JPH1119660A - Waste water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a device structure, to reduce a maintenance administration cost and an operation cost and to enable the underground laying of a flocculating and settling device as to the structure and agitating means of the flocculating and settling device used as the third treating device of a waste water treatment device. SOLUTION: A quick stirring tank 6 and a slow stirring tank 7 divided with a partition 5 are provided in a vessel. An inlet 11 of water to be treated is provided in the quick stirring tank 6 and an outlet 17 to a settling tank is provided in the slow stirring tank 7. A diffusing pipe 15 is arranged along the under side of the partition 5 in the quick stirring tank 6. The inlet 11 is opened in the direction promoting a revolving flow, since the revolving flow is generated in the quick stirring tank 6 by the diffusing air rising along the partition 5 from the diffusing pipe 5. The vessel 1 has a horizontal cylindrical shape, the partition 5 is provided in the diameter direction of the vessel, a communicating hole 8 communicating the quick stirring tank 6 and the slow stirring tank 7 is provided at the lower part of the partition and a slow diffusing pipe 16 is provided at the bottom part of the slow stirring tank 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus provided with a coagulation / sedimentation apparatus, and more particularly to a wastewater treatment apparatus characterized by a means for stirring treated water in a stirring tank of the coagulation / sedimentation apparatus and their arrangement.

[0002]

2. Description of the Related Art There are various types of wastewater treatment apparatuses according to the type of wastewater to be treated and the required quality of discharged water. Usually, a plurality of apparatuses are used in combination. . A small-scale wastewater treatment system for a general house is equipped with a primary treatment device that performs sedimentation and anaerobic treatment, and a secondary treatment device that decomposes organic matter in an aeration tank. It is discharged through. In large-scale septic tanks used for apartment houses and the like, the effluent water quality standards are becoming stricter, and thus the treated water subjected to aeration is subjected to a coagulation sedimentation treatment called tertiary treatment before being discharged.

[0003] The coagulation / sedimentation treatment is usually carried out using a rapid stirring tank, a slow stirring tank and a precipitation tank. The rapid stirring tank is provided with a flocculant supply means and a stirring means, and the suspension is flocculated by adding aluminum salts or iron salts such as alum as a flocculant to the treated water in the tank and stirring. Allow flocs to form. In the slow stirring tank, flocs formed in the rapid stirring tank are aggregated into large flocs while gently stirring the treated water, so that the sediment is easily settled. The treated water in the slow stirring tank is sent to the precipitation tank through a baffle tube,
Here, after the floc is precipitated, the supernatant is discharged. By such a treatment, the quality of the discharged water can be increased to a quality close to that of tap water.

In the rapid stirring tank, strong stirring is required in order to quickly and uniformly mix the supplied flocculant and the treated water and to cause the suspensions to collide with each other to form flocs quickly. It is. Therefore, as a stirring means, conventionally, as shown in FIG. 4, a mechanical stirring means in which a stirring blade 52 attached to a stirring shaft 51 is rotated by an electric motor 53 has been adopted. In FIG. 4, 6 is a rapid stirring tank, 7 is a slow stirring tank, 5 is a partition partitioning the rapid stirring tank 6 and the slow stirring tank 7, and 11 is an inlet of treated water after the secondary treatment. ,
12 is a flocculant supply port, 13 is a pH adjuster supply port, and 54 is a baffle tube.

The treated water flowing into the rapid stirring tank 6 from the inlet 11 is provided with a coagulant and is stirred by the stirring blades 52.
The suspension flows into the slow stirring tank 7 from the communication hole 8 provided in the lower part of the partition wall 5 in a state of forming small flocs. A baffle plate 55 for suppressing the flow in the tank is provided on the side wall of the slow stirring tank 7. Due to the treated water flowing from the rapid stirring tank 6, a gentle water flow is generated in the slow stirring tank 7, and the flocs collide with each other in this gentle water flow and aggregate to grow into large flocs. The outlet 17 of the baffle pipe 54 is opened below the surface of the slow stirring tank, and sends the treated water to the sedimentation tank together with the floating flocs on a gentle water flow. The sedimentation tank is larger in volume than the rapid stirring tank and the slow stirring tank, and the floc is settled and removed while the treated water remains in the sedimentation tank, and the supernatant is discharged.

When the pH of the treated water is biased, p
A pH adjuster is supplied from the H adjustor supply port to neutralize the pH adjuster. The reason why the outlet 17 of the baffle pipe 54 is opened below the water surface is to prevent oil and the like floating in the upper layer of the treated water from flowing into the settling tank. These suspensions are trapped in flocs over time and flow through a baffle tube to a settling tank.

[0007]

The mechanical stirring device is used as a stirring means for the rapid stirring tank because it is necessary to mix the treated water and the supplied chemical as quickly and uniformly as possible. To achieve this, it is common practice to provide a number of stirring blades to increase the rotation speed.
In the current rapid stirring tank, it is required that sufficient stirring and mixing be performed in any use condition, and it is considered that a mechanical stirring device must be used for that purpose.

[0008] However, the mechanical stirring device requires ancillary equipment such as a motor, its control device, and a switchboard, and requires maintenance and inspection and replacement of damaged parts. Therefore, it is difficult to install the mechanical stirring device underground. Generally, the primary and secondary treatment devices can be buried underground, and a tertiary treatment settling tank can also be buried underground. However, when the stirring tank is installed on the ground, the inflow water stirs the water in the sedimentation tank due to a drop between the ground and the underground, and impedes the precipitation treatment. Therefore, if the stirring tank is provided on the ground, the subsequent settling tank must be provided on the ground, and the large capacity of the settling tank requires a large area, which hinders effective use of land.

Further, the mechanical stirring device has a large number of parts,
It also requires electrical equipment and is expensive due to its complex structure. As a result of the complicated structure, installation and maintenance of the equipment are also expensive. Further, the power for driving the rotating blades is large, and the running cost increases as the amount of treated water increases.

The present invention is intended to simplify the structure of the coagulation sedimentation device used as a tertiary treatment device of a wastewater treatment device, reduce the cost of the device, reduce the maintenance and operation costs, and reduce the coagulation sedimentation device. The task is to be able to be buried underground so that it can be used effectively on the ground.

[0011]

The wastewater treatment apparatus according to the first aspect of the present invention includes a rapid stirring tank 6 and a slow stirring tank 7 partitioned by a partition 5 in a container 1. The rapid stirring tank 6 includes an inlet 11 for treated water and a coagulant supply unit 12. The slow stirring tank 7 has an outlet 17 to the settling tank. An air diffuser 15 is arranged in the rapid stirring tank 6 along the lower side of the partition 5. The swirling flow is generated in the rapid stirring tank 6 by the diffused air rising along the partition wall 5 from the diffuser pipe, so that the inflow port 11 is opened in a direction to promote the swirling flow.

According to a second aspect of the present invention, in the aggregating apparatus according to the first aspect, the container 1 has a horizontal cylindrical shape, and the partition wall 5 is provided in a direction parallel to the cylinder axis of the container. A communication hole 8 for communicating the stirring tank 6 and the slow stirring tank 7 is provided, and a slow air diffuser 16 for generating a slow water flow in the slow stirring tank is provided at the bottom of the slow stirring tank 7. It is characterized by having.

[0013]

A diffuser / agitator for stirring treated water by diffused air flowing out of a diffuser tube into treated water is conventionally known.
Since a rapid stirring tank requires a strong stirring force, a diffuser stirring device is used instead of the conventional mechanical stirring device.
It is conceivable to obtain a stirring effect equivalent to that of a mechanical stirring device by increasing the amount of diffused air. However, according to a test conducted by the inventor of the present application, simply increasing the amount of diffused air,
It was impossible to obtain a stirring effect equivalent to that of a mechanical stirring device. From the results of experiments on the cause, it was found that a good local mixing effect can be obtained with a normal air diffusing structure, but the inter-zone mixing effect is insufficient. That is, when viewed as a whole tank, there are a plurality of areas where the medicine is almost uniformly mixed, and the uniformity is insufficient when comparing the plurality of areas with each other. Simply increasing it could not solve it.

Therefore, an experiment was conducted by attaching a diffuser tube capable of producing fine air bubbles along the bottom of the vertical side surface of the rapid stirring tank and rotating the water flow in the tank. A stirring effect could be obtained. Furthermore, it was effective to install the inlet and outlet of the treated water far apart and to open the inflow so that the flow direction of the inflow water coincides with the direction of the swirling water flow as much as possible. The present invention has been made based on such knowledge.

The horizontal cylindrical container 1 is suitable as a structure for burying a large-capacity container underground. When the partition 5 is provided in parallel with the cylinder axis of the horizontal cylindrical container 1, a large air diffusion distance (distance in the vertical direction) is formed along the partition 5, and a strong swirling flow can be effectively generated in the rapid stirring tank. In addition, the generated swirling flow flows along the semicircular container inner wall, and thus has a small resistance. Then, the inflow port 11 of the treated water is placed above the tank 5
If a communication hole 8 to the slow stirring tank is provided below the partition 5, the inlet and the outlet are far apart, and the inflow water is in a direction to promote the swirling flow. An ideal rapid stirring tank can be formed.

[0016]

1 to 3 show an embodiment of the present invention. The wastewater treatment apparatus of the present embodiment
It consists of two horizontal cylindrical containers 1. First until secondary processing
In the processing tank 2, the third and subsequent processes are performed in the second processing tank 3.

The coagulation tank 4 is located in the second processing tank 3 and is divided into a rapid stirring tank 6 and a slow stirring tank 7 by a partition wall 5 parallel to the cylinder axis. A communication hole 8 communicating the rapid stirring tank 6 and the slow stirring tank 7 is opened below the partition wall 5. Above the side wall 9 of the rapid stirring tank 6, there is an inflow port 11 of the treated water, near which the coagulant supply port 12, the pH regulator supply port 13 and the pH sensor 14 extend from the side wall 9 toward the partition 5 side. There is. The rapid stirring tank 6 is provided with a rapid diffusing tube 15 along the lower side of the partition 5, and the slow stirring tank 7 is provided with
The slow air diffusers 16 are provided so as to protrude at right angles to the partition wall 5. An outlet 17 having a baffle structure is provided above the side wall 10 of the slow stirring tank 7.

In the rapid stirring tank 6, the diffused air rises along the partition 5 because the rapid diffusion pipe 15 is provided along the lower side of the partition 5. By the action of the diffused air, the treated water in the rapid stirring tank 6 turns as an upflow near the partition wall 5 and a downflow near the side wall 9. Since the inner wall of the treatment tank is semicircular, the resistance of the treatment water is small, and the swirling of the treatment water occurs over the entire inside of the rapid stirring tank 6. Further, since the rapid diffusing pipe 15 is installed at the deepest position of the rapid stirring tank 6, a large diffusing distance can be secured, and a stronger swirling flow can be generated. Furthermore, since the inflow port 11 of the treated water is above the side wall 9, the downward flow generated on the side wall 9 side is strengthened by the transfer of the treated water, and the swirling speed of the treated water in the tank is also increased.
The swirling of the treated water enhances the mixing effect between the sections in the rapid stirring tank 6.

The secondary treated water is supplied from the inlet 11 to the rapid stirring tank 6.
By the swirling flow generated in the rapid stirring tank 6
The mixture is sufficiently mixed with the coagulant supplied from the coagulant supply port 12. In the rapid stirring tank 6, the pH adjusting agent supply port 13 and the pH
A sensor 14 is provided, and the pH value of the treated water is controlled to a range suitable for treatment and water discharge as needed. The coagulant supply port 12 and the pH control agent supply port 13 are installed near the inflow port 11 to supply the drug during the downward flow and quickly mix it with the treated water.

The treated water flowing into the slow stirring tank 7 from the communication hole 8 is gently stirred by the diffused air slowly discharged from the slow diffuser 16. At this time, the floc particles formed by aggregating with the aggregating agent repeatedly collide with each other,
Grows into relatively large particles.

Conventionally, fine bubbles of carbon dioxide gas generated by a chemical reaction between the flocculant and the treated water adhere to the surface of the floc particles, and the floc particles generated in the subsequent precipitation treatment are less likely to precipitate. This air bubble was removed by a suitable removing means such as the above. According to the stirring method of the present invention,
Due to the collision of the diffused air released from the slow diffuser 16,
The fine bubbles on the surface of the floc particles are removed, and do not hinder the subsequent precipitation treatment.

The grown floc and treated water are supplied to the outlet 17
Is discharged from The outlet 17 has a baffle structure, and the outlet is provided below the water surface, so that surface substances such as oil near the water surface are not discharged to the next settling tank.

In the rapid stirring tank, many fine flocs are formed in the treated water by mixing well with the flocculant. The role of the slow stirring tank 7 is to cause these fine flocks to collide with each other and grow the particle size to a large value. If the stirring in the slow stirring tank is too intense, the resulting floc may be crushed, so it is important to select an appropriate stirring intensity.

Similar to the calculation of the discharge coefficient M used for designing the mechanical stirring tank, the discharge coefficient M of diffused stirring is calculated by the following equation (1). - type 1 M = D / F M emission factor [-] volume of the water Dokasa by the rising of the whole bubble per D unit time [m ³ / s] flow rate of treated water per F unit time [m ³ / s ]

Equation 2 is used to determine the volume D of water displaced by the rise of the entire bubble per unit time.・ Equation 2 D = 3V · h / 2dB V Amount of diffused air per unit time [m ³ / s] dB Average diameter of bubble [m] h Water depth [m]

The optimum value of M in the slow stirring tank for growing flocks is 30 to 40. The value of M is also related to the average diameter of the bubbles. Generally, as the diameter of the bubbles increases, the rising speed of the bubbles increases, and the rising speed of the bubbles decreases by 75%.
If it exceeds cm / s, the floc is destroyed.

Equations 3 and 4 are used to determine the rate of rise vt of the bubble. Which one of the two expressions is used depends on condition 1
And condition 2 are selected. That is, Expression 3 is used when Condition 1 is satisfied, and Expression 4 is used when Condition 2 is satisfied.・ Condition 1 500 ≦ dB ・ v / ν ≦ 10 ⁵ Equation 3 vt = (3g ・ dB) ^1/2・ Condition 2 2 ≦ dB ・ v / ν ≦ 500 Equation 4 vt = ｛(4g ² ) / (225ν) ｝ ^1/3・ d
B vt Bubble rising speed [m / s] g Gravity acceleration [m / s ² ] ν Power viscosity of treated water [m ² / s]

If the average diameter of the bubbles is 1 cm or less, the rising speed of the bubbles does not exceed 75 cm / s, and the flocs are not broken. The material, structure and arrangement of the air diffuser are selected so as to satisfy the condition of the average diameter of the bubble and the condition of the above-mentioned M value.

Referring to FIG. 3, the first processing tank 2 and the second processing tank 3 in which the coagulation tank of the present invention is disposed will be described.

The entire first treatment layer 2 has a cylindrical shape and is sectioned in the axial direction of the cylinder, and the anaerobic filter tank 35 and the contact aeration tank 3
6 and 37 are provided with two primary sedimentation tanks 38. The wastewater flowing into the first treatment tank enters the anaerobic filter bed tank 35, is subjected to anaerobic treatment, and is aerobically treated in the contact aeration tanks 36, 37.
Organic matter is decomposed. Further, sludge that cannot be completely decomposed in the primary sedimentation tank 38 is settled and sent to the second treatment tank.

The entire second treatment tank 3 is cylindrical and is partitioned in the direction of the cylinder axis. The intermediate treatment tank 31, the coagulation tank 4, two secondary sedimentation tanks 32 and 33, and a disinfection tank 34 are provided. . The treated water after the secondary treatment flows into the second treatment tank 3 and is temporarily stored in the intermediate water storage tank 31. Next, the treated water moves to the flocculation tank 4 and flocs are formed. Next, the treated water moves to the secondary sedimentation tank 32 to remove the flocs. Further, the treated water passes through the second secondary sedimentation tank 33, removes the flocs again, is disinfected in the disinfection tank 34, and then discharged.

[0032]

According to the agglomeration apparatus of the aeration / diffusion system of the present invention, it is possible to obtain a stirring effect equal to or higher than that of the aggregating apparatus of the mechanical stirring system. In addition, it has the following advantages.

・ Because the peripheral device of the stirring means becomes unnecessary,
The entire device can be installed underground, and the land can be used effectively. -The cost of parts such as the air diffuser is low, the structure is simple, the manufacturing is not complicated, and the manufacturing cost is low. -Since fine bubbles adhering to the flocks are removed by the collision of the diffused air, no special degassing means is required. -Low maintenance and operation costs.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a coagulation tank.

FIG. 2 is a sectional view of a main part of FIG. 1;

FIG. 3 is a schematic diagram of a first processing tank and a second processing tank.

FIG. 4 is a side sectional view of a conventional coagulation tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 5 Partition wall 6 Rapid stirring tank 7 Slow stirring tank 8 Communication hole 11 Inlet 12 Coagulant supply port 15 Rapid diffuser 16 Slow diffuser 17 Outlet

Claims (2)

[Claims] A container (1) is provided with a rapid stirring tank (6) and a slow stirring tank (7) partitioned by a partition (5).
Is provided with an inlet (11) for treated water and a coagulant supply means (12),
The slow stirring tank (7) is a wastewater treatment system equipped with an outlet (17) to the sedimentation tank, and the rapid stirring tank (6) is provided with an air diffuser (15) along the lower side of the partition (5). It is a septum from this diffuser
Rapid agitation tank generated by aeration that rises along (5)
(6) The wastewater treatment device, wherein the inflow port (11) is open in a direction to promote the swirling flow in the inside. 2. A container (1) having a horizontal cylindrical shape, a partition (5) is provided in a direction parallel to a cylinder axis of the container, and a rapid stirring tank (6) and a slow stirring tank are provided below the partition. (7) Communication hole communicating with
(8) is provided, and a slow diffuser (16) is provided at the bottom of the slow stirring tank (7) for generating a gentle water flow in the slow stirring tank. 2. The wastewater treatment device according to 1.