JPH11104656A - Apparatus for treating water containing inorganic contaminant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize an original treatment apparatus to calculate the amt. of alkali used at a time of the calculation of the concn. of SS formed by the neutralization of raw water from the use amt. of alkali in order to control a sludge return ratio without requiring separate exclusive machinery in treating water containing an inorg. contaminate by an alkali sludge method. SOLUTION: The raw water from a raw water tank 1 is preliminarily neutralized by a preparatory neutralization tank 2 and subsequently neutralized by alkali sludge in a neutralization tank 3 to form insoluble matter. This insoluble matter is subjected to flocculation treatment in a flocculation tank 4 and subsequently subjected to solid-liquid separation treatment in a sedimentation tank 5 to take out treated water. A part of separated sludge is returned to a reaction tank 6 and alkali is added to this sludge to form alkali sludge. The addition amt. of this alkali is calculated from the opening time of an alkali injection valve 9 in a recording/control part 10 and the amt. of formed SS is calculated on the basis of the calculated value to properly control the sludge return ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating inorganic contaminant-containing water, and more particularly, to neutralizing inorganic contaminant-containing water with an alkali to form an insolubilized product, and converting the resulting water into sludge and treating water. Inorganic contaminant-containing water treatment equipment that separates and returns part of the separated sludge to the neutralization process. Inorganic system that properly controls the amount of returned sludge, increases sludge concentration, and reduces sludge generation. The present invention relates to an apparatus for treating pollutant-containing water.

[0002]

2. Description of the Related Art In the treatment of metal ion-containing wastewater, there is an alkali sludge method as a method for obtaining high-concentration metal hydroxide sludge which is rich in concentration and excellent in dehydration. This method
This is a method in which an alkali is not directly added to a metal ion-containing wastewater but is mixed with a part of sludge separated in the treatment of the wastewater and added (Japanese Patent Publication No. 61-156).

[0003] In the alkaline sludge method, in order to stably obtain high-concentration sludge having excellent dehydration properties and maintain good quality of treated water, the amount of insolubilized matter (SS amount) generated by neutralization of raw water is reduced. It is necessary to maintain the ratio of returned sludge within a certain range. Thus, the present applicant has proposed a method for treating heavy metal-containing wastewater in which the amount of solid content of returned sludge previously mixed with alkali is set to 15 to 40 times the amount of insolubilized substances produced by the reaction between alkali and raw water. (Japanese Patent Laid-Open No. 5-57)
292).

[0004] In the present specification, the amount of SS (hereinafter, referred to as “SS”) generated by neutralizing wastewater containing metal ions as raw water is referred to as “SS”.
It may be simply referred to as “generation SS”. ) And the amount of returned sludge are referred to as “return ratio”. Specifically, the return ratio is calculated by measuring a factor shown in the following equation (1).

[0005]

(Equation 1)

As is apparent from the above equation (1), in order to maintain this return ratio within a certain range, it is necessary to respond to the change in the concentration of generated SS, that is, to adjust the metal ions in the raw water for generating SS. It is necessary to control the amount of returned sludge according to the change in the concentration of sludge.

[0007] In treating the metal ion-containing wastewater by the alkaline sludge method, the present applicant easily returns the amount of generated SS without using a sludge concentration meter having many problems in terms of measurement error and maintenance. As a method of performing good treatment while maintaining the ratio at a predetermined value, raw water is adjusted to pH 3
A method was previously proposed in which the metal ion concentration of raw water was determined from the amount of alkali required to bring the concentration to around 8.5, and the concentration of SS generated from raw water during neutralization was determined based on this value (Japanese Patent Laid-Open No. Hei 8- No. 24877).

That is, examples of the metal ion-containing wastewater to be treated include pickling wastewater for steel, electrogalvanizing wastewater for steel sheets, and washing wastewater from those processes. In addition to the ions, sulfuric acid and hydrochloric acid remaining without being completely used in the acid washing and plating steps are contained in the form of free acids, and the amount of metal ions can be determined only by the alkali amount used for pH titration. I can't ask.

Therefore, a certain amount of raw water is collected, and the amount of alkali required to adjust the pH to 3.0 is first determined (hereinafter, the process of adjusting the pH to 3 is referred to as “preliminary titration”).
In some cases. ). The alkali consumption required for this preliminary titration shall be used for neutralizing the free acid contained in the raw water.

FIG. 2 shows a pH titration curve of synthetic effluent containing sulfuric acid as a free acid at a concentration of 980 mg / L with NaOH. From the rising state of the curve in FIG. 2, neutralization reaction of free acid at pH 3 (H ₂ SO ₄ + 2NaOH → Na ₂ SO
₄ + 2H ₂ O) is completed.

Therefore, the amount of alkali used for the neutralization treatment from pH 3 to around 8.5 becomes the amount used for insolubilizing the metal ions by reacting with them (for example, FeSO _4).
+ 2NaOH → Fe (OH) ₂ + 2H ₂ O).

The amount of alkali used in the neutralization treatment for this insolubilization is determined by the type of the alkali, the metal ion to be insolubilized, and the like. You can ask.

For example, the ion to be insolubilized in raw water is Fe
If it is ²⁺ , the amount of SS generated by neutralization with caustic soda (NaOH) is calculated from the amount of alkali used in the neutralization treatment from pH 3 to around 8.5 by the following reaction formula:
It can be obtained from the following equation (2).

[0014]

(Equation 2)

In the following, N is calculated for calculating the generated SS concentration.
Required amount of alkali such as aOH (unit is mg-NaOH
/ L) may be referred to as “SS coefficient”. This SS coefficient differs depending on the type of the alkali and the ion to be insolubilized.
In the case of e ²⁺ insolubilization, the value is 0.89. The SS coefficients of other main ions to be insolubilized when NaOH or Ca (OH) ₂ is used as the alkali are as shown in Table 1 below.

[0016]

[Table 1]

By controlling the discharge amount of the sludge return pump in accordance with the calculated SS concentration calculated in this way and returning the required amount of sludge so that the return ratio is 8 to 40, the sludge is always returned. It is possible to stably and surely obtain sludge having a high concentration and excellent dewatering properties, and to maintain good quality of treated water.

In the method described in JP-A-8-24877, the amount of alkali used until the pH of the raw water becomes from 3 to about 8.5 is measured specifically as follows.

A pre-neutralization tank is installed in front of the neutralization tank for producing an insolubilized product by reaction with an alkali, and a certain amount of raw water whose pH has been adjusted to pH 3 in advance by this pre-neutralization layer is collected in a titration tank. , PH titration using an alkali of known concentration, p
The amount of alkali required to adjust to H8.5 is determined.

[0020]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 8-248 is disclosed.
According to the method described in Japanese Patent No. 77, the amount of SS generated by neutralization of raw water can be easily calculated, and the generated S
The sludge return ratio can be easily maintained at a predetermined value based on the calculated value of the amount of S. However, as described above, a predetermined amount of pre-neutralized water is collected from the pre-neutralization tank and subjected to pH titration. Requires a dedicated titration device such as a container or piping to measure the alkali amount separately from the original processing equipment, which complicates the equipment.Washing and titration of sensors and containers Maintenance such as replenishment of chemicals (alkali) is required, and there is a problem that operation management becomes complicated.

The present invention solves this problem, and when treating water containing inorganic pollutants by the alkali sludge method, to control the sludge return ratio, the concentration of SS generated by neutralizing raw water from the amount of alkali used to control the sludge return ratio. It is an object of the present invention to provide an inorganic contaminant-containing water treatment apparatus that can calculate the amount of the alkali used when calculating the water without using a dedicated device separately and using the original treatment apparatus. .

[0022]

According to the present invention, there is provided an apparatus for treating water containing inorganic contaminants, a first pH adjusting tank into which the water containing inorganic contaminants is introduced, and water contained in the water from the first pH adjusting tank. A second pH adjustment tank for insolubilizing the inorganic contaminants with the alkali or alkali and the contaminant insolubilizing agent to insolubilize the contaminants; A solid-liquid separation tank to be separated, sludge return means for returning a part of the sludge separated in the solid-liquid separation tank to the second pH adjustment tank, and sludge returned to the second pH adjustment tank or the second pH adjustment tank. An alkali supply unit for adding an alkali, and calculating the amount of the insolubilized product from the amount of alkali added by the alkali supply unit, and calculating and controlling the amount of sludge returned by the sludge return unit based on the calculated amount of alkali added. ·control Wherein the alkali supply means has an alkali injection valve, and the recording / control unit calculates an alkali addition amount based on the opening time of the alkali injection valve. It is characterized by the following.

In the present invention, the amount of alkali addition is determined based on the opening time of the alkali injection valve installed in the alkali supply means. Is calculated, and the generated SS amount is calculated based on the result, and the returned sludge amount can be easily controlled from the calculated generated SS amount and other data.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of an apparatus for treating water containing inorganic pollutants of the present invention. In FIG.
1 is a raw water tank, 2 is a preliminary neutralization tank (first pH adjustment tank), 3 is a neutralization tank (second pH adjustment tank), 4 is a coagulation tank, 5 is a sedimentation tank,
Reference numeral 6 denotes a reaction tank, 7 denotes an alkali storage tank, 8 denotes a polymer tank, 9 denotes an alkali injection valve, 10 denotes a recording / control unit, and 30 denotes a sludge concentration meter. In addition, 2A, 3A, 4A and 6A are stirrers,
B, 3B is a pH _{meter, P 1, P 2, P} 3, P 4, P 5 the pump, V is valve, F _1, F ₂ is a flow meter, the code of 11 to 23 is a piping.

In the method of this embodiment, water containing inorganic contaminants, which is raw water, is introduced into the pre-neutralization tank 2 via the pipe 11, the raw water tank 1, and the pipe 12. This raw water tank 1 is not always necessary, but by providing the raw water tank 1,
As described later, the raw water quality can be made uniform, the time lag of the control of the sludge return amount due to the fluctuation of the raw water quality can be reduced, and the supplied raw water amount can be stabilized.

The flow rate of the raw water is measured by the flow meter F ₁ , and the measured value is input to the recording / control unit 10. That is, in order to calculate the sludge return ratio described above, it is necessary to know the amount of treated water (the amount of raw water inflow). Therefore, it is preferable to provide a flow meter at an arbitrary position and always measure the inflow of raw water. However, normally, the amount of water supplied by the pump is almost constant, while the sludge return ratio is allowed to have a certain width. Therefore, the value of the amount of pump water supplied in advance to the recording / control unit as the amount of treated water is used. By recording it,
A flow meter F ₁ may be omitted.

In the pre-neutralization tank 2, the raw water is adjusted to pH 2.5 to 3 by alkali such as slaked lime injected from the alkali storage tank 7 through the pipe 21. The adjusted pH value of the pre-neutralization tank 2 is determined by the amount of free acid (for example, sulfuric acid,
Hydrochloric acid, nitric acid, etc.) or a pH that dissolves solids contained in raw water.
It may be in the range of 2.5 to 3, and therefore the pH of the pre-neutralization tank 2
Meter. 2B, in conjunction with the alkali supply pump P _2, pH of the bath in the liquid so that 2.5 to 3, the alkali is injected from the pipe 21. The injection of alkali into the preliminary neutralization tank 2 may be controlled by the recording / control unit 10.

When the pH of the raw water is as high as, for example, 4 or more, an acid such as sulfuric acid or hydrochloric acid is added to the pre-neutralization tank 2 to adjust the pH to 2.5 to 3 in the same manner. This is because the insolubilized material that has already precipitated in the raw water does not have the expected volume-reducing effect even if the sludge is returned. By adjusting to 0.5 to 3.0, once ionization (for example, Al (O
H) ₃ → Al ³⁺ , Zn (OH) ₂ → Zn ²⁺ , CaF ₂ →
^{_{F -, Ca 3 (PO 4}} ) 2 → PO 4 3-) to.

Generally, neutralization of free acid is instantaneously completed at the experimental level, but instantaneous neutralization is impossible in an actual apparatus. Therefore, the residence time in the pre-neutralization tank 2 is set to about 3 to 5 minutes. Is preferred.

The effluent from the pre-neutralization tank 2 is introduced into the neutralization tank 3 through a pipe 13. In the neutralization tank 3, a mixture prepared by mixing return sludge from the pipe 17 in the reaction tank 6 and alkali supplied from the alkali storage tank 7 through the pipe 20 (hereinafter referred to as “alkali sludge”) .) Is supplied from the pipe 22. The measured value of the pH meter 3B in the neutralization tank 3 is input to the recording / control unit 10, and the recording / control unit 10 controls the opening and closing of the alkali injection valve 9 to adjust the amount of alkali added to the reaction tank 6. Thereby, the tank liquid is controlled to a pH suitable for insolubilizing inorganic sludge by adding alkali sludge.

In the insolubilization treatment in the neutralization tank 3, if necessary, an insolubilizing agent for inorganic contaminants is added.
That is, the inorganic contaminants contained in the raw water according to the present invention include:
In addition to metal ions that can be insolubilized only with alkali, fluorine,
Some, such as phosphoric acid, carbonic acid, and sulfurous acid, require an insolubilizing agent such as an alkaline earth metal compound together with an alkali for pH adjustment. In this case, a necessary amount of the insolubilizing agent is appropriately added. .

The adjusted pH value of the neutralization tank 3 varies depending on the type of inorganic contaminants in the raw water, the type of insolubilizing agent, and the like.
It is generally in the range of 6-11. Specifically, when the ions to be insolubilized are Al ³⁺ and Fe ³⁺ , the pH is preferably 6 to 7,
F ^-, PO ₄ ^3- case is preferably pH 8-10, Ni
^In the case of ²⁺ and Cd ^2+, the pH is preferably 10 to 11.

Accordingly, the opening and closing of the alkali injection valve 9 such as a solenoid valve or an air-operated valve provided in the pipe 20 for supplying alkali to the reaction tank 6 is controlled so that the adjusted pH value is obtained.

In general, the alkaline injection valve 9 is not continuously opened until the predetermined pH is reached after the operation is started, but is opened / closed until the predetermined pH is reached.
Is repeatedly injected. The “open” / “close” time ratio is arbitrarily set by a timer.

In the present invention, the “open” time or the number of “open” / “close” cycles of the alkali injection valve 9 (actually, the “open” time obtained from this cycle number) is recorded.
Recorded in the control unit 10.

On the other hand, when the alkali injection valve 9 is "open", an alkali injection amount per unit time unique to the injection valve (hereinafter referred to as "intrinsic alkali injection amount") is obtained in advance, and this record is made. -Record it in the control unit 10. The recording / control unit 10 calculates the amount of alkali added to the reaction tank 6 based on the specific alkali inflow amount and the “open” time or “open” / “closed” cycle. The generated SS concentration is calculated by a calculation formula using a coefficient,
A generation SS concentrations further calculated, and the return sludge concentration inputted from the sludge concentration meter 30 will be described later, the return sludge flow rate inputted from the flow meter F _2, and a raw water flow rate inputted from the flow meter F ₁ of the aforementioned , Input to the above equation (1) to calculate the return ratio,
The return ratio to output a control signal of the discharge amount of the sludge return pump P ₄ to a predetermined value. Alternatively, a flow rate may be controlled by adjusting a degree of opening of a regulating valve. The return ratio depends on the quality of the raw water (the type of ions to be insolubilized in the raw water, coexisting ions), but usually, the return ratio is 15 to 40 in the treatment of metal ions, particularly Fe, Cr.
The return ratio is 15 to 20 for heavy metals such as Al, the return ratio is 20 to 30 for Al, and the return ratio is 30 to 50 when the insolubilized material is CaF ₂ , and the return ratio is 30 for Ca ₃ (PO ₄ ) ₂ . The return ratio is set to 30 to 100.

If the pressure applied to the alkali injection valve 9 fluctuates and the flow rate of the injection is fluctuated, a constant flow valve is provided on the inflow side or the outflow side of the alkali injection valve 9 so that the alkali in the open state is opened. By making the flow rate constant, it is possible to improve the calculation accuracy of the alkali addition amount from the opening time of the alkali injection valve.

As described above, in the neutralization tank 3, alkali sludge is always injected so as to have a pH suitable for insolubilizing inorganic contaminants. The amount of alkali injected into the tank 6 fluctuates according to the water quality fluctuation of the raw water. In the present invention, the fluctuating alkali injection amount is obtained from the operation state of the alkali injection valve. In general, the "open" / "close" time cycle of the alkali injection valve 9 can be variously set according to the standard of the injection valve. For example, “open” / “closed” = 10 seconds / 30 seconds, 30 seconds / 20 seconds, 20 seconds / 10 seconds, 20 seconds / 60 seconds. For such “open” / “closed” time cycle, in order to perform appropriate measurement in response to water quality fluctuation of raw water, practically 5 minutes or more, usually 10 minutes to 20 minutes Measure the opening time ("open" time or "open" / "close" cycle) of the alkali injection valve during any given time, grasp the alkali injection amount from this measured value, and average the value per unit time It is preferable to convert to In addition, absorb water quality fluctuation of raw water,
It is important to install the raw water tank 1 from the viewpoint of stabilizing the raw water quality, but in order to reduce the influence of the fluctuation of the raw water quality corresponding to such a measurement time, the capacity of the raw water tank must be measured as described above. Capacity that can ensure a residence time of at least three times the time, for example, 20 cycles of the “open” / “close” cycle of the alkali injection valve 9
When the average value per minute is obtained, the residence time of the raw water tank 1 is 60
It is preferred that the design is made to be at least minutes.

The effluent from the neutralization tank 3 is introduced into the coagulation tank 4 from the pipe 14, and is subjected to coagulation by the polymer injected from the polymer tank 8 through the pipe 23. This polymer injection amount is usually about 1 to 5 ppm. Although the flocculation tank 4 is not always necessary, it is practical to provide the flocculation tank 4 before the precipitation tank 5 to increase the size of the insolubilized material.

The coagulation solution is then supplied from the pipe 15 to the sedimentation tank 5.
And separated into solid and liquid. The separated water is discharged out of the system from the pipe 16 as treated water. A part of the settled sludge is discharged out of the system through a pipe 18, and the remaining part is returned to the reaction tank 6 through a pipe 17.

The sludge return concentration is measured by a sludge concentration meter 30 provided on a pipe 18 branched from the sludge return pipe 17. That is, a part of the returned sludge is extracted from the sludge return pipe 17 through the pipe 18, the concentration thereof is measured by the sludge concentration meter 30, and then injected into the reaction tank 6 through the pipe 19.

The measured value of the sludge densitometer is stored in the recording / control unit 1
Input to 0. In addition, the return sludge flow rate is the sludge return pipe 1
Measured in the flow meter F ₂ provided at 7, the measured value is also input to the recording and control unit 10.

In the present invention, the water containing inorganic contaminants to be treated includes heavy metal ions such as copper, zinc, nickel, cadmium, manganese, lead and iron, and heavy metal complexes of heavy metals and chelating agents. Wastewater containing metal ions,
Various inorganic systems such as metal ions, fluorine ions, and phosphate ions that can be insolubilized by the addition of an alkali or an alkali and an insolubilizing agent, such as plating wastewater and other fluorine-containing wastewater and phosphorus-containing wastewater. Wastewater containing pollutants.

Examples of the alkali to be added to these wastewaters include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, slaked lime, magnesium hydroxide, barium hydroxide, and strontium hydroxide. Examples of the agent include calcium chloride and magnesium chloride. Examples of the polymer include polyacrylamide and a partial hydrolyzate thereof.

The processing apparatus shown in FIG. 1 is an example of the embodiment of the present invention, and the present invention is not limited to the one shown in the drawings unless it exceeds the gist.

For example, the alkali to the neutralization tank (second pH adjusting tank) 3 is added to the returned sludge by mixing it.
May be added directly. In this case, the reaction tank 6 becomes unnecessary, and the sludge returned from the precipitation tank 5 is directly added to the neutralization tank 3.

According to the apparatus for treating inorganic contaminant-containing water of the present invention, a dedicated apparatus for measuring the amount of added alkali is not required, and the measurement for calculating the amount of added alkali from the treatment apparatus is not required. Value, and based on this measurement the generated S
Calculate the amount of S, maintain the return ratio at a predetermined value based on the amount of generated SS, obtain high-concentration sludge with excellent dehydration properties, and obtain clear and high-quality treated water stably and reliably. Can be.

[0049]

As described above in detail, according to the apparatus for treating inorganic contaminant-containing water of the present invention, in treating the inorganic contaminant-containing water by the alkali sludge method, the sludge return ratio is controlled. In addition, the amount of alkali used when calculating the SS concentration generated by the neutralization of raw water from the amount of alkali used can be obtained by using the original processing apparatus without the need for a special device separately. And maintenance and operation management can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a treatment apparatus for water containing inorganic pollutants of the present invention.

FIG. 2 is a graph showing a pH titration curve of synthetic wastewater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Preliminary neutralization tank 3 Neutralization tank 4 Coagulation tank 5 Sedimentation tank 6 Reaction tank 7 Alkaline storage tank 8 Polymer tank 9 Alkaline injection valve 10 Recording / control part 30 Sludge concentration meter

Claims (1)

[Claims] 1. The first p into which water containing inorganic contaminants is introduced.
An H-adjustment tank; a second pH-adjustment tank for reacting inorganic contaminants contained in water from the first pH-adjustment tank with alkali or an alkali and a contaminant-insolubilizing agent to insolubilize the contaminants; A solid-liquid separation tank that separates insoluble material contained in the water from the tank as sludge from the treated water, and a sludge return unit that returns a part of the sludge separated in the solid-liquid separation tank to the second pH adjustment tank. An alkali supply means for adding alkali to the second pH adjustment tank or sludge returned to the second pH adjustment tank; and an amount of the insolubilized product calculated from the amount of alkali added by the alkali supply means. A recording / control unit that calculates and controls the amount of sludge returned by the sludge return means based on the sludge return means. The alkali supply means has an alkali injection valve. Recording and control unit, the processing unit of the inorganic contaminants containing water and calculates the alkali addition amount based on the opening time of the alkali injection valve.