JP2016112515A - Method and apparatus for treating waste water containing coliform bacterium - Google Patents

Abstract

An object of the present invention is to provide a method for treating wastewater containing Escherichia coli that has a reduced impact on the environment and is a treatment method in which installation costs and operation costs are suppressed. The present invention includes, in order, a step of adding a cationic flocculant to a coliform group-containing wastewater containing fibers and a step of adding an anionic flocculant to obtain a flocculant-containing wastewater. Includes flocs having a floc diameter of 0.5 to 10 mm, and the ratio of the total projected area of the flocs of 0.5 to 10 mm is 70% or more with respect to the total projected area of all the flocs. It is related with the processing method of the coliform group containing waste_water | drain characterized by the turbidity of the treated water which removed the floc from 0-30 degree | times. [Selection] Figure 2

Description

  The present invention relates to a treatment method for coliform group-containing wastewater and a treatment apparatus for coliform group-containing wastewater. Specifically, the present invention is a method for reducing the number of coliforms in factory effluent without using chlorinated chemicals, etc., and a method for treating wastewater containing coliforms with little influence on the external environment and coliforms containing The present invention relates to a wastewater treatment device.

  The number of coliforms in wastewater discharged from factories is stipulated by the Water Pollution Control Law, and the daily average is obliged to be below 3000 / ml. On the other hand, each company with drainage performs various treatments to meet the regulation value.

  For removing coliform bacteria and preventing their occurrence, conventional methods include the use of osmotic membranes and the addition of chlorinated chemicals. For example, in a method using an osmotic membrane, the coliform group can be physically removed by using a membrane having a smaller diameter than bacteria including the coliform group. In addition, in the method of adding a chlorinated chemical, sterilization is performed by adding sodium hypochlorite (also known as hypo) used for sterilization of waterworks in the vicinity of the outlet from the factory.

  In addition, various new wastewater treatment technologies have been proposed to meet the needs of industry. For example, Patent Document 1 discloses a method of killing Escherichia coli and the like by generating microbubbles in a liquid containing E. coli or a virus and bringing them into contact or proximity. Patent Document 2 discloses a method for decomposing organic substances, E. coli, and bacteria by electrolytic treatment. Furthermore, Patent Document 3 discloses a method of concentrating sunlight and increasing infrared and ultraviolet density to sterilize or kill algae.

  In addition, the Water Pollution Control Law has standards for drainage in addition to coliforms. For example, the suspended matter amount (SS) is provided with a standard of an allowable limit of 200 mg / L and a daily average of 150 mg / L. As a method for removing SS from waste water, a method of adding a flocculant to raw water and precipitating (coagulating precipitation) is well known. Aggregation precipitation is performed for the purpose of removing the SS component, but it is estimated that the coliform group can be removed to some extent simultaneously. However, there is no significant correlation between the number of coliforms and the SS concentration (Non-patent Document 1), and the aggregation and precipitation treatment is performed exclusively for the removal of SS and the like.

JP 2011-115326 A JP 07-024468 A JP 2000-024655 A

"Correlation between the number of coliforms and chemical analysis items in factory / business site wastewater" (Shiga Prefectural Lake Biwa Environmental Science Research Center (2004))

As described above, it is considered that there is a certain effect in reducing coliform bacteria by using a method using an osmotic membrane or a method of adding a chlorinated chemical. However, the method using an osmotic membrane has a problem that the osmotic membrane is immediately blocked depending on the properties of the drainage. Furthermore, the method using the osmosis membrane has a problem that the installation cost and the operation cost are high, and such a method is limited to applications such as highly treating and reusing water.
In addition, the method of adding a chlorinated chemical also has a problem that the operating cost increases depending on the amount of addition. In addition, when the amount of chlorinated chemicals is increased, there is a problem that chlorine odor is generated in rivers and seas, which may affect the ecosystem of existing organisms.

  Moreover, the number of coliforms can also be reduced by using methods such as those disclosed in Patent Documents 1 to 3. However, in the installation in a drainage factory where the amount of wastewater per day reaches several thousand to several tens of thousands of rice, the scale of the equipment, the residence time, or the reaction time is not sufficient and it is impossible to apply. Moreover, when employ | adopting the method as disclosed by patent documents 1-3, it was necessary to introduce expensive equipment and there existed a subject also on the cost side.

Although various techniques have been developed to remove coliform bacteria from wastewater as described above, the actual situation is that chlorine-based chemicals are still generally used. Investigations have also been conducted on the relationship between the number of coliforms and various factors, but no clear results have been obtained for reducing the number of coliforms.
In order to solve the problems of the prior art, the present inventors provide a treatment method with reduced installation costs and operation costs, and a treatment method for coliform group-containing wastewater that has little environmental impact. We proceeded with the study for the purpose of doing this. That is, the present inventors proceeded with studies for the purpose of providing a treatment method for removing coliform bacteria from coliform bacteria-containing wastewater without using chlorinated chemicals or the like.

As a result of intensive studies to solve the above problems, the present inventors added a cationic flocculant and an anionic flocculant in a specific order to the coliform group-containing wastewater containing fibers, and further aggregated We found that coliforms can be removed from wastewater containing coliforms without using chlorinated chemicals, etc., by controlling the diameter of flocs generated after the addition of the agent and the turbidity of the treated water within the prescribed ranges. . The present inventors have found that by adopting such a method, the load on the environment can be greatly reduced, and the present invention has been completed.
Specifically, the present invention has the following configuration.

[1] A step of adding a cationic flocculant to a coliform group-containing wastewater containing fibers and a step of adding an anionic flocculant to obtain a flocculant-containing wastewater, the flocculant-containing wastewater having a floc diameter The ratio of the total projected area of 0.5 to 10 mm flocs including flocs of 0.5 to 10 mm is 70% or more with respect to the total projected area of all flocs, and the flocs were removed from the flocculant-containing waste water A method for treating coliform group-containing wastewater, wherein the turbidity of treated water is 0 to 30 degrees.
[2] The treatment method for coliform group-containing wastewater according to [1], wherein the cationic flocculant is added to the coliform group-containing wastewater so as to be 60 to 6000 mg / L in the step of adding the cationic flocculant.
[3] The method for treating coliform group-containing wastewater according to [1] or [2], wherein the cationic flocculant is an inorganic aluminum flocculant.
[4] In the step of adding a cationic flocculant, the inorganic aluminum flocculant is added to the coliform bacteria-containing wastewater so as to be 5 to 600 mg / L in terms of alumina. Method.
[5] In the step of obtaining the flocculant-containing wastewater, any one of [1] to [4], wherein the anionic flocculant is added to the coliform group-containing wastewater so that the solid content addition rate is 0.6 to 5 mg / L. A method for treating wastewater containing coliforms according to 1.
[6] The method for treating E. coli group-containing wastewater according to any one of [1] to [5], wherein the turbidity of treated water obtained by removing floc from the flocculant-containing wastewater is 0 to 10 degrees.
[7] In the step of adding a cationic flocculant, primary floc having an average floc diameter of 0.01 to 0.1 mm is formed. The coliform group-containing wastewater according to any one of [1] to [6] Processing method.
[8] The step of adding the cationic flocculant and the step of obtaining the flocculant-containing waste water each have a stirring step, and the stirring flow rate (m / min) in the step of adding the cationic flocculant is P. When the stirring flow rate (m / min) in the step of obtaining the wastewater is Q, 0.2 ≦ Q / P ≦ 0.7, the coliform group-containing wastewater according to any one of [1] to [7] Processing method.
[9] The method for treating E. coli group-containing wastewater according to any one of [1] to [8], further comprising a step of removing floc from the flocculant-containing wastewater.
[10] The method for treating coliform group-containing wastewater according to any one of [1] to [9], wherein the number of coliforms contained in the treated water from which floc has been removed from the flocculant-containing wastewater is 1000 / mL or less.
[11] The method for treating E. coli group-containing wastewater according to any one of [1] to [10], wherein the coliform group-containing wastewater is paper mill wastewater.
[12] A means for adding a cationic flocculant to a coliform group-containing wastewater containing fibers, and a means for adding an anionic flocculant after adding the cationic flocculant to obtain a flocculant-containing wastewater. The ratio of the total projected area of 0.5 to 10 mm flocs contained in the contained wastewater is 70% or more with respect to the total projected area of all flocs, and the turbidity of treated water from which flocs have been removed from the flocculant-containing wastewater A device for treating wastewater containing coliform bacteria that can be 0 to 30 degrees.
[13] The treatment apparatus for coliform group-containing wastewater according to [12], wherein the means for adding the cationic flocculant is means for adding the cationic flocculant to the coliform group-containing wastewater so as to be 60 to 6000 mg / L. .
[14] The means for adding the cationic flocculant is a means for adding the inorganic aluminum flocculant to the E. coli group-containing waste water so as to be 5 to 600 mg / L in terms of alumina, as described in [12] or [13]. E. coli group-containing wastewater treatment equipment.
[15] The means for obtaining the flocculant-containing wastewater is means for adding an anionic flocculant to the coliform group-containing wastewater so that the solid content addition rate is 0.6 to 5 mg / L. [12] to [14] An apparatus for treating wastewater containing coliforms according to any one of the above.
[16] The means for adding the cationic flocculant is capable of forming primary flocs having an average floc diameter of 0.01 to 0.1 mm. The coliform group-containing wastewater according to any one of [12] to [15] Processing equipment.
[17] The means for adding the cationic flocculant and the means for obtaining the flocculant-containing waste water each have a stirring means, and the stirring flow rate (m / min) in the means for adding the cationic flocculant is P, and the flocculant When the stirring flow rate (m / min) in the means for obtaining the contained wastewater is Q, the coliform group-containing wastewater according to any one of [12] to [16], wherein 0.2 ≦ Q / P ≦ 0.7. Processing equipment.
[18] The apparatus for treating coliform group-containing wastewater according to any one of [12] to [17], further comprising means for removing flocs from the flocculant-containing wastewater.

  According to the present invention, a large amount of coliform group-containing wastewater can be treated without installing expensive equipment or the like, and the number of coliform groups contained in the wastewater can be greatly reduced. In addition, the use of chlorinated chemicals that may affect the environment can be avoided, and the impact on aquatic ecology can be reduced.

FIG. 1 is a schematic view illustrating the structure of a sedimentation tank used in the treatment method of the present invention. FIG. 2 is a schematic diagram of an example of a processing apparatus used in the processing method of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Method of treating wastewater containing coliforms)
The present invention relates to a method for treating coliform group-containing wastewater, which comprises a step of adding a cationic flocculant to a coliform group-containing wastewater containing fibers and a step of adding an anionic flocculant to obtain a flocculant-containing wastewater. Here, the flocculant-containing wastewater obtained by adding the anionic flocculant contains flocs having a floc diameter of 0.5 to 10 mm, and the proportion of the total projected area of the flocs of 0.5 to 10 mm The turbidity of treated water from which floc is removed from the flocculant-containing wastewater is 0 to 30 degrees. As described above, in the present invention, by adding each flocculant in a specific order and controlling the floc diameter generated after the flocculant addition and the turbidity of the treated water within a predetermined range, chlorine-based chemicals, etc. The coliforms can be removed from the wastewater containing coliforms without using the. Such a method is a method that can significantly reduce the load on the environment, and further, the equipment cost and the operation cost are suppressed.

  In the present invention, a cationic flocculant and then an anionic flocculant are added to the coliform group-containing wastewater containing fibers. In the step of adding the cationic flocculant to the coliform group-containing wastewater, the cationic flocculant generates a relatively small micro floc (primary floc) containing the coliform group. The micro floc can then be grown to a larger floc by adding an anionic flocculant. The coliforms can be removed from the waste water by sedimentation and removal of the flocs thus generated.

(Flock diameter)
The floc formed after adding the anionic flocculant contains floc having a floc diameter of 0.5 to 10 mm, and the proportion of the total projected area of the floc having a diameter of 0.5 to 10 mm 70% or more with respect to the total projected area. The proportion of the total projected area of the flocs of 0.5 to 10 mm is preferably 80% or more, and more preferably 90% or more with respect to the total projected area of all the flocks.
Thus, in the present invention, the coliform group can be effectively removed by managing the total projected area of 0.5 to 10 mm floc formed after adding the anionic flocculant within the above range. It becomes possible. In addition, when the ratio of the total projected area of 0.5 to 10 mm flocs is less than 70%, sedimentation of suspended solids including coliforms deteriorates, and the coliforms are discharged outside the factory without being sufficiently removed. This is not preferable.

  In the present specification, a floc means a floc having a diameter of 0.1 mm or more. The present invention is characterized in that the ratio of the total projected area of flocs of 0.5 to 10 mm to the total projected area of all flocs having a floc diameter of 0.1 mm or more is 70% or more.

Strictly speaking, the floc formed after the addition of the anionic flocculant is not spherical, and the projection surface of the floc is often not a perfect circle. For this reason, in the present invention, the floc diameter is defined as the projected area circle equivalent diameter. Specifically, the floc diameter and the total projected area calculated as the projected area equivalent circle diameter can be calculated by the following procedure.
(1) A predetermined amount of flocculant-containing wastewater (for example, 100 ml) is arbitrarily measured, and the projected area (A) of all flocs present in the predetermined amount is calculated.
(2) Calculate the projected area circle equivalent diameter of each flock from each projected area.
(3) Calculate the total projected area (B) of flocs having a projected area equivalent circle diameter of 0.5 to 10 mm.
(4) The ratio (%) of the total projected area of 0.5 to 10 mm floc is calculated using the following formula.
Ratio (%) of total projected area of floc of 0.5 to 10 mm = B / A × 100
Note that the projected area of the flock can be calculated using an image analysis apparatus (DIP200, manufactured by Oji Scientific Instruments).

  In the present invention, the total projected area of flocs may be the total of the projected areas measured by the image analysis apparatus, or may be a value obtained by calculating the area from the projected area circle equivalent diameter and adding the areas. If there is no image analysis device, the total projected area of flocs may be obtained by using, for example, a contaminant measurement chart or a dot gauge according to the method described in JIS.

(Turbidity)
In this invention, the turbidity of the treated water which removed the floc from the flocculant containing waste water is 0-30 degree | times. The turbidity is preferably 0 to 20 degrees, more preferably 0 to 15 degrees, and still more preferably 0 to 10 degrees. The treated water is a solution obtained by removing flocs from the flocculant-containing wastewater, and is a supernatant obtained by performing natural sedimentation separation for 5 minutes after adding an anionic flocculant and stirring. The treated water is obtained by removing flocs, but substantially contains fine flocs that do not settle even after 5 minutes of natural sedimentation separation. In the present invention, those containing such fine flocs are included. Is also called treated water (supernatant). Moreover, in this specification, the treated water used for the measurement of turbidity is one that is naturally settled and separated for 5 minutes after stirring, and the treated water is collected at a point 20% of the water depth from the water surface.
Turbidity is mainly caused by fine flocs and colloidal substances floating in the waste water, and examples include those in which Escherichia coli group adheres to a cationic flocculant. For this reason, by controlling the turbidity to be within the above range, it is possible to effectively remove the coliform group.

  As a method for measuring turbidity, it is preferable to employ a method of measuring the transmitted light intensity of treated water. Specifically, the turbidity can be calculated by measuring the transmitted light intensity in the vicinity of a wavelength of 660 nm using TCR-5Z manufactured by Kasahara Chemical Industries. In addition, as said measuring instrument, when said apparatus is not available or a measurement is impossible, TD-M500 by an OPTEC company can be employ | adopted. In this invention, the turbidity of treated water can be calculated | required from the relational expression of the transmitted light intensity of a polystyrene turbidity standard liquid, and turbidity (concentration).

(Collagenous wastewater)
Coliform group-containing wastewater contains fiber. Here, the fibers contained in the coliform group-containing wastewater are fiber-shaped substances such as pulp. For this reason, the coliform group-containing wastewater is preferably paper mill wastewater. Since pulp-derived fibers are contained in paper mill wastewater, the treatment method of the present invention is preferably applicable. The content of the fiber contained in the paper mill wastewater is preferably 0.0005 to 0.1 mass%, more preferably 0.001 to 0.05 mass%, based on the total mass of the paper mill wastewater. preferable.

  The fiber contained in the coliform group-containing wastewater is preferably a fiber derived from wood pulp, and is preferably a fiber having a length weighted average value of 0.05 to 1 mm. Moreover, it is preferable that the fiber derived from a wood pulp is a fibrillated fiber (a fluffed fiber).

  When the coliform group-containing wastewater is wastewater other than paper mill wastewater or wastewater that does not contain fibers, it is preferable to add fibers before adding the cationic flocculant. As the fiber to be added, it is preferable to select one or a mixture of wood, herbaceous, or petrochemical-derived fibers. Moreover, it is preferable that the fiber to add is what charged the anion. For example, the coliform group is considered to be negatively charged because it is a microorganism. Part of the fungi are physically adsorbed on the fiber, and the rest are formed into primary flocs with a cationic flocculant and charge-coupled with the fiber, and are thought to be coarsened with an anionic flocculant to promote sedimentation. Yes.

  The length of the fiber to be added is preferably 0.05 to 1 mm in terms of a weighted average value. By setting the fiber length in the above range, the ratio of the total projected area of 0.5 to 10 mm floc formed after the addition of the anionic flocculant can be within a desired range, and the floc sedimentation can be achieved. Can be increased. Moreover, it can prevent that fiber itself floats and mixes in a treated water by making fiber length into the said range.

  When adding fibers to the coliform group-containing wastewater, the amount of fibers added is preferably 0.0005 to 0.1 mass% with respect to the total mass of the coliform group-containing wastewater. In addition, when coliform group containing waste_water | drain contains a fiber, it is preferable that the total mass of the fiber previously contained and the fiber to add becomes in the said range. When the coliform group-containing wastewater contains fibers within the above range, flocs having a desired size can be formed, and the coliform group can be efficiently removed.

(Cationic flocculant)
Cationic flocculants are positively charged and have the ability to collect negatively charged substances. As the cationic flocculant, an organic cationic flocculant or an inorganic cationic flocculant can be used. Among these, an inorganic cationic flocculant is preferably used, and an inorganic aluminum flocculant is more preferably used. Examples of the cationic flocculant preferably used in the present invention include sulfate band (aluminum sulfate), PAC (polyaluminum chloride), aluminum chloride, polyferric sulfate, ferrous sulfate and the like. Such a cationic flocculant is preferably used because it has a positively charged metal ion such as aluminum or iron.
Moreover, when using an organic cationic aggregating agent as the cationic aggregating agent, an aggregating agent having a molecular weight of about 100,000 to 400,000 can be preferably used. The organic cationic flocculant is also preferably used in combination with an inorganic cationic flocculant.

  The addition amount of the cationic flocculant is preferably adjusted as appropriate according to the properties of the wastewater such as SS (floating matter), COD (chemical oxygen demand), and turbidity. For example, in the step of adding the cationic flocculant, it is preferable to add the cationic flocculant to the coliform group-containing wastewater so as to be 60 to 6000 mg / L. Further, the cationic flocculant is preferably added so as to be 70 to 1000 mg / L, and more preferably added so as to be 100 to 400 mg / L. In addition, when using an organic cationic flocculant as a cationic flocculant, it is more preferable that the addition amount of an organic cationic flocculant is 60-300 mg / L. By making the addition amount of the cationic flocculant within the above range, the contact probability with the anionic flocculant added in the subsequent process can be increased, and a floc having excellent sedimentation properties is formed after the addition of the anionic flocculant. can do. Thereby, it becomes possible to remove coliform bacteria effectively.

  In the step of adding a cationic flocculant, it is preferable to use an inorganic aluminum flocculant. In this case, the inorganic aluminum flocculant is added to the coliform group-containing waste water so as to be 5 to 600 mg / L in terms of alumina. Is preferred. The addition amount of the inorganic aluminum-based flocculant is more preferably 5 to 100 mg / L, and further preferably 8 to 40 mg / L in terms of alumina. By setting the addition amount of the inorganic aluminum-based flocculant within the above range, flocs having excellent sedimentation properties can be formed after the addition of the anionic flocculant. Thereby, it becomes possible to remove coliform bacteria effectively.

  By adding a cationic flocculant, a relatively small micro floc (primary floc) containing coliforms is formed. In order to form a primary floc, it is preferable to provide a reaction time of 30 seconds to 5 minutes with rapid stirring after the addition of the cationic flocculant. Specifically, it is preferable to continue stirring for 30 seconds to 5 minutes. By providing the reaction time, a primary floc can be formed, and the residual colloidal substance including coliforms can be reduced. It should be noted that there is no problem if the reaction time exceeds 5 minutes, but if the reaction time exceeds this, the equipment such as piping becomes long, which is economically disadvantageous.

  After the cationic flocculant is added, it is preferable to continue strong stirring for 30 seconds to 5 minutes, and the stirring conditions are preferably 120 to 150 rpm, and preferably 30 to 40 m / min at a flow rate.

  The average floc diameter of the primary floc formed by adding the cationic flocculant is preferably 0.001 mm or more and less than 0.1 mm, and more preferably 0.01 mm or more and less than 0.1 mm. By controlling the average floc diameter of the primary flocs to be in the above range, it becomes easy to form flocs having a desired size when an anionic flocculant is added in the subsequent step. Thereby, coliform bacteria can be effectively removed.

(Anionic flocculant)
Anionic flocculants are negatively charged and have the ability to collect positively charged substances. The anionic flocculant is preferably a polymeric anionic flocculant. The polymer anionic flocculant is preferably selected from polymer flocculants having a molecular weight of 800 to 25 million in consideration of compatibility with the cationic flocculant in the previous step. The anionic flocculant is preferably a polyacrylamide flocculant, and specific examples include a copolymer (PAM) of acrylamide and an ionic monomer.

  Anionic flocculants having an anionic degree of weak to moderate anionic degree are often used. In many cases, the anionic flocculant is diluted and adjusted in advance and added to the waste water. Since the concentration adjustment is a polymer, the optimum reactivity and reaction time differ depending on the concentration and viscosity, but generally diluted to 0.01 to 0.1% by mass is used. By adjusting the concentration of the anionic flocculant within the above range, dispersibility and handling properties can be improved.

  The addition amount of the anionic flocculant is preferably selected so that the primary floc produced in the previous step does not remain as an unreacted product. Specifically, the anionic flocculant is preferably added so that the solid content addition rate per wastewater is 0.6 to 5 mg / L, and more preferably 1 to 3 mg / L. preferable. By setting the solid content addition rate per drainage of the anionic flocculant within the above range, the primary floc can be sufficiently captured and flocs having a desired size can be formed. Thereby, it becomes possible to remove coliform bacteria effectively. An anionic flocculant is not problematic even if it is added in excess of the above-mentioned upper limit value, but it is economically disadvantageous because an unreacted anionic flocculant remains.

  By adding an anionic flocculant, the primary floc grows into a floc of a predetermined size. In order to form a floc having a predetermined size, it is preferable to provide a reaction time of 30 seconds to 20 minutes after the addition of the anionic flocculant. Moreover, after adding an anionic flocculant, it is preferable to perform weak stirring. Specifically, after adding the anionic flocculant, it is preferable to stir at 30 to 60 rpm and 8 to 16 m / min in terms of flow rate.

When an anionic flocculant is added, the anionic flocculant is preferably added to the flocculation core provided at the center of the settling tank. FIG. 1 shows a sedimentation tank 10 preferably used in the present invention and a flocculation core 30 provided at the center of the sedimentation tank 10. FIG. 1B is a plan view of the sedimentation tank 10 as shown in FIG. As shown in FIG. 1B, the sedimentation tank 10 has a flocculation core 30 at the center. The inside of the flocculation core 30 is divided into 8 to 12 spaces, and the water flow sequentially flows up and down in the divided spaces. In the flocculation core 30, the wastewater that has reached the final space is discharged radially (360 ° direction) toward the upper part of the settling tank so that the water flow is upward.
FIG.1 (c) is the image figure which expanded a part of the flocculation core 30 shown by FIG.1 (b) planarly, and was seen from the side surface. FIG. 1 (c) shows the structure of the divided space and the flow of drainage. In addition, the spaces A to D in FIG. 1B correspond to the spaces A to D in FIG.
The anionic flocculant is preferably added from the upper part of the downward space. For example, in FIG.1 (c), adding in the space B or D is preferable. Moreover, it is preferable to add the space which adds an anionic flocculant in consideration of the distance to an exit. For example, when an anionic flocculant having a slow reaction is added, it is preferable to add it to a space close to the coliform group-containing drainage inlet 32 (a space far from the outlet) and downward. The anionic flocculant may be added to two or more different spaces. Thus, by adjusting the space to which the anionic flocculant is added, it becomes easy to form flocs having a uniform size.

  Although not shown, an anionic flocculant may be added in a stirring tank separate from the settling tank. In this case, it is preferable to provide a growth tank or a sedimentation tank downstream of the stirring tank. As described above, the step of adding flocs after adding the anionic flocculant may be a multi-stage configuration.

  When the stirring flow rate (m / min) in the step of adding the cationic flocculant is P and the stirring flow rate (m / min) in the step of obtaining the anionic flocculant-containing waste water is Q, 0.2 ≦ Q /P≦0.7 is preferable, and 0.3 ≦ Q / P ≦ 0.5 is more preferable. The stirring flow rate is calculated from the amount of water passing through a known volume that is a pipe and a tank. By setting the condition of Q / P within the above range, it is possible to prevent the grown flocs from being broken and to improve the sedimentation property. In addition, by setting the Q / P condition within the above range, the anionic flocculant can be uniformly dispersed, so that the primary floc and the like can be prevented from remaining, and the turbidity can be reduced. .

  In the step of adding the anionic flocculant to obtain the flocculant-containing wastewater, the water temperature of the flocculant-containing wastewater is preferably 10 ° C. or higher, and more preferably 15 to 45 ° C. By setting the water temperature in the above range, it is possible to easily form a floc having a predetermined size.

(PH adjustment step)
In the present invention, a pH adjustment step may be provided between the step of adding the cationic flocculant and the step of adding the anionic flocculant to obtain the flocculant-containing waste water. In the step of adding a cationic flocculant, when a sulfuric acid band is added, the pH decreases as the amount added increases, which may inhibit the aggregation of the anionic flocculant added later. In such a case, it is preferable to adjust to an optimum pH (preferably pH 5 to 8, more preferably pH 6 to 7) by adding an alkaline chemical. Thereby, the anionic flocculant can improve the cohesiveness and can maintain a favorable effect.

As the pH adjuster, sodium hydroxide, potassium hydroxide and the like are preferably used.
In addition, when calcium powder such as calcium carbonate or lime is used as a pH adjuster and added alone, a settling tank that maintains a long residence time will also contribute to the removal of coliform bacteria. Can be expected. However, since it takes time to settle, the final wastewater may become cloudy, which may not be suitable on an industrial scale with a large amount of wastewater.

(Flock removal process)
In this invention, it is preferable to further include the process of removing a floc from flocculent containing waste water. In the step of removing flocs from the flocculant-containing wastewater, it is preferable to remove the flocs by natural sedimentation separation after adding an anionic flocculant and allowing a reaction time of 30 seconds to 20 minutes.
In the step of removing flocs, in addition to the natural sedimentation separation method, for example, the flocs may be separated and removed using a centrifugal separation method or a pressure flotation method. In the pressure flotation method, flocs can be removed by putting fine air that has been compressed into flocculant-containing wastewater and allowing the flocs to float on the water surface. The pressure levitation method is an effective method for removing flocs having a relatively small floc diameter.

When flocs are allowed to settle by natural sedimentation separation, the flocs are preferably allowed to stand for a period of time during which the supernatant and floc are separated. Specifically, it is preferable to set the settling time (standing time) to 1 to 3 hours. By setting the settling time within the above range, it is possible to sink turbulent flow and settling even a relatively small floc. In addition, by setting the sedimentation time within the above range, it is possible to suppress the proliferation of coliform bacteria staying in the supernatant. The settling time is a preferable settling time in a settling tank having a basic agglomeration settling tank structure (for example, Z-2 type manufactured by Ebara Infilco). In a sedimentation tank having a high-speed agglomeration sedimentation system (for example, a Sumicener manufactured by Sumitomo Heavy Industries Environment Co., Ltd.), the sedimentation time can be shortened. In addition, a high speed coagulation sedimentation system means the system which raised the processing amount per volume. For example, in a system in which wastewater containing flocs is discharged downward from about 1/3 to half of the depth of the sedimentation tank, and clear water is discharged from the top, flocs arrive early by the short distance. Therefore, it is possible to reduce the installation volume of the equipment.
It is also effective to provide an inclined plate (rectifying plate) in the sedimentation tank to prevent the floc from rising again due to turbulent flow.

  When the floc is settled by natural sedimentation separation, the sedimentation speed of the floc may be increased by mixing sandy substances into the floc. Specifically, the sandy substance can be mixed into the floc by mixing the sandy substance with the flocculant-containing waste water. Such a method is referred to as an ultrafast sedimentation system.

(Number of coliforms in treated water)
In the present invention, after an anionic flocculant is added to obtain flocculant-containing wastewater, treated water can be obtained by removing flocs from the flocculant-containing wastewater. In the present invention, the number of coliform bacteria contained in the treated water is preferably 3000 cells / mL or less, more preferably 2000 cells / mL or less, even more preferably 1000 cells / mL or less, It is particularly preferred that the number is not more than pieces / mL.
Here, the coliform group includes not only E. coli but also various bacteria. The coliforms targeted for removal in the present invention are E. coli that can be counted by performing a test in accordance with JIS K0350-20-10 (2001) “Test method for coliforms in water and wastewater” and other counts. Refers to bacteria.

  The number of coliforms contained in waste water (treated water) discharged from factories and the like is regulated by the Water Pollution Control Law, and the daily average is set to 3000 or less. If the treated water is sufficiently equipped with nutrients, etc. necessary for the growth of coliforms, E.coli grows in the middle of the drainage route and exceeds the standard value even if the standards are met at the factory exit. There is a possibility. For this reason, it is preferable that the number of coliforms is 1000 / mL or less from the viewpoint of providing a margin for the reference value. It is also preferable to reduce the eutrophic content in the treated water.

  The number of coliforms in the treated water can be measured by a method for measuring the number of coliforms using deoxycholate agar medium. Specifically, 1 ml of a diluted sample of treated water was put in a disposable sterilized petri dish, and then 15 ml of deoxycholate agar medium which had been heated to dissolve at a specified concentration and then cooled to close to 50 ° C. was put first. Add while shaking to ensure uniform drainage. The mixture is allowed to cool, and after the deoxycholate agar medium has solidified, 10 ml of the aforementioned medium is added again and overlaid to solidify. Then, it culture | cultivates for 18-20 hours at 36 +/- 1 degreeC, and the number in 1 ml of samples can be computed by counting the number of the colonies of the red color formed on the culture medium. The sample is diluted so that the number of colonies to be counted is obtained in the range of 20 to 200 after the culture, and the value obtained by multiplying the count value after the culture by the dilution factor is defined as the number of coliforms. In order to reduce the error due to measurement, it is preferable to culture five cells having the same dilution rate and use the average value of the counts.

  In the present invention, the E. coli group in the treated water can be suppressed to the above range by performing the treatment as described above. In the present invention, it is preferable to remove 90% or more coliforms by performing the above treatment, more preferably to remove 95% or more coliforms, and to remove 99% or more coliforms. Further preferred. Thus, by using the treatment method of the present invention, the coliform group can be removed with an extremely high removal rate.

(Reuse of treated water)
By using the treatment method of the present invention, coliforms can be removed with a very high removal rate. For this reason, the treated water obtained by using the treatment method of the present invention does not cause environmental pollution or the like even when discharged into a river or the sea.

(Treatment device for coliform group-containing wastewater)
The present invention includes a coliform group comprising means for adding a cationic flocculant to a coliform group-containing wastewater containing fibers, and means for adding an anionic flocculant after adding the cationic flocculant to obtain a flocculant-containing wastewater. The present invention relates to a wastewater treatment apparatus. In the treatment apparatus of the present invention, the proportion of the total projected area of 0.5 to 10 mm flocs contained in the flocculant-containing wastewater is 70% or more with respect to the total projected area of all flocs, The turbidity of the treated water from which the floc has been removed can be 0 to 30 degrees.

FIG. 2 shows an example of the apparatus for treating wastewater containing coliforms of the present invention. As shown in FIG. 2, the apparatus for treating wastewater containing coliforms of the present invention has a sedimentation tank 10. The sedimentation tank 10 preferably includes a flocculation core 30. The interior of the flocculation core 30 is divided into 8 to 12 spaces, and the waste water is gently agitated by flowing the water flow up and down in order in the divided spaces. In the flocculation core 30, the wastewater that has reached the final space is discharged radially (360 ° direction) toward the upper part of the settling tank so that the water flow is upward.
As the settling tank 10, a known coagulation settling tank can be used. For example, a high-speed coagulation settling system such as a Z-2 type settling tank manufactured by EBARA Infilco or a Sumic Thickener manufactured by Sumitomo Heavy Industries Environment Co., Ltd. Can be suitably used.

  The coliform group-containing wastewater containing fibers is first stored in the raw water pit 20. In the raw water pit 20, a pH adjusting agent may be added to the coliform group-containing wastewater, and the raw water pit 20 may be a pH adjusting tank. The raw water pit 20 is preferably provided with a stirring system.

An in-line mixer 22 is preferably provided downstream of the raw water pit 20, and the raw water pit 20 and the in-line mixer 22 are preferably connected via a pump 21.
The cationic flocculant is preferably added in the in-line mixer 22 or in the pipe upstream of the in-line mixer 22. When the cationic flocculant is introduced into the pipe upstream of the in-line mixer 22, it can be added from an open part such as a distribution tank in the middle of the pipe, but it is preferable to press-fit into the pipe. The in-line mixer 22 is not particularly limited as long as it has a mechanism for causing turbulent flow and mixing. For example, only a part of the pipe may have a reduced diameter, or may be provided with a knob inside to generate turbulent flow. Using this turbulent flow, the cationic flocculant and the coliform-containing wastewater are mixed. In addition, the length of the in-line mixer 22 may be appropriately selected from the length that can be stirred in 30 seconds or more and 5 minutes or less.

  Although not shown, the treatment apparatus for coliform group-containing wastewater may have a stirring tank on the upstream side in addition to the sedimentation tank 10, and the cationic flocculant is added to such a stirring tank. May be. When the cationic flocculant is added to the stirring tank, strong stirring is preferably performed in the stirring tank, and specifically, stirring is preferably performed at a flow rate of 20 to 50 m / min. After stirring in the stirring tank, the coliform group-containing wastewater containing the cationic flocculant is sent to the sedimentation tank 10.

The cationic flocculant is preferably added to the coliform group-containing wastewater so as to be 60 to 6000 mg / L. The cationic flocculant is preferably added so as to be 70 to 1000 mg / L, and more preferably added so as to be 100 to 400 mg / L. In addition, when using an organic cationic flocculant as a cationic flocculant, it is more preferable that the addition amount of an organic cationic flocculant is 60-300 mg / L.
When an inorganic aluminum-based flocculant is used as the cationic flocculant, it is preferable to add the inorganic aluminum-based flocculant to the coliform group-containing wastewater so as to be 5 to 600 mg / L in terms of alumina. The addition amount of the inorganic aluminum-based flocculant is more preferably 5 to 100 mg / L, and further preferably 8 to 40 mg / L in terms of alumina.
In addition, when a cationic flocculant is thrown in in the piping upstream of the in-line mixer 22, it is preferable that the density | concentration after sending the liquid to the sedimentation tank 10 through the in-line mixer 22 is in the said range.

  The average floc diameter of the primary floc formed by adding the cationic flocculant is preferably 0.001 mm or more and less than 0.1 mm, and more preferably 0.01 mm or more and less than 0.1 mm. It is preferable to adjust the addition amount of the cationic flocculant so that the average floc diameter of the primary floc falls within the above range, and it is preferable to adjust the stirring speed of the in-line mixer 22 and the flocculation core 30.

  The coliform group-containing wastewater containing the cationic flocculant is sent to the sedimentation tank 10, but depending on the pH of the coliform group-containing wastewater containing the cationic flocculant, the space between the anion addition port and the cation addition port of the sedimentation tank 10 May be charged with a pH adjusting agent. The piping in front of the settling tank 10 may be equipped with a pH adjusting agent holding tank. When the pH of the coliform group-containing wastewater containing the cationic flocculant is 5 or less, a predetermined amount of alkaline chemical is added. It is preferable to add and adjust to an optimum pH (pH 6 to 7).

  The anionic flocculant is preferably added to the sedimentation tank 10. The anionic flocculant is preferably added to the coliform group-containing waste water so that the solid content addition rate is 0.6 to 5 mg / L, and more preferably 1 to 3 mg / L. . The anionic flocculant may be stored in an anionic flocculant holding tank provided in the settling tank 10, or an anionic flocculant may be charged from the anionic flocculant holding tank. The anionic flocculant holding tank has a mechanism for adjusting the addition amount according to the primary floc content of the coliform group-containing wastewater containing the cationic flocculant fed to the sedimentation tank 10. Is preferred.

  After adding the anionic flocculant, it is preferable to provide a reaction time of 30 seconds to 20 minutes. Moreover, after adding an anionic flocculant, it is preferable to perform weak stirring. Specifically, after adding the anionic flocculant, it is preferable to stir at 30 to 60 rpm and 8 to 16 m / min in terms of flow rate.

  After the anionic flocculant is added, it is preferable to gently stir using the flocculation core 30 or the like. Specifically, when the stirring flow rate (m / min) in the step of adding the cationic flocculant is P and the stirring flow rate (m / min) in the step of obtaining the flocculant-containing wastewater is Q, 0.2 ≦ Q / P ≦ 0.7 is preferable, and 0.3 ≦ Q / P ≦ 0.5 is more preferable. The stirring flow rate is calculated from the amount of water passing through a known volume that is a pipe and a tank. By setting the condition of Q / P within the above range, the grown floc is not broken and the sedimentation property can be improved. In addition, by setting the Q / P condition within the above range, the anionic flocculant can be uniformly dispersed, so that the primary floc and the like can be prevented from remaining, and the turbidity can be reduced. .

  In the apparatus for treating wastewater containing Escherichia coli group of the present invention, it is preferable to remove floc F by natural sedimentation separation after adding an anionic flocculant and allowing a reaction time of 30 seconds to 20 minutes. In addition, the processing apparatus of the coliform group containing waste_water | drain of this invention may be equipped with the centrifuge system and the pressurization flotation system, and you may isolate | separate and remove a floc using these systems.

  When flocs are allowed to settle by natural sedimentation separation, the flocs are preferably allowed to stand for a time during which the supernatant and floc can be separated. It is preferable to set the settling time (standing time) to 1 to 3 hours. By setting the sedimentation time within the above range, turbulence can be suppressed, and sedimentation can be achieved even with a relatively small floc. In order to suppress turbulent flow, it is also effective to provide an inclined plate (rectifying plate) in the sedimentation tank to prevent the floc from re-floating due to turbulent flow. In this case, the inclined plate (rectifying plate) is not arranged in the direction perpendicular to the placement surface, but can be prevented from rolling up the flock by being arranged so as to have an angle.

  It is preferable that the sedimentation tank 10 further includes means for removing flocs from the flocculant-containing waste water. Specifically, it is preferable to remove and remove sludge containing flocs from the bottom of the sedimentation tank 10. The sedimentation tank 10 preferably has a discharge port at the bottom, and the discharge port preferably has a triangular pyramid shape whose width decreases toward the bottom. A pipe and a pump may be connected to the discharge port, and the conveyance sludge of the pump may be extracted from the pipe using the conveyance force of the pump.

  Further, the treated water obtained by removing flocs from the flocculant-containing wastewater is collected as supernatant water and discharged through a pipe. The piping may be connected to a discharge port to a river or the sea, or may be connected to another storage tank or the like.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
Process water such as washing water after cooking kraft pulp and bleaching waste water was obtained at the factory and mixed according to the waste water ratio of the actual machine. This wastewater was treated with an oxygen-aerated activated sludge apparatus, and the supernatant was recovered to obtain coliform group-containing wastewater A. The BOD of the coliform group-containing wastewater A was 3 mg / L, COD was 52 mg / L, SS was 5.4 mg / L, and the number of coliform groups was 5700 / ml.

  1 liter of coliform group-containing wastewater A obtained above was set in a jar tester (MJS-6T, manufactured by Miyamoto Seisakusho Co., Ltd.) and pre-stirred at 120 rpm for about 1 minute. Next, PAC (manufactured by Showa Chemical Co., Ltd., polyaluminum chloride, 10% product in terms of alumina) was added as a cationic flocculant so as to be 2500 mg / L with respect to the weight of the waste water, and stirred at 120 rpm for 60 seconds. Thereafter, 1N (1N) aqueous sodium hydroxide solution was added to adjust the pH of the waste water to 6.5. While maintaining stirring at 120 rpm, PAM (manufactured by MT Aquapolymer, A-110H, medium anion degree, molecular weight 21 million) adjusted in advance to 0.06% was adjusted so that the solid content addition rate was 2 mg / L. Added quickly to the wastewater. Immediately after that, the number of revolutions was lowered to 60 rpm and stirring was performed for 60 seconds. After stirring for 60 seconds, the rotation of the jar tester was stopped and the diameter of the floc that settled was measured. The proportion of the total projected area of 0.5 to 10 mm flocs was 99.6%, the turbidity was 0.5 degrees, and the number of coliforms was 29 / ml (removal rate 99.5%).

(Example 2)
The same treatment as in Example 1 was performed except that the amount of PAC added was 5000 mg / L. The proportion of the total projected area of 0.5 to 10 mm flocs was 98.7%, the turbidity was 0.1 degree, and the number of coliforms was 24 / ml (removal rate 99.5%).

(Example 3)
The same treatment as in Example 1 was performed except that the addition amount of PAC was 400 mg / L, the addition amount of PAM was 1 mg / L in terms of solid content, and no sodium hydroxide aqueous solution was added. The proportion of the total projected area of flocs of 0.5 to 10 mm was 99.2%, the turbidity was 0.5 degrees, and the number of coliforms was 36 / ml (removal rate 99.4%).

(Comparative Example 1)
The same treatment as in Example 1 was performed except that the anionic flocculant, the cationic flocculant and the aqueous sodium hydroxide solution were not added to the coliform group-containing wastewater A used in Example 1. In Comparative Example 1, no suspended substances were observed, and the floc diameter could not be measured. The turbidity was 1.6 degrees, and the number of coliforms was 5700 / ml (removal rate 0%).

(Comparative Example 2)
The same treatment as in Example 1 was performed except that the cationic flocculant and the aqueous sodium hydroxide solution were not added to the coliform group-containing wastewater A used in Example 1. In Comparative Example 2, no suspended substances were observed, and the floc diameter could not be measured. The turbidity was 1.5 degrees, and the number of coliforms was 3900 / ml (removal rate 31.6%).

(Comparative Example 3)
The same treatment as in Example 1 was performed except that the anionic flocculant and the aqueous sodium hydroxide solution were not added to the coliform group-containing wastewater A used in Example 1. In Comparative Example 3, PAC-derived white turbidity (floc particles less than 0.5 mm) was observed. The proportion of the total projected area of 0.5 to 10 mm flocs was 20.5%, the turbidity was 14 degrees, and the number of coliforms was 3100 / ml (removal rate 45.6%).

(Measuring method)
(Coliform count)
After the addition of PAM, the mixture was stirred for 60 seconds, and then the rotation was stopped. After waiting for the water flow in the beaker to settle for 1 minute, water at a depth of 3 cm was collected from the water surface and the number of coliforms was measured. The measurement was performed in accordance with JIS K0350-20-10 (2001) “Test method for coliform bacteria in water and wastewater”.
Specifically, 1 ml each of 1-fold, 10-fold, and 100-fold diluted samples of treated water is placed in a disposable sterilized petri dish, then heated and dissolved at a specified concentration, and then cooled to near 50 ° C. 15 ml of an acid agar medium was added with shaking so that the waste water previously introduced was uniform. After allowing to cool and deoxycholate agar medium solidified, 10 ml of the above medium was added again and overlaid to solidify. Thereafter, the cells were cultured at 36 ± 1 ° C. for 18 to 20 hours, and the number of red colonies formed on the medium was counted to calculate the number in 1 ml of the sample. The number of settlements was counted in a petri dish containing an appropriately diluted sample so that it could be counted between 20 and 200. Moreover, in order to reduce the error by measurement, five things with the same dilution rate were cultured, and the average value of the count was used.

(Turbidity)
Turbidity was measured using TCR-5Z manufactured by Kasahara Kagaku Kogyo. Specifically, 200 ml was taken into a wastewater sampling container attached to TCR-5Z, a sensor was inserted so that bubbles did not adhere to the sensor part, and turbidity (polystyrene) was measured. “Turbidity (polystyrene)” indicates turbidity when polystyrene is used as a standard solution.

(Calculation of the ratio occupied by the total projected area of 0.5-10 mm floc)
After adding PAM, after 60 seconds of stirring, the rotation of the jar tester was stopped and the total projected area of all flocs was measured. Specifically, a predetermined amount of flocculant-containing wastewater (for example, 100 ml) was arbitrarily measured, and the projected area (A) of all flocs present in the predetermined amount was calculated.
Next, the projected area circle equivalent diameter of each floc was calculated from the projected area of each floc. And the total of the projection area (B) of the floc whose projection area circle equivalent diameter is 0.5-10 mm was calculated. The proportion (%) of the total projected area of 0.5 to 10 mm floc was calculated using the following formula.
Ratio (%) of total projected area of floc of 0.5 to 10 mm = B / A × 100
The projected area of the flock was calculated using an image analyzer (DI200 (trade name) manufactured by Oji Scientific Co., Ltd.).

Comparison of Examples and Comparative Examples shows that the number of coliforms is greatly reduced by using both cationic and anionic flocculants. In Examples 1 and 2, the addition rate of the cationic flocculant is high, and the chromaticity is kept low.
On the other hand, about Comparative Examples 1-3, since the floc was not formed and the total projection area of the floc of 0.5-10 mm was out of the predetermined range, the number of coliform groups detected was large.

Example 4
Subsequently, the waste water before the coagulation sedimentation processing of the factory using waste paper was used as the coliform group-containing waste water B. The COD of the coliform group-containing wastewater B was 47.9 mg / L, the turbidity was 200 degrees, the SS was 600 mg / L, and the number of coliform groups was 9100 / ml.

  1 liter of coliform group-containing wastewater B obtained above was set in a jar tester (MJS-6T, manufactured by Miyamoto Seisakusho Co., Ltd.) and pre-stirred at 120 rpm for about 1 minute. Subsequently, a sulfuric acid band (8% product in terms of alumina) was added as a cationic flocculant so as to be 150 mg / L with respect to the drainage weight, and the mixture was stirred at 120 rpm for 60 seconds. While continuing stirring, PAM (manufactured by MT Aqua Polymer, A-235H, medium anion degree, molecular weight 19 million) was added as an anionic flocculant so that the solid content addition rate was 1.5 mg / L, and immediately rotated. The number was lowered to 60 rpm and stirred for 60 seconds. After stirring for 60 seconds, the rotation of the jar tester was stopped and the diameter of the floc that settled was measured. The ratio occupied by the total projected area of 0.5 to 10 mm floc was 94.6%. The turbidity was 5.7 degrees, and the number of coliforms was 146 / ml (removal rate 98.4%).

(Example 5)
The same treatment as in Example 4 was performed except that the sulfuric acid band was 200 mg / L and PAM was 2.2 mg / L in terms of solid content. The proportion of the total projected area of flocs of 0.5 to 10 mm was 98.1%, the turbidity was 2.7 degrees, and the number of coliforms was 82 / ml (removal rate 99.1%).

(Example 6)
Before adding the sulfuric acid band, 30% by mass of wood-derived fibers having a length weighted average of 0.2 mm was added to the solid content in the coliform group-containing waste water B. It stirred for 1 minute and confirmed that there was no binding fiber. The same treatment as in Example 4 was performed, except that the sulfuric acid band was added at 180 mg / L and PAM was added at a solid content addition rate of 2.2 mg / L. The proportion of the total projected area of 0.5 to 10 mm flocs was 98.2%, the turbidity was 1.4 degrees, and the number of coliforms was 2 / ml (removal rate 99.98%).

(Comparative Example 4)
The same treatment as in Example 4 was performed except that the sulfuric acid band was 50 mg / L and PAM was 2.0 mg / L in terms of solid content. The proportion of the total projected area of the flocs of 0.5 to 10 mm was 36.3%, the turbidity was 33.0 degrees, the turbidity was not removed, and the number of coliforms was 3200 / ml (removal rate 64) .8%).

(Comparative Example 5)
The same treatment as in Example 4 was performed except that the sulfuric acid band was 400 mg / L and PAM was 0.5 mg / L in terms of solid content. The proportion of the total projected area of the floc of 0.5 to 10 mm was 62.6%, the turbidity was 31.0 degrees, the turbidity was not removed, and the number of coliforms was 4190 / ml (removal rate 54) 0.0%).

  Examples 4 to 6 and Comparative Examples 4 and 5 were also evaluated by the measurement method described above.

Even when factory effluent is used, comparing the example and the comparative example shows that the number of coliforms is greatly reduced in the example. In particular, in Examples 4 and 5, an appropriate amount of a cationic flocculant and an anionic flocculant is added, and the ratio and turbidity occupied by the total projected area of 0.5 to 10 mm floc are controlled. The number of coliforms detected was extremely small. Furthermore, in Example 6, a higher removal rate of coliform bacteria could be achieved by adding fibers.
On the other hand, in Comparative Examples 4 and 5, since the ratio of the turbidity and the total projected area of flocs of 0.5 to 10 mm was outside the predetermined range, the number of E. coli groups detected was large. That is, it can be seen that a high E. coli group removal effect can be obtained by managing the ratio and turbidity occupied by the total projected area of flocs of 0.5 to 10 mm during aggregation as an index.

10 Sedimentation tank 12 Drainage pipe 14 Treated water pipe 20 Raw water pit 21 Pump 22 In-line mixer 30 Flocculation core 32 E. coli group-containing drainage inlet F Flock

Claims (18)

Adding a cationic flocculant to coliform group-containing wastewater containing fibers;
A step of adding an anionic flocculant and obtaining flocculant-containing wastewater,
The flocculant-containing wastewater includes floc having a floc diameter of 0.5 to 10 mm,
The proportion of the total projected area of the 0.5 to 10 mm floc is 70% or more with respect to the total projected area of all the flocs,
A turbidity of treated water from which floc has been removed from the flocculant-containing wastewater is 0 to 30 degrees, and a method for treating coliform group-containing wastewater.   The method for treating coliform group-containing wastewater according to claim 1, wherein in the step of adding the cationic flocculant, the cationic flocculant is added to the coliform group-containing wastewater so as to be 60 to 6000 mg / L.   The method for treating coliform group-containing wastewater according to claim 1 or 2, wherein the cationic flocculant is an inorganic aluminum flocculant.   The treatment of coliform group-containing wastewater according to claim 3, wherein, in the step of adding the cationic flocculant, the inorganic aluminum-based flocculant is added to the coliform group-containing wastewater so as to be 5 to 600 mg / L in terms of alumina. Method.   5. The process according to claim 1, wherein in the step of obtaining the flocculant-containing wastewater, the anionic flocculant is added to the coliform group-containing wastewater so that the solid content addition rate is 0.6 to 5 mg / L. A method for treating wastewater containing coliforms according to 1.   The method for treating E. coli group-containing wastewater according to any one of claims 1 to 5, wherein the turbidity of treated water obtained by removing floc from the flocculant-containing wastewater is 0 to 10 degrees.   The method for treating wastewater containing Escherichia coli group according to any one of claims 1 to 6, wherein in the step of adding the cationic flocculant, primary floc having an average floc diameter of 0.01 to 0.1 mm is formed. . The step of adding the cationic flocculant and the step of obtaining the flocculant-containing wastewater each have a stirring step,
When the stirring flow rate (m / min) in the step of adding the cationic flocculant is P and the stirring flow rate (m / min) in the step of obtaining the flocculant-containing waste water is Q, 0.2 ≦ Q / P The treatment method for coliform group-containing wastewater according to any one of claims 1 to 7, wherein?   The method for treating coliform group-containing wastewater according to any one of claims 1 to 8, further comprising a step of removing floc from the flocculant-containing wastewater.   The method for treating coliform group-containing wastewater according to any one of claims 1 to 9, wherein the number of coliforms contained in the treated water from which flocs have been removed from the flocculant-containing wastewater is 1000 / mL or less.   The method of treating coliform group-containing wastewater according to any one of claims 1 to 10, wherein the coliform group-containing wastewater is paper mill wastewater. Means for adding a cationic flocculant to a coliform group-containing wastewater containing fibers;
Adding an anionic flocculant after adding the cationic flocculant, and obtaining a flocculant-containing wastewater,
The proportion of the total projected area of 0.5 to 10 mm flocs contained in the flocculant-containing wastewater is 70% or more with respect to the total projected area of all flocs,
A treatment apparatus for coliform group-containing wastewater, wherein the turbidity of treated water from which floc has been removed from the flocculant-containing wastewater can be 0 to 30 degrees.   13. The treatment apparatus for coliform group-containing wastewater according to claim 12, wherein the means for adding the cationic flocculant is means for adding the cationic flocculant to the coliform group-containing wastewater so as to be 60 to 6000 mg / L. .   The coliform group according to claim 12 or 13, wherein the means for adding the cationic flocculant is a means for adding an inorganic aluminum flocculant to the coliform group-containing waste water so as to be 5 to 600 mg / L in terms of alumina. Wastewater treatment equipment.   The means for obtaining the flocculant-containing wastewater is a means for adding the anionic flocculant to the coliform group-containing wastewater so that the solid content addition rate is 0.6 to 5 mg / L. An apparatus for treating wastewater containing coliforms according to claim 1.   The apparatus for treating wastewater containing Escherichia coli group according to any one of claims 12 to 15, wherein the means for adding the cationic flocculant is capable of forming primary flocs having an average floc diameter of 0.01 to 0.1 mm. . The means for adding the cationic flocculant and the means for obtaining the flocculant-containing waste water each have a stirring means,
When the stirring flow rate (m / min) in the means for adding the cationic flocculant is P and the stirring flow rate (m / min) in the means for obtaining the flocculant-containing waste water is Q, 0.2 ≦ Q / P It is <= 0.7, The processing apparatus of the coliform group containing waste_water | drain of any one of Claims 12-16.   The apparatus for treating coliform group-containing wastewater according to any one of claims 12 to 17, further comprising means for removing floc from the flocculant-containing wastewater.

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