JP4160882B2 - Flocculant for wastewater treatment - Google Patents

Description

  The present invention relates to a flocculant for discharge treatment that is particularly suitable for advanced treatment of wastewater containing hardly sedimentable substances.

When wastewater treatment is performed using a flocculant, in order to efficiently agglomerate suspended particles, the flocculant is uniformly mixed in the suspension and then rapidly stirred to form a micro floc group. In addition, it is known to use a combination of slow agitation and collision / aggregation of micro flock groups and fine particle groups. (Non-Patent Document 1)
Commonly used flocculants include inorganic flocculants represented by aluminum sulfate, polyaluminum chloride, iron chloride and the like, and water-soluble polymer flocculants represented by polyacrylamide and the like. Inorganic flocculants are prone to agglomerate due to positively charged hydroxides, and polymer flocculants aggregate the particles that come into contact with each other by a cross-linking action to form aggregates. In many cases, an agent and a polymer flocculant are used in combination.

  And also when using an inorganic flocculant and a polymer flocculant in combination, as described above, after adding the inorganic flocculant, rapidly stirring to form a micro floc group, adding the polymer flocculant, A treatment method in which a larger aggregate group is formed by stirring is applied.

  In Patent Document 1, treated water obtained by adding bentonite and a cationic polymer flocculant to waste water containing a surfactant, oil, etc. is led to a mixing tank, and an agglomeration reaction is performed by adding an aluminum salt and an alkali agent. After carrying out the method, a method for separating the floc flocs in the sedimentation basin is disclosed. However, since it is necessary to add a coagulant such as an inorganic coagulant and a polymer coagulant separately with a time lag, it takes time and requires a plurality of coagulant injection means, and the equipment area increases. There is also a disadvantage that the device becomes large.

  Non-Patent Document 2 discloses a wastewater treatment agent [(Yes) Westec comprising an A agent mainly composed of bentonite and plant extract and a B agent mainly composed of aluminum sulfate and a starch derivative cationic acrylamide polymer. The product name “WESTAK” sold by is introduced. However, since this wastewater treatment agent needs to first add a powdery A agent to the aqueous paint waste liquid, and then add a liquid obtained by dissolving the B agent in water. There are problems that the equipment area is increased and that a plurality of means for supplying the flocculant are required.

  Patent Document 2 discloses a mixed flocculant in which an adsorbing substance such as bentonite, carbonate, sulfate, and a polymer flocculant are mixed in a predetermined ratio. Although this technology solves the problem that multiple means for adding flocculant are required, if the adsorbing rate of the flocculant and the aggregation / sedimentation rate are slow, it takes time for the sedimentation separation, and the equipment area increases. The problem remains.

On the other hand, washing wastewater containing surfactants, oils, etc. has a problem that the oils are highly emulsified with surfactants, so the treatment with flocculants increases the equipment area and increases the amount of flocculant input. was there. For this reason, the residence time of the stirring tank and the coagulation sedimentation tank can be greatly shortened, or it is necessary to select a coagulant capable of coagulation sedimentation treatment even when the water surface sedimentation load is 1 or more.
Japanese Patent No. 1682255 JP-A-9-225208 Agglomeration Engineering-Basics and Applications-Japan Powder Industry Technology Association The Chemical Daily on June 26, 2001

  The present invention solves the above problems and is particularly suitable for advanced treatment of wastewater containing hardly sedimentable substances, and it is an object to provide a flocculant for wastewater treatment that can contribute to downsizing of wastewater treatment facilities. To do.

  The present invention is a flocculant for removing COD components in wastewater as a means for solving the problem, and is added to the wastewater at a concentration of 100 mg / L, stirred for 10 minutes, and then allowed to settle. A coagulant for wastewater treatment in which the settling speed of the aggregated floc is 0.3 to 3.0 cm / min is provided.

  In the present invention, the COD component means an oxidizable component that develops a COD value, and removing the COD component means reducing COD.

Further, the present invention provides another solution to the problem. The tank capacity of the stirring part is V ₁ (m ³ ), the tank capacity of the precipitation part is V ₂ (m ³ ), and the sedimentation area of the precipitation part is A (m ² ). When the coagulation-sedimentation treatment is performed in the coagulation-sedimentation tank, a wastewater treatment coagulant is provided which is processed so as to satisfy the following requirements (a) to (e).

(A) It adds to a stirring part with the density | concentration of 20-200 mg / L with respect to waste_water | drain;
(B) Process with a processing amount F (m ³ / Hr);
_(C) agitating section water mean residence time expressed in _V 1 / F is 5 to 15 min;
_{(D) V} 2 / precipitation section water mean residence time represented by F is 10 to 30 minutes;
(E) The water area load represented by F / A is 1 to 10 m / Hr;
In the present invention, the sedimentation area A of the sedimentation part is the sum of the areas where the aggregated flocs can accumulate in the sedimentation part, and includes the area of the tank bottom and the area of the sedimentation plate.

  According to the flocculant for wastewater treatment of the present invention, a combination of rapid stirring and slow stirring is unnecessary, there is no need to divide the flocculant into two components for each component, a bulk density is high, and a component having high sedimentation properties is added. The use of this solves the problem of increasing the flocculant equipment area and requiring a plurality of flocculant charging means. For this reason, if the coagulant | flocculant for wastewater treatment of this invention is applied, a wastewater treatment apparatus can be reduced more in size.

  Furthermore, according to the flocculant for wastewater treatment of the present invention, wastewater containing difficult-to-settling substances, such as car wash wastewater, can be treated at a high level, and the wastewater treatment apparatus can be downsized. It can be easily applied to a car wash wastewater treatment apparatus.

  By using the wastewater treatment flocculant of the present invention, the COD removal rate (determined by the method described in Examples) can be significantly increased.

  The flocculant for wastewater treatment of the present invention is added at a concentration of 100 mg / L to the wastewater, and after stirring for 10 minutes, the sedimentation rate of the flocs flocs when allowed to stand still is 0.3 to 3.0 cm. / Min, preferably 0.5 to 2.0 cm / min.

  If the sedimentation rate is 0.3 cm / min or more, the sedimentation property is good and the volume of the sedimentation tank can be reduced. If the sedimentation rate is 3.0 cm / min or less, the water quality after treatment evaluated by COD is also obtained. Get better.

In the flocculant for wastewater treatment of the present invention, the tank capacity of the stirring part is V ₁ (m ³ ), the tank capacity of the precipitation part is V ₂ (m ³ ), and the sedimentation area of the precipitation part is A (m ² ). When the coagulation precipitation treatment is performed in a certain coagulation sedimentation tank, the treatment is performed so as to satisfy the following requirements (a) to (e).

(A) It adds to a stirring part with the density | concentration of 20-200 mg / L with respect to waste_water | drain;
(B) Process with a processing amount F (m ³ / Hr);
_(C) agitating section water mean residence time expressed in _V 1 / F is 5 to 15 min;
_{(D) V} sedimentation section water mean residence time expressed in 2 / F is 10 to 30 minutes;
(E) The water area load represented by F / A is 1 to 10 m / Hr;
Thus, by processing so as to satisfy (a) to (e), the COD removal rate can be significantly increased.

  The flocculant for wastewater treatment of the present invention preferably contains 30 to 60% by mass of bentonite (montmorillonite). Bentonite acts to reduce the solution viscosity (viscosity of wastewater) by adsorbing the oil component emulsified with a surfactant, the main component of montmorillonite, compared to other flocculant components. Since the density is also high, it is excellent in terms of good sedimentation.

  The flocculant for wastewater treatment of the present invention preferably contains a component selected from the following organic flocculants and inorganic flocculants as the remaining components other than bentonite.

  Inorganic flocculants other than bentonite are selected from aluminum sulfate, polyaluminum chloride, magnesium chloride, ferric chloride, ferrous sulfate, ferric sulfate, slaked lime, sodium silicate, sodium aluminate, aluminum alums, etc. 1 type or more to be mentioned. Of these, aluminum sulfate is preferred.

  Examples of organic flocculants include poly (meth) acrylic acid esters, poly (meth) acrylamides, acrylic copolymers obtained by copolymerizing hydrophilic monomers such as (meth) acrylic acid and (meth) acrylamide, and sodium alginate. , Sodium salt of carboxymethyl cellulose, maleic acid copolymer, poly (meth) acrylamide, sodium lignin sulfonate, caustic starch, polyoxyethylene, (meth) acrylic acid ester and (meth) acrylamide anionic, cationic or Nonionic polymer flocculants, anionic, cationic or nonionic polymer flocculants such as copolymers of (meth) acrylic acid and acrylamide, polyamines, polydicyandiamides, cationized starch, cationic poly (Meth) acrylamide, water-soluble aniline tree , Polythiourea, polyethyleneimine, quaternary ammonium salts, polyvinyl pyridines, cationic polymer flocculants such as chitosan, low-molecular amine flocculants such as propylene diamine and the like. Among these, polyacrylamide, polyacrylic acid ester, and sodium alginate are preferable, and cationic polyacrylamide and sodium alginate are most preferable.

  The content of montmorillonite as a component of the flocculant is preferably 30 to 60% by mass, more preferably 40 to 55% by mass, still more preferably 45 to 50% by mass, and the inorganic flocculant other than montmorillonite is preferably 30 to 60%. % By mass, more preferably 40 to 55% by mass, still more preferably 45 to 50% by mass, and the organic flocculant is preferably 1 to 14% by mass, more preferably 2 to 12% by mass, still more preferably 3 to 10% by mass. %.

  Next, the preferable compounding example of the flocculant for wastewater treatment of this invention is illustrated.

(1) Formulation Example 1
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Cationic polyacrylamide 1-8% by mass
(2) Formulation example 2
Bentonite (montmorillonite) 30-60% by mass
Ferric sulfate 40-60% by mass
Cationic, anionic or nonionic polyacrylamide 1-10% by mass
(3) Formulation Example 3
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Sodium alginate 1-5% by mass
Cationic polyacrylamide 1-5% by mass
The wastewater treatment flocculant of the present invention is in the form of powder or particles, but if it can be rapidly disintegrated when put into wastewater, a method such as compression molding is applied to obtain a desired shape. It can also be molded.

  The amount of the flocculant for wastewater treatment of the present invention is appropriately set according to the degree of dirt of the wastewater to be treated, but for the wastewater whose COD concentration is about 30 to 300 mg / L, the concentration of the flocculant in the wastewater May be added so as to be about 20 to 200 mg / L.

  When using the flocculant for wastewater treatment of the present invention, a method for supplying all of the required amount at once to a wastewater to be treated, a method for continuously supplying the required amount, and dividing the required amount into multiple times Applying method can be applied.

  The flocculant for wastewater treatment of the present invention can be applied as a flocculant for various wastewater treatment facilities and treatment equipment, and can be particularly useful for downsizing the treatment equipment because the equipment area for the flocculant can be reduced. is there.

  The flocculant for wastewater treatment of the present invention is a wastewater treatment containing oil and cleaning agents, wastewater discharged from households, pools and bathhouses, food factory wastewater treatment containing squeezed rice juice, sugar and protein, water purification treatment, treatment It can also be applied to the purification of natural water with a high degree of pollution.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

(1) Sedimentation rate The sedimentation rate is 80% of the aggregate flocs present immediately after stirring the flocculant at a concentration of 100 mg / L in a 1 L beaker containing 1 L of measurement wastewater and stirring at 160 rpm. Based on the time T until Hcm settled from the water surface and deposited on the bottom, it was calculated as H / T. Specifically, the turbidity at the point of Hcm below the surface of the water immediately after stirring and at each sedimentation time was examined, and the time T and sedimentation distance H when the turbidity decreased by 80% were measured and calculated by the above formula. The turbidity was measured with a turbidimeter (TURBIDIMETER 2100P: manufactured by HACH).

(2) COD removal rate The COD concentration of the car wash wastewater is X, the COD concentration after the coagulation sedimentation treatment (for example, the supernatant water from the sedimentation tank of the coagulation sedimentation tank) is Y, and the COD removal rate is (1-Y / X) It was defined as x100 and calculated.

  Regarding COD concentration, 2 ml of waste water (raw water) and supernatant were put into a COD reagent vial (Cat. 21259-25; 0 to 1,500 mg / L; manufactured by HACH) and heated at 150 ° C. for 2 hours. Then, it cooled and measured with the water quality analyzer (DR / 2010) made from HACH.

(3) Wastewater treatment experiment A wastewater recycling device consisting of the following coagulation / sedimentation processing unit, membrane separation processing unit and advanced processing unit was installed beside the car washer in the gas station, and the amount treated (the amount treated in the coagulation / sedimentation processing unit). F was set to 2.4 m ³ / H (other than Comparative Example 3; Comparative Example 3 was 9.6 m ³ / Hr), and car wash drainage treatment was performed.

(Coagulation sedimentation processing section)
A to D type coagulation sedimentation tanks comprising three tanks, a stirring tank, a sedimentation tank, and a membrane raw water storage tank, were used.

A type stirring tank capacity (V ₁ ): 0.4 m ³ , sedimentation tank capacity (V ₂ ): 0.6 m ³ , sedimentation area (A) of the sedimentation tank: 0.5 m ² , membrane raw water storage tank: 0.2 m ³
B type stirring vessel volume _(V 1): 0.3m ^3, precipitation tank volume _(V 2): 0.5m ^3, sedimentation area of the sedimentation tank (A): 0.3m ^2, film raw water storage tank: 0.2 m ³
C type stirring tank capacity (V ₁ ): 0.5 m ³ , sedimentation tank capacity (V ₂ ): 0.7 m ³ , sedimentation area (A) of the sedimentation tank: 1.0 m ² , membrane raw water storage tank: 0.2 m ³
The flocculant was charged into the stirring tank by a powder feeder. The input amount was set to 100 mg / L with respect to the waste water.

In addition, as the membrane separation processing unit, three cellulose acetate hollow fiber membrane modules (membrane area 16 m ² , fractional molecular weight: 150,000) were used, and the transmembrane pressure difference was maintained at 15 to 25 kPa. A column packed with activated carbon (CW130A, manufactured by Nimura Chemical Industry Co., Ltd.) was used as the advanced processing section.

Example 1
Each component of 47% by weight of bentonite (manufactured by Hojun), 49% by weight of aluminum sulfate (manufactured by Asada Chemical Co., Ltd.), and 4% by weight of cationic polyacrylamide (manufactured by Mitsui Cytec Co., Ltd., Akofloc C486) is mixed to obtain a flocculant 1 for wastewater treatment. Got.

  Using this flocculating agent 1, car wash wastewater (average COD value 63 mg / L, average turbidity 16 NTU) was processed using an A-type flocculation sedimentation tank. Table 1 shows the COD removal rate after the treatment.

Example 2
50% by mass of bentonite (manufactured by Hojun), 45% by mass of aluminum sulfate (manufactured by Asada Chemical Co., Ltd.), and 5% by mass of cationic polymethacrylic acid ester (manufactured by Mitsui Cytec Co., Ltd., Akofloc A130) are mixed and coagulated for wastewater treatment. Agent 2 was obtained.

  Using this flocculant 2, the car wash wastewater (average COD value 53 mg / L, average turbidity 13 NTU) was treated as described above using an A type coagulation sedimentation tank. Table 1 shows the COD removal rate after the treatment.

Example 3
Each component of 45% by weight of bentonite (manufactured by Hojun), 50% by weight of ferric sulfate (manufactured by Wako Pure Chemical Industries), and 5% by weight of nonionic polyacrylamide (manufactured by Mitsui Cytec Co., Ltd., Akofloc N100) is mixed and agglomerated for wastewater treatment. Agent 3 was obtained.

  Using this flocculant 3, the car wash wastewater (average COD value 71 mg / L, average turbidity 23 NTU) was treated as described above using an A type coagulation sedimentation tank. Table 1 shows the COD removal rate after the treatment.

Example 4
48% by mass of bentonite (manufactured by Hojun), 48% by mass of aluminum sulfate (manufactured by Wako Pure Chemical Industries), 2% by mass of sodium alginate (manufactured by Argitex L, Kimika), and 2% by mass of cationic polyacrylamide (Acoflock C486) Mixing to obtain a flocculant 4 for wastewater treatment Using this flocculant 4, the treatment of car wash wastewater (average COD value 81 mg / L, average turbidity 25 NTU) as described above using an A type coagulation sedimentation tank. went. Table 1 shows the COD removal rate after the treatment.

Example 5
Using the flocculant 4 used in Example 4, a B-type flocculent sedimentation tank was used to treat car wash wastewater (average COD value 68 mg / L, average turbidity 17 NTU). Table 1 shows the COD removal rate after the treatment.

Example 6
Using the flocculant 4 used in Example 4, a C-type coagulation sedimentation tank was used to treat car wash wastewater (COD value 72 mg / L, turbidity 19 NTU). Table 1 shows the COD removal rate after the treatment.

Comparative Example 1
Each component of 90% by mass of aluminum sulfate (manufactured by Asada Chemical Co., Ltd.) and 10% by mass of cationic polyacrylamide (Akofloc C486) was mixed to obtain flocculant 5 for wastewater treatment.

  Using this flocculating agent 5, car wash wastewater (COD value 76 mg / L, turbidity 17 NTU) was treated as described above using an A type coagulation sedimentation tank. Table 1 shows the COD removal rate after the treatment.

Comparative Example 2
Each component of 10% by mass of aluminum sulfate (manufactured by Asada Chemical Co., Ltd.) and 90% by mass of cationic polyacrylamide (Acofloc C486) was mixed to obtain flocculant 6 for wastewater treatment.

  Using this flocculant 6, the car waste water (COD value 73 mg / L, turbidity 20 NTU) was treated as described above using an A type coagulation sedimentation tank. Table 1 shows the COD removal rate after the treatment. Moreover, the sedimentation speed in the waste water at the above-mentioned coagulant addition amount of 100 mg / L was 0.2 cm / min.

Comparative Example 3
Using the flocculant 4 used in Example 4, using a type A coagulation sedimentation tank, the treatment amount was 9.6 m ³ / Hr, and the car wash wastewater (COD value 69 mg / L, turbidity 18 NTU) as described above. Was processed. Table 1 shows the COD removal rate after the treatment.

  As is apparent from Table 1, a comparatively high COD removal rate was obtained by comparing the Examples 1 to 4 and Comparative Examples 1 and 2 when the sedimentation rate of the aggregated floc was 0.3 to 3.0 cm / min. It was.

From the comparison of Examples 4 to 6 and Comparative Example 3, the flocculant of the present invention is represented by V ₁₅ / F, and the stirring part liquid average residence time represented by V ₁ / F is represented by V ₂ / F. By treating the waste water at a treatment amount F (m ³ / Hr) such that the sedimentation part liquid average residence time is 10 to 30 minutes and the water area load represented by F / A is 1 to 10 m / Hr, A relatively high COD removal rate was obtained.

In Example 5, a B type coagulation sedimentation tank is used, and in Comparative Examples 1 and 2, an A type coagulation sedimentation tank is used. However, since the capacity of the A type coagulation sedimentation tank is larger, By using the flocculant, it is possible to increase the processing capacity and further reduce the size of the coagulation sedimentation tank.

Claims (4)

A flocculant for removing COD components in wastewater, which was added at a concentration of 100 mg / L to wastewater having a COD concentration of 30 to 300 mg / L, stirred for 10 minutes, and then allowed to settle. A coagulant for wastewater treatment selected from the following Formulation Examples 1 to 3, wherein the settling rate of the aggregated floc is 0.3 to 3.0 cm / min.
(1) Formulation Example 1
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Cationic polyacrylamide 1-8% by mass
(2) Formulation example 2
Bentonite (montmorillonite) 30-60% by mass
Ferric sulfate 40-60% by mass
Cationic, anionic or nonionic polyacrylamide 1-10% by mass
(3) Formulation Example 3
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Sodium alginate 1-5% by mass
Cationic polyacrylamide 1-5% by mass A flocculant for wastewater treatment selected from the following formulation examples 1 to 3, wherein the tank capacity of the stirring part is V ₁ (m ³ ), the tank capacity of the precipitation part is V ₂ (m ³ ), and the sedimentation area of the precipitation part is A flocculant for wastewater treatment, which is treated so as to satisfy the following requirements (a) to (e) when the coagulation sedimentation treatment is performed in the coagulation sedimentation tank which is A (m ² ).
(1) Formulation Example 1
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Cationic polyacrylamide 1-8% by mass
(2) Formulation example 2
Bentonite (montmorillonite) 30-60% by mass
Ferric sulfate 40-60% by mass
Cationic, anionic or nonionic polyacrylamide 1-10% by mass
(3) Formulation Example 3
Bentonite (montmorillonite) 30-60% by mass
Aluminum sulfate 40-60 mass%
Sodium alginate 1-5% by mass
Cationic polyacrylamide 1-5% by mass
(A) It adds to a stirring part with the density | concentration of 20-200 mg / L with respect to waste_water | drain;
(B) Process with a processing amount F (m ³ / Hr);
_(C) agitating section water mean residence time expressed in _V 1 / F is 5 to 15 min;
_{(D) V} precipitates section average residence time represented by 2 / F is 10 to 30 minutes;
(E) The water area load represented by F / A is 1 to 10 m / Hr; Tank capacity V of the stirring section ₁ (M ³ ), Tank capacity V of sedimentation part ₂ (M ³ ) And sedimentation area A (m ² )But,
Tank capacity (V ₁ ) Is 0.4m ³ , Tank capacity (V ₂ ) Is 0.6m ³ The sedimentation area (A) of the sedimentation part is 0.5m ² ,
Tank capacity (V ₁ ) Is 0.3m ³ , Tank capacity (V ₂ ) Is 0.5m ³ The sedimentation area (A) of the sedimentation part is 0.3 m ² ,as well as
Tank capacity (V ₁ ) Is 0.5m ³ , Tank capacity (V ₂ ) Is 0.7m ³ The sedimentation area (A) of the sedimentation part is 1.0 m ² The flocculant for wastewater treatment according to claim 2, which is selected from any combination of the following. Wastewater treatment flocculant according to any one of claims 1 to 3 wastewater is wash effluent.