Wastewater treatment system

Abstract

A wastewater treatment system is used for treating nitrogen-containing acid wastewater and sequentially comprises, from upstream to downstream, a pretreatment tank in which wastewater is subjected to a neutralization reaction to increase the pH value of the wastewater; the wastewater is subjected to denitrification reaction in the anoxic tank; wherein the wastewater treatment system further comprises a return pipe, and the return pipe is used for connecting the water outlet of the anoxic tank with the pretreatment tank, so that the alkaline wastewater at the water outlet of the anoxic tank flows into the pretreatment tank through the return pipe.

Description

Technical Field

[0001] The utility model relates to a wastewater treatment system, and more specifically to a wastewater treatment system for treating acidic nitrogen-containing wastewater. Background Art

[0002] For acidic nitrogen-containing wastewater (for example, wastewater produced by the production of adipic acid), it is necessary to reduce the acidity of the wastewater before entering the biochemical pool for microbial treatment to prevent the excessively low pH value of the wastewater from killing the microorganisms in the biochemical pool and causing a decrease in the wastewater treatment capacity. In the prior art, alkaline substances are usually added to the wastewater before the acidic nitrogen-containing wastewater enters the biochemical pool to neutralize the wastewater, and then the neutralized wastewater enters the biochemical pool for microbial treatment. However, for the above-mentioned wastewater treatment method, a large amount of alkaline substances need to be consumed. For example, for an adipic acid device that produces 300,000 tons per year, more than 7,500 tons of sodium hydroxide need to be consumed each year, and the corresponding cost is more than 15 million yuan per year.

[0003] To this end, it is desired to propose a wastewater treatment system for treating acidic nitrogen-containing wastewater, so that the system no longer needs to consume a large amount of alkaline substances to pre-neutralize the wastewater, thereby significantly reducing the cost of the system. Utility Model Content

[0004] According to the first aspect of the utility model, a wastewater treatment system is proposed for treating acidic nitrogen-containing wastewater, which includes, from upstream to downstream: a pretreatment tank, in which the wastewater undergoes a neutralization reaction in the initial stage of production to increase the pH value of the wastewater; an anoxic tank, in which the wastewater undergoes a denitrification reaction and produces alkaline substances; wherein the anoxic tank is an SBR biochemical reactor.

[0005] According to the scheme, the alkalinity generated by the denitrification reaction in each reaction batch in the SBR biochemical reactor can be used to neutralize the acidic wastewater, and the acidic wastewater meets the pH value required for the denitrification reaction after being neutralized in the alkalinity-rich water environment. Compared with the prior art in which acidic wastewater is neutralized by adding alkaline substances from the outside, the present scheme neutralizes the acidic wastewater through the alkalinity generated by the denitrification reaction, which greatly reduces the consumption of alkaline substances in the wastewater treatment process, thereby greatly reducing the cost of operating the wastewater treatment system. In addition, the SBR biochemical reactor is used as a separate denitrification tank, and the activated sludge is domesticated in a long-term denitrification state under anoxic environment for a long time. Compared with the conventional AO biochemical tank, the denitrifying bacteria are more concentrated and more active, which makes the denitrification treatment efficiency high, thereby improving the purification capacity of the wastewater treatment system.

[0006] In some embodiments, the wastewater treatment system may further include a reflux pipe, which connects the outlet of the anoxic tank with the pretreatment tank, so that the alkaline wastewater at the outlet of the anoxic tank flows into the pretreatment tank via the reflux pipe.

[0007] According to this scheme, by directing the alkaline wastewater at the outlet of the anoxic tank back to the pretreatment tank and neutralizing the wastewater in the pretreatment tank, part of the effluent alkalinity can be recovered for neutralizing the acidic wastewater, thereby reducing the cost of adding alkaline agents for the operation of part of the wastewater treatment system.

[0008] In some aspects, the wastewater treatment system can be configured to add alkaline material to the pretreatment tank only when the anoxic tank is first started up.

[0009] According to this scheme, before the anoxic pool is started for the first time, since the denitrification reaction has not yet occurred in the anoxic pool to form an alkaline water environment in the anoxic pool, the acidic nitrogen-containing wastewater cannot undergo denitrification at low pH in the anoxic pool. For this reason, alkaline substances can be added to the pretreatment pool to neutralize the wastewater in the pretreatment pool. Once the anoxic pool starts to start, the denitrification reaction in the anoxic pool causes the alkalinity in the anoxic pool to rise. The sufficient alkalinity in the anoxic pool can neutralize the acidic nitrogen-containing wastewater, and at this time, it is no longer necessary to continue to add alkaline substances from the outside.

[0010] In some embodiments, the pH of the wastewater after neutralization in the pretreatment tank may be between 6 and 7.5.

[0011] According to this scheme, the wastewater entering the anoxic tank will not affect the activity of microorganisms in the anoxic tank, thereby not reducing the wastewater treatment capacity.

[0012] In some embodiments, the wastewater treatment system may be configured to stop adding alkaline substances to the pretreatment tank when the alkalinity of the wastewater in the anoxic tank is greater than 1000 mg / L.

[0013] According to this scheme, since the alkalinity of the wastewater in the anoxic tank is already large enough, introducing it back into the pretreatment tank is sufficient to neutralize the acidic wastewater in the pretreatment tank so that the wastewater meets the conditions for entering the anoxic tank.

[0014] In some embodiments, the alkaline substance can be sodium hydroxide.

[0015] In some embodiments, the SBR biochemical reactor may be provided with an integrated aerator, which is configured to remove bubbles attached to the activated sludge in the SBR biochemical reactor through aeration measures.

[0016] According to this scheme, the supersaturated nitrogen in the water formed by denitrification and the nitrogen bubbles attached to the activated sludge are quickly blown out of the SBR biochemical reactor through aeration treatment, so that the activated sludge settles faster, improving the decanting efficiency and effluent water quality.

[0017] In some embodiments, the SBR biochemical reactor may also be provided with a decanter, which is configured to prevent the activated sludge in the SBR biochemical reactor from flowing out of the SBR biochemical reactor.

[0018] According to the scheme, the loss of activated sludge in the SBR biochemical reactor, which would lead to a decrease in treatment performance, is prevented.

[0019] In some embodiments, the SBR biochemical reactor may also be provided with an online pH meter to measure the pH value of the wastewater in the SBR biochemical reactor in real time.

[0020] According to this scheme, the pH value of the wastewater in the SBR biochemical reactor can be adjusted in real time according to the pH value of the wastewater in the SBR biochemical reactor measured in real time by an online pH meter, so as to make it in a state that maximizes the activity of microorganisms in the SBR biochemical reactor.

[0021] In some embodiments, the wastewater treatment system may further include a post-treatment tank, which is arranged downstream of the anoxic tank to reduce the chemical oxygen demand of the wastewater.

[0022] According to this scheme, the water quality of the effluent can be further improved through a post-treatment tank.

[0023] In some schemes, the return pipe can be designed to allow alkaline wastewater less than or equal to 50% of the total amount of alkaline wastewater at the outlet of the anoxic tank to flow into the pretreatment tank via the return pipe.

[0024] In some aspects, the wastewater may be industrial wastewater generated from the production of adipic acid or any other nitrogen-containing acidic wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a wastewater treatment system according to an embodiment of the present utility model is shown.

[0026] Reference numerals:

[0027] 10 Wastewater treatment system

[0028] 12 Pretreatment tank

[0029] 14. Hypoxic Pool

[0030] 16 Return pipe

[0031] 18 Post-treatment pool DETAILED DESCRIPTION

[0032] In order to make the purpose, scheme and advantages of the technical solution of the utility model clearer, the technical solution of the embodiment of the utility model will be clearly and completely described in conjunction with the drawings of the specific embodiments of the utility model. Unless otherwise specified, the terms used in this article have the usual meanings in the art. The same reference numerals in the drawings represent the same components.

[0033] Figure 1 A schematic diagram of a wastewater treatment system 10 according to an embodiment of the present invention is shown. The wastewater treatment system 10 is arranged from upstream to downstream (ie, the flow direction of the wastewater, for example Figure 1 The anoxic tank 14 includes a pretreatment tank 12 and an anoxic tank 14 in sequence (from left to right in the figure). The anoxic tank 14 contains denitrifying bacteria, which can react with nitrate nitrogen (e.g., nitrate) to undergo a denitrification reaction to convert nitrate nitrogen that pollutes rivers and other environments into nitrogen gas that is non-polluting to the environment, so as to purify the wastewater. For acidic wastewater, because the activity of the microorganisms in the anoxic tank 14 will be reduced or even killed under acidic conditions, an alkaline water environment is required to neutralize the acidic wastewater (e.g., so that the pH value of the acidic wastewater is neutralized to between 6 and 7.5). The wastewater mentioned in the present utility model may be, for example, industrial wastewater from the production of adipic acid, but it should be understood that the present utility model is not intended to limit the specific components of the wastewater to be treated, and the wastewater to be treated may be any acidic wastewater suitable for microbial treatment.

[0034] In the prior art, for each batch of wastewater entering the pretreatment tank 12 from the upstream, it is necessary to add alkaline substances (e.g., sodium hydroxide) to neutralize the wastewater, which will consume a large amount of alkaline substances and thus greatly increase the cost of the wastewater treatment system. In the wastewater treatment system 10 according to the embodiment of the utility model, the anoxic tank 14 is an SBR biochemical reactor. The alkalinity generated by the denitrification reaction of each reaction batch in the SBR biochemical reactor 14 can be used to neutralize the acidic wastewater, and the acidic wastewater is neutralized in the alkalinity-rich water environment to meet the pH value required for the denitrification reaction. Compared to the traditional AO treatment technology, the alkaline wastewater generated by the denitrification reaction flows downstream and cannot effectively neutralize the acidic wastewater in the upstream. In the SBR biochemical reactor 14, the reagents can be fully mixed, so that the alkaline wastewater generated by the denitrification reaction effectively neutralizes the acidic wastewater entering the SBR biochemical reactor 14. In other words, the utility model changes the source of alkaline substances used to neutralize acidic wastewater in the prior art from the outside to the alkalinity generated by the denitrification reaction occurring in the SBR biochemical reactor 14, making full use of the alkaline wastewater generated by the denitrification action of the anoxic tank 14. While greatly reducing the cost caused by the external addition of alkaline substances, it also reduces the increase in the salt content of the effluent caused by the external addition of alkaline substances, thereby further improving the effluent water quality.

[0035] Preferably, a reflux pipe 16 is provided between the pretreatment tank 12 and the anoxic tank 14, and the reflux pipe 16 connects the outlet of the anoxic tank 14 to the pretreatment tank 12, so that the alkaline wastewater at the outlet of the anoxic tank 14 (preferably, alkaline wastewater less than or equal to 50% (for example, 30% or 40%) of the total amount of alkaline wastewater at the outlet of the anoxic tank 14) flows into the pretreatment tank 12 via the reflux pipe 16. By leading the alkaline wastewater at the outlet of the anoxic tank 14 back to the pretreatment tank 12, the wastewater in the pretreatment tank 12 is neutralized, and the consumption of alkaline substances in the wastewater treatment process is further reduced, thereby reducing the cost of operating the wastewater treatment system 10.

[0036] Preferably, the wastewater treatment system 10 can be configured to add alkaline substances to the pretreatment tank 12 only when the anoxic tank 14 is started for the first time. Before the anoxic tank 14 is started for the first time, since the denitrification reaction has not yet occurred in the anoxic tank 14 to make the wastewater alkaline, it is temporarily impossible to use the alkalinity generated by the denitrification reaction in the anoxic tank 14 to neutralize the acidic wastewater. For this reason, alkaline substances can be added to the pretreatment tank 12 to neutralize the wastewater in the pretreatment tank 12. Once the anoxic tank 14 starts to start, the denitrification reaction occurring in the anoxic tank 14 makes the anoxic tank 14 in an alkalinity-rich water environment, so that the acidic wastewater can be neutralized, and at this time, it is no longer necessary to continue to add alkaline substances from the outside.

[0037] It should be understood that, although the above scheme is similar to the prior art and also adds alkaline substances to the pretreatment tank 12 from the outside, the difference from the prior art is that: in the prior art, for each batch of wastewater entering the pretreatment tank 12 from the upstream, alkaline substances need to be added from the outside to neutralize the wastewater, while in the present invention, alkaline substances need to be added from the outside to the pretreatment tank 12 only when the anoxic tank 14 has not yet been started and before denitrification occurs fully, the specific reasons are as follows. Once denitrification has fully occurred in the anoxic tank 14, the alkalinity of the wastewater in the anoxic tank 14 can be high enough (for example, the alkalinity of the wastewater in the anoxic tank 14 is greater than 1000 mg / L), it is no longer necessary to add alkaline substances to the pretreatment tank 12 from the outside, and the alkaline wastewater in the anoxic tank 14 is used to neutralize the acidic wastewater in the pretreatment tank 12 instead.

[0038] In addition, because the SBR biochemical reactor is used as a separate denitrification tank, the activated sludge is domesticated in a long-term denitrification state under an anoxic environment, so compared with the conventional AO biochemical tank, the concentration of denitrifying bacteria is higher and the activity is better, so that the denitrification treatment efficiency is high, thereby improving the purification capacity of the wastewater treatment system 10. It should be understood that the present invention is not intended to limit the specific type of the anoxic tank 14, and the anoxic tank 14 can be any other suitable biochemical treatment tank for purifying nitrate nitrogen in wastewater through the denitrification of microorganisms.

[0039] Preferably, the SBR biochemical reactor 14 may be provided with an aeration machine (not shown), which is configured to remove bubbles attached to the activated sludge in the SBR biochemical reactor 14 through aeration measures. The supersaturated nitrogen in the water formed by denitrification and the nitrogen bubbles attached to the activated sludge are quickly blown out of the SBR biochemical reactor 14 through aeration treatment, so that the activated sludge settles faster, thereby improving the decanting efficiency and effluent water quality.

[0040] Preferably, the SBR biochemical reactor 14 may also be provided with a decanter (not shown), which is configured to block the activated sludge in the SBR biochemical reactor 14 from flowing out of the SBR biochemical reactor, thereby preventing the loss of activated sludge in the SBR biochemical reactor 14 and causing a decrease in the wastewater purification performance of the wastewater treatment system 10, thereby improving the effluent water quality.

[0041] Preferably, the SBR biochemical reactor 14 may also be provided with an online pH meter (not shown) to measure in real time the pH value of the wastewater in the SBR biochemical reactor 14. The pH value of the wastewater in the SBR biochemical reactor 14 may be adjusted in real time according to the pH value of the wastewater in the SBR biochemical reactor 14 measured in real time by the online pH meter, so that the pH value of the wastewater in the SBR biochemical reactor 14 is in a state where the microbial activity in the SBR biochemical reactor 14 is the highest, thereby further improving the wastewater treatment capacity of the wastewater treatment system 10.

[0042] Preferably, the wastewater treatment system 10 may further include a post-treatment tank 18 arranged downstream of the anoxic tank 14 to reduce the chemical oxygen demand of the wastewater. The post-treatment tank 18 can reduce the chemical oxygen demand of the wastewater, thereby further improving the water quality of the effluent.

[0043] This document describes in detail several exemplary embodiments of the present invention with reference to preferred embodiments. However, it will be understood by those skilled in the art that, without departing from the concept of the present invention, various modifications and variations may be made to the above-mentioned specific embodiments, and various technical features and structures proposed in the present invention may be combined without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A wastewater treatment system for treating nitrogen-containing acidic wastewater, characterized in that: From upstream to downstream, they include: A pretreatment tank, in which the wastewater undergoes a neutralization reaction to increase the pH value of the wastewater; an anoxic tank, in which the wastewater undergoes denitrification; Wherein, the anoxic tank is a SBR biochemical reactor.

2. The wastewater treatment system according to claim 1, characterized in that: The wastewater treatment system further comprises a reflux pipe, which connects the water outlet of the anoxic tank with the pretreatment tank, so that the alkaline wastewater at the water outlet of the anoxic tank flows into the pretreatment tank via the reflux pipe.

3. The wastewater treatment system according to claim 1, characterized in that: The wastewater treatment system is configured to add alkaline substances to the pretreatment tank only when the anoxic tank is started for the first time.

4. The wastewater treatment system according to claim 3, characterized in that: The pH value of the wastewater after neutralization in the pretreatment tank is between 6 and 7.

5.

5. The wastewater treatment system according to claim 3, characterized in that: The wastewater treatment system is configured to stop adding the alkaline substance to the pretreatment tank when the alkalinity of the wastewater in the anoxic tank is greater than 1000 mg / L.

6. The wastewater treatment system according to claim 3, characterized in that: The alkaline substance is sodium hydroxide.

7. The wastewater treatment system according to claim 6, characterized in that: The SBR biochemical reactor is provided with an integrated aeration machine, and the integrated aeration machine is configured to remove bubbles attached to the activated sludge in the SBR biochemical reactor through stirring and aeration measures.

8. The wastewater treatment system according to claim 6, characterized in that: The SBR biochemical reactor is also provided with a decanter, which is configured to block the outflow of activated sludge in the SBR biochemical reactor and collect water produced in each reaction batch.

9. The wastewater treatment system according to claim 6, characterized in that: The SBR biochemical reactor is also provided with an online pH meter to measure the pH value of the wastewater in the SBR biochemical reactor in real time.

10. The wastewater treatment system according to claim 2, characterized in that: The reflux pipe is designed to allow alkaline wastewater less than or equal to 50% of the total amount of alkaline wastewater at the outlet of the anoxic tank to flow into the pretreatment tank via the reflux pipe.

11. The wastewater treatment system according to claim 1, characterized in that: The wastewater is industrial wastewater generated by producing adipic acid.

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