KR101352247B1 - Apparatus for treating waste water - Google Patents

Abstract

The nitrogen compound and inorganic ion-containing wastewater treatment apparatus prevents scale precipitation due to insolubilization of inorganic ions in the nitriding tank in treating nitrogen compounds in the nitrogen compound and the inorganic ion-containing wastewater by performing nitrite-nitride. The treatment apparatus includes a nitriding tank 1 for aeration of wastewater containing a nitrogen compound and an inorganic ion to oxidize the nitrogen compound to nitrite nitrogen, scale preventing means 2 and 3 for suppressing scaling of the inorganic ion; It is provided with the pH adjuster addition means 2 for maintaining pH in the nitriding tank 1 neutral to alkaline.

Description

Drainage treatment device {APPARATUS FOR TREATING WASTE WATER}

The first invention relates to a wastewater treatment apparatus and a treatment method containing a nitrogen compound and an inorganic ion.

In the second invention, a wastewater containing nitrate nitrogen and / or nitrite nitrogen (hereinafter referred to as " (sub) nitrogen nitrogen ") and polyvalent inorganic ions is concentrated by a membrane separation device, and the concentrated water is biologically denitrified. It relates to an apparatus for denitrification by furnace.

The third and fourth inventions relate to a wastewater treatment apparatus containing an organic nitrogen compound and / or ammonia nitrogen, and more specifically, to treating wastewater containing inorganic ions in addition to the organic nitrogen compound and / or ammonia nitrogen. It relates to a processing device.

A method of treating nitrogen-containing wastewater, the method of biological denitrification, in which organic nitrogen containing ammonia nitrogen is nitrified biologically with nitrite nitrogen or nitrate nitrogen, and biologically reduced the nitrite nitrogen and nitrate nitrogen for denitrification. Is well known. When the wastewater is aerated and aerobic biologically treated by the nitriding step in the biological denitrification treatment, the organic nitrogen in the wastewater becomes ammonia nitrogen, and the ammonia nitrogen becomes nitrite nitrogen by ammonia oxidizing bacteria.

The nitrite nitrogen becomes nitrate nitrogen by nitrite oxidizing bacteria in nitriding process. In this nitriding step, the amount of oxygen required in the nitriding step is good by stopping the reaction in the step before the organic nitrogen is nitrated to nitrite nitrogen through ammonia nitrogen and the nitrite nitrogen is oxidized to nitrate nitrogen.

Amount of excess sludge is generated by eliminating the need for the addition of hydrogen donors such as methanol by denitrifying by nitrite nitrite with ammonia nitrogen using an autotrophic microorganism using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. This decreases.

Japanese Patent Laid-Open No. 2004-298841 discloses a method of performing nitrous acid-type nitriding by adjusting the concentration of residual ammonia nitrogen in a nitriding tank to be 50 mg-N / L or more.

Nitrite-nitride means that nitrite nitrogen occupies 50% or more among the nitrogen oxides (nitrite nitrogen and nitrate nitrogen) produced by the nitriding process. Suitable pH conditions for nitrous acid type nitriding are 7.5 to 8.5, which are higher than those for 6.5 to 7.5 which are suitable pH conditions for nitric acid nitriding which oxidizes ammonia nitrogen to nitrate nitrogen.

If the inside of the nitriding tank has a relatively high pH of pH 7.5 to 8.5 suitable for nitrite-type nitriding, when the raw water to be treated contains low solubility divalent or trivalent inorganic ions, they are either calcium carbonate or Precipitates as a solid (scale) of inorganic carbonate compounds, such as magnesium carbonate. If the scale precipitates in the nitriding tank, the amount of inorganic sludge in the biological sludge increases, or the amount of air supplied to the nitriding tank decreases due to the blockage of the air supply pipe, which makes it impossible to perform a stable treatment, and the treatment efficiency (treatment load) is lowered. The water quality deteriorates.

When nitrous acid type nitriding is performed, scale is likely to occur in the nitriding tank. That is, the pH in the nitriding tank is lowered by nitriding the ammonia nitrogen to an acidic nitrite nitrogen. When the pH of the ammonia-oxidizing bacteria is less than 6.5, the activity is significantly reduced, so that oxidation to nitrous acid does not proceed well. For this reason, adding a pH adjuster (alkali) is normally performed so that pH may be kept above neutral. If soluble inorganic ions are contained in the raw water to be treated, the inorganic ions are insolubilized as hydroxides or carbonates by this pH adjustment, and scale is precipitated. When the pH of the waste water is low, the inorganic carbonate compound and the hydroxide compound dissolved in the waste water are also scaled by pH adjustment. When carbonate and / or bicarbonate is added as a pH adjuster, inorganic ions become carbonates and are easily precipitated.

A method for treating nitrogen-containing wastewater, the method of biological denitrification in which organic nitrogen containing ammonia nitrogen is biologically nitrified with (h) nitrate nitrogen, and the (h) nitrate nitrogen is reduced biologically to nitrogen gas. Is well known. Prior to the biological denitrification, the nitriding liquid containing (a) nitrate nitrogen is concentrated by a membrane separation device, and denitrification of the concentrated water is also performed (Japanese Patent Laid-Open No. 6-142693). By concentrating the nitriding treatment liquid, it is possible to raise the concentration of (nitrous) nitrate nitrogen and perform biodenitrification efficiently.

When the nitriding treatment liquid is concentrated by a membrane separation device, if the nitriding treatment liquid contains polyvalent inorganic ions having low solubility such as calcium ions, the scale of calcium carbonate or the like precipitates and deposits on the membrane surface, and the amount of treatment of the membrane separation device. And treated water quality is lowered.

In the semiconductor manufacturing process and liquid crystal manufacturing process in the electronics industry, since many amines and ammonium, such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH), are used, these organic nitrogen compounds and / or ammonia nitrogen Drain containing water is being discharged.

The organic nitrogen compounds such as MEA and TMAH are decomposed by aerobic microbial treatment which is mixed with activated sludge and aerated, and the nitrogen content can be oxidized to nitric acid or nitrous acid type. Then, in order to remove nitrate nitrogen or nitrite nitrogen from the wastewater containing nitrogen oxides such as nitric acid, the separation means is separated into permeate and concentrated water by a separation means using a reverse osmosis membrane. The method of biologically denitrifying by a processing apparatus is conventionally performed (Japanese Patent Laid-Open No. 2000-70986).

However, in the above-described method, when the drainage contains divalent or trivalent inorganic ions such as calcium ions, aluminum ions, iron ions, etc. in addition to nitrate nitrogen and nitrite nitrogen due to organic nitrogen compounds, When the separation into permeate and concentrated water (hereinafter, "separation of permeate and concentrated water by reverse osmosis membrane" may be referred to as "RO membrane separation"), the scale of the inorganic ion is Precipitates and deposits on the membrane surface. For this reason, the increase in the amount of permeate that penetrates the reverse osmosis membrane gradually progresses, and the RO membrane separation becomes difficult.

The present invention can stably perform reverse osmosis membrane separation treatment and denitrification treatment by introducing a softening treatment step, and further, by adding calcium ions as inorganic ions to the denitrification tank, the denitrification treatment can be performed more stably at a higher load. It is an object to provide a wastewater treatment apparatus and a treatment method.

It is an object of the first invention to provide a nitrogen compound and an inorganic ion-containing wastewater treatment apparatus and a treatment method in which scale precipitation by inorganic ions is prevented in nitrite-nitriding a wastewater containing a nitrogen compound and an inorganic ion.

The nitrogen compound and the inorganic ion-containing wastewater treatment apparatus of the first aspect of the present invention include a nitriding tank for aerobic biotreatment of wastewater containing a nitrogen compound and an inorganic ion to oxidize the nitrogen compound with nitrite nitrogen, and scaling of the inorganic ion. And an anti-scaling means for suppressing the pH, and a pH adjusting agent adding means for maintaining the pH in the nitriding tank to neutral to alkaline.

The nitrogen compound and inorganic ion-containing wastewater treatment method of the first invention include a nitriding step of aerobic biotreatment of wastewater containing a nitrogen compound and an inorganic ion to oxidize the nitrogen compound with nitrite nitrogen, and the scale of the inorganic ion. It is provided with the scale prevention process for suppressing oxidation, and the pH adjustment process for maintaining pH in the said nitriding process to neutral to alkaline.

According to the first invention, scaling of inorganic ions in the nitriding tank is prevented.

After most of the ammonia nitrogen is converted to nitrous nitrogen by nitrite-type nitriding in the nitriding tank, the nitrification tank effluent is usually introduced into the denitrification tank, and the nitrite nitrogen is reduced to nitrogen gas by the denitrification bacteria. When the nitrogen compound concentration of raw water is low, it is preferable to concentrate a nitriding process liquid and to denitrify it once. For example, a membrane separation device (such as a reverse osmosis (RO) membrane separation device) is disposed at the rear of the nitriding tank, and the nitrate tank effluent containing nitrite nitrogen is introduced into the membrane separation device, and the concentrated water is separated into permeate and concentrated water. Denitrification. By concentration of the nitriding treatment liquid, the concentration of nitrous nitrogen is increased, and the biodenitrification is efficiently carried out. When the nitriding solution is concentrated, the amount of water introduced into the denitrification tank decreases, so that the denitrification tank is sufficient for a small volume.

In the case where the nitriding treatment liquid is subjected to the membrane separation treatment after the anti-scaling treatment, scale precipitation in the membrane separation apparatus is prevented.

In 1st invention, it is preferable to add carbonate and / or bicarbonate as a pH adjuster to a nitriding tank.

In 1st invention, the scale prevention means may remove inorganic ion in waste water, and may add a scale inhibitor.

In the first aspect of the invention, the nitriding tank is preferably used from the viewpoint of treatment efficiency to use a carrier for holding cells.

In the second aspect of the present invention, in the condensation of wastewater containing (a) nitrate nitrogen and polyvalent inorganic ions with a membrane separation device, and denitrification of the concentrated water with a biological denitrification device, insolubilization of the polyvalent inorganic ion in the membrane separation device It is an object of the present invention to provide a wastewater treatment apparatus containing a (nitric acid) nitrate and a polyvalent inorganic ion, which prevents scaling up and deterioration of the treated water amount and the treated water quality of the membrane separation apparatus.

The (nitrous) nitrogenous acid and polyvalent inorganic ion containing wastewater processing apparatus of 2nd invention is the scale which suppresses scaling of this polyvalent inorganic ion in wastewater containing nitrate nitrogen and / or nitrite nitrogen and a polyvalent inorganic ion. Means for adding an inhibitor, a membrane separation device for separating the wastewater to which the scale inhibitor has been added into permeate and concentrated water, and denitrifying nitrate nitrogen and / or nitrite nitrogen contained in the concentrate. It has a biological denitrification device to treat.

In 2nd invention, in performing membrane separation of (a) nitrate nitrogen and polyhydric inorganic ion containing wastewater by the membrane separation apparatus, the anti-scaling agent for suppressing scaling of polyhydric inorganic ion is added. Scale precipitation of polyvalent inorganic ions in the membrane separation device is prevented.

When a biodegradable scale inhibitor is used as this scale inhibitor, the unreacted excess scale inhibitor is decomposed | disassembled by the biological denitrification apparatus of a later stage, and a scale inhibitor is not contained in a treated water. In the subsequent biological denitrification apparatus, the anti-scaling agent is biodegraded, thereby releasing polyvalent inorganic ions in the biological denitrification apparatus. This polyvalent inorganic ion is contained in the sludge to increase the sludge settling.

In the second invention, the biological denitrification device is preferably a USB type biological denitrification device. The higher the sedimentation of the granules in the biological denitrification apparatus of the upflow sludge blanket (USB), the higher the sludge concentration in the denitrification tank. When the precipitation tank is provided at the rear end of the denitrification tank, when the sedimentation property of the sludge in the precipitation tank becomes high, the sludge is easily separated into solids.

In the second aspect of the present invention, when the anti-scaling agent is not biodegradable and polyvalent inorganic ions are not liberated in the biological denitrification apparatus, an inorganic compound may be added from outside the system to increase the settling properties of the sludge. Even when the sludge settling properties of the sludge cannot be sufficiently improved with polyvalent inorganic ions in the system, an inorganic compound may be added from outside the system to increase the settling properties of the sludge.

An object of the third and fourth inventions is to provide a wastewater treatment apparatus in which the scale does not adhere to the membrane surface of the reverse osmosis membrane even if the wastewater contains an inorganic ion.

The wastewater treatment apparatus of the third invention comprises softening means for softening wastewater containing inorganic ions while containing nitrate nitrogen or nitrite nitrogen, and the effluent from the softening means is passed through the reverse osmosis membrane into permeate and concentrated water. A reverse osmosis membrane separation means for separating and denitrification means for biologically denitrifying the concentrated water to obtain denitrified water.

The softening means ion-exchanges the inorganic ions in the drainage with sodium ions or the like to soften them. For this reason, when the effluent from the softening means is separated into permeate and concentrated water by the reverse osmosis membrane separation means, the scale of the inorganic ions does not precipitate on the membrane surface of the reverse osmosis membrane, and adhesion of the scale can be prevented. Therefore, separation of permeated water and concentrated water (RO membrane separation) by the reverse osmosis membrane can be performed smoothly, and the separated concentrated water can be supplied to the denitrification means for biological denitrification and then discharged.

The wastewater treatment apparatus of the fourth invention includes a wastewater supply means containing an organic nitrogen compound and / or ammonia nitrogen and an inorganic ion, and the wastewater from the supply means, and microbially decomposes the organic nitrogen compound by aeration treatment. Aeration tank for nitriding, solid-liquid separation means for solid-liquid separation of the mixed liquid in the aeration tank, softening means for softening the separated water separated by the solid-liquid separation means, and effluent from this softening means are concentrated with permeate water by a reverse osmosis membrane. Reverse osmosis membrane separation means for separating into water, and denitrification means for biologically denitrifying the concentrated water to obtain denitrified water.

In the aeration tank, organic nitrogen compounds such as MEA and TMAH are microbially decomposed into nitrate nitrogen and nitrite nitrogen, and solid-liquid separation is performed by solid-liquid separation means. The solid-liquid separated water contains inorganic ions in addition to nitrate nitrogen and nitrite nitrogen, but is softened by ion-exchanging inorganic ions with sodium ions by a softening means for subsequent treatment. Even if the permeate membrane is separated into permeate and concentrated water, the scale of the inorganic ions does not precipitate on the membrane surface, and adhesion of the scale can be prevented. Therefore, separation of the permeate and the concentrated water (membrane separation) by the reverse osmosis membrane can be performed smoothly, and the denitrified water can be discharged by biological denitrification by supplying the separated concentrated water to the denitrification means.

In the wastewater treatment apparatus of 3rd, 4th invention, it is preferable to provide the supply means which supplies the said denitration process water to the said aeration tank. Accordingly, the denitrified water is used as a means for assisting the pH adjuster in the aeration tank.

In the wastewater treatment apparatus of 3rd, 4th invention, it is preferable that the said aeration tank is filled with the carrier which carries a microorganism. It is preferable to further provide a regeneration drainage supply means for feeding a part or all of the regeneration wastewater containing the inorganic ions discharged from the softening means to the denitrification means. The denitrification means is preferably a denitrification tank in which denitrification bacteria form sludge particles.

According to the wastewater treatment apparatus of the third and fourth inventions, the softening means is softened by ion-exchanging inorganic ions such as calcium ions, aluminum ions, and iron ions with sodium ions, and the like. Even if separated into permeate and concentrated water, the scale of the inorganic ion does not precipitate on the membrane surface, and adhesion of the scale can be prevented. For this reason, the separation (membrane separation) of permeate and concentrated water by a reverse osmosis membrane can be performed smoothly.

According to the present invention, the reverse osmosis membrane separation treatment and the denitrification treatment can be performed stably by introducing a softening treatment step, and the denitrification treatment can be stably performed at a higher load by adding calcium ions as inorganic ions to the denitrification tank. .

BRIEF DESCRIPTION OF THE DRAWINGS The systematic diagram which shows embodiment of the nitrogen compound and inorganic ion containing wastewater treatment apparatus of 1st invention.
FIG. 2 is a system diagram showing an embodiment of a (nitrous) nitrate nitrogen and polyvalent inorganic ion-containing wastewater treatment apparatus of the second invention. FIG.
3 is a block diagram showing a wastewater treatment apparatus of a third invention.
4 is a block diagram showing a wastewater treatment apparatus of a third invention.
Fig. 5 is a block diagram showing the wastewater treatment apparatus of the third invention.
6 is a block diagram showing a wastewater treatment apparatus of a fourth invention.
7 is a block diagram showing a wastewater treatment apparatus of a fourth invention.
8 is a block diagram showing a wastewater treatment apparatus of a fourth invention.
9 is a block diagram of a comparative example.
10 is a characteristic diagram showing the sedimentation rate of the granules of Examples 3 to 5;

EMBODIMENT OF THE INVENTION Below, with reference to drawings, embodiment of the nitrogen compound and inorganic ion containing wastewater treatment apparatus and treatment method of a 1st invention is described in detail.

BRIEF DESCRIPTION OF THE DRAWINGS It is a systematic diagram which shows embodiment of the nitrogen compound and inorganic ion containing wastewater treatment apparatus of 1st invention.

In the first aspect of the invention, the inorganic ion is, is insoluble in water-based and easy ions to scaled to be contained in the treated water drain, typically, a bivalent to trivalent cations, such as Ca ^{2 +,} Mg ^{2 +,} Fe ^{3 +,} it may be mentioned ions such as Al ^{+ 3.} These inorganic ions are scaled up when there are paired ions, such as hydroxyl ions, carbonate ions, phosphate ions, and fluorine ions, which are easily insolubilized.

In the first invention, the nitrogen compound contained in the waste water to be treated is organic nitrogen such as ammonia, ammonium compound or amine compound such as TMAH (tetra methyl ammonium hydroxide), MEA (monoethanol amine) or other amino acids. These organic nitrogens are oxidized to nitrite nitrogen via ammonia nitrogen in the nitriding process.

Examples of the wastewater to be treated in the first invention containing the inorganic ion and the nitrogen compound include liquid crystal plant drainage and semiconductor plant drainage.

Raw water consisting of nitrogen compounds and inorganic ion-containing wastewater is introduced into the nitriding tank 1 from the pipe 11, and aerobic biological treatment is performed by aeration or the like to conduct nitrous acid-nitriding. The nitriding tank 1 is provided with a scale preventing means for suppressing scaling of inorganic ions.

Examples of the scale preventing means include an anti-scaling agent adding means 2 shown in FIG. 1A and an inorganic ion removing means 3 provided at the front end of the nitriding tank 1 shown in FIG. 1B. Can be. As the anti-scaling means, both the anti-scaling agent adding means and the inorganic ion removing means may be employed.

As shown in Fig. 1 (a), when the scale inhibitor is added as the scale prevention means, scaling of the inorganic ions in the nitriding system is suppressed by adding the scale inhibitor to the raw water. As shown in FIG. 1 (a), the raw water introduction pipe 11 to the nitriding tank 1 may be used, the nitriding tank 1 may be used, or both.

Examples of the anti-scaling agent to be added include biodegradable anti-scaling agents such as polymer dispersants such as polyacrylic acid, polymaleic anhydride, polyacrylamide hydrolyzate and sulfonic acid polymers, phosphonates, inorganic polyphosphates, and EDTA (ethylene diamine tetraacetic acid). Chelating inhibitors, such as these, can be used. These scale inhibitors may be used individually by 1 type, and may mix and use 2 or more types.

The amount of the anti-scaling agent to be added may be such that the scale of inorganic ions can be suppressed, and in general, it is about 5 to 500 mg / L.

As the inorganic ion removing means 3, an ion exchange device, a crystallization device, an agglomeration separation device, or the like can be used.

The ion exchange device is an ion exchange column packed with a strongly acidic cation exchange resin or a weakly acidic cation exchange resin, and for example, a softening tower can be used. By passing raw water through an ion exchange column, the inorganic ion (cationic) can be removed by adsorption.

As a crystallizer, a crystal tower filled with seed material (for example, calcium carbonate, calcium phosphate, etc.) can be used. Insolubilizers (e.g., carbonates, phosphates, etc.) that react with inorganic ions to produce insoluble matters are added to raw water and passed through these crystal towers, whereby inorganic ions can be crystallized and removed from the seed phase.

As the flocculation separation apparatus, an insolubilizer (for example, alkali such as slaked lime) or a flocculant is added to the waste water to form an inorganic ion as a flocculation floc, and the flocculation floc can be removed by solid-liquid separation such as precipitation, flotation and filtration.

By the scale preventing means, the inorganic ions in the raw water are preferably removed at 1/10000 to 1/1, preferably 1/10000 to 9/10 of the saturation concentration, or the inorganic ions are dispersed to make the nitrile tank (1). To prevent scale precipitation.

When the membrane separation apparatus is arranged at the rear end of the nitriding tank and the nitriding tank effluent is concentrated, it is preferable to adjust the removal rate of the inorganic ions in accordance with the concentration magnification.

In the nitriding tank 1, a pH adjuster (alkali) is added by the pH adjusting means 4, and nitrite-nitriding is performed by maintaining the pH in the tank at a pH suitable for nitrous acid-type nitriding, that is, pH 7.5 to 8.5. As alkali added by the pH adjusting means 4, carbonates such as sodium carbonate and bicarbonates such as sodium bicarbonate are used, and the pH of the carbonate or bicarbonate is prevented from dropping in pH in the biofilm according to the pH buffering ability. It is desirable to maintain. However, strong alkalis such as sodium hydroxide (NaOH) may be added by the pH adjusting means 4.

A liquid in which exhaust gas containing carbon dioxide gas such as boiler exhaust gas is absorbed into an alkali chemicals such as caustic soda may be added to the nitriding tank 1 as water containing carbonate and / or bicarbonate.

In the nitriding tank 1, nitrous acid type nitriding is performed under neutral to alkaline pH conditions of pH 7.5 to 8.5, but since scale of inorganic ions in raw water is suppressed, precipitation of scale in the nitriding tank 1 is prevented. .

In the nitriding tank 1, a carrier 5 for holding the cells may be added. By the addition of the carrier, the cells are kept at a high concentration in the nitriding tank 1, whereby a more efficient treatment can be performed. As a carrier to add, it is preferable that it is sponge type and a large specific surface area. The carrier is preferably about 2 to 20 mm in size. The shape of the carrier is not particularly limited, and for example, a spherical or cuboidal one can be used. The material of the sponge may be an ester-based polyurethane, but is not limited thereto. The carrier is preferably added in an apparent volume of about 20 to 80% by volume of the volume of the nitriding tank 1.

In the present invention, even if the carrier 5 is added to the nitriding bath 1, the scale is prevented from adhering to the carrier.

The effluent of the nitriding tank 1 subjected to nitrous acid type nitriding is introduced into the membrane separation device 6 from the pipe 12 and concentrated, and then the concentrated water is added to the membrane nitrile tank (not shown) rather than the pipe 13. It is fed and biologically denitrified. Permeate of the membrane separation device 6 is discharged from the pipe 14 to the outside of the system.

Even in the case of membrane separation treatment of the nitriding treatment liquid, it is possible to prevent scale failure due to membrane separation concentration by the anti-scaling treatment at the front end.

As the membrane separation device 6, for example, a two-stage processing device of a micro filter membrane and an RO membrane, an RO membrane separation apparatus, or the like can be used.

In the first aspect of the invention, since ammonia-oxidizing bacteria are dominant in order to perform nitrite-nitriding, carbonate and / or bicarbonate are added to the nitriding tank to maintain the inorganic carbon concentration in the nitriding tank at 50 mg-C / L or more. As in Japanese Patent Laid-Open No. 2004-298841, a method of adjusting the residual ammonia nitrogen concentration in the nitriding tank to 50 mg-N / L or more (method of using an ammonia nitrogen inhibitory action), and other inhibitors The method of injecting, the method using the difference of the growth rate of a cell by a set temperature, the method of adjusting dissolved oxygen (DO) concentration, etc. can be employ | adopted.

An Example and a comparative example are given to the following, and 1st invention is demonstrated more concretely.

Example 1

The wastewater of 45 mg / L of Ca ion and 100 mg / L of K-N (Kjeldahl nitrogen) was passed through the apparatus shown in FIG. 1 (a) as raw water at the flow volume of 1000 L / d, and it processed. In addition, operation in the object drainage started after the apparatus of each process was operated, and the processing capacity became normal state. The operating conditions of each process are as follows.

Means for adding anti-scaling agents: 300 mg / L of sodium polyacrylate

Nitriding tank: volume 100 L

         pH 7.5

        Temperature 30 ℃

        30 vol% of each 3 mm sponge is added as a carrier

        pH adjusting sodium carbonate

        Inorganic Carbonate Concentration in Tank (Setting Value) 60 mg / L

Membrane Separator: RO Membrane `` NTR 759 HR-S2 '' by Nitto Denko

              (Pretreatment: Two-layer filtration (LV = 1 m / h) with slime control agent)

              RO membrane inlet pressure 1.3 MPa

              RO membrane outlet pressure 1.25 MPa

              Circulating water 6 L / min

              Permeate Flow Rate 0.7 L / min

              Set concentration water 0.3 L / min

              RO feedwater pH 6.0

Table 1 shows the results of investigation of the change over time of the inorganic sludge content of the sponge carrier in the nitriding bath, the water quality of the treated water of the nitriding bath, and the rate of decrease of the RO membrane flux (permeation flow rate) of the membrane separation device.

Driving days Nitrided water quality (mg / L) Organic sludge
Content (%) RO membrane flux reduction rate
(%) K-N (Keldal Nitrogen) Nox-n
Nitrite nitrogen 1 day 13 73 18 2.3 3 days 16 76 19 3.1 5 days - - 20 3.3 10 days 15 72 21 4.1

As apparent from Table 1, the ratio of the inorganic sludge in the sponge carrier in the nitriding tank did not increase, and the nitriding treatment could be continued for 10 days stably. In addition, in the RO membrane separation device, only 5% or less of flux was observed on the 3rd day from the start of operation, and the processing continued with 5% or less of the flux at the start of operation even on the 10th day from the start of operation. I can do it.

Comparative Example 1

In Example 1, the same treatment was conducted except that no anti-scaling agent was added, and the inorganic sludge content of the sponge carrier in the nitriding tank, the water quality of the treated water of the nitriding tank, and the RO membrane flux (permeation flow rate) lowering rate of the membrane separation device. The changes over time were investigated and the results are shown in Table 2.

Driving days Nitrided water quality (mg / L) Organic sludge
Content (%) RO membrane flux reduction rate
(%) K-N (Keldal Nitrogen) Nox-n
Nitrite nitrogen 1 day 23 64 26 23 2 days - - 42 30 3 days 56 36 51 40

As is also apparent from Table 2, in Comparative Example 1, the ratio of inorganic sludge in the sponge carrier was increased in the nitriding tank on the 3rd day from the start of operation, so that the specific gravity of the carrier was increased to settle in the tank. For this reason, oxygen could not be supplied sufficiently to the cells adhered to the sponge carrier, and the nitriding treatment capacity was lowered. In the RO membrane separation device, the scale gradually adhered to the membrane surface after the start of operation, and the flux decreased by 40% on the third day from the start of operation.

EMBODIMENT OF THE INVENTION Below, with reference to drawings, embodiment of the (a) nitrous acid nitrogen and polyvalent inorganic ion containing wastewater treatment apparatus of 2nd invention is described in detail.

FIG. 2 is a system diagram showing an embodiment of the (nitrous) nitrate-containing and polyvalent inorganic ion-containing wastewater treatment apparatus of the second invention. FIG.

In the second invention, the polyvalent inorganic ions is, is insoluble in water and easy ions to scaled to be contained in the treated water drain, typically, a bivalent to trivalent cations, such as Ca ^{2 +,} Mg ^{2 +,} Fe ^{3 +,} there may be mentioned ions such as Al ^{+ 3.} These inorganic ions are precipitated as a scale when there exist a pair of easily insolubilizing ions such as hydroxyl ions, carbonate ions, phosphate ions and fluorine ions. _{^{SO 4 2 -, PO 4 3}} -, CO 3 2 - and also an anion such as a screen scale. These anions are also contained in the polyvalent inorganic ion which concerns on this invention.

Examples of the wastewater to be treated containing inorganic ions and (a) nitrate nitrogen include a nitriding treatment liquid obtained by nitriding organic nitrogen-containing waste water such as liquid crystal plant drainage and semiconductor plant drainage. When organic nitrogen-containing waste water is nitrified, organic nitrogen such as ammonia, ammonium compounds, or amine compounds in the waste water, such as TMAH (tetra methyl ammonium hydroxide), MEA (monoethanol amine), and other amino acids, passes through ammonia nitrogen. (A) It becomes nitrate nitrogen.

(H) Nitrogen-nitrogen and polyvalent inorganic ion-containing waste water are introduced into the membrane separation device 22 from the pipe 31 as raw water, and a membrane separation treatment is performed. In order to suppress scaling of inorganic ions in the membrane separation device 22, a scale inhibitor is added to the raw water by the scale inhibitor addition means 21 provided in the raw water introduction pipe 31 into the membrane separation device 22.

As a scale inhibitor to add, what prevents a scale by microdispersion, a solubilization by chelate formation, etc. can be used. As bio-degradable scale inhibitors, for example, polymer dispersants such as polyacrylic acid, polymaleic anhydride, polyacrylamide hydrolyzate, sulfonic acid polymers, chelating agents such as phosphonates, inorganic polyphosphates, and EDTA (ethylene diamine tetraacetic acid) Can be used. As an easy biodegradable scale inhibitor, for example, polyaspartic acid, polyglutamic acid, polyalanine, polyleucine, polylysine, polyalginic acid and the like can be used. These scale inhibitors may be used individually by 1 type, and may mix and use 2 or more types.

When an easy biodegradable scale inhibitor is used, the unreacted excess scale inhibitor is decomposed by the biological denitrification apparatus 23 at the next stage. In the biological denitrification apparatus 23 at the next stage, the biodegradation agent of the scale prevents the release of polyvalent inorganic ions in the biological denitrification apparatus 23, and the polyvalent inorganic ions are accommodated in the sludge to increase the settling properties of the sludge. In the biological denitrification apparatus of an upflow sludge blanket (USB), the high sedimentation of granule sludge increases the sludge concentration in the denitrification tank. If the sludge has good sedimentation property, it is easy to settle the sludge in the sedimentation tank.

The amount of the anti-scaling agent to be added may be such that the scale of polyvalent inorganic ions can be suppressed, and the amount of the anti-scaling agent is appropriate depending on the concentration of the polyvalent inorganic ions of raw water, the treatment conditions (concentration ratio, etc.) of the membrane separation device 22, the type of anti-scaling agent to be used, and the like. But usually in the range of 5 to 500 mg / L.

In 2nd invention, by adding a scale inhibitor, the polyvalent inorganic ion in raw water is disperse | distributed and the precipitation of the scale in the membrane separation apparatus 22 is prevented.

As the separation membrane of the membrane separation device 22 into which the raw water to which the anti-scaling agent is added is introduced, (nitrous) nitrate can be concentrated. A reverse osmosis (RO) membrane, a nanofiltration (NF) membrane, or the like can be used. . The membrane separation device may be provided in two or more stages.

In the membrane separation device 22, the scale precipitation of polyvalent inorganic ions is prevented, so that the flux of the membrane can be maintained high for a long time, so that a stable and efficient membrane separation treatment can be continued.

The permeated water of the membrane separation device 22 is high purity water from which most salts and organics in raw water have been removed, and can be reused after being recovered from the pipe 32 as it is, or treated with necessary purity to further improve the water quality. have.

The concentrated water of the membrane separation device 22 is introduced into the biological denitrification device 23 from the pipe 33 and denitrified.

The biological denitrification device 23 may be suspended activated sludge, upflow sludge blanket (USB), or the like. The USB method is a method in which a granule having a diameter of 1 to several mm is formed by treating a carrier, calcium carbonate, or the like as a nucleus, and is advantageous in that the installation area is smaller than that of the floating activated sludge type, and the high load can be achieved.

In biological treatment, a small amount of inorganic ions is required for the growth and settling of microorganisms. When the biodegradable scale inhibitor which is easy as a scale inhibitor is used, polyvalent inorganic ion can be liberated and used by biodegradation of the scale inhibitor in a denitration process.

With the use of biodegradable anti-scaling agents, sufficient inorganic ions cannot be supplied in the denitrification process when the polyvalent inorganic ions form a chelate compound. Therefore, in this case, in order to supply inorganic ions, it is preferable to add a separate inorganic compound to the inlet of the biological denitrification device 23 or the biological denitrification device 23.

In the USB method, the sludge or granule inorganic ions are accommodated, and the specific gravity thereof is increased to prevent the sludge and the granule from being injured and leaked.

Calcium chloride, calcium hydroxide, etc. are preferable for the inorganic compound to add, The addition amount should just be a grade which can acquire required sludge settling property.

In the second invention, in this way, by securing the amount of inorganic ions in the biological denitrification apparatus 23, the sedimentation property of the sludge is increased, and the organic sludge ratio (VSS / SS) that accounts for all the sludge in the denitrification tank is 0.80 or less, for example. The denitrification treatment is preferably maintained at about 0.5 to 0.8.

There are no particular restrictions as to other treatment conditions in the biological denitrification device 23. In this biological denitrification apparatus 23, hydrogen donors, such as methanol, are added as needed.

The treated water of the biological denitrification device 23 is discharged from the pipe 34 to the outside of the system and further processed to be recovered, reused or discharged.

An Example and a comparative example are given to the following, and 2nd invention is demonstrated more concretely.

[Example 2]

A multiple of the degree of calcium ion concentration by the apparatus shown in 2, 45 mg / L, NO 3 -N concentration 160 mg / L as raw water, and treated by water flow at a flow rate of 200 L / d. Operation at the target drainage began after the equipment in each process had been operated and the processing capacity had reached a steady state. The operating conditions of each device are as follows.

Means for adding anti-scaling agents: 400 mg / L polyaspartic acid

Membrane separation device: `` NTR759 HR-S2 '' made by RO membrane Nitto Denko Corporation

              RO membrane inlet pressure = 1.3 MPa

              RO membrane outlet pressure = 1.25 MPa

              Circulating water amount = 6 L / min

              Set permeation amount = 0.7 L / min

              Set concentration water = O.3 L / min

              RO feed water pH = 6.0

Biological Denitrification Device: USB Method

                    Tank volume = 3.5 L

                    pH = 7.5

                    Temperature = 35 ℃

                    Hydrogen source: add 1400 mg / L methanol

At this time, the rate of decrease of the membrane flux in the membrane separation device and the VSS / SS ratio in the biological denitrification device and the change over time of the nitric acid (NO ₃ -N) concentrations of the inlet and outlet water of the biological denitrification device were investigated. The results are shown in Table 3.

Driving days
Flux reduction rate
(%)
VSS / SS Ratio NO ₃ -N concentration (mg / L) Biological denitrification inlet water Biological denitrifier outlet water 1 day 2.4 0.70 511 25 10 days 3.7 0.68 508 22 30 days 4.1 0.66 515 23

As apparent from Table 3, in the membrane separation device, only a decrease of 5% or less of the flux was observed on the 10th day from the start of operation, and continued on the 30th day with a decrease of 5% or less of the flux at the start of the operation. Could handle. In the biological denitrification apparatus, the ratio of the inorganic sludge to the whole sludge remained almost constant, and it was possible to stably denitrify at 90% or more of removal rate.

[Comparative Example 2]

In Example 2, treatment was carried out in the same manner except that no anti-scaling agent was added to reduce the membrane flux in the membrane separation device, the VSS / SS ratio in the biological denitrification device, and the inlet and outlet water of the biological denitrification device. Table 4 shows the results of investigating the change over time of the nitric acid concentration.

Driving days Flux Decay Rate (%) 1 day 21 5 days 35 10 days 42

As is apparent from Table 4, in Comparative Example 2, the flux of the membrane separation device gradually decreased due to the adhesion of the scale to the membrane surface every time the operating days passed, and on the 10th day, the flux was 40% or more compared with the start of operation. Or degraded.

EMBODIMENT OF THE INVENTION Hereinafter, the wastewater treatment apparatus of 3rd invention is demonstrated in detail, referring drawings.

3 is a block diagram showing a wastewater treatment apparatus of a third invention. The processing apparatus 41 shown in FIG. 3 is characterized by including a softening means 42, a reverse osmosis membrane separating means 43, and a denitrification tank 44 as a denitration means.

* The softening means 42 is supplied with drainage from the supply means 45. Drainage contains nitrate nitrogen and nitrite nitrogen resulting from organic nitrogen compounds such as MEA and TMAH, and contains divalent and / or trivalent inorganic ions such as calcium ions, aluminum ions and iron ions. The softening means 42 softens the inorganic ions in the waste water by ion exchange, and the reaction column is filled with a cation exchange resin. Therefore, by introducing wastewater from the upper portion of the softening means 42 and passing it through the reaction column, the wastewater is discharged from the lower portion of the softening means 42 after the inorganic ions contained are ion-exchanged with sodium ions. It is introduced into the reverse osmosis membrane separation means 43.

In the softening means 42, the concentration of inorganic ions is 1/10000 to 1/1 of the saturation concentration, more preferably 1/10000 to 9/10, depending on the concentration ratio in the reverse osmosis membrane separation step. To be removed.

The reverse osmosis membrane separation means 43 separates the ion-exchanged wastewater into the permeate 46 and the concentrated water 47 by the reverse osmosis membrane. Then, the permeated water 46 is reused as the recovered water, and the concentrated water 47 is introduced into the denitrification tank 44. The concentrated water 47 is introduced into the denitrification tank 44 together with organic substances such as methanol, and the introduced concentrated water 47 is subjected to biological denitrification to become the denitrification treated water 48, which is aerated and precipitated as necessary. After treatment, it is discharged.

As biological denitrification in the denitrification tank 44, a floating activated sludge method or an upflow sludge blanket (USB) method can be used. The USB method is a method of performing denitrification using sludge particles formed by denitrifying bacteria. That is, the denitrification treatment is carried out by forming granules having a diameter of 1 to several mm using a carrier, calcium carbonate, or the like as a nucleus, so that the concentrated water 47 from the reverse osmosis membrane separation means 43 is removed from the lower part of the denitrification tank 44. By introducing the concentrated water 47 into contact with the granules, the nitrate nitrogen and the nitrite nitrogen in the concentrated water 47 are decomposed and the denitrified water 48 is extracted from the upper portion of the denitrification tank 44. . This USB method has the advantage that the installation area is small and high load is possible compared to the floating activated sludge.

According to the processing apparatus 41 described above, even if the waste water contains inorganic ions, the inorganic ions are removed by ion exchange by passing through the softening means 42. For this reason, when the permeate and the concentrated water to the reverse osmosis membrane separation means 43 are separated (RO membrane separation), these inorganic ions become scale and do not precipitate and adhere to the membrane surface of the reverse osmosis membrane. Therefore, the separation of the permeated water and the concentrated water (RO membrane separation) by the reverse osmosis membrane can be performed smoothly, so that the drainage treatment can be performed quickly and efficiently.

4 is a block diagram showing another wastewater treatment apparatus 51 according to the third invention. The processing apparatus 51 shown in FIG. 4 is provided with the regeneration drainage supply means 49 in addition to the structure of FIG. One end of the regeneration drainage supply means 49 is connected to the upper portion of the softening means 42, and the other end thereof is connected to the denitrification tank 44. Further, the regeneration drainage supply means 49 includes a regeneration drainage storage tank 50 for storing the regeneration drainage.

The processing apparatus 51 of FIG. 4 can function similarly to the processing apparatus 41 of FIG. 3 by providing the softening means 42, the reverse osmosis membrane separation means 43, and the denitrification tank 44. As shown in FIG. In addition, in the processing apparatus 51 of FIG. 4, by providing the regeneration drainage supply means 49, backwash water 52 such as aqueous sodium chloride solution is introduced from the lower portion of the reaction column in the softening means 42, and the reaction is carried out. The inorganic ions trapped in the cation exchange resin in the column can be separated from the cation exchange resin. The water containing the separated inorganic ions becomes regeneration drainage and is stored in the regeneration drainage storage tank 50. Some or all of the stored regeneration water is supplied to the denitrification tank 44 together with the concentrated water 47 from the reverse osmosis membrane separation means 43.

Generally, biological denitrification in denitrification tank 44 requires a small amount of inorganic ions. In particular, in the USB method, the granules having high sedimentability are important for maintaining the nitrogen treatment load because the granules having high sedimentability are caused to rise and leak of the granules due to the deposition or inclusion of nitrogen gas generated. For this reason, it is effective to make inorganic granules into a granule or sludge and to increase specific gravity.

Since the softening means 42 uses an aqueous sodium chloride solution, the regeneration drainage contains inorganic ions such as calcium ions, magnesium ions and iron ions at high concentrations. The regeneration drainage supply means 49 supplies the regeneration drainage containing the inorganic ions in high concentration to the denitrification tank 44, so that the specific gravity of granules or sludge in the denitrification tank 44 can be increased. As a result, the denitrification in the denitrification tank 44 can be performed with high efficiency.

FIG. 5 is a block diagram showing still another wastewater treatment device 61 in the third invention. The processing apparatus 61 shown in FIG. 5 is equipped with the softening means 42, the reverse osmosis membrane separation means 43, and the denitrification tank 44 similarly to FIG. 3 and FIG. In addition, the processing apparatus 61 has a structure capable of supplying inorganic ions such as calcium compound (CaCl ₂ ) to the denitrification tank 44. The inorganic ions are introduced into the denitrification tank 44 by incorporation into the concentrated water 47 from the reverse osmosis membrane separation means 43. Thereby, like the processing apparatus 51 of FIG. 4, the specific gravity of the granule and sludge in the denitrification tank 44 can be enlarged, and the denitrification process in the denitrification tank 44 can be performed with high efficiency.

6 is a block diagram showing the wastewater treatment apparatus 71 according to the fourth invention. The processing apparatus 71 shown in FIG. 6 includes an aeration tank 72, a solid-liquid separation means 73 composed of a settling tank, a softening means 42, a filter 74, a reverse osmosis membrane separation means 43, And a denitrification tank 44 are provided. In the aeration tank 72, air is aerated inside from the diffusion means 75. The supply means 45 supplies wastewater to this aeration tank 72. Drainage is introduced into the aeration tank 72 in a state containing organic nitrogen compounds such as MEA, TMAH, and / or ammonia nitrogen and the inorganic ions described above.

In the aeration tank 72, the waste water is aerated by air aerated from the diffusion means 75. In this aeration treatment, the organic nitrogen compound is oxidatively decomposed by the microorganism, and the nitrogen component is nitrated to become nitrate nitrogen or nitrite nitrogen. The solid-liquid separation means 73 solid-separates the treatment liquid aerated in the aeration tank 72. A sludge conveying line 76 is provided between the solid-liquid separating means 73 and the aeration tank 72, and the separated sludge separated by the solid-liquid separating means 73 is conveyed to the aeration tank 72 through the sludge conveying line 76. . On the other hand, the separated fine water is supplied to the softening means 42.

As the softening means 42, clear water from the solid-liquid separation means 73 is introduced from the top and ion exchanged while passing through the reaction column. As a result, the inorganic ions contained in the clear green water are ion-exchanged with sodium ions, and the clear green water is softened.

The finely exchanged fine water is passed through the filter 74 to remove fine solids. As the filter 74, sand filtration, microfiltration, ultrafiltration, or other means can be used.

After passing through the filter 74, it is supplied to the reverse osmosis membrane separation means 43 and separated into permeate 46 and concentrated water 47. The permeated water 46 is reused as recovered water, and the concentrated water 47 is introduced into the denitrification tank 44 by adding organic substances such as methanol, and biologically denitrified in the denitrification tank 44. The denitrification-treated denitrification water 48 is re-aerated as necessary and precipitated, and then discharged.

In this processing apparatus 71, a feeding means 77 for feeding a portion of the denitrification treatment water from the denitrification tank 44 to the aeration tank 72 is provided. In this way, the denitrification treatment water 48 supplied to the aeration tank 72 by the feeding means 77 acts as a pH adjusting agent, and the pH of the wastewater from the supply means 45 can be smoothly adjusted.

In this treatment apparatus 71, even if the wastewater contains an organic nitrogen compound and / or ammonia nitrogen and an inorganic ion, the organic nitrogen compound is oxidatively decomposed and nitrided by the aeration tank 72, whereby nitrate nitrogen and nitrite nitrogen In this case, the denitrification tank 44 can perform denitrification efficiently. Moreover, since the softening means 42 which ion-exchange the clear supernatant from the solid-liquid separation means 73 is provided, an inorganic ion can be removed and the membrane surface of the reverse osmosis membrane in the reverse osmosis membrane separation means 43 is provided. Inorganic ions become scaled and do not attach. As a result, separation of the permeated water 46 and the concentrated water 47 by the reverse osmosis membrane (RO membrane separation) can be performed efficiently.

Although not shown, the inorganic ions trapped in the cation exchange resin of the softening means 42 may be separated and recycled as in FIG. 4, and some or all of the recycled wastewater may be supplied to the denitrification tank 44. . As a result, the specific gravity of granules and sludge in the denitrification tank 44 can be increased, and the denitrification treatment in the denitrification tank 44 can be performed with high efficiency.

7 is a block diagram showing another processing apparatus 81 of the fourth invention. In the processing apparatus 81 shown in FIG. 7, the carrier 82 which hold | maintained nitride bacteria with respect to the processing apparatus 71 of FIG. 6 is used, and this support 82 is introduce | transduced into the aeration tank 72. As shown in FIG. As the carrier 82 for holding the nitride bacteria, one having a large specific surface area such as foamed resin is used. Thus, by applying the carrier 82 which hold | maintained nitride bacteria to the aeration tank 72, it becomes possible to perform nitriding in the aeration tank 72 more efficiently.

In addition, in the processing apparatus 81 of FIG. 7, the aggregation reaction tank 83 and the aggregation precipitation tank 84 are used. The agglomeration reactor 83 is agglomerated by adding a flocculant to solids such as sludge which is separated from the carrier 82 in the aeration tank 72 and the suspended cells growing. The floc after the flocculation is supplied to the flocculation precipitation tank 84 and agglomerated. Solid-liquid separation is carried out by the settling tank 84. Thus, by using the aggregation reaction tank 83 and the aggregation precipitation tank 84, solid-liquid separation can be performed reliably and quickly.

8 is a block diagram showing still another wastewater treatment apparatus 91 of the fourth invention. The processing apparatus 91 shown in FIG. 8 uses the immersion membrane type aeration tank 92 instead of the aeration tank 72 of the processing apparatus 71 in FIG. The immersion membrane type aeration tank 92 uses an immersion membrane 93, and the immersion membrane 93 is in the state of being immersed in the drainage in the aeration tank 92. The treated water is filtered by the immersion membrane 93 and then supplied to the softening means 42. Therefore, in this processing apparatus 91, the solid-liquid separation means 73 in the processing apparatus 71 of FIG. 6 becomes unnecessary, and the installation area can be made small.

In this case, the inside of the aeration tank 92 is aerated by the diffusion means 75, and by disposing the immersion membrane 93 therein, the deposit on the surface of the membrane can be removed by aeration from the bottom. Therefore, the immersion film 93 can be stably operated for a long time. As the immersion membrane 93, an ultrafiltration membrane, a microfiltration membrane, or the like can be used, and as the material thereof, polyolefin, cellulose acetate, ceramic, or the like can be selected. Such an immersion film 93 can be repeatedly used by cleaning, which is economical.

A 3rd invention is concretely demonstrated by an Example and a comparative example. In the following examples and comparative examples, nitrogen removal treatment was performed by passing water at a flow rate of 200 L / d using a wastewater having a Ca ion concentration of 45 mg / L and a NO ₃ -N concentration of 80 mg / L as raw water. In addition, operation in the object drainage started after the apparatus of each process was operated, and the processing capacity became normal state. The operating conditions of each treatment step are as follows.

(1) Softening process: weakly acidic cation exchange resin (manufactured by Bayer Corporation, trade name "Lewatit CNP80"), SV70hr ^-1

(2) Membrane separation step: Reverse osmosis membrane (RO membrane) (manufactured by Nitto Denko Corporation, trade name "NTR759 HR-S2")

(3) Denitrification Process: USB Method (Upflow Sludge Blanket Method: Upflow Sludge Blanket Method, Denitrification Tank Volume 3.5 L, pH 7.5, Temperature 35 ° C., Methanol 240 mg / L

[Comparative Example 3]

The drainage process was performed by the flowchart shown in FIG. That is, the raw water not subjected to the softening process was separated into permeate 46 and concentrated water 47 by a reverse osmosis membrane, and the separated concentrated water 47 was denitrified by the denitrification tank 44. After the start of operation, the scale gradually adheres to the reverse osmosis membrane, and as shown in Table 5, the amount of permeated water (hereinafter referred to as flux) that is separated into the reverse osmosis membrane decreases by 26% at the first day compared with the start of operation. On the third day, the decrease was 42%.

Flux Decay Rate (%) Day 1 26 Day 2 33 Day 3 42

[Example 3]

The wastewater was processed by the flowchart shown in FIG. That is, after the wastewater is ion-exchanged with the softening means 42, it is passed through the reverse osmosis membrane separation means 43 and separated into the permeate 46 and the concentrated water 47, and the concentrated water 47 thereafter. Was introduced into the denitrification tank 44 to perform denitrification. The results are shown in Table 6.

As shown in Table 6, in Example 3, the flux reduction rate of the first day from the start of operation was reduced by only 2.1% compared to the start of the operation, and also decreased by only 3.1% and 4.3% on the 15th and 30th days, respectively. It was confirmed that 5% or less was maintained and separation of the permeate and the concentrated water by the reverse osmosis membrane was continued. In the denitrification process, the concentration of nitrate nitrogen in the treated water was gradually increased from the start of operation, but the nitrate nitrogen at 30 days from the start of operation was 86.5%, and 85% was maintained as the removal rate. Removal efficiency of nitrate nitrogen is, indicates the percent removal of the nitrate-nitrogen (NO ₃ -N) from the inflow water flowing into the denitrification process.

Flux Decay Rate (%)
NO ₃ -N (mg / L) in the denitrification process Influent Treated water Removal rate (%) Day 1 2.1 510 26 94.9 Day 15 3.1 503 48 90.5 Day 30 4.3 519 70 86.5

Example 4

The wastewater was processed by the flowchart shown in FIG. That is, after the wastewater is ion-exchanged with the softening means 42, it is passed through the reverse osmosis membrane separation means 43 and separated into the permeate 46 and the concentrated water 47, and the concentrated water 47 thereafter. Was introduced into the denitrification tank 44 to perform denitrification. In the denitrification treatment, the regeneration wastewater was mixed with the concentrated water 47 from the regeneration wastewater feeding means 9 and introduced into the denitrification tank 44. Sodium chloride (NaCl) was used for this regeneration agent. The results are shown in Table 7.

As shown in Table 7, in Example 4, even after 30 days from the start of operation, there was no significant increase in the rate of decrease of the flux, which was maintained at 5% or less, and also in the removal rate of nitrate nitrogen, there was usually no noticeable fluctuation. About 95%. Therefore, the reverse osmosis membrane separation treatment and the denitrification treatment could maintain the same treatment capacity and treated water quality as when the operation was started.

Flux Decay Rate (%)
NO ₃ -N (mg / L) in the denitrification process Influent Treated water Removal rate (%) Day 1 2.5 530 24 95.5 Day 15 3.9 512 28 94.5 Day 30 4.4 522 21 96.0

[Example 5]

The wastewater was processed by the flowchart shown in FIG. That is, after the wastewater is ion-exchanged with the softening means 42, it is passed through the reverse osmosis membrane separation means 43 and separated into the permeate 46 and the concentrated water 47, and the concentrated water 47 thereafter. Was introduced into the denitrification tank 44, and the calcium compound was added to the denitrification tank 44 to perform denitrification. Calcium chloride was used as a calcium compound. The results are shown in Table 8.

As shown in Table 8, in Example 5, even after 30 days from the start of operation, 5% or less was maintained without a significant increase in the rate of decrease of flux, and no significant change was observed in the removal rate of nitrate nitrogen. Usually about 95%. Therefore, the reverse osmosis membrane separation treatment and the denitrification treatment could maintain the same treatment capacity and treated water quality as when the operation was started.

Flux Decay Rate (%)
NO ₃ -N (mg / L) in the denitrification process Influent Treated water Removal rate (%) Day 1 1.9 521 28 94.6 Day 15 2.8 518 31 94.0 Day 30 4.1 529 23 95.6

FIG. 10 is a graph showing the trend of sedimentation velocity of granules in Examples 3 to 5. FIG. In Example 3, in which calcium ion was not contained in the water introduced into the denitrification tank 44, the sedimentation rate of the granule, which was 50 m / hr at the start of operation, was reduced to 40 m / hr at 30 days after the start of operation. On the other hand, in Example 4 and Example 5 with the addition of calcium ions it was possible to maintain the sedimentation rate of the granule at 50 m / hr even 30 days after the start of operation.

1: Nitride tank
2: pH adjuster addition means
3: inorganic ion removal means
4: pH adjusting means
6: membrane separation device
11: raw water introduction piping
21: means for adding a scale inhibitor
23: denitrification device
42: softening means
43: reverse osmosis membrane separation means

Claims (3)

Means for adding a readily biodegradable scale inhibitor for inhibiting scaling of the polyvalent inorganic ion to a wastewater containing at least one of nitrate nitrogen and nitrite nitrogen and a polyvalent inorganic ion;
A membrane separation device for separating the wastewater to which the scale inhibitor is added into membrane permeate and concentrated water;
A biological denitrification apparatus for denitrifying at least one of nitrate nitrogen and nitrite nitrogen contained in the concentrated water, wherein the denitrification apparatus for decomposing an unreacted easy biodegradable scale inhibitor is decomposed.
Lt; / RTI >
The readily biodegradable scale inhibitor is at least one selected from the group consisting of polyaspartic acid, polyglutamic acid, polyalanine, polyleucine, polylysine and polyalginic acid,
A drainage treatment apparatus containing at least one of nitrate nitrogen and nitrite nitrogen and a polyvalent inorganic ion. Means for adding an egg biodegradable antiscaling agent that inhibits scaling of the polyvalent inorganic ion to a wastewater containing at least one of nitrate nitrogen and nitrite nitrogen and a polyvalent inorganic ion;
A membrane separation device for separating the wastewater to which the scale inhibitor is added into membrane permeate and concentrated water;
A biological denitrification apparatus for denitrifying one or more of nitrate nitrogen and nitrite nitrogen contained in the concentrated water;
Means for adding at least one of calcium chloride and calcium hydroxide as an inorganic compound to water in the biological denitrification apparatus or the concentrated water introduced into the biological denitrification apparatus
/ RTI >
The egg biodegradable anti-scaling agent is at least one selected from the group consisting of polyacrylic acid, polymaleic anhydride, polyacrylamide hydrolyzate, sulfonic acid polymer, phosphonic acid salt, inorganic polyphosphate and EDTA (ethylene diamine tetraacetic acid). ,
A drainage treatment apparatus containing at least one of nitrate nitrogen and nitrite nitrogen and a polyvalent inorganic ion. The multivalent inorganic ion-containing wastewater treatment apparatus according to claim 1 or 2, wherein the biological denitrification apparatus is an upflow sludge blanket biological denitrification apparatus.

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