KR100295499B1 - Sewage treatment equipment - Google Patents

Abstract

An object of the present invention is to provide a sewage treatment apparatus with economical and practicality by greatly improving the removal efficiency of nitrogen and phosphorus by changing some components while maintaining the existing facilities.

In order to achieve the above object, the present invention increases the flow rate of the incoming sewage by reducing the residence time, the primary sedimentation basin to ensure a large amount of organic matter;

An anoxic tank for performing a denitrification reaction to treat nitrogen;

Anaerobic bath inducing release of phosphorus from microorganisms;

An aeration tank for establishing an aerobic condition for carrying out excessive intake of phosphorus by the microorganisms and nitrification, which is a step prior to nitrogen treatment;

It is arranged in the order of secondary sedimentation basin to separate the treated water and sludge,

A stirrer respectively installed in the anoxic tank and the anaerobic tank to agitate the influent to prevent sludge settling;

An air supplier for supplying bubbles to the aeration tank;

A primary sedimentation basin treatment water distribution line for directly injecting sewage from the primary sedimentation basin into an anaerobic tank so as to supply organic matter necessary for promoting microorganisms when phosphorus is released from the anaerobic tank;

A sludge circulation line circulating to the anoxic tank to denitrify the nitrified sewage through the aeration tank;

A return line for returning the sludge sewage submerged in the secondary sedimentation basin to the anaerobic tank;

A final treated water discharge pipe for discharging the treated water located at the upper portion of the secondary sedimentation basin;

The waste sludge discharge line for returning a portion of the sludge sewage sinking to the bottom of the secondary sedimentation basin to the anaerobic tank to discharge the rest to the outside.

Description

Sewage treatment equipment

The present invention relates to a sewage treatment apparatus for purifying sewage discharged from a general household, wastewater discharged from a factory, and general sewage generated in a city.

In countries where water resources are scarce, artificial lakes created by constructing various dams are used as important water sources.However, due to rapid development policies and industrialization, domestic sewage and factory wastewater flow into rivers and flow into lakes used as water resources. By causing eutrophication, the water quality is rapidly deteriorated, threatening the drinking water source, and the polluted water flows into the sea, causing red tide, etc., causing a lot of damage to coastal aquaculture.

For this reason, sewage treatment plants are installed to purify domestic sewage or factory wastewater, and discharged to rivers to prevent contamination of rivers and lakes.

However, the sewage treatment method of the sewage treatment plant currently adopted in Korea adopts biological oxygen demand, that is, activated sludge method for treating organic and suspended substances, commonly referred to as BOD, and it is a river by eutrophication due to lack of nitrogen and phosphorus treatment. The deterioration of water quality is inevitable.

The most economical methods for removing nitrogen and phosphorus, the causative agent of eutrophication, include the so-called A20 process, the VIP process according to US Pat. No. 4,867,883, the Bardenpho process according to US Pat. No. 3,964,998, etc. This is known.

However, these methods are suitable methods under the well-equipped sewage management system, but as the distribution rate of sewage pipes is low and the sewage drainage system is mainly combined as in Korea, there is a problem that it is not suitable for the water quality characteristics of low organic matter content of sewage.

In Korean Patent Publication No. 95-31,935, the zeolite filter paper to which nitrification microorganisms are attached is installed in the final treated water outlet of the existing activated sludge process, and the operation method of the filter paper is composed of a top-down, bottom-up, inflatable or fluid filter paper. The process of nitrogen and phosphorus treatment by chemical treatment method that installs backwash device is presented.

However, in the above method, when the solid and the liquid are separated by the secondary sedimentation basin, the upper effluent has almost no organic matter remaining. Therefore, the number of nitrifying microorganisms is small or the existence of the nitrate is questioned. The treatment can be performed only by ion exchange. In this case, since the cation form of the unoxidized ammonia nitrogen (NH ₄ ⁺ ) and the anion form of nitrogen nitrate (NO ₃ ⁻ ) in the form of nitrogen present in the sewage coexist, the ion can be removed simultaneously. Exchange resin is required, but since natural zeolite is mainly represented by alkaline earth metal, only ammonia nitrogen is removed. In addition, it is pointed out that there is no provision for the phosphorus component that causes green algae and red tide even at a much lower concentration than nitrogen because it is impossible to process nitrogen and phosphorus phosphorus in the sewage at the same time.

In order to make up for such drawbacks, Korean Patent Publication No. 96-10,551 discloses a process for biological treatment in parallel with chemical treatment.

In this manner, the phosphorus component is biologically treated, and the nitrogen component is combined with the biological treatment by chemical treatment with zeolite to which the nitrifier is attached. However, in the above method, since sewage itself is composed of high concentration of suspended solids, zeolite filter paper is frequently clogged, and the sewage treatment operation is often stopped, and a backwashing facility is necessary to control this. In order to perform the washing, since the loss of zeolite occurs, not only the zeolite consumption is increased, but also an additional reaction device is required to install an additional reaction device in order to regenerate the zeolite. In addition, since the regeneration treatment of zeolite is made of waste acid and waste alkali treatment, there is a problem of secondary pollution.

Meanwhile, Korean Patent Publication No. 96-22,286 discloses an anaerobic tank → anoxic tank → aeration tank while maintaining the so-called A20 process disclosed in US Patent Publication No. 4,056,465 by Air Products & Chemicals of the United States. A treatment process is proposed to prevent the short-circuit phenomenon by attaching the filter filler to the filter medium and to attach the microorganisms to the filter filler to increase the nitrification and denitrification efficiency.

However, the attached microorganism method is advantageous for securing microbial population because filled media acts as a habitat for microorganisms, but desorption of attached microorganisms occurs due to shear force caused by agitation of sewage and movement of media. The microorganisms inhabiting the filter filling in the area are weak in adhesion because most of the microorganisms in the endogenous breathing stage, and due to the lack of cohesiveness, they are easily released into the fine suspended matter in the secondary settling basin. As a result, it is well known that turbidity of the final treated water is lowered and water deterioration is more likely to occur, and since it is not possible to artificially control the amount of microorganisms attached to the filter medium, the ability to cope with the impact load is reduced, and compliance with the impact load is caused. The drawback is that it takes too long.

In addition, according to Korean Patent Laid-Open Publication No. 96-22,287, using the same process as Korean Patent Publication No. 96-22,286, it is proposed to operate the first step in an anaerobic tank and the second step in anaerobic tank.

However, anaerobic tanks and anaerobic tanks are classified according to whether the material to be treated is nitrogen or phosphorus. It is logically logical to change anaerobic tanks to anaerobic tanks and anaerobic tanks under the same conditions. There is a possibility that a partially anaerobic state is formed inside the accumulated sludge, and the absorbed phosphorus may be released again. When circulated in this state, the anoxic tank simultaneously releases phosphorus and denitrification reactions. There is a disadvantage that the removal rate is lowered.

Another Korean Patent Publication No. 96-10,918 discloses a process for treating nitrogen and phosphorus by consisting of an anaerobic tank → anoxic tank → phosphorus absorption tank → sedimentation tank → nitrification tank → sedimentation tank and three return pipes.

However, the process is too complicated to distinguish between the desorption tank and the nitrification tank because there is no way to distinguish between denitrification microorganisms and dephosphorus microorganisms.

In addition, according to the theory of nitrogen and phosphorus treatment, anaerobic tank → aeration tank for phosphorus treatment, and aeration tank → anaerobic tank for nitrogen treatment, anaerobic tank → phosphorus absorption tank → sedimentation tank → anaerobic tank → nitrification tank → It is difficult to satisfy the phosphorus and nitrogen treatment at the same time because it is effective to form in the settling tank.

In addition, when the sludge, which is the activated microbial mass in the settling tank, is separated into solid-liquid, nitrifying microorganisms are also excluded. In the nitrification tank installed at the rear of the settling tank, not only the population of microorganisms but also the food is insufficient, so the growth conditions of the nitrifying microorganisms are poor. This demerit has been pointed out.

According to U.S. Patent Publication No. 5,733,455, which discloses another phosphorus-nitrogen treatment process, it consists of a spraying tank (microbial habitat) → anoxic tank (anaerobic tank) → aeration tank → a settling tank, and the organic matter necessary for denitrification and phosphorus release at the inlet of the anoxic tank. It suggests the process of external input.

However, in the anoxic tank for simultaneous denitrification and phosphorus release reaction, phosphorus is difficult to release due to the increase in the oxidation-reduction potential difference due to nitrate oxygen and deterioration of anaerobic state. Phosphorus removal capacity tends to be reduced because it is consumed, and organic matter existing in existing sewage is removed from the sedimentation tank installed in the middle, and there is a need to replenish insufficient organic matter. In this case, sufficient organic material for denitrification can be maintained, so an appropriate level of treatment efficiency can be maintained. However, since additional organic materials must be purchased and added, operation and maintenance costs are increased. The disadvantage may arise that there is a risk of causing secondary pollution.

Accordingly, the present invention has been proposed in view of the above-mentioned problems, and its object is to improve the efficiency of removing nitrogen and phosphorus by changing a part of the structure while maintaining an existing facility. To provide.

In order to achieve the above object, the present invention increases the flow rate of the incoming sewage by reducing the residence time, the primary sedimentation basin to ensure a large amount of organic matter;

An anoxic tank for performing a denitrification reaction to treat nitrogen;

Anaerobic bath inducing release of phosphorus from microorganisms;

An aeration tank for establishing an aerobic condition for carrying out excessive intake of phosphorus by the microorganisms and nitrification, which is a step prior to nitrogen treatment;

It is arranged in the order of secondary sedimentation basin to separate the treated water and sludge,

A stirrer respectively installed in the anoxic tank and the anaerobic tank to agitate the influent to prevent sludge settling;

An air supplier for supplying bubbles to the aeration tank;

A primary sedimentation basin treatment water distribution line for directly injecting sewage from the primary sedimentation basin into an anaerobic tank so as to supply organic matter necessary for promoting microorganisms when phosphorus is released from the anaerobic tank;

A sludge circulation line circulating to the anoxic tank to denitrify the nitrified sewage through the aeration tank;

A return line for returning the sludge sewage submerged in the secondary sedimentation basin to the anaerobic tank;

A final treated water discharge pipe for discharging the treated water located at the upper portion of the secondary sedimentation basin;

The waste sludge discharge line for returning a portion of the sludge sewage sinking to the bottom of the secondary sedimentation basin to the anaerobic tank to discharge the rest to the outside.

1 is a view showing a sewage treatment apparatus according to the present invention

※ Explanation of codes for main parts of drawing

2: primary sedimentation basin

3: anoxic tank

4: anaerobic maturation

5: aeration tank

6: air supply

7: secondary sedimentation basin

9,10: Stirrer

11: Waste Sludge Discharge Line

12: final treated water discharge line

13: Return Line

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings.

1 is a view showing a sewage treatment apparatus according to the present invention, 1 is a sewage inlet pipe for introducing sewage into the primary sedimentation basin (2).

In the case of sewage generated in Korea, it is a low-load sewage that lacks organic materials for nitrogen and phosphorus treatment. Therefore, when reducing the load on the subsequent process by increasing the capacity of the primary sedimentation basin (2) as in the conventional treatment process, denitrification Since the organic matter necessary for the growth of the denitrifying bacteria causing the reaction and the dephosphorizing bacteria causing the dephosphorization reaction is insufficient, the primary sedimentation basin (2) of the present invention is designed to have a smaller capacity than the conventional one and to increase the flow rate of the sewage, thereby increasing the primary sedimentation basin. (2) By reducing the residence time in the soil, only suspended solids and contaminants with high settling speeds can be removed, and the organic matters settled down can be suppressed as much as possible. This allows the subsequent processes to establish the conditions necessary for the growth of denitrification and dephosphorus microorganisms, i.

The oxygen-free tank 3 is responsible for the purification of the nitrogen component in the sewage along with the aeration tank 5 which is a subsequent treatment process.

Ammonia nitrogen (NH ₃ -N), a form of nitrogen that accounts for most of the nitrogen in the influent sewage, is reacted with oxygen supplied through the air supply (6) of the aeration tank (5) and nitrosamonas is a microorganism contained in a large amount in the organic matter. It is oxidized by (Nitrosomonas) to be converted to nitrous nitrogen (NO ₂ -N), the nitrite nitrogen is converted to nitrate nitrogen (NO ₃ -N) by the decomposition of the microorganism Nitrobaactor (Nitrobactor).

After such a change in nitrogen form is carried out in the aeration tank, part of the sewage is returned to the anoxic tank 3 of the preceding process via the sludge circulation line 8 while being transferred to the secondary sedimentation basin 7.

The sewage containing nitrogen components in the form of nitrate nitrogen (NO ₃ -N) by the reaction in the aeration tank 5 causes denitrification reaction in the oxygen-free tank 3.

Denitrification is carried out by random microorganisms, heterotrophic microorganisms, which occupy most of the natural water system. The electron transfer system uses organic matter as the reduced electron donor and oxygen, nitrate nitrogen, and sulfate ion as the final oxidized electron acceptor. Each electron acceptor reacts with organic matter in the sewage in order of oxygen> nitrogen nitrogen> sulphate ions, so if there is no oxygen, that is, in the absence of oxygen, the microorganisms are electron acceptors. In the radical, chemically bound oxygen is used to breathe, so nitrate nitrogen (NO ₃ -N) is deprived of oxygen in microbial respiration and finally free nitrogen is present. It will fly away and get rid of the nitrogen in the sewage.

If the phenomenon appearing in each (5) (3) is expressed by the reaction equation as follows.

1) Reaction formula in aeration tank (5)

2) Reaction formula in anoxic tank (3)

As can be seen from the reaction scheme, the pollutant of the nitrogen system included in the sewage is decomposed into water (H ₂ O) and nitrogen (N ₂ ) in the anoxic tank (3) through a cycle from the aeration tank (5) to the anoxic tank (3). Since nitrogen, which is a gas, is blown off into the atmosphere, most of the ammonia nitrogen present in the sewage can be treated.

For nitrogen treatment only, the aeration tank → anoxic tank should be arranged in the order of the reaction scheme, but in this case, since the microorganisms are placed in the second half of the endogenous respiratory tract, solid-liquid separation does not occur in the secondary sedimentation basin (7). In order to solve this problem, in the present invention, the anaerobic tank 3 is first installed, and the aeration tank 5 is installed thereon to circulate the sewage so that the solid-liquid separation in the secondary sedimentation basin is made smoothly.

In other words, when the nitrified effluent from the aeration tank (5) is recycled to an anoxic tank (3) to cause denitrification to treat nitrogen, and to treat phosphorus in the anaerobic and aeration tanks, the simultaneous treatment efficiency of nitrogen and phosphorus is maximized, and the solid-liquid separation is also smooth and clean. Treated water can be discharged. Reference numerals 9 and 10 in the drawings are stirrers that rotate and stir so that the sewage and microorganism equalization of the entire treatment tank 3 and 4 and sludge containing a large amount of microbial masses are evenly distributed in the sewage without sedimentation.

On the other hand, an anaerobic tank 4 is provided between the aerobic tank 3 and the aeration tank 5 for the treatment of phosphorus together with the aeration tank 5.

Phosphorus content contained in microorganisms in the cell is about 1.5 to 2% by dry weight ratio, and the existing activated sludge method can remove only the amount of phosphorus necessary for cell synthesis, resulting in low phosphorus treatment efficiency.

However, when anaerobic conditions are followed by aerobic conditions, the intake of microorganisms exceeds the theoretical requirement for microbial cell growth, and according to the biological mechanism that the intracellular phosphorus content reaches 4-12% (drying weight ratio). Anaerobic tank → aeration tank arranged in order from the aeration tank (5) to the oxygen-free tank (3) nitrate acid sewage process and anaerobic tank and aeration tanks are installed in sequence, so that the order of the reaction and the return of sewage tanks without any major structural changes By modifying the system to meet the optimum conditions of nitrogen and phosphorus treatment simultaneously, it is possible to greatly improve the efficiency of nitrogen and phosphorus removal treatment.

In the anaerobic tank (4), soluble biological requirements (BOD) present in sewage are converted to short chain fatty acids (SCFAs) such as acetate by random microorganisms by fermentation reactions, and the resulting lower fatty acids are acinetovectors. It is broken down by a microorganism called Acinetobacter, and phosphorus is released by using energy generated through hydrolysis of carbohydrates (polyphosphates) stored in cells.

When phosphorus is released, lower fatty acids are converted into PHB (Poly-β-hydroxy butyrate) and accumulate in cells.

After this reaction, when the sewage is passed from the anaerobic tank (4) to the aeration tank (5), aerobic conditions are formed by oxygen supplied through the air supply (6), and the carbohydrate is regenerated as the PHB accumulated in the cells of the microorganism is oxidized. At this time, microorganisms ingest excess phosphorus. That is, because the anaerobic tank (4) is absorbed in the aeration tank (5), which is several times more phosphorus than the amount of phosphorus released under stress, the content of phosphorus in the sewage is sharply reduced.

In this way, the microorganisms ingesting excessive phosphorus are transferred to the secondary sedimentation basin (7), which is contained in sewage water (but as described above, some sewage is circulated to an anaerobic bath), and thus within the secondary sedimentation basin (7). The sediment is deposited on the bottom, and discharged to the outside through the waste sludge discharge line 11 to be treated separately, and the treated water (cleaned sewage) located at the top of the secondary sedimentation basin 7 is the final treated water. The discharge pipe 12 is discharged to the river or the like.

On the other hand, if all the sludge is discharged through the waste sludge discharge line 11, the microorganisms for nitrogen and phosphorus treatment is insufficient, the expensive microorganisms must be continuously replenished and supplied to the anaerobic tank (4) and aeration tank (5) This leads to an increase in operating costs.

For this reason, in the present invention, part of the sludge is returned to the anaerobic tank 4 through the return line 13 to prevent the loss of artificially activated microorganisms and to secure the population of microorganisms required for nitrogen and phosphorus treatment in the previous process. .

At the same time, the entire amount of sewage flowing into the primary sedimentation basin (2) is introduced into the anaerobic tank (4) through the primary sedimentation basin treatment water distribution line (15) without introducing the entire amount of sewage into the anaerobic tank (3). Increase the supply of organics.

As described above, the present invention is composed of an anaerobic tank → anaerobic tank → aerobic tank → aerobic tank → aeration tank instead of the aerobic tank adopted in the conventional nitrogen and phosphorus treatment process, and returns the nitrate sewage from the aeration tank to the anoxic tank, and the primary sedimentation basin. In order to minimize the precipitation of organic matter, some of the sewage flowing into the anaerobic tank is bypassed to the anaerobic tank and directly introduced into the anaerobic tank, and the sludge of the secondary settler is returned to the anaerobic tank, and Part of the anaerobic tank is completely removed and the nitrate nitrogen in the sewage is completely removed and then flowed into the anaerobic tank to release phosphorus smoothly, resulting in a high denitrification and dephosphorization effect.In particular, the anaerobic tank is installed at the end of the anaerobic tank so Even if the concentration of nitrate nitrogen in raw water is high The rate is stable. In addition, since it is possible to secure microorganisms and organics useful for sewage treatment, the dephosphorization and denitrification microorganisms can be easily grown, and thus, nitrogen and phosphorus can be efficiently treated even at low loads with low organic content.

Claims (1)

A primary sedimentation basin to secure a large amount of organic matter by reducing the residence time by increasing the flow rate of inflowing sewage; An anoxic tank for performing a denitrification reaction to treat nitrogen; Anaerobic bath inducing release of phosphorus from microorganisms; An aeration tank for establishing an aerobic condition for carrying out excessive intake of phosphorus by the microorganisms and nitrification, which is a step prior to nitrogen treatment; It is arranged in the order of secondary sedimentation basin to separate the treated water and sludge, A stirrer respectively installed in the anoxic tank and the anaerobic tank to agitate the influent to prevent sludge settling; An air supplier for supplying bubbles to the aeration tank; A primary sedimentation basin treatment water distribution line for directly injecting sewage from the primary sedimentation basin into an anaerobic tank so as to supply organic matter necessary for promoting microorganisms when phosphorus is released from the anaerobic tank; A sludge circulation line circulating to the anoxic tank to denitrify the nitrified sewage through the aeration tank; A return line for returning the sludge sewage submerged in the secondary sedimentation basin to the anaerobic tank; A final treated water discharge pipe for discharging the treated water located at the upper portion of the secondary sedimentation basin; And a waste sludge discharge line for conveying a portion of the sludge sewage that sinks to the bottom of the secondary sedimentation basin to the anaerobic tank and then discharging the remaining sludge to the outside.