JP4860201B2 - Method and apparatus for treating wastewater containing boron - Google Patents

Description

  The present invention relates to the treatment of boron-containing wastewater such as flue gas desulfurization wastewater from coal-fired power plants, waste incineration smoke washing wastewater, nickel plating factory wastewater, glass manufacturing factory wastewater, and more specifically, aluminum compounds and calcium compounds. It is related with the processing method and processing apparatus of the boron containing waste water which adjusts to alkalinity and performs solid-liquid separation.

  Conventionally, as an agglomeration and precipitation treatment for boron-containing wastewater, an aluminum compound such as aluminum sulfate and a calcium compound such as slaked lime are added to the boron-containing wastewater and reacted with an alkaline solution having a pH of 9 or more to separate the resulting reaction solution from insoluble precipitates. And processing methods are known.

When an aluminum compound is dissolved in water and adjusted to be alkaline, it dissolves in the state of aluminate ions. Aluminate ions easily react with calcium and produce white insoluble precipitates. Although few studies have been made on this precipitate, it is considered to be calcium aluminate Ca (Al (OH) ₄ ) ₂ .
Therefore, boron is considered to be removed by adsorption or incorporation into crystals when aluminum and calcium react under alkaline conditions to produce an insoluble precipitate presumed to be calcium aluminate. Yes.

  In the coagulation precipitation method using an aluminum compound and a calcium compound, it is necessary to use a relatively large amount of chemicals in order to treat boron to 10 mg / l or less of the wastewater standard, and the insolubility is about 100 times that of boron by weight ratio. It is necessary to generate precipitates. That is, since the amount of chemicals is large and the amount of sludge generated is also large, development of a more efficient treatment method is desired.

As a method for solving these problems, Patent Documents 1 and 2 disclose a solid sludge obtained by solid-liquid separation of an insoluble precipitate produced by adding an aluminum compound and a calcium compound into a boron-containing wastewater in a precipitation tank or the like. A method of returning the part to the reaction process has been proposed. Patent Document 3 proposes a method in which an insoluble precipitate formed by adding an aluminum compound and a calcium compound to boron-containing wastewater is solid-liquid separated in a precipitation tank or the like, and the separated precipitate is returned to contact with raw water. Has been. Furthermore, Patent Document 4 proposes a method in which an aluminum compound and a sulfuric acid compound are present in boron-containing water.
JP 2001-232372 A JP 2001-239273 A JP 2002-233881 A JP 2001-162287 A

  By the way, the above-mentioned prior art is a method of treating boron-containing wastewater by adding an aluminum compound and a calcium compound to wastewater containing boron. The methods described in Patent Documents 1 to 3, the so-called sludge circulation method, have the effect of promoting the growth of crystals using the returned sludge as the core, and the effect of improving the sedimentation property (sediment separation property) of the sludge. This method is widely used in wastewater treatment of inorganic chemical substances. However, as a result of repeated investigations by the inventors on the sludge circulation method, it was found that the treatment performance was improved at the initial stage of return for boron wastewater treatment, but the treatment performance deteriorated with each return. It was. In other words, there is a problem that the above method cannot maintain long-term and stable processability. Further, the method described in Patent Document 4 and the precipitation separation method of boron-containing raw water also have a problem that long-term and stable processability cannot be maintained.

  Therefore, in order to solve such problems, the present invention can efficiently maintain a long-term and stable good treatability with a smaller amount of chemicals, and can efficiently treat boron-containing wastewater with less sludge generation. To provide an apparatus.

The invention according to claim 1 is introduced from the first step, a first step of generating a reaction solution and an insoluble precipitate by adding an aluminum compound and a calcium compound to waste water containing boron and adjusting the pH to 9 or more. A second step of adding a polymer flocculant to the reaction solution and separating it into treated water and sludge, and a polymer added in the second step to a part of the sludge introduced from the second step And a third step of adding and mixing an ionic polymer flocculant different from the flocculant and then returning to the first step.

According to the first aspect of the invention, the compound added to the waste water containing boron in a first step to produce a reaction solution and an insoluble precipitate was adjusted to pH9 or more, introduced from the first step in the second step In the third step, an ionic polymer flocculant different from the polymer flocculant is added to a part of the sludge in the second step. In addition, after mixing and returning to the first step, the compound and polymer flocculant circulate from the third step to the first step, so that long-term and stable good processability can be maintained with fewer drugs. In addition, it is possible to realize an efficient treatment of boron-containing wastewater that generates less sludge.

The invention according to claim 2 is introduced from the first step, a first step of generating a reaction solution and an insoluble precipitate by adding an aluminum compound and a calcium compound to waste water containing boron and adjusting the pH to 9 or more. A second step of adding a polymer flocculant to the reaction solution and separating it into treated water and sludge; after irradiating a part of the sludge introduced from the second step with ultrasonic waves, And a third step of returning to the step.

According to the invention described in claim 2 , a compound is added to the wastewater containing boron in the first step to adjust the pH to 9 or more to produce a reaction solution and an insoluble precipitate, and introduced from the first step in the second step. A polymer flocculant is added to the reaction solution, which is separated into treated water and sludge, and ultrasonic waves are applied to a portion of the sludge introduced from the second step in the third step, and then returned to the first step. Since the chemical circulates from the third step to the first step, efficient boron-containing wastewater that can maintain long-term and stable good treatment with fewer chemicals and generates less sludge. Can be realized.

The invention according to claim 3 is the first step of adding a part of the reaction solution returned from the second step to the wastewater containing boron and stirring and mixing the aluminum, and the reaction solution introduced from the first step is made of aluminum. A second step of adding a compound and a calcium compound to adjust the pH to 9 or more to produce a reaction solution and an insoluble precipitate, and returning a part of the reaction solution to the first step; And a third step of solid-liquid separation into treated water and sludge.

According to the invention of claim 3, a part of the reaction solution is added to and mixed with the wastewater containing boron in the first step, and the compound is added to the reaction solution introduced from the first step in the second step to be alkaline. To produce a reaction solution and an insoluble precipitate, and by adding a polymer flocculant to the reaction solution introduced from the second step in the third step and solid-liquid separation, the compound is obtained from the second step. Since it circulates in one step, it is possible to maintain an excellent treatment property in a long term and stably with a smaller amount of chemicals, and to realize an efficient treatment of boron-containing wastewater with less sludge generation.

The invention according to claim 4 is provided with an adjusting means for adjusting the pH to 9 or more by adding wastewater containing boron and adding an aluminum compound and a calcium compound, and the adjusting means generates a reaction solution and an insoluble precipitate. A reaction tank; a coagulation tank provided with a first addition means for adding a polymer flocculant to the reaction liquid introduced from the reaction tank; and the reaction liquid is introduced from the coagulation tank to treat water and sludge. A settling tank for separation and a second addition means for adding a part of the sludge from the settling tank and adding an ionic polymer flocculant different from the polymer flocculant added in the flocculant to the sludge are provided. And a mixing means for mixing the reaction liquid, and a flocculant addition tank for returning the mixed reaction liquid to the reaction tank.

According to invention of Claim 4 , a compound is added to the wastewater containing boron in a reaction tank, it adjusts to pH9 or more, a reaction liquid and an insoluble precipitate are produced | generated, and the reaction liquid from a reaction tank is made into a coagulation tank. Add polymer flocculant, separate into treated water and sludge in sedimentation tank, add ionic polymer flocculant different from the polymer flocculant to part of sludge from sedimentation tank in flocculant addition tank By mixing the reaction liquid and returning the mixed reaction liquid to the reaction tank, the drug circulates from the flocculant addition tank to the reaction tank, so that long-term and stable good processability can be achieved with fewer drugs. An efficient treatment of boron-containing wastewater that can be maintained and generates little sludge can be realized.

According to the fifth aspect of the present invention, a wastewater containing boron is introduced, an adjusting means for adjusting the pH to 9 or more by adding an aluminum compound and a calcium compound is provided, and the adjusting means generates a reaction solution and an insoluble precipitate. A reaction tank; a coagulation tank provided with an addition means for adding a polymer flocculant to the reaction liquid introduced from the reaction tank; and a precipitate into which the reaction liquid is introduced from the coagulation tank and separated into treated water and sludge. A part of the sludge is introduced from the tank and the settling tank, and an ultrasonic oscillator for irradiating the sludge with ultrasonic waves is provided, and the reaction liquid irradiated with ultrasonic waves by the ultrasonic oscillator is returned to the reaction tank. And an ultrasonic irradiation tank.

According to the fifth aspect of the present invention, a wastewater containing boron is introduced, an adjusting means for adjusting the pH to 9 or more by adding an aluminum compound and a calcium compound is provided, and the adjusting means generates a reaction solution and an insoluble precipitate. A reaction tank; a coagulation tank provided with an addition means for adding a polymer flocculant to the reaction liquid introduced from the reaction tank; and a precipitate into which the reaction liquid is introduced from the coagulation tank and separated into treated water and sludge. A part of the sludge is introduced from the tank and the settling tank, and an ultrasonic oscillator for irradiating the sludge with ultrasonic waves is provided, and the reaction liquid irradiated with ultrasonic waves by the ultrasonic oscillator is returned to the reaction tank. And an ultrasonic irradiation tank.

The invention according to claim 6 is the first reaction tank provided with mixing means for adding and mixing a part of the reaction liquid returned from the second reaction tank while introducing wastewater containing boron, and the first reaction tank. A second reaction tank provided with adjusting means for adding an aluminum compound and a calcium compound to a reaction liquid introduced from one reaction tank to adjust the pH to 9 or more to generate a reaction liquid and an insoluble precipitate; and the second reaction A coagulation tank in which the reaction liquid is introduced from the tank and provided with an addition means for adding a polymer flocculant; a precipitation tank in which the reaction liquid is introduced from the coagulation tank and separated into treated water and sludge;
It is characterized by including.

According to the invention described in claim 6, wastewater containing boron is introduced into the first reaction tank and a part of the reaction solution returned from the second reaction tank is added and mixed. A compound is added to the reaction liquid introduced from one reaction tank to adjust the alkalinity to pH 9 or higher to produce a reaction liquid and an insoluble precipitate, and the reaction liquid is introduced from the second reaction tank to the polymer agglomeration in the aggregation tank. The agent is added and separated into treated water and sludge in the sedimentation tank, so that the chemical circulates from the second reaction tank to the first reaction tank. An efficient treatment of boron-containing wastewater that can be maintained and generates little sludge can be realized.

  According to the present invention, waste water containing boron and a compound are added in the first step to generate a reaction solution and an insoluble precipitate, and a flocculant is added to the reaction solution in the first step in the second step, and treated water and After separating into sludge and adding a flocculant different from the flocculant to a part of the sludge introduced from the second step in the third step, the mixture is returned to the first step, whereby the drug is transferred to the third step. Since it is circulated from the process to the first process, it is possible to maintain a good long-term and stable treatment with fewer chemicals, and to achieve efficient treatment of boron-containing wastewater with less sludge generation. it can.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is an equipment configuration diagram showing an embodiment of a treatment apparatus to which a treatment method for boron-containing wastewater according to the present invention is applied.
The treatment apparatus 100 shown in the figure is provided with adjusting means 105 for introducing waste water containing boron, adjusting the pH to 9 or more by adding an aluminum compound and a calcium compound, and generating a reaction solution and an insoluble precipitate. A reaction tank 101 for generating a reaction solution and an insoluble precipitate by means 105; a coagulation tank 102 provided with a first addition means 106 for adding a polymer flocculant to the reaction liquid in the reaction tank 101; The reaction liquid is introduced, a precipitation tank 103 that separates (solid-liquid separation) into treated water and sludge, and a part of the sludge separated in the precipitation tank 103 is introduced, and added to the introduced sludge in the coagulation tank 102. A second addition means 107 for adding an ionic polymer flocculant different from the polymer flocculant is provided, a mixing means 108 for mixing the reaction liquid is provided, and the mixed reaction liquid is not shown. Including a flocculant tank 104 for returning to the reaction tank 101 by pump, a.

The adjusting means 105 includes, for example, a tank for storing an aluminum compound, a tank for storing a calcium compound, a tank for storing a pH adjusting agent, a pipe leading from each tank to the reaction tank 101, an electromagnetic valve inserted into each pipe, and each electromagnetic valve. It is comprised with the drive device which operates a valve (all are not shown in figure).
The first addition means 106 includes, for example, a tank that stores the polymer flocculant, a pipe that leads from the tank to the flocculation tank 102, an electromagnetic valve that is inserted into the pipe, and a drive device that operates the electromagnetic valve (all of which are Not shown).
As the second addition means 107, for example, a tank for storing an ionic polymer flocculant different from the polymer flocculant described above, a pipe leading from the tank to the flocculant addition tank 104, an electromagnetic valve inserted in the pipe, It is comprised with the drive device which operates a solenoid valve (all are not shown in figure).
Examples of the mixing means 108 include a screw and a means for rotating the screw to mix the reaction liquid by stirring the reaction liquid. For example, a porous block (for example, bubble stone), a pipe having one end fixed to the porous block, A means that comprises a pump that pumps air from the other end of the pipe and mixes by blowing bubbles into the reaction solution may be used.

In the processing apparatus 100 shown in FIG. 1, boron-containing wastewater is first introduced into a reaction vessel 101 in which a first step is performed.
In the first step, a calcium compound and an aluminum compound are added to the boron-containing waste water to adjust the pH to 9 or higher to produce a reaction solution and an insoluble precipitate, which are mixed by the mixing means 108. The sludge returned from the flocculant addition tank 104 to be applied is received. In the first step, an insoluble precipitate containing calcium aluminate is generated, and a reaction occurs in which boron is adsorbed or taken into the crystal in the precipitate.

  Next, in the agglomeration tank 102 in which the first half of the second step is performed, a polymer flocculant is added to the reaction liquid in the agglomeration tank 102 from the first addition means 106 and mixed to agglomerate insoluble precipitates. The agglomerated particles come to have sedimentation properties, and are allowed to stand in the sedimentation tank 103 in which the second half of the second step is performed, thereby precipitating insoluble precipitates and obtaining supernatant water (treated water).

  In the flocculant addition tank 104 subjected to the third step, the polymer flocculant is added and mixed by the second addition means 107 to a part of the precipitate separated in the second step. The ionicity of the polymer flocculant added here is different from that of the polymer flocculant added in the second step. For example, when a nonionic polymer flocculant is added in the second step, a cationic or anionic polymer flocculant is added in the third step. By adding different ionic polymer flocculants in this way, boron can be treated in a long-term and stable manner even if sludge is returned to the first step.

FIG. 2 is an equipment configuration diagram showing another embodiment of a treatment apparatus to which the method for treating boron-containing wastewater according to the present invention is applied. Hereinafter, the same reference numerals are used for members similar to those shown in FIG.
The difference between the processing apparatus 200 shown in FIG. 2 and the processing apparatus 100 shown in FIG. 1 is that an ultrasonic irradiation tank 201 is used instead of using the flocculant addition tank 104.

  The treatment apparatus 200 shown in FIG. 2 is provided with an adjusting unit 105 into which wastewater containing boron is introduced and an aluminum compound and a calcium compound are added to adjust the pH to 9 or higher. Reaction tank 101, a coagulation tank 102 provided with an addition means (similar to the first addition means) 106 for adding a polymer flocculant to the reaction liquid in the reaction tank 101, and a reaction liquid from the coagulation tank 102 Is introduced into the treated water and sludge, a part of the sludge separated in the sedimentation tank 103 is introduced, and an ultrasonic oscillator 202 for irradiating the introduced sludge with ultrasonic waves is provided, And an ultrasonic irradiation tank 201 for returning the reaction liquid irradiated with ultrasonic waves by the ultrasonic oscillator 202 to the reaction tank 101 with a pump (not shown).

In the processing apparatus 200 shown in FIG. 2, boron-containing wastewater is first introduced into the reaction tank 101 in which the first step is performed. In the first step, a calcium compound and an aluminum compound are added to the boron-containing wastewater to adjust the alkalinity to pH 9 or higher to produce a reaction solution and an insoluble precipitate, and an ultrasonic wave is irradiated from the ultrasonic transmitter 202. At the same time, the sludge returned from the ultrasonic irradiation tank 201 subjected to the third step is received.
In the first step, a reaction solution and an insoluble precipitate containing calcium aluminate are generated, and a reaction occurs in which boron is adsorbed or taken into the crystal in the precipitate.

  Next, in the agglomeration tank 102 in which the first half of the second step is performed, the polymer flocculant is added from the addition means 106 to the reaction solution in the agglomeration tank 102 and mixed to agglomerate insoluble precipitates. The agglomerated particles come to have sedimentation properties, and are allowed to stand in the sedimentation tank 103 in which the second half of the second step is performed, thereby precipitating insoluble precipitates and obtaining supernatant water (treated water).

  In the ultrasonic irradiation tank 201 to which the third step is performed, ultrasonic waves are irradiated by the ultrasonic transmitter 202 onto a part of the precipitate separated in the second step. When the ultrasonic wave is irradiated, the aggregated insoluble precipitate is refined. The insoluble precipitate is refined and mixed with the reaction solution evenly. Boron can be treated in a long-term and stable manner by returning the sludge refined by irradiating ultrasonic waves to the reaction tank 101 in which the first step is performed.

FIG. 3 is an equipment configuration diagram showing another embodiment of a treatment apparatus to which the method for treating boron-containing wastewater according to the present invention is applied.
The difference between the processing apparatus 300 shown in FIG. 3 and the processing apparatus 100 shown in FIG. 1 is that the tank liquid in the second reaction tank 101-2 subjected to the second process is subjected to the first process. It is a point to circulate to the reaction tank 101-1.

  The processing apparatus 300 shown in FIG. 3 is a first reaction tank in which waste water containing boron is introduced and a mixing means 301 is provided for adding and mixing a part of the reaction liquid from the second reaction tank 101-2. 101-1, a second reaction tank 101-2 provided with an adjusting means 105 for adjusting the pH to 9 or higher by adding an aluminum compound and a calcium compound to the reaction solution from the first reaction tank 101-1, and a second reaction tank The reaction liquid from 101-2 is introduced, the coagulation tank 102 provided with the addition means 106 for adding the polymer flocculant, and the reaction liquid from the coagulation tank 102 is introduced to solid-liquid separation into treated water and sludge And a sedimentation tank 103.

In the processing apparatus 300 shown in FIG. 3, the boron-containing waste water is first introduced into the first reaction tank 101-1. In the first step, a part of the reaction liquid that has passed through the second reaction tank 101-2 subjected to the second step and the boron-containing wastewater are stirred and mixed by the mixing means 301.
In the second reaction tank 101-2, the calcium compound and the aluminum compound are added to the boron-containing wastewater by the adding means 105 to adjust the alkalinity to pH 9 or higher and mix.
In the second step, a reaction solution and an insoluble precipitate containing calcium aluminate are generated, and a reaction occurs in which boron is adsorbed or taken into the crystal in the precipitate.
The reaction solution that has passed through the second step is precipitated in the agglomeration tank 102 in which the first half of the third step is applied and the precipitation tank 103 in which the second half of the third step is applied to obtain supernatant water (treated water). The reaction liquid returned to the reaction tank 101-2 is distributed, but the reaction liquid returned to the first reaction tank 101-2 is not returned after the insoluble precipitate is concentrated, but is returned as it is. . Thus, by returning in the state of the reaction solution, boron can be treated for a long time and stably.

  Each step other than the solid-liquid separation step in the treatment apparatus to which the treatment method according to the present invention is applied preferably uses a mixing operation because it is necessary to adjust the pH and to uniformly mix the additive agent and the returned sludge. It is possible to adopt a method of mixing by installing a stirrer in the tank, a mixing method using a line mixer, or an aeration mixing method using an air lift effect such as air.

  The solid-liquid separation apparatus used in the treatment apparatus to which the treatment method according to the present invention is applied can use any apparatus used for general wastewater treatment without limitation, and in addition to the precipitation separation apparatus, such as a filter press and a belt press. A filtration dehydration device, a membrane separation device, or the like can be used.

  The type of aluminum compound in the treatment apparatus to which the treatment method according to the present invention is applied is not particularly limited, and aluminum sulfate (sulfate band), polyaluminum chloride (PAC), aluminum chloride, aluminum hydroxide, sodium aluminate (sodium aluminate) ) And the like, but a sulfate band capable of simultaneously supplying sulfate ions is preferred.

  There is no restriction | limiting in particular in the kind of calcium compound in the processing apparatus to which the processing method concerning this invention is applied, You may mix and use 2 or more types. Examples of calcium compounds that can be used include calcium hydroxide (slaked lime), calcium chloride, calcium oxide (quick lime), calcium carbonate, calcium sulfate, and the like, but easily react with aluminum and sulfate ions to form insoluble precipitates. In addition, inexpensive calcium hydroxide is preferable.

  According to the present invention, a drug for pH adjustment can be used in all steps. In the present invention, since the step of adjusting the alkalinity to pH 9 or more occupies the main component, for example, when an alkaline agent such as slaked lime or quicklime is used as the calcium compound, the pH adjuster can be used for both calcium supply and pH adjustment. It may not be necessary. However, when the acidity of the boron-containing wastewater is strong, an alkali agent such as sodium hydroxide or potassium hydroxide may be used in combination. Moreover, when it is necessary to add an acid, such as when the boron-containing wastewater is a strong alkali, an acid such as hydrochloric acid, nitric acid, or sulfuric acid can be added.

  The reaction time, reaction temperature, and reaction pressure conditions in the treatment method according to the present invention can be arbitrarily set in all steps. The longer the reaction time is, the better. However, if the reaction time is too long, the scale of equipment is increased, and therefore, 10 minutes to 1 hour is preferable, and more preferably about 30 minutes. is there. The reaction temperature can be applied in a wide range of 0 ° C. to 100 ° C. under normal pressure, but can also be applied at a higher temperature under high pressure conditions.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. In Examples and Comparative Examples, an industrial sulfuric acid band (8% by weight in terms of Al ₂ O ₃ ) was used as the aluminum compound, and slaked lime (reagent special grade) was used as the calcium compound, and pure water was added to adjust to 10% by weight. Used after milk condition. The amount of drug added (mg / l) represents the amount added relative to the amount of raw water.

(Comparative Example 1)
An experiment was conducted in which boric acid was dissolved in pure water, and 100 ml of simulated waste water adjusted to a boron concentration of 100 mg / l was used to treat the sludge by a known method. The simulated wastewater was added with a sulfuric acid band of 500 mg / l as aluminum and slaked lime as calcium at 4000 mg / l and stirred for 1 hour. The pH rose to about 12. Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates to obtain clear supernatant water (treated water). At the same time, the precipitate was separated. The volume of the precipitate was 25 ml.

Next, the first return experiment was performed. 25 ml of the above precipitate was taken out and added to a simulated waste water adjusted to a boron concentration of 100 mg / l. At the same time, a sulfuric acid band was added to 500 mg / l as aluminum and slaked lime was set to 4000 mg / l as calcium, followed by stirring for 1 hour. The pH rose to about 12.
Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates. As obtained, the precipitate separated. The volume of the precipitate was 37 ml.

The experiment was repeated up to 5 times of return in the same manner as described above. The sludge to be returned was fixed at 25 ml (25% by volume of the raw water), and the rest was discharged out of the system as surplus sludge. The results are shown in Table 1.

  According to Table 1, the boron concentration in the treated water without sludge return is 38 mg / l, whereas the boron concentration is 1.5 mg / l in the first return, and the treatment efficiency improvement effect by returning is recognized. , It can be seen that the processability deteriorates every time the return number is repeated.

Example 1
A beaker experiment based on the continuous processing apparatus of FIG. 1 was conducted. That is, boric acid was dissolved in pure water and added to 100 ml of simulated waste water adjusted to a boron concentration of 100 mg / l so that the sulfuric acid band was 500 mg / l as aluminum and slaked lime was calcium as 4000 mg / l, and stirred for 1 hour. As a result, the pH rose to about 12.
Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates to obtain clear supernatant water (treated water). At the same time, the precipitate was separated. The volume of the precipitate was 25 ml.

Next, the first return experiment was performed. 25 ml of the above-mentioned precipitate was taken out, 15 mg / l of a polymer flocculant (anionic polymer flocculant manufactured by Health Flock, product number A-151) was added to the precipitate, and the mixture was stirred for 10 minutes.
Subsequently, at the same time as adding to the simulated waste water adjusted to a boron concentration of 100 mg / l, a sulfuric acid band was added to 500 mg / l as aluminum, and slaked lime was set to 4000 mg / l as calcium, followed by stirring for 1 hour. As a result, the pH increased to about 12.
Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates. As obtained, the precipitate separated.

The experiment was repeated up to 7 times of return in the same manner as described above. The sludge to be returned was fixed at 25 ml (25% by volume of the raw water), and the rest was discharged out of the system as surplus sludge.
FIG. 4 shows the relationship between the sludge return count and the treated water boron concentration when treated by the conventional sludge return method shown in Comparative Example 1, and the sludge return count and treated water boron concentration corresponding to Examples 1 to 3 described later. It is a figure which shows the relationship.
In the figure, the horizontal axis indicates the number of times, and the vertical axis indicates the treated water boron concentration.

  According to FIG. 4, it can be recognized that boron can be treated in a long-term and stable manner regardless of the number of returns by treating with the method of FIG. 1.

(Example 2)
A beaker experiment based on the continuous processing apparatus of FIG. 2 was conducted. That is, boric acid was dissolved in pure water and added to 100 ml of simulated waste water adjusted to a boron concentration of 100 mg / l so that the sulfuric acid band was 500 mg / l as aluminum and slaked lime was calcium as 4000 mg / l, and stirred for 1 hour. The pH rose to about 12. Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates to obtain clear supernatant water (treated water). At the same time, the precipitate was separated. The volume of the precipitate was 25 ml.

Next, the first return experiment was performed. 25 ml of the above precipitate was taken out and irradiated with ultrasonic waves for 10 minutes in a tabletop ultrasonic cleaner (output 300 W, frequency 38 kHz). The sludge after ultrasonic irradiation was added to a simulated waste water adjusted to a boron concentration of 100 mg / l. At the same time, a sulfuric acid band was added to 500 mg / l as aluminum and slaked lime was set to 4000 mg / l as calcium, followed by stirring for 1 hour. As a result, the pH increased to about 12.
Thereafter, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added, and the mixture was gently stirred to aggregate insoluble precipitates. As obtained, the precipitate separated.

  The experiment was repeated up to 7 times of return in the same manner as described above. The sludge to be returned was fixed at 25 ml (25% by volume of the raw water), and the rest was discharged out of the system as surplus sludge. The result of the treated water boron concentration is shown in FIG.

  According to FIG. 4, it is recognized that boron can be treated in a long-term and stable manner regardless of the number of returns by treating with the method of FIG. 2.

(Example 3)
A beaker experiment based on the continuous processing apparatus of FIG. 3 was conducted. That is, boric acid was dissolved in pure water and added to 100 ml of simulated waste water adjusted to a boron concentration of 100 mg / l so that the sulfuric acid band was 500 mg / l as aluminum and slaked lime was calcium as 4000 mg / l, and stirred for 1 hour. As a result, the pH increased to about 12.

  Next, 15 mg / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) was added to 100 ml of 200 ml of the reaction solution, and the mixture was gently stirred to clump insoluble precipitates. Supernatant water (treated water) was obtained, and the precipitate was separated.

Next, the first return experiment was performed. The remaining 100 ml of the reaction solution was added to 100 ml of simulated waste water adjusted to a boron concentration of 100 mg / l and stirred for 1 hour.
Then, the sulfuric acid band was added to 500 mg / l as aluminum, and slaked lime was set to 4000 mg / l as calcium, followed by stirring for 1 hour. The pH rose to about 12. 15 ml / l of a polymer flocculant (nonionic polymer flocculant manufactured by Health Flock Co., Ltd., product number N-217) is added to 100 ml out of 200 ml of the reaction solution, and gently stirred to agglomerate insoluble precipitates. (Treated water) was obtained and the precipitate was separated.

  The experiment was repeated up to 7 times of return in the same manner as described above. The reaction solution to be returned was fixed at 100 ml (100% by volume of the raw water). The result of the treated water boron concentration is shown in FIG.

  According to FIG. 4, it is recognized that boron can be treated stably over a long period of time regardless of the number of returns by performing the treatment with the continuous treatment apparatus of FIG. 3.

  In the above, according to the treatment method and apparatus for boron-containing wastewater according to the present invention, there is an advantage that good treatment can be maintained stably and stably for a long time with fewer chemicals.

It is the equipment block diagram which showed one Embodiment of the processing apparatus to which the processing method of the boron containing waste water which concerns on this invention was applied. It is the equipment block diagram which showed other embodiment of the processing apparatus to which the processing method of the boron containing wastewater which concerns on this invention was applied. It is the equipment block diagram which showed other embodiment of the processing apparatus to which the processing method of the boron containing wastewater which concerns on this invention was applied. The relationship between the sludge return count and the treated water boron concentration when treated by the conventional sludge return method shown in Comparative Example 1, the relationship between the sludge return count and the treated water boron concentration corresponding to Examples 1 to 3 described later. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Processing apparatus 101 Reaction tank 102 Coagulation tank 103 Precipitation tank 104 Coagulant addition tank

Claims (6)

A first step of adding an aluminum compound and a calcium compound to wastewater containing boron and adjusting the pH to 9 or more to produce a reaction solution and an insoluble precipitate;
A second step of adding a polymer flocculant to the reaction liquid introduced from the first step and separating it into treated water and sludge;
An ionic polymer flocculant different from the polymer flocculant added in the second step is added to and mixed with a part of the sludge introduced from the second step, and then returned to the first step. The third step;
A method for treating wastewater containing boron, comprising: A first step of adding an aluminum compound and a calcium compound to wastewater containing boron and adjusting the pH to 9 or more to produce a reaction solution and an insoluble precipitate;
A second step of adding a polymer flocculant to the reaction liquid introduced from the first step, and separating into treated water and sludge;
After irradiating a part of the sludge introduced from the second step with ultrasonic waves, a third step returning to the first step;
A method for treating wastewater containing boron, comprising: A first step of adding a part of the reaction liquid returned from the second step to the wastewater containing boron and stirring and mixing;
An aluminum compound and a calcium compound are added to the reaction solution introduced from the first step to adjust the pH to 9 or more to produce a reaction solution and an insoluble precipitate, and a part of the reaction solution is returned to the first step. The second step;
A third step of adding a polymer flocculant to the reaction liquid introduced from the second step and separating the liquid into treated water and sludge;
A method for treating wastewater containing boron, comprising: A wastewater containing boron is introduced, and an adjusting means for adjusting the pH to 9 or more by adding an aluminum compound and a calcium compound is provided, and a reaction vessel for generating a reaction liquid and an insoluble precipitate by the adjusting means,
A coagulation tank provided with a first addition means for adding a polymer flocculant to the reaction liquid introduced from the reaction tank;
A settling tank in which the reaction solution is introduced from the coagulation tank and separated into treated water and sludge;
A part of the sludge is introduced from the settling tank, and a second addition means is provided for adding an ionic polymer flocculant different from the polymer flocculant added in the flocculent to the sludge and mixing the reaction liquid And a flocculant addition tank for returning the mixed reaction liquid to the reaction tank,
An apparatus for treating boron-containing wastewater, comprising: A wastewater containing boron is introduced, and an adjusting means for adjusting the pH to 9 or more by adding an aluminum compound and a calcium compound is provided, and a reaction vessel for generating a reaction liquid and an insoluble precipitate by the adjusting means,
A coagulation tank provided with an addition means for adding a polymer flocculant to the reaction liquid introduced from the reaction tank;
A precipitation tank in which a reaction liquid is introduced from the aggregating tank and separated into treated water and sludge;
A part of the sludge is introduced from the sedimentation tank, an ultrasonic oscillator is provided for irradiating the sludge with ultrasonic waves, and an ultrasonic wave is sent back to the reaction tank for the reaction liquid irradiated with ultrasonic waves by the ultrasonic oscillator An irradiation tank;
An apparatus for treating boron-containing wastewater, comprising: A first reaction tank provided with a mixing means for adding and mixing a part of the reaction liquid returned from the second reaction tank while introducing wastewater containing boron;
A second reaction tank provided with an adjusting means for adding an aluminum compound and a calcium compound to the reaction liquid introduced from the first reaction tank to adjust the pH to 9 or more to produce a reaction liquid and an insoluble precipitate;
A coagulation tank in which the reaction solution is introduced from the second reaction tank and an addition means for adding a polymer flocculant is provided;
A precipitation tank in which the reaction liquid is introduced from the coagulation tank and separated into treated water and sludge;
An apparatus for treating boron-containing wastewater, comprising:

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