JP7484705B2 - Wastewater treatment system and wastewater treatment method - Google Patents

Description

This disclosure relates to a wastewater treatment system and method that can stably and appropriately treat wastewater with large fluctuations in discharge volume and pollutant concentration while conserving resources.

In corrugated cardboard manufacturing plants, wastewater is generated from glue washing water from laminating machines and ink washing water from box making machines. It is necessary to treat these wastewaters so that the treated water quality and wastewater comply with the Water Pollution Prevention Law and the Waste Management Law. Since these wastewaters are washing waters, there are large load fluctuations such as fluctuations in generation frequency, generation volume, and pollutant concentration, making it difficult to obtain stable treated water quality.
As a device to deal with such large load fluctuations, a method that combines coagulation-sedimentation treatment for primary treatment and biological treatment for secondary treatment has been widely introduced. When using membrane separation activated sludge for biological treatment, it is necessary to sufficiently reduce pollutants by coagulation-sedimentation treatment to prevent clogging of the membrane.
In addition, because of the large load fluctuations, the amount of flocculant required to reduce pollutants fluctuates greatly, and it is necessary to respond to the fluctuations even in the automatic control of the amount of flocculant added. As a coagulation and sedimentation treatment method, a means for adjusting the amount of flocculant added depending on the electrical conductivity and flow rate of the water to be treated has been described (for example, Patent Documents 1 to 3).
Patent Document 3 describes a method for measuring the electrical conductivity of a mixture of two types of raw water with different electrical conductivities, and controlling the amount of coagulant added based on the relationship between the mixing ratio and electrical conductivity so that the MFF of the treated water is 1.1 or less.

Japanese Patent Application Laid-Open No. 5-103910 Japanese Patent Application Laid-Open No. 6-304412 JP 2017-77513 A

However, the optimal amount of flocculant to be added does not always depend on the electrical conductivity. When treating multiple wastewaters with similar electrical conductivity but different charge densities, such as glue washing water and ink washing water, it was found that the amount of flocculant to be added calculated based only on the electrical conductivity of the mixed water may not be adequate and may result in excessive addition.
The present disclosure provides a wastewater treatment system and a wastewater treatment method that automatically controls an appropriate amount of flocculant to be added when treating multiple wastewaters with different charge densities.

[1] A wastewater treatment system for mixing two or more types of wastewater and subjecting them to coagulation and sedimentation treatment,
The wastewater having the highest absolute value of the charge density among the two or more types of wastewater is designated as wastewater A;
When the wastewater other than the wastewater A among the two or more types of wastewater is regarded as the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system comprises:
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
A calculation unit is provided for calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value,
The wastewater treatment system is characterized in that in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate coagulant addition amount.
[2] A wastewater treatment system for mixing two or more types of wastewater and subjecting them to coagulation and sedimentation treatment,
Among the two or more types of wastewater, wastewater having an absolute value of charge density exceeding 100 μeq/L is designated as wastewater A;
Among the two or more types of wastewater, wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L is taken as the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system comprises:
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
A calculation unit is provided for calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value,
The wastewater treatment system is characterized in that in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate coagulant addition amount.
[3] The wastewater treatment system according to [1] or [2], wherein the indicator of pollutants is at least one selected from the group consisting of turbidity, suspended solids, ultraviolet absorbance, and chemical oxygen demand.
[4] The wastewater treatment system according to [1] or [2], wherein the indicator of pollutants is turbidity.

[5] The wastewater treatment system comprises:
A storage tank A for storing the wastewater A;
Another storage tank for storing the other wastewater other than the wastewater A;
a mixing tank for mixing the wastewater A sent from the storage tank A with the other wastewater sent from the other storage tank to obtain the mixed water, and a continuous coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water sent from the mixing tank,
The wastewater treatment system comprises:
an electrical conductivity meter A for measuring the electrical conductivity A of the wastewater A and a flow meter A for measuring the flow rate A of the wastewater A conveyed from the storage tank A to the mixing tank;
another electrical conductivity meter for measuring the electrical conductivity of the other wastewater, and a mixed water flow meter for measuring the flow rate of the mixed water sent from the mixing tank to a coagulation sedimentation treatment device;
The calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the flow rate of the mixed water, the electrical conductivity A, the flow rate A, and the electrical conductivity of the other wastewater. Wastewater treatment system described in any of [1] to [4].
[6] The wastewater treatment system comprises:
A storage tank A for storing the wastewater A;
a second storage tank for storing the wastewater other than the wastewater A, and a batch-type coagulation and sedimentation treatment device for mixing the wastewater A sent from the storage tank A and the second storage tank for treating the mixed water by coagulation and sedimentation,
The wastewater treatment system comprises:
an electric conductivity meter A for measuring the electric conductivity A of the wastewater A and a flow meter A for measuring the flow rate A of the wastewater A conveyed from the storage tank A to the coagulation sedimentation treatment device;
Another electrical conductivity meter for measuring the electrical conductivity of the other wastewater, and a water level meter for measuring the amount and water supply time of the mixed water supplied to the coagulation sedimentation treatment device,
The calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the electrical conductivity A, the flow rate A, the electrical conductivity of the other wastewater, as well as the amount of the mixed water and the water supply time. Wastewater treatment system according to any one of [1] to [4].
[7] The wastewater treatment system comprises:
Another storage tank for storing the other wastewater other than the wastewater A;
The wastewater A is delivered and the other wastewater is delivered from the other storage tank, so that the wastewater A and the other wastewater are mixed to obtain the mixed water, and the mixed water is stored in a mixed water storage tank, and the coagulation sedimentation treatment device is provided for coagulating and sedimenting the mixed water delivered from the mixed water storage tank,
The wastewater treatment system comprises:
Another electrical conductivity meter for measuring the electrical conductivity of the other wastewater; a flow meter B for measuring the flow rate B of the other wastewater sent from the other storage tank to the mixed water storage tank;
an electrical conductivity meter C for measuring the electrical conductivity C of the mixed water in the mixed water storage tank;
a mixed water flow meter for measuring a flow rate of the mixed water sent from the mixed water storage tank to the coagulation sedimentation treatment device;
The wastewater treatment system according to any one of [1] to [4], wherein the calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the electrical conductivity of the other wastewater, the flow rate B, the electrical conductivity C, and the flow rate of the mixed water.

[8] The relationship is the following relational formula (1):
The wastewater treatment system according to any one of [5] to [7], wherein the calculation unit calculates the appropriate amount of flocculant to be added by the following relational formula (1).
F = αEA × VA + βEB (VC - VA) ... (1)
(In the formula, F (L/h) is the appropriate amount of flocculant to be added. EA (μS/cm) is the electrical conductivity of wastewater A, VA (m ³ /h) is the flow rate A of wastewater A, EB (μS/cm) is the electrical conductivity of the other wastewater, and VC (m ³ /h) is the flow rate of the mixed water. α and β are coefficients (cm/μS·L/m ³ ), α is a value of 1.0×10 ^-3 to 1.0×10 ^-2 , and β is a value of 1.0×10 ^-4 to 1.0×10 ^-3 .)
[9] After the flocculant is added by the flocculant adding device, the polymer flocculant is added to 1 m of the mixed water.
The wastewater treatment system according to any one of [1] to [8], wherein 0.1 g to 10 g of solids are added per ³ .
[10] The charge density of the wastewater A is -10,000 μeq/L or more and less than -100 μeq/L,
The wastewater treatment system according to any one of [1] to [9], wherein the charge density of the other wastewater is −100 μeq/L to 0 μeq/L.
[11] The two or more types of wastewater are wastewater generated in a cardboard factory,
The wastewater treatment system according to any one of [1] to [10], wherein the wastewater A is ink washing water, and the other wastewater other than the wastewater A is glue washing water.
[12] The wastewater treatment system according to any one of [1] to [11], further comprising a biological reaction tank for biologically treating treated water from the coagulation sedimentation treatment device.
[13] The wastewater treatment system according to [12], wherein the biological reaction tank is a membrane separation activated sludge treatment device.

[14] A wastewater treatment method using a wastewater treatment system equipped with a coagulation sedimentation treatment device that performs coagulation sedimentation treatment on mixed water obtained by mixing two or more types of wastewater, comprising:
The wastewater treatment method comprises:
Wastewater A is a wastewater having the highest absolute value of charge density among the two or more types of wastewater;
A mixing step of mixing the two or more types of wastewater with other wastewater than the wastewater A to obtain the mixed water;
From at least two electrical conductivities of the drainage A, the other drainage, and the mixed water, and the amount of at least two waters of the amount of the drainage A, the amount of the other drainage, and the amount of the mixed water,
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
The method includes a calculation step of calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value, and a coagulation and sedimentation treatment step of subjecting the obtained mixed water to coagulation and sedimentation treatment,
The wastewater treatment method, wherein in the coagulation sedimentation treatment step, the calculated appropriate amount of coagulant to be added is added to the coagulation sedimentation treatment device.
[15] A wastewater treatment method using a wastewater treatment system equipped with a coagulation sedimentation treatment device that performs coagulation sedimentation treatment on mixed water obtained by mixing two or more types of wastewater, comprising:
The wastewater treatment method comprises:
Among the two or more types of wastewater, wastewater A is wastewater having an absolute value of charge density exceeding 100 μeq/L;
A mixing step of mixing the two or more types of wastewater with another wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L to obtain the mixed water;
From at least two electrical conductivities of the drainage A, the other drainage, and the mixed water, and the amount of at least two waters of the amount of the drainage A, the amount of the other drainage, and the amount of the mixed water,
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
The method includes a calculation step of calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value, and a coagulation and sedimentation treatment step of subjecting the obtained mixed water to coagulation and sedimentation treatment,
The wastewater treatment method, wherein in the coagulation and sedimentation treatment step, the calculated appropriate amount of coagulant to be added is added to the coagulation and sedimentation treatment device.

This disclosure provides a wastewater treatment system and method that automatically controls the appropriate amount of flocculant to be added when treating multiple wastewaters with different charge densities.

Conceptual diagram of wastewater treatment system Schematic diagram of one embodiment of a wastewater treatment system. Schematic diagram of one embodiment of a wastewater treatment system. Schematic diagram of one embodiment of a wastewater treatment system. Schematic diagram of one embodiment of a wastewater treatment system.

The expressions "XX to YY" and "XX to YY" representing a numerical range mean a numerical range including the endpoints, that is, the lower limit and the upper limit, unless otherwise specified.
When numerical ranges are stated in stages, the upper and lower limits of each numerical range can be combined in any way.

The present disclosure relates to a wastewater treatment system for mixing two or more types of wastewater and subjecting them to coagulation and sedimentation treatment,
The wastewater having the highest absolute value of the charge density among the two or more types of wastewater is designated as wastewater A;
When the wastewater other than the wastewater A among the two or more types of wastewater is regarded as the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system has a calculation unit that calculates an appropriate amount of flocculant to be added, which makes the index of the pollutant in the mixed water equal to or lower than a predetermined appropriate value, based on a relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, the amount of flocculant to be added, and an index of the pollutant in the mixed water after the addition of the flocculant and precipitation treatment, which is prepared in advance, from the at least two electrical conductivities and the at least two water volumes,
The present invention relates to a wastewater treatment system in which, in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate amount of coagulant to be added.

Another aspect of the present disclosure is a wastewater treatment system for mixing two or more types of wastewater and subjecting them to coagulation and sedimentation treatment,
Among the two or more types of wastewater, wastewater having an absolute value of charge density exceeding 100 μeq/L is designated as wastewater A;
When wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L among the two or more types of wastewater is the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system has a calculation unit that calculates an appropriate amount of flocculant to be added, which makes the index of the pollutant in the mixed water equal to or lower than a predetermined appropriate value, based on a relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, the amount of flocculant to be added, and an index of the pollutant in the mixed water after the addition of the flocculant and precipitation treatment, which is prepared in advance, from the at least two electrical conductivities and the at least two water volumes,
The present invention relates to a wastewater treatment system in which, in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate amount of coagulant to be added.

FIG. 1 is a conceptual diagram of a wastewater treatment system.
The wastewater treatment system mixes two or more types of wastewater and performs coagulation and sedimentation treatment on the mixed water obtained by mixing wastewater A, which is wastewater having the highest absolute value of charge density among the two or more types of wastewater, and other wastewater among the two or more types of wastewater other than wastewater A, using a coagulation and sedimentation treatment device.
In another embodiment, mixed water obtained by mixing wastewater A, which is wastewater having an absolute value of charge density exceeding 100 μeq/L among the two or more types of wastewater, and other wastewater, which is wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L among the two or more types of wastewater, is subjected to coagulation precipitation treatment by a coagulation precipitation treatment device. In another embodiment, there may be a plurality of wastewaters A.

The wastewater treatment system includes an electrical conductivity meter that measures at least two electrical conductivities of wastewater A, other wastewater, and mixed water, and a water volume measuring device that measures at least two water volumes of the amount of wastewater A, other wastewater, and mixed water. The wastewater treatment system also includes a flocculant addition device that adds a flocculant to the coagulation sedimentation treatment device. The wastewater treatment system also includes a calculation unit that calculates (calculates) the amount of flocculant to be added to the coagulation sedimentation treatment device.
The calculation unit calculates, from the at least two measured electrical conductivities and at least two water volumes, an appropriate amount of coagulant to be added that will make the index of the pollutants in the mixed water below a predetermined appropriate value, based on the relationship between the electrical conductivity of wastewater A, the electrical conductivity of the other wastewater, the volume of the mixed water and the mixing ratio of wastewater A and the other wastewater in the mixed water, the amount of coagulant to be added, and the index of the pollutants in the mixed water after the addition of the coagulant and the precipitation treatment (after the coagulation and precipitation treatment), which have been prepared in advance.
Then, the wastewater treatment system adds the calculated appropriate amount of flocculant to the flocculating sedimentation treatment device by the flocculant adding device.

In the wastewater treatment method, a wastewater treatment system is used that is equipped with a coagulation sedimentation treatment device that performs coagulation sedimentation treatment on mixed water obtained by mixing two or more types of wastewater.
And the wastewater treatment method is
Wastewater A is a wastewater having the highest absolute value of charge density among the two or more types of wastewater;
A mixing step of mixing the two or more types of wastewater with other wastewater than the wastewater A to obtain mixed water;
a calculation step of calculating an appropriate amount of flocculant to be added, based on at least two electrical conductivities of the wastewater A, the other wastewater, and the mixed water, and at least two water volumes of the wastewater A, the other wastewater, and the mixed water, based on a previously prepared relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the volume of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, the amount of flocculant to be added, and the indicator of the pollutant of the mixed water after the addition of the flocculant and the sedimentation treatment; and a coagulation and sedimentation treatment step of performing coagulation and sedimentation treatment on the resulting mixed water,
In the coagulation sedimentation treatment step, the calculated appropriate amount of coagulant is added to the coagulation sedimentation treatment device.

Another aspect of the wastewater treatment method is
Among the two or more types of wastewater, wastewater A is wastewater having an absolute value of charge density exceeding 100 μeq/L;
A mixing step of mixing the two or more types of wastewater with another wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L to obtain the mixed water;
a calculation step of calculating an appropriate amount of flocculant to be added, based on at least two electrical conductivities of the wastewater A, the other wastewater, and the mixed water, and at least two water volumes of the wastewater A, the other wastewater, and the mixed water, based on a previously prepared relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the volume of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, the amount of flocculant to be added, and the indicator of the pollutant of the mixed water after the addition of the flocculant and the sedimentation treatment; and a coagulation and sedimentation treatment step of subjecting the resulting mixed water to coagulation and sedimentation treatment,
In the coagulation sedimentation treatment step, the calculated appropriate amount of the coagulant is added to the coagulation sedimentation treatment device.

As described above, when treating multiple wastewaters with different charge densities, the amount of flocculant added calculated based on the electrical conductivity of the mixed water may result in excessive addition. For example, even if the electrical conductivities of wastewaters A and B are the same, if the absolute value of the charge density of wastewater A is high, the amount of flocculant added calculated from the electrical conductivity of the mixed water of wastewaters A and B may result in excessive addition.
On the other hand, when considering automatic control of the coagulation and sedimentation treatment, it is difficult to use the charge density of the wastewater, which is difficult to measure continuously, as an index for determining an appropriate amount of coagulant to be added.

The inventors have studied and found that when equal amounts of flocculant are added to a mixture of wastewater A and B, the higher the mixing ratio of B, the lower the pollutant index such as turbidity of the treated water (i.e., the lower the optimal amount of flocculant to be added). This is thought to be because wastewater with a higher absolute value of charge density requires a larger amount of flocculant to be added for charge neutralization.
The inventors have discovered that when treating mixed water containing multiple wastewaters with different charge densities, it is possible to control the optimal amount of coagulant to be added without excessive addition by focusing on the electrical conductivity of wastewater A, which has a large absolute value of charge density, the electrical conductivity of the other wastewaters, the amount of mixed water, and the mixing ratio of the multiple wastewaters in the mixed water.

There are no particular limitations on the means for acquiring the relationship between the electrical conductivity of wastewater A, the electrical conductivity of the other wastewater, the amount of mixed water and the mixing ratio of wastewater A to the other wastewater in the mixed water, the amount of coagulant added, and the indicator of pollutants in the mixed water after the addition of the coagulant and precipitation treatment.
For example, data on the electrical conductivity and amount of each of a plurality of wastewaters to be subjected to coagulation and sedimentation treatment, and the amount of flocculant required to reduce the pollutant index of each wastewater to an appropriate value or less are obtained in advance. More specifically, the appropriate amount of flocculant to be added for wastewater A and the appropriate amount of flocculant to be added for the other wastewaters are determined in advance by a coagulation test. For each wastewater with a different electrical conductivity, a calibration relationship is obtained between the amount of flocculant to be added and the pollutant index after the coagulant is added and the sedimentation treatment is performed.
An appropriate amount of coagulant to be injected into the mixed water can be calculated based on the mixing ratio of wastewater A to other wastewater in the mixed water and the appropriate amount of coagulant to be added to each wastewater determined as described above.
From these data, it is possible to obtain the relationship between the electrical conductivity of each wastewater, the amount of mixed water, and the mixing ratio of each wastewater in the mixed water, and the amount of coagulant to be added to adjust the indicator of pollutants in the mixed water after adding a coagulant and performing coagulation and sedimentation treatment.

The electrical conductivity A of wastewater A is EA, and the volume of wastewater A is VA.
When another wastewater is wastewater B, the electrical conductivity of the wastewater B is EB, and the amount of the wastewater B is VB.
When the electrical conductivity of the mixed water is EC and the volume of the mixed water is VC,
The following relational expression (A) approximately holds true:
EA x VA + EB x VB = EC x VC ... (A)
In addition, when the mixing ratio of wastewater A in the mixed water is r, the following relational expression (B) approximately holds.
EC = EA × r + EB × (1-r) ... (B)
Even when there are two or more wastewaters other than wastewater A, the other wastewater obtained by mixing them (i.e., wastewater B) can be measured and applied to formulas A and B.

Therefore, if at least two of the electrical conductivity of wastewater A, the electrical conductivity of the other wastewater, and the electrical conductivity of the mixed water, and at least two of the amount of wastewater A, the amount of the other wastewater, and the amount of the mixed water can be measured, all of these values can be calculated. From the viewpoint of automatic control, it is preferable to measure the electrical conductivity of wastewater A and the amount of wastewater A, which have a large absolute value of charge density and are likely to affect the amount of flocculant added.
Therefore, the wastewater treatment system includes an electrical conductivity meter that measures at least two (e.g., two) electrical conductivities of the wastewater A, the other wastewater, and the mixed water. The wastewater treatment system also includes a water volume measuring device that measures at least two (e.g., two) water volumes of the wastewater A, the other wastewater, and the mixed water. An appropriate amount of flocculant to be added can be calculated with a small number of measuring devices. Examples of the water volume measuring device include a flow meter or a water level gauge.

The amount of wastewater may be the volume of the wastewater or the flow rate of the wastewater (volume of the wastewater per unit time). It may be appropriately selected depending on the type of coagulation sedimentation treatment device applied to the wastewater treatment system. The volume of the wastewater can be calculated from the flow rate of the wastewater and the inflow time, and the flow rate of the wastewater can be calculated from the volume of the wastewater and the water conveyance time.
For example, when the coagulation and sedimentation treatment device is a continuous type, the flow rate of the wastewater can be selected. That is, the relationship with the amount of flocculant to be added can be set using the flow rate of wastewater A, the flow rate of other wastewater, and the flow rate of mixed water, and the appropriate amount of flocculant to be added per unit time can be calculated.
In addition, when the coagulation sedimentation treatment device is a batch type, the volume of the wastewater can be selected. That is, the volume of the wastewater A in the coagulation sedimentation tank, the volume of the other wastewater, and the volume of the mixed water can be used to set the relationship with the amount of coagulant to be added, and the appropriate amount of coagulant to be added can be calculated. In the case of the coagulation sedimentation treatment device is a batch type, the flow rate of the wastewater can be selected. The appropriate amount of coagulant to be added per unit time can be calculated based on the flow rate and water supply time of the wastewater, and the amount of coagulant corresponding to the water supply time of the wastewater to the batch type coagulation sedimentation tank can be added.

The measurement of the electrical conductivity and the amount of each wastewater is not particularly limited, and a known electrical conductivity meter, flow meter, and water level meter can be used. From the viewpoint of automatic control, those capable of continuous measurement are preferable.
The positions of measuring devices such as electrical conductivity meters and flow meters in the wastewater treatment system are not particularly limited. They may be appropriately selected depending on the configuration of the wastewater storage tank and mixing tank used and the configuration of the coagulation sedimentation treatment device used. The wastewater treatment system may have an electrical conductivity meter at a position where it can measure the electrical conductivity of wastewater A, the electrical conductivity of other wastewater, or the electrical conductivity of the mixed water. In addition, the wastewater treatment system may have a flow meter or a water level gauge at a position where it can measure the amount of wastewater A, the amount of other wastewater, or the amount of the mixed water.

In addition, when there is one wastewater other than wastewater A among two or more kinds of wastewater, that one is the other wastewater, and when there are multiple kinds of wastewater other than wastewater A, a mixture of these wastewaters is the other wastewater.
When multiple wastewaters other than wastewater A are present, the electrical conductivity of the other wastewaters and the amount of the other wastewaters refer to the electrical conductivity and amount of wastewater mixed with wastewaters other than wastewater A. The electrical conductivity of the other wastewaters and the amount of the other wastewaters may be measured after mixing multiple wastewaters other than wastewater A, or may be values calculated from the values of each of the multiple wastewaters other than wastewater A.
In addition, when a plurality of wastewaters A are present, the electrical conductivity of wastewater A and the amount of wastewater A refer to the electrical conductivity and amount when a plurality of wastewaters A are mixed. The electrical conductivity of wastewater A and the amount of wastewater A may be measured after a plurality of wastewaters A are mixed, or may be values calculated from the values of each of the plurality of wastewaters A.

The indicator of pollutants in the treated water after wastewater treatment is not particularly limited, and examples thereof include turbidity, suspended solids (SS), ultraviolet absorbance (UV), and chemical oxygen demand (COD). It may be appropriately selected according to the downstream equipment of the coagulation and sedimentation treatment and the water quality standard of the discharge. The indicator of pollutants is preferably at least one selected from the group consisting of turbidity, suspended solids, ultraviolet absorbance, and chemical oxygen demand. The amount of flocculant added required to reduce these indicators is correlated with the charge density, and the above-mentioned wastewater treatment system and wastewater treatment method can calculate a more appropriate amount of flocculant to be injected.
The indicator of pollutants is more preferably turbidity. Turbidity can be measured either continuously or at one point. The appropriate value of turbidity is preferably 0.0 to 100.0 degrees, more preferably 8.0 to 60.0 degrees, and even more preferably 10.0 to 15.0 degrees.
The turbidity is measured using a turbidimeter according to the turbidity specified in JIS K0101 "Industrial Water Testing Method" or "JIS K0801 Automatic Turbidity Meter." The measurement method may be continuous measurement or periodic single-point measurement.
For continuous measurements, the transmitted light scattering method or the surface scattered light method specified in "JIS K0801 Automatic Turbidity Meter" is used. For single point measurements, the visual method, transmitted light method, scattered light method, and integrating sphere method specified in JIS K0101 "Industrial Water Testing Method" are used. Turbidity is measured using the supernatant obtained by coagulation and sedimentation treatment.

The coagulation and sedimentation treatment device may be of a batch type or a continuous type.
In the coagulation and sedimentation treatment, a coagulant is added to the mixed water, which causes fine particles in the water to coagulate.
The flocculant is not particularly limited, and any known flocculant can be used, including, for example, inorganic flocculants such as aluminum sulfate (aluminum sulfate), polyiron (polyferric sulfate), polyaluminum chloride, ferric chloride, and ferrous sulfate.
The flocculant is preferably a cationic flocculant, more preferably an iron- or aluminum-based flocculant as a metal-based inorganic flocculant, even more preferably an iron- or aluminum-based flocculant selected from the group consisting of polyiron, aluminum sulfate, and polyaluminum chloride, and most preferably an aluminum-based flocculant selected from the group consisting of aluminum sulfate and polyaluminum chloride.
When the flocculant is aluminum sulfate, it is preferable to use one having an aluminum sulfate concentration of 5% by mass to 15% by mass (more preferably 6% by mass to 10% by mass). Other flocculant aids may be used in combination. Examples of flocculant aids include diatomaceous earth, kaolin, and talc.

In order to adjust the pH to a level suitable for coagulation, a pH adjuster such as a known acid or alkali agent may be added. In the coagulation precipitation treatment, a coagulant and an alkali agent are preferably added.
The pH during flocculation is preferably controlled to about 5.0 to 8.0 in the case of an aluminum-based flocculant, more preferably about 6.0 to 7.5, and even more preferably about 6.5 to 7.0. In the case of an iron-based flocculant, the pH is preferably controlled to 4.0 or more, more preferably about 6.5 to 7.0.

Next, a polymer flocculant may be added to the mixed water to which the flocculant has been added. The polymer flocculant further flocculates the fine particles that have been flocculated by the flocculant, forming larger flocs (flocculation). The formed flocs are more likely to settle, facilitating solid-liquid separation.
The polymer flocculant is not particularly limited, and any known polymer flocculant can be used. For example, polyacrylamide, 2-acryloylamino-2-methylpropanesulfonic acid (AMPS), etc. Polymer flocculants include anionic polymer flocculants, cationic polymer flocculants, nonionic polymer flocculants, etc., and may be appropriately selected depending on the charge state of the mixed water.

The amount of polymer flocculant added is preferably about 0.1 g to 10 g in terms of solid content ^per cubic meter of mixed water to be treated.
The mixed water to which the polymer flocculant has been added and in which flocs have been formed (the treated product of the coagulation-sedimentation treatment) is separated, for example, by sedimentation separation into a supernatant liquid (treated water) and a sediment containing flocs (sludge slurry).

In the wastewater treatment system, the two or more types of wastewater are preferably two types of wastewater.
The two or more types of wastewater are preferably wastewater generated in a food factory or a cardboard factory. More preferably, the two types of wastewater are wastewater generated in a cardboard factory. When the two types of wastewater are wastewater generated in a cardboard factory, the wastewater A (the wastewater having the highest absolute value of charge density or the absolute value of charge density exceeding 100 μeq/L) is preferably ink washing water from a box making machine, and the other types of wastewater other than the wastewater A are preferably glue washing water from a laminating machine.
Ink wash water from box making machines is wastewater that contains at least ink (such as flexographic ink) used for printing on corrugated board.
The glue washing water from the laminating machine is wastewater that contains at least glue (starch, etc.) for gluing cardboard.

The charge density is the unit of cationic or anionic substance required per volume of wastewater to neutralize the surface charge of pollutants present as colloids in the wastewater, and is defined as follows, with the molar equivalent of charge per 1 L being 1 eq/L:
1 μeq/L = 1 μmol/L × number of charges = 96.5 C/ ^m3
The charge density of wastewater A is preferably -10000 μeq/L to -100 μeq/L, more preferably -10000 μeq/L or more and less than -100 μeq/L, even more preferably -1000 μeq/L to -200 μeq/L, and even more preferably -600 μeq/L to -300 μeq/L. The charge density of wastewater other than wastewater A among two or more kinds of wastewater (if there are multiple wastewaters other than wastewater A, the wastewaters obtained by mixing these, i.e., the other wastewaters) is preferably -100 μeq/L to 0 μeq/L, more preferably -50 μeq/L to -5 μeq/L, and even more preferably -30 μeq/L to -10 μeq/L.
In addition, the absolute difference between the charge density of wastewater A and the charge density of other wastewater is preferably 300 μeq/L to 10,000 μeq/L, more preferably 350 μeq/L to 1,000 μeq/L, and even more preferably 350 μeq/L to 500 μeq/L.

The absolute value of the charge density of the wastewater A is preferably 100 μeq/L or more, more preferably more than 100 μeq/L, even more preferably more than 100 μeq/L and not more than 10,000 μeq/L, even more preferably 200 μeq/L to 1,000 μeq/L, and particularly preferably 300 μeq/L to 600 μeq/L. The absolute value of the charge density of the other wastewater is preferably 0 μeq/L to 100 μeq/L, more preferably 5 μeq/L to 50 μeq/L, and even more preferably 10 μeq/L to 30 μeq/L.
The wastewater treatment system and wastewater treatment method disclosed herein can be applied to wastewater having an absolute value of charge density of preferably 10,000 μeq/L or less, more preferably 1,000 μeq/L or less, and even more preferably 600 μeq/L or less.

In the present disclosure, wastewaters are classified into wastewater A and wastewaters other than wastewater A based on the absolute value of the charge density of the wastewaters. The method for measuring and comparing the charge density of the multiple wastewaters is as follows.
For one of the multiple wastewaters, 0.1 L of wastewater is sampled every 3 hours. This is repeated 4 times and all the samples are mixed to obtain multiple cumulative wastewater samples. If it is not possible to sample the wastewater every 3 hours due to the wastewater conditions of the factory, etc., the frequency and sampling amount are adjusted appropriately. The total number of samplings is set to 4 or more, and the total sampling volume is set to 0.4 L or more to minimize the influence of variations in wastewater quality.
The charge density of the accumulated wastewater samples is measured using a charge analyzer (THE RANK BROTHERS CHARGE ANALYZER) or the like.

The electrical conductivity of wastewater A (or a mixture of wastewaters when there are multiple wastewaters A) is preferably 0 μS/cm to 5000 μS/cm, more preferably 100 μS/cm to 1000 μS/cm. The electrical conductivity of the other wastewaters (or a mixture of other wastewaters when there are multiple other wastewaters) other than wastewater A among the two or more types of wastewater is preferably 0 μS/cm to 5000 μS/cm, more preferably 100 μS/cm to 1000 μS/cm.

2 is a schematic diagram of one embodiment of a wastewater treatment system. The wastewater treatment system 100 includes a storage tank 1 for storing wastewater A, which is wastewater having the highest absolute value of charge density among two or more types of wastewater, another storage tank 2 for storing another type of wastewater (wastewater B) other than the wastewater A among the two or more types of wastewater, a mixing tank 3 for mixing the wastewater A sent from the storage tank 1 with the other wastewater sent from the other storage tank 2 to obtain mixed water, and a continuous coagulation sedimentation treatment device 10 for coagulating and sedimenting the mixed water sent from the mixing tank 3.
When there are multiple wastewaters A, the multiple wastewaters A may be sent to storage tank 1 and mixed to obtain wastewater A. When there are multiple other wastewaters, the multiple other wastewaters may be sent to storage tank 2 and mixed to obtain other wastewater.

The wastewater treatment system 100 includes an electrical conductivity meter EM1 that measures the electrical conductivity A of wastewater A, a flow meter FT1 that measures the flow rate A of wastewater A transported from a storage tank 1 to a mixing tank 3, another electrical conductivity meter EM2 that measures the electrical conductivity of another wastewater, and a mixed water flow meter FT2 that measures the flow rate of mixed water transported from the mixing tank 3.
The wastewater treatment system 100 also includes a flocculant adding device 5 that adds a flocculant to the reaction tank 11 of the coagulation sedimentation treatment device 10 .

The wastewater treatment system 100 has a calculation unit 4 that calculates an appropriate amount of coagulant to be added so that the index of pollutants in the mixed water will be equal to or lower than a predetermined appropriate value, based on the relationship between the electrical conductivity of wastewater A, the electrical conductivity of other wastewaters, the amount of mixed water, and the mixing ratio of wastewater A and other wastewaters in the mixed water, the amount of coagulant to be added, and the index of pollutants in the mixed water after addition of the coagulant and sedimentation treatment, which have been prepared in advance.
In order to accurately grasp the amount of mixed water and the mixing ratio of the wastewater, the wastewater treatment system 100 may be provided with a flow meter that measures the flow rate of other wastewater sent from the storage tank 2 to the mixing tank 3 and/or a water level meter that measures the amount of mixed water in the mixing tank 3. The wastewater treatment system 100 does not necessarily have to be provided with a flow meter that measures the flow rate of other wastewater sent from the storage tank 2 to the mixing tank 3 and/or a water level meter that measures the amount of mixed water in the mixing tank 3.

Wastewater A and another wastewater (wastewater B) are supplied from storage tanks 1 and 2, respectively, to a mixing tank 3 by, for example, a pump P, and mixed to obtain mixed water. The mixing tank 3 may be equipped with an agitator 21. The mixed water is continuously supplied to a reaction tank 11 of a coagulation sedimentation treatment device 10 by, for example, a pump P.
The electrical conductivities of wastewater A and the other wastewater are measured by electrical conductivity meters EM1 and EM2. The flow rates of wastewater A and the mixed water are measured by flow meters FT1 and FT2. These measured values are input to the calculation unit 4.

The calculation unit 4 calculates the appropriate amount of flocculant to be added for the mixed water to be treated by the coagulation and sedimentation treatment device 10 from the flow rate, electrical conductivity A, flow rate A, and electrical conductivity of the other wastewater. When calculating, the calculation unit 4 calculates the amount of mixed water and the mixing ratio of wastewater A and other wastewater in the mixed water from the flow rate, electrical conductivity A, flow rate A, and electrical conductivity of the other wastewater, as necessary. Since the flocculant addition device is a continuous type, the appropriate amount of flocculant to be added is preferably calculated as the amount of flocculant per unit time. When the appropriate amount of flocculant to be added calculated by the calculation unit 4 is output to the flocculant addition device 5, the flocculant addition device 5 adds the appropriate amount of flocculant to the reaction tank 11.

A known method may be used for the coagulation and sedimentation treatment in the coagulation and sedimentation treatment device 10. The coagulation and sedimentation treatment device 10 includes a reaction tank 11, a coagulation tank 12, and a sedimentation tank 13.
In the coagulation and sedimentation treatment device 10, a coagulant and, if necessary, a pH adjuster are added to the mixed water in the reaction tank 11 by the coagulant adding device 5, thereby coagulating fine particles in the mixed water. The mixed water to which the coagulant has been added is sent to the coagulation tank 12, where a polymer coagulant is added to the mixed water to flocculate the fine particles. The addition of the polymer coagulant can be automatically controlled by the calculation unit 4 and the coagulant adding device 5, similar to the addition of the coagulant in the reaction tank 11.
The mixed water is then sent to the settling tank 13 for settling treatment. The mixed water is separated into treated water, which is a supernatant liquid, and a sludge slurry containing flocs.

FIG. 3 is a schematic diagram of another embodiment of a wastewater treatment system.
The wastewater treatment system 100 includes a storage tank 1 for storing wastewater A, another storage tank 2 for storing wastewater other than wastewater A, and a batch-type coagulation and sedimentation treatment device 30 that mixes the wastewater A delivered from the storage tank 1 with the other wastewater delivered from the other storage tank 2 and performs coagulation and sedimentation treatment on the resulting mixed water.
When there are multiple wastewaters A, the multiple wastewaters A may be sent to storage tank 1 and mixed to obtain wastewater A. When there are multiple other wastewaters, the multiple other wastewaters may be sent to storage tank 2 and mixed to obtain other wastewater.

The wastewater treatment system 100 also includes an electrical conductivity meter EM1 that measures the electrical conductivity A of wastewater A, a flow meter FT that measures the flow rate A of wastewater A transported from the storage tank 1 to the coagulation sedimentation treatment device 30, another electrical conductivity meter EM2 that measures the electrical conductivity of other wastewater, and a water level meter LT that measures the amount of mixed water transported to the coagulation sedimentation treatment device 30 and the transport time.
In order to accurately grasp the amount of mixed water and the mixing ratio of the wastewater, the wastewater treatment system 100 may be provided with a flow meter that measures the flow rate of the other wastewater sent from the storage tank 2 to the coagulation sedimentation treatment device 30. The wastewater treatment system 100 does not need to be provided with a flow meter that measures the flow rate of the other wastewater sent from the storage tank 2 to the coagulation sedimentation treatment device 30.

The wastewater treatment system 100 also includes a flocculant adding device 5 that adds a flocculant to the coagulation sedimentation treatment device 30 .
The wastewater treatment system 100 has a calculation unit 4 that calculates an appropriate amount of coagulant to be added so that the index of pollutants in the mixed water is below a predetermined appropriate value, based on the relationship between the electrical conductivity A of wastewater A, the electrical conductivity of the other wastewaters, the amount of mixed water and the mixing ratio of wastewater A and the other wastewaters in the mixed water, the amount of coagulant to be added, and the index of pollutants in the mixed water after the addition of the coagulant and precipitation treatment, which have been prepared in advance.

Wastewater A and another wastewater (wastewater B) are supplied batchwise from storage tanks 1 and 2, respectively, to a coagulation sedimentation treatment device 30 by, for example, a pump P. Mixed water is supplied, for example, up to the upper limit of a water level gauge LT.
The electrical conductivity of wastewater A and the other wastewater, and the flow rate A of wastewater A are measured and input to the calculation unit 4. The water volume (water level) of the coagulation sedimentation treatment device 30 and the water supply time of the mixed water are input to the calculation unit 4. The calculation unit 4 calculates, as necessary, the amount of mixed water and the mixing ratio of wastewater A to the other wastewater in the mixed water for the mixed water contained in the coagulation sedimentation treatment device 30 from the electrical conductivity A, the flow rate A, the electrical conductivity of the other wastewater, and the amount and water supply time of the mixed water.
The calculation unit 4 then calculates the appropriate amount of flocculant to be added from these input values. When the calculated appropriate amount of flocculant to be added is output to the flocculant addition device 5, the flocculant addition device 5 adds the appropriate amount of flocculant to the coagulation and sedimentation treatment device 30.

The coagulation and sedimentation treatment device 30 is a batch-type coagulation and sedimentation treatment device. In the coagulation and sedimentation treatment device 30, the coagulation and sedimentation treatment may be performed by a known method.
In the coagulation sedimentation treatment device 30, first, a coagulant and, if necessary, a pH adjuster are added to the mixed water by the coagulant adding device 5 to coagulate fine particles in the mixed water. The coagulation sedimentation treatment device 30 may be equipped with a stirring device 21. Next, a polymer coagulant is added to the water to be treated, and the coagulated fine particles are flocculated. The addition of the polymer coagulant can also be automatically controlled by the calculation unit 4 and the coagulant adding device 5. Then, the mixed water is left to stand for a predetermined time, and the mixed water is separated into treated water, which is a supernatant liquid, and a sludge slurry containing flocs.

FIG. 4 is a schematic diagram of another embodiment of a wastewater treatment system.
The wastewater treatment system 100 includes another storage tank 2 for storing wastewater other than wastewater A, a mixed water storage tank 6 into which wastewater A is pumped and other wastewater is pumped from the other storage tank 2 to obtain mixed water by mixing the wastewater A and the other wastewater, and a coagulation and sedimentation treatment device 10 for performing coagulation and sedimentation treatment of the mixed water pumped from the mixed water storage tank 6.
When there are multiple wastewaters A, the multiple wastewaters A may be sent to the mixed water storage tank 6. When there are multiple other wastewaters, the multiple other wastewaters may be sent to the storage tank 2 and mixed to produce the other wastewater.

The wastewater treatment system 100 is equipped with another electrical conductivity meter EM2 that measures the electrical conductivity of the other wastewater, a flow meter FT2 that measures the flow rate B of the other wastewater sent from the other storage tank 2 to the mixed water storage tank 6, an electrical conductivity meter EM3 that measures the electrical conductivity C of the mixed water in the mixed water storage tank 6, and a mixed water flow meter FT3 that measures the flow rate of the mixed water sent from the mixed water storage tank 6.
The wastewater treatment system 100 also includes a flocculant adding device 5 that adds a flocculant to the reaction tank 11 of the coagulation sedimentation treatment device 10 .

The wastewater treatment system 100 has a calculation unit 4 that calculates an appropriate amount of coagulant to be added so that the index of pollutants in the mixed water will be equal to or lower than a predetermined appropriate value, based on the relationship between the electrical conductivity of wastewater A, the electrical conductivity of other wastewaters, the amount of mixed water, and the mixing ratio of wastewater A and other wastewaters in the mixed water, the amount of coagulant to be added, and the index of pollutants in the mixed water after addition of the coagulant and sedimentation treatment, which have been prepared in advance.
In order to accurately grasp the amount of mixed water and the mixing ratio of the wastewater, the wastewater treatment system 100 may be provided with a flow meter that measures the flow rate of the wastewater A and/or a water level meter that measures the amount of mixed water in the mixed water storage tank 6. The wastewater treatment system 100 does not necessarily have to be provided with a flow meter that measures the flow rate of the wastewater A and/or a water level meter that measures the amount of mixed water in the mixed water storage tank 6.

Another wastewater (wastewater B) is supplied from another storage tank 2 to the mixed water storage tank 6 together with the wastewater A by, for example, a pump P, and mixed to obtain mixed water. The mixed water storage tank 6 may be equipped with an agitator 21. The mixed water is continuously supplied to the reaction tank 11 of the coagulation sedimentation treatment device 10 by, for example, a pump P.

The electrical conductivity of the other wastewater, the electrical conductivity C of the mixed water, the flow rate B of the other wastewater, and the flow rate of the mixed water are measured, and these measured values are input to the calculation unit 4. The calculation unit 4 calculates, as necessary, the electrical conductivity A of wastewater A, the amount of the mixed water, and the mixing ratio of wastewater A to the other wastewater in the mixed water, for the mixed water contained in the coagulation and sedimentation treatment device 10, from the electrical conductivity, flow rate B, electrical conductivity C of the other wastewater, and the flow rate of the mixed water.
The calculation unit 4 then calculates the appropriate amount of flocculant to be added from these input values. When the calculated appropriate amount of flocculant to be added is output to the flocculant addition device 5, the flocculant addition device 5 adds the appropriate amount of flocculant to the reaction tank 11 of the coagulation and sedimentation treatment device 10.
The coagulation and sedimentation treatment device 10 is the same as that shown in FIG.

FIG. 5 is a schematic diagram of another embodiment of a wastewater treatment system.
The wastewater treatment system 100 includes another storage tank 2 for storing wastewater other than wastewater A, a mixed water storage tank 6 into which wastewater A is pumped and the other wastewater is pumped from the other storage tank 2 to obtain mixed water, and in which the mixed water is stored, and a batch-type coagulation and sedimentation treatment device 30 for coagulating and sedimenting the mixed water pumped from the mixed water storage tank 6.
When there are multiple wastewaters A, the multiple wastewaters A may be sent to the mixed water storage tank 6. When there are multiple other wastewaters, the multiple other wastewaters may be sent to the storage tank 2 and mixed to produce the other wastewater.

The wastewater treatment system 100 is equipped with another electrical conductivity meter EM2 that measures the electrical conductivity of the other wastewater, a flow meter FT2 that measures the flow rate B of the other wastewater sent from the other storage tank 2 to the mixed water storage tank 6, an electrical conductivity meter EM3 that measures the electrical conductivity C of the mixed water in the mixed water storage tank 6, and a mixed water flow meter FT3 that measures the flow rate of the mixed water sent from the mixed water storage tank 6 to the coagulation sedimentation treatment device 30.
The wastewater treatment system 100 also includes a flocculant adding device 5 that adds a flocculant to the coagulation sedimentation treatment device 30 .

The wastewater treatment system 100 has a calculation unit 4 that calculates an appropriate amount of coagulant to be added so that the index of pollutants in the mixed water is below a predetermined appropriate value, based on the relationship between the electrical conductivity A of wastewater A, the electrical conductivity of the other wastewaters, the amount of mixed water and the mixing ratio of wastewater A and the other wastewaters in the mixed water, the amount of coagulant to be added, and the index of pollutants in the mixed water after the addition of the coagulant and precipitation treatment, which have been prepared in advance.
In order to accurately grasp the amount of mixed water and the mixing ratio of the wastewater, the wastewater treatment system 100 may be provided with a flow meter that measures the flow rate of wastewater A, a water level gauge that measures the amount of mixed water in the mixed water storage tank 6, and/or a water level gauge LT that measures the amount of mixed water and the water transport time of the mixed water in the coagulation sedimentation treatment device 30. The wastewater treatment system 100 does not have to be provided with a flow meter that measures the flow rate of wastewater A, a water level gauge that measures the amount of mixed water in the mixed water storage tank 6, and/or a water level gauge LT that measures the amount of mixed water and the water transport time of the mixed water in the coagulation sedimentation treatment device 30.

Another wastewater (wastewater B) is supplied from another storage tank 2 to the mixed water storage tank 6 together with wastewater A by, for example, a pump P, and mixed to obtain mixed water. The mixed water storage tank 6 may be equipped with an agitator 21. The mixed water is supplied to the coagulation and sedimentation treatment device 30 in batches by, for example, a pump P. The mixed water is supplied, for example, up to the upper limit of the water level gauge LT.

The electrical conductivity of the other wastewater, the electrical conductivity of the mixed water, the flow rate B of the other wastewater, and the flow rate of the mixed water are measured. In addition, an integrated measurement value of the water supply time during which the mixed water is supplied to the coagulation sedimentation treatment device 30 is input to the calculation unit 4. The calculation unit 4 calculates, as necessary, the electrical conductivity A of wastewater A, the amount of the mixed water, and the mixing ratio of wastewater A to the other wastewater in the mixed water for the mixed water contained in the coagulation sedimentation treatment device 30 from the electrical conductivity, flow rate B, electrical conductivity C of the other wastewater, and the flow rate of the mixed water.
The calculation unit 4 then calculates the appropriate amount of flocculant to be added from these input values. When the calculated appropriate amount of flocculant to be added is output to the flocculant addition device 5, the flocculant addition device 5 adds the appropriate amount of flocculant to the coagulation and sedimentation treatment device 30.
The coagulation and sedimentation treatment device 30 is the same as that shown in FIG.

The relationship between the electrical conductivity of wastewater A, the electrical conductivity of the other wastewater, the amount of mixed water and the mixing ratio of wastewater A and the other wastewater in the mixed water, the amount of flocculant to be added, and the index of the pollutants in the mixed water after the addition of the flocculant and the precipitation treatment can be expressed, for example, by the following relational formula (1). It is preferable that the calculation unit 4 calculates the appropriate amount of flocculant to be added by the following relational formula (1).
F = αEA × VA + βEB (VC - VA) ... (1)
(In formula (1), F (L/h) is the appropriate amount of flocculant to be added, EA (μS/cm) is the electrical conductivity of wastewater A, VA (m ³ /h) is the flow rate A of wastewater A, EB (μS/cm) is the electrical conductivity of the other wastewater, and VC (m ³ /h) is the flow rate of mixed water.
α and β are coefficients (cm/μS·L/m ³ ), α is a value of 1.0×10 ⁻³ to 1.0×10 ⁻² , and β is a value of 1.0×10 ⁻⁴ to 1.0×10 ⁻³ (preferably 3.0×10 ⁻⁴ to 7.0×10 ⁻⁴ ).

In the various measuring devices in a wastewater treatment system, it may not be possible to directly obtain the above EA, VA, EB, and VC. In such cases, EA, VA, EB, and VC may be calculated based on the above-mentioned relational expressions (A) and (B) and the volume, flow rate, and water supply time of the mixed water.
For example, when the flow rate of the mixed water is VC ( ^m3 /h), the electrical conductivity of the mixed water is EC (μS/cm), the electrical conductivity of the other wastewater is EB (μS/cm), and the flow rate B is VB ( ^m3 /h), based on the above-mentioned relational formula (A), formula (1) can also be expressed as the following formula (2).
F = α (EC × VC - EB × VB) + βEB × VB ... (2)
(In formula (2), α and β are coefficients (cm/μS·L/m ³ ), α is a value of 1.0×10 ⁻³ to 1.0×10 ⁻² , and β is a value of 1.0×10 ⁻⁴ to 1.0×10 ⁻³ (preferably 3.0×10 ⁻⁴ to 7.0×10 ⁻⁴ ).)

The unit of the flocculant addition amount F may be appropriately selected depending on the type, form, concentration, etc. of the flocculant used. Although the flocculant addition amount F is expressed in L/h, for example, when the flocculant is a powder, it may be expressed in g/h.
When the coagulation and sedimentation treatment is a batch type, as described above, the appropriate amount of coagulant to be added per unit time is calculated based on the flow rate of the wastewater, and the amount of coagulant corresponding to the inflow time of the wastewater into the batch type coagulation and sedimentation tank is added. In addition, in the case of a batch type, each flow rate may be calculated as a water amount (volume). In that case, the appropriate amount of coagulant to be added F (L or g) can be calculated from formula (1) by assuming that VA (m ³ /h) is the amount VA (m ³ ) of wastewater A and VC (m ³ /h) is the amount VC (m ³ ) of mixed water.

The coefficients α and β are coefficients related to the electrical conductivity and charge density of the wastewater to determine the amount of flocculant to be added. In the same manner as the above-mentioned means for obtaining the relationship between the electrical conductivity of wastewater A, the electrical conductivity of other wastewaters, the amount of mixed water, the mixing ratio of wastewater A and other wastewaters in the mixed water, the amount of flocculant to be added, and the indicator of the pollutants in the mixed water after the addition of the flocculant and the precipitation treatment, α and β can be obtained from the calibration relationship between the electrical conductivity of each wastewater and the appropriate amount of flocculant to be added.
The coefficients α and β may vary depending on the measured values of the calibration relationship depending on the type, form, concentration, etc. of the flocculant. When the flocculant is an aluminum-based flocculant, the coefficients α and β can be calculated from the amount of flocculant added converted to alumina.
In formula (1), αEA×VA corresponds to the amount of flocculant added to wastewater A in the mixed water. Also, βEB(VC-VA) corresponds to the amount of flocculant added to wastewater B in the mixed water. The higher the electrical conductivity and charge density of the wastewater, the larger α and β become.

The wastewater treatment system may include a biological reactor that biologically treats the treated water from the coagulation sedimentation treatment device. The biological reactor is not particularly limited, and a known biological reactor may be used. In the biological treatment tank, biological treatment (biological treatment) is carried out.
Biological treatment is roughly divided into activated sludge treatment apparatuses that use suspended sludge and biofilm treatment apparatuses that support sludge on a carrier, and either type of apparatus can be applied to wastewater treatment systems.

Preferred activated sludge treatment devices are standard activated sludge treatment devices equipped with an aeration tank and a settling tank for returning sludge, batch-type activated sludge treatment devices which alternate between aeration and settling in one tank, and membrane separation activated sludge treatment devices (MBR devices) which separate sludge from treated water using a separation membrane immersed in the aeration tank.
More preferably, it is a membrane separation activated sludge treatment device (MBR device). In the above wastewater treatment system, even if the amount of coagulant added is likely to fluctuate, it is easy to calculate the amount of coagulant added that satisfactorily reduces indicators of pollutants such as turbidity. Therefore, even if a membrane separation activated sludge treatment device is provided after the coagulation sedimentation treatment device, it is easy to prevent membrane clogging.

The present invention will be specifically explained below with reference to examples. The following examples are not intended to limit the present invention in any way.

In the following examples, the electrical conductivity A of wastewater A is EA (μS/cm), the flow rate A of wastewater A is VA (m ³ /h), the electrical conductivity of wastewater B is EB (μS/cm), the flow rate B of wastewater B is VB (m ³ /h), the electrical conductivity of the mixed water is EC (μS/cm), and the flow rate of the mixed water is VC (m ³ /h).
In the following examples, turbidity was measured by a transmitted light method.

Example 1
Using the wastewater treatment system of the embodiment shown in FIG. 2, wastewater treatment was carried out as follows.
Ink washing wastewater was used as wastewater A, glue washing wastewater was used as wastewater B, and a metallic inorganic flocculant, aluminum sulfate (aluminum sulfate concentration 8 mass% (aluminum sulfate, Kyokuyo Co., Ltd.)), was used as the flocculant. The electrical conductivity EA and flow rate VA of wastewater A, the electrical conductivity EB of wastewater B, and the flow rate VC of mixed water at the mixing tank outlet were measured when the total wastewater volume VC (= VA + VB) was 1.00 ^m3 /h.
The charge density of wastewater A was −437 μeq/L, and the charge density of wastewater B was −17 μeq/L.
In the following formula (X), the coefficient α for determining the appropriate flocculant addition amount F (L/h) for making the turbidity of the treated water 15 degrees or less was examined, and the result is shown in Table 1. Similarly, the coefficient β was examined, and the result was β = 5.0 × ^10-4 .
F = α EA VA + β EB (VC-VA) ... (X)
1.0× ^10-3 ≦α≦1.0× ^10-2

上記表は、ＥＡ・ＶＡの各範囲に対応した、係数αの値を示す。

The above table shows the value of the coefficient α corresponding to each range of EA and VA.

Using the wastewater treatment system shown in Figure 2, when EA = 364 µS/cm, VA = 0.67 m ³ /h, EB = 321 µS/cm, and VC = 1.00 ^{m 3} /h, the optimal amount of aluminum sulfate to be added was determined to be 1.03 L/h based on formula (X) and Table 1. When wastewater treatment was performed with this amount to be added, the turbidity of the treated water was 11 degrees, which satisfied the standard, and the amount of flocculant to be added was not excessive.

(Comparative Example 1)
In the wastewater treatment system shown in Fig. 2, wastewater treatment was carried out using the same wastewater as in Example 1. The electrical conductivity EC of the mixed water in the mixing tank and the flow rate VC of the mixed water at the outlet of the mixing tank were measured, and EC was 370 µS/cm and VC was 1.00 m ³ /h.
The optimum amount of aluminum sulfate added was determined based on formula (X) and Table 1 in the same manner as in Example 1, assuming EC=EA and VC=VA, and was found to be 2.22 L/h. When wastewater treatment was performed with this amount added, the turbidity of the treated water reached 5 degrees, which met the standard, but the necessary amount was greater than in Example 1 and was an excessive amount.

(Reference Example 1)
2, the optimum amount of aluminum sulfate added was determined in the same manner as in Example 1, except that α in formula (X) was set to 5.0×10 ⁻⁴ (outside the range of α in Table 1), and was found to be 0.17 L/h. When wastewater treatment was performed with this amount added, the turbidity of the treated water was 60 degrees, which did not satisfy the standard.

(Reference Example 2)
2, the optimum amount of aluminum sulfate to be added was determined in the same manner as in Example 1, except that α in formula (X) was set to 2.0×10 ^-2 (outside the range of α in Table 1), and was found to be 4.93 L/h. When wastewater treatment was performed with this amount to be added, the turbidity of the treated water was 3.6 degrees, which satisfied the standard, but the amount required to be added was greater than that in Example 1, being an excessive amount.

In Example 1, by using EA and VA from wastewater A and EB and (VC-VA) from wastewater B, the amount of flocculant required to be added was less than when EC and VC from mixed water C were used as in Comparative Example 1.

If the amount of flocculant to be added were determined based solely on the electrical conductivity and flow rate of the mixed water, an excessive amount of flocculant would be added. On the other hand, by measuring the electrical conductivity and flow rate of wastewater A, as well as the electrical conductivity and flow rate of the mixed water, and using these as the indicated values to determine the amount of flocculant to be added, the optimal amount of flocculant to be added was obtained.

Example 2
Using the wastewater treatment system shown in Fig. 4, wastewater was treated in the same manner as in Example 1. EC = 370 µS/cm, VC = 1.00 m ³ /h, EB = 321 µS/cm, VB = 0.33
^m3 /h. The optimum amount of aluminum sulfate added was calculated based on Table 1, formula (X) and the following formula (Y) in the same manner as in Example 1, and was found to be 1.11 L/h. When wastewater treatment was performed with this amount added, the turbidity of the treated water was 11 degrees, which satisfied the standard, and the amount of flocculant added was not excessive.
EA·VA=EC·VC-EB·VB ... (Y)

(Comparative Example 2)
4, wastewater treatment was carried out using the same wastewater as in Example 1. The electrical conductivity and flow rate at the outlet of the mixed water storage tank 6 were measured, and the results were EC = 370 μS/cm and VC = 1.00 m ³ /h.
The optimum amount of aluminum sulfate added was determined based on Table 1 and formula (X) in the same manner as in Example 2, assuming EC=EA and VC=VA, and was found to be 2.22 L/h. When wastewater treatment was performed with this amount added, the turbidity of the treated water reached 5 degrees, which met the standard, but the amount required to be added was greater than in Example 2, being an excessive amount.

(Reference Example 3)
4, the optimum amount of aluminum sulfate added was determined in the same manner as in Example 2, except that α in formula (X) was set to 5.0×10 ⁻⁴ (outside the range of α in Table 1), and the result was 0.19 L/h. When wastewater treatment was performed with this amount added, the turbidity of the treated water was 60 degrees, which did not satisfy the standard.

(Comparative Example 3)
4, the optimum amount of aluminum sulfate to be added was determined in the same manner as in Example 2, except that α in formula (X) was set to 2.0×10 ^-2 (outside the range of α in Table 1), and was found to be 5.33 L/h. When wastewater treatment was performed with this amount to be added, the turbidity of the treated water was 3.6 degrees, which satisfied the standard, but the amount required to be added was greater than that in Example 2, being an excessive amount.

In Example 2, by using EC and VC from mixed water C and EB and VB from wastewater B, the amount of flocculant required to be added was less than that required in Comparative Example 2, when only EC and VC from mixed water C was used.

If the amount of flocculant to be added were determined based solely on the electrical conductivity and flow rate of the mixed water, an excessive amount of flocculant would be added. On the other hand, by measuring the electrical conductivity and flow rate of wastewater B, as well as the electrical conductivity and flow rate of the mixed water, and using these as the indicated values to determine the amount of flocculant to be added, the optimal amount of flocculant to be added was obtained.

100: wastewater treatment system, 1: storage tank, 2: other storage tank, 3: mixing tank, 4: calculation unit, 5: flocculant addition device, 6: mixed water storage tank, 10: continuous type coagulation sedimentation treatment device, 11: reaction tank, 12: coagulation tank, 13: sedimentation tank, 21: agitation device, 30: batch type coagulation sedimentation treatment device

Claims (15)

A wastewater treatment system that mixes two or more types of wastewater and performs coagulation and sedimentation treatment,
The wastewater having the highest absolute value of the charge density among the two or more types of wastewater is designated as wastewater A;
When the wastewater other than the wastewater A among the two or more types of wastewater is regarded as the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system comprises:
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
A calculation unit is provided for calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value,
The relationship is
A suitable amount of flocculant to be added to the wastewater A and a suitable amount of flocculant to be added to the other wastewater are determined in advance by a flocculation test,
When the calibration relationship between the amount of flocculant added and the indicator of pollutants after the flocculant was added and the precipitation treatment was performed for the wastewater A and the other wastewater was obtained,
The relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of each wastewater in the mixed water, and the amount of flocculant to be added, which is obtained from the calibration relationship;
The wastewater treatment system is characterized in that in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate coagulant addition amount. A wastewater treatment system that mixes two or more types of wastewater and performs coagulation and sedimentation treatment,
Among the two or more types of wastewater, wastewater having an absolute value of charge density exceeding 100 μeq/L is designated as wastewater A;
When wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L among the two or more types of wastewater is the other wastewater,
The wastewater treatment system performs coagulation and sedimentation treatment on mixed water, the mixed water being obtained by mixing the wastewater A with the other wastewater,
The wastewater treatment system comprises:
an electrical conductivity meter for measuring at least two electrical conductivities of the drainage water A, the other drainage water, and the mixed water;
a water amount measuring device for measuring at least two water amounts among the amount of the wastewater A, the amount of the other wastewater, and the amount of the mixed water;
The method includes a coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water, and a coagulant adding device for adding a coagulant to the coagulation and sedimentation treatment device,
The wastewater treatment system comprises:
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
A calculation unit is provided for calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value,
The relationship is
A suitable amount of flocculant to be added to the wastewater A and a suitable amount of flocculant to be added to the other wastewater are determined in advance by a flocculation test,
When the calibration relationship between the amount of flocculant added and the indicator of pollutants after the flocculant was added and the precipitation treatment was performed for the wastewater A and the other wastewater was obtained,
The relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of each wastewater in the mixed water, and the amount of flocculant to be added, which is obtained from the calibration relationship;
The wastewater treatment system is characterized in that in the coagulation sedimentation treatment, the coagulant is added to the coagulation sedimentation treatment device by the coagulant adding device in the calculated appropriate coagulant addition amount. The wastewater treatment system according to claim 1 or 2, wherein the indicator of pollutants is at least one selected from the group consisting of turbidity, suspended solids, ultraviolet absorbance, and chemical oxygen demand. The wastewater treatment system according to claim 1 or 2, wherein the indicator of pollutants is turbidity. The wastewater treatment system comprises:
A storage tank A for storing the wastewater A;
Another storage tank for storing the other wastewater other than the wastewater A;
a mixing tank for mixing the wastewater A sent from the storage tank A with the other wastewater sent from the other storage tank to obtain the mixed water, and a continuous coagulation and sedimentation treatment device for coagulating and sedimenting the mixed water sent from the mixing tank,
The wastewater treatment system comprises:
an electrical conductivity meter A for measuring the electrical conductivity A of the wastewater A and a flow meter A for measuring the flow rate A of the wastewater A conveyed from the storage tank A to the mixing tank;
another electrical conductivity meter for measuring the electrical conductivity of the other wastewater, and a mixed water flow meter for measuring the flow rate of the mixed water sent from the mixing tank to a coagulation sedimentation treatment device;
The calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the flow rate of the mixed water, the electrical conductivity A, the flow rate A, and the electrical conductivity of the other wastewater. The wastewater treatment system according to any one of claims 1 to 4. The wastewater treatment system comprises:
A storage tank A for storing the wastewater A;
a second storage tank for storing the wastewater other than the wastewater A, and a batch-type coagulation and sedimentation treatment device for mixing the wastewater A sent from the storage tank A with the other wastewater sent from the second storage tank, and performing coagulation and sedimentation treatment on the resulting mixed water,
The wastewater treatment system comprises:
an electric conductivity meter A for measuring the electric conductivity A of the wastewater A and a flow meter A for measuring the flow rate A of the wastewater A conveyed from the storage tank A to the coagulation sedimentation treatment device;
Another electrical conductivity meter for measuring the electrical conductivity of the other wastewater, and a water level meter for measuring the amount and water supply time of the mixed water supplied to the coagulation sedimentation treatment device,
The wastewater treatment system according to any one of claims 1 to 4, wherein the calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the electrical conductivity A, the flow rate A, the electrical conductivity of the other wastewater, and the amount of the mixed water and the water delivery time. The wastewater treatment system comprises:
Another storage tank for storing the other wastewater other than the wastewater A;
The wastewater A is delivered and the other wastewater is delivered from the other storage tank, so that the wastewater A and the other wastewater are mixed to obtain the mixed water, and the mixed water is stored in a mixed water storage tank, and the coagulation sedimentation treatment device is provided for coagulating and sedimenting the mixed water delivered from the mixed water storage tank,
The wastewater treatment system comprises:
Another electrical conductivity meter for measuring the electrical conductivity of the other wastewater; a flow meter B for measuring the flow rate B of the other wastewater sent from the other storage tank to the mixed water storage tank;
an electrical conductivity meter C for measuring the electrical conductivity C of the mixed water in the mixed water storage tank;
a mixed water flow meter for measuring a flow rate of the mixed water sent from the mixed water storage tank to the coagulation sedimentation treatment device;
The wastewater treatment system according to any one of claims 1 to 4, wherein the calculation unit calculates the appropriate amount of coagulant to be added based on the relationship from the electrical conductivity of the other wastewater, the flow rate B, the electrical conductivity C, and the flow rate of the mixed water. The relationship is the following relational formula (1):
The wastewater treatment system according to any one of claims 5 to 7, wherein the calculation unit calculates the appropriate amount of flocculant to be added by the following relational expression (1):
F = αEA × VA + βEB (VC - VA) ... (1)
(In the formula, F (L/h) is the appropriate amount of flocculant to be added. EA (μS/cm) is the electrical conductivity of wastewater A, VA (m ³ /h) is the flow rate A of wastewater A, EB (μS/cm) is the electrical conductivity of the other wastewater, and VC (m ³ /h) is the flow rate of the mixed water. α and β are coefficients (cm/μS·L/m ³ ), α is a value of 1.0×10 ^-3 to 1.0×10 ^-2 , and β is a value of 1.0×10 ^-4 to 1.0×10 ^-3 .) The wastewater treatment system according to any one of claims 1 to 8, wherein after the addition of the flocculant by the flocculant adding device, 0.1 g to 10 g of polymer flocculant is added per 1 ^m3 of the mixed water in terms of solid content. The charge density of the wastewater A is -10,000 μeq/L or more and less than -100 μeq/L,
The wastewater treatment system according to any one of claims 1 to 9, wherein the charge density of the other wastewater is -100 μeq/L to 0 μeq/L. The two or more types of wastewater are wastewater generated in a cardboard factory,
The wastewater treatment system according to any one of claims 1 to 10, wherein the wastewater A is ink washing water, and the other wastewater other than the wastewater A is glue washing water. The wastewater treatment system according to any one of claims 1 to 11, further comprising a biological reaction tank for biologically treating the treated water from the coagulation and sedimentation treatment device. The wastewater treatment system according to claim 12, wherein the biological reactor is a membrane separation activated sludge treatment device. A wastewater treatment method using a wastewater treatment system equipped with a coagulation sedimentation treatment device that performs coagulation sedimentation treatment on mixed water obtained by mixing two or more types of wastewater,
The wastewater treatment method comprises:
Wastewater A is a wastewater having the highest absolute value of charge density among the two or more types of wastewater;
A mixing step of mixing the two or more types of wastewater with other wastewater than the wastewater A to obtain the mixed water;
From at least two electrical conductivities of the drainage A, the other drainage, and the mixed water, and the amount of at least two waters of the amount of the drainage A, the amount of the other drainage, and the amount of the mixed water,
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
The method includes a calculation step of calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value, and a coagulation and sedimentation treatment step of subjecting the obtained mixed water to coagulation and sedimentation treatment,
The relationship is
A proper amount of flocculant to be added to the wastewater A and a proper amount of flocculant to be added to the other wastewater are determined in advance by a flocculation test,
When the calibration relationship between the amount of flocculant added and the indicator of pollutants after the flocculant was added and the precipitation treatment was performed for the wastewater A and the other wastewater was obtained,
The relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of each wastewater in the mixed water, and the amount of flocculant to be added, which is obtained from the calibration relationship;
The wastewater treatment method, wherein in the coagulation and sedimentation treatment step, the calculated appropriate amount of coagulant to be added is added to the coagulation and sedimentation treatment device. A wastewater treatment method using a wastewater treatment system equipped with a coagulation sedimentation treatment device that performs coagulation sedimentation treatment on mixed water obtained by mixing two or more types of wastewater,
The wastewater treatment method comprises:
Among the two or more types of wastewater, wastewater A is wastewater having an absolute value of charge density exceeding 100 μeq/L;
A mixing step of mixing the two or more types of wastewater with another wastewater having an absolute value of charge density of 0 μeq/L to 100 μeq/L to obtain the mixed water;
From at least two electrical conductivities of the drainage A, the other drainage, and the mixed water, and the amount of at least two waters of the amount of the drainage A, the amount of the other drainage, and the amount of the mixed water,
The electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of the wastewater A and the other wastewater in the mixed water, which have been prepared in advance,
The amount of flocculant added;
Based on the relationship between the addition of the coagulant and the indicator of the pollutants in the mixed water after the sedimentation treatment,
The method includes a calculation step of calculating an appropriate amount of flocculant to be added so that the pollutant index of the mixed water is equal to or less than a predetermined appropriate value, and a coagulation and sedimentation treatment step of subjecting the obtained mixed water to coagulation and sedimentation treatment,
The relationship is
A proper amount of flocculant to be added to the wastewater A and a proper amount of flocculant to be added to the other wastewater are determined in advance by a flocculation test,
When the calibration relationship between the amount of flocculant added and the indicator of pollutants after the flocculant was added and the precipitation treatment was performed for the wastewater A and the other wastewater was obtained,
The relationship between the electrical conductivity of the wastewater A, the electrical conductivity of the other wastewater, the amount of the mixed water, and the mixing ratio of each wastewater in the mixed water, and the amount of flocculant to be added, which is obtained from the calibration relationship;
The wastewater treatment method, wherein in the coagulation and sedimentation treatment step, the calculated appropriate amount of coagulant to be added is added to the coagulation and sedimentation treatment device.

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