Wastewater treatment device and method for treating thiourea-containing wastewater

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a wastewater treatment device and a method for treating thiourea-containing wastewater. The wastewater treatment device provided by this invention includes a sulfur autotrophic short-cut denitrification zone 1, a sedimentation zone 2, and a partial nitrification-anaerobic ammonium oxidation zone 3, connected sequentially. The sulfur autotrophic short-cut denitrification zone 1 and the sedimentation zone 2 are connected by a first water passage 7-1, with the inlet of the first water passage 7-1 located at the upper end of the sulfur autotrophic short-cut denitrification zone 1 and the outlet of the first water passage 7-1 located at the lower end of the sedimentation zone 2. The sedimentation zone 2 and the partial nitrification-anaerobic ammonium oxidation zone 3 are connected by a second water passage 7-2, with the inlet of the second water passage 7-2 located at the upper end of the sedimentation zone 2 and the outlet of the second water passage 7-2 located at the lower end of the partial nitrification-anaerobic ammonium oxidation zone 3. Using the wastewater treatment device of this invention to treat thiourea-containing wastewater can simply and efficiently remove thiourea from the wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a wastewater treatment device and a method for treating thiourea-containing wastewater. Background Technology

[0002] Thiourea, also known as thiourea, has the molecular formula CS(NH2)2 and is mainly used in industry, medicine, agriculture, and electronics. In the electronics industry, thiourea can be used as an extractant for some precious metals. With the rise of the electronics industry, the usage of thiourea has gradually increased, resulting in a rise in thiourea-containing wastewater. Thiourea is highly toxic and poses hereditary risks and can even be fatal to humans and animals.

[0003] Thiourea is biotoxic and severely inhibits nitrification in traditional biological treatment processes. Studies have shown that thiourea can chelate with Cu, the active element in the monooxygenase (AMO) of nitrifying bacteria, inhibiting AMO enzymes and thus suppressing the entire nitrification process. Thiourea strongly inhibits the metabolism and growth of nitrifying bacteria. This inhibition is non-competitive, with an inhibition constant EC50 (KI) of 0.14 mg / L; even low concentrations of thiourea can cause approximately 90% nitrification inhibition. Therefore, direct biological treatment of thiourea-containing wastewater is challenging. Currently, chemical methods, chemical pretreatment-biological methods, advanced oxidation catalysis, or heterotrophic microbial oxidation decomposition are commonly used to treat thiourea-containing wastewater; for example, patents CN110104861A, CN110902828A, and CN109468251A. However, existing treatment methods have problems such as complex operation, high energy consumption, and difficulty in large-scale practical application. Therefore, research on new thiourea treatment methods is urgent. Summary of the Invention

[0004] In view of this, the present invention provides a wastewater treatment device and a method for treating thiourea-containing wastewater. The wastewater treatment device provided by the present invention is simple to operate, easy to apply on a large scale, and can efficiently remove thiourea from the wastewater.

[0005] To solve the above-mentioned technical problems, the present invention provides a wastewater treatment device, comprising a sulfur autotrophic short-range denitrification zone 1, a sedimentation zone 2 and a partially nitrified-anaerobic ammonium oxidation zone 3 connected in sequence.

[0006] The sulfur autotrophic short-cut denitrification zone 1 and the sedimentation zone 2 are connected by a first water passage 7-1. The inlet of the first water passage 7-1 is located at the upper end of the sulfur autotrophic short-cut denitrification zone 1, and the outlet of the first water passage 7-1 is located at the lower end of the sedimentation zone 2. The sedimentation zone 2 and the partial nitrification-anammox zone 3 are connected by a second water passage 7-2. The inlet of the second water passage 7-2 is located at the upper end of the sedimentation zone 2, and the outlet of the second water passage 7-2 is located at the lower end of the partial nitrification-anammox zone 3.

[0007] Preferably, the sedimentation zone 2 is provided with a guide plate 6, and the rotation angle of the guide plate 6 relative to the horizontal direction is 20 to 40°;

[0008] The bottom of the sedimentation zone 2 is provided with a sedimentation collection tank 5, and the bottom of the sedimentation collection tank 5 is provided with a solid discharge hole 11.

[0009] Preferably, an aeration device 8 is provided at the bottom of the partial nitrification-anaerobic ammonium oxidation zone 3;

[0010] The upper end of the partial nitrification-anaerobic ammonium oxidation zone 3 is provided with an outlet 9; the outlet 9 is also connected to a first reflux pipe 4-1 connected to the sedimentation zone 2 and a second reflux pipe 4-2 connected to the sulfur autotrophic short-range denitrification zone 1.

[0011] The present invention also provides a method for treating thiourea-containing wastewater using the wastewater treatment device described above, comprising the following steps:

[0012] The thiourea-containing wastewater is transported to sulfur autotrophic short-cut denitrification zone 1 for sulfur autotrophic short-cut denitrification to obtain sulfur autotrophic short-cut denitrification effluent; the pH value of the sulfur autotrophic short-cut denitrification is 9-10.5.

[0013] The effluent from the sulfur autotrophic short-cut denitrification is transported to sedimentation zone 2 for sedimentation to obtain primary purified effluent; the pH value of sedimentation zone 2 is 7.5-8;

[0014] The primary purified effluent is transported to the partial nitrification-anaerobic ammonium oxidation zone 3 for partial nitrification-anaerobic ammonium oxidation to obtain purified effluent.

[0015] Preferably, the temperature of the sulfur autotrophic short-range denitrification is 20–40°C, and the redox potential is -110–-330 mV.

[0016] Preferably, the upward flow velocity during the sedimentation process is below 1 m / h;

[0017] The dissolved oxygen concentration in the precipitation zone 2 is 0.2–0.4 mg / L, and the oxidation-reduction potential is above 0 mV.

[0018] Preferably, the pH value of the partial nitrification-anaerobic ammonium oxidation is 7-8.5, the temperature is 20-40℃, and the dissolved oxygen concentration is 0.5-2 mg / L.

[0019] Preferably, after obtaining the purified effluent, the method further includes: recirculating the purified effluent to sedimentation zone 2 and sulfur autotrophic short-cut denitrification zone 1 respectively; the recirculation ratio to sedimentation zone 2 is 200-400%, and the recirculation ratio to sulfur autotrophic short-cut denitrification zone 1 is 100-300%.

[0020] Preferably, the hydraulic retention times of the sulfur autotrophic short-range denitrification zone 1, the sedimentation zone 2, and the partial nitrification-anaerobic ammonia oxidation zone 3 are independently 2 to 24 hours.

[0021] Preferably, the thiourea concentration in the thiourea-containing wastewater is 500–10000 mg / L.

[0022] This invention provides a wastewater treatment device, comprising a sulfur autotrophic short-cut denitrification zone 1, a sedimentation zone 2, and a partial nitrification-anaerobic ammonium oxidation zone 3, which are connected in sequence. The sulfur autotrophic short-cut denitrification zone 1 and the sedimentation zone 2 are connected by a first water passage 7-1, the inlet of which is located at the upper end of the sulfur autotrophic short-cut denitrification zone 1, and the outlet of which is located at the lower end of the sedimentation zone 2. The sedimentation zone 2 and the partial nitrification-anaerobic ammonium oxidation zone 3 are connected by a second water passage 7-2, the inlet of which is located at the upper end of the sedimentation zone 2, and the outlet of which is located at the lower end of the partial nitrification-anaerobic ammonium oxidation zone 3. This invention utilizes a wastewater treatment device to treat thiourea-containing wastewater, achieving simple and efficient removal of thiourea from the wastewater. Specifically, it first employs sulfur autotrophic short-cut denitrification, using nitrate as an electron acceptor, to oxidize the organic sulfur in thiourea into elemental sulfur, thereby breaking the thiourea molecular chain and releasing ammonia nitrogen from the thiourea, reducing its toxicity to subsequent denitrification. Simultaneously, nitrate is converted into nitrite. Then, partial nitrification-anaerobic ammonia oxidation is used to convert the released ammonia into nitrogen gas, thus achieving the biodegradation of nitrogen and sulfur in thiourea. Compared with traditional physicochemical processes, the treatment method provided by this invention significantly reduces material and energy consumption in the treatment process. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the wastewater treatment device used in the embodiment, where 1 is the sulfur autotrophic short-cut denitrification zone, 2 is the sedimentation zone, 3 is the partial nitrification-anaerobic ammonium oxidation zone, 4-1 is the first return pipe, 4-2 is the second return pipe, 5 is the sedimentation collection tank, 6 is the guide plate, 7-1 is the first water passage, 7-2 is the second water passage, 8 is the aeration device, 9 is the outlet, 10 is the inlet, and 11 is the solid discharge hole. Detailed Implementation

[0024] The present invention provides a wastewater treatment device, comprising a sulfur autotrophic short-range denitrification zone 1, a sedimentation zone 2, and a partially nitrified-anaerobic ammonia oxidation zone 3 connected in sequence.

[0025] In this invention, the sulfur autotrophic short-cut denitrification zone 1 and the sedimentation zone 2 are connected by a first water passage 7-1, the inlet of which is located at the upper end of the sulfur autotrophic short-cut denitrification zone 1 and the outlet of which is located at the lower end of the sedimentation zone 2; the sedimentation zone 2 and the partial nitrification-anammox zone 3 are connected by a second water passage 7-2, the inlet of which is located at the upper end of the sedimentation zone 2 and the outlet of which is located at the lower end of the partial nitrification-anammox zone 3.

[0026] In one embodiment of the present invention, the sedimentation zone 2 is provided with a guide plate 6, the rotation angle of the guide plate 6 relative to the horizontal direction is preferably 20-40°, more preferably 30°. In the present invention, the sedimentation zone 2 is used for the precipitation and sedimentation of elemental sulfur in the liquid phase after sulfur autotrophic short-range denitrification; the present invention reduces the upward flow velocity of the liquid in the sedimentation zone 2 by setting the guide plate, thereby promoting the precipitation of solids.

[0027] As an embodiment of the present invention, a sedimentation collection tank 5 is provided at the bottom of the sedimentation zone 2, and a solid discharge hole 11 is provided at the bottom of the sedimentation collection tank 5.

[0028] In one embodiment of the present invention, an aeration device 8 is provided at the bottom of the partial nitrification-anaerobic ammonium oxidation zone 3. The present invention provides oxygen to the partial nitrification-anaerobic ammonium oxidation zone 3 through the aeration device 8 to ensure its dissolved oxygen concentration.

[0029] In one embodiment of the present invention, an outlet 9 is provided at the upper end of the partial nitrification-anaerobic ammonium oxidation zone 3. In another embodiment of the present invention, the outlet 9 is also connected to a first reflux pipe 4-1 communicating with the sedimentation zone 2 and a second reflux pipe 4-2 communicating with the sulfur autotrophic short-cut denitrification zone 1. In another embodiment of the present invention, 4-1 is connected to the sedimentation zone 2 through the inlet of the sedimentation zone 2; the second reflux pipe 4-2 is connected to the sulfur autotrophic short-cut denitrification zone 1 through the inlet 10 of the sulfur autotrophic short-cut denitrification zone 1; the inlet 10 of the sulfur autotrophic short-cut denitrification zone 1 is located at the lower end of the sulfur autotrophic short-cut denitrification zone 1.

[0030] The present invention also provides a method for treating thiourea-containing wastewater using the wastewater treatment device described above, comprising the following steps:

[0031] The thiourea-containing wastewater is transported to sulfur autotrophic short-cut denitrification zone 1 for sulfur autotrophic short-cut denitrification to obtain sulfur autotrophic short-cut denitrification effluent; the pH value of the sulfur autotrophic short-cut denitrification is 9-10.5.

[0032] The effluent from the sulfur autotrophic short-cut denitrification is transported to sedimentation zone 2 for sedimentation to obtain primary purified effluent; the pH value of sedimentation zone 2 is 7.5-8;

[0033] The primary purified effluent is transported to the partial nitrification-anaerobic ammonium oxidation zone 3 for partial nitrification-anaerobic ammonium oxidation to obtain purified effluent.

[0034] This invention involves transporting thiourea-containing wastewater to a sulfur autotrophic short-cut denitrification zone 1 for sulfur autotrophic short-cut denitrification, yielding sulfur autotrophic short-cut denitrification effluent. In this invention, the mass concentration of thiourea in the thiourea-containing wastewater is preferably 500–10000 mg / L, more preferably 500–1000 mg / L. In this invention, the pH value of the sulfur autotrophic short-cut denitrification is 9–10.5, preferably 9.5–10. In this invention, the temperature of the sulfur autotrophic short-cut denitrification is preferably 20–40°C, more preferably 30–35°C; the oxidation-reduction potential of the sulfur autotrophic short-cut denitrification is preferably -110–-330 mV, more preferably -120–-200 mV. In this invention, the hydraulic retention time of the sulfur autotrophic short-cut denitrification zone 1 is preferably 2–24 h, more preferably 6–10 h. In this invention, the sulfur autotrophic short-range denitrification refers to the process of using the reduced organic sulfur in thiourea as an electron donor to convert nitrate into nitrite or nitrogen gas, while simultaneously converting itself into elemental sulfur.

[0035] In this invention, the sulfur autotrophic short-cut denitrification zone 1 is preferably equipped with biofilm packing to achieve contact oxidation. This invention reduces nitrates in the effluent from nitrite-anaerobic ammonia oxidation to nitrite via sulfur autotrophic short-cut denitrification, while simultaneously oxidizing sulfur in thiourea to elemental sulfur. This invention ensures that solid sulfur does not precipitate in the sulfur autotrophic short-cut denitrification zone by adjusting the pH and temperature conditions, thereby avoiding biofilm mineralization.

[0036] After obtaining the effluent from the sulfur autotrophic short-cut denitrification process, this invention transports the effluent to sedimentation zone 2 for sedimentation to obtain primary purified effluent. In this invention, the pH value of sedimentation zone 2 is 7.5–8, preferably 8. This invention preferably adjusts the pH value of sedimentation zone 2 by adding hydrochloric acid. This invention has no special requirements on the amount of hydrochloric acid used, as long as the desired pH value is achieved. In this invention, the upward flow velocity during sedimentation is preferably below 1 m / h, more preferably 0.8–1 m / h. In this invention, the dissolved oxygen concentration in sedimentation zone 2 is preferably 0.2–0.4 mg / L, more preferably 0.3 mg / L; the redox potential in sedimentation zone 2 is preferably above 0 mV, more preferably 50–100 mV. This invention limits the pH value, upward flow velocity, and redox potential of sedimentation zone 2 to within the above ranges, which is conducive to the precipitation of elemental sulfur produced by sulfur autotrophic short-cut denitrification. In this invention, the hydraulic retention time of the sedimentation zone 2 is preferably 2 to 24 hours, and more preferably 3 to 5 hours.

[0037] After obtaining the primary purified effluent, the present invention transports the primary purified effluent to a partial nitrification-anammox zone 3 for partial nitrification-anammox oxidation to obtain purified effluent. In the present invention, the pH value of the partial nitrification-anammox oxidation is preferably 7-8.5, more preferably 7.5-8; the temperature of the partial nitrification-anammox oxidation is preferably 20-40℃, more preferably 30-40℃; the dissolved oxygen concentration of the partial nitrification-anammox oxidation is preferably 0.5-2 mg / L, more preferably 1-2 mg / L. In the present invention, the hydraulic retention time of the partial nitrification-anammox oxidation zone 3 is preferably 2-24 h, more preferably 6-10 h. In the present invention, the partial nitrification-anammox oxidation is preferably performed using a biofilm method.

[0038] In this invention, after obtaining the purified effluent, it is preferable to further include: recirculating the purified effluent back to sedimentation zone 2 and sulfur autotrophic short-cut denitrification zone 1, respectively. In this invention, the recirculation ratio to sedimentation zone 2 is preferably 200-400%, more preferably 300-350%; the recirculation ratio to sulfur autotrophic short-cut denitrification zone 1 is preferably 100-300%, more preferably 150-200%. This invention, by controlling the recirculation rate of a portion of the nitrification-anaerobic ammonium oxidation effluent back to the sedimentation zone inlet, ensures that the ORP (oxidation-reduction potential) of the sedimentation zone is greater than 0 mV, thereby reducing the sulfur content. 2- Concentration promotes the precipitation of elemental sulfur.

[0039] This invention utilizes organic sulfur in thiourea as an electron donor through controlled process parameters such as pH during the reaction. This autotrophic short-cut denitrification decomposes thiourea, removing sulfur while reducing its toxicity to subsequent biological denitrification. Subsequently, in a partial nitrification-anaerobic ammonia oxidation process, nitrate is converted to nitrite. This not only fully utilizes pollutants in wastewater and reduces organic carbon source consumption during nitrate removal, but also recovers valuable elemental sulfur resources and reduces the toxicity of thiourea molecules to the subsequent ammonia oxidation process. Furthermore, by adjusting the pH and ORP of the effluent from the sulfide denitrification zone, the release of liquid elemental sulfur from the effluent during the autotrophic short-cut denitrification process is achieved in the sedimentation zone, allowing for solid-liquid separation and recovery of elemental sulfur, rather than allowing solid sulfur to precipitate in the autotrophic short-cut denitrification zone and affecting the continuous reaction between microorganisms and pollutants. To address the ammonia nitrogen generated after thiourea separation, a low-carbon partial nitrification anaerobic ammonia oxidation process is employed for nitrogen removal, significantly reducing the carbon source requirements of traditional nitrification-denitrification processes. The process of this invention is characterized by its low carbon footprint and high efficiency in treating thiourea.

[0040] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] use Figure 1 The integrated device shown treats thiourea-containing wastewater with a thiourea concentration of 500 mg / L.

[0043] Mature sulfur autotrophic short-cut denitrification sludge was inoculated into sulfur autotrophic short-cut denitrification zone 1. The pH value of sulfur autotrophic short-cut denitrification zone 1 was adjusted to 10.5, the temperature to 30℃, the ORP to -120mV, and the hydraulic retention time to 6h. Thiourea-containing wastewater was passed into sulfur autotrophic short-cut denitrification zone 1 for sulfur autotrophic short-cut denitrification to obtain sulfur autotrophic short-cut denitrification effluent.

[0044] The dissolved oxygen concentration in sedimentation zone 2 was adjusted to 0.3 mg / L, the pH value to 8, the upward flow rate to 1 m / h, the oxidation-reduction potential to 100 mV, and the hydraulic retention time to 3 h. The effluent from the sulfur autotrophic short-cut denitrification was then introduced into sedimentation zone 2 for sedimentation to obtain primary purified water.

[0045] The dissolved oxygen concentration in the partial nitrification-anaerobic ammonium oxidation zone 3 was adjusted to 1 mg / L, the pH value to 8, the temperature to 30℃, and the hydraulic retention time to 8 h. The primary purified water was then introduced into the partial nitrification-anaerobic ammonium oxidation zone 3 for partial nitrification-anaerobic ammonium oxidation to obtain purified effluent. The effluent was returned to the sulfur autotrophic short-cut denitrification zone at a reflux ratio of 150% and returned to the sedimentation zone at a reflux ratio of 300%.

[0046] The average desulfurization rate after 30 days of operation according to the example was 2.5 kg / (m³). 3 ·d), the solid sulfur recovery rate is 85%, and the denitrification rate is 2.1 kg / (m³). 3 •d) The effluent sulfate <70mg / L, ammonia nitrogen <8mg / L, and total nitrogen <20mg / L meet the discharge standards. Calculations show that the treatment cost is only 5 yuan / ton of wastewater, significantly reducing the price of 3000 yuan / ton for treating this type of wastewater as hazardous waste.

[0047] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating thiourea-containing wastewater, characterized in that, Includes the following steps: Thiourea-containing wastewater is transported to a sulfur autotrophic short-cut denitrification zone (1) for sulfur autotrophic short-cut denitrification to obtain sulfur autotrophic short-cut denitrification effluent; the pH value of the sulfur autotrophic short-cut denitrification process is 9~10.5; The sulfur autotrophic short-cut denitrification effluent is transported to the sedimentation zone (2) for sedimentation to obtain primary purified effluent; the pH value of the sedimentation zone (2) is 7.5~8; The primary purified effluent is transported to the partial nitrification-anaerobic ammonia oxidation zone (3) for partial nitrification-anaerobic ammonia oxidation to obtain purified effluent.

2. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, The temperature of the sulfur autotrophic short-range denitrification process is 20~40℃, and the redox potential is -330~-110mV.

3. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, The upward flow velocity during the sedimentation process is less than 1 m / h; The dissolved oxygen concentration in the precipitation zone (2) is 0.2~0.4 mg / L, and the oxidation-reduction potential is above 0 mV.

4. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, The pH value of the partial nitrification-anaerobic ammonium oxidation process is 7~8.5, the temperature is 20~40℃, and the dissolved oxygen concentration is 0.5~2mg / L.

5. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, After obtaining the purified effluent, the process also includes: returning the purified effluent to the sedimentation zone (2) and the sulfur autotrophic short-cut denitrification zone (1), respectively; the return ratio to the sedimentation zone (2) is 200~400%, and the return ratio to the sulfur autotrophic short-cut denitrification zone (1) is 100~300%.

6. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, The hydraulic retention time of the sulfur autotrophic short-range denitrification zone (1), sedimentation zone (2) and part of the nitrification-anaerobic ammonia oxidation zone (3) is 2~24h.

7. The method for treating thiourea-containing wastewater according to claim 1, characterized in that, The thiourea concentration in the thiourea-containing wastewater is 500~10000 mg / L.

8. A wastewater treatment device, characterized in that, The device is applied to the method for treating thiourea-containing wastewater as described in any one of claims 1 to 7, comprising a sulfur autotrophic short-range denitrification zone (1), a sedimentation zone (2), and a partial nitrification-anaerobic ammonia oxidation zone (3) connected in sequence. The sulfur autotrophic short-cut denitrification zone (1) and the sedimentation zone (2) are connected by a first water passage (7-1), the inlet of which is located at the upper end of the sulfur autotrophic short-cut denitrification zone (1) and the outlet of which is located at the lower end of the sedimentation zone (2); the sedimentation zone (2) and the partial nitrification-anaerobic ammonium oxidation zone (3) are connected by a second water passage (7-2); the inlet of which is located at the upper end of the sedimentation zone (2) and the outlet of which is located at the lower end of the partial nitrification-anaerobic ammonium oxidation zone (3).

9. The wastewater treatment device according to claim 8, characterized in that, The sedimentation zone (2) is provided with a guide plate (6), and the rotation angle of the guide plate (6) relative to the horizontal direction is 20~40°; The bottom of the sedimentation zone (2) is provided with a sedimentation collection tank (5), and the bottom of the sedimentation collection tank (5) is provided with a solid discharge hole (11).

10. The wastewater treatment apparatus according to claim 8, characterized in that, An aeration device (8) is provided at the bottom of the partial nitrification-anaerobic ammonium oxidation zone (3); The upper end of the partial nitrification-anaerobic ammonia oxidation zone (3) is provided with an outlet (9); the outlet (9) is also connected to a first reflux pipe (4-1) connected to the sedimentation zone (2) and a second reflux pipe (4-2) connected to the sulfur autotrophic short-range denitrification zone (1).

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