JP6743352B2 - Humin-containing wastewater treatment method and humin-containing wastewater treatment device - Google Patents

Description

The present invention relates to a humin-containing wastewater treatment method and a humin-containing wastewater treatment apparatus.

As a method of purifying wastewater containing a hydrophobic substance, a method of filtering wastewater using a filtration membrane such as a hollow fiber membrane is known (for example, Patent Documents 1 and 2).
As the filtration time becomes longer, dirt adheres to the filtration membrane and the filtration performance deteriorates. Therefore, normally, the filtration performance is recovered by regularly cleaning the filtration membrane. For example, a method of washing a filter membrane obtained by filtering oil-containing wastewater with a strong alkaline chemical such as sodium hydroxide (for example, Patent Document 3) or a mixed solution of chloric acid or its salt and a surfactant is used. There is known a method of cleaning by cleaning (for example, Patent Document 4).
However, although it is possible to wash the filtration membrane by these methods, it is important to prevent membrane clogging in order to perform stable wastewater treatment.

Humin is one of the substances that induce membrane blockage in wastewater containing hydrophobic substances. Examples of the method for removing humin in wastewater treatment by membrane filtration include the following methods (a) and (b).
(A) A method in which humin-containing waste water is subjected to membrane filtration by decomposing humin by causing ozone, ultrasonic waves, hydrogen peroxide, ultraviolet rays, or a photocatalyst to oxidize (for example, Patent Documents 5 to 7).
(B) A method in which a coagulant is allowed to act on humic acid-containing wastewater to cause humin to coagulate and precipitate to be removed from the wastewater, and then membrane filtration is performed (for example, Patent Documents 8 to 9).

JP-A-56-152781 JP-A-5-245472 JP, 2010-36183, A JP, 2013-31839, A JP-A-11-347587 JP, 2003-24957, A JP, 2003-88885, A JP, 2002-326088, A JP, 2002-346581, A

However, in the method (a), energy required for oxidation, facilities and reagents for operation, and the like require a great cost. Further, the method (a) was easily affected by impurities.
In the method (b), the use of the aggregating agent causes a problem that the amount of the agglomerated precipitate increases and the treatment cost of the agglomerated precipitate increases.
As described above, the above method has been studied as a method for removing humic substances in wastewater, but the above method consumes a large amount of energy and produces a large amount of industrial waste, which causes a rise in wastewater treatment cost. There was a problem.

The present invention aims to solve such conventional problems.
That is, an object of the present invention is to provide a method for easily removing humic acid from humic-containing wastewater and treating wastewater by membrane filtration with high stability, and a wastewater treatment apparatus.

The present invention has the following aspects.
[1] A method for treating humic-containing wastewater, which comprises the following steps (i) and (ii).
(I) A removal step of adjusting the pH of the humic-containing wastewater to 7 or less, insolubilizing the humin in the wastewater, and removing the insolubilized humin;
(Ii) Membrane filtration step in which the humic-free effluent obtained in step (i) is subjected to membrane filtration;
[2] The method for treating humic-containing wastewater according to [1], wherein the step (i) includes the following steps (i-1) to (i-3).
(I-1) Insolubilization step of adjusting the pH of the humic-containing wastewater to less than 5 to insolubilize the humin in the wastewater;
(I-2) A removal step of removing insolubilized humin from the wastewater obtained in the step (i-1);
(I-3) A neutralizing step of adding an alkali to the wastewater obtained in the step (i-2) to adjust the pH to 5 to 9 and neutralizing the wastewater;
[3] In the step (i), at least one of an inorganic acid and an organic acid is added to adjust the pH of the humic acid-containing wastewater to insolubilize the humic acid, and thus the humic acid-containing wastewater of [1] or [2]. Processing method.
[4] In the step (i), hydrochloric acid is added to adjust the pH of the humic acid-containing wastewater to insolubilize the humic acid, and the humic acid-containing wastewater is treated according to any one of [1] to [3]. ..
[5] The method for treating humic-containing wastewater according to any one of [1] to [4], wherein a coagulant is added in the step (i).
[6] The method for treating humic-containing wastewater according to any one of [1] to [5], wherein the step (ii) is a membrane separation activated sludge treatment combining biological treatment and membrane separation treatment.
[7] The method for treating humic-containing wastewater according to [6], wherein the biological treatment includes at least one selected from the group consisting of anaerobic treatment, anoxic treatment and aerobic treatment.
[8] The method for treating humic-containing wastewater according to [6] or [7], wherein the biological treatment includes anoxic treatment and aerobic treatment.
[9] In the biological treatment, the humic-containing wastewater treatment method according to [8], wherein a part of the sludge in the aerobic tank for aerobic treatment is returned to the anoxic tank for anoxic treatment.
[10] Any of [1] to [9], wherein the humic-containing wastewater is wastewater generated from a process including heat treatment in which a part of coal is gasified, or wastewater discharged from the livestock industry. The method for treating humic-containing wastewater according to one.

[11] An apparatus for treating humic-containing wastewater, comprising a insolubilizing tank for insolubilizing humin, a removing tank for removing insolubilized humin, and a membrane filtration device for membrane-filtering effluent-free effluent.
[12] The treatment device for humic-containing wastewater according to [11], further including a neutralization tank for neutralizing the wastewater from which humic acid has been removed.
[13] The treatment device for humic-containing wastewater according to [12], wherein the neutralization tank has a pH adjusting unit that adjusts the pH in the tank by adding an alkali.
[14] The treatment device for humic-containing wastewater according to [12] or [13], wherein the neutralization tank and the membrane filtration device are integrated.
[15] The treatment device for humic-containing wastewater according to any one of [11] to [14], which has pH adjusting means for adjusting the pH in the tank by adding an acid to the insolubilizing tank.
[16] The treatment device for humic-containing wastewater according to any one of [11] to [15], wherein the insolubilization tank and the removal tank are integrated.
[17] The treatment device for humic-containing wastewater according to any one of [11] to [16], wherein in the membrane filtration device, membrane separation activated sludge treatment that combines biological treatment and membrane separation treatment is performed.
[18] The treatment device for humic-containing wastewater according to [17], wherein the biological treatment includes at least one selected from the group consisting of anaerobic treatment, anoxic treatment, and aerobic treatment.
[19] The treatment device for humic-containing wastewater according to [17] or [18], wherein the biological treatment includes anoxic treatment and aerobic treatment.
[20] The treatment device for humic-containing wastewater according to [19], wherein in the biological treatment, part of the sludge in the aerobic tank that performs aerobic treatment is returned to the anoxic tank that performs anoxic treatment.

According to the method for treating humic acid-containing wastewater of the present invention, humic acid can be easily removed from humic acid-containing effluent and the effluent can be treated by membrane filtration with high stability.
Further, according to the treatment apparatus for humic-containing wastewater of the present invention, humic acid can be easily removed from humic-containing wastewater, and the wastewater can be treated with high stability by membrane filtration.

It is a schematic block diagram which shows an example of the processing apparatus of the humic-containing wastewater of this invention. It is a schematic block diagram which shows the other example of the processing apparatus of the humic-containing wastewater of this invention. It is a schematic block diagram which shows the other example of the processing apparatus of the humic-containing wastewater of this invention. It is a schematic block diagram which shows the other example of the processing apparatus of the humic-containing wastewater of this invention.

Hereinafter, an example of the method for treating humic-containing wastewater of the present invention will be described.
The humic acid-containing wastewater treatment method of the present invention is a method of performing membrane filtration after removing the humic acid from humic acid-containing wastewater, particularly humic acid-containing wastewater, and includes the following steps (i) and (ii).
(I) A removal step of adjusting the pH of the humin-containing wastewater to 7 or less, insolubilizing the humin in the wastewater, and removing the insolubilized humin;
(Ii) Membrane filtration step in which the humic-free effluent obtained in step (i) is subjected to membrane filtration;

<Humin-containing wastewater>
The humic-containing wastewater to be treated in the present invention is, for example, wastewater generated from a process including heat treatment in which a part of coal is gasified (hereinafter, also referred to as “coal heating wastewater”), or discharged from the livestock industry. It is wastewater containing human waste.

Examples of the coal heating wastewater include wastewater generated from each step in the coal carbonization step, the coal gasification step, the coal liquefaction step, the coke step, and the like.
The heating temperature in the heat treatment is generally about 450° C. in the Bergius method in the coal liquefaction step, 200 to 400° C. in the Fischer-Tropsch method, and about 900° C. or higher in the high temperature carbonization method in the coking step.
The gas generated by the heat treatment is recovered by cooling, a scrubber or the like, and subsequently separated, recovered and purified as various chemical species by steps such as fractional distillation and extraction.
It may also be used for water gasification, which is a reaction of heated coal and water, or for calcium carbide production.
Coal heating wastewater is wastewater generated by gas recovery, chemical species separation, recovery, refining, equipment cleaning, etc. in these processes, and may include domestic wastewater, industrial wastewater, water, seawater, and the like.
Examples of the substances contained in the coal heating wastewater include phenols, cyanides, ammonia, hydrogen sulfide ions, thiocyan, tar-like oil, hydrocarbon compounds and aromatic compounds.

Examples of wastewater containing human excrement discharged from the livestock industry include livestock urine generated from livestock facilities such as cattle, pigs, chickens or horses, drainage of breeding wastewater, or digested liquid obtained by fermenting these. ..
Since livestock urine contains a large amount of humic acid, the present invention is particularly effective when treating wastewater discharged from the livestock industry.

<Step (i)>
Step (i) is a removal step of adjusting the pH of the humic-containing wastewater to 7 or less, insolubilizing the humin in the wastewater, and removing the insolubilized humin.

(PH adjustment)
As a method for adjusting the pH of the humic-containing wastewater, addition of acid can be mentioned. Examples of the type of acid to be added include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; organic acids such as oxalic acid, citric acid, formic acid and acetic acid, and mixtures thereof.
Among these, hydrochloric acid or sulfuric acid, or a mixed solution thereof is preferable as the acid from the viewpoint of being an acid that hardly affects the water quality of wastewater, and hydrochloric acid is particularly preferable from the viewpoint of the influence on the generation of hydrogen sulfide and biological treatment. preferable.

The pH of the humic-containing wastewater is adjusted to 7 or less. If the pH of the humic-containing wastewater is 7 or less, the humic acid in the humic-containing wastewater becomes insoluble.
As the pH of the humic-containing wastewater becomes lower (that is, the more acidic the humic-containing wastewater becomes), the humic acid in the humic-containing wastewater tends to be insolubilized easily, and thus the insoluble humic acid is easily removed from the humic-containing wastewater. Therefore, from the viewpoint of humic acid removal efficiency, the lower the pH of the humic acid-containing wastewater, the more preferable.
However, if the pH of the humic-containing wastewater is low, the filtration membrane used in the step (ii) described below tends to deteriorate. In addition, since the wastewater (permeate) after membrane filtration may be discharged to rivers, etc., if the pH of the humic-containing wastewater is low, add alkali after removing the insolubilized humin from the humic-containing wastewater. Neutralization treatment is preferably performed. Therefore, it is preferable that the pH of the humic acid-containing wastewater is not too low in consideration of the amount of alkali added and the labor of the neutralization treatment.

Considering the amount of alkali added and the time and effort required for neutralization, the pH of the humic-containing wastewater is preferably 5 or more and 7 or less, and more preferably 5.7 or more and 6.9 or less. If the pH of the humic-containing wastewater is 5 or higher, the neutralization step can be omitted after removing insolubilized humic acid from the humic-containing wastewater or when the permeated water is discharged to a river or the like. Even when the treatment is performed, the amount of alkali added can be reduced, which is economical.

From the viewpoint of humin removal efficiency, the step (i) preferably includes the following steps (i-1) to (i-3).
(I-1) Insolubilization step of adjusting the pH of the humic-containing wastewater to less than 5 to insolubilize the humin in the wastewater;
(I-2) A removal step of removing insolubilized humin from the wastewater obtained in the step (i-1);
(I-3) A neutralizing step of adding an alkali to the wastewater obtained in the step (i-2) to adjust the pH to 5 to 9 and neutralizing the wastewater;

When the pH of the humic-containing wastewater is adjusted to be less than 5 in the step (i-1), the humic acid in the humic-containing wastewater becomes more insoluble. Therefore, insolubilized humin can be removed from the humic-containing wastewater in the step (i-2) with high efficiency.
However, as described above, when the pH of the humic-containing wastewater is low, the filtration membrane tends to deteriorate. Further, permeated water having a low pH is difficult to be discharged as it is to a river or the like. Therefore, in step (i-3), alkali is added to the wastewater obtained in step (i-2) to adjust the pH to 5 to 9, and the wastewater is neutralized.
Examples of the alkali include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, calcium carbonate and the like.

Examples of methods for removing the insolubilized humin include sand filtration, pressure floating separation, centrifugal separation, belt pressing, and sedimentation by a sedimentation tank.
Of these, in consideration of the continuity of treatment and the state of insolubilized humin, the method of removing insolubilized humin is preferably precipitation by a sedimentation tank.

In the present invention, the humin removed from the humic-containing wastewater by insolubilization is also called humic substance, so-called humic substance, or a polymer compound formed by polymerization of an organic compound such as an aromatic compound, which is mainly dark black. To a dark brown substance. Humin becomes insoluble in an acidic region of pH, as represented by humic acid. Humin exists as an organic pigment (coloring component) in wastewater, is difficult to decompose by biological treatment, and becomes a water pollutant as COD. Therefore, the present invention is also useful in wastewater treatment.

In step (i), a coagulant may be added. The timing of adding the coagulant is preferably from the time when the pH of the humic-containing wastewater is adjusted to 7 or less to insolubilize the humin and the time when the insoluble humin is removed from the wastewater. The pH of the humic-containing wastewater at this time is preferably 5 or more and 7 or less.
Examples of the aggregating agent include inorganic aggregating agents such as iron chloride, iron sulfate, aluminum sulfate and polyaluminum chloride; and polymer aggregating agents such as polyacrylamide and polyacrylic acid.

By the way, when the humin is coagulated and precipitated by the coagulant and removed from the wastewater as in the method (b) described above, there is a problem that the amount of the coagulated precipitate increases and the treatment cost increases. In addition, among the aggregating agents, the inorganic aggregating agents tend to form a complex with humin in the strongly acidic region and increase the solubility of humin, so that they tend not to be insolubilized.
However, in the present invention, the humin can be sufficiently removed without adding the coagulant, but the humin can be removed more efficiently by adding the coagulant. Moreover, since the amount of the coagulant added can be reduced as compared with the method (b) described above, the processing cost can be reduced. Further, particularly in a weakly acidic region where the pH of the humic-containing wastewater is 5 or more and 7 or less, it is difficult to form a complex with the inorganic coagulant and humic acid, and therefore, they can be effectively used together.

<Step (ii)>
The step (ii) is a membrane filtration step in which the humic acid-free wastewater obtained in the step (i) is subjected to membrane filtration.

As a form of membrane filtration, for example, a membrane module containing a filtration membrane for membrane filtration is fixed in a housing so that the primary side and the secondary side of the membrane are isolated from each other. The primary side may be connected to a reaction tank for insolubilizing heavy metals (eg, zinc and copper) in waste water through a circulation line, and the secondary side may be connected to a filtration pump.
Further, the membrane module containing the filtration membrane for membrane filtration may be a device capable of performing membrane filtration while being directly immersed in a reaction tank in which heavy metals (eg, zinc and copper) in wastewater are insolubilized. Further, as the membrane module, one provided with aeration means for cleaning the membrane surface below the filtration membrane may be used. As the aeration means, known means can be adopted, and examples thereof include an air diffuser.

In the step (ii), it is preferable to perform membrane filtration of the wastewater from which humic substances have been removed by the membrane separation activated sludge treatment that combines biological treatment and membrane separation treatment, because the wastewater can be purified more efficiently.
In particular, the biological treatment preferably includes at least one selected from the group consisting of anaerobic treatment, anoxic treatment and aerobic treatment, and more preferably includes anoxic treatment and aerobic treatment. If biological treatment includes anoxic treatment and aerobic treatment, it is possible to remove pollutants such as nitrogen and phosphorus in wastewater.
When the biological treatment includes anoxic treatment and aerobic treatment, it is preferable to return a part of the sludge in the aerobic tank for aerobic treatment to the anoxic tank for anoxic treatment.

The permeated water filtered by the filtration membrane may be further subjected to removal of water pollutants such as organic matter and nitrogen content, if necessary. Moreover, pH may be adjusted and it may be discharged into a river or the like.

<Processing device>
Here, an example of an apparatus for treating humic-containing wastewater used in the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an example of a treatment device for humic-containing wastewater. The humin-containing wastewater treatment device 1 of this example includes a treatment tank 11 and a membrane filtration device 20.

The processing tank 11 is a tank in which a insolubilizing tank for insolubilizing humin and a removing tank for removing insolubilized humin are integrated.
The treatment tank 11 is not particularly limited as long as it can store humic acid-containing wastewater and can remove insolubilized humic acid, but a humic acid-containing wastewater and a material that is less likely to be deteriorated by addition of an acid are preferable.

A drainage channel 12, a pH adjusting unit 13, a discharge channel 14, and a supernatant liquid channel 15 are connected to the treatment tank 11.
The drainage channel 12 is a channel for supplying the humic-containing wastewater to the treatment tank 11 from a raw water tank (not shown) that stores the humic-containing wastewater.
The pH adjusting means 13 adjusts the pH of the humic-containing wastewater in the treatment tank 11 to 7 or less by adding an acid to the treatment tank 11. The pH adjusting means 13 is not particularly limited as long as it can add an acid, and examples thereof include a pH meter and an acid adding device.
The discharge flow path 14 is a flow path for discharging the humin insolubilized by the addition of acid from the processing tank 11.
The supernatant liquid flow path 15 is a flow path for supplying the effluent-free waste water (supernatant liquid) to the membrane filtration device 20.

The membrane filtration device 20 is a device that membrane-filters the effluent-free wastewater.
In the membrane filtration device 20 of this example, wastewater from the treatment tank 11 (wastewater from which humic substances have been removed) is biologically treated by microorganisms in the activated sludge, and at the same time, the sludge and the permeated water are separated by a filtration membrane (separation membrane). Membrane separation activated sludge treatment for treatment (solid-liquid separation treatment) is performed.
The membrane filtration device 20 includes an aerobic tank 21 and a membrane module 22 including a filtration membrane.

The aerobic tank 21 is for treating effluent-free wastewater by the action of microorganisms in the activated sludge.
The aerobic tank 21 is not particularly limited as long as it can be biologically treated, but an aerobic tank 21 that is not easily deteriorated by an acid is preferable.

The membrane module 22 is arranged in the aerobic tank 21. In the membrane module 22, biologically treated wastewater is membrane-treated with a filtration membrane.
The membrane module 22 is connected to a permeate flow passage 23 that discharges permeate from the membrane filtration device 20, and a suction pump 24 is installed in the permeate flow passage 23. As a result, the permeated water that has permeated the filtration membrane of the membrane module 22 can be discharged from the membrane filtration device 20.

The filtration membrane is not particularly limited as long as it has filtration ability, and examples thereof include a hollow fiber membrane, a flat membrane, a tubular membrane, a monolith type membrane and the like. Among these, the hollow fiber membrane is preferable because it has a high volume filling rate.
When a hollow fiber membrane is used as the filtration membrane, examples of the material thereof include cellulose, polyolefin, polysulfone, polyvinylidene difluoride (PVDF), and polytetrafluoroethylene (PTFE). Among these, polyvinylidene difluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferable as the material of the hollow fiber membrane from the viewpoint of chemical resistance and resistance to pH change.
When a monolith type membrane is used as the filtration membrane, a ceramic membrane can be used.

The average pore size of the fine pores formed in the filtration membrane is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.45 μm. When the average pore size of the fine pores is at least the lower limit value, the pressure required for membrane filtration is easily reduced, and the concentration efficiency of metal aggregates is easily increased. When the average pore size of the fine pores is not more than the upper limit value, it is easy to prevent the metal aggregate from leaking into the filtrate.

The membrane filtration device 20 of this example further includes an air diffuser 25.
The air diffuser 25 is installed below the membrane module 22 in the aerobic tank 21.
An introduction pipe 26 that supplies air to the air diffusion pipe 25 is connected to the air diffusion pipe 25, and a blower 27 is installed in the introduction pipe 26.
The diffusing tube 25 is not particularly limited as long as it can discharge the air supplied from the blower 27 upward, and for example, a single tube with a hole or a membrane type tube can be used.

(Other embodiments)
The treatment device for humic-containing wastewater is not limited to the illustrated example. The membrane filtration device provided in the treatment device for humic-containing wastewater of the illustrated example is an integrated type that performs biological treatment and membrane separation treatment in one tank, but separate tanks for performing biological treatment and membrane separation treatment in separate tanks. It may be stationary.

When the biological treatment includes anoxic treatment and aerobic treatment, it is preferable to use, for example, the humin-containing wastewater treatment device 2 shown in FIG. 2 as the humin-containing wastewater treatment device. In FIG. 2, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
The membrane filtration device 20 shown in FIG. 2 includes an anoxic tank 31 upstream of the aerobic tank 21.
In the membrane filtration device 20 of this example, the wastewater from the treatment tank 11 (the wastewater from which the humic acid has been removed) is anoxic-treated in the anoxic tank 31, and then the aerobic tank 21 is subjected to aerobic treatment and membrane separation. Activated sludge treatment is performed.

In the anoxic tank 31, the anoxic treatment of biological treatment is performed.
The oxygen-free tank 31 is not particularly limited as long as the wastewater from the treatment tank 11 (wastewater from which the humic acid has been removed) can be subjected to oxygen-free treatment, but one that is not easily deteriorated by acid is preferable.
An oxygen-free treatment liquid channel 32 is connected to the oxygen-free tank 31. The oxygen-free treatment liquid flow path 32 is a flow path for supplying the oxygen-free treated waste water (oxygen-free treatment liquid) to the aerobic tank 21.
Further, the oxygen-free tank 31 is equipped with a stirring means 33 for stirring the inside of the tank.

In the aerobic tank 21, aerobic treatment of biological treatment is performed. Further, the biologically treated wastewater is subjected to membrane treatment by the filtration membrane provided in the membrane module 22 arranged in the aerobic tank 21.
A return flow passage 34 is connected to the aerobic tank 21 shown in FIG. The return flow passage 34 is a flow passage for returning a part of the activated sludge in the aerobic tank 21 to the anoxic tank 31.

When the biological treatment includes anaerobic treatment, for example, in the humin-containing wastewater treatment apparatus 2 shown in FIG. 2, an anaerobic tank (not shown) for performing the anaerobic treatment is installed upstream of the anoxic tank 31, An anaerobic tank may be installed instead of the oxygen tank 31.
The anaerobic tank is not particularly limited as long as it can anaerobically treat the wastewater from the treatment tank 11 (the wastewater from which the humic acid has been removed), but an anaerobic tank that is not easily deteriorated by acid is preferable.

When the above-mentioned step (i) includes the steps (i-1) to (i-3), the humic-containing wastewater treatment apparatus 3 shown in FIG. 3, for example, is used as the humic-containing wastewater treatment apparatus. Is preferred.
The treatment device 3 for humic-containing wastewater shown in FIG. 3 includes a treatment tank 11, a neutralization tank 41, and a membrane filtration device 20.
In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In the neutralization tank 41, wastewater from the treatment tank 11 (wastewater from which humic substances have been removed) is neutralized. In the treatment tank 11, the pH of the humic-containing wastewater is adjusted to less than 5, and the humic acid is insolubilized and then the humic acid is removed from the wastewater.
The neutralization tank 41 is not particularly limited as long as it can store the effluent-free effluent, but is preferably one that is not easily deteriorated by the addition of alkali.

The pH adjusting means 42 and the neutralizing liquid flow path 43 are connected to the neutralizing tank 41.
The pH adjusting means 42 adjusts the pH of the wastewater in the neutralization tank 41 from which humic substances have been removed to 5 to 9 by adding an alkali to the neutralization tank 41. The pH adjusting unit 42 is not particularly limited as long as it can add an alkali, and examples thereof include a unit equipped with a pH meter and an alkali adding device.
The neutralization liquid flow path 43 is a flow path for supplying the neutralized wastewater (neutralization liquid) to the membrane filtration device 20.

In addition, in the humic-containing wastewater treatment apparatus 3 shown in FIG. 3, the neutralization treatment and the membrane separation treatment are performed in separate tanks, but the neutralization tank 41 and the membrane filtration device 20 may be integrated. When the biological treatment includes the anoxic treatment and the aerobic treatment, the membrane filtration device 20 shown in FIG. 3 may include the anoxic tank 31 upstream of the aerobic tank 21 as shown in FIG. 2, for example. Good.

Further, in the humic-containing wastewater treatment devices 1 to 3 shown in FIGS. 1 to 3, an insolubilizing tank for insolubilizing humin and a removing tank for removing insolubilized humin are integrated, but as shown in FIG. 4, for example. In addition, insolubilization of humin and removal of insolubilized humin may be performed in separate tanks.
The treatment device 4 for humic-containing wastewater shown in FIG. 4 includes an insolubilization tank 51, a removal tank 52, and a membrane filtration device 20.
In FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In the insolubilizing tank 51, humin in the humic-containing wastewater supplied from a raw water tank (not shown) is insolubilized.
The insolubilizing tank 51 is not particularly limited as long as it can store the humic acid-containing wastewater, but is preferably one that is not easily deteriorated by the addition of the humic acid-containing wastewater and the acid.
To the insolubilizing tank 51, the drainage flow path 12, the pH adjusting means 13, and the insolubilizing water flow path 53 are connected. The insolubilized water flow path 53 is a flow path for supplying wastewater containing insolubilized humin to the removal tank 52.
Further, the insolubilizing tank 51 includes a stirring means 54 for stirring the inside of the tank.

In the removal tank 52, the insolubilized humin is removed from the wastewater from the insolubilized tank 51 (the wastewater containing the insolubilized humin).
The removal tank 52 is not particularly limited as long as it can store wastewater containing insolubilized humin and can remove insolubilized humin, but is preferably one that is not easily deteriorated by wastewater containing humin and acid.
The discharge channel 14 and the supernatant liquid channel 15 are connected to the removal tank 52.

Further, in the humin-containing wastewater treatment devices 1 to 4 shown in FIGS. 1 to 4, the pH of the humic-containing wastewater is adjusted in the treatment tank 11 or the insolubilization tank 51, but the pH is adjusted in the middle of the drainage flow path 12. Means 13 may be combined to adjust the pH of the humic-containing wastewater in the wastewater flow path 12.

<Effect>
INDUSTRIAL APPLICABILITY The present invention described above is a method and apparatus for insolubilizing and removing humic substances from wastewater containing humic substances and treating the wastewater by membrane filtration. As a result, humic acid can be removed from the humic acid-containing wastewater, and stable membrane filtration operation can be performed. Further, according to the present invention, it is possible to reduce the frequency of cleaning in the membrane filtration operation, and the frequency of stopping the processing associated with cleaning is low, which enables stable operation of the processing apparatus and reduces the amount of cleaning chemicals used. It is economical because it can.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following description.

[Example 1]
Using a membrane separation activated sludge test device equipped with a hollow fiber membrane module, a purification test of coal heated wastewater was conducted as follows.
As the coal heating waste water, the waste water generated by the coking process containing pH of 7.9 to 9.0, NH ₄ —N of 600 to 1000 mg/L, and COD _Cr of 2900 to 4400 mg/L was used.
Since drainage to facilitate the purification process, for the purpose of removing a portion of NH 4 _-N, while controlling the pH by adding a pre-sodium hydroxide 11 or more, subjected to aeration by the air, NH ₄ -N Was adjusted to 60 to 170 mg/L.
Thereafter, the pH was adjusted to 6.0 or more and 6.8 or less with hydrochloric acid, and the insolubilized humin was precipitated to obtain a supernatant (supernatant solution), thereby obtaining wastewater from which the insolubilized humin was removed (step (I)).
Using the wastewater from which the insolubilized humin was removed as raw water, purification treatment was performed under the condition that the average permeation flux per day of the hollow fiber membrane module was 0.05 to 0.07 m/d (step (ii)). ..
As a result, clogging of the hollow fiber membrane was suppressed, and it took about 30 days until the filtration pressure difference exceeded 10 kPa.

[Comparative Example 1]
Without the addition of hydrochloric acid, the pH of some waste water after the removal of the _NH 4 -N was adjusted to the same pH as before _NH 4 -N removal (pH7.8~9.1) except that, in Example Purification treatment was performed in the same manner as in 1.
As a result, clogging of the hollow fiber membrane was observed, and the filtration differential pressure increased to over 10 kPa in about 8 days.

From the above results, in Example 1 including the removal step (i), the clogging of the hollow fiber membrane was suppressed, and the wastewater treatment could be performed stably.
On the other hand, in Comparative Example 1 that did not include the step (i), the hollow fiber membrane was clogged, and stable wastewater treatment could not be performed.

1 Treatment device for humic-containing wastewater 2 Treatment device for humic-containing wastewater 3 Treatment device for humic-containing wastewater 4 Treatment device for humic-containing wastewater 11 Treatment tank 12 Drainage channel 13 pH adjusting means 14 Discharge channel 15 Supernatant channel 20 Membrane Filtration device 21 Aerobic tank 22 Membrane module 23 Permeate flow passage 24 Suction pump 25 Diffuser pipe 26 Introducing pipe 27 Blower 31 Anoxic tank 32 Oxygen-free treatment liquid passage 33 Stirring means 34 Return passage 41 Neutralization tank 42 pH adjusting means 43 Neutralizing Liquid Flow Path 51 Insolubilizing Tank 52 Removal Tank 53 Insolubilizing Water Flow Path 54 Stirring Means

Claims (15)

The following steps (i) and (ii) are carried out, and removal of insolubilized humin is carried out by at least one selected from the group consisting of sand filtration, pressure flotation, centrifugation, belt press, and sedimentation by a sedimentation basin. Done,
In the following step (i), a method for treating humic-containing wastewater in which no coagulant is added.
(I) a step including the following steps (i-1) to (i-3) :
(I-1) Insolubilization step of adjusting the pH of the humic-containing wastewater to less than 5 to insolubilize the humin in the wastewater;
(I-2) A removal step of removing insolubilized humin from the wastewater obtained in the step (i-1);
(I-3) A neutralizing step of adding an alkali to the wastewater obtained in the step (i-2) to adjust the pH to 5 to 9 and neutralizing the wastewater;
(Ii) A membrane filtration step in which the humic acid- removed and neutralized waste water obtained in the step (i) is subjected to membrane filtration. The method for treating humic acid-containing wastewater according to claim 1, wherein in the step (i), at least one of an inorganic acid and an organic acid is added to adjust the pH of the humic acid-containing wastewater to insolubilize the humic acid. The method for treating humic acid-containing wastewater according to claim 1 or 2 , wherein in the step (i), hydrochloric acid is added to adjust the pH of the humic acid-containing wastewater to insolubilize the humic acid. The method for treating humic-containing wastewater according to any one of claims 1 to 5 , wherein the step (ii) is a membrane separation activated sludge treatment in which a biological treatment and a membrane separation treatment are combined. The method for treating humic-containing wastewater according to claim 4 , wherein the biological treatment includes at least one selected from the group consisting of anaerobic treatment, anoxic treatment and aerobic treatment. The method for treating humic-containing wastewater according to claim 4 or 5 , wherein the biological treatment includes anoxic treatment and aerobic treatment. The method for treating humic-containing wastewater according to claim 6 , wherein a part of the sludge in the aerobic tank that performs aerobic treatment is returned to the anoxic tank that performs anoxic treatment in the biological treatment. The humic-containing wastewater, wastewater generated from the process a portion of the coal comprises a heat treatment of gasification, or waste water containing human waste discharged from the livestock industry, as claimed in any one of claims 1-7 Treatment method of wastewater containing humin. An insolubilization tank for insolubilizing humin, a removal tank for removing insolubilized humin, a neutralization tank for neutralizing effluent- free wastewater, and a membrane filtration device for removing humin and neutralizing wastewater by membrane filtration, A treatment device for humic-containing wastewater,
The insolubilizing tank has a pH adjusting means for adjusting the pH in the tank to less than 5 by adding an acid,
The neutralization tank has a pH adjusting means for adjusting the pH in the tank to 5 to 9 by adding an alkali,
The removal tank includes at least one selected from the group consisting of a sand filtration device, a pressure flotation device, a centrifugal separation device, a belt press device, and a sedimentation tank,
A treatment device for humic-containing wastewater, wherein the insolubilization tank is not equipped with a coagulant addition means. The treatment device for humic-containing wastewater according to claim 9 , wherein the neutralization tank and the membrane filtration device are integrated. The treatment device for humic-containing wastewater according to claim 9 or 10 , wherein the insolubilization tank and the removal tank are integrated. The treatment device for humic-containing wastewater according to any one of claims 9 to 11 , wherein in the membrane filtration device, a membrane separation activated sludge treatment combining biological treatment and membrane separation treatment is performed. The treatment apparatus for humic-containing wastewater according to claim 12 , wherein the biological treatment includes one or more selected from the group consisting of anaerobic treatment, anoxic treatment and aerobic treatment. The humic-containing wastewater treatment apparatus according to claim 12 or 13 , wherein the biological treatment includes anoxic treatment and aerobic treatment. The treatment device for humic-containing wastewater according to claim 14 , wherein a part of the sludge in the aerobic tank that performs aerobic treatment is returned to the anoxic tank that performs anoxic treatment in the biological treatment.

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