KR20010083723A - Method of eliminating phosphorus and nitrogen from disposal sewage - Google Patents

Abstract

PURPOSE: Provided is a method for removing nitrogen and phosphorous in wastewater, which is modified from activated sludge process and A2O process. This process is characterized by adding the conditions such as a phosphorous release tank and a denitrification tank in a nitrification tank. CONSTITUTION: The process is composed of the following parts: a phosphorous release tank (1); a denitrification tank (2); a nitrification tank (3); a baffle wall (4); an anoxic tank (5); a settling tank (6); an inner return pipe (7); and an outer return pipe (8). The baffle wall is installed for maximizing the denitrification rate by decreasing DO of inner return sludge. The process can treat 90% of BOD, 75% of TN and 75% of TP, respectively.

Description

Method of eliminating phosphorus and nitrogen from disposal sewage

The present invention relates to a sewage treatment method, and adds a phosphorus discharge tank and a denitrification tank condition to a sewage treatment plant nitrification tank so as to treat nitrogen and phosphorus compounds, which are the largest water pollution in the sewage and organic wastewater flowing into the sewage treatment plant. The present invention relates to a method for removing phosphorus and nitrogen in sewage treatment, which is invented to remove nitrogen and phosphorus simultaneously by using characteristics of nitrifying and denitrifying bacteria.

Currently, the regulation of nitrogen and phosphorus is required to discharge less than 60mg / l of nitrogen and less than 8mg / l of phosphorus in sewage terminal treatment facilities.Since 2000, the discharged water quality standards have been strengthened further, so that nitrogen 20mg / l and phosphorus 1mg / It is supposed to regulate less than ℓ. Therefore, this treatment method has been developed phosphorus and nitrogen removal method suitable for sewage end treatment facilities and livestock wastewater joint treatment facilities since 2000.

The present invention has been invented in view of the above problems, and was developed for the convenience of maintenance by removing nitrate nitrogen in the return sludge and ammonia nitrogen in the influent. Therefore, the influent can be introduced into the phosphorus discharge tank, denitrification tank, and nitrification tank to facilitate the supply of organic materials required for denitrification, and the internal and external conveying sludge can also be supplied to both the phosphorus discharge tank, the denitrification tank, and the nitrification tank. It can prevent nitrification rate due to water temperature decrease during cultivation and winter operation, and cope with on-site conditions under overload or low load, and also keep nitrifying bacteria in nitrification tank at high concentration, so it can break down nitrifying bacteria in treatment plant that is not nitrifying well. By culturing it will be able to remove nitrogen and phosphorus.

1 is a process diagram of phosphorus, nitrogen treatment of the present invention.

<Description of Signs for Main Parts of Drawings>

1: phosphorus release tank, 2: denitrification tank, 3: nitrification tank, 4: diaphragm, 5: anoxic bath,

6: sedimentation tank, 7: internal conveying line, 8: external conveying line,

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to each step according to the phosphorus, nitrogen treatment process diagram shown in Figure 1 as follows.

Conventional sewage treatment by the pretreatment process to remove and equalize the solid contaminants in the incoming sewage and wastewater, and biological or physical processes that simultaneously perform nitrification, denitrification, and dephosphorization in biological reactions. In the processing apparatus,

First stage

Inflow of sewage and wastewater and the sludge returned from the final sludge settling tank are in contact with the polymer organic matter introduced by the low-molecular anaerobic microorganisms so that the denitrified microorganisms can easily absorb the organic matter and at the same time the organic matter by the phosphorus-removing microorganism A phosphorus discharge tank 1 for causing absorption and phosphorus release phenomena;

2nd step

The denitrification microorganism causes the denitrification reaction by using the low molecular weight organic material and the internally conveyed nitrate in the phosphorus discharge tank (1). Maintaining the N (organic substance / total nitrogen) ratio depends on the degree of denitrification, and the denitrification tank 2 for stabilizing the nitriding reaction in the aeration tank since the Alkalinity is increased incidentally;

3rd step

The waste and wastewater that passed through the denitrification tank converts ammonia nitrogen in the water into nitrate nitrogen by nitrifying microorganisms under aeration conditions, and at the same time, reduces phosphorus concentration in water through the phosphorus excess absorption reaction by the phosphorus removing microorganism. Nitrification tank (3) to serve to make;

4th step

In the nitrification tank (3) is reduced to install a diaphragm (4) at the end to maximize the denitrification rate DO of sludge conveyed internally to the anoxic tank (5),

5th step

Phosphorus discharge denitrified sewage through the nitrification tank is solid-liquid separated before being discharged from the settling tank (6) to maintain the MLSS (microbial) concentration of the bioreactor through the lower return line and the treated water is discharged;

A device for returning the treated water oxidized with nitrate nitrogen to an anaerobic tank, anoxic tank, and aeration tank in the nitriding tank, and is mainly introduced into the anoxic tank (5) when denitrification is carried out to nitric acid (NO ₃ ) or nitrite group (NO ₂ ). An internal conveying line 7 which serves to change nitrogen gas into nitrogen gas by denitrification microorganisms;

6th step

External conveying line for conveying to maintain the MLSS of the phosphorus discharge tank (1), denitrification tank (2), and nitrification tank, and if necessary to be returned to the nitrification tank for maximum nitrification reaction in the nitrification tank (8) It is a process that can selectively control and manage the phosphorus release and denitrification of sewage and wastewater.

According to the present invention as described above, when the sewage and waste water are introduced into the phosphorus discharge tank 1 after the pretreatment process, the phosphorus releases phosphorus in the anaerobic state of the activated sludge of the phosphorus discharge tank 1.

The principle of biological removal of phosphorus released in the anaerobic state will be described first.

In standard activated sludge processes, phosphorus is mainly removed by the growth, precipitation, adsorption, etc. of microorganisms. Phosphorus removal efficiency is about 30% in sprinkling method, 10-30% in ash disc method and 30-50% in standard activated sludge process. Phosphorus content of the sludge is 1-2% and above, it can be judged that abnormality of phosphorus metabolism necessary for microbial growth is removed. Phosphorus is required for the growth of microorganisms in small amounts compared to carbon or nitrogen. Therefore, it is possible to obtain satisfactory results by the method of cell synthesis and to obtain satisfactory results. Phosphorus can be effectively removed more than the biochemical equivalent required for.

Phosphorus in sewage is usually present in the form of inorganic and organic phosphorus. Inorganic phosphorus is further divided into orthophosphate and polyphosphate in the form of PO ₄ ^3- . In water, macromolecular phosphate can be hydrolyzed in the form of phosphate, and phosphate is converted into macrophosphate and stored in cells. If microorganisms in activated sludge are temporarily deprived of one or more important elements such as nitrogen, phosphorus, sulfur or oxygen, normal metabolic processes will not work and will be under severe stress. Some microorganisms cannot tolerate this, while others use other metabolic pathways. In this case, microorganisms need a special survival mechanism, and phosphorus is in the form of Poly-P (polymer phosphorus), and carbon accumulates in Poly-ß-Hydroxy Butyrate (PHB) to seek survival. The eggplant compound has a low solubility in water and does not affect the osmotic pressure in the microorganism. The removal of phosphorus by biological means is the accumulation of high concentrations of phosphorus in activated sludge. This is due to the phenomenon that activated sludge releases phosphorus in anaerobic state and excessive intake of phosphorus in aerobic state. Herein, phosphorus release refers to converting and storing organic acids ingested into PHB (Poly-ß-Hydroxy Butyrate) using energy generated when decomposing Poly-P (polymer phosphorus) accumulated in cells under anaerobic conditions. It is the phenomenon of releasing free orthophosphoric acid (Ortho-P) into the solution, and under anaerobic conditions, under aerobic conditions, it decomposes PHB stored in the cell to synthesize ATP (adenosine triphosphatase), and from this solution After ingesting an excessive amount of acid, which is synthesized with Poly-P and stored in cells, this phenomenon is called overingestion of phosphorus. The most important factor in biological removal is to maximize carbon storage in the anaerobic state, which requires substrates to be applied in the aerobic state and oxygen sources to be minimized. The mechanism of biological excess phosphorus removal has been studied by Levin and Shapiro et al. Until recently, biochemical models have been proposed by scholars in various fields.

Looking at the background and phosphorus removal influencing factors for the phosphorus discharge made in the phosphorus discharge tank 1 of the present invention as follows.

1) Background on phosphorus discharge from phosphorus discharge tank

Phosphorus-removing microorganisms continue to ingest organic acids such as acetic acid using energy generated by hydrolysis of Poly-P accumulated in cells in the absence of oxygen or nitric oxide, and convert them into PHB to store them in cells. Have. Normal phosphoric acid produced by the decomposition of inorganic phosphorus is stored in cells or released into the solution when concentration differences occur. Acetic acid is ingested by microorganisms in the form of acetic acid when an appropriate pH difference exists inside and outside the cell, and it quickly decomposes to become an acetic acid, thus reducing the constant pH difference. At this time, since the cell has a function of regenerating the lost pH, it is possible to continuously ingest the acetic acid while maintaining a constant pH difference at all times. Three factors are responsible for regenerating attenuated pH in and out of cells in anaerobic conditions.

First, ATP is decomposed by APT-ase (Adenosine Triphosphatase) enzyme attached to the cell wall and becomes ADP (Idenosine Diphosphate), which releases hydrogen ions;

Second: NADH (nicotine imide adenine dinucleotide hydrogen) is consumed by the hydrogen ion transfer enzyme in the cell wall, and it has the function of releasing hydrogen ions out of the cell. According to Comeau et al. The energy generated as a result of the decomposition of phosphorus is used to form Acetyl-CoA, which is fed through the TCA (citric acid) circuit;

Third: When the ratio of ATP / ADP adenosine triphosphate / adenosine diphosphate is low when Poly-P is decomposed, ATP is produced, and hydrogen ions are released by the same principle as the first function to maintain pH difference. . However, according to Mino et al., Since the TCA (citric acid) circuit does not work during the anaerobic reactor, NADH is generated and supplemented when glycogen accumulated in the cell is decomposed by Glycolysis. Therefore, biochemical release under anaerobic conditions is achieved in Table 1.

2) Phosphorus Removal Influence Factor

Factors influencing phosphorus removal treatment method are related to influent wastewater characteristics, treatment method design factors and operation method. environmental factors such as pH, solids residence time (SRT) and design variables such as anaerobic and aerobic bath residence times, formations in influent sewage, levels of VFAs (volatile fatty acids), and nitrate nitrogen concentrations. In terms of their effects, the study of DO (dissolved oxygen) concentrations affecting phosphorus removal maintains a minimum concentration of 2 mg / l in the aerobic bath, which is the minimum concentration for microorganisms to ingest enough phosphorus, and release of phosphorus. In the phosphorus discharge tank 1, which is a stage, it is necessary to create a condition in which DO (polyoxygen) concentration does not exist.

Therefore, according to the selection of treatment process, an appropriate SRT (sludge residence time) for phosphorus removal should be selected and an appropriate combination of anaerobic residence time and aerobic residence time should be appropriately selected.

In this way, the wastewater is discharged phosphorus by the activated sludge into the phosphorus discharge tank (1) anaerobicly and then goes to the denitrification tank (2) to denitrify by anoxic.

Denitrification of the denitrification tank (2) refers to a process of reducing nitric acid or nitrous acid produced in nitrification to nitrogen gas by a microorganism using an electron acceptor. The procedure is as follows.

NO ₂ ^-- N N ₂

In addition, nitrates, nitrites, sulfates, and ferric ions, in addition to oxygen, may be used as electron acceptors in the oxidation process by NADH (nicotinamide adenine dinucleotide hydrogen) in the electron transport system. . The use of bound oxygen here is called anaerobic respiration, and this environment is usually called anoxic. The most common electron acceptor other than oxygen is the nitrate (Nitrate) This cytochrome: NO ₂ by the reducing agent to be reduced by the (Cytochrome pigment protein acting on the oxidation-reduction of the ^cell) is reduced to N ₂ via a, N ₂ O. And the reduction potential needed to reduce nitrate to nitrite is + 0.4V, whereas the reduction potential of O ₂ is + 0.8V, which is more oxidative by O ₂ than nitrate. In the case of sufficient polyoxygen, denitrification by the microorganism, ie reduction of nitrate, is greatly inhibited. In general, when methanol is used as the organic carbon source, the denitrification process is represented by the following Chemical Formula 1.

^{_{NO 3 - + 0.833CH 3 OH +}} 0.167H 2 CO 3 - -> 0.5N 2 + 1.33H 2 O + HCO 3

Denitrification bacteria include Pseudomonas, Micrococcus, Archromobacter, Bacillus, and others. Since these microorganisms are facultative heterotrophic microorganisms, denitrification does not occur because dissolved oxygen is used as an electron acceptor. . McCarty expressed the amount of methanol (Cm) required when methanol is used as organic carbon for denitrification, as shown in the following formula (2).

^{_{Cm = 2.47NO 3 - - N +}} 1.53NO 2 - - N + 0.87DO

As can be seen from the above equation, Alkainity is generated during denitrification, and 3.57mg of Alkainity, expressed as CaCO ₃ per 1mg of nitrate or nitrite, is produced. In actual experiments, however, Alkainity of 2.95-2.89mg is produced. The denitrification process of nitrate nitrogen or nitrite nitrogen and the synthesis formula of denitrification microorganism are shown in Table 2.

As described above, the denitrification tank 3 causes denitrification microorganisms to cause denitrification by using the low molecular weight organic material and the internally conveyed nitrate in the phosphorus discharge tank 1, and at this time, a considerable amount of organic source is compared with the amount of nitrification introduced. Therefore, maintaining an appropriate C / N (organic substance / total nitrogen) ratio for this depends on the degree of denitrification, and as an incidental increase of alkali, it also involves stabilizing the nitrification reaction in the aeration tank. .

The sewage and wastewater which passed through the denitrification tank flows back into the nitrification tank 3 and converts ammonia nitrogen in the water into nitrate nitrogen under aeration conditions, and at the same time, absorbs phosphorus excess by the phosphorus removing microorganism. The reaction serves to reduce the concentration of phosphorus in water.

The present invention phosphorus discharge tank (1) Denitrification tank (2) Phosphorus discharge and denitrification through the nitrification tank (3), and then the sludge is solid-liquid separated from the settling tank (6) to discharge the treated water in the upper part and the sludge settled in the lower part is disposed of through the outlet or external conveying line (8) By selectively returning to the phosphorus discharge tank (1), denitrification tank (2), nitrification tank (3) as necessary to maintain the MLSS (microorganism).

When aeration is carried out in the nitrification tank 3 to stabilize the nitrification reaction, when the quality of the phosphorus is determined to be insufficient or the concentration of sewage flowing into the phosphorus discharge tank 1 is high, the internal conveying line 7 is opened. The treated water of the anoxic tank (5) installed at the end of the nitrification tank is returned through the phosphorus release process again, and when the growth of the microorganisms in the phosphorus discharge tank (1) is necessary, the external conveying line (8) By opening the valve of), the sludge of the sedimentation tank 6 is introduced to remove phosphorus as the microorganisms grow.

As such, the sewage from which phosphorus is removed from the phosphorus discharge tank 1 is denitrified microorganisms cause denitrification reaction using the low-differentiated organic material and internally conveyed nitrification material from the denitrification tank 2, and the amount of nitrification introduced therein Compared to this, since a considerable amount of organic sources are required, denitrification is maintained by maintaining an appropriate C / N ratio for this purpose, and alkali (Alkalinity) is incidentally increased, thereby acting to stabilize nitrification in aeration of the nitrifier.

In the denitrification tank 2, the denitrification effect is carried out by selectively bringing in the water of the anoxic tank 5 or the sludge of the settling tank 6 by operating the valves of the inner conveying line 7 and the outer conveying line 8 according to the degree of denitrification. To increase.

The sewage denitrified in the denitrification tank is moved to the nitrification tank 3 and aerated by air generated from the nozzle at the bottom. The nitrification tank simultaneously converts ammonia nitrogen in the water into nitric acid nitrogen by nitrifying microorganisms under the aeration conditions. Phosphorus removal acts to reduce the degree of race in water through the phosphorus excess absorption reaction by microorganisms.

In the nitrification tank 3, the valves of the inner conveying line 7 and the outer conveying line 8 are selectively opened as necessary, such as the phosphorus discharge tank 1 and the denitrification tank 2, so that ammonia nitrogen is nitrate. It creates environmental conditions that allow it to be oxidized with nitrogen.

In addition, the anoxic tank 5 on one side of the diaphragm 4 of the nitrification tank 3 reduces DO of the sludge conveyed inside to maximize the denitrification rate.

As above, wastewater and wastewater discharge tank (1) Denitrification tank (2) Through the nitrification tank 3, the treated water oxidized to phosphorus release, denitrification, and ammonia nitrogen to nitric acid finally solidifies and precipitates sludge in the settling tank 6, and then discharges the constant located at the top.

The experiment was performed as follows with respect to the phosphorus and nitrogen processing method of this invention implemented as mentioned above.

This experiment was conducted on the influent of sewage treatment plant in industrial area which has different inflow water quality than other sewage treatment plants.

end. Analytical Method

PH, Temp (temperature), ORP (redox unit), DO (dissolved) for influent, phosphorus discharge tank, denitrification tank, nitrification tank and effluent in order to check the operation status and treatment efficiency for the treatment process operation of the present invention. Oxygen), CODcr (chemical oxygen demand), BOD (biochemical oxygen demand), MLSS (microorganism), MLVSS (volatile solids), SVI (sludge capacity indicator), SS (sustained substance), TKN (total nitrogen), NH ₄ ⁺ -N (ammonia nitrogen), NO ₃ ^-- N (nitrogen nitrogen), NO ₂ ^-- N (nitrogen nitrogen), TP (total phosphorus), Alkalinity (alkalinity) and the like were analyzed. Samples were taken every day at each sampling site, and microorganisms were observed in addition to the above analysis items. At this time, an analysis experiment was performed immediately after sampling to minimize the change in the appearance of the sample, and an immediate sampling was conducted to identify a clear processing mechanism. Table 3 below shows the analysis experiment methods performed.

I. Experiment specification

For accurate experiments, an acrylic reactor of the treatment method of the present invention and two acrylic reactors of an activated sludge method for comparative experiments were installed and then compared.

Reactor standard and auxiliary facilities (inflow rate: 30ℓ / day)

Phosphorus discharge tank

Specification: 200L × 84W × 250H (Acrylic type reactor)

Additional facilities: Raw water inflow pump (100ml / min, 1 Master Flex pump)

Agitator (0 ~ 200rpm, Hana product)

Denitrification tank

Specification: 200L × 168W × 250H (Acrylic type reactor)

Additional facilities: methane supply pump (50ml / min, 1 master flex pump)

Agitator (0 ~ 200rpm, Hana product)

Nitrifier

Standard: 200L × 340W × 250H (acrylic type reactor)

Facilities: Alkaline One Supply Pump (50ml / min, 1 Master Flex Pump)

Agitator (0 ~ 200rpm, Hana product)

Internal Transfer Pump (300ml / min, 1 Master Flex Pump)

Air diffuser (0-50mL / min)

Reactor standard and auxiliary facilities of activated sludge process

Active onyx

Specification: 200L × 600W × 250H (Acrylic type reactor)

Additional facilities: Raw water inflow pump (100ml / min, 1 master flex pump)

Return sludge pump (50ml / min, one Master Flex pump)

Air diffuser (0-50mL / min)

All. Water quality analysis result

The conclusion obtained through pilot operation for about 100 days in the above experiment is as follows.

1) In the sewage treatment plant according to the present invention, the inflow BOD was 86.0ml / l, the outflow BOD 10.9mg / l, the treatment rate was 83%, the inflow CODmn 28.0mg / l, the outflow CODmn 28.0mg / l, cjfldbf 70%, inflow SS 125mg / l, outflow SS 12.2mg / l, throughput 90%.

2) In nitrogen removal, which is a characteristic of the treatment method of the present invention, inflow TN 111.9mg / l, outflow TN27.4mg / l, treatment rate 76%, results below the current effluent water quality of 60mg / l. The performance was excellent with 2.6 mg / l, effluent TP 0.6 mg / l and throughput 78%.

3) In general, in the case of high nitrogen treatment, when the concentration of organic material in the influent is low, it is determined that an external organic source is required for denitrification.

4) Differences from traditional treatment

The nitrification rate of the nitrification tank is increased because it is possible to enter the nitrification tank from the denitrification tank and nitrification tank in the external conveying sludge.

Phosphorus discharge tank and phosphorus discharge tank in the inflow of sludge to ensure the residence time to denitrify, nitrification tank can prevent the reduction of nitrification rate due to the influence of water temperature during the winter season, the nitrification rear membrane is nitrification Denitrification is improved by maximizing nitrification in the tank and DO reduction of the internal conveying sludge flowing into the denitrification tank, and valve operation can be selectively performed for the reaction of each tank. Invented.

Thus, the sewage and wastewater treatment method of the present invention can be immediately applied by additionally expanding the sewage treatment plant without modification, and is easy to operate according to the change in the concentration of water quality of the treatment plant. It does not significantly change the operation method, and it can be fully operated by the operation method of the A ₂ O process, which is well known as an advanced treatment process, and the external conveying sludge flows into the nitrification tank to maintain a high concentration of MLSS, thereby improving the nitrification reaction. The sludge returned internally from the nitrification tank flows into the nitrification tank and re-absorbs the micro-oxidized treated water, which can increase the treatment efficiency decrease due to the decrease in winter water temperature.BOD 90%, TN 75%, YP 75% or more It can be removed to keep BOD 10mg / l, TN 20mg / l, TP 1mg / l or less, and denitrification by installing nitric oxide diaphragm. The DO of the sludge returned to the tank was reduced, and the denitrification rate was improved.

Claims (1)

Conventional sewage treatment is a pretreatment process that removes and equalizes solid contaminants in incoming sewage and wastewater, and biological or physical processes that simultaneously perform nitrification, denitrification, and dephosphorization in biological reactions. In the processing apparatus, Inflow of sewage and wastewater and the sludge returned from the final sludge settling tank are brought into contact with the low molecular weight of the organic anaerobic microorganisms. A phosphorus discharge tank 1 for causing absorption and phosphorus release phenomena; The denitrification microorganism causes the denitrification reaction by using the low molecular weight organic material and the internally conveyed nitrate in the phosphorus discharge tank (1). Maintaining the N (organic substance / total nitrogen) ratio depends on the degree of denitrification, and the denitrification tank (2) for stabilizing the nitrification reaction in the aeration tank since the Alkalinity (incidentally) increases. The waste and wastewater that passed through the denitrification tank converts ammonia nitrogen in the water into nitrate nitrogen by nitrifying microorganisms under aeration conditions, and at the same time, reduces phosphorus concentration in water through the phosphorus excess absorption reaction by the phosphorus removing microorganism. Nitrification tank (3) to serve to make; In the nitrification tank (3) is reduced to install a diaphragm (4) at the end to maximize the denitrification rate of the DO sludge conveyed internally to the oxygen-free tank (5), Phosphorus discharge denitrified sewage through the nitrification tank is separated into solid and liquid before being discharged from the settling tank (6) to maintain the MLSS (microbial) concentration of the bioreactor through the lower return line and the treated water is discharged; In the nitriding tank, the ammonia nitrogen is returned to the anaerobic tank, anoxic tank, and aeration tank to return the treated water oxidized to nitrate nitrogen. The anoxic tank (5) is introduced into the nitrogen tank (NO ₃ ) or the nitrite group (NO ₂ ). An internal conveying line 7 serving to change nitrogen gas by denitrification microorganisms; External conveying line for conveying to maintain the MLSS of the phosphorus discharge tank (1), denitrification tank (2), and nitrification tank, and if necessary to be returned to the nitrification tank for maximum nitrification reaction in the nitrification tank (8) A method for removing phosphorus and nitrogen in sewage treatment, comprising a process in which the phosphorus release and denitrification of sewage and wastewater can be selectively controlled and managed as necessary.