CN210945291U - System for be used for mud minimizing to handle - Google Patents

Abstract

The utility model discloses a system for be used for mud minimizing to handle, include: a contact reaction pretreatment tank, a water ejector and a contact reaction tank. In the mixing zone of the contact reaction pretreatment tank, the introduced sludge and ozone are mixed and reacted. The water ejector is arranged at the downstream of the contact reaction pretreatment tank and is configured to mix ozone with sludge by using a venturi principle so that the ozone is dispersed in the sludge in the form of bubbles. In the contact reaction tank, the sludge and the ozone are contacted and reacted again. According to the utility model discloses a system for mud minimizing treatment adopts two-stage ozone sludge contact reaction pond, can share, reduce the operational risk.

Description

System for be used for mud minimizing to handle

Technical Field

The utility model relates to a water treatment technical field specifically relates to a system for mud minimizing is handled.

Background

In the sewage treatment industry, the treatment and disposal of sludge cannot be ignored, and the main reasons are as follows: firstly, the components of the sludge are complex, and the sludge contains a large amount of perishable organic matters, pathogenic bacteria, impurities and the like, so that the risks of threatening the environmental safety and human health exist; secondly, the sludge yield is high, and generally, 6 tons of sludge (80% water content) is generated by treating 1 ten thousand tons of wastewater, and the daily yield of the sludge reaches 120 tons in a typical municipal sewage plant (20 ten thousand tons per day of treatment capacity). More seriously, if the generated sludge is dangerous waste, such as sludge from sewage treatment in petrochemical industry and coal chemical industry, the cost/expense of treatment and disposal is higher. Therefore, under the precondition of ensuring the stable operation of the wastewater treatment process, how to realize the sludge reduction has important practical significance.

The ozone oxidation-reduction potential is high, organic matters in the sludge can be oxidized and decomposed, and the microbial structure can be destroyed, so that the ozone can be applied to sludge reduction treatment. At present, there is a device that mixes ozone and sludge to perform a contact reaction, and stirring is performed with a stirrer. However, the traditional stirring mode and structure are too single, the mixing effect is poor, the mass transfer efficiency is low, and the requirements of high reaction rate and thorough reaction of ozone and sludge cannot be met. Moreover, the sludge properties (such as sludge amount, organic matter content and the like) are influenced by factors such as the quality, season, water amount and the like of the incoming water, and the fluctuation of the sludge properties means that the reaction conditions of the sludge and the ozone need to be flexibly adjusted. However, the traditional sludge reduction system has weak strain capacity and impact resistance, and has the phenomena of insufficient reaction between ozone and sludge and poor reduction effect.

SUMMERY OF THE UTILITY MODEL

To the above problem, according to the utility model discloses, a system for mud minimizing treatment is proposed, include: a contact reaction pretreatment pool, a water ejector and a contact reaction pool. The contact reaction pretreatment pool comprises: a pretreatment sludge inlet configured to introduce sludge to be treated into the contact reaction pretreatment tank; a pretreatment ozone inlet configured to introduce ozone into the contact reaction pretreatment tank; a mixing zone in which the introduced sludge and ozone are mixed and reacted; a first agitator disposed in the mixing zone and configured to agitate the sludge and ozone within the mixing zone to promote reaction of the sludge with the ozone; and a pretreated sludge outlet configured to discharge pretreated sludge. The water ejector is arranged at the downstream of the contact reaction pretreatment tank, is connected to a pretreated sludge outlet, and is configured to mix ozone with sludge by using a Venturi principle, so that the ozone is dispersed in the sludge in the form of bubbles. The contact reaction tank comprises: a sludge and ozone inlet configured to introduce a gas-liquid mixture of sludge and ozone from the waterjet into the contact reaction tank; a second agitator disposed in the contact reaction tank and configured to agitate sludge and ozone in the contact reaction tank to promote a reaction of the sludge with the ozone; and a sludge outlet configured to discharge the sludge treated by the contact reaction tank.

According to the utility model discloses a two-stage ozone sludge contact reaction pond that is used for system's adoption contact reaction preliminary treatment pond and contact reaction pond to reduce quantization arranges, and every grade of sludge contact pond all has independent ozone dosing system and sludge reaction system, can throw with quantity and dwell time isoparametric according to the corresponding change ozone of concrete argillaceous condition, uses in a flexible way. The two-stage ozone sludge contact reaction tank can share and reduce the running risk of sludge reduction. The mixing zone of the contact reaction pretreatment tank plays a role in improving the fluidity of the sludge and reducing the sludge reduction load of a subsequent treatment unit. The stirrer and the water ejector are introduced into the system together, so that the contact reaction is implemented in steps and stages, the mass transfer efficiency of ozone is effectively improved, and the mixed reaction effect of ozone and sludge is guaranteed.

The system for sludge reduction treatment according to the present invention may have one or more of the following features.

According to one embodiment, the system further comprises a sludge conduit directly connected to the waterjet configured to introduce sludge to be treated directly into the waterjet without passing through the contact reaction pretreatment tank. The sludge quality is better, when the impurities are not contained or less, the contact reaction pretreatment tank can be saved, and the sludge enters the contact reaction tank from the water injector, so that the process flow is shortened, and the treatment cost is saved.

According to one embodiment, the contact reaction pretreatment tank further comprises a separation zone which is arranged at the downstream of the mixing zone and at the upstream of the pretreated sludge outlet and is communicated with the mixing zone, the bottom of the separation zone is provided with a sand collecting hopper for collecting impurities, and solid impurities in the sludge from the mixing zone are accumulated in the sand collecting hopper under the action of gravity in the separation zone. The separation of impurity has been realized to the setting of disengagement zone, has avoided follow-up water dart to block up.

According to one embodiment, the first stirrer of the contact reaction pretreatment tank is tapered, and both the tapered surface and the bottom surface are provided with a plurality of swirl plates spaced apart from each other. The structure of the first stirrer enables the first stirrer to have a large action range and a strong mixing effect.

According to one embodiment, the contact reaction pretreatment tank further comprises an ozone distributor formed in an annular shape and disposed directly below the first stirrer, the annular ozone distributor being parallel to the bottom surface of the mixing zone, the annular diameter being slightly smaller than the diameter of the bottom surface of the first stirrer, the ozone from the pretreatment ozone inlet being released to the mixing zone through the ozone distributor. Under the action of the first stirrer, the ozone bubbles released from the ozone gas distributor generate a rapid turbulent mixing effect with the sludge in the mixing zone, so that the full contact reaction of the sludge and the ozone is promoted, and the sludge reduction effect is improved.

According to one embodiment, the contact reaction tank further comprises a shower head disposed below the second agitator, the shower head being configured to spray a gas-liquid mixture from the sludge and ozone inlet into the contact reaction tank. The action force of the spray head releasing the steam-water mixture is upward, the driving force generated by the stirrer is downward, the interaction of the spray head and the stirrer can generate strong turbulence in the pool to generate bubbles, and the ozone and the sludge are promoted to react violently.

According to one embodiment, the contact reaction tank further comprises a draft tube comprising a cylindrical body surrounding and spaced apart from at least the paddle of the second agitator and the showerhead, and open upper and lower ends spaced apart from the top and bottom walls of the contact reaction tank, respectively. The generation of turbulence, as well as the circulation and mixing of the material throughout the tank, is further enhanced based on the use of a draft tube in combination with a second agitator.

According to one embodiment, the height of the guide shell is 1/3-1/2 of the height of the contact reaction tank. The proper height enables the ozone and the sludge to be in contact reaction better.

According to one embodiment, the guide shell is cemented or made of stainless steel. Therefore, the guide shell is low in cost and durable.

According to one embodiment, the system further comprises an ozone generator configured to generate ozone and adjustably delivered to the pretreatment ozone inlet of the contact reaction pretreatment tank and the water jet. The supply of ozone is realized, and the flow rate of the ozone conveyed to the contact reaction pretreatment tank and the water ejector can be independently and adjustably controlled.

According to one embodiment, the contact reaction pretreatment tank comprises a first tail gas outlet configured to discharge residual tail gas in the contact reaction pretreatment tank; the contact reaction tank includes a second off-gas outlet configured to vent residual off-gas within the contact reaction tank. Wherein the system further comprises: a tail gas destructor connected to the first and second tail gas outlets and configured to convert ozone in the tail gas discharged from the first and second tail gas outlets into oxygen for recycling; and the recycling pipeline is connected with the tail gas destructor and the aeration tank so as to convey the oxygen discharged by the tail gas destructor to the aeration tank. The tail gas destructor converts the ozone tail gas into mixed gas mainly containing oxygen for the microorganisms in the aeration tank to utilize, thereby realizing the resource utilization of the ozone tail gas.

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. The drawings are intended to depict only some embodiments of the invention, and not all embodiments of the invention are limited thereto.

Fig. 1 is a process flow diagram when using a system for sludge reduction treatment according to the present invention.

Fig. 2 is a schematic diagram of a contact reaction pretreatment tank of a system for sludge reduction treatment according to the present invention.

Fig. 3 is a schematic diagram of a contact reaction tank of a system for sludge reduction treatment according to the present invention.

Detailed Description

In order to make the technical solution of the present invention, its purpose, technical solution and advantages become clearer, the drawings of the embodiments of the present invention will be combined hereinafter, and the technical solution of the embodiments of the present invention will be clearly and completely described. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive work based on the described embodiments of the present invention, belong to the protection scope of the present 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 in the claims does not indicate any order, quantity, or importance, but rather is 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.

According to the utility model discloses a system 1 for mud minimizing is used for the mud that sewage treatment plant produced especially biochemical mud to realize mud minimizing as the processing object, through the contact reaction of mud and ozone. Fig. 1 shows a flow diagram of a system 1 for sludge reduction treatment according to the invention when operating a sewage treatment system. As shown in figure 1, after sewage passes through an anaerobic/anoxic tank and an aeration tank, solid-liquid separation is carried out in a secondary sedimentation tank, sludge is deposited at the bottom of the secondary sedimentation tank due to the action of gravity, and clear liquid overflows out of the secondary sedimentation tank. The sludge in this case is a solid-liquid mixture having a solid content of about 0.7% to 1%, but those skilled in the art will understand that the solid content of the sludge is influenced by the quality of the incoming water, the season, the amount of water, and the like, and is not limited to the above range. The sludge from the secondary sedimentation tank can be returned to the aeration tank after being treated by the system 1 for sludge reduction treatment according to the utility model.

As shown in fig. 1, the system 1 for sludge reduction treatment according to the present invention may include a contact reaction pretreatment tank 100, a water ejector 300 and a contact reaction tank 200 in the direction of sludge flow. The contact reaction pretreatment tank 100 and the contact reaction tank 200 are both configured to carry out contact reaction between sludge and ozone, decompose organic matters in the sludge, and realize sludge reduction. Wherein the water jet 300 is configured to mix ozone with sludge using the venturi principle so that ozone is dispersed in the sludge in the form of bubbles. Therefore, the sludge treatment process can be as follows: secondary sedimentation tank sludge-contact reaction pretreatment tank 100-water injector 300-contact reaction tank 200-reduced sludge-aeration tank. Alternatively, the system may further include a sludge pipe directly connected to the water jet apparatus 300, and thus, the sludge to be treated from the secondary sedimentation tank may be directly introduced into the water jet apparatus 300 without passing through the contact reaction pretreatment tank 100, in which case, the treatment flow of the sludge may be: the process of the secondary sedimentation tank sludge-water ejector 300-contact reaction tank 200-reduced sludge-aeration tank is generally used for the conditions of high sludge quality, low impurity content or low solid content. The system also includes an ozone generator 400 configured to generate ozone and deliver it to the contact reaction pretreatment tank 100 and the water sparger 300. It will be understood by those skilled in the art that the ozone supplied to the contact reaction pretreatment tank 100 and the water ejector 300 can be controlled individually, that is, supplied to only the water ejector 300, or supplied to both the reaction pretreatment tank and the water ejector 300, and the rate of the ozone supplied to the reaction pretreatment tank and the water ejector 300 can be controlled individually. Two stages of ozone sludge contact reaction tanks, namely a contact reaction pretreatment tank 100 and a contact reaction tank 200, are arranged, each stage of sludge contact tank is provided with an independent ozone adding system and a sludge reaction system, parameters such as ozone adding amount, retention time and the like can be correspondingly changed according to specific mud quality conditions, and the ozone sludge contact reaction tank is flexible to use. The two-stage ozone sludge contact reaction tank can share and reduce the running risk of sludge reduction.

Fig. 2 is a schematic diagram of a contact reaction pretreatment tank 100 of the system 1 for sludge reduction treatment according to the present invention. As shown in fig. 2, the contact reaction pretreatment tank 100 may include two parts, a mixing zone 110 and a separation zone 120, in which the sludge and ozone are mixed and reacted in the mixing zone 110 and the separation of the sludge from impurities is achieved in the separation zone 120.

The mixing zone 110 may be provided with: a pretreated sludge inlet 101 configured to introduce sludge to be treated into the mixing zone 110 of the contact reaction pretreatment tank 100; a pre-treatment ozone inlet 102 configured to introduce ozone into the mixing zone 110 of the contact reaction pre-treatment cell 100; a first agitator 103 configured to agitate the sludge and ozone within the mixing zone 110 to promote reaction of the sludge with the ozone. Preferably, the first stirrer 103 is conical, the conical surface is of streamlined design, both the conical surface and the bottom surface are provided with a plurality of swirl plates spaced apart from each other. The structure of the first stirrer 103 enables the first stirrer 103 to have a wide range of action and a strong mixing effect. Preferably, the mixing zone 110 is further provided with an ozone distributor 104 formed in a ring shape and disposed directly below the first stirrer 103, a plane in which a ring-shaped main body of the ozone distributor 104 is located is parallel to a bottom surface of the mixing zone 110, a diameter of the ring is slightly smaller than a diameter of a bottom surface of the first stirrer 103, and ozone from the pre-treatment ozone inlet 102 is discharged to the mixing zone 110 through the ozone distributor 104. Under the action of the first stirrer 103, the ozone bubbles released from the ozone distributor 104 generate a rapid turbulent mixing action with the sludge in the mixing zone 110, which is beneficial to promoting the full contact reaction between the sludge and the ozone and improving the sludge reduction effect. Moreover, the solid content of the sludge is gradually reduced (namely, part of the sludge is reduced) after a certain period of contact reaction, and the fluidity of the sludge is improved.

The separation region 120 is disposed downstream of the mixing region 110 and is communicated with the mixing region 110, the sludge flows to the separation region 120 after passing through the mixing region 110, in the separation region 120, the sludge exists in a uniform mixture state, and the impurities are accumulated in a sand collecting hopper disposed at the bottom of the separation region 120 under the action of gravity, so that the separation of the sludge and the impurities is realized. The sludge after impurity separation is discharged from the pretreated sludge outlet 106. The top of the separation zone 120 may also be provided with a first off-gas outlet 105 for discharging residual off-gas, which may include residual ozone and other gases generated by the contact reaction.

The contact reaction tank 200 is arranged in the pretreatment tank, so that the following advantages are achieved: on one hand, the mixing area 110 carries out pre-ozonation on the sludge, namely the solid content of the solid mixture is reduced, the water content is higher, the fluidity of the sludge is improved, the sludge can more easily pass through the water ejector 300, and the treatment load and the treatment risk of a subsequent reduction unit are reduced. On the other hand, the separation area 120 removes sand from the sludge to separate impurities, thereby preventing the subsequent water ejector 300 from being blocked.

The sludge discharged from the contact reaction pretreatment tank 100 is conveyed by a water pump under pressure, passes through a water ejector 300, and then enters the contact reaction tank 200. Meanwhile, ozone is sucked into the ejector 300 based on the venturi principle to be secondarily mixed with the sludge, and the ozone is dispersed into the sludge in the form of fine bubbles, which are fine and have a mixing intensity much higher than that of the primary mixing occurring at the mixing zone 110 of the contact reaction pretreatment tank 100. The stirrer is matched with the water ejector 300 to realize the step-by-step implementation of the contact reaction, so that the mass transfer efficiency of the ozone is effectively improved, and the mixed reaction effect of the ozone and the sludge is ensured.

Fig. 3 is a schematic view of a contact reaction tank 200 of the system 1 for sludge reduction treatment according to the present invention. The contact reaction cell 200 may include: a sludge and ozone inlet 201 configured to introduce a gas-liquid mixture of sludge and ozone from the water ejector 300 into the contact reaction tank 200; a second agitator 202 provided in the contact reaction tank 200 and configured to agitate the sludge and ozone within the contact reaction tank 200 to promote a reaction of the sludge with ozone; a shower head disposed below the second agitator 202 and configured to spray a gas-liquid mixture from the sludge and ozone inlet 201 into the contact reaction tank 200; and a sludge outlet 205 configured to discharge the sludge treated by the contact reaction tank 200. Preferably, the contact reaction tank 200 further includes a guide shell 203, the guide shell 203 including a cylindrical body surrounding and spaced apart from at least the paddle and the shower head of the second stirrer 202, and open upper and lower ends spaced apart from the top and bottom walls of the contact reaction tank 200, respectively. The height of the guide cylinder 203 may be 1/3-1/2 of the height of the contact reaction tank 200. Here, the height of the contact reaction cell 200 refers to an effective cell depth of the contact reaction cell 200, i.e., an inner depth of the contact reaction cell 200. The guide shell 203 may be cemented or made of stainless steel. The contact reaction cell 200 can further include a second off-gas outlet 204 configured to vent residual off-gas from the contact reaction cell 200. As shown in fig. 3, the contact reaction tank 200 may further include a partition wall, and after the sludge and the ozone contact and react in the area where the guide cylinder 203 is located, the sludge passes through the lower part of the partition wall and enters an outlet area, in which the sludge is discharged from the sludge outlet 205, and the tail gas is discharged from the second tail gas outlet 204.

The specific working principle of the contact reaction tank 200 is as follows: the action force of the nozzle below the second stirrer 202 for releasing the gas-water mixture is upward, and the driving force generated by the second stirrer 202 is downward, so that the interaction of the two can generate strong turbulence in the contact reaction tank 200 and generate a large amount of bubbles, and the ozone and the sludge are promoted to react violently. In addition, the guide cylinder 203 confines the second stirrer 202 and the spray head in a limited space, further enhancing the generation of turbulence, and the circulation and mixing of the substances throughout the contact reaction tank 200.

After passing through the contact reaction tank 200, the solid content of the sludge is further reduced, and the target of expected reduction is realized. After this, the sludge is conveyed via an outlet to an aeration tank. The reaction time and the amount of ozone added in the contact reaction tank 200 may be adjusted according to the properties of the sludge.

As shown in fig. 1, the system 1 for sludge reduction treatment according to the present invention may further include: a tail gas destructor 500 connected to the first tail gas outlet 105 and the second tail gas outlet 204 and configured to convert ozone in the tail gas discharged from the first tail gas outlet 105 and the second tail gas outlet 204 into oxygen for recycling; a recycling pipe connecting the tail gas destructor 500 and the aeration tank to transport the oxygen discharged from the tail gas destructor 500 to the aeration tank. The tail gas treated by the tail gas destructor 500 contains a large amount of oxygen which is an important factor for maintaining the metabolic activity of microorganisms in the aeration tank, so that the oxygen conveyed to the aeration tank from the tail gas destructor 500 can be used for the metabolic activity of aerobic microorganisms, and the resource utilization of the ozone tail gas is realized.

The exemplary embodiment of the system 1 for sludge reduction treatment according to the present invention has been described in detail with reference to the preferred embodiments, however, it will be understood by those skilled in the art that various modifications and changes may be made to the above specific embodiments without departing from the concept of the present invention, and various combinations of the various technical features and structures of the present invention may be implemented without departing from the scope of the present invention.

List of reference numerals

1 System for sludge reduction treatment

100 contact reaction pretreatment pool

101 inlet for pretreated sludge

102 pretreatment ozone inlet

103 first stirrer

104 ozone gas distributor

105 first tail gas outlet

106 outlet for pretreated sludge

110 mixing zone

120 separation area

200 contact reaction tank

201 sludge and ozone inlet

202 second stirrer

203 guide flow cylinder

204 second tail gas outlet

205 sludge outlet

300 water injector

400 ozone generator

500 tail gas destructor

Claims (11)

1. A system for sludge reduction treatment, comprising:

a contact reaction pretreatment tank comprising: a pretreatment sludge inlet configured to introduce sludge to be treated into the contact reaction pretreatment tank; a pretreatment ozone inlet configured to introduce ozone into the contact reaction pretreatment tank; a mixing zone in which the introduced sludge and ozone are mixed and reacted; a first agitator disposed in the mixing zone and configured to agitate the sludge and ozone within the mixing zone to promote reaction of the sludge with the ozone; and a pretreated sludge outlet configured to discharge pretreated sludge;

a water ejector disposed downstream of the contact reaction pretreatment tank, connected to a pretreated sludge outlet, and configured to mix ozone with sludge using a venturi principle such that ozone is dispersed in the sludge in the form of bubbles; and

a contact reaction cell, comprising: a sludge and ozone inlet configured to introduce a gas-liquid mixture of sludge and ozone from the waterjet into the contact reaction tank; a second agitator disposed in the contact reaction tank and configured to agitate sludge and ozone in the contact reaction tank to promote a reaction of the sludge with the ozone; and a sludge outlet configured to discharge the sludge treated by the contact reaction tank.

2. The system of claim 1, further comprising a sludge conduit directly connected to the waterjet configured to direct sludge to be treated directly into the waterjet without passing through the contact reaction pretreatment tank.

3. The system of claim 1, wherein the contact reaction pretreatment tank further comprises a separation zone disposed downstream of the mixing zone and upstream of the pretreated sludge outlet and communicating with the mixing zone, the bottom of the separation zone is provided with a sand collection hopper for collecting impurities, and solid impurities in the sludge from the mixing zone are accumulated in the sand collection hopper under the action of gravity in the separation zone.

4. The system of claim 1, wherein the first agitator of the contact reaction pretreatment tank is tapered, and wherein both the tapered surface and the bottom surface are provided with a plurality of swirl plates spaced apart from each other.

5. The system of claim 4, wherein the contact reaction pretreatment tank further comprises an ozone distributor formed in a ring shape and disposed directly below the first stirrer, the ring-shaped ozone distributor being parallel to the bottom surface of the mixing zone and having a diameter slightly smaller than that of the bottom surface of the first stirrer, the ozone from the pretreatment ozone inlet being discharged to the mixing zone through the ozone distributor.

6. The system of any one of claims 1-5, wherein the contact reaction tank further comprises a spray head disposed below the second agitator, the spray head configured to spray a gas-liquid mixture from the sludge and ozone inlet into the contact reaction tank.

7. The system of claim 6, wherein the contact reaction tank further comprises a draft tube comprising a barrel surrounding and spaced apart from at least the blades of the second agitator and the sparger, and open upper and lower ends spaced apart from the top and bottom walls of the contact reaction tank, respectively.

8. The system of claim 7, wherein the height of the guide shell is 1/3-1/2 of the contact reaction tank height.

9. The system of claim 7, wherein the draft tube is cemented or made of stainless steel.

10. The system of any one of claims 1-5, further comprising an ozone generator configured to generate ozone and adjustably deliverable to the pretreatment ozone inlet of the contact reaction pretreatment tank and the water eductor.

11. The system of any one of claims 1-5, wherein the contact reaction pretreatment tank comprises a first tail gas outlet configured to discharge residual tail gas within the contact reaction pretreatment tank; the contact reaction tank comprises a second tail gas outlet configured to discharge residual tail gas in the contact reaction tank,

wherein the system further comprises:

a tail gas destructor connected to the first and second tail gas outlets and configured to convert ozone in the tail gas discharged from the first and second tail gas outlets into oxygen for recycling;

and the recycling pipeline is connected with the tail gas destructor and the aeration tank so as to convey the oxygen discharged by the tail gas destructor to the aeration tank.

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