KR100503632B1 - Method and apparatus for treating metal finishing waste which contains high nitrogen and phosphorus - Google Patents

Abstract

The present invention relates to an apparatus and a method for treating a high concentration of nitrogen and phosphorus contained in a metal surface treatment industrial wastewater by combining a chemical coagulation sedimentation process and a microorganism treatment process.

The method for treating wastewater according to the present invention comprises the steps of: 1) removing phosphorus contained in wastewater from a metal surface treatment by an aggregation reaction of an aluminum salt; 2) coagulating phosphorus remaining in the treated water subjected to primary coagulation with calcium salt Removing nitrogen by converting the nitrogen in the wastewater into nitrogen gas in a nitrogen-containing reaction tank and dissipating it into the air, and dehydrating the sludge generated in each of the steps. do.

Since the metal surface treatment industrial wastewater has a high total dissolved solids (TDS) concentration, it is impossible to apply the microorganism treatment method as a nitrogen treatment method. However, according to the present invention, it is possible to remove dissolved metal ions and phosphorus The removal of TDS at the same time has enabled microbial treatment. As a result, it has become possible to effectively treat metal surface treatment industrial wastewater containing high concentrations of nitrogen and phosphorus.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for treating metal wastewater containing a high concentration of nitrogen and phosphorus,

The present invention relates to an apparatus and a method for treating nitrogen and phosphorus in a metal surface treatment industrial wastewater. More particularly, the present invention relates to a method for treating phosphorus contained in a metal surface treatment industrial wastewater by two steps of an aluminum salt and a calcium salt, The present invention relates to an apparatus and a method for efficiently removing nitrogen and phosphorus in wastewater.

The metal surface treatment industry uses a large amount of toxic substances and chemicals. Wastewater generated contains heavy metals ions, harmful substances, various salts such as nitrogen and phosphorus. In recent years, wastewater treatment methods have been limited to the removal of heavy metals and harmful substances. In recent years, environmental pollution caused by nitrogen and phosphorus has become a social problem. There is an urgent need for development of a phosphorus treatment method.

In particular, the aluminum surface treatment industry using aluminum as a raw material has a high concentration of nitrogen and phosphorus because anodizing, which includes chemical polishing and electrolytic polishing, is the main process as a pretreatment method. These polishing processes use a large amount of nitric acid compound and phosphate as the surface treatment solution, and consequently nitrogen and phosphorus of high concentration are contained in the wastewater. In addition, a considerable amount of metallic material is dissolved in the surface treatment solution in the polishing process, thereby increasing the heavy metal ions and TDS in the wastewater. Such high concentration of TDS and heavy metal ions are the main causes of difficulty in the treatment of wastewater by the microbial treatment method.

Conventional methods for the complete treatment of metal surface treatment industrial wastewater include evaporation and concentration. This is a system in which the entire amount of wastewater is decompressed and the energy cost required for the evaporation of wastewater is 25,000 to 30,000 KRW when treated with 1 m 3 of wastewater and is ineffective treatment which takes about 4 times as much as the wastewater treatment cost incurred in a normal surface treatment industry Method. However, until now, there has been no complete treatment method to replace the evaporation enrichment method.

Korean Patent Registration No. 1996-11888 discloses a method of integrating an anaerobic tank for anaerobic digestion and anoxic anaerobic tank for denitrification in a separation tank for simplifying the process, a phosphorus absorption tank for first removing the treated water through the separation reaction tank, There has been disclosed an apparatus and a method for treating biological wastewater for nitrogen and phosphorus combined with a primary settling tank for separating a liquid mixture of an absorption tank and a liquid, a nitrification tank for nitrifying the treated supernatant in the primary settling tank, and a final settling tank, The apparatus and method are applicable only to general lower wastewater treatment and are not suitable for treatment of wastewater containing high concentration of TDS and heavy metal ions as well as low pH and high concentrations of nitrogen and phosphorus such as metal surface treatment industrial wastewater. And the processing efficiency is relatively low considering the processing time and the removal rate.

Korean Patent Laid-Open Publication No. 2001-94714 discloses a process for producing a zeolite zeolite comprising 5 to 50 weight of calcium type artificial zeolite, 15 to 50 weight of soluble aluminum or iron salt compound, 0.5 to 20 weight of natural or synthetic polymer flocculant, A water treatment agent composition for removing nitrogen and phosphorus in bottom / wastewater composed of a weight, and 10 to 40 weight of a functional preparation selected from the group consisting of calcium compounds, alkaline earth metal carbonates, titanium dioxide, and powdered activated carbon; However, the treatment method using the above composition is also applicable only to general wastewater treatment and is not suitable for the treatment of metal surface treatment industrial wastewater. Since only chemical treatment is required, a large amount of chemical agent is required There is a disadvantage in that the amount of sludge generated by the additive agent is large.

The present inventors studied the efficient treatment of nitrogen and phosphorus at a high concentration of industrial surface wastewater containing heavy metal ions and TDS at a high concentration and difficulty in proper treatment. The inventors of the present invention found that the heavy metal ions contained in the wastewater, It has been found that phosphorus can be removed by coagulation and precipitation with salt. In addition, it has been found that the removal of phosphorus from the phosphorus removal water removes heavy metal ions, And then the nitrogen contained in the treated water is removed by the microbial treatment method, so that a practical treatment apparatus and method suitable for treating nitrogen and phosphorus in the metal surface treatment industrial wastewater have been developed.

For this purpose, in treating phosphorus contained in the metal surface treatment industrial wastewater, phosphorus is removed by coagulation and sedimentation using heavy metal ions and aluminum salts dissolved in the wastewater, and phosphorus remaining in the wastewater is treated with a calcium salt , And the nitrogen was removed from the treated water in which the TDS was removed at the same time as the removal of phosphorus by the microbial denitrification using an external carbon source. Finally, the phosphorus concentration was 1 mg / L, the total nitrogen concentration was 10 mg / L and discharging it, thus completing the present invention.

Accordingly, it is an object of the present invention to provide an apparatus and a method for treating a metal surface treatment industrial wastewater which has relied on evaporation and concentration without a suitable treatment method.

In order to achieve the above object, the present invention provides an apparatus for treating metal surface treatment industrial wastewater containing nitrogen, phosphorus, heavy metal ions and total dissolved solids (TDS) at high concentration,

A water collecting tank in which metal wastewater discharged from the outside is stored;

A first chemical reaction tank connected to the water collecting tank, wherein the phosphorus contained in the wastewater flowing from the water collecting tank reacts with the aluminum salt and coagulates in the form of an aluminum phosphate compound;

A first settler connected to the first chemical reactor and separating the coagulated precipitate and the supernatant from the wastewater flowing from the first chemical reactor;

A second chemical reaction tank connected to the first settling tank, wherein the remaining phosphorus contained in the supernatant introduced from the first settling tank reacts with the calcium salt and coagulates in the form of a calcium phosphate compound;

A second sedimentation tank connected to the second chemical reaction tank and separating the flocculated sediment and the supernatant from the wastewater flowing from the second chemical tank;

A pH adjusting tank connected to the second settling tank and adapted to adjust the pH of the supernatant introduced from the second settling tank;

A batch type nitrogen reaction tank connected to the pH adjustment tank, the nitrogen contained in the wastewater flowing from the pH adjustment tank is denitrified by microorganisms; And

And a sludge dewatering device connected to the first settling tank, the second settling tank, and the batch type nitrogen tank, wherein the excess sludge generated from the first settling tank, the second settling tank and the batch type nitrogen tank is dewatered. Lt; / RTI >

The present invention also provides a method for treating metal surface treatment industrial wastewater containing high concentrations of nitrogen, phosphorus, heavy metal ions and total dissolved solids (TDS) using the wastewater treatment apparatus,

(1) firstly removing phosphorus by adjusting the pH of the metal surface treatment industrial wastewater flowing into the first chemical reaction tank through the water collecting tank to aggregate phosphorus in the form of an aluminum phosphate compound with aluminum salt contained in wastewater;

(2) separating the wastewater treated in the step (1) into a flocculation precipitate and a supernatant in a first settling tank;

(3) adding calcium salt to the supernatant separated in step (2) in the second chemical reaction tank to coagulate the remaining phosphorus in the form of calcium phosphate compound to thereby remove phosphorus;

(4) separating the wastewater treated in the step (3) into a coagulated precipitate and a supernatant in a second settling tank;

(5) adjusting the pH of the supernatant separated in the step (4) in the pH adjustment tank;

(6) biologically removing nitrogen by denitrifying the wastewater whose pH is adjusted in step (5) by a microorganism in a batch type nitrogen reaction tank;

(7) aerating the wastewater treated in the step (6) in a batch type nitrogen reactor to remove nitrogen adhering to the microorganism, precipitating the microorganism sludge, and discharging the supernatant; And

(8) A method for treating metal surface treatment industrial wastewater comprising dehydrating waste sludge generated in steps (2), (4) and (7) in a sludge dehydrator.

In the treatment method according to the present invention, in the step (1), a pH of 3 to 5, preferably 4, and a pH of 8 to 10, preferably 9 And the flocculation reaction is carried out. Further, in order to achieve optimal denitrification by the microorganism, the pH is adjusted to 6 to 8, preferably to 7 in the step (5).

According to an embodiment of the present invention, when the amount of the aluminum salt contained in the wastewater is small in the step (1), the aluminum salt may be added separately.

By the treatment apparatus and the treatment method according to the present invention, heavy metal ions and TDS are removed by coprecipitation in the removal process of phosphorus by the agglomeration of steps (1) and (3), whereby denitrification by microorganisms is possible, The concentration can be treated to 1 mg / L or less and the total nitrogen concentration to 10 mg / L or less.

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

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an apparatus and a treatment process of a metal surface treatment industrial wastewater according to the present invention,

The apparatus for treating metal surface treatment industrial wastewater according to the present invention comprises a water immersion tank (10) for storing metal surface treatment industrial wastewater, and a flocculating tank (10) for flocculating phosphorus contained in the wastewater with heavy metal ions and aluminum salts in the wastewater, The first precipitating tank (30) for solid-liquid separating the coagulated sludge, and a second precipitating tank (30) for accumulating surplus phosphorus contained in the supernatant from the first sedimentation tank with a calcium salt to form calcium phosphate A pH adjustment tank 60 for adjusting the pH of the supernatant in the second settling tank prior to the microbial treatment, a second chemical reaction tank 40 for forming a compound, a second settling tank 50 for solid-liquid separating the coagulated sludge, And a step of denitrifying the wastewater whose pH is adjusted by an external carbon source using microorganisms, re-aerating it, precipitating the microorganisms, and discharging the treated supernatant in a series of steps For nitrogen and a batch reaction vessel 70 and the first precipitation tank 30, a second settling tank 50, the sludge dehydrator 80 for the reduction of nitrogen waste sludge generated from the batch reaction tank 70.

The treatment process of the metal surface treatment industrial wastewater according to the present invention comprises a first phosphorus removal step, a second phosphorus removal step, a microorganism denitration step, aeration and precipitation step, and a dehydration step as follows.

1. First Injection Process

Metal surface treatment Industrial wastewater contains a large amount of phosphate, nitrate and heavy metal ions dissolved in the surface treatment process used in the manufacturing process. Most of these heavy metal ions constitute aluminum, iron and chromium. When the aluminum is adjusted to a proper pH in the first chemical reaction tank 20, it reacts with phosphorus-type phosphorus to aggregate while forming an aluminum phosphate compound, and then it is removed in the form of sludge in the first settling tank 30. Other heavy metals, such as iron ions, are also removed by coprecipitation with aluminum ions.

Normally, the aluminum salt necessary for the coagulation of phosphorus in the first chemical reaction tank 20 uses dissolved Al ³⁺ in the wastewater. Therefore, it is not necessary to add a separate chemical, but when the concentration of the cation in the wastewater is very low, Aluminum sulfate may be added separately.

Metal surface treatment The reaction formula of aluminum ion in industrial wastewater is as follows.

Al ³⁺ + PO ₄ ^3-? AlPO ₄ (s)

Al ³⁺ + 3OH ^-? Al (OH) ₃ (s)

As shown in Reaction Scheme 1 and Reaction Scheme 2, aluminum ions can simultaneously react with OH ^- and PO ₄ ^3- in the wastewater, and thus competition between the two reactions occurs. Lt; / RTI > That is, the higher the pH, the more Al (OH) ₃ (s) is produced and the lower the pH, the more AlPO ₄ (s) is produced. In order to improve the removal effect of phosphorus by aluminum, the lower the pH is, the more advantageous it is. However, the excessive pH lowering hinders the coagulation reaction itself, so that it is difficult to apply. The wastewater treated in the first chemical reaction tank (20) is separated into a supernatant and a precipitate in the first settling tank (30).

2. Second Injection Process

Since the phosphorus not removed by the aluminum phosphate remains in the supernatant from the first settling tank 30, the calcium salt is introduced into the second chemical reaction tank 40 to remove the remaining phosphorus.

5Ca ²⁺ + 3PO ₄ ^3- + OH ^- ↔ Ca ₅ (PO ₄ ) ₃ OH (s)

The calcium salt is removed in the form of a calcium phosphate compound as shown in Reaction Scheme 3, wherein the optimum pH is 9. The calcium salt required for the reaction is injected proportional to the amount of phosphorus to be removed. Usually calcium chloride is used in combination with calcium chloride when excessive pH is likely to rise. The wastewater treated in the second chemical reaction tank (40) is separated into the sludge and the upper water in the second settling tank (50).

3. Microorganism denitrification process

Since the pH of the supernatant introduced from the second settling tank 50 is 9, the pH is adjusted to 7 in the pH adjusting tank 60 so that the microorganism can be treated. The pH-adjusted wastewater is denitrified by the optional microorganisms in the batch-type nitrogen reactor 70, and the carbon source required is methanol. The denitrification reaction is as follows.

NO ³ + 0.83 CH ₃ OH 0.5N ₂ + 1.167H ₂ O + 0.8333CO ₂ + OH ^-

The nitrate in the wastewater is converted into nitrogen gas and dissipated into the air as shown in Reaction Scheme 4, thereby completing the nitrogen treatment. The time required for denitrification is about 8 hours.

4. Aeration and precipitation process

In the wastewater that has undergone the denitrification process, a large amount of nitrogen gas adheres to the microbial sludge, thereby deteriorating the sludge settleability. The aeration process is performed to desorb the nitrogen gas attached to the microbial sludge and to remove residual organic matter. The microorganisms in the aeration wastewater are excellent in sedimentation, so they are sedimented for a certain period of time and the clear supernatant is discharged. This process is performed in the batch type nitrogen reaction tank 70, and the aeration time and the settling time are respectively about 4 hours. It is preferable that the denitrification process, the aeration and the settling process are performed in a separate reaction tank, rather than in a single batch reaction tank, and the process is continuously performed.

5. Dehydration process

The sludge generated from the first settling tank 30, the second settling tank 50, and the batch type nitrogen reacting tank 70 is reduced by the sludge dehydrator 80, and then discharged into the waste.

Through the above-described process, phosphorus is removed from the metal surface treatment industrial wastewater in a two-stage treatment process, nitrogen is removed from the microorganism denitrification process, and then, after the aeration and precipitation process, finally discharged to a clear supernatant.

Hereinafter, an example of on-site operation according to the apparatus and method for treating wastewater of the present invention will be described, and its effect will be described.

<Examples>

Table 1 shows the results of wastewater treatment at the site.

pH T-P (mg / L) T-N (mg / L) TDS (mg / L) enemy 2.0 15,000 1,500 35,000 First chemical treatment 4.0 8,000 1,500 18,000 Second chemical treatment 9.0 5 1,500 8,000 Nitrogen reaction tank 7.0 One 10 8,000

As shown in Table 1, the metal surface treatment industrial wastewater used in this example is strongly acidic wastewater of pH 2 containing high concentrations of nitrogen, phosphorus, and TDS.

When the wastewater containing high concentration nitrogen and phosphorus is stored in the water collecting tank 10 and the pH is adjusted to 4.0 using NaOH in the first chemical reaction tank 20, Al ³⁺ contained in the wastewater reacts with phosphorus to form aluminum phosphate The compounds formed and aggregated to form a precipitate. At this point of the waste water Al ^3+, PO ₄ ^3-, heavy metal ions are removed together as by co-precipitation, TDS of the effluent was significantly reduced to 18,000 ㎎ / L at 35,000 ㎎ / L, concentration of phosphorus in addition, 15,000 ㎎ / L 8,000 ㎎ / L. The wastewater from which the precipitate was formed was separated into sludge and supernatant in the first settling tank (30).

In order to remove the remaining phosphorus present in a large amount in the supernatant separated in the first settling tank 30, Ca (OH) ₂ is added in an amount equivalent to that required for removing the remaining phosphorus in the second chemical reaction tank 40, &Lt; / RTI &gt; The pH was adjusted to 9.0 using caustic soda. The wastewater from which the precipitate was formed was separated into sludge and supernatant in the second settling tank 50 at which time the TDS concentration of the supernatant was further reduced to 8,000 mg / L and the concentration of phosphorus was almost removed to 5 mg / L.

The pH of the supernatant from the second settling tank 50 was adjusted to 7.0 by introducing H ₂ SO ₄ in a pH adjusting tank 60 for nitrogen treatment by microorganisms.

The wastewater from the pH adjustment tank 60 was introduced into a batch type nitrogen reaction tank 70, methanol was added thereto, and the mixture was denatured in an oxygen-free state for 8 hours while stirring with an underwater stirrer. During this process, the nitrogen in the waste water was called nitrogen gas.

The denitrified microbial suspension was aerated for 4 hours to dissipate the nitrogen gas attached to the microbial sludge to the air.

After the aeration, the microbial suspension was settled for 4 hours, and the microorganisms and the clear supernatant were separated and finally the purified supernatant was discharged. The nitrogen concentration in the effluent was 10 mg / L and the phosphorus concentration was 1 mg / L.

The sludge generated in the first settling tank 30, the second settling tank 50, and the batch type microorganism tank 70 was dehydrated by the sludge dehydrator 80 and then taken out as waste.

As described above, the present invention is that Al by providing an existing device and method, for treating a metal surface treatment industrial waste water containing a high concentration of nitrogen difficult and the processing apparatus and method, is contained in the waste water ³⁺ , The phosphorus is first treated and removed, and calcium phosphate such as Ca (OH) ₂ is used to completely remove untreated phosphorus. In this process, TDS-free wastewater can be treated with nitrogen by microorganisms High-concentration nitrogen can be effectively removed by treatment with a microorganism denitrification method.

In the treatment of wastewater containing a high concentration of nitrogen and phosphorus generated in the metal surface treatment industry, it is possible to economically treat the metal surface treatment industrial wastewater treated by the evaporation concentration method without the conventional treatment method Therefore, it is expected that it will have a great effect on the development of the metal surface treatment industry.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic processing apparatus and treatment process diagram of a metal surface treatment industrial wastewater according to the present invention. FIG.

10: water collecting tank 20: first chemical reaction tank

30: first settling tank 40: second chemical tank

50: second settling tank 60: pH adjusting tank

70: Batch type nitrogen tank 80: Sludge dehydrator

Claims (6)

1. An apparatus for treating metal surface treatment industrial wastewater containing a high concentration of nitrogen, phosphorus, heavy metal ions and total dissolved solids (TDS) A water collecting tank in which metal wastewater discharged from the outside is stored; A first chemical reaction tank connected to the water collecting tank, wherein the phosphorus contained in the wastewater flowing from the water collecting tank reacts with the aluminum salt and coagulates in the form of an aluminum phosphate compound; A first settler connected to the first chemical reactor and separating the coagulated precipitate and the supernatant from the wastewater flowing from the first chemical reactor; A second chemical reaction tank connected to the first settling tank, wherein the remaining phosphorus contained in the supernatant introduced from the first settling tank reacts with the calcium salt and coagulates in the form of a calcium phosphate compound; A second sedimentation tank connected to the second chemical reaction tank and separating the flocculated sediment and the supernatant from the wastewater flowing from the second chemical tank; A pH adjusting tank connected to the second settling tank and adapted to adjust the pH of the supernatant introduced from the second settling tank; A batch type nitrogen reaction tank connected to the pH adjustment tank, the nitrogen contained in the wastewater flowing from the pH adjustment tank is denitrified by microorganisms; And And a sludge dewatering device connected to the first settling tank, the second settling tank, and the batch type nitrogen tank, wherein the excess sludge generated from the first settling tank, the second settling tank and the batch type nitrogen tank is dewatered. . A method for treating metal surface treatment industrial wastewater containing high concentrations of nitrogen, phosphorus, heavy metal ions and total dissolved solids (TDS) using the wastewater treatment apparatus of claim 1, (1) firstly removing phosphorus by adjusting the pH of the metal surface treatment industrial wastewater flowing into the first chemical reaction tank through the water collecting tank to aggregate phosphorus in the form of an aluminum phosphate compound with aluminum salt contained in wastewater; (2) separating the wastewater treated in the step (1) into a flocculation precipitate and a supernatant in a first settling tank; (3) adding calcium salt to the supernatant separated in step (2) in the second chemical reaction tank to coagulate the remaining phosphorus in the form of calcium phosphate compound to thereby remove phosphorus; (4) separating the wastewater treated in the step (3) into a coagulated precipitate and a supernatant in a second settling tank; (5) adjusting the pH of the supernatant separated in the step (4) in the pH adjustment tank; (6) biologically removing nitrogen by denitrifying the wastewater whose pH is adjusted in step (5) by a microorganism in a batch type nitrogen reaction tank; (7) aerating the wastewater treated in the step (6) in a batch type nitrogen reactor to remove nitrogen adhering to the microorganism, precipitating the microorganism sludge, and discharging the supernatant; And (8) A method for treating metal surface treatment industrial wastewater comprising dehydrating waste sludge generated in steps (2), (4) and (7) in a sludge dewatering machine. The method according to claim 2, wherein the coagulation reaction is carried out after adjusting the pH to 3 to 5 in step (1) and the pH to 8 to 10 in step (3), and adjusting the pH to 6 to 8 in step (5) A method of treating metal surface treatment industrial wastewater. The method according to claim 2, wherein, in step (1), when the amount of the aluminum salt contained in the wastewater is small, an aluminum salt is added separately. 3. The method according to claim 2, wherein the metal ions and the total dissolved solids (TDS) are removed by coprecipitation in the removal of phosphorus by the aggregation of steps (1) and (3) Methods of treating industrial wastewater. delete