JP6565268B2 - Method and apparatus for treating inorganic carbon-containing water - Google Patents

Description

  The present invention relates to a method and apparatus for efficiently aggregating inorganic carbon-containing water containing inorganic carbon in an amount of 50 mg / L or more and having a problem of agglomeration inhibition due to inorganic carbon to solid-liquid separation.

  In order to remove organic carbon and turbidity contained in the water to be treated, it is common to perform a solid-liquid separation treatment using a precipitation tank, a filter, or a turbidity removal membrane. At this time, in order to increase the solid-liquid separation efficiency, agglomeration is generally performed prior to the solid-liquid separation.

  Conventionally, as the aggregating chemical (aggregating agent), inorganic aggregating agents such as iron salts and aluminum salts are typical.

  However, when a lot of inorganic carbon is contained in water, in the aggregation pH range of pH 5.5 to 8.5, the carbonate ion derived from inorganic carbon inhibits the reaction between the inorganic flocculant and the turbidity or organic matter, resulting in poor aggregation. cause.

Generally, the inorganic carbon concentration in river water and lake water in Japan is around 10 mg / L, and does not inhibit the inorganic flocculant. Moreover, since the concentration of inorganic carbon does not exceed 50 mg / L even in general factory effluent, the above-mentioned poor aggregation due to inorganic carbon does not become a problem.
However, some industrial wastewaters have an inorganic carbon concentration increased to 50 mg / L or more depending on chemicals added during the manufacturing process and specific processes.

In ordinary wastewater treatment, a method of adding a large amount of a flocculant is common to improve agglomeration failure, but there is a problem that a large amount of sludge is generated. Moreover, even if a large amount of a flocculant is added to wastewater containing a large amount of inorganic carbon, the organic carbon and turbidity that should be removed are deteriorated and cannot be removed by, for example, a precipitation tank or a filter. .
Turbidity, organic carbon, etc. that could not be removed in the latter stage cause environmental pollution when discharged outside the system. Further, for example, when there is a turbidity removal membrane or a reverse osmosis (RO) membrane in the subsequent stage of the settling tank or the filter, it also leads to contamination thereof.
Ozone treatment is also proposed as a method to reduce organic carbon that cannot be removed by a subsequent filter, etc., but it costs power, so the organic carbon concentration is reduced as much as possible by coagulation and solid-liquid separation treatment in the previous stage. It is effective to do.

Conventionally, it is known to use together with an inorganic flocculant and a cationic organic flocculant in order to increase the removal efficiency of organic carbon and turbidity in wastewater. For example, Patent Document 1 discloses wastewater such as paper mill wastewater. In addition, a method has been proposed in which a water-soluble cationic polymer is added and mixed, then an inorganic flocculant is added and mixed, and then an anionic polymer flocculant is added to perform an agglomeration treatment.
Patent Document 2 proposes a method in which polydiallyldimethylammonium chloride having an intrinsic viscosity of 0.4 to 1.4 and an inorganic flocculant are added to an anionic dye wastewater and agglomerated at a predetermined pH.
Patent Document 3 proposes a flocculant composition obtained by mixing a cationic organic flocculant and an inorganic flocculant.

  However, all of the conventional techniques use a cationic organic flocculant together with an inorganic flocculant in order to improve the removal rate of organic carbon and turbidity in wastewater, and focused on aggregation inhibition by inorganic carbon. No agglomeration technique has been proposed.

JP 2011-131167 A JP-A-6-126286 JP 59-82911 A

  An object of the present invention is to provide a method and an apparatus for efficiently coagulating inorganic carbon-containing water containing inorganic carbon in an amount of 50 mg / L or more and having a problem of aggregation inhibition due to inorganic carbon to solid-liquid separation.

As a result of intensive studies to solve the above-mentioned problems, the present inventors preferably added a combination of an inorganic flocculant and an organic coagulant having a cationic group to inorganic carbon-containing water. It has been found that by using an organic coagulant having a colloidal equivalent cationic group, inorganic carbon-containing water can be efficiently coagulated and organic carbon and turbidity can be removed to a high degree.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] Inorganic carbon-containing water characterized by solid-liquid separation after adding an inorganic flocculant and an organic coagulant having a cationic group to water to be treated containing 50 mg / L or more of inorganic carbon and aggregating it. Processing method.

[2] A method for treating inorganic carbon-containing water according to [1], wherein an organic coagulant having a cationic group is added to the water to be treated, and then an inorganic flocculant is added to perform the coagulation treatment.

[3] The method for treating inorganic carbon-containing water according to [1] or [2], wherein the organic coagulant having the cationic group has a colloid equivalent of 1 meq / g or more.

[4] The inorganic carbon-containing water according to any one of [1] to [3], wherein the amount of the organic coagulant having a cationic group is controlled according to the inorganic carbon concentration of the water to be treated. Processing method.

[5] The method for treating inorganic carbon-containing water according to any one of [1] to [4], further comprising adding an organic flocculant having an anion group to the water to be treated for aggregation treatment.

[6] The method for treating inorganic carbon-containing water according to any one of [1] to [5], wherein the separated water obtained by the solid-liquid separation is subjected to a turbidity membrane or reverse osmosis membrane separation treatment.

[7] A treatment apparatus for inorganic carbon-containing water that coagulates and treats water to be treated containing 50 mg / L or more of inorganic carbon and then solid-liquid separates the organic coagulant having an inorganic flocculant and a cationic group in the water to be treated. An apparatus for treating inorganic carbon-containing water, characterized by comprising a coagulation treatment means for performing coagulation treatment by adding water and a solid-liquid separation means for solid-liquid separation of the coagulation treated water.

[8] In the inorganic carbon according to [7], the aggregation treatment means is a means for adding an organic coagulant having a cationic group to the water to be treated and then adding an inorganic flocculant to perform the aggregation treatment. Water treatment equipment.

[9] An apparatus for treating inorganic carbon-containing water according to [7] or [8], wherein the organic coagulant having the cationic group has a colloid equivalent of 1 meq / g or more.

[10] In any one of [7] to [9], the inorganic carbon concentration measuring means for measuring the inorganic carbon concentration of the water to be treated, and the addition of the organic coagulant having the cationic group based on the measured value And a control means for controlling the amount of the inorganic carbon-containing water treatment apparatus.

[11] In any one of [1] to [4], the aggregating treatment means is a means for aggregating by further adding an organic flocculant having an anion group to the water to be treated. Carbon-containing water treatment equipment.

[12] The inorganic carbon-containing water according to any one of [7] to [11], comprising a turbidity membrane or reverse osmosis membrane separation means into which the separated water obtained by the solid-liquid separation means is introduced. Processing equipment.

According to the present invention, inorganic carbon-containing water containing inorganic carbon in an amount of 50 mg / L or more and having a problem of aggregation inhibition due to inorganic carbon is efficiently agglomerated to highly solid-liquid-separate organic carbon and turbidity in water. be able to.
According to the present invention, turbidity and organic carbon can be removed to a high degree by preventing the inhibition of aggregation by inorganic carbon. Film contamination such as the above can be prevented, and the frequency of cleaning the film can be reduced. Moreover, the processing cost can be reduced by reducing the load on the subsequent processing apparatus such as ozone treatment.

It is a systematic diagram which shows an example of embodiment of the processing apparatus of the inorganic carbon containing water of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

<Mechanism>
The mechanism of the coagulation-improving effect according to the present invention in which an organic coagulant having a cationic group (hereinafter sometimes referred to as “cationic organic coagulant”) and an inorganic coagulant are added together is as follows. .

Only by adding a cationic organic coagulant, turbidity and organic carbon in the water to be treated cannot be sufficiently coagulated.
By adding an inorganic flocculant, turbidity and organic carbon can be agglomerated, but as described above, in the case of water to be treated with a high inorganic carbon concentration, carbonate ions derived from inorganic carbon and turbidity with the inorganic flocculant. Impedes reaction with quality and organic carbon.
When a cationic organic coagulant is added to such water to be treated, the inorganic carbon in the water reacts with the cationic organic coagulant to suppress aggregation inhibition by the inorganic carbon, and the inorganic coagulant and turbid or organic The reactivity with carbon can be improved.

  In the present invention, a combination of a cationic organic coagulant and an inorganic flocculant can provide a good flocculation effect. However, an organic flocculant having an anionic group (hereinafter referred to as “anionic organic flocculant”) In combination with an anionic organic flocculant, the aggregate flocs can be coarsened to improve the quality of the solid-liquid separation water.

<Treatment water>
The water to be treated in the present invention is water that has an inorganic carbon concentration of 50 mg / L or more and easily inhibits the aggregation of the inorganic flocculant by inorganic carbon.
The cause of the generation of water to be treated with such a high inorganic carbon concentration is not clear, but it is assumed that there are processes unique to factories and the like.
The SS concentration of these waters is often 10 mg / L or more, and the electrical conductivity is 100 mS / m or more. In addition, when performing agglomeration, precipitation, filtration treatment, etc., usually using river water or lake water as a water source, the inorganic carbon concentration is around 10 mg / L, and may be 2 mg / L or less.

<Cationic organic coagulant>
The cationic organic coagulant is not particularly limited, and those conventionally used or similar can be used. For example, polyethyleneimine, dicyandiamide-formalin condensate, alkylene polyamine-alkylene dihalide condensate, poly Dimethyldiallylammonium salt, polyacrylamide Mannich modified product, polyacrylamide Hofmann degradation product, epihalohydric-amine condensate, cationized starch, cationized guar gum, chitosan, aminoalkyl (meth) acrylate (including tertiary and quaternized products) ) Homopolymers or copolymers with acrylamide or other monomers, and in particular, epihalohydric-amine condensates, polyethyleneimines, dicyandiamide-formalin condensates, alkylenepolyamides, etc. - alkylene dihalide condensates, polydimethyl diallyl ammonium salts are preferred. These may use only 1 type and may mix and use 2 or more types.

  As the cationic organic coagulant, those having high reactivity with inorganic carbon due to a cation group are preferable, and those having a colloidal equivalent of 1 meq / g or more, particularly 5 meq / g or more are used as the inorganic flocculant. The organic coagulant is preferred in that it is excellent in the effect of improving the cohesiveness due to the combined use. Although there is no restriction | limiting in particular about the upper limit of the colloid equivalent of a cationic organic coagulant, Usually, it is 20 meq / g or less.

  The amount of the cationic organic coagulant added to the water to be treated varies depending on the quality of the water to be treated and the type of the cationic organic coagulant, but should be 2 to 30 mg / L, particularly about 5 to 10 mg / L. Is preferred. If the amount of the cationic organic coagulant added is too small, the effect of improving the cohesiveness by adding the cationic organic coagulant cannot be obtained sufficiently. In addition, it can become contaminated.

  In particular, it is preferable to control the addition amount of the cationic organic coagulant in accordance with the inorganic carbon concentration in the water to be treated in order to prevent the cationic organic coagulant from being excessive or insufficient and to obtain a good coagulation effect. Therefore, it is preferable to measure the inorganic carbon concentration of the water to be treated with GE Sievers 900 or the like, and to control the injection of the cationic organic coagulant based on the measurement result. In this case, the cationic organic coagulant can be controlled so as to have an addition amount (mg / L) of about 1 to 5% by weight with respect to the inorganic carbon concentration (mg / L) of the water to be treated. preferable. In addition, the inorganic carbon concentration of to-be-processed water may be measured continuously and may be measured intermittently.

<Inorganic flocculant>
As the inorganic flocculant, aluminum-based or iron-based inorganic flocculants can be used. These may use only 1 type and may mix and use 2 or more types. Specifically, examples of the aluminum-based inorganic flocculant include aluminum sulfate (sulfate band), polyaluminum chloride (PAC), and aluminum chloride. Examples of the iron-based inorganic flocculant include ferric chloride, ferrous chloride, ferrous sulfate, ferric sulfate, and polyiron sulfate.

  The amount of the inorganic flocculant added to the water to be treated varies depending on the quality of the water to be treated, the type of the inorganic flocculant, etc., but is preferably about 50 to 500 mg / L, particularly about 100 to 300 mg / L. If the amount of the inorganic flocculant added is too small, turbidity and organic carbon in the water to be treated cannot be sufficiently agglomerated to obtain solid water-liquid separated water with good water quality, but the present invention is a cationic organic coagulant. In combination, the required amount of the inorganic flocculant is reduced, and excessive addition of the inorganic flocculant leads to an increase in the amount of sludge generated, and is not preferable in terms of chemical cost. .

<Anionic organic flocculant>
As an anionic organic flocculant, 1 type (s) or 2 or more types, such as sodium polyacrylate, a polyacrylamide partial hydrolyzate, a partial sulfomethylation polyacrylamide, a poly (2-acrylamide) 2-methylpropane sulfate, are used. be able to.

  When an anionic organic flocculant is used in combination, the amount added varies depending on the quality of the water to be treated and the type of anionic organic flocculant used, but is usually about 0.1 to 5 mg / L.

<Aggregation treatment>
When a cationic organic coagulant and an inorganic flocculant are added to the water to be treated containing inorganic carbon for coagulation treatment, the cationic organic coagulant and the inorganic flocculant may be added simultaneously or separately. Although it is good, from the viewpoint of preventing the aggregation of the inorganic flocculant caused by inorganic carbon due to the addition of the cationic organic coagulant, after adding the cationic organic coagulant in advance, the inorganic flocculant is added and the coagulation treatment is performed. Is preferred. In this case, after adding a cationic organic coagulant to the water to be treated and stirring for about 1 to 20 minutes, it is preferable to add an inorganic flocculant and stir for about 3 to 20 minutes for aggregation. .

  When an anionic organic flocculant is used in combination, the anionic organic flocculant is preferably added after the inorganic flocculant is added.

  The pH during the flocculation treatment is preferably a suitable pH according to the inorganic flocculant to be used. If it is an aluminum-based inorganic flocculant, the pH is about 5.8 to 7.0, and if it is an iron-based inorganic flocculant, the pH is 5 It is preferable to adjust the pH by adding acid or alkali to about 8 to 7.5 as necessary. However, with this treatment method, it is possible to carry out the treatment without special pH adjustment.

<Solid-liquid separation>
The solid-liquid separation means after the coagulation treatment is not particularly limited, and a precipitation tank, a pressure levitation tank, a membrane separation device, a filter and the like can be used.

<Post-processing>
In the latter stage of the solid-liquid separation means, particularly when a precipitation tank is used as the solid-liquid separation means, a filter, a turbidity membrane device, etc. are provided in the latter stage in order to remove the solid-liquid separation water SS to a higher degree. Also good. Moreover, a reverse osmosis (RO) membrane separation apparatus may be provided to perform a desalting treatment or to treat residual organic substances by ozone treatment. In this case, according to the present invention, it is possible to obtain solid water-liquid separated water having a good water quality in which turbidity and organic carbon are sufficiently reduced by improving the cohesiveness. It is possible to reduce costs and perform stable operation.

<Inorganic carbon-containing water treatment device>
Hereinafter, the treatment apparatus for inorganic carbon-containing water of the present invention will be described with reference to FIG.
FIG. 1 is a system diagram showing an example of an embodiment of an apparatus for treating inorganic carbon-containing water according to the present invention.

The raw water in the raw water tank 1 is coagulated for a predetermined time in the first coagulation tank 2 after the cationic organic coagulant is added in the process of being fed to the first coagulation tank 2 from the pipe 11.
The aggregating water in the first aggregating tank 2 is agglomerated in the second aggregating tank 3 for a predetermined time after the inorganic aggregating agent is added in the process of being fed to the second aggregating tank 3 from the pipe 12.
The agglomerated water in the second aggregating tank 3 is subjected to solid-liquid separation in the precipitation tank 4 after the anionic organic flocculant is added in the process of being fed to the precipitation tank 3 via the pipe 13.
The separation water in the settling tank 4 is supplied to the turbidity membrane device 5 through the pipe 14 and further turbidized, and then supplied to the RO membrane separation device 6 through the pipe 15 and subjected to the RO membrane separation treatment. It is discharged out of the system from the pipe 16 as treated water.

FIG. 1 shows an example of the treatment apparatus for inorganic carbon-containing water of the present invention, and the present invention is not limited to the illustrated one.
The cationic organic coagulant and the inorganic coagulant may be added to the coagulation tank instead of pipe injection, and an anionic organic coagulant may be added and a coagulation tank for coagulation treatment may be provided.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Aggregating agent]
The aggregation treatment agents used in the following examples and comparative examples are as follows.
Inorganic flocculant: Ferric chloride (manufactured by Showa Chemical Industry Co., Ltd.)
Cationic organic coagulant A: epichlorohydrin-dimethylamine condensate, colloid equivalent 6.5 meq / g
Cationic organic coagulant B: polydimethyldiallylammonium chloride, colloidal equivalent 0.5 meq / g
Anionic organic flocculant: copolymer of sodium acrylate and acrylamide

[Raw water]
The raw water subjected to the flocculation treatment in the following Examples and Comparative Examples is of the following water quality obtained by biological treatment of the wastewater (inorganic carbon concentration 55 to 250 mg / L) of the A factory. Inorganic carbon concentration does not change even after biological treatment.

[Evaluation of aggregation performance]
In the following Examples and Comparative Examples, using a water treatment apparatus in which a coagulation tank, a precipitation tank, and a turbidity removing film apparatus are connected in this order, continuous treatment is performed for 7 days, and the aggregation performance is evaluated using the following evaluation items. did.

Turbidity of solid-liquid separation water: The separation water of the precipitation tank was collected and turbidity (NTU) was measured with a turbidimeter.
Sediment sludge ratio: The amount of sludge separated in the sedimentation tank was weighed, and relative evaluation was made with the case of Example 1 being 1.
Filtered water SDI: The separated water collected in the settling tank was collected. The SDI of filtered water obtained by filtering with 5A filter paper was measured according to ASTM D4189-95 (2002).
MF membrane differential pressure increase rate: Separation water in the sedimentation tank is continuously passed through the turbidity membrane (PVDF MF membrane with a pore size of 0.1 μm manufactured by Asahi Kasei Co., Ltd.) in the latter stage of the precipitation tank at a flow rate of 2 m ³ / m ² / day The pressure on the supply water side and the treated water side when water was measured was measured, and the rate of increase in differential pressure (kPa / day) was calculated.

[Example 1]
The cationic organic coagulant A 5 mg / L and the inorganic coagulant 200 mg / L were added to the coagulation tank, and the pH was not adjusted. After coagulation treatment for 10 minutes, water was passed through the precipitation tank and the turbidity removal membrane device.

[Example 2]
Two agglomeration tanks are provided. After adding 5 mg / L of the cationic organic coagulant A in the first agglomeration tank and aggregating for 5 minutes, adding 200 mg / L of inorganic aggregating agent in the second agglomeration tank and aggregating for 10 minutes Except that, the same procedure as in Example 1 was performed.

[Example 3]
In Example 2, the inorganic carbon concentration of the raw water was measured with a GE Sievers 900 once an hour, so that the cationic organic coagulant A was 10% by weight with respect to the inorganic carbon concentration (mg / L). The same operation as in Example 2 was conducted except that the addition amount (mg / L) was controlled.

[Example 4]
In Example 2, it carried out like Example 2 except having added 2 mg / L of anionic organic flocculants to the effluent of the 2nd flocculent tank.

[Example 5]
In Example 3, it carried out like Example 3 except having used the cationic organic coagulant B instead of the cationic organic coagulant A.

[Comparative Example 1]
In Example 1, it carried out like Example 1 except having added neither the cationic organic coagulant A nor an inorganic flocculant.

[Comparative Example 2]
In Example 1, it carried out like Example 1 except not having added cationic organic coagulant A.

[Comparative Example 3]
Example 1 was carried out in the same manner as Example 1 except that the cationic organic coagulant A was not added and the inorganic flocculant addition amount was doubled to 400 mg / L.

  Table 1 shows the results of Examples 1 to 5 and Comparative Examples 1 to 3.

Table 1 shows the following.
In Comparative Example 1 in which no flocculant is used and in Comparative Example 2 in which flocculation treatment is performed using only the inorganic flocculant, the turbidity of the solid-liquid separated water is high.
In Comparative Example 3 in which the amount of inorganic flocculant added was double, the solid-liquid separation water turbidity and the SDI of filtered water were good values, but the amount of sludge was about 1.89 times that of Example 1. became.

On the other hand, the favorable result was obtained in Examples 1-5 which used together the cationic organic coagulant and the inorganic flocculant.
In particular, in Example 2 in which an inorganic flocculant was added after adding a cationic organic coagulant, the turbidity of solid-liquid separated water was lower than that in Example 1, and the SDI value of filtered water was also low. The rate of increase in the differential pressure of the membrane also decreased.
In Example 3 where the addition amount of the cationic organic coagulant was controlled according to the inorganic carbon concentration of the raw water, the turbidity of the solid-liquid separated water was lower than that of Example 2, and the fluctuation range was smaller. The differential pressure increase rate of the MF membrane was further improved.
Furthermore, in Example 4 to which the anionic organic flocculant was added, the flocs flocs increased and the solid-liquid separation water turbidity decreased.
Example 5 uses a cationic organic coagulant having a low colloidal equivalent, and the turbidity of solid-liquid separation water and the rate of increase in the differential pressure of filtered water SDI and MF membrane are inferior to those of other examples. Favorable results are obtained as compared with Comparative Examples 1 and 2, and the amount of sludge can be reduced as compared with Comparative Example 3.

DESCRIPTION OF SYMBOLS 1 Raw water tank 2 1st flocculation tank 3 2nd flocculation tank 4 sedimentation tank 5 Turbidity removal membrane apparatus 6 RO membrane separation apparatus

Claims (9)

  An inorganic flocculant and an organic coagulant having a cationic group with a colloidal equivalent of 1 meq / g or more are added to water to be treated containing 50 mg / L or more of inorganic carbon, and the flocculant is treated at a pH of 5.5 to 8.5. Then, the method for treating inorganic carbon-containing water is characterized in that solid-liquid separation is performed.   The method for treating inorganic carbon-containing water according to claim 1, wherein an organic coagulant having the cationic group is added to the water to be treated, and then an inorganic flocculant is added to perform an aggregation treatment.   The method for treating inorganic carbon-containing water according to claim 1 or 2, wherein the amount of the organic coagulant having a cationic group is controlled according to the inorganic carbon concentration of the water to be treated.   The method for treating inorganic carbon-containing water according to any one of claims 1 to 3, further comprising adding an organic flocculant having an anion group to the water to be treated for agglomeration treatment.   5. The method for treating inorganic carbon-containing water according to claim 1, wherein the separated water obtained by the solid-liquid separation is subjected to a turbidity membrane or reverse osmosis membrane separation treatment. An inorganic flocculant and an organic coagulant having a cationic group with a colloidal equivalent of 1 meq / g or more are added to water to be treated containing 50 mg / L or more of inorganic carbon, and agglomeration is performed at pH 5.5 to 8.5. a flocculation treatment unit, a processing device for a continuously machine the carbon-containing water that have a and solid-liquid separation means for solid-liquid separation aggregation process water,
An inorganic carbon concentration measuring means for measuring the inorganic carbon concentration of the water to be treated, and a control means for controlling the addition amount of the organic coagulant having the cationic group based on the measured value Carbon-containing water treatment equipment .   7. The inorganic carbon-containing water according to claim 6, wherein the flocculation treatment means is a means for adding the organic coagulant having the cationic group to the water to be treated and then adding an inorganic flocculant to perform the flocculation treatment. Processing equipment. According to claim 6 or 7, wherein the aggregation processing means, the processing apparatus of inorganic carbon-containing water, wherein the a means for flocculation treatment by adding an organic flocculant having a further anionic groups to the water to be treated. The apparatus for treating inorganic carbon-containing water according to any one of claims 6 to 8 , further comprising a turbidity removal membrane or reverse osmosis membrane separation means into which the separated water obtained by the solid-liquid separation means is introduced. .

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