CN111777291A - Treatment system for coal chemical industry wastewater - Google Patents

Treatment system for coal chemical industry wastewater Download PDF

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Publication number
CN111777291A
CN111777291A CN202010787787.6A CN202010787787A CN111777291A CN 111777291 A CN111777291 A CN 111777291A CN 202010787787 A CN202010787787 A CN 202010787787A CN 111777291 A CN111777291 A CN 111777291A
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China
Prior art keywords
denitrification
zone
sludge
facultative
area
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CN202010787787.6A
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Inventor
寇光辉
郑斌
周夏海
张志峰
朱先富
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Suez Water Engineering Co ltd
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Suez Water Engineering Co ltd
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Priority to CN202010787787.6A priority Critical patent/CN111777291A/en
Publication of CN111777291A publication Critical patent/CN111777291A/en
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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00Biological treatment of water, waste water, or sewage
    • C02F3/30Aerobic and anaerobic processes
    • C02F3/302Nitrification and denitrification treatment
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F2001/007Processes including a sedimentation step
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/30Organic compounds
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/30Organic compounds
    • C02F2101/38Organic compounds containing nitrogen

Abstract

The invention discloses a treatment system for coal chemical industry wastewater, which comprises: the raw water enters the preposed denitrification area to carry out denitrification reaction; the mixed liquid from the preposed denitrification area enters the nitrification and decarbonization area to carry out nitrification reaction; the mixed liquid from the nitrification and decarbonization zone enters the first facultative zone to carry out synchronous nitrification and denitrification, and one part of the mixed liquid in the first facultative zone reflows to the inlet of the preposed denitrification zone through a reflux pump; the residual mixed liquid from the first facultative denitrification area enters the post-denitrification area to carry out denitrification reaction; the mixed liquid from the post denitrification zone enters the second facultative denitrification zone to carry out synchronous nitrification and denitrification; and the mixed liquid from the second facultative anaerobic zone enters the secondary sedimentation tank for sludge-water separation, and part of sludge at the bottom returns to the inlet of the preposed denitrification zone through a sludge reflux pump. The treatment system can improve the efficiency of pre-denitrification and post-denitrification and reduce the consumed carbon source.

Description

Treatment system for coal chemical industry wastewater
Technical Field
The invention relates to the technical field of water treatment, in particular to a treatment system for coal chemical industry wastewater.
Background
In the coal chemical industry, a large amount of wastewater is generated in the production process and mainly generated in the coal gas washing (coal gasification unit), condensation (coal gasification unit) and purification processes (purification unit), wherein the washing and condensation water of the coal gasification unit is mainly used, the wastewater is high in water temperature, high in suspended matter, high in hardness and high in ammonia nitrogen and contains a certain amount of organic matters, the requirements of direct discharge and biochemical treatment cannot be met, and the ash water treatment is generally carried out in a coal gasification device area. The grey water treatment usually adopts a multi-stage flash evaporation and precipitation process, most of the treated grey water is directly reused as washing water of a washing tower, a small part of the treated grey water is discharged to a sewage treatment plant for treatment, and the treated grey water has large water volume, high water temperature, high total nitrogen (mainly ammonia nitrogen), high hardness and a certain amount of organic matters.
The existing treatment system for coal chemical industry wastewater is shown in fig. 1, and comprises a preposed denitrification area A1, a first aeration tank O1, a postposition denitrification area A2, a second aeration tank O2, a degassing tank D and a secondary sedimentation tank F, wherein water from the first aeration tank O1 and sludge from the secondary sedimentation tank F partially flow back to an inlet of the preposed denitrification area A1.
The first aeration tank O1 is provided with an aerator in the whole tank, which provides oxygen source for nitrification reaction and decarbonization reaction during the process of wastewater passing through the whole aeration tank channel, and prevents biochemical sludge from depositing in the flowing process through air agitation. In the actual operation process, the dissolved oxygen concentration at the outlet of the first aeration tank O1 is higher than 2mg/l, even reaches 3-4mg/l or higher, mainly due to the fact that the concentration of the inlet water pollutants is often lower than the designed value, the oxygen consumption is low, but the actual aeration quantity for preventing sludge precipitation cannot be reduced. The reflux ratio of the mixed liquid of the coal chemical wastewater returned from the first aeration tank O1 to the inlet of the preposed denitrification area A1 is high (600 percent in 500 percent), and the return of the nitrified liquid containing a large amount of dissolved oxygen to the preposed denitrification area A1 reduces the denitrification efficiency and consumes carbon sources. High concentrations of dissolved oxygen entering the post denitrification zone A2 also affect denitrification efficiency and carbon source consumption.
The second aeration tank O2 is also provided with an aerator in the whole tank to be used as the water outlet of the postposition denitrification zone A2 to remove the excess carbon source added by A2. In the actual operation process, because the surplus carbon source is less, aeration stirring is required for preventing biochemical sludge precipitation, the dissolved oxygen content of the actual effluent is high, and the actual effluent flows back to the preposed denitrification area A1 through the sludge and then flows back to the same way as the nitrifying liquid, so that the preposed denitrification treatment effect is influenced.
The coal chemical industry wastewater contains a large amount of organic acid salt (such as formate and the like) and organic nitrogen, and the content of formate actually measured in a certain project reaches 3000 mg/l. The formate is easy to degrade, a large amount of alkalinity is released in the degradation process, after wastewater enters a traditional treatment system, the alkalinity in water can be rapidly increased, the pH value is correspondingly increased, a large amount of free ammonia can be generated under the conditions of high water temperature and partial alkalinity, the nitrification can be obviously inhibited, and the ammonia nitrogen concentration of effluent water of a secondary sedimentation tank is maximally deteriorated to 18mg/l from less than 1 mg/l.
Disclosure of Invention
In view of the above problems, according to a first aspect of the present invention, a treatment system for wastewater of coal chemical industry is provided. The processing system comprises:
the water to be treated enters the preposed denitrification area to carry out denitrification reaction, and the preposed denitrification area is provided with: an underwater agitator configured to agitate within the pre-denitrification zone; a preposed carbon source adding point which is configured to add a carbon source to the preposed denitrification area,
a nitrification and decarbonization area, wherein the mixed liquid from the preposed denitrification area enters the nitrification and decarbonization area to carry out nitrification reaction, the nitrification and decarbonization area is provided with an aeration device which is required for providing oxygen for the reaction,
a first facultative zone, the mixed liquor from the nitrification and decarbonization zone enters the first facultative zone to carry out synchronous nitrification and denitrification,
the post-denitrification area is used for allowing the residual mixed liquor from the first facultative anoxic area to enter the post-denitrification area for denitrification reaction, and is provided with: an underwater agitator configured to agitate in the post-nitrification zone; a post carbon source feeding point which is configured to feed a carbon source into the post denitrification area,
the mixed liquid from the post-denitrification zone enters the second facultative denitrification zone for synchronous nitrification and denitrification,
and the mixed liquid from the second facultative anaerobic zone enters the secondary sedimentation tank for sludge-water separation, the separated clarified effluent is discharged to a downstream processing unit, a part of sludge at the bottom returns to the inlet of the preposed denitrification zone through a sludge return pump, and the residual sludge is discharged to a subsequent sludge processing unit through a residual sludge pump.
Compared with the conventional treatment system, the treatment system provided by the first aspect of the invention has the advantages that the concentration of dissolved oxygen in the mixed liquor is reduced due to the arrangement of the first facultative zone, the efficiency of the post-denitrification zone and the pre-denitrification zone is improved, and carbon sources consumed by removing the dissolved oxygen can be reduced. In addition, the second facultative area is arranged, so that the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank is reduced, and the efficiency of the preposed denitrification area is improved after the sludge flows back to the preposed denitrification area.
The treatment system for coal chemical industry wastewater according to the present invention may have one or more of the following features.
According to one embodiment, the sludge bed thickness of the secondary sedimentation tank is in the range of 1.5-2.5m, so that denitrification reactions occur in the sludge bed. The thickness range of the sludge bed layer enables the sludge at the bottom of the secondary sedimentation tank to be in a hydrolysis state, so that denitrification reaction can be carried out to remove partial nitrate in water, the purpose of further removing the total nitrogen in the wastewater is achieved, and the total nitrogen removal efficiency is very high. The setting of the thickness of the sludge bed layer of the secondary sedimentation tank is matched with the setting of the second facultative zone, and the concrete expression is that, on one hand, the second facultative zone reduces the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank, thereby being beneficial to realizing the anaerobic hydrolysis state of the sludge at the bottom of the secondary sedimentation tank; on the other hand, the carbon source required by denitrification reaction in the sludge bed layer of the secondary sedimentation tank can be from the surplus carbon source processed at the upstream or the available carbon source generated by self degradation of the sludge in the secondary sedimentation tank, and the second facultative anaerobic zone is arranged to reserve the surplus carbon source for the secondary sedimentation tank to a certain extent. In addition, because denitrification can generate nitrogen, in a general municipal sewage treatment process, the thickness of sludge in a secondary sedimentation tank cannot be too high, the denitrification action needs to be avoided as much as possible, otherwise, excessive nitrogen is generated to cause the sludge to float upwards, and the quality of effluent water is poor. But due to the characteristics of the coal chemical wastewater, the biochemical sludge has high specific gravity, a secondary sedimentation tank can be used for carrying out denitrification reaction to remove a small part of nitrate, and the generated nitrogen does not float upwards.
According to one embodiment, the secondary sedimentation tank is provided with an online sludge level meter on the hanging bridge from the center 2/3 of the tank, and the thickness of a sludge bed layer of the secondary sedimentation tank is controlled according to data measured by the online sludge level meter, so that sludge at the bottom of the secondary sedimentation tank is in a hydrolysis state. Therefore, the sludge bed layer of the secondary sedimentation tank can be always kept at the thickness favorable for carrying out denitrification reaction, and the further removal of the total nitrogen in the wastewater is promoted.
According to one embodiment, the pre-denitrification zone is further provided with: an acid adding point, configured to add acid to the pre-denitrification region to adjust the pH value of the pre-denitrification region and neutralize the pH value generated by decomposition of organic acid salt and organic nitrogen; and a phosphorus source feeding point configured to feed a phosphorus source to the pre-denitrification region. The acid adding point can control the pH value of the treatment system in a proper range, so that the normal operation of the subsequent nitrification and denitrification is ensured; the phosphorus source feeding point can be set to supplement the required phosphorus source.
According to one embodiment, the pre-denitrification region is further provided with a pH probe and an oxidation-reduction potential probe configured to monitor the pH value and the anoxic state of the pre-denitrification region. Thus, the parameters of the processing system can be adjusted according to the measured values, making it more efficient.
According to one embodiment, the nitrification and decarbonization zone is provided with an online dissolved oxygen analyzer configured to online monitor the dissolved oxygen concentration of the nitrification and decarbonization zone, and the oxygen supply amount of the aeration device is adjusted according to the monitored dissolved oxygen concentration. Thus, the aeration apparatus can be efficiently and economically controlled.
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 dosage of the post-carbon addition point is adjusted according to the monitored nitrate concentration. According to the data of the on-line nitrate analyzer, the carbon source adding is adjusted in a targeted manner so as to avoid adding excessive carbon source.
According to one embodiment, the first facultative zone is provided with one or more first stirrers for stirring and a first aeration device for providing oxygen, and a part of the mixed liquor in the first facultative zone is refluxed to the inlet of the pre-denitrification zone by a reflux pump; the second facultative zone is provided with one or more second stirrers for stirring and a second aeration device for providing oxygen. The agitators and the aeration devices arranged in the first facultative zone and the second facultative zone enable the synchronous nitrification and denitrification reactions occurring in the first facultative zone and the second facultative zone to be adjusted as required.
According to one embodiment, the inlet of the first facultative zone is provided with an on-line ammonia nitrogen analyzer, so that when the ammonia nitrogen concentration of the inlet of the first facultative zone is lower than a first set value, only the first stirrer is operated, and when the ammonia nitrogen concentration of the inlet of the first facultative zone is higher than the first set value, the first stirrer and the first aeration device are operated. By controlling the operation of the first stirrer and the first aeration device, it is possible to control the on-line dissolved oxygen at a lower concentration.
According to one embodiment, said first set value is between 1 and 5 mg/l.
According to one embodiment, the outlet of the first facultative zone is provided with a first online dissolved oxygen analyzer configured to online monitor the dissolved oxygen concentration at the outlet of the first facultative zone, the oxygen supply amount of the first aeration apparatus is adjusted according to the monitored dissolved oxygen concentration and ammonia nitrogen concentration, and the dissolved oxygen concentration is controlled to be 0.5-1 mg/l. Because the dissolved oxygen concentration of the first facultative denitrification zone is lower, the dissolved oxygen concentration of the mixed liquid which flows back to the preposed denitrification zone is also lower, the denitrification reaction of the preposed denitrification zone is not influenced, and the denitrification reaction of the post denitrification zone is not influenced, thereby improving the efficiency of the whole treatment system and reducing the consumed carbon source.
According to one embodiment, the inlet of the second facultative zone is provided with an on-line COD analyzer, such that when the COD concentration of the inlet of the second facultative zone is lower than a second set value, only the second stirrer is operated, and when the COD concentration of the inlet of the second facultative zone is higher than the second set value, the second stirrer and the second aeration device are operated. Therefore, the state in the second facultative area can be dynamically adjusted in real time, and the purposes of removing total nitrogen by denitrification and removing excess carbon sources in water by nitrification are achieved.
According to one embodiment, said second set value is between 40 and 100 mg/l.
According to the second aspect of the present invention, there is also provided a treatment system for coal chemical industry wastewater, comprising:
the water to be treated enters the preposed denitrification area to carry out denitrification reaction, and the preposed denitrification area is provided with: an underwater agitator configured to agitate within the pre-denitrification zone; a preposed carbon source adding point which is configured to add a carbon source to the preposed denitrification area,
a nitrification and decarbonization area, wherein the mixed liquid from the preposed denitrification area enters the nitrification and decarbonization area to carry out nitrification reaction, the nitrification and decarbonization area is provided with an aeration device which is required for providing oxygen for the reaction,
the post-denitrification area is used for allowing the residual mixed liquor from the first facultative anoxic area to enter the post-denitrification area for denitrification reaction, and is provided with: an underwater agitator configured to agitate in the post-nitrification zone; a post carbon source feeding point which is configured to feed a carbon source into the post denitrification area,
and the mixed liquid from the second facultative anaerobic zone enters the secondary sedimentation tank for sludge-water separation, the separated clarified effluent is discharged to a downstream processing unit, part of the bottom sludge flows back to the inlet of the preposed denitrification zone through a sludge reflux pump, and the residual sludge is discharged to a subsequent sludge processing unit through a residual sludge pump, wherein the thickness of a sludge bed layer of the secondary sedimentation tank is within the range of 1.5-2.5 m.
Compared with the conventional treatment system, the treatment system of the second aspect of the invention reduces the dissolved oxygen concentration of the mixed liquor flowing to the secondary sedimentation tank due to the elimination of the second aeration tank, and improves the efficiency of the pre-denitrification zone after the sludge flows back to the pre-denitrification zone. And the sludge bed layer thickness is set to ensure that the sludge at the bottom of the secondary sedimentation tank can be in a hydrolysis state, so that denitrification reaction can be carried out to remove partial nitrate in water, and the aim of further removing the total nitrogen in the wastewater is fulfilled.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly described below. Wherein the drawings are only for purposes of illustrating some embodiments of the invention and are not to be construed as limiting the invention to all embodiments thereof.
FIG. 1 is a schematic diagram of a prior art processing system.
Fig. 2 is a schematic view of a treatment system for coal chemical industry wastewater according to a first embodiment of the present invention.
Fig. 3 is a schematic view of the first facultative zone or the second facultative zone of the treatment system for coal chemical industry wastewater according to the invention.
Fig. 4 is another schematic view of the first facultative zone or the second facultative zone of the treatment system for coal chemical industry wastewater according to the invention.
Fig. 5 and 6 are graphs comparing a treatment system for coal chemical industry wastewater according to a first embodiment of the present invention with a conventional treatment system, respectively.
List of reference numerals
A1 preposed denitrification zone
O1 nitration decarbonization zone
C1 first facultative zone
A2 postposition denitrification zone
C2 second facultative zone
F secondary sedimentation tank
P1 mixed liquid reflux pump
P2 sludge recirculation pump
P3 excess sludge pump
Q1 raw Water
Q2 refluxing the mixture
Q3 return sludge
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments 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 specific embodiments of the present invention. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
The present invention is described in detail below by way of describing example embodiments.
[ first embodiment ] A method for manufacturing a semiconductor device
As shown in fig. 2, the treatment system for coal chemical industry wastewater according to the first embodiment of the present invention includes a pre-denitrification zone a1, a nitrification-decarbonization zone O1, a first facultative zone C1, a post-denitrification zone a2, a second facultative zone C2, and a secondary sedimentation tank F. Wherein part of the mixed liquor in the first facultative zone C1 and part of the sludge in the secondary sedimentation tank F return to the inlet of the preposed denitrification zone A1. To this end, the processing system further comprises: a mixed liquid reflux pump P1 and corresponding pipelines, so that the reflux mixed liquid Q2 from the first facultative anaerobic zone C1 reflows to the inlet of the preposed denitrification zone A1, and the mixed liquid reflux pump P1 can be a variable-frequency control adjustable-flow volume type submersible pump; a sludge return pump P2 and a corresponding pipeline, so that returned sludge Q3 from the secondary sedimentation tank F returns to the inlet of the preposed denitrification area A1, and the sludge return pump P2 can be a variable-frequency control variable-flow positive displacement pump. Each zone will be described in detail below.
Front denitrification zone A1
Raw water Q1, reflux mixed liquor Q2 of the first facultative zone C1 and reflux sludge Q3 of the secondary sedimentation tank F enter a preposed denitrification zone A1, and organic matters and nitrate nitrogen in the raw water are removed by carrying out denitrification reaction by utilizing an organic carbon source which can be quickly absorbed in the raw water.
In order to prevent the sludge from settling, a mixing and stirring device, such as a submersible turbine type stirrer, is arranged in the preposed denitrification area A1 to ensure that the activated sludge in the preposed denitrification area A1 is uniformly mixed and is in a suspension state.
The preposed denitrification area A1 can be provided with a carbon adding point and a phosphorus adding point, and respectively supplements phosphorus source and carbon source required by denitrification of the preposed denitrification area A1. Specifically, methanol can be added to the carbon adding point, and phosphoric acid can be added to the phosphorus adding point. In addition, the preposed denitrification area A1 can be provided with an acid adding point to neutralize the alkalinity generated by the decomposition of organic acid salts such as formate and organic nitrogen and prevent a great deal of alkalinity generated by the decomposition of formate in the raw water from influencing the biochemical reaction of the treatment system.
To monitor the biochemical operation of the treatment system, the pre-denitrification zone a1 may be equipped with a pH probe and an Oxidation Reduction Potential (ORP) probe to monitor the anoxic state of the reaction zone of the pre-denitrification zone a1 via pH and ORP. According to the value measured by the ORP probe, whether the denitrification reaction occurs can be monitored. The acid adding point can control the adding amount of acid according to the pH value measured by the pH probe.
Nitration decarbonization zone O1
The mixed liquid from the preposed denitrification area A1 enters a nitrification and decarbonization area O1 to carry out nitrification reaction, and ammonia nitrogen and organic matters in the water are removed.
The nitrification and decarbonization zone O1 is provided with an aeration device to provide the required oxygen for the aerobic zone. Because the sewage has higher hardness and is easy to cause scaling, the VIBRAIR vibration type mesopore aerator can be adopted, and has high oxygen conveying efficiency, low energy consumption, long service life and no blocking risk.
In addition, the nitrification and decarbonization zone O1 can also be provided with a pH probe and a dissolved oxygen on-line analyzer. The nitration reaction will cause the pH to drop and the pH probe can be set to monitor the pH and thereby control the pH not to exceed the biochemically required range. The dissolved oxygen on-line analyzer can be immersed and is configured to monitor the dissolved oxygen concentration of the nitrification and decarbonization zone O1 at any time, and the oxygen supply amount of the aeration device can be adjusted according to the monitored dissolved oxygen concentration, namely, the oxygen supply amount can be adjusted according to the actual oxygen demand of carbon oxidation and nitrification, so that the smooth proceeding of nitrification and denitrification can be ensured, and the cost can be reduced.
The first facultative zone C1
And the mixed liquor from the nitrification and decarbonization zone O1 enters a first facultative zone C1, and synchronous nitrification and denitrification are carried out by controlling the concentration of dissolved oxygen so as to remove a small amount of residual ammonia nitrogen in water and simultaneously reduce the concentration of the dissolved oxygen of the mixed liquor flowing back to the preposed denitrification zone A1.
The first facultative zone C1 may take the form of an oxidation ditch provided with one or more agitators for agitation and an aeration means for providing oxygen. Dissolved oxygen in the first facultative zone C1 is controlled to be low in concentration (for example, 0.5-1mg/l) by controlling the aeration quantity of the aeration device, dissolved oxygen gradient is generated in the microbial flocs by utilizing the limitation of the diffusion effect of the dissolved oxygen, nitrification reaction is generated outside the activated sludge flocs, denitrification is generated inside the flocs, and therefore the effect of simultaneously treating ammonia nitrogen and nitrate nitrogen is achieved in the treatment unit of the first facultative zone C1, and synchronous nitrification and denitrification are realized.
Specifically, as shown in fig. 3 and 4, an on-line ammonia nitrogen analyzer is provided at the inlet of the first facultative zone C1, and an on-line dissolved oxygen analyzer is provided at the outlet. When the ammonia nitrogen concentration at the inlet of the first facultative zone C1 is lower than a set value (such as 1-5mg/l) measured by an online ammonia nitrogen analyzer, only operating a stirrer in the first facultative zone C1, and when the ammonia nitrogen concentration at the inlet of the first facultative zone C1 is higher than the set value, operating both the stirrer and an aerator in the first facultative zone C1 to control the online dissolved oxygen concentration at a lower concentration (such as 0.5-1mg/l), thereby carrying out synchronous nitrification and denitrification to remove residual ammonia nitrogen. Fig. 3 and 4 show the arrangement of the first facultative zone C1 or the second facultative zone C2, respectively, in which one or more agitators, and one or more aeration zones, may be provided to achieve simultaneous nitrification and denitrification.
Because the dissolved oxygen concentration of the first facultative denitrification zone C1 is lower, the dissolved oxygen concentration of the mixed liquid flowing back to the preposed denitrification zone A1 is also lower, the denitrification reaction of the preposed denitrification zone A1 is not influenced, and the denitrification reaction of the postposition denitrification zone A2 is not influenced, thereby improving the efficiency of the whole treatment system and reducing the consumed carbon source.
Postposition denitrification zone A2
The residual mixed liquid from the first facultative denitrification area O1 enters a post-denitrification area A2 to carry out denitrification reaction, remove residual nitrate nitrogen and reduce the total nitrogen of effluent.
An agitator is arranged in the postposition denitrification area A2 to prevent sludge from settling. The post-denitrification area A2 can also be provided with a carbon feeding point to provide enough carbon source for denitrification reaction. An on-line nitrate analyzer may be provided at the inlet of the post-denitrification zone A2. The adding amount of the carbon source is adjusted according to the water inlet flow, the sludge reflux amount and the nitrate concentration measured by an online nitrate analyzer. The postposition denitrification area A2 can be also provided with a pH meter for monitoring the state of biochemical operation.
Second facultative zone C2
The mixed liquor from the post-denitrification area A2 enters the second facultative zone, the second facultative zone C2 utilizes organic matters generated by the self decomposition of microorganisms as a carbon source, and nitrate nitrogen in the effluent of the post-denitrification area A2 is further removed in an endogenous respiration denitrification mode. In addition, by monitoring the COD concentration of the water discharged from the post-denitrification area A2, the purpose of removing the excessive carbon source is achieved by aeration under the condition of excessive carbon source addition. That is, the simultaneous nitrification and denitrification can be performed in the second facultative zone C2.
As shown in fig. 3 and 4, the second facultative zone C2 may take the same form as the first facultative zone C1, provided with one or more agitators for agitation and an aeration device for supplying oxygen. The dissolved oxygen in the first facultative zone C1 is controlled to a low concentration (e.g., 0.5-1mg/l) by controlling the aeration amount of the aeration means. Specifically, an on-line COD analyzer is provided at the inlet of the second facultative zone C2, and an on-line dissolved oxygen analyzer is provided at the outlet. When the COD concentration at the inlet of the second facultative zone C2 is lower than the set value (for example, 40-100mg/l), only the stirrer is operated in the second facultative zone C2, so that the endogenous respiration denitrification is carried out to remove the total nitrogen. When the COD concentration at the inlet of the second facultative zone C2 is higher than a set value, which means that the added carbon source in the postposition denitrification zone A2 is excessive, the stirrer and the aeration device are operated together in the second facultative zone to remove the excessive added carbon source in the water.
It is worth proposing that, because the second facultative zone C2 is arranged in the treatment system before the secondary sedimentation tank F, the degassing tank is omitted, and the dissolved oxygen concentration of the mixed liquid entering the secondary sedimentation tank F is lower, on one hand, the dissolved oxygen concentration of the sludge reflowing from the secondary sedimentation tank F is correspondingly lower, the denitrification reaction of the preposed denitrification zone A1 is not influenced, and on the other hand, the sludge bed layer of the secondary sedimentation tank is beneficial to further denitrification.
Two heavy ponds F
The mixed liquid from the second facultative zone C2 enters a secondary sedimentation tank F for sludge-water separation. The separated clear effluent is led out to a downstream processing unit. A part of bottom sludge is returned to the inlet of the preposed denitrification area A1 through a sludge return pump P2 to be mixed with raw water to play a role of returning sludge, and the sludge return pump P2 is provided with a frequency converter to control the amount of returned sludge Q3, so that after the returned sludge Q3 is mixed with the raw water, the sludge concentration is controlled within a proper range of 3-5 g/l. Excess sludge is discharged to a subsequent sludge treatment unit through an excess sludge pump P3, and the excess sludge pump P3 controls the sludge discharge flow through a frequency converter, and is interlocked with an online sludge level meter to control the thickness of a sludge bed layer.
The mud scraper driving device of the secondary sedimentation tank F controls the rotating speed of the scraping bridge through the frequency converter, and the rotating speed is controlled within the range of 4-8 cm/s according to different tank diameters, so that sludge is conveyed to the central mud bucket at the bottom of the tank through the bottom scraping plate and the sludge guide pipe.
Preferably, the denitrification can be achieved by controlling the thickness of the sludge blanket in the secondary sedimentation tank F. Specifically, the secondary sedimentation tank F can be provided with an online sludge level meter on the suspension bridge from the center 2/3 of the tank, monitor the thickness of the sludge bed layer on line, and by controlling the rotation speed of the mud scraper and/or the flow of discharging sludge by the excess sludge pump P3, the thickness of the sludge bed layer is kept within a proper range, such as 1-2.5m, 1-2m, 1.5-2m, 1.5-2.5m, preferably 1.5-2.5m, so as to promote the bottom sludge to be in a hydrolysis state, the activated sludge is hydrolyzed by itself to generate absorbable organic matters as a carbon source, and the organic matters are subjected to denitrification reaction with nitrate in water, thereby achieving the purpose of further removing the total nitrogen in the wastewater, and the removal efficiency of the total nitrogen is very high. The setting of the thickness of the sludge bed layer of the secondary sedimentation tank is matched with the setting of the second facultative zone, and the concrete expression is that, on one hand, the second facultative zone reduces the dissolved oxygen concentration of the mixed liquid flowing to the secondary sedimentation tank, which is beneficial to the realization of the hydrolysis state of the sludge at the bottom of the secondary sedimentation tank; on the other hand, the carbon source required by denitrification reaction in the sludge bed layer of the secondary sedimentation tank can be from the surplus carbon source processed at the upstream or the available carbon source generated by self degradation of the sludge in the secondary sedimentation tank, and the second facultative anaerobic zone is arranged to reserve the surplus carbon source for the secondary sedimentation tank to a certain extent. In addition, because denitrification can generate nitrogen, in a general municipal sewage treatment process, the thickness of sludge in a secondary sedimentation tank cannot be too high, the denitrification action needs to be avoided as much as possible, otherwise, excessive nitrogen is generated to cause the sludge to float upwards, and the quality of effluent water is poor. But due to the characteristics of the coal chemical wastewater, the biochemical sludge has high specific gravity, a secondary sedimentation tank can be used for carrying out denitrification reaction to remove a small part of nitrate, and the generated nitrogen does not float upwards.
The effect of the scheme according to the present invention will be further described by comparing the treatment system for coal chemical industry wastewater according to the first embodiment of the present invention with a conventional treatment system. The process flow of the conventional treatment system (comparison item) is shown in fig. 1, and specifically comprises the following steps: a preposed denitrification area A1, a first aeration tank O1, a postpositive denitrification area A2, a second aeration tank O2, a degassing tank D and a secondary sedimentation tank F. The processing system according to the present invention is shown in fig. 2, and specifically includes: a preposed denitrification area A1, a nitrification and decarbonization area O1, a first facultative anaerobic area C1, a postpositive denitrification area A2, a second facultative anaerobic area C2 and a secondary sedimentation tank F.
As shown in FIG. 5, which shows a comparison of the data of the post-denitrification region A2 according to the present example and the post-denitrification region A2 according to the comparative example in the case of the same amount of carbon source being fed, it can be seen that the dissolved oxygen concentration of the post-denitrification region A2 according to the present example is very low and is significantly lower than that of the post-denitrification region A2 according to the comparative example, and therefore, the post-denitrification region A2 according to the present example is brought into an anaerobic state more favorable for the denitrification reaction, thereby achieving a greater nitrate removal amount, and as shown in FIG. 5, the nitrate removal amount of the post-denitrification region A2 according to the present example is also significantly higher than that of the post-denitrification region A2 according to the comparative example. The reason why the post-denitrification region a2 according to the present embodiment can achieve such a low dissolved oxygen concentration is that since the post-denitrification region a2 is preceded by the first facultative zone C1, the first facultative zone C1 according to the present embodiment has a lower dissolved oxygen concentration than the first aeration tank O1 according to the comparative example, and thus the dissolved oxygen concentration can be lower after entering the post-denitrification region a 2.
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 1.5-2.5m, while the sludge thickness of the secondary sedimentation tank of the conventional treatment system is 0.5-1.5m, the difference in the nitrate inlet and outlet water of the secondary sedimentation tank F according to the present invention is 4 to 10mg/l, and the difference in the nitrate inlet and outlet water of the secondary sedimentation tank of the conventional treatment system is 0 to 3 mg/l. Obviously, the secondary sedimentation tank F can effectively remove the nitrate further, so that the total nitrogen in the wastewater is further removed, because the thick sludge bed layer promotes the bottom sludge to be in a hydrolysis state, and the activated sludge is hydrolyzed by itself to generate absorbable organic matters serving as a carbon source to perform denitrification reaction with the nitrate in the water. In contrast, nitrate removal in the secondary sedimentation tank of conventional treatment systems is not significant.
[ second embodiment ]
The treatment system for coal chemical industry wastewater according to the second embodiment of the present invention includes a pre-denitrification zone a1, a nitrification-decarbonization zone O1, a post-denitrification zone a2, and a secondary sedimentation tank F. The pre-denitrification zone A1, the nitrification-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 the description thereof is omitted. It should be noted that the thickness of the sludge bed layer of the secondary sedimentation tank F according to the second embodiment may be kept within a suitable range, for example, 1-2.5m, 1-2m, 1.5-2m, 1.5-2.5m, preferably 1.5-2.5m, to promote the hydrolysis of the bottom sludge, and the activated sludge itself is hydrolyzed to generate absorbable organic matters as a carbon source, and the absorbable organic matters are subjected to denitrification reaction with the nitrate in the water, so as to achieve the purpose of further removing the total nitrogen in the wastewater. And compared with the conventional treatment system, the system has the advantages that the concentration of dissolved oxygen in the mixed liquid flowing to the secondary sedimentation tank is reduced due to the elimination of the second aeration tank, and the efficiency of the preposed denitrification zone is improved after the sludge flows back to the preposed denitrification zone.
Although the exemplary embodiment of the treatment system for coal chemical industry wastewater according to the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made to the specific embodiments described above, and various combinations of the technical features and structures of the present invention can be made without departing from the concept of the present invention.

Claims (12)

1. A treatment system for coal chemical industry wastewater, comprising:
the water to be treated enters the preposed denitrification area to carry out denitrification reaction, and the preposed denitrification area is provided with: an underwater agitator configured to agitate within the pre-denitrification zone; a preposed carbon source adding point which is configured to add a carbon source to the preposed denitrification area,
a nitrification and decarbonization area, wherein the mixed liquid from the preposed denitrification area enters the nitrification and decarbonization area to carry out nitrification reaction, the nitrification and decarbonization area is provided with an aeration device which is required for providing oxygen for the reaction,
a first facultative zone, the mixed liquor from the nitrification and decarbonization zone enters the first facultative zone to carry out synchronous nitrification and denitrification,
the post-denitrification area is used for allowing the residual mixed liquor from the first facultative anoxic area to enter the post-denitrification area for denitrification reaction, and is provided with: an underwater agitator configured to agitate in the post-nitrification zone; a post carbon source feeding point which is configured to feed a carbon source into the post denitrification area,
the mixed liquid from the post-denitrification zone enters the second facultative denitrification zone for synchronous nitrification and denitrification,
and the mixed liquid from the second facultative anaerobic zone enters the secondary sedimentation tank for sludge-water separation, the separated clarified effluent is discharged to a downstream processing unit, a part of sludge at the bottom returns to the inlet of the preposed denitrification zone through a sludge return pump, and the residual sludge is discharged to a subsequent sludge processing unit through a residual sludge pump.
2. The treatment system according to claim 1, wherein the sludge bed thickness of the secondary sedimentation tank is in the range of 1.5-2.5m, so that denitrification reaction occurs in the sludge bed.
3. The treatment system according to claim 2, wherein the secondary sedimentation tank is provided with an on-line sludge level meter on the hanging bridge from the tank center 2/3, and the thickness of the sludge bed layer of the secondary sedimentation tank is controlled according to the data measured by the on-line sludge level meter, so that the sludge at the bottom of the secondary sedimentation tank is in a hydrolysis state.
4. The treatment system of claim 1, wherein the pre-denitrification zone is further provided with: an acid adding point, configured to add acid to the pre-denitrification region to adjust the pH value of the pre-denitrification region and neutralize the pH value generated by decomposition of organic acid salt and organic nitrogen; and a phosphorus source feeding point configured to feed a phosphorus source to the pre-denitrification region.
5. The processing system as set forth in claim 1,
wherein the preposed denitrification area is also provided with a pH probe and an oxidation-reduction potential probe which are configured to monitor the pH value and the anoxic state of the preposed denitrification area,
wherein the nitrification and decarbonization area is provided with an online dissolved oxygen analyzer which is configured to monitor the dissolved oxygen concentration of the nitrification and decarbonization area online, the oxygen supply amount of the aeration device is adjusted according to the monitored dissolved oxygen concentration,
the post-denitrification area is provided with an online nitrate analyzer which is configured to monitor the nitrate concentration of the post-denitrification area online, and the adding amount of the post-carbon adding point is adjusted according to the monitored nitrate concentration.
6. The treatment system according to any one of claims 1 to 5, wherein the first facultative zone is provided with one or more first stirrers for stirring and a first aeration device for providing oxygen, a portion of the mixed liquor in the first facultative zone being returned to the inlet of the pre-denitrification zone by a reflux pump; the second facultative zone is provided with one or more second stirrers for stirring and a second aeration device for providing oxygen.
7. The treatment system according to claim 6, wherein the inlet of the first facultative zone is provided with an on-line ammonia nitrogen analyzer, so that when the ammonia nitrogen concentration at the inlet of the first facultative zone is lower than a first set value, only the first stirrer 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 stirrer and the first aeration device are operated.
8. The treatment system of claim 7, wherein the first set point is 1-5 mg/l.
9. The treatment system according to claim 7, wherein the outlet of the first facultative zone is provided with a first online dissolved oxygen analyzer configured to online monitor the dissolved oxygen concentration at the outlet of the first facultative zone, and the oxygen supply amount 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 to be 0.5-1 mg/l.
10. The treatment system according to claim 6, wherein the inlet of the second facultative zone is provided with an on-line COD analyzer, so that when the COD concentration of the inlet of the second facultative zone is lower than a second set value, only the second stirrer is operated, and when the COD concentration of the inlet of the second facultative zone is higher than the second set value, the second stirrer and the second aeration device are operated.
11. The treatment system according to claim 10, wherein the second set value is 40-100 mg/l.
12. A treatment system for coal chemical industry wastewater, comprising:
the water to be treated enters the denitrification zone to carry out denitrification reaction,
a nitrification and decarbonization area, wherein the mixed liquid from the preposed denitrification area enters the nitrification and decarbonization area to carry out nitrification reaction, the nitrification and decarbonization area is provided with an aeration device which is required for providing oxygen for the reaction,
and the mixed liquid from the second facultative anaerobic zone enters the secondary sedimentation tank for sludge-water separation, the separated clarified effluent is discharged to a downstream processing unit, part of the bottom sludge flows back to the inlet of the preposed denitrification zone through a sludge reflux pump, and the residual sludge is discharged to a subsequent sludge processing unit through a residual sludge pump, wherein the thickness of a sludge bed layer of the secondary sedimentation tank is within the range of 1.5-2.5 m.
CN202010787787.6A 2020-08-07 2020-08-07 Treatment system for coal chemical industry wastewater Pending CN111777291A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113069801A (en) * 2021-03-26 2021-07-06 中冶北方(大连)工程技术有限公司 Control system and method for thickener

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113069801A (en) * 2021-03-26 2021-07-06 中冶北方(大连)工程技术有限公司 Control system and method for thickener

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