and the UV lamps are started for cyclic oxidation treatment. During this period, samples are taken and tested at preset time intervals until the COD value and organic phosphorus content of the wastewater meet the preset indicators. The wastewater treated by UV / H2O2 photocatalytic oxidation is introduced into a coagulation reaction tank, coagulant is added and stirred, and the preset residence time is maintained. The wastewater after coagulation reaction is introduced into a sedimentation tank for solid-liquid separation. The qualified wastewater after separation is discharged, and the sludge generated by sedimentation is solidified.

[0018] The pretreatment process is one or a combination of filtration, oil separation, or air flotation.

[0019] The dosage of H2O2 is calculated based on a molar ratio of H2O2 to COD in wastewater of 0.5 to 2:1.

[0020] The power of the UV lamp tube is 200-350W, and the circulation time of the wastewater in the UV / H2O2 photocatalytic oxidation cycle system is 30-120min.

[0021] The preset time interval for interval sampling and testing is 30 to 60 minutes.

[0022] The coagulant is ferrous sulfate, polyaluminum chloride, or a combination of PAC and PAM. The dosage of the coagulant is 50–200 mg / L, and the residence time is 15–30 min.

[0023] The sedimentation tank is either an inclined tube sedimentation tank or a horizontal flow sedimentation tank, and the solid-liquid separation time is 30 to 60 minutes.

[0024] The steps for treating organophosphorus wastewater are as follows: Step 1, Pretreatment process: The wastewater is pretreated to remove suspended solids (such as silt, solid impurities, and a small amount of precipitated flocs), oils, and other substances, thereby reducing the turbidity of the wastewater and ensuring that the surface of the UV lamps does not scale, the UV / H2O2 reactor and the coagulation reaction tank do not become clogged, and the treatment efficiency is guaranteed.

[0025] When filtering large particulate impurities, quartz sand filters, filter cloth filters, and bar screen filters can be used for filtration; when treating oily wastewater, oil-water separators and oil separators can be used for efficient oil separation. Once there is no obvious floating oil in the wastewater, the next step can be carried out.

[0026] Step 2, H2O2 addition: Detect the COD value according to national standard HJ828-2017, and the total phosphorus and organic phosphorus content according to national standard HJ670-2013. The organic phosphorus content is the difference between total phosphorus and inorganic phosphorus. Calculate the H2O2 dosage based on the COD value and organic phosphorus content, and then add the H2O2 to the wastewater all at once to ensure sufficient contact between H2O2 and the wastewater.

[0027] H2O2 dosage calculation formula (minor adjustments may be made in industrial practice): H2O2 dosage (mg / L) = [COD detection value (mg / L) × molar ratio (H2O2:COD) × 34] / 16 × excess coefficient.

[0028] The excess coefficient is 1.1 to 1.3.

[0029] Step 3, UV / H2O2 photocatalytic oxidation cycle treatment: The wastewater after H2O2 addition is introduced into the UV / H2O2 photocatalytic oxidation inlet tank using a booster pump, and then introduced into the advanced oxidation reactor via a circulating water pump. The reactor is equipped with UV lamps, and the UV lamps are then activated for cycle oxidation treatment. Under the irradiation of the UV lamps, H2O2 generates highly oxidizing ·OH, which oxidizes and decomposes the organic phosphorus in the wastewater into inorganic phosphorus, while simultaneously degrading COD. No sludge is generated during the entire process. During the treatment, COD and organic phosphorus content are sampled and tested every 30-60 minutes until the test results meet the preset indicators, at which point the oxidation treatment is stopped.

[0030] It should be noted that the preset indicators are usually the influent indicators for the next step (i.e., coagulation reaction), and these indicators may fluctuate depending on the type of wastewater. For example, the preset indicators may be set to COD≤20mg / L and organic phosphorus≤1mg / L.

[0031] Oxidation methods can efficiently degrade organic matter, mainly including chemical oxidation, photocatalytic oxidation, wet oxidation, and supercritical water oxidation. Among them, the UV / H2O2 photocatalytic oxidation method used in this invention is a type of chemical oxidation, which has the advantages of simple process and no solid waste generated during the treatment compared with other oxidation methods.

[0032] Step 4, coagulation reaction: The effluent after UV / H2O2 oxidation is introduced into the coagulation reaction tank, and a coagulant (ferrous sulfate, polyaluminum chloride or PAC and PAM composite agent) is added at a dosage of 50-200 mg / L. After stirring evenly, the water is kept for a residence time of 15-30 minutes to allow the inorganic phosphorus to react with the coagulant to form insoluble precipitates.

[0033] Step 5, Sedimentation and Sludge Treatment: The wastewater after coagulation reaction is introduced into a sedimentation tank (inclined tube sedimentation tank or horizontal flow sedimentation tank) and allowed to stand for 30-60 minutes to achieve solid-liquid separation; the supernatant after separation is tested and found to have total phosphorus ≤0.5mg / L and COD ≤20mg / L, meeting the municipal Class A discharge requirements, and is directly discharged; the sludge generated by sedimentation is solidified after being filtered by a filter press, and the sludge production is much lower than that of traditional chemical precipitation methods.

[0034] It should be noted that the specific choice of sedimentation tank can be determined according to the wastewater quality. If the wastewater has a large amount of flocs and high turbidity (such as nickel leaching wastewater), an inclined tube sedimentation tank is selected to take advantage of its dense interception, shorten the wastewater retention time, improve separation efficiency, and occupy less space. If the wastewater has low turbidity and high salt content (such as RO membrane concentrate), a horizontal flow sedimentation tank is selected. Its structure is simple and has strong resistance to shock loads, which can avoid component blockage caused by high salt and reduce later operation and maintenance costs.

[0035] The organophosphorus wastewater treatment method of the present invention has the following significant advantages compared with the prior art: Wide adaptability: It can treat toxic and harmful organophosphorus wastewater (such as nickel smelting wastewater and RO membrane concentrate) that cannot be treated by the activated sludge process, solving the problem of treating highly toxic wastewater. Thorough treatment effect: The organic phosphorus in the wastewater is converted into inorganic phosphorus through UV / H2O2 oxidation, and combined with the synergistic effect of coagulation and sedimentation, the final effluent total phosphorus ≤0.5mg / L and COD ≤20mg / L, meeting the Class A discharge standard; No secondary pollution: The UV / H2O2 oxidation process does not produce sludge, and the amount of sludge produced by coagulation and sedimentation is only 1 / 3 to 1 / 2 of that produced by traditional chemical sedimentation, thus reducing sludge treatment costs. Simple process and low cost: No complex equipment is required, the dosage of H2O2 and coagulant is controllable, the operation and maintenance are simple, and it is suitable for large-scale application. Flexible operation: The pretreatment process, H2O2 dosage, and UV power can be adjusted according to the wastewater quality, making it suitable for COD / organic phosphorus wastewater from different sources and of great promotional value.

[0036] The organophosphorus wastewater treatment method of the present invention will be described below with reference to preferred embodiments. The following embodiments are only exemplary and illustrative. This treatment method is also applicable to the treatment of other wastewater (such as pesticide production wastewater, chemical / pharmaceutical organophosphorus product production wastewater, etc.) and has the same effect.

[0037] Organic phosphorus wastewater parameter table: The analysis results are as follows, based on samples taken at regular time intervals: Example 1: Treatment of nickel smelting wastewater Wastewater source parameters: COD: 114 mg / L; Total phosphorus (mainly organic phosphorus): 128.3 mg / L; pH: 7.09; Electrical conductivity: 1656 μS / cm; Physical properties: white, slightly turbid liquid.

[0038] Processing steps: Step 1: Pretreatment: Quartz sand filtration is used to remove suspended solids from the wastewater and reduce its turbidity. Once the turbidity meets the preset standard, proceed to the next step (e.g., set the wastewater turbidity to: turbidity ≤ 5 NTU). Step 2: H2O2 addition: The COD of the pretreated wastewater was measured to be 110 mg / L. Based on the molar ratio of H2O2 to COD of 1.7:1, 1.2 mg / L of 30% H2O2 solution was added and stirred evenly. Step 3: UV / H2O2 oxidation: UV lamp power 250W (wavelength 254nm), cyclic treatment for 60min; samples were taken every 40min during the process. After 60min of oxidation, COD=13mg / L, total phosphorus=100.0mg / L (organic phosphorus has been converted to inorganic phosphorus). Step 4: Coagulation reaction: Add 100 mg / L polyaluminum chloride (PAC) + 5 mg / L PAM, stir and let stand for 20 min; Step 5: Sedimentation separation: An inclined tube sedimentation tank was used. After standing for 40 minutes, the total phosphorus in the supernatant after solid-liquid separation was 0.46 mg / L and the COD was 13 mg / L.

[0039] Example 2: Treatment of RO membrane concentrate Wastewater source parameters: COD: 55 mg / L; Total phosphorus (mainly organic phosphorus): 71.36 mg / L; pH: 9.08; Electrical conductivity: 26.9 mS / cm; Physical properties: light yellow, transparent liquid.

[0040] Processing steps: Step 1: Pretreatment: A combination of oil separation and filtration is used to remove oil and suspended solids; Step 2: H2O2 addition: The COD of the pretreated wastewater was detected to be 52 mg / L. Based on the molar ratio of H2O2 to COD of 2:1, 0.6 mg / L of 30% H2O2 solution was added and stirred evenly. Step 3: UV / H2O2 oxidation: UV lamp power 200W, cyclic treatment for 30min, with samples taken every 30min during the process; COD after oxidation = 17mg / L, total phosphorus = 69.1mg / L; Step 4: Coagulation reaction: Add 150 mg / L ferrous sulfate + 3 mg / L PAM, stir and let stand for 25 minutes; Step 5: Sedimentation separation: A horizontal flow sedimentation tank was used. After standing for 50 minutes, the total phosphorus in the supernatant after solid-liquid separation was 0.25 mg / L and the COD was 17 mg / L.

[0041] After treatment, the total phosphorus (0.46 mg / L and 0.25 mg / L) in the two organophosphorus wastewaters in the above two embodiments were both ≤0.5 mg / L, and the COD (13 mg / L and 17 mg / L) were both ≤20 mg / L, which met the Class A discharge requirements of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), proving that the technical solution of the present invention is stable and effective.

[0042] It should be noted that the terms "center", "upper", "lower", "front", "rear", "left", "right", "middle", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for treating COD / organophosphorus wastewater using a synergistic effect of UV / H2O2 and coagulation sedimentation, characterized in that... Includes the following steps: Pretreatment of COD / organophosphorus wastewater removes suspended solids and oily substances from the wastewater; The COD value and organic phosphorus content of the pretreated wastewater are detected, and the amount of H2O2 to be added is calculated based on the detection results. The H2O2 is then added to the wastewater in one go. The wastewater after adding H2O2 is introduced into a photocatalytic oxidation cycle system, and the UV lamps are started for cyclic oxidation treatment. During this period, samples are taken and tested at preset time intervals until the COD value and organic phosphorus content of the wastewater meet the preset indicators. The wastewater treated by UV / H2O2 photocatalytic oxidation is introduced into a coagulation reaction tank, coagulant is added and stirred, and the preset residence time is maintained. The wastewater after coagulation reaction is introduced into a sedimentation tank for solid-liquid separation. The qualified wastewater after separation is discharged, and the sludge generated by sedimentation is solidified.

2. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 1, characterized in that: The pretreatment process is one or a combination of filtration, oil separation, or air flotation.

3. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 2, characterized in that... The dosage of H2O2 is calculated based on a molar ratio of H2O2 to COD in wastewater of 0.5 to 2:

1.

4. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 3, characterized in that: The power of the UV lamp is 200-350W, and the circulation time of the wastewater in the UV / H2O2 photocatalytic oxidation cycle system is 30-120min.

5. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 4, characterized in that: The preset time interval for the interval sampling and detection is 30 to 60 minutes.

6. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 5, characterized in that: The coagulant is ferrous sulfate, polyaluminum chloride, or a composite of PAC and PAM. The dosage of the coagulant is 50-200 mg / L, and the residence time is 15-30 min.

7. The method for treating COD / organophosphorus wastewater by synergistic effect of UV / H2O2 and coagulation sedimentation according to claim 6, characterized in that: The sedimentation tank is an inclined tube sedimentation tank or a horizontal flow sedimentation tank, and the solid-liquid separation time is 30 to 60 minutes.

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