KR20010000303A - A Soil Clothing-Style Contact Oxidation Apparatus with Recycle of Nitrified Liquid and Contact Oxidation Method of Using the Same - Google Patents

Abstract

PURPOSE: The wastewater treatment system that has internal circulation contact oxidation system covered with soil uses carbon compound, nitrogen and phosphorus as a nutrient of microorganisms, lawn, microbe in soil. CONSTITUTION: Wastewater is stored in a precipitation-denitrification tank (1), and precipitated/denitrified wastewater in the precipitation/denitrification cell is aerated in the first aeration chamber (2) by an air injector (11). Aerated wastewater in the first aeration is separated solid and liquid in a precipitation tank (3), and separated wastewater in the precipitation (3) is aerated in the second aeration chamber (4) by the air injector (11). In each tank, a part of nitrogen not treated is returned to the precipitation/denitrification tank (1) through a circulation pipe (14). In each tank, treated wastewater is discharged through an outlet (5).

Description

Soil Clothing-Style Contact Oxidation Apparatus with Recycle of Nitrified Liquid and Contact Oxidation Method of Using the Same}

The present invention relates to a medium- and small-scale soil-coated internal mild catalytic oxidation apparatus suitable for treating nitrogen and phosphorus as well as a carbon compound contained in sewage water, and a catalytic oxidation method using the same. And a soil coating type internal circulation contact oxidation apparatus composed of a second aeration tank, comprising a maternity network and a soil layer having a plurality of vent holes formed in an upper layer of each treatment tank, and a medium and small sewage treatment system in which plants are planted in the soil layer. It is about.

In addition, the introduced waste water is stored in the sedimentation denitrification tank (1); Aeration treatment of the sewage denitrified sewage water in the sedimentation denitrification tank (1) in the first aeration tank (2) through the air injection device (11); Separating the wastewater abandoned in the first aeration tank 2 into the sedimentation tank 3; The wastewater separated from the sedimentation tank 3 in the solid wastewater is abandoned in the second aeration tank 4 through the air injection device 11; In each of the above steps, a part of which is internally circulated to the settling denitrification tank 1 through an internal circulation tube 14 for final removal of nitrogen; And it relates to the internal circulation contact oxidation method of the soil-coated sewage water characterized in that the sewage water that has become the supernatant water through each treatment step is discharged through the discharge tank (5).

Eutrophication in closed waters such as lakes and lakes, which are emerging as a social problem in recent years, is caused by the influx of nitrogen and phosphorus compounds, which promotes the growth of algae, phytoplankton in the water. In this way, nitrogen and phosphorus compounds in the water itself is a contaminant and cause a loss of water resources value, but it is used as a nutrient required for algae growth to further deteriorate the water quality.

River water pollution is mainly caused by the inflow of pollutants such as domestic wastewater, industrial wastewater, and livestock wastewater, and the pollution concentrations of large urban rivers where populations and industrial complexes are concentrated are more serious. As a countermeasure against such river water pollution, it is required to expand the facilities of sewage treatment plants that can fundamentally block the cause of pollution. On the other hand, considering that river water pollution is caused by domestic wastewater in most cases, it is the primary source of the source of pollution, namely, small and medium sized sewage end purification facilities, rather than large-scale sewage treatment plants that require a lot of budget and space. The current situation is that a treatment facility is required to cut off the barriers and maintain a comfortable water environment.

The predominant nitrogen forms in sewage water are organic nitrogen and ammonia nitrogen (NH ₃ -N). Organic nitrogen is converted to ammonia nitrogen by the decomposition of microorganisms under anaerobic or aerobic conditions. There are many kinds of microorganisms causing oxidation of ammonia nitrogen, but representative ones include nitrosomonas and nitrobacter. These are all aerobic autotrophic bacteria and grow by oxidizing ammonia with oxygen. The nitrification of ammonia in water in the form of ammonia ions (NH ₄ ⁺ ) is as follows.

^{_{22NH 4 + + 37O 2 + 4CO}} 2 + HCO 3 - → C 5 H 7 O 2 N + 21NO 3 - + 20H 2 O + 42H +

Nitric acid produced by nitrification is reduced to harmless nitrogen gas (N ₂ ) by the microorganisms that reduce it, and released into the atmosphere. This is called denitrification. Denitrifying bacteria include species such as Pseudomonas, Micrococcus, Archomobactor and Bacillus, and these microorganisms are facultative heterotrophic microorganisms. Denitrification does not occur because it is used as a receptor. Therefore, in order to activate the denitrification, an oxygen-free environment and supply of sufficient organic matter are absolutely necessary. Methanol is the most widely used organic material for denitrification because of its economic feasibility. However, obtaining useful organic materials in sewage can reduce the cost of supplying methanol. In the denitrification process, since nitrate nitrogen (NO ₃ ⁻ ) is used as a hydrogen acceptor, it becomes an anaerobic reaction.

^{_{NO 3 - + 1.08CH 3 OH +}} H ++ → 0.065C 5 H 7 O 2 N + 0.47N 2 + 0.76CO 2 + 2.44H 2 0

In addition, the theory of removing phosphorus in sewage water increases the phosphorus intake by phosphate accumulating organisms (PAOs) when the environment in the reactor repeats anaerobic and aerobic conditions, which leads to the luxury uptake of microorganisms. ), The phosphorus is finally removed by removing sludge of high phosphorus intake with sludge.

Generally, wastewater treatment methods for removing nitrogen and phosphorus include physicochemical treatment and biological treatment. The physicochemical treatment methods include ammonia degassing, ion exchange using selective adsorption, precipitation of phosphorus using slaked lime and flocculant, and struvite formation of precipitation of nitrogen and phosphorus simultaneously. However, the physicochemical treatment method has the disadvantage of being sensitive to the temperature and cost, although the treatment is selectively performed, and the chemical cost and the environment required for operation are difficult to operate and the effluent is runoff. Is unstable and rarely used in the field.

The biological treatment method for removing nitrogen and phosphorus is to separate anaerobic-aerobic-anaerobic-aerobic reactors to induce organic material oxidation and nitrification reactions and microorganisms to ingest phosphorus in aerobic reactors according to the characteristics of each reactor. In the process, denitrification and phosphorus were released, which transformed nitrate nitrogen into nitrogen gas and released it into the atmosphere. These biological treatment methods are still in the research stage, and some of them are applied, but there are limitations in treatment efficiency and high plant construction costs. Nitrogen and phosphorus removal method according to the conventional biological treatment method is a post-rip (Phostrip) method, the activated sludge passes through the post-rip tank and aerobic tank to grow the phosphorus-removing microorganisms, in the above method the phosphorus released from the post-lip bath Nitrogen nitrate treated in chemicals and in an aerobic tank was circulated internally to an anoxic bath to remove nitrogen. However, this process requires the use of chemicals to remove phosphorus and does not function when the concentration of organic matter in the influent is low.

And MUCT and VIP process returns to an anaerobic tank to remove nitrate nitrogen in return sludge, denitrification and internal return to supply anaerobic tank to supply microorganisms to anaerobic tank. It was a problem.

In addition, the standard activated sludge method has a large amount of sludge and poor sludge dehydration, which causes problems in the sludge treatment process.In addition to the problems of deodorization facilities and excessive maintenance costs to solve the odor problems, organic matters are required. Although the removal efficiency of is good, there was a problem that can not efficiently remove nitrogen and phosphorus.

In addition, the post-lip method, MUCT process, VIP process, and standard activated sludge method were developed to be applied to medium and large-scale treatment plants. There was a problem that can not be removed efficiently.

The present invention is to solve the problems of the prior art as described above can not only efficiently remove nitrogen and phosphorus at the same time, but also simplify the treatment process of the conventional soil-coated contact oxidation tank to be suitable for medium and small sewage treatment plant. Soil-covered sewage water purification device that improves the economic efficiency and consists of three treatment tanks: sedimentation denitrification tank, first aeration tank, and second aeration tank. The upper part of the facility is covered by soil layer and plants, In case of artificial feeding, the same effect can be obtained by introducing less air into the aeration tank than when it comes into contact with concrete.In addition, when the microorganisms in the aeration tank are killed by abnormalities in the inflow water quality or failure of the air supply system, Microorganisms in the living soil layer are naturally supplied into the aeration tank. Was effective may be not only confirmed that this process can be obtained in a stable altitude and completed the present invention to remove nitrogen and phosphorus as.

After all, it is an object of the present invention to provide a soil-coated sewage treatment system capable of efficiently removing nitrogen and phosphorus simultaneously.

In addition, another object of the present invention is to provide a method for purifying wastewater using a soil-coated sewage treatment system capable of efficiently removing nitrogen and phosphorus simultaneously.

1 is a block diagram showing a soil-coated internal circulation catalytic oxidation process according to the present invention.

Figure 2 is a cross-sectional view for explaining the configuration of the soil-coated internal circulation catalytic oxidation process.

Figure 3 is a plan view for explaining the configuration of the soil-coated internal circulation catalytic oxidation process.

Figure 4 is a system diagram for explaining the treatment process of the soil-coated internal circulation catalytic oxidation.

* Description of the symbols for the main parts of the drawings *

1: sedimentation denitrification tank 1a: sedimentation denitrification tank 1 room

1b: sedimentation denitrification tank 2 room 2: first aeration tank

2a: 1st aeration tank 1 room 2b: 1st aeration tank 2 rooms

3: settling tank 4: second aeration tank

5: outfall 6: grass

7: Porous soil 8: Maternal network

9: media 10: pedestal

11: air injection device 12: electric valve

13: air supply pipe 14: internal circulation pipe

15: inlet 16: outlet

17: AP pump 18: connector

19: Subspace 20: Wall hole

21: Oni

Hereinafter, the present invention will be described in more detail.

Soil-covered sewage treatment system for achieving the object of the present invention is composed of three treatment tanks of sedimentation denitrification tank (1), the first aeration tank (2) and the second aeration tank (4), Between the porous soil layer (7) constituted a capillary network (8) formed with a plurality of air vents to prevent the soil from falling to the bottom, and microorganisms coexist in the soil layer exchanges with the treatment tank at the bottom, and also planting plants on the soil layer It is included.

In addition, the step of storing the introduced waste water in the sedimentation denitrification tank (1); Aeration treatment of the sewage denitrified sewage water in the sedimentation denitrification tank (1) in the first aeration tank (2) through the air injection device (11); Separating the wastewater abandoned in the first aeration tank 2 into the sedimentation tank 3; The wastewater separated from the sedimentation tank 3 in the solid wastewater is abandoned in the second aeration tank 4 through the air injection device 11; In each of the above steps, a part of which is internally circulated to the settling denitrification tank 1 through an internal circulation tube 14 for final removal of nitrogen; And it relates to the internal circulation contact oxidation method of the soil-coated sewage water characterized in that the sewage water that has become the supernatant water through each treatment step is discharged through the discharge tank (5).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. These examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples according to the gist of the present invention.

1 is a schematic view showing a soil-coated internal circulation catalytic oxidation process according to the present invention, Figure 2 is a cross-sectional view for explaining the configuration of the soil-coated internal circulation catalytic oxidation process, Figure 3 is a soil-coated interior 4 is a plan view for explaining the configuration of the cyclic catalytic oxidation process, Figure 4 shows a schematic diagram for explaining the treatment process of the soil-coated internal circulation catalytic oxidation process.

As shown in Figure 1, the soil-coated sewage treatment system according to the present invention is a sedimentation denitrification tank (1) consisting of a sedimentation denitrification tank (1a) and a sedimentation denitrification tank (1b) and a first aeration tank 1 ( It consists of three treatment tanks, the first aeration tank 2 and the second aeration tank 4, which are composed of 2a) and two first aeration tanks 2b, and transfers the supernatant water through the connection pipe 18 of each treatment tank. .

In general, the wastewater treatment apparatus receives a wastewater through an inlet, and has a screen for removing solids of a predetermined size or more. The wastewater stored in the wastewater tank may be supplied with biomedia, and may be supplied using an external blower or underwater aeration system. In the aeration tank and the aeration tank, which can be composed of a plurality of tanks for aeration, it consists of a sedimentation tank for separating solid-liquid from the wastewater treated by the microorganisms through a connecting pipe. Here, the general wastewater treatment apparatus is provided with a screen for removing solids of a predetermined size or more by receiving the wastewater, but in the present invention, since the treatment facility is buried underground, the screen device is not installed because no pumping facility is needed, and sedimentation is performed. The denitrification tank 1 is configured to receive the wastewater and directly flow into the sedimentation denitrification tank 1. The sedimentation denitrification tank (1) consisting of a sedimentation denitrification tank (1a) and a sedimentation denitrification tank (1b) has a sufficient lower space (19) in order to stack the sewage wastewater introduced through the inlet (15) as much as possible. In order to facilitate cleaning, the sedimentation denitrification tank (1) is divided into sedimentation denitrification tank (1a) and 2 chambers (1b), and the sedimentation denitrification tank (1) can be composed of one or more compartments according to the inflow of wastewater. have.

The inflow water transferred from the sedimentation denitrification tank 1 through the connecting pipe 18 moves to the first aeration tank 2 composed of the first aeration tank 2a and the first aeration tank 2b. The first aeration tank 2 is configured to supply oxygen sufficiently by an external air injection device 11 to maintain an aerobic state of the oxygen tank. In the first aeration tank (2) to reduce the lower space (19) to sufficiently fill the filter medium (9), the first aeration tank (2) is the first aeration tank 1 chamber (2a) and the first aeration tank 2 to increase the efficiency of aeration The wall consisting of the chamber 2b and partitioning the first aeration tank 1 chamber 2a and the 2 chamber 2b is provided with a wall hole 20 for horizontal movement of sewage water, and sewage and wastewater are discharged by the settling tank 3. The connector 18 for movement is comprised.

The sedimentation tank 3 is a treatment tank in which the sewage waste water abandoned in the first aeration tank 2 and the anaerobic sludge 21 separated from the sedimentation are collected and connected to supply the sewage and waste water first abandoned to the second aeration tank 4. The tube 18 is formed. In addition, in the second aeration tank (4), the same as the first aeration tank (1), the lower space 19 and the filling medium (9) is sufficiently filled to maximize the efficiency of aeration, the second aeration waste water discharge tank ( 5) and the connection pipe 18 and the inner circulation pipe 14 for moving to the sedimentation denitrification tank 1 are respectively configured. The waste water of the second aeration tank 4 circulated internally to the sedimentation denitrification tank 1 is denitrified and nitrogen is finally removed, and the treated water moved to the discharge tank 5 through the connecting pipe 18 is connected to the outlet 16. Through the outside.

The first aeration tank (2), the settling tank (3), the second aeration tank (4) and the discharge tank (5) by the external air injection device 11, the air is sufficiently supplied to each treatment tank through the air injection pipe (13). It is configured to.

In addition, the sludge 21 accumulated in the first aeration tank 2, the sedimentation tank 3, the second aeration tank 4, and the discharge tank 5 has an AP pump by adjusting a predetermined time interval in the external air injection device 11. Air is injected into 17 and returned to the sedimentation denitrification tank 1 along the inner circulation pipe 14.

Part of each treatment tank is filled with the filter medium (9) to give the soil microorganisms the closest conditions for growth not only in the soil layer but also inside the reactor, and the bottom of the filter medium (9) is installed at regular intervals The filter medium 9 does not fall into the lower space 19. As a filter medium (9), demolished stone crushed stone which is cheaper and more durable than other contact media, pottery roasted ocher pipe similar to soil layer, blast furnace slag with super large and durable steel waste and concrete structure which is construction waste And other residues.

In addition, between the upper portion of each treatment tank and the porous soil (7) layer is installed a capillary network (8) formed with a plurality of ventilation holes so that the porous soil (7) does not fall to the lower portion and the aeration to each treatment tank. Porous soil (7) layer is planted with a plant, such as grass (6) to have a condition for active microorganisms.

In the wastewater treatment step of each process, carbon compounds, phosphorus and nitrogen are treated in a first step (anaerobic reaction), and the wastewater is stored in the anaerobic sedimentation denitrification tank 1 through the inlet 15. The carbon compounds contained in the sewage water are converted into organic acids by the microorganisms attached to the surface of the filter medium (9), to prevent clogging due to solids in the filter medium (9) layer of the anaerobic sedimentation denitrification tank (1), In order to secure a large amount of microorganisms, the lower space 19 of the precipitation denitrification tank 1 is sufficiently left. In addition, in the anaerobic sedimentation denitrification tank (1), the denitrification reaction proceeds as well as the removal of the high concentration of carbon compounds, which is circulated to the sedimentation denitrification tank (1a) through the inner circulation pipe (14) at the rear end of the second aeration tank (4). Removal of nitrates occurs simultaneously in the return water. At this time, some of the carbon compounds in the influent sewage are used as carbon source for denitrification.

The second step (aerobic reaction) is performed by the first air aeration tank 2 consisting of two chambers: a first aeration tank 2a and a first aeration tank 2b 2b for giving up by the external air injection device 11; It consists of a sedimentation tank (3) for receiving the sewage and waste water treated by the microorganisms through the connecting pipe (18) to separate the solid-liquid. In the second stage, the organic matter remaining after the first stage is removed by the adherent microorganisms on the surface of the mediator 9 and by the floating microorganisms in the pores of the mediator 9. A part of the discharge water of the first aeration tank 2 is returned to the sedimentation denitrification tank 1a 1a located at the front end using the AP pump 17. In this way, in the sedimentation denitrification tank (1), since denitrification may occur simultaneously with organic decomposition, the natural filtration tank following the second aeration tank used as the denitrification tank in the conventional soil-coated contact oxidation tank does not need to be installed separately. . Simplification of the process by eliminating the natural filtration tank and reducing the total capacity is also a reason for returning a part of the second aeration tank 4 effluent to the sedimentation denitrification tank 1. The third stage (aerobic reaction) consists of a second aeration tank 4 for completely converting the ammonia remaining after the second stage to nitrate and a discharge tank 5 through which the purified water flows out. Nitrate in the second aeration tank (4) discharge water is returned to the anaerobic sedimentation denitrification tank (1) to the sedimentation denitrification tank (1) through the internal circulation pipe (14) to cause denitrification.

In addition, the porous soil (7) layer located above the sewage water purification device has a vegetation grass (6) is planted to maximize the activity of microorganisms in the soil, microorganisms present in the soil layer is an auxiliary function of purification of influent wastewater. Therefore, the processing efficiency of nitrogen or phosphorus is higher than those of other processes.

Up to about 1m below the soil surface, organisms such as plants, animals, and microorganisms live in a mutually interdependent relationship. When pollutants enter the porous soil (7) layer, the pollutants become nutrients of soil organisms and are decomposed and removed. . Ten million to hundreds of millions of microorganisms are inhabited in 1 ml of soil, and among the protozoa of soil, earthworms are very fond of sludge as commonly seen in general sewers. It has the ability to break down through the body. In addition, harmful bacteria in sewage and wastewater such as Escherichia coli exist as soil microorganisms and can be completely eliminated by feeding on microorganisms. Soil microorganisms become protozoa foods and these protozoa become nutrient sources of earthworms. . In addition, when the odor generated in the sewage and wastewater treatment facilities passes through the porous soil layer, the odor is adsorbed to the soil, and the adsorbed odorous substances are gradually converted into odorless substances by the soil microorganisms. When vegetation, such as grass, is grown on top of the soil layer, the pollutants in the soil are used as nutrients, so that the pollutants can be purified along with the soil, and in the case of the treatment plant, it can be used as a member of a landscape facility.

Figure 2 is a cross-sectional view for explaining the configuration of the automatic purification of sewage wastewater biodegradation of the present invention 1 sedimentation denitrification tank 1, sedimentation denitrification tank 2, 1 aeration tank 1 chamber, 1 aeration tank 2, a second aeration tank and discharge It can be confirmed that it is composed of a tank, and Figure 3 also shows a plan view for explaining the configuration of the wastewater purification apparatus of the present invention. 4 is a system treatment road for explaining the treatment system of the wastewater purification politics according to the present invention, the wastewater flows into the inlet 18, and the sedimentation denitrification (anaerobic), the first aeration (aerobic), sedimentation, the second aeration ( The process of the wastewater purification apparatus of the present invention, which is discharged through the outlet 16 of the discharge tank 5 and becomes the supernatant through the exhalation), is described.

The wastewater purification apparatus was tested under the conditions shown in Table 1 below.

In addition, the samples were taken while the above operation mode was tested and analyzed according to the Environmental Pollution Process Test Method and the American Public Health Association's standard method. The analysis method for each item of water quality analysis is shown in Table 2 below.

Operation mode I was operated without returning nitric oxide containing nitrate nitrogen (NO ₃ -N). In operation mode II, the residence time was extremely high using about 1/4 of the hydraulic retention time applied. It is to see how the processing efficiency changes when it is lowered. The residence time of operation mode III is about 1/2 of the residence time applied, but the amount of inflow wastewater itself (except return water) can be treated per unit time by this mode. Even if the nitric oxide was returned to be the same as the throughput, it was set up to confirm whether the treatment plant volume of the currently applied farming village can be used as it is without any change. Operation mode IV is intended to investigate the increase in treatment efficiency if the actual treatment capacity is reduced to 1/2 due to the return water, but is consistent with the current residence time of the sewage treatment plant.

The COD treatment efficiency (effluent concentration / influent concentration), which is the main removal material of the present invention by the above operation mode, was confirmed that 90% or more was removed except the operation mode I, and the results of the COD treatment rate are shown in Table 3. In addition, the treatment efficiency of nitrogen and phosphorus increased as the residence time increased to operation mode III and IV rather than operation mode II, and the treatment efficiency also increased. Also, the treatment of phosphorus rather than nitrogen by soil layer and vegetation grass covered in the upper part of the reactor was shown. The efficiency was higher. Table 4 and Table 5 show the results of treatment rates of nitrogen and phosphorus by the operation mode.

As described above, the soil-covered sewage treatment system according to the present invention can efficiently remove carbon compounds, nitrogen, and phosphorus simultaneously, and removes unnecessary oxidization tanks to be suitable for medium and small-sized wastewater treatment plants. Type sewage treatment system consists of three treatment tanks: sedimentation denitrification tank (1), first aeration tank (2), and second aeration tank (4), covering the porous soil (7) in the upper part of the purification device, and the grass (6). ) Is a nature-friendly process with vegetation, and the lower reaction tanks and the soil / grass on the upper side can interconnect to effectively remove nitrogen and phosphorus, including carbon compounds, and also cause abnormalities in the inflow water quality. Or microorganisms are supplied from the soil layer, which is the habitat of soil microorganisms, into the reactor when the microorganisms in the reactor die due to the failure of the air supply system. There is an excellent effect that the soil layer acts as a natural microbial culture tank.

Claims (6)

Sedimentation denitrification tank (1) in which sewage water introduced through the inlet participates in the anaerobic reaction; In the wastewater purification apparatus composed of three treatment tanks of the first aeration tank (2) to give up to the external air injection device for aerobic reaction and the second aeration tank (4) to increase the efficiency of the aerobic reaction, Each treatment tank is soil-coated sewage water purification device, characterized in that can be distributed to more than one compartment in order to increase the treatment efficiency of sewage water. The method of claim 1, wherein the filter material (9) in each treatment tank is filled with at least one selected from among crushed stone, roasted ocher pipe, blast furnace slag as steel waste, and residues from concrete structures as construction waste. Soil-covered sewage water purification equipment. The soil-coated sewage water purification apparatus according to claim 2, wherein a lower portion (19) space for securing microorganisms is formed at a lower end portion of the filter medium in each treatment tank. The internal circulation pipe (14) according to claim 1, characterized in that an internal circulation pipe (14) is provided as a conveying device for conveying a part of the discharged water of the first aeration tank (2) and the second aeration tank (4) to the sedimentation denitrification tank (1). Soil-covered sewage treatment system. 2. The soil according to claim 1, wherein a capillary network 8 having a plurality of ventilation holes formed in an upper layer of each treatment tank and a porous soil layer 7 formed above the capillary network 8, wherein plants are planted in the soil layer. Covered Wastewater Purification System Storing the introduced wastewater in the sedimentation denitrification tank (1); Aeration treatment of the sewage denitrified sewage water in the sedimentation denitrification tank (1) in the first aeration tank (2) through the air injection device (11); Separating the wastewater abandoned in the first aeration tank 2 into the sedimentation tank 3; The wastewater separated from the sedimentation tank 3 in the solid wastewater is abandoned in the second aeration tank 4 through the air injection device 11; In each of the above steps, a part of which is internally circulated to the settling denitrification tank 1 through an internal circulation tube 14 for final removal of nitrogen; And internal circulation catalytic oxidation of the soil-coated sewage water, characterized in that the sewage water which has become the supernatant water through each treatment step is discharged through the discharge tank (5).