JP2003062406A - Sludge-discharge controlling method for sludge in sedimentation pond of water-purifying process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controlling method capable of efficiently removing a sludge in a precipitation pond and selectively discharging a high concentration sludge without reducing a function of the sedimentation pond while solving problems that in a sludge- discharge control in the sedimentation pond, a grasp of an amount of the deposited sludge in the sedimentation pond is difficult, an appropriate operation timing and operating period of a sludge-discharge equipment can not be determined, there is a bad influence to finally treated water at the time of fluctuation of an amount of raw water and a turbidity because the sludge-discharge equipment is intermittently operated for a constant time, a deposited position and a deposited amount of the sludge cannot be grasped and a low concentration of sludge is possibly discharged. SOLUTION: An average grain diameter and an average number concentration of floc in flowing-out water in a floc-formation pond are continuously measured and when a flowing-out floc volume integration value per a calculated unit time exceeds a removal permission deposition value in the sedimentation pond, a command signal of an operation starting timing and an operation time is transmitted to a sludge- discharge means controlling device and the sludge deposited in the sedimentation pond is discharged by operating a sludge-discharge mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sludge mud control in a sedimentation tank during a coagulation sedimentation treatment process in a water purification process.

[0002]

2. Description of the Related Art FIG. 4 is a conceptual diagram showing an example of a coagulation sedimentation treatment process in a water purification plant. In FIG. 4, the coagulation-sedimentation treatment is performed by adding a coagulant 32 to the raw water 31 to generate a fine floc, a flocculation pond 34 for growing the generated microflocs, and a growth floc by gravity sedimentation. It is performed by a settling basin 35 for removing sedimentation and a filter basin 36 for removing unremoved flocs in the settling basin 35.

Of these, the settling basin plays an important role in determining the quality of the final treated water, and has three functions of settling, buffering and sludge. Regarding the functions of sedimentation and buffer, the sedimentation tank structure and the first stage of the sedimentation tank (flock formation tank)
It is almost determined by the processing method up to. On the other hand, the function of the sludge, that is, the appropriate bottom bottom sludge discharge considering the history of raw water quality and the history of operating conditions and the structure of the sedimentation basin directly affects the processability of the latter stage. However, at present, there are few practical means for measuring the sludge condition of the sedimentation tank, and the sludge scraper of the existing sedimentation tank is intermittently operated without limitation by human intuition and experience. Moreover,
The sludge discharge from the sludge discharge port is performed by opening an on-off valve installed at the discharge port for a certain period of time (for example, by setting a timer).

[0004]

[Problems to be Solved by the Invention] Generally, a water purification plant produces a certain amount of purified water every day. Therefore, it is clear that the amount of sludge generated changes depending on the turbidity of the raw water, which changes daily.In particular, during the rainy season and the snowmelt season, the frequency of treatment of high-turbidity raw water increases, so that it is inevitably higher than normal. A lot of sludge is generated. Under the present circumstances where such fluctuations in the amount of sludge generation cannot be quantified, it is almost difficult to perform an ideal sludge operation in which high concentration sludge is discharged in a short time. Therefore, the above-mentioned prior art has the following problems. (1) Since it is difficult to grasp the amount of sludge settled in the sedimentation basin, it is impossible to grasp the proper operation timing and operation time of the sludge discharge equipment. (2) Since the sludge discharge equipment is operated intermittently for a certain period of time,
Fluctuations in raw water volume and turbidity may adversely affect the final treated water. (3) Since the sludge sedimentation position and the amount of sedimentation cannot be grasped, sludge with a relatively low floc concentration may be discharged.

The present invention has been made to solve the above problems, and its purpose is to remove sludge from the bottom of a sedimentation pond efficiently and efficiently without lowering the function of the sedimentation pond. An object of the present invention is to provide a sludge control method for selectively sludge sludge having a relatively high concentration.

[0006]

In order to solve the above problems, the sludge control method of the present invention uses the following two methods. The first method, by simultaneously measurable means the average particle diameter D _n of flocs in the effluent of the flocculation basin average number and concentration N _n consecutive measurement, the flock average particle size D _n
And the average number concentration N _n , the average floc volume ratio of the outflow water of the floc formation pond is calculated, and the average floc volume ratio is multiplied by the outflow water amount Q _OUT of the floc formation pond per unit time to flow out per unit time. When the integrated value V _SUM of the floc volume to be exceeded exceeds the allowable accumulation value V _UP preset so as not to interfere with the removal function in the sedimentation basin, the operation start time is set to the sludge removal means control device installed in the sedimentation basin. And a command signal of operation time are transmitted, and the sludge accumulated in the sedimentation tank is discharged by operating the sludge discharge mechanism.

The second method is a means capable of simultaneously measuring the average particle size D _n of the flocs in the outflow water of the floc formation pond, the average number concentration N _n, and the average settling velocity of the flocs calculated from the average particle size. Continuous measurement is performed to predict the position where the flocs reach the bottom of the sedimentation basin and the amount of sedimentation based on the average settling velocity, the amount of outflow water from the floc formation basin per unit time, and the size of the sedimentation basin. This is a method of selectively operating the sludge removal mechanism of the above to discharge sludge from the sedimentation tank.

As described above, in the sludge control method of the present invention, sedimentation is performed in the sedimentation basin based on the particle size of flocs in the effluent of the flocculation basin, the number of flocs per unit volume, the average sedimentation velocity, and the particle size distribution. It is necessary to calculate and estimate the accumulated amount of flocs and sedimentation distribution, and operate the existing sludge removal mechanism of the sedimentation basin so as not to exceed the maximum allowable amount of sludge that can be calculated in advance from the size of the sedimentation basin and the flow rate of treated water. You can decide when and when. Furthermore, it is possible to limit the operation and operation range of the sludge discharge mechanism, to efficiently discharge the sludge accumulated in the sedimentation tank, and further to minimize the precipitation treated water discharged simultaneously with the sludge.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described below based on Examples. FIG. 1 is a process cross-sectional conceptual diagram showing a rapid mixing basin 1, a floc formation basin 2, a sedimentation basin 3, a sludge discharging mechanism 4, and a sludge discharging mechanism control device 5 in a water purification process to which the method of the present invention is applied.

First, the sedimentation velocity W of flocs formed in the water purification process is determined by the Stokes equation (1). W = (1/18) · g · {(ρ _s −ρ) / μ} · D ² ───── (1) where g is the acceleration of gravity, ρ _s is the floc density, and ρ is the water density. , Μ is the viscosity coefficient of water, and D is the diameter of the floc.

However, in water purification treatment, since water is contained in the gaps of the flocs without exception, the density ρ _s −ρ in the equation (1) can be generally approximated by the equation (2), and therefore the equation (1) is given by the equation (3). Can be expressed as ρ _s −ρ = 1 / D ^1.5 ────────────────── (2) W = (1/18) ・ g ・ D ^0.5 / μ─────── ─────── (3) On the other hand, in the sedimentation tank 3 in Fig. 1, the sedimentation speed W ₀ (surface load factor) of the minimum particle size (slow sedimentation speed) of flocs completely removed from the sedimentation tank Is expressed by equation (4).

W ₀ = Q _in / A ────────────────────── (4) Here, A is the bottom area of the sedimentation basin 3, and Q _in is sedimentation. It is the amount of water flowing into the pond. At this time, the removal rate of flocs having a sedimentation velocity W ≧ W ₀ that is greater than the sedimentation velocity W ₀ of the sedimentation basin 3 is 100%, and therefore, as shown in equation (5) from equations (3) and (4),
The minimum floc particle diameter D _{min at the} initial stage of inflow into the settling basin capable of completely removing the precipitate in the settling basin 3 is obtained.

[0013]       D_min= {(Q_in/ A) ・ (18μ / g)}²─────── (5) Therefore, in the first method, in FIG.
The sensor 6 installed directly in the pond runoff water
Average particle size D of flocs discharged from Ku formation pond_n, Average number concentration
N_nContinuously measured at the same time, sensor measurement value 7 (average grain
Diameter D_nAnd the average number concentration N_n) To computer 8 each time
Is entered. Also, the measured value θ with the water temperature gauge 9_nIs similar to
It is input to the computer 8 by iming. At this time, computer 8
, The unit measured by the flowmeter 10 in front of the mixing basin
Raw water intake per unit time Q_RAnd the floc formation pond style
Water outflow Q_OUTAnd settling basin inflow Q_inAre all equal
D obtained from equation (5)_minOn the other hand, D_n≧ D_minTo
Flock average particle size D _nSelect and select only
Total flocs deposited in the sedimentation basin by the treatment procedure shown.
Integrated value V of product_SUMIs calculated.

Each of the calculations shown in FIG.
This is performed using the equation (8). V _n = π ・ D _n ³・ N _n / 6 ───────────── (6) V _UNIT = π ・ D _n ³・ N _n・ Q _OUT / 6 ───── ───── (7) V _SUM = ∫V _UNIT ───────────────────── (8) T ₁ = V _SUM / Q ₃ ───── ─────────────── (9) where V _n is the floc volume, V _UNIT is the floc volume per unit time deposited in the sedimentation tank 3, and V _SUM is the sedimentation tank 3
The integrated value of the total flock volume accumulated on the surface, T ₁ is the sludge discharge time, and Q ₃ is the sludge discharge flow rate per unit time.

Further, in the computer 8, V which is sequentially calculated
_SUM is the value V _UP preset by the operator (however,
When the preset value V _UP ≤ maximum sludge deposit allowable amount V _MAX in the sedimentation basin is exceeded, the sludge discharge time T ₁ is determined, and operation start and operation time are set for the sludge discharge mechanism controller 5 already installed in the sedimentation basin. Command signal 11 of
As a result, the sludge 13 accumulated in the sedimentation tank 3 is efficiently discharged. Further, after the discharging is completed, the integrated value V _SUM of the total flock volume stored in the computer 8 is reset and the counting is started again from 0.

An example of the sensor for the above-mentioned application is
For example, Japanese Patent Application No. 2-43064 "A plurality of compounds contained in a liquid
And apparatus for detecting the agglomeration process of
It can be applied. Next, regarding the second method, the first
The method will be described with reference to FIGS. Second way
Then, in the same way as the first method, the settling tank is calculated by the computer 8.
The process shown in FIG.
Total Flock Volume Product of Sedimentation Tank Sediment Calculated Sequentially by Procedure
Calculated value V_SUMHowever, the value V preset by the operator_UPOver
The sludge discharge time is determined by the formula (5).
D found_minAgainst D_n≧ D _minMeet Flock Taira
Average particle size D_nAfter selecting and selecting only
The following process is performed to limit the number of positions. This process
Is the average particle size of floc D _nAverage number concentration measured simultaneously with
N_nAnd the sedimentation velocity W obtained by the equation (3)_nAnd by
Using the derived equation (10), the floc in the sedimentation tank 3 is
Estimated distance of Ku (bottom position in sedimentation tank) X_nCalculate
It Figure 3 shows the sedimentation in the depth (water treatment progress) direction of the rectangular sedimentation tank.
Flock volume cumulative distribution for Tonoike cross section XX '
It shows a schematic diagram showing the actual dimensions of the rectangular sedimentation tank.
A similar diagram is sequentially calculated and created according to. In addition, the above
The distribution category is determined in advance according to the arrangement of the sludge removal mechanism in the sedimentation tank.
Keep it.

[0017]       X_n= (Q_in/ B) ・ (18 ・ μ) / (g ・ D_n ^0.5) ─── (10) Here, B is the width of the sedimentation tank 3. In this way
In the second method, the sludge discharge timing determined by computer 8
At the sedimentation basin, the accumulated volume of flocs V_SUM
Volume product of which the ratio of the flock exceeds the preset value
Position X which is the mathematical distribution_{V MAX}Sludge outlet valve 12 in the vicinity
Is selected and determined on the computer 8, and the existing
Sludge discharge valve for sludge discharge mechanism controller 5
12 operation start and operation time T₂Command signal 14 of
Believe that the sludge 13 is efficient from the position where the amount of sediment is relatively large.
To be discharged. Here, the operating time is T₂The settling pond
Total floc volume accumulated value V accumulated in 3_{SU M}Against
Position X_{V MAX}Of the volume integrated value of the₁To
Multiply the value. Also, after the discharge is completed, it is deposited in the sedimentation tank 3.
Flock volume integrated value V_SUMIs the V_SUMDischarged from
Position X_{V MAX}The value obtained by subtracting the volume integrated value of
And start counting. In addition, here, sludge discharge mechanism
The operation of the outlet valve, which is one of the
Regarding operations such as gathering machines, limited operations depending on the deposition position
Is possible.

[0018]

As described above, since there are few practical means for measuring the sludge condition of the sedimentation tank, there is no sludge control method for efficiently discharging sludge. According to the present invention, as described in the embodiment,
Flock formation pond The integrated amount of total floc volume settled in the settling basin and the sludge in the water flow direction are measured using a means for continuously measuring the particle size and number of flocs per unit volume in the outflow water and a means for calculating the average settling velocity. The optimum time and time to operate the existing sludge removal mechanism by calculating the integrated value of the volume distribution so as not to exceed the maximum allowable sludge accumulation amount that can be calculated in advance from the size of the sedimentation tank and the flow rate of treated water. Can be determined. Moreover, the operation range of the sludge discharge mechanism can be limited to the vicinity of the position where the sludge accumulation amount is relatively large, so that the sludge accumulated in the sedimentation tank can be discharged at a high concentration and the treated water discharged at the same time as the sludge can be minimized. It can be limited.

[Brief description of drawings]

FIG. 1 is a process cross-sectional conceptual diagram of a water purification process to which the method of the present invention is applied.

[Fig. 2] Flow chart for calculating the integrated value of the floc volume deposited in the sedimentation tank

FIG. 3 is a cross section X of the sedimentation basin shown in FIG. 1, which is parallel to the flow direction of water.
-X 'is a schematic diagram showing the state of the flock volume cumulative distribution

[Figure 4] Conceptual diagram showing the coagulation / precipitation / filtration process of the water purification plant

[Explanation of symbols]

1: Rapid mixing pond 2: Flock formation pond 3: Settling tank 4: Sludge removal mechanism 5: Sludge removal mechanism control device 6: Sensor 7: Sensor measurement value 8: Calculator 9: Water thermometer 10: Flow meter 11: Command signal 12: Sludge outlet valve 13: Sludge 14: Command signal 31: Raw water 32: Flocculant 33: Rapid mixing pond 34: Flock formation pond 35: Settling tank 36: Filter pond

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tokio Oto             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd.

Claims (2)

[Claims] 1. An average particle size of aggregates (hereinafter referred to as flocs) in the effluent of the floc formation pond in a coagulation sedimentation treatment process of a water purification system comprising a mixing pond, a floc formation pond, a sedimentation pond, and a filtration pond. And the average number concentration are measured continuously by means capable of simultaneously measuring, and the average floc volume ratio of the outflow water of the floc formation pond is calculated from this floc average particle size and the average number concentration. When the integrated value of the volume of flocs flowing out per unit time, which is obtained by multiplying the amount of outflow water from the floc formation pond per unit, exceeds the preset allowable sedimentation value that does not interfere with the removal function in the sedimentation pond, Send a command signal of the operation start time and operation time to the installed sludge control device,
A method for controlling sludge sludge sludge discharge in a water purification process, characterized in that sludge flocs (hereinafter referred to as sludge) accumulated in the settling tank are discharged by operating a sludge discharging mechanism. 2. The average particle size, the average number concentration and the average particle size of the flocs in the effluent water of the floc formation pond in the coagulation sedimentation treatment process of a water purification system comprising a mixing pond, a floc formation pond, a sedimentation pond and a filtration pond. The average settling velocity of flocs calculated from the above is continuously measured by means capable of simultaneously measuring, and from the average settling velocity and the amount of outflow water of the floc formation pond per unit time and the size of the sedimentation pond, the flocs are transferred to the bottom of the sedimentation pond. A method for controlling sludge sludge discharge in a water purification process, which predicts the position where sedimentation reaches and the amount of sedimentation, and selectively operates the sludge discharge mechanism near the position where the amount of sedimentation is large to discharge sludge from the sedimentation pond. .