CN111777291A - Treatment system for coal chemical wastewater - Google Patents

Abstract

This invention discloses a treatment system for coal chemical wastewater, comprising: a pre-denitrification zone, in which raw water enters and undergoes a denitrification reaction; a nitrification-decarbonization zone, in which a mixture from the pre-denitrification zone enters and undergoes a nitrification reaction; a first anaerobic zone, in which the mixture from the nitrification-decarbonization zone enters and undergoes simultaneous nitrification and denitrification, and a portion of the mixture from the first anaerobic zone is returned to the inlet of the pre-denitrification zone via a return pump; a post-denitrification zone, in which the remaining mixture from the first anaerobic zone enters and undergoes a denitrification reaction; a second anaerobic zone, in which the mixture from the post-denitrification zone enters and undergoes simultaneous nitrification and denitrification; and a secondary sedimentation tank, in which the mixture from the second anaerobic zone enters and undergoes sludge-water separation, and a portion of the bottom sludge is returned to the inlet of the pre-denitrification zone via a sludge return pump. The treatment system according to the present invention can improve the efficiency of pre-denitrification and post-denitrification, and reduce the carbon source consumed.

Description

Treatment system for coal chemical wastewater

technical field

The invention relates to the technical field of water treatment, in particular to a treatment system for coal chemical wastewater.

Background technique

In the production process of coal chemical industry, a large amount of waste water will be generated, mainly from the washing (coal gasification unit), condensation (coal gasification unit) and purification process (purification unit) of coal gas, among which the washing and condensate water of the coal gasification unit are the main ones. Wastewater has high water temperature, high suspended solids, high hardness, high ammonia nitrogen and a certain amount of organic matter, which cannot meet the needs of direct efflux and biochemical treatment. Generally, grey water treatment is carried out in the coal gasification unit area. The grey water treatment usually adopts the process of multi-stage flash evaporation and precipitation. After the treatment, most of the grey water is directly reused as the washing water of the washing tower, and a small part is discharged to the sewage treatment plant for treatment. The waste water volume is large, the water temperature is high, and the total nitrogen (with Ammonia nitrogen-based), high hardness and contains a certain amount of organic matter.

The existing treatment system for coal chemical wastewater is shown in Figure 1, including a pre-denitrification zone A1, a first aeration tank O1, a post-denitrification zone A2, a second aeration tank O2, and a degassing tank D. , the secondary sedimentation tank F, and the water from the first aeration tank O1 and the sludge from the secondary sedimentation tank F are partially returned to the inlet of the pre-denitrification zone A1.

The first aeration tank O1 is equipped with aerators to provide oxygen sources for nitrification and decarbonization reactions during the process of wastewater passing through the entire aeration tank channel, and at the same time, air agitation prevents biochemical sludge from precipitating during the flow process. In the actual operation process, the dissolved oxygen concentration at the outlet of O1 of the first aeration tank is higher than 2mg/l, and even reaches 3-4mg/l or higher, mainly because the concentration of pollutants in the influent is often lower than the design value, and the oxygen consumption However, it is caused by the fact that the actual aeration amount cannot be reduced to prevent sludge precipitation. The reflux ratio of the coal chemical wastewater mixture from the first aeration tank O1 to the inlet of the pre-denitrification zone A1 is high (500-600%), and the return of the nitrification solution containing a large amount of dissolved oxygen to the pre-denitrification zone A1 will reduce the Denitrification efficiency while consuming carbon source. After the high concentration of dissolved oxygen enters the post-denitrification zone A2, it will also affect the denitrification efficiency and consume carbon sources.

The second aeration tank O2 is also equipped with aerators in the whole tank, as the effluent of the post denitrification zone A2 to remove the excess carbon source added by A2. In the actual operation process, because there are few excess carbon sources, and aeration and stirring are necessary to prevent the precipitation of biochemical sludge, the actual effluent has a high dissolved oxygen content, and after the sludge is returned to the pre-denitrification zone A1, it is the same as the nitrification solution. The effect of pre-denitrification treatment.

Coal chemical wastewater contains a large amount of organic salts (such as formate, etc.) and organic nitrogen. The measured formate content of a project reaches 3000mg/l. Formate is easily degraded and releases a large amount of alkalinity during the degradation process. After the wastewater enters the traditional treatment system, the alkalinity of the water will increase rapidly, and the pH will also increase accordingly. Under the condition of high water temperature and partial alkalinity, a large amount of free ammonia will be produced , the nitrification was significantly inhibited, and the ammonia nitrogen concentration in the effluent of the secondary sedimentation tank deteriorated from less than 1mg/l to 18mg/l.

SUMMARY OF THE INVENTION

In view of the above problems, according to the first aspect of the present invention, a treatment system for coal chemical wastewater is proposed. The processing system includes:

In the pre-denitrification zone, the water to be treated enters the pre-denitrification zone and a denitrification reaction occurs. The pre-denitrification zone is provided with: an underwater agitator, which is configured to stir in the pre-denitrification zone; The carbon source addition point is configured to add carbon source to the pre-denitrification zone,

The nitrification and decarburization zone, where the mixed solution from the pre-denitrification zone enters the nitrification and decarburization zone for a nitrification reaction, and the nitrification and decarburization zone is provided with an aeration device for providing oxygen required for the reaction,

The first facultative oxygen zone, the mixed solution from the nitrification and decarburization zone enters the first facultative oxygen zone for simultaneous nitrification and denitrification,

In the post-denitrification zone, the remaining mixed solution from the first facultative oxygen zone enters the post-denitrification zone to have a denitrification reaction, and the post-denitrification zone is provided with: an underwater agitator, configured as Stirring is carried out in the post nitrification zone; the post carbon source addition point is configured to add carbon source to the post denitrification zone,

In the second facultative oxygen zone, the mixed solution from the post denitrification zone enters the second facultative oxygen zone for simultaneous nitrification and denitrification,

The secondary sedimentation tank, the mixed liquid from the second facultative oxygen zone enters the secondary sedimentation tank for mud-water separation, the separated clarified effluent is discharged to the downstream processing unit, and a part of the bottom sludge is returned to the front side through the sludge return pump At the entrance of the denitrification zone, the excess sludge is discharged to the subsequent sludge treatment unit through the excess sludge pump.

Compared with the conventional treatment system, the treatment system according to the first aspect of the present invention reduces the dissolved oxygen concentration of the mixed solution and improves the efficiency of the post-denitrification zone and the pre-denitrification zone due to the provision of the first facultative zone. Also, the carbon source consumed by the removal of dissolved oxygen can be reduced. In addition, due to the setting of the second facultative oxygen zone, the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank is reduced, and the efficiency of the pre-denitrification zone is improved after the sludge is returned to the pre-denitrification zone.

The treatment system for coal chemical wastewater according to the present invention may have one or more of the following features.

According to one embodiment, the thickness of the sludge bed of the secondary sedimentation tank is in the range of 1.5-2.5 m, so that denitrification reaction occurs in the sludge bed. The thickness range of the sludge bed makes the sludge at the bottom of the secondary sedimentation tank in a hydrolyzed state, so that the denitrification reaction can be carried out to remove part of the nitrate in the water, so as to further remove the total nitrogen of the wastewater, and the removal efficiency of the total nitrogen is also very high. high. The setting of the thickness of the sludge bed in the secondary sedimentation tank is coordinated with the setting of the second facultative oxygen zone. The specific performance is that, on the one hand, the second facultative oxygen zone reduces the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank, It is beneficial to realize the anaerobic hydrolysis of the sludge at the bottom of the secondary sedimentation tank; on the other hand, the carbon source required for the denitrification reaction in the sludge bed of the secondary sedimentation tank can come from the remaining carbon source in the upstream treatment or the secondary sedimentation. The available carbon source generated by the self-degradation of the sludge in the tank, the setting of the second facultative oxygen zone retains the remaining carbon source for the secondary sedimentation tank to a certain extent. In addition, since denitrification will generate nitrogen, in the general municipal sewage treatment process, the thickness of the sludge in the secondary sedimentation tank should not be too high, and the occurrence of denitrification should be avoided as much as possible, otherwise the production of too much nitrogen will cause the sludge to float. lead to poor water quality. However, due to the characteristics of coal chemical wastewater, its biochemical sludge has a large proportion, and a small amount of nitrate can be removed by denitrification in a secondary sedimentation tank, and the nitrogen generated will not cause sludge to float.

According to an embodiment, an online sludge level gauge is installed on the hanging bridge at 2/3 of the center of the secondary settling tank, and the thickness of the sludge bed in the secondary settling tank is controlled according to the data measured by the online sludge level gauge. , so that the sludge at the bottom of the secondary sedimentation tank is in a state of hydrolysis. Therefore, the sludge bed layer of the secondary sedimentation tank can be kept at a thickness that is favorable for denitrification reaction, and further removal of total nitrogen from wastewater can be promoted.

According to one embodiment, the pre-denitrification zone is further provided with: an acid dosing point configured to add acid to the pre-denitrification zone to adjust the pH of the pre-denitrification zone and neutralize organic acids The alkalinity generated by the decomposition of salt and organic nitrogen; and the phosphorus source dosing point, which is configured to add phosphorus source to the pre-denitrification zone. The setting of the acid addition point can control the pH of the treatment system within an appropriate range to ensure the normal operation of the subsequent nitrification and denitrification; the setting of the phosphorus source addition point can supplement the required phosphorus source.

According to one embodiment, the pre-denitrification zone is further provided with a pH probe and a redox potential probe, configured to monitor the pH and anoxic state of the pre-denitrification zone. As a result, the parameters of the processing system can be adjusted to be more efficient based on the measured values.

According to an embodiment, the nitrification and decarbonization zone is provided with an online dissolved oxygen analyzer configured to monitor the dissolved oxygen concentration of the nitrification and decarbonization zone online, and the oxygen supply of the aeration device is based on the monitored dissolved oxygen concentration to adjust. Thereby, the aeration device can be controlled efficiently and economically.

According to one embodiment, the post denitrification zone is provided with an online nitrate analyzer, configured to monitor the nitrate concentration of the post denitrification zone online, and the dose of the post carbon dosing point is monitored according to the adjusted for the nitrate concentration. According to the data of the online nitrate analyzer, the carbon source dosage is adjusted in a targeted manner to avoid adding too much carbon source.

According to one embodiment, the first anaerobic zone is provided with one or more first agitators for stirring and a first aeration device for supplying oxygen, and a part of the mixed liquid in the first anaerobic zone passes through a reflux pump Return to the inlet of the pre-denitrification zone; the second facultative zone is provided with one or more second agitators for stirring and a second aeration device for providing oxygen. The agitators and aeration devices provided in the first and second anaerobic zones enable the simultaneous nitrification and denitrification reactions occurring in the first and second anaerobic zones to be adjusted as required.

According to one embodiment, an online ammonia nitrogen analyzer is provided at the inlet of the first anaerobic zone, so that when the ammonia nitrogen concentration at the inlet of the first anaerobic zone is lower than the first set value, only the first agitator is operated, And when the ammonia nitrogen concentration at the inlet of the first facultative zone is higher than the first set value, the first agitator and the first aeration device are operated. By controlling the operation of the first agitator and the first aeration device, the online dissolved oxygen can be controlled at a lower concentration.

According to one embodiment, the first set value is 1-5 mg/l.

According to one embodiment, the outlet of the first anaerobic zone is provided with a first on-line dissolved oxygen analyzer, configured to monitor the dissolved oxygen concentration at the outlet of the first anaerobic zone online, and the first aeration device has an on-line dissolved oxygen analyzer. The oxygen supply is adjusted according to the monitored dissolved oxygen concentration and ammonia nitrogen concentration, and the dissolved oxygen concentration is controlled at 0.5-1 mg/l. Since the dissolved oxygen concentration of the first facultative zone is low, the dissolved oxygen concentration of the mixed solution returning to the pre-denitrification zone is also low, so it will not affect the denitrification reaction in the pre-denitrification zone, nor will it affect the post-denitrification zone. The denitrification reaction in the denitrification zone is placed, thereby improving the efficiency of the entire treatment system and reducing the consumption of carbon sources.

According to one embodiment, an online COD analyzer is provided at the inlet of the second anaerobic zone, so that when the COD concentration at the inlet of the second anaerobic zone is lower than the second set value, only the second agitator is operated, And when the COD concentration at the inlet of the second facultative zone is higher than the second set value, the second agitator and the second aeration device are operated. Thus, the state in the second facultative oxygen zone can be dynamically adjusted in real time, so as to achieve the purpose of removing total nitrogen by denitrification and removing excess carbon source in water by nitrification.

According to one embodiment, the second set value is 40-100 mg/l.

According to the second aspect of the present invention, a treatment system for coal chemical wastewater is also proposed, comprising:

In the pre-denitrification zone, the water to be treated enters the pre-denitrification zone and a denitrification reaction occurs. The pre-denitrification zone is provided with: an underwater agitator, which is configured to stir in the pre-denitrification zone; The carbon source addition point is configured to add carbon source to the pre-denitrification zone,

The nitrification and decarburization zone, where the mixed solution from the pre-denitrification zone enters the nitrification and decarburization zone for a nitrification reaction, and the nitrification and decarburization zone is provided with an aeration device for providing oxygen required for the reaction,

The post denitrification zone, the remaining mixed solution from the first facultative oxygen zone enters the post denitrification zone and a denitrification reaction occurs, and the post denitrification zone is provided with: an underwater agitator, configured as Stirring is carried out in the post nitrification zone; the post carbon source addition point is configured to add carbon source to the post denitrification zone,

The secondary sedimentation tank, the mixed liquid from the second facultative oxygen zone enters the secondary sedimentation tank for mud-water separation, the separated clarified effluent is discharged to the downstream processing unit, and a part of the bottom sludge is returned to the front side through the sludge return pump At the entrance of the denitrification zone, the excess sludge is discharged to the subsequent sludge treatment unit through the excess sludge pump, wherein the thickness of the sludge bed in the secondary sedimentation tank is in the range of 1.5-2.5m.

Compared with the conventional treatment system, the treatment system according to the second aspect of the present invention reduces the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank due to the removal of the second aeration tank, and returns to the pre-denitrification zone through the sludge After that, the efficiency of the pre-denitrification zone is improved. Moreover, the setting of the thickness of the sludge bed allows the sludge at the bottom of the secondary sedimentation tank to be in a hydrolyzed state, so that the denitrification reaction can be carried out to remove part of the nitrate in the water, so as to further remove the total nitrogen in the wastewater.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings of the embodiments of the present invention will be briefly introduced hereinafter. The accompanying drawings are only used to illustrate some embodiments of the present invention, but not to limit all the embodiments of the present invention thereto.

FIG. 1 is a schematic diagram of a conventional processing system.

2 is a schematic diagram of a treatment system for coal chemical wastewater according to the first embodiment of the present invention.

3 is a schematic diagram of the first facultative zone or the second anaerobic zone of the treatment system for coal chemical wastewater according to the present invention.

Fig. 4 is another schematic diagram of the first facultative zone or the second anaerobic zone of the treatment system for coal chemical wastewater according to the present invention.

FIG. 5 and FIG. 6 are respectively a comparison graph of a treatment system for coal chemical wastewater according to the first embodiment of the present invention and a conventional treatment system.

List of reference signs

A1 Pre-denitrification zone

O1 nitrification and decarbonization zone

C1 first facultative zone

A2 Post-denitrification zone

C2 second facultative zone

F Secondary sedimentation tank

P1 Mixed liquid return pump

P2 sludge return pump

P3 excess sludge pump

Q1 Raw water

Q2 reflux mixture

Q3 Return sludge

Detailed ways

In order to make the purpose, technical solutions and advantages of the technical solutions of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments of the present invention. The same reference numbers in the figures represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

Unless otherwise defined, technical or scientific terms used herein should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first", "second" and similar terms used in the description of the patent application and the claims of the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Likewise, words such as "a" or "an" do not necessarily imply a limitation of quantity. "Comprising" or "comprising" and similar words mean that the elements or things appearing before the word encompass the elements or things recited after the word and their equivalents, but do not exclude other elements or things. Words like "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", etc. are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

The present invention is described in detail below by way of describing example embodiments.

[First Embodiment]

As shown in FIG. 2 , the treatment system for coal chemical wastewater according to the first embodiment of the present invention includes a pre-denitrification zone A1, a nitrification and decarbonization zone O1, a first facultative oxygen zone C1, and a post-denitrification zone A2 , the second facultative oxygen zone C2, and the secondary sedimentation tank F. Among them, part of the mixed liquid in the first facultative zone C1 and part of the sludge in the secondary sedimentation tank F are returned to the inlet of the pre-denitrification zone A1. To this end, the treatment system further includes: a mixed solution return pump P1 and corresponding pipelines, so that the reflux mixed solution Q2 from the first facultative zone C1 is returned to the inlet of the pre-denitrification zone A1, and the mixed solution return pump P1 can It is an adjustable flow volumetric submersible pump controlled by frequency conversion; the sludge return pump P2 and the corresponding pipeline make the return sludge Q3 from the secondary sedimentation tank F return to the inlet of the pre-denitrification zone A1, and the sludge return pump P2 can be an adjustable flow positive displacement pump controlled by frequency conversion. Each zone is described in detail below.

Front denitrification zone A1

The raw water Q1, the reflux mixed liquid Q2 of the first facultative oxygen zone C1 and the reflux sludge Q3 of the secondary sedimentation tank F enter the pre-denitrification zone A1, and the denitrification reaction occurs by using the organic carbon source that can be quickly absorbed in the raw water. , remove organic matter and nitrate nitrogen from raw water.

In order to prevent sludge sedimentation, a mixing and stirring device, such as a submersible turbine mixer, is installed in the pre-denitrification zone A1 to ensure that the activated sludge in the pre-denitrification zone A1 is evenly mixed and suspended.

The pre-denitrification zone A1 can be provided with a carbon dosing point and a phosphorus dosing point, respectively, to supplement the phosphorus and carbon sources required for denitrification in the pre-denitrification zone A1. Specifically, methanol can be added at the carbon addition point, and phosphoric acid can be added at the phosphorus addition point. In addition, the pre-denitrification zone A1 can also be provided with an acid dosing point to neutralize the alkalinity generated by the decomposition of organic acid salts such as formate and organic nitrogen, and prevent a large amount of alkalinity generated by the decomposition of formate in the raw water from affecting the treatment. biochemical reactions of the system.

In order to monitor the biochemical operation of the treatment system, the pre-denitrification zone A1 can be equipped with a pH probe and an oxidation-reduction potential (ORP) probe. Based on the value measured by the ORP probe, it is possible to monitor whether denitrification has occurred. The acid dosing point can control the dosing amount of acid according to the pH value measured by the pH probe.

Nitrification and decarbonization zone O1

The mixed solution from the pre-denitrification zone A1 enters the nitrification and decarbonization zone O1 for nitrification to remove ammonia nitrogen and organic matter in the water.

The nitrification and decarbonization zone O1 is provided with an aeration device to provide the required oxygen for the aerobic zone. Due to the high hardness of this type of sewage, it is easy to cause scaling, and VIBRAIR vibrating mesoporous aerator can be used, which has high oxygen transport efficiency, low energy consumption, long service life and no risk of clogging.

In addition, the nitrification and decarbonization zone O1 can also be provided with a pH probe and an online dissolved oxygen analyzer. The nitrification reaction will cause the pH to drop, and the pH probe can be set to monitor the pH value and thus control the pH value not to exceed the range required for biochemistry. The dissolved oxygen online analyzer can be immersed and configured to monitor the dissolved oxygen concentration of O1 in the nitrification and decarbonization zone at any time. The oxygen supply of the aeration device can be adjusted according to the monitored dissolved oxygen concentration. The actual oxygen demand of oxidative nitrification can be adjusted, so as to ensure the smooth progress of nitrification and reduce costs.

The first facultative zone C1

The mixed liquid from the nitrification and decarburization zone O1 enters the first facultative oxygen zone C1, and by controlling the dissolved oxygen concentration, synchronous nitrification and denitrification are carried out to remove a small amount of ammonia nitrogen remaining in the water, and at the same time reduce the mixing back to the pre-denitrification zone A1. The dissolved oxygen concentration of the liquid.

The first facultative oxygen zone C1 can be in the form of an oxidation ditch, and is provided with one or more stirrers for stirring and an aeration device for supplying oxygen. By controlling the aeration amount of the aeration device, the dissolved oxygen in the first facultative zone C1 is controlled to a lower concentration (for example, 0.5-1 mg/l), and the dissolved oxygen is produced in the microbial flocs by the limitation of the diffusion of dissolved oxygen. Gradient, nitrification reaction occurs outside the activated sludge floc, and denitrification occurs inside the floc, so that the simultaneous treatment of ammonia nitrogen and nitrate nitrogen in the first facultative zone C1 treatment unit achieves simultaneous nitrification and denitrification. .

Specifically, as shown in FIG. 3 and FIG. 4 , an online ammonia nitrogen analyzer is provided at the inlet of the first anaerobic zone C1, and an online dissolved oxygen analyzer is provided at the outlet. When the ammonia nitrogen concentration at the inlet of the first anaerobic zone C1 measured by the online ammonia nitrogen analyzer is lower than the set value (for example, 1-5 mg/l), only the agitator is operated in the first anaerobic zone C1. When the inlet ammonia nitrogen concentration of zone C1 is higher than the set value, both the agitator and the aeration device are operated in the first facultative zone C1, and the online dissolved oxygen concentration is controlled at a lower concentration (for example, 0.5-1 mg/l), Thereby, simultaneous nitrification and denitrification are carried out to remove residual ammonia nitrogen. Figures 3 and 4 show the arrangement of the first anaerobic zone C1 or the second anaerobic zone C2, respectively. One or more agitators and one or more aeration zones can be provided in the anaerobic zone to achieve synchronization Nitrification and denitrification.

Since the dissolved oxygen concentration of the first facultative zone C1 is relatively low, the dissolved oxygen concentration of the mixed solution returning to the pre-denitrification zone A1 is also relatively low, so it will not affect the denitrification reaction of the pre-denitrification zone A1, nor It will affect the denitrification reaction of the post-denitrification zone A2, thereby improving the efficiency of the entire treatment system and reducing the consumption of carbon sources.

Post-denitrification zone A2

The remaining mixed solution from the first facultative oxygen zone O1 enters the post-denitrification zone A2 for denitrification reaction to remove the remaining nitrate nitrogen and reduce the total nitrogen in the effluent.

There is an agitator in the post-denitrification zone A2 to prevent sludge from settling. The post-denitrification zone A2 can also be provided with a carbon addition point to provide sufficient carbon source for the denitrification reaction. An online nitrate analyzer can be provided at the inlet of the post-denitrification zone A2. The dosage of carbon source is adjusted according to the influent flow, the sludge return flow and the nitrate concentration measured by the online nitrate analyzer. A pH meter may also be provided in the post-denitrification zone A2 to monitor the state of biochemical operation.

The second facultative zone C2

The mixed solution from the post-denitrification zone A2 enters the second facultative zone, and the second facultative zone C2 utilizes microorganisms to decompose themselves to generate organic matter as a carbon source, and further removes the post-deoxygenation by means of endogenous respiration and denitrification. Nitrate nitrogen in the effluent of nitrification zone A2. In addition, by monitoring the COD concentration of the effluent from the post-denitrification zone A2, in the case of excessive carbon source addition, the purpose of removing the excess carbon source is achieved by aeration. That is to say, simultaneous nitrification and denitrification can be performed in the second facultative zone C2.

As shown in Figures 3 and 4, the second anaerobic zone C2 may take the same form as the first anaerobic zone C1, provided with one or more stirrers for stirring and aeration means for supplying oxygen. By controlling the aeration amount of the aeration device, the dissolved oxygen in the first facultative oxygen zone C1 is controlled at a lower concentration (for example, 0.5-1 mg/l). Specifically, an on-line COD analyzer is provided at the inlet of the second oxygen compatible zone C2, and an on-line dissolved oxygen analyzer is provided at the outlet. When the COD concentration at the inlet of the second anaerobic zone C2 is lower than the set value (for example, 40-100 mg/l), only the agitator is operated in the second anaerobic zone C2 to perform endogenous respiration and denitrification to remove total nitrogen. When the COD concentration at the inlet of the second facultative oxygen zone C2 is higher than the set value, it means that the post denitrification zone A2 adds excessive carbon source, then the agitator and the aeration device are jointly operated in the second facultative oxygen zone to remove the water of excess carbon sources.

It is worth mentioning that, because the second facultative oxygen zone C2 is set before the secondary sedimentation tank F in the treatment system, not only the degassing tank is omitted, but also the dissolved oxygen concentration of the mixed liquid entering the secondary sedimentation tank F is lower, On the one hand, it ensures that the dissolved oxygen concentration of the sludge returned from the secondary sedimentation tank F is correspondingly low, which will not affect the denitrification reaction in the pre-denitrification zone A1. On the other hand, it is beneficial to the sludge bed itself of the secondary sedimentation tank. further denitrification.

Secondary Sedimentation Tank F

The mixed liquid from the second facultative oxygen zone C2 enters the secondary sedimentation tank F for mud-water separation. The separated clarified effluent is directed to the downstream processing unit. A part of the sludge at the bottom is returned to the inlet of the pre-denitrification zone A1 through the sludge return pump P2, mixed with the raw water, and plays the role of returning the sludge. The sludge return pump P2 controls the amount of the return sludge Q3 by setting the inverter. , after mixing the return sludge Q3 with the raw water, the sludge concentration is controlled within a suitable range of, for example, 3-5 g/l. The excess sludge is discharged to the subsequent sludge treatment unit through the excess sludge pump P3. The excess sludge pump P3 controls the sludge discharge flow through the set inverter, and is interlocked with the online sludge level gauge to control the thickness of the sludge bed.

The scraper drive device of the secondary sedimentation tank F controls the speed of the scraper bridge through the frequency converter, and the speed is controlled within the range of 4-8cm/s according to the different diameter of the tank, and the sludge is transported to the bottom of the tank through the bottom scraper and the sludge conduit. Center mud bucket.

Preferably, the purpose of denitrification can be achieved by controlling the thickness of the sludge bed in the secondary sedimentation tank F. Specifically, the secondary sedimentation tank F can install an online sludge level gauge on the hanging bridge at a distance of 2/3 from the center of the tank to monitor the thickness of the sludge bed online, and control the speed of the sludge scraper and/or the excess sludge pump by controlling the sludge level. P3 is the process of discharging sludge, so that the thickness of the sludge bed is kept in a suitable range, such as 1-2.5m, 1-2m, 1.5-2m, 1.5-2.5m, preferably 1.5-2.5m, to promote the sludge at the bottom In the state of hydrolysis, the activated sludge itself hydrolyzes to generate absorbable organic matter as a carbon source, which undergoes denitrification reaction with nitrate in the water to further remove total nitrogen from wastewater, and the removal efficiency of total nitrogen is also very high. The setting of the thickness of the sludge bed in the secondary sedimentation tank is coordinated with the setting of the second facultative oxygen zone. The specific performance is that, on the one hand, the second facultative oxygen zone reduces the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank, It is beneficial for the sludge at the bottom of the secondary sedimentation tank to achieve a hydrolyzed state; on the other hand, the carbon source required for the denitrification reaction in the sludge bed of the secondary sedimentation tank can come from the remaining carbon source in the upstream treatment or the secondary sedimentation tank sludge. The available carbon source generated by self-degradation, the setting of the second facultative oxygen zone retains the remaining carbon source for the secondary sedimentation tank to a certain extent. In addition, since denitrification will generate nitrogen, in the general municipal sewage treatment process, the thickness of the sludge in the secondary sedimentation tank should not be too high, and the occurrence of denitrification should be avoided as much as possible, otherwise the production of too much nitrogen will cause the sludge to float. lead to poor water quality. However, due to the characteristics of coal chemical wastewater, its biochemical sludge has a large proportion, and a small amount of nitrate can be removed by denitrification in a secondary sedimentation tank, and the nitrogen generated will not cause sludge to float.

The effect of the solution according to the present invention is further explained below by comparing the treatment system for coal chemical wastewater according to the first embodiment of the present invention with a conventional treatment system. Among them, the process flow of the conventional treatment system (comparison project) is shown in Figure 1, which is specifically: the pre-denitrification zone A1, the first aeration tank O1, the post-denitrification zone A2, the second aeration tank O2, the denitrification zone Gas tank D, secondary sedimentation tank F. The treatment system according to the present invention is shown in Fig. 2, and is specifically: a pre-denitrification zone A1, a nitrification and decarbonization zone O1, a first facultative oxygen zone C1, a post-denitrification zone A2, a second facultative oxygen zone C2, two Sedimentation Pond F.

As shown in Figure 5, it shows the data comparison between the post-denitrification zone A2 according to the present embodiment and the post-denitrification zone A2 according to the comparison project under the condition of adding the same amount of carbon source, it can be seen that, The dissolved oxygen concentration of the post-denitrification zone A2 according to the present embodiment is very low, which is significantly lower than the data of the post-denitrification zone A2 of the comparative project. Therefore, the formation of the post-denitrification zone A2 according to the present embodiment is more conducive to the formation of The anaerobic state of the denitrification reaction is carried out, thereby realizing a larger nitrate removal amount. As shown in Figure 5, the nitrate removal amount according to the post-denitrification zone A2 of the present embodiment is also significantly higher than that according to the comparison project. Nitrate removal in post-denitrification zone A2. The reason why the post-denitrification zone A2 according to the present embodiment can achieve such a low dissolved oxygen concentration is because the post-denitrification zone A2 is preceded by the first facultative oxygen zone C1, and the first facultative oxygen zone C1 according to the present embodiment Compared with the first aeration tank O1 according to the comparison project, it has a lower dissolved oxygen concentration, and then the dissolved oxygen concentration can also be lower after entering the post denitrification zone A2.

As shown in Fig. 6, it can be seen that the sludge thickness of the secondary sedimentation tank F according to the present invention is 1.5-2.5 m, while the sludge thickness of the secondary sedimentation tank of the conventional treatment system is 0.5-1.5 m. The difference between the nitrate inlet and outlet water of the secondary sedimentation tank F is 4 to 10 mg/l, while the nitrate inlet and outlet water difference of the secondary sedimentation tank of the conventional treatment system is 0 to 3 mg/l. It can be clearly seen that the secondary sedimentation tank F according to the present invention can effectively further remove nitrate, thereby further removing total nitrogen from wastewater, because the thicker sludge bed promotes the sludge at the bottom to be in a hydrolyzed state, and the activated sludge is in a state of hydrolysis. Self-hydrolysis produces organic matter that can be absorbed as a carbon source, and undergoes denitrification reaction with nitrate in water. In contrast, the nitrate removal in the secondary sedimentation tank of the conventional treatment system was not significant.

[Second Embodiment]

The treatment system for coal chemical wastewater according to the second embodiment of the present invention includes a pre-denitrification zone A1, a nitrification and decarbonization zone O1, a post-denitrification zone A2, and a secondary sedimentation tank F. The pre-denitrification zone A1, the nitrification and decarbonization zone O1, the post-denitrification zone A2, and the secondary sedimentation tank F according to the second embodiment are similar to those of the first embodiment, and their descriptions are omitted here. It should be noted that the thickness of the sludge bed in the secondary sedimentation tank F according to the second embodiment can be kept within a suitable range, such as 1-2.5m, 1-2m, 1.5-2m, 1.5-2.5m, preferably 1.5-2.5m, to promote the bottom sludge in a hydrolyzed state, the activated sludge itself hydrolyzes to produce absorbable organic matter as a carbon source, which undergoes denitrification reaction with nitrate in the water to further remove total nitrogen from wastewater. Moreover, compared with the conventional treatment system, due to the removal of the second aeration tank, the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank is reduced, and the pre-denitrification is improved after the sludge is returned to the pre-denitrification zone. District efficiency.

The exemplary embodiments of the treatment system for coal chemical wastewater proposed by the present invention have been described in detail above with reference to the preferred embodiments. However, those skilled in the art can understand that, without departing from the concept of the present invention, it is possible to Various variations and modifications can be made to the above-mentioned specific embodiments, and various technical features and structures proposed by the present invention can be combined in various ways without departing from the protection scope of the present invention.

Claims (12)

1. A treatment system for coal chemical wastewater, comprising: In the pre-denitrification zone, the water to be treated enters the pre-denitrification zone and a denitrification reaction occurs. The pre-denitrification zone is provided with: an underwater agitator, which is configured to stir in the pre-denitrification zone; The carbon source addition point is configured to add carbon source to the pre-denitrification zone, The nitrification and decarburization zone, where the mixed solution from the pre-denitrification zone enters the nitrification and decarburization zone for a nitrification reaction, and the nitrification and decarburization zone is provided with an aeration device for providing oxygen required for the reaction, The first facultative oxygen zone, the mixed solution from the nitrification and decarburization zone enters the first facultative oxygen zone for simultaneous nitrification and denitrification, In the post-denitrification zone, the remaining mixed solution from the first facultative oxygen zone enters the post-denitrification zone to have a denitrification reaction, and the post-denitrification zone is provided with: an underwater agitator, configured as Stirring is carried out in the post nitrification zone; the post carbon source addition point is configured to add carbon source to the post denitrification zone, In the second facultative zone, the mixed solution from the post-denitrification zone enters the second facultative zone for simultaneous nitrification and denitrification, The secondary sedimentation tank, the mixed liquid from the second facultative oxygen zone enters the secondary sedimentation tank for mud-water separation, the separated clarified effluent is discharged to the downstream processing unit, and a part of the bottom sludge is returned to the front side through the sludge return pump At the entrance of the denitrification zone, the excess sludge is discharged to the subsequent sludge treatment unit through the excess sludge pump. 2. The treatment system according to claim 1, wherein the thickness of the sludge bed of the secondary sedimentation tank is in the range of 1.5-2.5 m, so that denitrification reaction occurs in the sludge bed. 3. The treatment system according to claim 2, wherein the secondary sedimentation tank is installed with an online sludge level gauge on the hanging bridge at 2/3 of the center of the pool, and is controlled according to the data measured by the online sludge level gauge. The thickness of the sludge bed in the secondary sedimentation tank makes the sludge at the bottom of the secondary sedimentation tank in a state of hydrolysis. 4. The treatment system according to claim 1, wherein the pre-denitrification zone is further provided with: an acid addition point configured to add acid to the pre-denitrification zone to adjust the pre-denitrification zone. The pH of the nitrification zone neutralizes the alkalinity generated by the decomposition of organic acid salts and organic nitrogen; and the phosphorus source addition point, which is configured to add phosphorus source to the pre-denitrification zone. 5. The processing system of claim 1, Wherein, the pre-denitrification zone is also provided with a pH probe and a redox potential probe, configured to monitor the pH and anoxic state of the pre-denitrification zone, Wherein, the nitrification and decarbonization zone is provided with an online dissolved oxygen analyzer, which is configured to monitor the dissolved oxygen concentration of the nitrification and decarbonization zone online, and the oxygen supply of the aeration device is adjusted according to the monitored dissolved oxygen concentration, Wherein, the post denitrification zone is provided with an online nitrate analyzer, configured to monitor the nitrate concentration of the post denitrification zone online, and the dosage of the post carbon dosing point is based on the monitored nitrate concentration to adjust. 6. The treatment system according to any one of claims 1-5, wherein the first anaerobic zone is provided with one or more first agitators for stirring and a first aeration device for providing oxygen, A part of the mixed liquid in the first anaerobic zone is returned to the inlet of the pre-denitrification zone through a reflux pump; the second anaerobic zone is provided with one or more second stirrers for stirring and providing oxygen of the second aeration device. 7. The processing system according to claim 6, wherein the inlet of the first anaerobic zone is provided with an online ammonia nitrogen analyzer, so that when the ammonia nitrogen concentration of the inlet of the first anaerobic zone is lower than the first set value When , only the first agitator is operated, and when the ammonia nitrogen concentration at the inlet of the first facultative zone is higher than the first set value, the first agitator and the first aeration device are operated. 8. The processing system of claim 7, wherein the first set value is 1-5 mg/l. 9. The processing system according to claim 7, wherein the outlet of the first anaerobic zone is provided with a first on-line dissolved oxygen analyzer configured to monitor the dissolved oxygen concentration at the outlet of the first anaerobic zone on-line , the oxygen supply of the first aeration device is adjusted according to the monitored dissolved oxygen concentration and ammonia nitrogen concentration, and the dissolved oxygen concentration is controlled at 0.5-1 mg/l. 10. The processing system according to claim 6, wherein, the inlet of the second anaerobic zone is provided with an online COD analyzer, so that when the COD concentration of the inlet of the second anaerobic zone is lower than the second set value , only the second agitator is operated, and when the COD concentration at the inlet of the second facultative zone is higher than the second set value, the second agitator and the second aeration device are operated. 11. The processing system of claim 10, wherein the second set value is 40-100 mg/l. 12. A treatment system for coal chemical wastewater, comprising: In the denitrification zone, the water to be treated enters the denitrification zone and undergoes a denitrification reaction. The nitrification and decarburization zone, where the mixed solution from the pre-denitrification zone enters the nitrification and decarburization zone for a nitrification reaction, and the nitrification and decarburization zone is provided with an aeration device for providing oxygen required for the reaction, The secondary sedimentation tank, the mixed liquid from the second facultative oxygen zone enters the secondary sedimentation tank for mud-water separation, the separated clarified effluent is discharged to the downstream processing unit, and a part of the bottom sludge is returned to the front side through the sludge return pump At the entrance of the denitrification zone, the excess sludge is discharged to the subsequent sludge treatment unit through the excess sludge pump, wherein the thickness of the sludge bed in the secondary sedimentation tank is in the range of 1.5-2.5m.

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