KR100406734B1 - Method for preparing predisposal of livestock waste water completed struvite and ammonia stripping and device thereof - Google Patents

Abstract

The present invention relates to a method and apparatus for pretreatment of livestock wastewater with struvite precipitation and ammonia stripping combined nitrogen and phosphorus simultaneous removal, which is performed by simultaneously performing struvite precipitation and ammonia stripping, which are physical and chemical treatment methods. A method and apparatus for struvite precipitation and ammonia stripping-coupled nitrogen and phosphorus simultaneous livestock wastewater pretreatment that can simultaneously remove wine and maintain a C / N ratio suitable for subsequent biological treatment.

To this end, the present invention provides a nitrogen and phosphorus simultaneous livestock wastewater pretreatment method and apparatus which combines organic nitrogen and ammonia stripping which is effective in removing struvite precipitation and high concentration of ammonia, which are effective for removing phosphorus.

The present invention can handle a load 2 to 3 times higher than the conventional livestock wastewater treatment process, and can remove high concentrations of organic matter, nitrogen and phosphorus even in a short residence time, as well as a subsequent anaerobic tank for phosphorus removal. By omitting, the site of the subsequent treatment process can be reduced, and the cost is reduced by preventing the blockage of the pipe by removing the material causing the blockage of the pipe in advance by struvite precipitation.

Description

METHOD FOR PREPARING PREDISPOSAL OF LIVESTOCK WASTE WATER COMPLETED STRUVITE AND AMMONIA STRIPPING AND DEVICE THEREOF}

[Industrial use]

The present invention relates to a method and apparatus for pretreatment of livestock wastewater for simultaneous removal of struvite precipitation and ammonia stripping combined nitrogen and phosphorus, and simultaneous physical and chemical treatment of struvite precipitation and ammonia stripping. Simultaneous removal of struvite precipitation and ammonia stripping combined nitrogen and phosphorus livestock wastewater to remove nitrogen and phosphorus in high concentrations simultaneously and maintain a C / N (COD / TKN) ratio suitable for subsequent biological treatment A method and apparatus are disclosed.

[Prior art]

General livestock wastewater treatment methods include physical, chemical, and biological treatment methods, but most of them are biological treatment methods in which physical or chemical methods are combined as pre and post treatment methods.

The biggest problem of domestic livestock wastewater treatment facility was designed by manure for livestock (pig) flowing into the treatment facility according to BOD 5,000 mg / L, SS 2,000 mg / L, but the actual inflow of pig manure is BOD 25,000 ~ It is more than 30,000 mg / L, and contains a high concentration of nitrogen of about 4,000 to 7,000 mg / L and a high concentration of phosphorus of about 1,000 to 3,000 mg / L significantly exceeds the treatment capacity. As environmental standards become more stringent, the treatment of livestock wastewater requires not only the removal of organic matter but also the strict treatment of nitrogen and phosphorus. Biotreatment alone is not possible and does not meet effluent quality standards.

Above all, the C / N (COD / TKN) ratio, which is suitable for removing nitrogen and phosphorus biologically, is 8-11 or more. For slurry type livestock wastewater, the C / N ratio is generally 6 or less, and it is difficult to treat wastewater separated from manure and urine. Is more difficult to process due to its lower C / N ratio (Kyun, PS et al., 2000). The biological treatment process for the high-level treatment of nitrogen and phosphorus in livestock wastewater consists mainly of anaerobic, anaerobic, and aerobic tank processes, but livestock wastewater has a low C / N ratio, making it difficult to secure sufficient organic matter for denitrification under anoxic conditions. As it is difficult and substrate competition occurs between phosphorus-removing microorganisms and denitrification bacteria, it is very difficult to remove nitrogen and phosphorus in high concentrations in livestock wastewater biologically unless there is sufficient substrate (Hartwig, 1992; Chae et al., 2000). Therefore, the process becomes more complicated to remove sufficient nitrogen, phosphorus and organics, and the operation cost is increased by adding extra organics for denitrification.

In order to solve these problems, nitrogen and phosphorus are mostly removed in the pretreatment process to meet the balance of nitrogen, phosphorus and organic matter in the main treatment process, which enables effective biological denitrification and dephosphorization, and at the same time, it is possible to simplify the process. Development is urgently needed. As part of the pretreatment process to remove high concentrations of nitrogen, ammonia stripping is applied in some livestock wastewater treatment plants, but there are many problems. In foreign countries, struvite precipitation for fertilizer plant wastewater containing high concentrations of nitrogen and phosphorus Although it is used individually, it is mainly focused on the recovery of nitrogen and phosphorus, which is difficult to operate due to excessive chemical costs.

Ammonia stripping process shows stable removal rate by changing most of ammonia to gaseous state at high pH such as pH 10.5 ~ 11.5, but it is sensitive to temperature and requires a large amount of blowing air, and it has significant problems such as winter fog and ice. It has a problem that the drug cost required for pH adjustment is expensive. In a conventional treatment plant, lime is injected for ammonia stripping to raise the pH, and the lime and high pH supplied cause the absorption of carbon dioxide in the air, forming a large amount of calcium carbonate scale in the stripping tower and the inlet pipe. Increase operating costs In addition, by injecting lime during ammonia stripping, it is possible to remove some of the phosphorus present in the livestock wastewater, but excessive sludge generation causes an increase in treatment cost. In addition, ammonia stripping is impossible to remove organic nitrogen. Since about 30-50% of the TKN of livestock wastewater is organic nitrogen, it is virtually difficult to remove more than 50% of the total nitrogen of livestock wastewater by ammonia stripping.

Struvite precipitation is partly used to recover nitrogen and phosphorus from industrial wastewater, such as wastewater from fertilizer plants containing high concentrations of ammonia and phosphorous acid, and struvite crystals are commonly found in livestock wastewater treatment. This causes a serious problem of duct obstruction. Struvite is magnesium ammonia phosphate hexahydrate (MgNH ₄ PO ₄ · 6H ₂ O), which is likely to be produced above pH 8 and has the lowest solubility between pH 10.5 and 11 (Ohlinger et al, 1998; Kabdashli et al., 2000; Maqueda et al., 1993; Webb and Ho, 1992; Loewenthal et al., 1994).

In other words, the struvite determination is generated when Mg ²⁺ , NH ₄ ⁺ , and PO ₄ ^3- in the livestock wastewater exceed the stratibyte solubility limit, and the solubility constant (pK _sp ) varies depending on the researcher. The same scheme 1 shows about 13.0.

Scheme 1

The struvite precipitation removes nitrogen and phosphorus simultaneously and removes much of the organic nitrogen, which was not possible in ammonia stripping because of the substantial solids removed during the precipitation process. The removal has the advantage of reducing the load on subsequent biological phosphorus removal processes. However, for struvite precipitation, high concentrations of ammonia, phosphate, and magnesium ions must be injected, which is very expensive. Furthermore, in order to treat wastewater with high concentrations of ammonia and phosphate as well as livestock wastewater, it is necessary to supply excessive magnesium (Mg) and phosphate to maintain the optimum molar ratio required for struvite precipitation. have.

The ammonia stripping and struvite precipitation process may be a pretreatment process for nitrogen and phosphorus removal of livestock wastewater, but since it is difficult to apply individually, it is necessary to improve efficiency by mutual complement. Moreover, struvite precipitation is effective at low temperatures and ammonia stripping is a suitable process for high temperatures, so it is difficult to apply each process separately in Korea where the four seasons are obvious.

In consideration of the problems of the prior art, the present invention performs struvite precipitation and ammonia stripping at the same time to simultaneously remove high concentrations of nitrogen and phosphorus and to maintain a C / N ratio suitable for subsequent biological treatment. An object of the present invention is to provide a method for pretreatment of livestock wastewater with simultaneous precipitation and ammonia stripping of nitrogen and phosphorus.

It is another object of the present invention to provide a nitrogen, phosphorus simultaneous livestock wastewater pretreatment apparatus combined with struvite precipitation and ammonia stripping.

Still another object of the present invention is to provide a method for treating biological nitrogen and phosphorus simultaneously removing livestock wastewater using livestock wastewater.

Still another object of the present invention is to provide a biological nitrogen and phosphorus simultaneous livestock wastewater treatment apparatus of livestock wastewater.

1 shows a pretreatment apparatus combining a struvite precipitation and ammonia stripping according to an embodiment of the present invention.

2 is a graph showing changes in nitrogen, phosphorus removal and C / N ratio in livestock wastewater in each process according to an embodiment of the present invention.

Description of the main symbols in the drawings

1: pH adjusting chemical tank (NaOH, H ₂ SO ₄ ) 2: Mg chemical tank

3: PO ₄ ^3- -P chemical bath 4: diffuser

5: stirrer 6: sediment drain valve

7: inlet 8: outlet

9: Jet Nozzle 10: Struvite Settling Tank

11: high speed formation part 12: blower

13: pump 14: nozzle

[Means for solving the problem]

In order to achieve the above object, the present invention, in the pre-treatment method of livestock wastewater that can remove nitrogen and phosphorus at the same time, a) chemicals to add pH adjustment chemicals, Mg ²⁺ , PO ₄ ^3- -P to the raw water; B) precipitating the wastewater of step a) by mechanical stirring and intermittent air agitation by jet nozzles; and c) discharging the struvite crystals generated in step b). step; And d) stripping the ammonia in the wastewater by forming a wastewater in the wastewater of step c) at high speed.

It provides a pretreatment method of livestock wastewater comprising a.

In another aspect, the present invention in the pre-treatment device of wastewater including a sedimentation tank having an inlet and an outlet for inflow or outflow of wastewater into the sedimentation tank for the pretreatment of livestock wastewater that can remove nitrogen and phosphorus at the same time, the communication with the sedimentation tank, Chemical injection unit for injecting the chemical into the wastewater introduced into the sedimentation tank; A high speed oil formation part installed inside the sedimentation tank for dewatering wastewater and ammonia; A struvite settling tank installed under the settling tank, in which struvite crystals are precipitated; And a drain valve connected to a lower portion of the struvite sedimentation tank for discharging the struvite crystals in the struvite sedimentation tank.

Hereinafter, the present invention will be described in detail.

[Configuration and Action]

The present invention, unlike the prior art of injecting the drug in a molar ratio of Mg ²⁺ : NH ₄ ⁺ : PO ₄ ³ = 1: 1: 1, which is an optimal molar ratio of struvite precipitation, provides a molar ratio of soluble phosphorous present in the wastewater. ^Struvite precipitation is performed by injecting as much Mg ²⁺ or by injecting Mg ²⁺ and PO ₄ ^3- so that the concentration of nitrogen remains ^intact for subsequent biological treatment. In addition to maintaining a C / N ratio suitable for subsequent biological treatment through ammonia stripping for additional nitrogen removal, ammonia stripping can be simultaneously removed during high temperature summers and nitrogen and phosphorus by struvite crystals in winter. By carrying out the ammonia stripping and struvite determination at the same time with the pretreatment method, it can handle the load 2-3 times higher than the conventional livestock wastewater treatment process, Edo not only removes high concentrations of organics, nitrogen, and phosphorus, but also eliminates significant amounts of phosphorus in the pretreatment process, which simplifies the process by eliminating subsequent anaerobic tanks for phosphorus removal. It is possible to provide a pretreatment method for livestock wastewater that can achieve stable treatment efficiency regardless of season.

More specifically,

a) a chemical input step of adding a pH adjusting agent, Mg ²⁺ , and PO ₄ ^3- -P to the wastewater raw water to produce a pH of 8.0 or higher and struvite crystals;

b) a swirl flow mechanical stirring step for agitation suitable for struvite precipitation in the wastewater of step a);

c) generating the agitation result of step b), and discharging the precipitated struvite crystals; And

d) a high-speed oil droplet formation step for maximizing the degassing of ammonia in the wastewater raw water of step c)

Livestock wastewater pretreatment method comprising a.

In the present invention, the struvite precipitation is capable of simultaneous removal of nitrogen and phosphorus by chemical crystallization reaction, and is more effective in removing organic nitrogen which was impossible for ammonia degassing because solids precipitated together more rapidly in winter when the temperature is low. In addition, the phosphorus can be sufficiently removed in the pretreatment process, so that the anaerobic tank for phosphorus removal can be omitted in the subsequent treatment process, thereby simplifying and compacting the process.

In the livestock wastewater pretreatment method of the present invention, before the step a), it is preferable to further include degassing the high concentration of carbon dioxide produced by biodegradation as a result of the biodegradation while the wastewater stays in the storage tank through an acid pipe. By increasing the pH to suit the struvite precipitation, the cost of chemicals required for pH adjustment can be reduced.

In the pH adjusting chemical bath of step a), it is preferable to use NaOH or H ₂ SO ₄ as the pH adjusting chemical, and for the pH suitable for struvite precipitation, it is preferable to administer the waste water to have a pH of 8.0 or higher. .

In addition, the ag Mg chemical tank and PO ₄ ^3- chemical tank of step a) can be removed by nitrogen, phosphorus by struvite crystals by adding Mg ^{2 +} and PO ₄ ^3- -P. In the Mg ²⁺ is preferably to inject as much as the mole ratio of phosphorus solubility present in the livestock waste water, an excess of the remaining NH ₄ ⁺ is preferably degassed to remove.

In step a), during the process of adding the pH adjusting chemicals and Mg ²⁺ , and PO ₄ ^3- , it is preferable to add the coagulation material of the struvite precipitation. The coagulated tuberculosis material is fine powder type natural zeolite, and it is preferable to add 10 to 2000 mg / L per raw material of wastewater.

The step b) is a step for smoothly mixing the waste water, air and chemicals in the settling tank, to prevent the laminar flow generated during swirl flow mechanical agitation and to maximize the vortex after the step c) after the jet of the reaction vessel It is preferable to further include the step of introducing air intermittently through the nozzle.

In step c), the struvite precipitation tank is formed to be inclined in two stages to effectively collect the sediment, and a pressure reduction facility may be installed on the struvite precipitation tank to increase the ammonia degassing efficiency when the temperature decreases.

In the step d) to form a fine oil droplets (fine water droplets) to maximize the ammonia degassing by the waste water remains and the mass transfer of the atmosphere.

In addition, the step d) is preferably carried out at the same time, further comprising the step of spraying the wastewater to the high-speed oil drop forming unit through the upper nozzle, which can remove the excess bubbles generated during ammonia degassing, Can improve the material transfer efficiency.

In another aspect, the present invention provides a pre-treatment device for wastewater, characterized in that the strikite precipitation and ammonia stripping is performed simultaneously in one reactor to realize a method for pretreatment of livestock wastewater that can remove nitrogen and phosphorus at the same time Bar, in the wastewater pretreatment apparatus including a sedimentation tank having an inlet (7) and an outlet (8) for inflow or outflow of the wastewater into the sedimentation tank, the drug injection in communication with the sedimentation tank, the chemical injection into the wastewater introduced into the sedimentation tank Part (1, 2, or 3); A high speed oil drop formation unit 11 installed inside the sedimentation tank for dewatering wastewater and ammonia; A struvite settling tank installed under the settling tank, in which struvite crystals are precipitated; And a drain valve 6 connected to the lower part of the struvite settling tank for discharging the struvite crystals in the strutbite settling tank.

The settling tank is in communication with the chemical injecting unit for injecting the chemical into the wastewater introduced into the settling tank, the chemical inlet is pH adjustment chemical tank (1), Mg chemical tank (2), and PO ₄ ^3- chemical tank (3) is settling tank Is made in communication with

Here, the pH adjusting chemical tank 1 is a chemical tank for insufficient pH adjustment as the pH adjustment is made in the acid pipe 4 to be described later, and it is preferable to use a chemical such as NaOH or H ₂ SO ₄ .

The Mg chemical tank (2) and PO ₄ ^3- chemical tank (3) are installed to inject Mg ²⁺ and PO ₄ ^3-- P into the settling tank to remove nitrogen and phosphorus by struvite crystals.

In addition, an air inlet for injecting air for the detonator is communicated to the settling tank, and an air inlet is connected to the settling tank and is connected to the blower 12 for injecting air to the wastewater in the settling tank, and connected to the blower 12 and installed inside the settling tank. And an air diffuser 4 for introducing air introduced into the blower 12 into the settling tank, and a jet nozzle 9 connected to the blower 12 and installed on the side of the settling tank.

The stirrer (5) is located at the top of the settling tank to allow the waste water, air and chemicals to be stirred smoothly inside the settling tank.

In addition, a high speed oil drop forming portion 11 is installed at an inner upper portion of the sedimentation tank, which is a structure in which a plurality of blades are installed on a rod formed as a propeller as viewed from above, and rotates by a motor to form fine water droplets (fine water droplets) and wastewater. Maximize ammonia degassing by mass transfer of remains and atmosphere.

In addition, by controlling the wastewater in the reaction tank by a predetermined amount through the pump 13 by spraying the wastewater through the upper nozzle 14 to maximize the material transfer and suppress the foaming.

The lower part of the settling tank is provided with a struvite settling tank 10 in which the struvite crystals are settled.

The lower part of the struvite sedimentation tank is inclined in two stages for the collection of effective sediment during sedimentation, the inclination angle is preferably at least 50 °. If the inclination angle is less than 50 °, there is a problem that the precipitation is accumulated inside the settling tank.

Moreover, the drain valve 6 which discharges the struvite crystal | crystallization in the struvite precipitation tank 10 is provided in the lower part of the struvite precipitation tank 10.

On the other hand, in order to increase the ammonia degassing efficiency when the temperature decreases, a pressure reduction facility may be installed on the upper part of the struvite settling tank.

Operation for pretreatment of wastewater as described above is automatically controlled by a programmable logic controller (PLC), and is performed simultaneously or sequentially according to time and operation logic.

The pretreatment apparatus for livestock wastewater configured as described above, Mg ^{2 +} and PO ₄ in the Mg chemical tank (2) and PO ₄ ^3- chemical tank (3) to the wastewater flowing into the sedimentation tank through the inlet (7) first there is injected into a ^3, the multiple host bytes settling tank 10, injection of soluble phosphorus molar ratio of as much as Mg ²⁺ present in the livestock waste water and then NH ₄ ⁺ is only residual nitrogen concentration of about multitude not go to the subsequent biological treatment.

In the present invention, since the ammonia stripping efficiency is excellent in the summer when the temperature is high, the ammonia stripping is mainly performed to remove the nitrogen in the summer, and in the winter, the ammonia stripping efficiency is low due to the temperature decrease. As nitrogen and phosphorus are simultaneously removed by crystallization, struvite crystallization is relatively stable at pH 8.0 or above, and thus sufficient pH adjustment is possible using an air inlet.

However, if sufficient pH adjustment is not easy even with the air inlet as described above, pH adjustment is performed by adding NaOH in the pH adjustment chemical bath.

When the detonator and chemicals as described above are introduced, the waste water, air, and chemicals are smoothly stirred using the stirrer 5.

In struvite precipitation, micropowder-type natural zeolite is added as coagulation nucleus material to promote coagulation reaction and induce adsorption of nitrogen and phosphorus, and also to mix MgCl ₂ and brine as Mg source to reduce chemical cost.

The present invention provides a method for treating livestock wastewater, including the livestock wastewater pretreatment method as described above.

In another aspect, the present invention provides a livestock wastewater treatment apparatus including the livestock wastewater pretreatment device.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, an Example is for illustrating this invention and is not limited only to these.

EXAMPLE

Example 1

In order to remove nitrogen and phosphorus from the livestock wastewater, struvite precipitation was performed at pH 8, and then the precipitate was removed and the pH was raised to 10 again to perform ammonia stripping for about 2.5 hours.

Comparative Example 1

Only struvite precipitation was performed at pH 8 to remove nitrogen and phosphorus from the livestock wastewater.

Comparative Example 2

Only ammonia stripping was carried out at pH 10 for about 2.5 hours to remove nitrogen and phosphorus from the livestock wastewater.

As a result of Example 1 and Comparative Examples 1 and 2, as shown in FIG. 2, in the case of Example 1 which simultaneously performed struvite precipitation and ammonia stripping, 53% of ammonia and 80% of phosphoric acid were confirmed to be removed. . However, in the case of Comparative Example 1, which performed only struvite precipitation, ammonia nitrogen decreased about 13% from the initial 4600 mg / L to 4000 mg / L, while the fixed phosphoric acid was about 230 mg / L from the initial 1000 mg / L. The removal efficiency was about 77%. In addition, in the case of Comparative Example 2, which performed only ammonia stripping, it was confirmed that ammonia was reduced by about 41%, while phosphoric acid was hardly removed.

The present invention can handle a load 2 to 3 times higher than the conventional livestock wastewater treatment process, and can remove high concentrations of organic matter, nitrogen and phosphorus even in a short residence time, as well as a subsequent anaerobic tank for phosphorus removal. By omitting, the site of the subsequent treatment process can be reduced, and the cost can be reduced by preventing the blockage of the pipe by removing the material causing the pipe blockage in advance with the struvite.

Claims (12)

(correction) In the livestock wastewater pretreatment method, a) a chemical input step of adding a pH adjuster, Mg ²⁺ , PO ₄ ^3- -P to the wastewater raw water; b) intermittent air agitation of the wastewater of step a) by mechanical stirring and jet nozzle Simultaneously performing the struvite precipitation; c) discharging the struvite crystal produced in step b); And d) the waste water of step c) is formed at high speed to remove ammonia in the waste water. Stripping step Livestock wastewater pretreatment method comprising a. The method of claim 1, A method of pretreatment of livestock wastewater further comprising the step of an aerator for degassing the carbon dioxide generated during the residence of the wastewater in the reservoir prior to step a). The method of claim 1, And a step of introducing air through the jet nozzle on the side of the reactor after step b). The method of claim 1, And d) spraying the wastewater to the high speed oil drop forming apparatus through the upper nozzle in step d). The method of claim 1, The step b) is a step of adding a coagulated tuberculosis material after the addition of the pH adjusting agent, and then Mg ²⁺ , and PO ₄ ^3- The pre-treatment method of livestock wastewater. The method of claim 5, A method for pretreatment of livestock wastewater, in which the coagulated tuberculosis substance is added at a concentration of 10 to 2000 mg / L per liter of wastewater with fine powder-type natural zeolite. In the livestock wastewater pretreatment apparatus comprising a sedimentation tank having an inlet and an outlet for inflow or outflow of the wastewater into the sedimentation tank for pretreatment of the livestock wastewater, A chemical injection unit communicating with the precipitation tank and injecting the chemical into the wastewater introduced into the precipitation tank; An agitator for agitation suitable for struvite precipitation of the wastewater; A high speed oil drop formation unit installed inside the sedimentation tank for dewatering the waste water and ammonia; A struvite settling tank installed under the settling tank, in which struvite crystals are precipitated; And A drain valve connected to the bottom of the struvite sedimentation tank for discharging struvite crystals in the struvite settling tank Livestock wastewater pretreatment device comprising a. (delete) The method of claim 7, wherein The pretreatment device of the livestock wastewater is connected to the settling tank and blower for injecting air into the wastewater in the settling tank, an acid pipe connected to the blower and installed in the settling tank to inject air introduced into the settling tank into the settling tank, and the blower A livestock wastewater pretreatment apparatus further comprising an air inlet comprising a jet nozzle connected to the settling tank. The method of claim 7, wherein The livestock wastewater pretreatment apparatus further comprises a nozzle for spraying the wastewater in order to maximize the material transfer in the high speed oil formation and to remove excess bubbles generated during degassing. (delete) (delete)