KR101463987B1 - Method of treating organic waste water - Google Patents

Abstract

The present invention relates to a method for aerobically biologically treating organic wastewater and then carrying out coagulation treatment by adding an inorganic coagulant to remove a soluble substance or a suspended material containing biologic metabolites in the biological wastewater, And to obtain a good flocculation treatment water after the addition amount is reduced.

An organic wastewater treatment method for introducing an organic wastewater into a biological treatment tank (1) for aerobic biological treatment, adding an inorganic coagulant to biological treatment water flowing out from an outlet of the biological treatment tank (1) The pH of the biological treatment water in the outlet region in the biological treatment tank (1) is set to 7.3 or less.

Description

[0001] METHOD OF TREATING ORGANIC WASTE WATER [0002]

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a systematic diagram showing a specific example of a treatment apparatus suitable for carrying out the method of treating organic wastewater of the present invention. Fig.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of treating organic wastewater.

3 is a systematic diagram showing a specific example of a treatment apparatus suitable for carrying out the method of treating organic wastewater of the present invention.

4 is a graph showing the relationship between the set pH of the aeration tank and the FI value of the flocculation treated water in the case of the addition amount of the inorganic flocculant of 300 mg / L and the case of 400 mg / L obtained from the results of Examples 1 to 3 and Comparative Examples 1 and 2 FIG.

Description of the Related Art

1: aerobic biological treatment reactor (aeration tank)

2: First coagulation tank

3: Second coagulation tank

4: Solid-liquid separation tank (pressurized floating tank)

5: Filter

6: RO membrane separator

11: aerobic bioreactor

12: Settling tank

21, 22: biological filtration tank

The present invention relates to a method of treating organic wastewater, and more particularly, to an organic wastewater which is aerobically biologically treated and then an inorganic coagulant is added to remove a soluble substance or a suspended substance containing a biological metabolite in biological treatment water And a method of performing coagulation treatment.

As a method of treating organic wastewater, biological treatment methods are widely adopted. Further, in order to remove contaminants such as suspended substances and soluble substances in the biological treatment water or in the case where the amount of drainage is large, coagulation treatment of the biological treatment water for the water recovery, and further treatment of the film after the flocculation treatment are carried out.

Since the coagulant (inorganic coagulant) added for accelerating the coagulation action when coagulating the biological treatment water is a factor that is directly connected to the running cost, it is required to reduce the amount of the coagulant. However, ), In particular, the amount of the coagulant added is large because it contains a large amount of biologic metabolites.

Particularly in recent years, recycling of water resources is becoming important, and drainage is being recovered. However, a large amount of coagulant is required to highly purify water discharged as drainage to a level that can be reused after biological treatment. For this reason, reduction of the amount of the flocculant added in the coagulation treatment of biological treatment water has become a big problem.

Although it is known to use a polymer flocculant in combination to reduce the amount of the inorganic flocculant added, there is a cost for adding the polymer flocculant.

An object of the present invention is to solve the above-described problems of the prior art, and to provide a method of aerobically biologically treating organic wastewater, and then adding an inorganic coagulant to remove a soluble or suspended material containing biologic metabolites in biological treatment water, Which is capable of reducing the addition amount of an inorganic flocculant and obtaining a good flocculation treatment water in a method of treating organic wastewater.

The inventors of the present invention have paid attention to the fact that the necessary addition amount of the inorganic coagulant is generally increased at the wastewater having a high pH at the end of the aerobic biological treatment tank. On the other hand, the present inventors have found that when the pH of the end of the aerobic biological treatment tank is not more than 7.3, particularly 6.5 to 6.9, sufficient flocculation effect can be obtained even when the amount of the inorganic flocculant added is small.

A method of treating organic wastewater according to the present invention is a method of treating organic wastewater by introducing organic wastewater into a biological treatment tank and aerobically biological treatment and adding an inorganic coagulant to the biological treatment water flowing out of the biological treatment reactor outlet, , The pH of the biological treatment water in the outlet region in the biological treatment bath is set to 7.3 or less.

The coagulation treatment water may be passed through the reverse osmosis membrane separation device and treated.

In the present invention, the pH of the biological treatment water in the outlet region in the biological treatment bath is preferably 6.3 to 7.3, particularly preferably 6.5 to 6.9.

In the present invention, the biological treatment tank may have a plurality of stages of biological treatment zones, and the pH of the biological treatment water in the exit zone of the final stage biological treatment zone may be set to 7.3 or less.

In this case, the pH of water in at least a part of the biological treatment area other than the biological treatment area at the final stage may be 7.3 or more, preferably 7.5 to 8.5.

The organic wastewater is preferably a wastewater which consumes alkali in biological treatment.

The flocculant is preferably an iron flocculating agent and / or an aluminum flocculating agent.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the method for treating organic wastewater of the present invention will be described in detail.

[Organic drainage]

In the present invention, the organic wastewater to be treated is not particularly limited as long as it is an organic matter-containing wastewater usually subjected to biological treatment, and examples thereof include an industrial wastewater, a chemical plant wastewater, and a food factory wastewater. For example, in the electronic component manufacturing process, various organic wastewater is generated from a developing process, a peeling process, an etching process, a cleaning process and the like in a large amount, and further, the wastewater is required to be recovered to be purified and reused at a pure water level. Are suitable as the subject wastewater of the present invention.

Examples of such organic wastewater include organic wastewater containing isopropyl alcohol, ethyl alcohol and the like, organic nitrogen such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH), organic wastewater containing ammonia nitrogen, dimethyl sulfoxide (DMSO), and the like.

Particularly, the present invention is effective for organic wastewater which consumes alkali in biological treatment. That is, when aerobic biological treatment of organic wastewater containing organic nitrogen and ammonia nitrogen is performed, nitric acid and / or nitrite are produced by nitrification reaction, and when biological wastewater containing organic sulfur compounds is aerobically treated, And the generated acid consumes alkali. When the alkali is consumed, the pH is lowered and the treatment activity of the organism is lowered. Therefore, when such waste water is subjected to biological treatment, alkali is added to the biological treatment tank so that the pH is maintained at 7.5 or higher, 8.5, and keeping the biological activity, high processing ability can be obtained.

As the organic wastewater which consumes alkali in the biological treatment, for example, wastewater such as Kj-N (Kjeldahl nitrogen) concentration of 5 mg / L or more, particularly 10 to 1000 mg / L can be mentioned.

The effect of the present invention can be effectively obtained by adjusting the pH of the outlet region to 7.3 or less even when the region on the upstream side of the outlet region of the biological treatment reaction tank is adjusted to pH 7.5 or more suitable for biological treatment.

[Biological Treatment Reactor]

As the aerobic biological treatment tank for aerobic biological treatment of organic wastewater, various biological treatment biological treatment tanks can be used. For example, a floating system in which activated sludge is kept in a floating state in a tank, a biofilm system in which activated sludge is attached to a carrier and the like can be adopted. The biofilm system may be any microbiological system, such as a fixed-bed system, a fluid-bed system, and a spread-spectrum system. In addition, activated carbon, various plastic carriers, sponge carriers, etc. may be used as the carrier.

In the floating system, it is preferable to provide a solid-liquid separating means for separating the activated sludge from the treated water. For example, it is preferable to provide a solid-liquid separating means such as a sedimentation tank and a membrane separator at the rear end of the biological treatment tank. In another method, since the activated sludge is maintained in the biological treatment tank, such solid-liquid separation means can be omitted.

As the carrier, a sponge carrier is preferable. The sponge carrier can maintain microorganisms at a high concentration. The material of the sponge is not particularly limited, but an ester-based polyurethane is suitable. The amount of the carrier to be added is not particularly limited, but it is generally preferable that the apparent capacity of the carrier relative to the coagulating capacity of the biological treatment tank is about 10 to 50%.

The biological treatment reaction tank used in the present invention is a reaction tank for microbially decomposing organic matter in an aerobic state, and is an aeration tank provided with an oxygen gas supply means such as an oxidizer or a blower for supplying oxygen (air) to the tank.

This biological treatment tank may be composed of only one tank or a plurality of tanks connected in series. The partition wall may partition the inside of the biological treatment tank into a plurality of areas and the liquid may flow sequentially from the upstream area to the downstream area.

[pH adjustment]

In the present invention, in the biological treatment tank, the pH of the vicinity of the outlet where the biological treatment water is discharged from the reaction tank (the outlet region of the tank, hereinafter sometimes simply referred to as the "outlet region") is 7.3 or less, preferably 6.5 to 7.1, More preferably 6.5 to 6.9. When the pH of the outlet region is less than 6.5, the activity tends to decrease in the conventional biological treatment and the removal of dissolved organic substances becomes insufficient. As a result, in order to obtain water having a low FI value described later, A coagulant is required. If the adjusted pH exceeds 7.3, organic matter can be removed by biological treatment, but a large amount of inorganic coagulant is also required to obtain water with a low FI value. When the adjusted pH is 7.3 or less, particularly pH 6.5 to 6.9, sufficient flocculation effect can be achieved even when the amount of the inorganic flocculant added is small in the flocculation treatment at the downstream stage, and water with low FI value can be obtained.

In the present invention, any of the areas in the biological treatment bath may be adjusted to the above-mentioned pH. In the case where a plurality of biological treatment areas are formed by partitioning the inside of the biological treatment bath by a partition wall, It is preferable that at least the outlet region of the region has a pH of 7.3 or less, preferably 6.5 to 6.9, and the other front-end bioprocessing region is higher than pH 7.3. In this case, it is preferable that the other area than the exit area is adjusted to a pH suitable for biological treatment. When the biological treatment tank is constituted by a plurality of tanks connected in series, it is preferable to set the pH of the tank other than the final tank at pH 7.5 or more suitable for biological treatment, and at least the outlet region of the final tank to be pH 7.3 or less. The pH of the final step may be not more than 7.3, the pH of the outlet region may be not more than 7.3, and the pH of the solution other than the outlet may be at least 7.5.

That is, organic wastewater which consumes alkali such as organic wastewater containing organic nitrogen or ammonia nitrogen as described above and organic wastewater containing organic sulfur compounds is added to the biological treatment tank at a pH of 7.5 or higher, for example, about 7.5 to 8.5 It is preferable to form a plurality of stages of biological treatment zones in the case of treating such organic wastewater and to set only the outlet region of the last biological treatment zone at pH 7.3 or less, preferably 6.5 to 6.9, It is preferable that the pH of the biological treatment area is 7.5 or more. This region may be formed by partitioning the inside of the biological treatment reaction tank as described above, or may be formed by constituting a biological treatment reaction tank by a plurality of tanks connected in series.

The method of adjusting the pH of the outlet region is not particularly limited, but a method of adding an acid to the biological treatment tank is simple. As the acid, various inorganic acids such as hydrochloric acid and sulfuric acid are preferably used. The acid is usually added to the outlet region in the biological treatment reaction tank, but may be added to the front (inlet region) of the biological treatment reaction tank or to the front end of the biological treatment reaction tank. As a method for adjusting the pH by the addition of an acid, more specifically, a method of controlling the acid injection amount added to the biological treatment reaction tank by measuring the pH of the outlet region of the biological treatment reaction tank or the pH of the biological treatment water flowing out of the biological treatment reaction tank .

In addition, the acid should be added to the water in the biological treatment tank, and the effect of the present invention can not be obtained even when acid is added to the water flowing out of the biological treatment tank.

[Coagulation Treatment]

Various flocculation treatment apparatuses are used for coagulation treatment of biological treatment water obtained by aerobic biological treatment of organic wastewater in a biological treatment tank. The flocculation tank of this flocculation treatment apparatus may have only one set or two floats.

Examples of the inorganic flocculant for use in the flocculation treatment include iron flocculants such as ferric chloride and ferric polysulfate, aluminum flocculants such as aluminum sulfate, aluminum chloride and polychlorinated aluminum, but iron flocculants are preferable in terms of flocculation effect . These inorganic coagulants may be used alone, or two or more of them may be used in combination.

In the coagulation treatment, a pH adjuster is added as needed to adjust the pH to an appropriate level for the inorganic coagulant to be used. That is, as the pH condition, it is effective to react, for example, an iron-based flocculant at a pH of 5.5 or less. As the aluminum flocculant, it is effective to adjust the pH of the flocculant at pH 6.0 or higher after the reaction at pH 5.0 or lower. To adjust the pH. Although the details of the reason for obtaining a favorable treated water quality by the coagulation treatment under such pH conditions are not clear, it is presumed that the charge of the protein component in the biomass is neutralized.

By coagulation treatment, dissolved organics or suspensions in biological treatment water are flocized. An inorganic flocculant may be added to the first flocculation tank and a polymer flocculant to the second flocculation tank to grow the flocculated floc.

The resulting coagulated flocs are separated from the treated water by solid-liquid separation. As the solid-liquid separating means, sedimentation, pressurized floatation, or the like can be used. However, since the coagulated flocs of the biologically treated water are easily floated and separated, and the apparatus can also be used as a small-area apparatus in comparison with the sedimentation tank,

[Reverse osmosis membrane treatment]

The flocculation treatment water may further be passed through a reverse osmosis (RO) membrane separation apparatus to treat the RO membrane.

In this case, it is preferable that the flocculation treatment water is passed through a filter and subjected to filtration treatment in order to remove the residues (SS) in the flocculation treatment water prior to the RO membrane treatment. As the filter, there can be used a packed bed filter filled with a yellowing material such as sand or anthracite, a membrane filter using a membrane such as a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, or the like. As a result, water in the coagulation bath may be directly filtered.

As the RO membrane separation apparatus, any conventional apparatus can be used.

In the present invention, it is possible to obtain a flocculation treatment water having a low FI value with an added amount of a small amount of inorganic flocculant and to supply it to the RO membrane separator. Therefore, the deterioration of the membrane flux of the RO membrane separator can be suppressed, ) Can be obtained.

Further, the FI value is used as an index for judging whether or not the water quality of the water supplied to the RO membrane separator when water is passed through the RO membrane separator and deionized is suitable for RO membrane treatment. Even though the amounts of dissolved organic matter and SS in the coagulation treatment water are substantially the same, there is a case in which the film flux is initially lowered or not lowered by RO film treatment. In such a case, a difference occurs in the F1 value of the RO series .

The FI value can be obtained from an initial required time and a required time after passage of a predetermined time by performing an operation of measuring the time required for filtering a predetermined amount of water through a membrane filter having a predetermined pore diameter, Membrane fouling, membrane clogging, or water quality that is difficult to cause. In general, even water quality having an FI value of 5 or less may be accepted as an RO grade, but water quality of an FI value of 3 or less is generally required. Therefore, in the present invention, it is preferable to subject the biological treatment water to coagulation treatment to obtain water having an FI value of 3 or less, and this treatment is RO membrane treatment.

[Flow of Processing Apparatus]

Hereinafter, the flow of a processing apparatus suitable for the practice of the present invention will be described with reference to the drawings.

Fig. 1, Fig. 2 and Fig. 3 are schematic diagrams showing a treatment apparatus suitable for carrying out the method of treating organic wastewater of the present invention.

1, an aerobic biological treatment tank (aeration tank) 1 is provided with an acid furnace 1A, and the carrier 1B is charged into the tank. A screen 1C is provided in the biological treatment water outlet of the biological treatment tank 1 and a pipe 1D for injecting acid into the biological treatment tank 1 is provided on the upstream side of the screen 1C. Is installed.

Stirrers 2A and 3A are provided in the first flocculation tank 2 in which the effluent from the aerobic biological treatment tank is introduced and in the second flocculation tank 3 in which the effluent from the first flocculation tank is introduced. An inlet pipe 2B for the inorganic flocculant is provided in the first flocculating tank 2 and an inlet pipe 3B for the pH adjusting agent and the polymer flocculant is provided in the second flocculating tank 3.

A solid-liquid separating tank (pressurized float bath) 4, a filter 5 and a RO membrane separator 6 are provided at the downstream of the second flocculation tank 3.

The organic wastewater is introduced into the aerobic biological treatment tank (1), subjected to biological treatment under exhalation conditions, and biological treatment water is discharged. The pH of the biological treatment water in the outlet region is adjusted to 7.3 or less, preferably 6.5 to 6.9 by adding acid from the piping 1D to the outlet region in the biological treatment tank 1. [ The biological treatment water is then flocculated with the inorganic flocculant added to the first flocculation tank (2), and further the pH adjusting agent and the polymer flocculant are added to the floc in the second flocculating tank (3). The flocculation treatment water in the second flocculation tank 3 is fed to the next pressurized flotation tank 4 and the flocculated flocs are separated by solid-liquid separation. The separated water of the pressurized portion auxiliary tank 4 is removed by the filter 5 to remove residual SS and then treated with RO membrane by the RO membrane separator 6 so that the permeate is taken out as treated water.

The aerobic biological treatment tank 11 shown in Fig. 2 is a floating biological treatment tank, and has an acid pipe 11A. Three biological treatment regions 11a, 11b, and 11c are formed in the bath 11 by partition walls 11B and 11C. The multiple flows in the order of the regions 11a, 11b, and 11c. An acid injection piping 11D is provided in the final region 11c of the biological treatment tank 11 so that only the final biological treatment region 11c is adjusted to pH 7.3 or lower, have. The biological treatment water in the biological treatment tank 11 is subjected to solid-liquid separation in the sedimentation tank 12, a part of the separated sludge is discharged to the outside of the system as surplus sludge and the remainder is transported to the inlet side of the biological treatment tank 11 do. The separated water of the settling tank 12 is treated by the first flocculating tank 2, the second flocculating tank 3, the solid-liquid separating tank 4, the filter 5 and the RO membrane separator 6 as in Fig. 1 .

FIG. 3 shows a biological treatment tank in which a plurality of biological treatment tanks are provided in a multistage manner and the biofilm tanks 21 and 22 are provided with acid tanks 21A and 22A and biofiltration layers 21B and 22B, respectively . A piping 22C for injecting acid is provided in the inlet piping of the biological filtration tank 22 at the downstream end so as to adjust the biological treatment water of the biological filtration tank 22 to pH 7.3 or lower, preferably pH 6.5 to 6.9 have. The biological treatment water of the biological filtration tank 22 is supplied to the first flocculation tank 2, the second flocculation tank 3, the solid-liquid separation layer 4, the filter 5, the RO membrane separator 6, Lt; / RTI >

1 to 3 is an example of a treatment apparatus that can be employed in the present invention. The present invention is not limited to any of the illustrated methods, and, as described above, in the biological treatment reactor or the flocculation tank, Various other shapes can be adopted.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, reference examples and comparative examples.

Examples 1-3

The organic wastewater treatment was carried out by the apparatus shown in Fig. 1 according to the present invention. The water quality of the treated organic wastewater and the specifications and operating conditions of the aerobic biological treatment tank (1) and the flocculation tank (2, 3) used were as follows and treated at a throughput of 2400 L / day. As the filter 5, a sand filter was used.

Further, the pH of the outlet region was adjusted by adding HCl as an acid to the outlet region in the aerobic biological treatment tank (1). The pH in the reaction tank (1) other than the outlet region was 7.5.

The water quality of the biological treatment water (the water quality of the aeration tank effluent) and the quality of the flocculation treated water (after the second flocculation tank effluent was set for 30 minutes, the water filtered with the No. 5A filter paper was measured according to ASTM D 4189-95 The FI value measured in accordance with the present invention). The results are shown in Table 1.

On the basis of the results of Examples 1 to 3 and Comparative Examples 1 and 2 described later, in the case of the addition amount of the inorganic flocculant of 300 mg / L and the case of 400 mg / L, the set pH of the aeration tank and the FI Values are graphically shown in Fig.

[Organic drainage water quality]

Kj-N: 38.2 mg / L

S-TOC: 352 mg / L

[Aerobic biological treatment tank (1)]

Joe capacity: 2400 L

Aperture: 200 L / min

Carrier: A 3 mm square sponge was added in an apparent volume of 50% of the crude volume

Setting of the outlet area of the aeration tank pH: 7.2 in Example 1, 6.8 in Example 2, 6.5

[First coagulation tank (2)]

Joe capacity: 50 L

Inorganic coagulant: 38 wt% ferric chloride solution, the amount of addition was as shown in Table 1

Proof pH: 3.0 to 5.0 (adjusted by addition of HCl)

Stirrer: flat blade 40 mm x 200 mm, 180 rpm

[Second coagulation tank (3)]

Joe capacity: 50 L

Stirrer: flat blade 40 mm x 200 mm, 60 rpm

Proof pH: 5.0 (adjusted by addition of NaOH)

Comparative Example 1

No acid was added to the aerobic biological treatment tank (1), and no acid was added to the effluent of the aerobic biological treatment tank (1). The same treatment was carried out except for this, and the bioprocess water quality and coagulated water quality were examined in the same manner, and the results are shown in Table 1. In addition, the pH of the aerobic biological treatment tank (1) and its effluent is 7.5.

Comparative Example 2

The same treatment was carried out except that the addition amount of the acid was increased and the pH of the outlet region in the aerobic biological treatment tank 1 was set to 6.0 and the biological treatment water and the flocculated water quality were examined in the same manner. Respectively.

Comparative Example 3

In Comparative Example 1, except that no acid was added to the aerobic biological treatment tank (1), acid was added to only the biological treatment water flowing out of the aerobic biological treatment tank (1), and the pH of the effluent was changed to 6.8 Were treated in the same manner, and the water quality of the biological treatment water and the coagulated water were similarly examined, and the results are shown in Table 1.

It can be seen from Table 1 and Fig. 4 that the addition amount of the inorganic coagulant to equalize the FI value, which is an index of the coagulation treatment effect, can be remarkably reduced only by adjusting the pH of the aeration tank inner area.

It can also be seen from the results of Comparative Example 3 that the effect of the present invention can not be obtained even when an acid is added to the number of the aeration tank outlets without adding an acid to the aerobic biological treatment tank (1).

According to the present invention, in the case of introducing organic wastewater into a biological treatment tank and aerobically biologically treating the biological wastewater, and adding an inorganic coagulant to the biological treatment water flowing out from the biological treatment reactor outlet to perform flocculation treatment, By setting the pH of the biological treatment water to a weak acidity of 7.3 or less, preferably 6.3 to 7.3, particularly preferably 6.5 to 6.9, a good flocculation effect can be obtained with a small amount of inorganic flocculant added.

Although the details of the mechanism for reducing the amount of the inorganic flocculant added and improving the flocculation state by making the pH of the biological treatment water in the outlet region in the biological treatment tank less than 7.3 are not clear, It is presumed that these conditions are modified by the conditions and the cohesiveness is improved.

According to the present invention, by a simple operation of adjusting the pH of the biological treatment water in the outlet region in the biological treatment tank by acid addition or the like, a special apparatus is not required and the amount of the inorganic coagulant used directly in the treatment cost can be greatly reduced have.

Claims (15)

A method for treating organic wastewater, comprising introducing organic wastewater into a biological treatment tank to aerobically biological treatment, adding an inorganic coagulant to the biological wastewater discharged from the biological treatment reactor outlet, A method for treating organic wastewater, wherein the pH of the biological treatment water in the outlet region in the biological treatment reaction tank is set to 6.5 to 7.3, and the coagulation treatment water is passed through a reverse osmosis membrane separation device, Wherein the biological treatment tank has a plurality of stages of biological treatment zones and the pH of the biological treatment water in the exit zone of the final stage biological treatment zone is set to 6.5 to 7.3, Wherein the pH of water in at least a part of the biological treatment area other than the biological treatment area at the final stage is more than 7.3 and less than 8.5. The method of treating organic wastewater according to claim 1, wherein the pH of the biological treatment water in the outlet region in the biological treatment bath is set to 6.5 to 6.9. The method of treating organic wastewater according to claim 1 or 2, wherein the organic wastewater has a Kj-N (Kjeldahl nitrogen) concentration of 5 to 1000 mg / L. The method of treating organic wastewater according to claim 1 or 2, wherein the coagulant is at least one of an iron-based coagulant and an aluminum-based coagulant. 4. The method of treating organic wastewater according to claim 3, wherein the coagulant is at least one of an iron-based coagulant and an aluminum-based coagulant. delete delete delete delete delete delete delete delete delete delete

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