KR100531516B1 - Biological nutrient removal process - Google Patents

Abstract

The present invention relates to a method for biologically treating nutrients in sewage and wastewater, and includes a sedimentation process, a primary sedimentation process, a preliminary denitrification process, an anaerobic bioselective reaction process, an anaerobic contact process, a denitrification / dephosphorization process, and a final sedimentation process. Characterized in that made.

The method for treating sewage and wastewater according to the present invention uses sewage and wastewater as a carbon source necessary for denitrification of the returning sludge without introducing various chemicals or external carbon sources, thereby swelling the sludge and controlling the swelling of sludge by maximizing phosphorus elution and inhibiting growth of filamentous fungi. In addition to increasing the dephosphorization efficiency and increasing the sedimentation and concentration of the final sludge, the denitrification in the nitrification process, the denitrification in the final sedimentation process, and the denitrification by denitrification microorganisms (DPRB) can reduce the COD requirements of the denitrification process. The low concentration of sewage and wastewater can be treated, and the size of the denitrification tank can be reduced, thus reducing the initial facility investment cost and facility operation cost.

Description

Biological treatment of nutrients from sewage and wastewater {BIOLOGICAL NUTRIENT REMOVAL PROCESS}

The present invention relates to a method for biologically treating nutrients in sewage and wastewater, and more particularly, to a method for biologically efficiently treating nutrients such as nitrogen and phosphorus contained in sewage and wastewater.

Wastewater is increasing due to various kinds of detergents used in homes and various factory wastewater discharged as industrialization progresses, and consequently, pollution of water supplies and amusement zones is increasing.

Sewage and wastewater contain nitrogen and phosphorus such as yam, causing eutrophication / reddening and severe odor.

Thus, in order to remove nitrogen and phosphorus contained in the sewage and wastewater, various methods have been conventionally used to remove or by using an external carbon source to remove by biological methods. However, the above methods have a problem in that additional costs such as drugs or external carbon sources are added.

In particular, most sewage conduits in Korea are combined exclusion systems that exclude sewage, wastewater and rainwater as one conduit, and low concentrations of sewage and wastewater flow into sewage treatment facilities. The low concentration of sewage and wastewater introduced into the biological treatment process has low treatment efficiency due to treatment process / operational problems that do not maintain conditions (environment) suitable for the growth of microorganisms in the treatment system. There is a problem of high initial facility investment cost and treatment plant operation cost due to insufficient provision of suitable environment for growing sensitive microorganisms.

It is an object of the present invention to provide a method for biologically removing nitrogen and phosphorus, which are nutrients contained in sewage and wastewater, without the introduction of various drugs or external carbon sources.

Another object of the present invention is to provide a method applicable to low concentration sewage and wastewater treatment which is difficult to denitrify due to low chemical oxygen demand (COD).

Still another object of the present invention is to reduce the size of the denitrification tank and the nitrification tank and to reduce the initial facility investment cost and facility operation cost.

In order to achieve the above object, the method of biologically treating the nutrients of sewage and wastewater of the present invention, in the method of biologically treating the nutrients of sewage and wastewater introduced through the sedimentation process and the primary sedimentation process, A pre-denitrification step of denitrifying nitrogen nitrate (NO ₃ -N) contained in the return sludge which is precipitated and returned in the final settling process by introducing the sewage and wastewater which have passed through the first settling process; An anaerobic bioselection reaction step of introducing denitrified return sludge and sewage and wastewater in the preliminary denitrification step to inhibit filamentous fungi growth and to grow condensed microorganisms under anaerobic conditions; Anaerobic contact process to maximize the dissolution of the sewage and wastewater through the anaerobic bioselective reaction process under anaerobic conditions; The wastewater from the anaerobic contact process is denitrated by releasing nitrate nitrogen as nitrogen gas under anoxic conditions, and phosphorus ingested under aerobic conditions is dephosphorized and ammonium nitrogen is converted into nitrate nitrogen. Denitrification / dephosphorization processes that change to remove nitrogen and phosphorus simultaneously; And a final sedimentation step of finally solidifying the sewage and wastewater having undergone the denitrification / dephosphorization process to precipitate.

Hereinafter, with reference to the accompanying drawings will be described a process for biologically treating the nutrients of sewage, wastewater of the present invention.

Figure 1 shows an embodiment treatment system of the wastewater treatment method according to the present invention.

First, a sedimentation process is first performed to remove impurities (sand, etc.) from the introduced sewage and wastewater. Sewage and waste water flow into the sedimentation tank 1 to filter out impurities through normal filtration means such as a screen in the sedimentation tank 1.

The sewage and wastewater passing through the settling tank (1) is subjected to a primary settling process which is separated into primary treated water and waste sludge through a precipitation process in the primary settling tank (2). The sludge precipitated in the primary sedimentation tank 2 is separated through a conventional sludge storage tank 9, a sludge concentration tank 10 and a sludge dewatering tank 11 to be used as compost or sanitary landfill.

The sewage and wastewater having undergone the primary precipitation process is introduced into the preliminary denitrification tank 3 and subjected to a pre-denitrification process. At this time, a part of the sludge precipitated in the final sedimentation process is returned to the pre-denitrification tank (3), the incoming sewage and waste water acts as a carbon source to denitrate the nitrate nitrogen contained in the conveying sludge.

  Subsequently, the sewage and wastewater having undergone the preliminary denitrification process are introduced into the anaerobic bioselection reaction tank 4. The anaerobic bioselection reactor (4) inhibits filamentous fungi growth under anaerobic conditions, denitrates untreated nitrogen nitrate in a pre-denitrification process, and enhances phosphorus accumulating organisms (PAOs). This is called the Anaerobic Bio-selectors Process.

The wastewater, which has undergone the anaerobic bioselection reaction process, is introduced into the anaerobic contacting tank (5) to maximize leach. This is called the anaerobic process.

The wastewater, which has undergone the anaerobic contacting process in the anaerobic contacting tank 5, enters the denitrification / dephosphorization reaction tank 6A to simultaneously remove nitrogen and phosphorus. This denitrification / dephosphorization process releases nitrate nitrogen into nitrogen gas under anoxic conditions, and denitrifies it, and dephosphorization of excess phosphorus under aerobic conditions changes the ammonium nitrogen to nitrate nitrogen. By simultaneously removing phosphorus.

In the present invention, the denitrification / dephosphorization process can be performed by using a conventional method of removing nitrogen and phosphorus. For example, by intermittently supplying oxygen to the denitrification / dephosphorization reactor 6A, nitrate nitrogen is released as nitrogen gas under anoxic conditions, and phosphorus ingested under aerobic conditions is dephosphorized and ammonium nitrogen is nitrate nitrogen at the same time. To change. In more detail, the denitrification / dephosphorization process is described in detail. A rotor, a horizontal axis mechanical aeration device, is installed on the surface of the denitrification / dephosphorization reactor 6A, which is a single reaction tank, and an agitator is placed in the lower water of the denitrification / dephosphorization reactor 6A. ), And the denitrification / dephosphorization process is performed by PLC (Programmable Logic Controller) operation operation. In other words, when the rotor is operated, oxygen is supplied to the denitrification / dephosphorization reactor 6A to become an aerobic environment, and excess phosphorus is dephosphorized and ammonium nitrogen is converted to nitrate nitrogen. At this time, the stirrer installed in the lower part of the reactor does not operate. On the other hand, when the rotor is stopped, oxygen supply is interrupted and the denitrification / dephosphorization reaction tank 6A becomes an oxygen free environment, whereby denitrification is caused by the reaction of nitrate nitrate with organic carbon. At this time, the stirrer is operated to prevent floc precipitation of the mixed liquid in the reactor. The oxygen supply capacity of the rotor installed for the biological treatment of organics depends on the nature of the sewage, ie the load of organic contamination. Therefore, the total oxygen demand is determined according to the influent load, the treatment effluent allowance concentration and the temperature change, and the rotor capacity is determined accordingly. The operation of the rotor and the stirrer is performed according to a program defined by the PLC and is capable of controlling the lowest and highest dissolved oxygen concentrations in the denitrification / dephosphorization reactor.

The sewage / wastewater that has passed through the denitrification / dephosphorization process is introduced into the final sedimentation tank 8 and subjected to a final sedimentation process to solidify and separate the sludge. After the final sedimentation process, the final treated water is discharged, and some of the finally settled sludge is returned to the preliminary denitrification tank 3, and the remaining excess sludge is treated through a conventional sludge treatment process.

On the other hand, in the method for biologically treating the nutrients of sewage and wastewater of the present invention, the denitrification / dephosphorization process, the anaerobic contact process and nitrification process wastewater and wastewater is subjected to the accumulation of microorganisms under anoxic conditions. Denitrification process to remove nitrogen and phosphorus simultaneously by excess intake of phosphorus by denitrification, denitrification by deproducible dephosphorus microorganism (DPRB), denitrification by denitrification microorganism; and phosphorus eluted under anaerobic conditions under aerobic conditions Phosphorus is excessively ingested and dephosphorized and at the same time nitrification process for converting ammonia nitrogen (NH ₄ -N) to nitrate nitrogen (NO ₃ -N);

   As shown in FIG. 2, the wastewater, which has undergone the anaerobic contact process and the wastewater, which has undergone the nitrification process, enters the denitrification tank 6 and undergoes a denitrification process which simultaneously removes nitrogen and phosphorus. The denitrification tank (6) is an anoxic (anoxic) condition in the excess intake of phosphorus by the accumulation of microorganisms, denitrification by denitrification microorganisms that can be denitrified, denitrification reaction by denitrification microorganisms.

On the other hand, in the nitrification process (7), phosphorus eluted in the anaerobic bioselection reaction process and anaerobic contact process is excessively phosphorus ingested under aerobic conditions and dephosphorized, and at the same time, ammonia nitrogen is converted to nitrate nitrogen and denitrification tank ( 6) is fed back into the denitrification cycle.

After the nitrification and denitrification process, the wastewater is introduced into the final sedimentation tank 8 and subjected to a final sedimentation process to solidify and separate the sludge.

3 and 4 show another embodiment of the method for biologically treating nutrients in sewage and wastewater according to the present invention.

FIG. 3 shows an embodiment in which the sewage and wastewater that have undergone the primary settling process are divided into a predetermined amount into the preliminary denitrification tank 3 and the anaerobic bioselection reaction tank 4.

That is, in the present invention, it is preferable that 10 to 25% of the wastewater and wastewater that have undergone the primary precipitation process are introduced into the preliminary denitrification tank 3 and the remaining 75 to 90% are introduced into the anaerobic bioselection reaction tank 4. Do.

In the present invention, the amount of sewage and wastewater flowing into the pre-denitrification tank 3 is preferably 10 to 25% of the total amount of sewage and wastewater to be treated, which is the amount of sewage and wastewater used as the carbon source of the microorganisms. This is because the denitrification efficiency of the nitrate nitrogen contained in the conveying sludge in the preliminary denitrification tank 3 becomes maximum when it is in the range.

That is, if less than 10% of sewage and wastewater enter the preliminary denitrification tank (3), the denitrification efficiency of nitrate nitrogen becomes low due to lack of carbon source, and if it exceeds 25%, the size of the preliminary denitrification tank (3) becomes excessive. Uneconomical

The appropriate amount of sewage and wastewater flowing into the preliminary denitrification tank 3 is determined according to the concentration of nitrate nitrogen contained in the return sludge returned from the final sedimentation tank 8.

5 and 6, there is also shown another embodiment of the treatment system of the method for biologically treating nutrients in sewage and wastewater according to the present invention.

As shown in FIG. 5, in the method for biologically treating the nutrients of sewage and wastewater of the present invention, the sewage and wastewater having undergone the preliminary denitrification process in the preliminary denitrification tank 3 is introduced into the anaerobic contact tank 5. It can be processed directly into the anaerobic contact process without going through the anaerobic bioselective reaction process. At this time, 75 ~ 90% of the sewage and wastewater that passed through the primary settling process flows into the anaerobic contact tank (5). In this embodiment, the process is further simplified by not undergoing an anaerobic bioselective reaction process, and 75 to 90% of wastewater and wastewater are introduced into the anaerobic contact tank 5, and the dissolution of phosphorus in the anaerobic contact tank 5 is maximized.

   The method of biologically treating the nutrients in sewage and wastewater of the present invention will be described in more detail.

In the present invention, the sewage and wastewater having undergone the primary sedimentation process is introduced into the preliminary denitrification tank 3, which is precipitated in the final sedimentation process and is contained in the return sludge returned to the preliminary denitrification tank 3. Will denitrate.

 The pre-denitrification step in the pre-denitrification tank (3) is intended to maximize the extraction in the post-stage process by removing the nitric acid nitrate, which is an inhibitor of phosphorus elution, contained in the conveying sludge by the denitrification reaction.

In the present invention, the denitrification reaction of the preliminary denitrification process is a decomposition reaction of organic matter, so that sufficient carbon energy (organic matter) is required, and inflow and wastewater are used as carbon sources. At this time, the inflow of sewage and wastewater into the preliminary denitrification tank, the anaerobic bioselection reaction tank, or the anaerobic contacting tank, respectively, is more efficient for the denitrification of nitrate nitrogen. That is, it is preferable that only 10-25% of the total amount of sewage and wastewater to be treated is introduced into the preliminary denitrification tank, and the remaining 75-90% of the sewage and wastewater is introduced into an anaerobic Bao selective reaction tank or anaerobic contacting tank and treated.

In the present invention, when the microorganism decomposes organic matter, nitrate nitrogen is converted into nitrogen gas (N ₂ ) while using nitrate nitrogen (NO ₃ -N) included in the return sludge as a final electron acceptor. By providing a preliminary denitrification process, the nitrate nitrogen contained in the conveying sludge can be removed, thereby improving the removal efficiency of phosphorus contained in the sewage and wastewater.

In other words, when nitrate nitrogen is introduced through anaerobic contact process, denitrification microorganisms use short-chain volatile fattyacids (SCVFAs) that are easily decomposed prior to the accumulation of microorganisms. Elution does not occur, and the SCVFA accumulation is small, resulting in a lack of energy available on the aerobic phase, which also reduces the phosphorus intake capacity.

Subsequently, the conveying sludge denitrated in the preliminary denitrification step and the sewage and wastewater which have passed through the primary settling step flow into the anaerobic bioselective reaction tank 4.

The anaerobic bioselection reaction step in the anaerobic bioselection reaction tank 4 is a step of inhibiting the growth of filamentous organisms, and is a step of removing untreated nitrate nitrogen and prematurely accumulating microorganisms in a preliminary denitrification step.

Growth of filamentous fungi is the most common operational problem in the simultaneous removal of biological nitrogen and phosphorus. The increase in filamentous fungi leads to sludge bulking of sludge and poor sludge settling. Sludge swelling is due to overgrown filamentous fungi Microthrix Parvicella, Sphaerotilus Natans, Nocardia, Type 021 yen and 1701 (Type 021 & 1701). Is caused.

  The main cause of swelling is M. Parvicella, due to the low F / M microorganism concentration in the reactor. Low food-microbes exhibit very high growth rates at low substrate concentrations. Therefore, at low F / M ratio, filamentous fungi proliferate and inhibit floc-forming bacteria growth due to cell division, and consequently, at high substrate concentration, filamentous fungi are suppressed by maintaining high growth rate of floc forming microorganisms. do.

  Another sludge swelling phenomenon is due to anoxic mixing sequences, low BOD: N and BOD: P ratios. Various different changes cause swelling, but the parameters of the conventional single process for controlling these varying environments are not possible.

In the present invention, a plug flow type anaerobic bioreaction process is provided in the previous stage of the anaerobic contacting process, so that the effluent and the wastewater (preferably, 75 to 90% of the wastewater and wastewater) of the preliminary denitrification process are mixed. Therefore, it is possible to control the growth of non-filamentous organisms selectively due to the high food-microbial (F / M) ratio to control the sludge swelling phenomenon.

 In other words, non-flat flock-forming bacteria have a large μmax value but low affinity to the substrate (ie, a large Ks), whereas filamentous bacteria have a small μmax value but a large affinity to the substrate (ie, a small Ks). Due to the large concentration gradient of the substrate, dissolved organics are rapidly adsorbed to the floc forming microorganisms. As a result of the rapid removal of dissolved organic matter, less organic matter is required for the growth of filamentous fungi and is killed. Therefore, the growth of filamentous bacteria is advantageous at low substrate concentrations.

 In addition, the anaerobic bioselection reactor (4) is an anaerobic condition (environmental), so it grows in the anaerobic phase (anaerobic) excellent growth rate microorganisms (PAOs). BOD is also eliminated by using organic matter as an energy source for the activity of accumulating microorganisms.

 In the present invention, in order to meet the optimum conditions of the anaerobic bioselective reaction tank (4), it is necessary to set the residence time so that the concentration of nitrate nitrogen is 1 mg / l or less in the preliminary denitrification step of the preliminary denitrification process included in the return sludge. In addition, the nitrogenous nitrogen contained in the denitrified return sludge in the pre-denitrification process is removed by the denitrification reaction in the anaerobic bioselection reaction tank 4.

Conventional filamentous fungi control involves injecting chlorine or hydrogen peroxide (H ₂ O ₂ ) into the return sludge, changing the dissolved oxygen (DO) concentration in the nitrification process, injecting key nutrients, growth factor) was temporarily injected. Chlorine injection is effective for suppressing sludge swelling by filamentous fungal growth but ineffective for swelling by light flocs containing bound water. In addition, turbid effluent is produced until the filamentous fungus dies upon chlorine injection. Chlorination of nitrified sludge also results in turbid runoff resulting from the killing of nitrifying microorganisms and increases maintenance costs.

  In the anaerobic contact process, submerged agitators are installed so that the return sludge and the inflow sewage and wastewater discharged from the anaerobic bioselective reaction tank 4 are completely mixed. Phosphorus release in anaerobic contact processes is a biodegradable, soluble BOD is formed by heterotrophs, mainly fatty acid low molecular weight organic matter (SCVFA).

The formed low molecular weight organic matter is decomposed by Poly-p microorganisms. Ortho-phosphate (PO ₄ ^-2 ) using energy generated by hydrolysis by stored polyphosphate (P ₂ O ₂ ). It is eluted by decomposition and low molecular weight organic matter is stored in cells as PHB (Poly-β-hydroxy butyrate). Degradation of Poly-p to Ortho-p increases soluble phosphate in the mixture and also releases energy. Energy stores microorganisms in soluble BODs through the cell wall. In this way, the BOD concentration of the mixed solution is reduced without oxygen consumption.

  In the nitrification process, poly-p microorganisms use nitrite and oxygen for PHB oxidation to grow into new Poly-p microorganisms, absorbing the energy released when oxidizing to PHB, and ingesting soluble phosphorus above the normal level. Stored. The stored phosphorus accumulates in the sludge aggregated with the microorganisms, and is precipitated and removed in the final precipitation process.

  The nitrification process and the denitrification process are processes for removing organic matter, nitrogen and phosphorus simultaneously, and in order to improve the efficiency of removing nitrogen and phosphorus at the same time, a separate pre-denitrification process and anaerobic bio-selection process are installed in front of the anaerobic contact process. By improving the nitrogen and phosphorus removal efficiency higher.

In the aerobic (oxygen) process, oxidization of organic substances and oxidation of ammonium nitrogen (NH ₄ -N) to nitrate nitrogen (NO ₃ -N) are carried out, and dephosphorization occurs due to excess intake of phosphorus. In the anoxic region (in the absence of molecular oxygen), denitrification proceeds by the reaction of nitrified nitrates with organic carbon, releasing nitrate nitrogen as nitrogen gas. The denitrification requires organic carbon as an energy source, so the influent sewage and waste water itself is a carbon source. In the present invention, since the influent wastewater flows directly into the anaerobic region, the influent wastewater can be smoothly used for denitrification.

 Nitrification is a biological process of autotrophs. That is, the energy of microbial growth is mainly obtained from the oxidation of nitrogen oxides such as ammonium. Nitrification of ammonium nitrogen is a two-step process involving two types of microorganisms: nitrosomonas and nitrobacter. In the first stage, ammonium is converted to nitrite, and in the second stage, nitrite is converted to nitrate.

In other words,

               Nitrozomonas

^{_{NH 4 + + O 2 --------------->}} NO 2 - + H 2 O + 2H +

                  Niobacter

^{_{NO 2 - + 1 / 2O 2}} -------------> NO 3 -

Nitrozomonas and nitrobacters use the energy produced in these reactions for cell growth and maintenance.

The overall energy response is as follows, resulting in denitrification, or nitrogen release, in the anaerobic region.

^{_{NH 4 - + O 2 ------------->}} NO 3 - + 2H + + H 2 O

NO ₃ ^- + substrate _{-------------> N 2 + CO 2 +} H 2 O + OH + cells

  In the conventional sewage and wastewater treatment process, nitrifiers known as two types of nitrozomonas sp. And nitrobacter sp. Are actually referred to by conventional conveniences representing various nitrifying microbial species. Recently, biotechnological microorganisms such as fluorescent in situ hybridization (FISH) have increased the information on the species of microorganisms that cause nitrification in the actual sewage and wastewater treatment process. In the process of the present invention, these heterotrophic microorganisms are increased. The use of heterotrophic nitrification (10-15% of autotrotrophic nitrification) enables the most economical nitrification process.

Denitrification varies according to the F / M ratio of the reaction tank, the feeding mode (VFA content, VFA type), and the concentration of microorganisms used. The larger the F / M ratio, the higher the VFA, the greater the denitrification effect. For effective denitrification, the greater the food, the greater the COD / N ratio, the greater the effect. Therefore, COD / N ratio is an important design factor in the nutrient removal process that removes nitrogen and phosphorus simultaneously.

In particular, low concentration sewage in Korea is difficult to denitrify because of low COD concentration, and as a result, it is difficult to remove phosphorus. That is, the present invention, which solves the necessary portion of the organic matter required for biological nitrogen removal because the nitrogen concentration is relatively high compared to the organic material because the COD / N ratio is low, heterotrophic desorption using a carbon source in the conventional traditional anoxic state In addition to the nitrate (NO ₃ -N)-> N ₂ gas conversion process by heterotrophic denitrifier, autotrophic denitrification microorganisms and denitrifying phosphorous removal bacteria (DPRB) are used.

That is, by directly injecting the phosphorus-containing sewage and wastewater discharged excessively in the anaerobic contact process to the denitrification process, nitrogen and phosphorus are simultaneously removed by overingestion of phosphorus and denitrifying microorganisms capable of denitrification.

Therefore, it is possible to reduce the required amount of COD of the denitrification process in nutrients.

 That is, the conversion process during denitrification is performed in the following formula, and the denitrification and phosphorus accumulation are caused by the continuous repetition of the nitrification / denitrification reaction process, followed by the final precipitation process (8).

Final sedimentation (8) must solidify the liquid from the mixed liquer suspended solids (MLSS) to obtain the target treated water and satisfy the concentration function of the return sludge.

  The conventional final settling process has a problem in that a large amount of solids flows out when the load ratio is too large by designing the process by applying the surface load ratio or the solid load ratio in the sewer design standard (Ministry of Environment). The biological nutrient removal process has a high MLSS concentration and high SVI, so that the sludge interface of the final settler is high, and solids in the sedimentation basin are easily leaked.

In the present invention, a limiting solids flux technique is proposed in which the concentration of solids in the treated water is reduced, the solid-liquid separation is reliably achieved, and the sludge zone settling that can move to the bottom of the sedimentation basin for sludge concentration is considered. By application, the amount of solids entering the settling basin is greater than the limit solids flux value so that solids cannot accumulate in the settler and flow out of the settling basin.

  As such, the maximum MLSS concentration of the nitrification process is changed according to the concentration of the return sludge. For this reason, the final precipitation process must be considered together in the biological nutrient removal process to obtain stable treated water.

 In addition, in the present invention, denitrification by endogenous denitrification by the settling sludge layer (10 cm) (anoxic sludge blanket depth) in the final sedimentation process (8) is applied to reduce the initial investment cost by reducing the volume (anoxic volume) of the denitrification reaction process. It can be inexpensive.

 On the other hand, the excess sludge is transferred to the sludge concentration tank 10 from the sludge storage tank 9 which is a conventional facility, and the sludge cake dehydrated through the sludge dewatering process is used as organic fertilizer or disposed of in sanitary land.

 In particular, the sewage and wastewater treatment method of the present invention is the dephosphorization, denitrification and solid-liquid separation of sewage and wastewater according to the continuous denitrification, anaerobic bioreaction, anaerobic contact, denitrification, nitrification, and final sedimentation. Treatment results in a low initial capital investment, the most economical and stable treatment water, and surplus sludge is recycled to withdrawal sanitation / compost.

In addition, in the present invention, wastewater (10-25%) is introduced into the carbon source required for the preliminary denitrification process, and the treatment efficiency of the anaerobic bioselective reaction tank 4 is removed to improve the treatment efficiency in summer and the high concentration of nitrate nitrogen in winter (NO _3). -N) The method considering improvement of removal efficiency, denitrification of nitrification process and denitrification of final sedimentation process can reduce the size of denitrification tank, and directly introduce phosphorus-containing sewage and wastewater eluted from anaerobic contact process directly into denitrification process. Simultaneous removal of nitrogen and phosphorus using dephosphorization microorganisms, reducing the COD requirement of the denitrification process, makes it difficult to denitrify due to the low COD, a characteristic of Korea's sewage. It is a useful invention with low operating costs.

The scope of application of the method for biologically treating nutrients in sewage and wastewater of the present invention is not limited to the above, and various modifications can be made within the scope of the present invention, and such modifications belong to the following claims. something to do.

The method for biologically treating nutrients in sewage and wastewater of the present invention is capable of simultaneously removing nitrogen and phosphorus contained in sewage and wastewater without introducing various chemicals or external carbon sources, as well as effectively removing organic matter. By using the appropriate amount of sewage and wastewater as a carbon source for denitrification of the return sludge, maximization of phosphorus elution and growth inhibition of filamentous fungi control sludge swelling, increase denitrification and dephosphorization efficiency, and increase sedimentation and concentration of final sludge.

In addition, the method for biologically treating the nutrients of sewage and wastewater of the present invention is to reduce the COD requirement of the denitrification process by denitrification in the nitrification process, denitrification in the final sedimentation process and denitrification by denitrification microorganisms (DPRB). Therefore, it is possible to treat sewage and wastewater at low concentration, and to reduce the size of the denitrification tank, thus reducing the initial facility investment cost and facility operation cost.

 In addition, by the method of the present invention by removing the nitrogen and phosphorus in the sewage and wastewater at the same time, and effectively remove the organic matter, it is possible to prematurely block the eutrophication / red tide phenomena of the water source and amusement water, closed water.

delete

1 is a flow diagram of an embodiment of a wastewater treatment method according to the present invention.

FIG. 2 is a process flow diagram showing another embodiment of the denitrification / dephosphorization process of the embodiment shown in FIG. 1.

3 and 4 is another embodiment of the wastewater treatment method according to the present invention.

5 and 6 are still another embodiment of the wastewater treatment method according to the present invention.

<Explanation of symbols for main parts of the drawings>

      1: sedimentation tank 2: primary precipitation tank

      3: pre-denitrification tank 4: anaerobic bioselection reactor

      5: anaerobic contact tank 6: denitrification reactor

6A: Denitrification / Dephosphorization Tank 7: Nitrification Process 8: Final Precipitation Tank

Claims (7)

In the method of biologically treating the nutrients of sewage and wastewater introduced through the sedimentation process and the primary sedimentation process, A pre-denitrification step of denitrifying nitrogen nitrate (NO ₃ -N) contained in the return sludge which is precipitated and returned in the final settling process by introducing the sewage and wastewater which have passed through the first settling process; An anaerobic bioselection reaction step of introducing denitrified return sludge and sewage and wastewater in the preliminary denitrification step to inhibit filamentous fungi growth and to grow condensed microorganisms under anaerobic conditions; Anaerobic contact process to maximize the dissolution of the sewage and wastewater through the anaerobic bioselective reaction process under anaerobic conditions; The wastewater from the anaerobic contact process is denitrated by releasing nitrate nitrogen as nitrogen gas under anoxic conditions, and phosphorus ingested under aerobic conditions is dephosphorized and ammonium nitrogen is converted into nitrate nitrogen. Denitrification / dephosphorization processes that change to remove nitrogen and phosphorus simultaneously; And And a final sedimentation step of finally solid-separating the sewage and wastewater having undergone the denitrification / dephosphorization process to settle it. The method according to claim 1, The denitrification / dephosphorization process, Nitrogen and phosphorus in the anaerobic contact process and the nitrification process of wastewater and waste water under anoxic conditions, overingestion of phosphorus by accumulation microorganisms, denitrification by denitrable dephosphorus microorganisms (DPRB), and denitrification by denitrification microorganisms Denitrification step to remove at the same time; And Phosphorus eluted under anaerobic conditions is overingested phosphorus under aerobic conditions and dephosphorized and at the same time converting ammonia nitrogen (NH ₄ -N) to nitric acid (NO ₃ -N); A method for biologically treating nutrients in sewage and wastewater. In the method of biologically treating the nutrients of sewage and wastewater introduced through the sedimentation process and the primary sedimentation process, A pre-denitrification step of denitrifying nitrogen nitrate (NO ₃ -N) contained in the return sludge which is returned and precipitated in the final settling process by introducing 10-25% of the sewage and wastewater which have passed through the first settling process; An anaerobic bioselection reaction step of introducing 75-90% of the return sludge denitrified in the preliminary denitrification step and the sewage and wastewater which have undergone the primary sedimentation step to inhibit filamentous fungi growth under anaerobic conditions and to grow condensed microorganisms; Anaerobic contact process to maximize the dissolution of the sewage and wastewater through the anaerobic bioselective reaction process under anaerobic conditions; Nitrogen nitrate is released and denitrated by nitrogen gas under an anaerobic contact process under anaerobic conditions, and excess phosphorus dephosphorized under aerobic conditions is dephosphorized and ammonium nitrogen is converted to nitrate nitrogen. Denitrification / dephosphorization process to remove at the same time; And And a final sedimentation step of finally solid-separating the sewage and wastewater having undergone the denitrification / dephosphorization process to settle it. The method according to claim 3, The denitrification / dephosphorization process, Nitrogen and phosphorus in the anaerobic contact process and the nitrification process of wastewater and waste water under anoxic conditions, overingestion of phosphorus by accumulation microorganisms, denitrification by denitrable dephosphorus microorganisms (DPRB), and denitrification by denitrification microorganisms Denitrification step to remove at the same time; And Phosphorus eluted under anaerobic conditions is overingested phosphorus under aerobic conditions and dephosphorized and at the same time converting ammonia nitrogen (NH ₄ -N) to nitric acid (NO ₃ -N); A method for biologically treating nutrients in sewage and wastewater. In the method of biologically treating the nutrients of sewage and wastewater introduced through the sedimentation process and the primary sedimentation process, A pre-denitrification step of denitrifying nitrogen nitrate (NO ₃ -N) contained in the return sludge which is returned and precipitated in the final settling process by introducing 10-25% of the sewage and wastewater which have passed through the first settling process; Anaerobic contact process to maximize the dissolution under anaerobic conditions by introducing 75 ~ 90% of the sewage and wastewater after the preliminary denitrification process and the primary sedimentation process; Nitrogen nitrate is released and denitrated by nitrogen gas under an anaerobic contact process under anaerobic conditions, and excess phosphorus dephosphorized under aerobic conditions is dephosphorized and ammonium nitrogen is converted to nitrate nitrogen. Denitrification / dephosphorization process to remove at the same time; And And a final sedimentation step of finally solid-separating the sewage and wastewater having undergone the denitrification / dephosphorization process to settle it. The method according to claim 5, The denitrification / dephosphorization process, Nitrogen and phosphorus in the anaerobic contact process and nitrification of wastewater and waste water under anoxic conditions, overingestion of phosphorus by an accumulating microorganism, denitrification by denitrable dephosphorus microorganisms (DPRB), and denitrification by denitrification microorganisms. Denitrification step to remove at the same time; And Phosphorus eluted under anaerobic conditions is overingested phosphorus under aerobic conditions and dephosphorized and at the same time converting ammonia nitrogen (NH ₄ -N) to nitric acid (NO ₃ -N); A method for biologically treating nutrients in sewage and wastewater. The method according to any one of claims 1 to 6, Biological process for treating sewage and wastewater biologically characterized in that the residence time is adjusted so that the concentration of nitrate nitrogen flowing out through the pre-denitrification process is less than 1mg / l.