JP2002159965A - Pressure floatation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure floatation device capable of maintaining the water level inside a floatation vessel within a specified range even when a rapid increase in flow rate of raw water is caused, and discharging highly concentrated scum having a stable concentration. SOLUTION: A raw water treatment process using this pressure floatation device comprises: allowing raw water and pressurized water to flow into a floatation vessel from an inflow pipe 2 through a feed well 3 to perform solid- liquid separation of the raw water, raking up floated scum within the floatation vessel with a scum rake 4 so as to allow the raked scum to fall into a sludge discharge box 5 for the scum to discharge the scrum; making treated water pass through a space between a baffle wall 8 and the bottom surface of a floatation vessel body 1 and then discharging the treated water through a treated water discharge pipe 6 to the outside of the device, and controlling a pump 7 placed in the treated water discharge pipe 6 so as to maintain the water level within the vessel body 1 detected by a water level gage 9, at a constant level by using an arithmetic unit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for subjecting water containing suspended substances (SS) to pressurized flotation and separation from water containing the suspended substance (SS). The present invention relates to a pressure flotation device capable of discharging scum.

[0002]

2. Description of the Related Art As one method of treating water containing SS,
A pressurized flotation device mixes raw water with pressurized water and supplies it to the floating tank, where the SS in the raw water is adsorbed by the micro air and floats on the water surface, and is raked and discharged by a scum lake (schema). is there.

[0003] Raw water introduced into the floating tank is often sent from the raw water tank to the flocculation treatment tank via a pump, where a flocculant is added to generate flocs and then introduced into the floating tank. The amount of water sent from the raw water tank to the coagulation tank varies depending on the level of the water in the raw water tank, and is usually ± 20 to 3 times the average amount.
It fluctuates about 0%.

Since the water in the flocculation tank flows into the floating tank due to overflow, the amount of water flowing from the flocculation tank to the floating tank fluctuates in accordance with a change in the amount of water supplied from the raw water tank to the flocculation tank. Will do. The treated water in the floating tank is configured to flow out of the floating tank due to the head difference, so if the diameter of the treated water discharge pipe from the floating tank is increased, the flow rate of the raw water will increase significantly. Even so, the fluctuation range of the water level in the floating tank is small.

[0005]

If the diameter of the treated water discharge pipe is increased, the construction cost of the pressure flotation device increases. For this reason,
In designing the pressurized flotation device, the diameter of the treated water discharge pipe is limited to a range that can cope with a normal fluctuation of the inflow water amount. As a result, when there is a significant increase in the inflow volume exceeding the normal inflow volume, the inflow volume exceeds the treated water discharge volume, the water level in the floating tank increases, and the amount of raw water flowing out with the scum increases. The amount of mud increases significantly. Further, there is a possibility that raw water or scum may flow out by overflowing the tank wall of the floating tank.

The present invention solves such a problem, and keeps the water level in the floating tank within a certain range even if the flow rate of the raw water is greatly increased without unnecessarily increasing the diameter of the treated water discharge pipe.
An object of the present invention is to provide a pressure flotation device capable of discharging high-concentration scum having a stable concentration.

[0007]

The pressure flotation apparatus of the present invention comprises a flotation tank, a supply means for supplying raw water and pressurized water to the flotation tank, and a treated water discharge means for taking out treated water out of the tank. A pressurized flotation device comprising: a measuring means for measuring a water level of the flotation tank; and a control means for controlling a discharge amount of the treated water or a supply amount of the raw water based on the measured water level. Is what you do.

According to such a pressurized flotation device, the fluctuation of the water level in the flotation tank is suppressed without increasing the diameter of the treated water discharge pipe, and it is possible to always discharge high-concentration scum.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the pressure flotation device of the present invention.

The tank body 1 having a cylindrical peripheral wall is formed in a conical shape in which the bottom becomes lower toward the center, and a discharge pipe 6 for treated water is connected to the center of the bottom. A water discharge pump 7 is provided. Note that the inflow end of the discharge pipe 6 projects slightly vertically upward from the bottom surface of the tank body 1 so as to prevent inflow of settling scum.

A feed well 3 is provided upright above a discharge pipe 6 at the center of the tank body 1, and a raw water inflow pipe 2 is connected to a lower portion of the feed well 3. A pressurized water valve is connected to the raw water inflow pipe 2. Pressurized water inflow pipes (both not shown) are connected.

The bottom surface of the feed well 3 is sealed, and the water flowing into the feed well 3 from the inflow pipe 2 flows only upward.

The raw water inflow pipe 2 is tangentially connected to the feed well 3. By arranging the raw water inflow pipe 2 tangentially to the feed well 3 in this manner, the mixed water of the raw water and the pressurized water flowing into the lower part of the feed well 3 turns along the inner peripheral wall of the feed well 3. As a result, it is possible to prevent short-circuiting from flowing to the upper portion of the feed well 3.

Further, a treated water straightening plate 8 is provided in the tank body 1. The treated water straightening plate 8 is arranged so as to surround the outside of the feed well 3 and is attached to the lower end of the feed well 3. The treated water straightening plate 8 is formed of a substantially chin-shaped plate that is inclined so as to be lower toward the outer peripheral side.

The outer peripheral end of the treated water straightening plate 8 is close to the bottom surface of the tank body 1, and the treated water flows between the treated water straightening plate 8 and the tank body 1.
To the discharge pipe 6 after passing through the bottom surface of the container.

A scum lake 4 is installed on the upper part of the tank body 1. A scum drain box 5 is provided at the upper part of the side wall surface of the tank body 1, and a drain pipe is connected to the scum drain box 5.

A water level gauge 9 is provided for detecting a water level in the tank body 1 and a detection signal of the water level gauge 9 is used as an arithmetic unit 10
Has been entered. The computer 10 controls the rotation speed of the treated water discharge pump 7.

The water level gauge 9 is of a type that extracts a water level as an electric signal, such as a pressure type or an ultrasonic type. The electric signal indicating the water level is input to the computer 10 including the inverter, and the discharge amount of the treated water discharge pump 7 is changed by changing the frequency, so that the water level in the tank body 1 can be kept constant.

Raw water and pressurized water flow from the inflow pipe 2 through the feed well 3 into the floating tank, where solid-liquid separation is performed. The mixed water flows in the tangential direction to the feed well 3 and rises in the feed well 3 as a swirling flow, so that a short circuit of the mixed water is prevented. Feedwell 3
The mixed water of the raw water and the pressurized water that has risen as a swirling flow in the inside does not directly blow up on the water surface, but forms a uniform, gentle radial flow from the upper end of the feed well 3 into the tank body 1. And undergoes flotation separation.

The scum that has floated in the floating tank is scraped by the scum lake 4, dropped into the scum discharge box 5, and discharged.

On the other hand, the treated water separated from the scum is discharged through a treated water discharge pipe 6 through a gap between the treated water straightening plate 8 and the bottom surface of the tank body 1.

The computer 7 controls the pump 7 so that the water level in the tank 1 detected by the water level meter 9 is kept constant.

For example, 100 m of average treated water³/ Hr addition
80-120m in pressure flotation device ³/ Hr inflow
When there is fluctuation, control the water level fluctuation of the water surface to ± 1cm
Between water level and inverter output frequency for
An operation example such as the pump water discharge amount is shown below. Ports used here
The pump is 100m at 55Hz³/ Hr pump
Yes, the relationship between the water level and the discharge amount is set as shown in Table 1.

[0024]

[Table 1]

The treated water is discharged at a rate of 100 m ³ / hr between the contacts HL. If the water level falls below M, the amount of inflow water has also decreased, and the amount of discharge will be reduced to 90 m ³ / hr. If it reaches the LL point, it is further reduced to 80 m ³ / hr, but it is possible that the raw water pump is stopped.

When the water level rises, when the temperature exceeds the HH point, the treated water pump may become abnormal and may not output a discharge amount corresponding to the frequency. Therefore, an alarm is issued and the raw water pump is stopped at the same time.

In the above embodiment, the pump 7 is provided in the treated water discharge pipe 6, and the whole amount of treated water is discharged by the pump 7, but most of the treated water (for example, 60 to 80%)
May be discharged by the head difference of the tank body 1, and the remaining may be discharged by a pump. FIG. 2 shows an example thereof.
The second treated water discharge pipes 11 and 12 are arranged in parallel with the treated water discharge pipe 6.
The treated water discharge pipes 11, 12 are provided with a pump 7 '.
Is interposed. Part of the treated water in the tank 1 flows in the order of the treated water discharge pipe 11, the pump 7 ', and the treated water discharge pipe 12, and is sent to the treated water discharge pipe 6. The amount of water discharged from the pump 7 'is calculated by the computer 10 so that the water level in the tank 1 is constant.
Is controlled by As the pump 7 ', a pump smaller than the pump 7 is sufficient.

FIG. 3 shows an example of a pressure flotation apparatus in which part of the treated water is used as pressurized water.

In the pressure flotation apparatus shown in FIG. 3, a treated water intake pipe 13 is branched from a treated water discharge pipe 12, and a constant flow valve 14 is provided in the treated water intake pipe 13. For example, about 15 to 30% of the total treated water amount is constantly collected from the separation pipe 13 and sent to the pressurized water producing apparatus.

In the present invention, although not shown, the water level in the tank 1 may be detected to control the raw water pump, thereby keeping the water level in the tank constant.

[0031]

As described above, according to the present invention, in the pressurized flotation device for separating treated water and scum, even if the amount of inflow water fluctuates, the fluctuation of the water level is small, so that the scum of a certain concentration can be discharged. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a pressure flotation device of the present invention.

FIG. 2 is a longitudinal sectional view showing another embodiment of the pressure flotation device of the present invention.

FIG. 3 is a longitudinal sectional view showing still another embodiment of the pressure flotation device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tank body 2 Raw water inflow pipe 3 Feed well 4 Rake 5 Scum drain box 6 Treated water discharge pipe 7 Pump 8 Treated water straightening plate 9 Water level gauge 10 Computing machine 11, 12 Treated water discharge pipe 13 Treated water intake pipe 14 Constant flow rate valve

Claims (1)

[Claims] 1. A pressurized levitation apparatus comprising: a levitation tank; supply means for supplying raw water and pressurized water to the levitation tank; and treated water discharge means for taking out treated water out of the tank. And a control means for controlling the discharge amount of the treated water or the supply amount of the raw water based on the measured water level.