JP2002192164A - Method and apparatus for coagulating sedimentation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for the addition of a coagulant for improving the quality of water and a pH adjuster to water-to-be-treated in a settling tank, especially suitable for improving the quality of treated water in the existing water-cleaning tank and for easily adding the function of flocculation. SOLUTION: The advection water treated in a bioreaction tank 5 is sucked from the inside of a center well 13 in a settling tank 7 by an induction pump 9 to be introduced into a rapid agitation tank 10. A coagulant and a pH adjuster are added to the advection water in the rapid agitation tank and they are agitated to be mixed, and then the water is returned to the inside of the center well 13 below the suction point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a septic tank provided with a sedimentation tank, wherein a flocculant is added to the treated water in order to improve the quality of the water discharged from the sedimentation tank, and SS removal of the treated water, and BOD and COD. The present invention relates to a method and an apparatus for improving the above-described method, and particularly to a method and an apparatus suitable for improving the treated water quality of an existing septic tank or simply adding a coagulation function to a newly installed septic tank.

[0002]

2. Description of the Related Art It is known to improve the quality of discharged water by adding a flocculant or a pH adjuster to treated water in a sedimentation tank. The sedimentation tank is usually arranged at the latter stage of the biological reaction tank, and sedimentation and separation of suspended particulate matter of the treated water purified by the microbial reaction is carried out, and the supernatant liquid is transferred to the subsequent disinfection tank. By adding an aggregating agent to the treated water in the sedimentation tank to cause an agglutination reaction, the suspended particulate matter (S
S) and some dissolved components can be removed by precipitation to improve the quality of treated water in the septic tank.

In order to carry out the agglutination reaction efficiently and promptly, it is desirable to add the aggregating agent while stirring the treated water. As a conventional method of adding a coagulant, a coagulation tank is provided between a pre-tank (usually a biological reaction tank) and a sedimentation tank, and the coagulant is added while stirring the treated water in the tank by a pump or aeration. Method, a method of installing a flocculation tank after the sedimentation tank after biological treatment and further guiding to the sedimentation tank provided in the subsequent stage, and a method of adding a coagulant in the middle of the advection pipe connected from the pre-tank to the sedimentation tank is used Have been.

[0004]

By the way, by improving the awareness of the environment and strengthening regulations, even in existing septic tanks in which no coagulant is added to treated water, the quality of discharged water can be improved by adding coagulant. There is a request to do so. In such a case, the septic tank is usually buried underground, so it is impossible to install a new coagulation tank.
In many cases, a method of adding a coagulant in the middle of the advection tube to the sedimentation tank is adopted.

However, usually, the flow rate of the treated water in the advection pipe does not often have the flow rate required to stir and mix the added flocculant, so that the added flocculant often flows in the advection pipe. The trouble of sedimentation and stagnation occurs.

Accordingly, the present invention provides a coagulation / sedimentation method and apparatus which can efficiently add and mix a coagulant, a pH adjuster, and the like to treated water in a sedimentation tank, and can be easily adopted in existing purification tanks. The challenge is to obtain

[0007]

In order to prevent the water in the sedimentation tank from flowing due to the inflow of the advancing water and causing an obstacle to the sedimentation of the sludge, a vertical cylinder called a center well is provided in the sedimentation tank. Migrated water from the pre-tank of the contact aeration tank flows into the center well. In the present invention, the advection water treated in the biological reaction tank 5 is sucked from the inside of the center well 13 of the settling tank 7 by the introduction pump 9 and guided to the rapid stirring tank (reaction tank, also called mixing tank) 10.
The coagulant is added to the treated water by adding the coagulant and the pH adjuster in the rapid stirring tank, and then returning the coagulant and the pH adjuster to the center well 13 at a position below the sucked position.

In this case, if necessary, an aggregating tank may be provided at the subsequent stage of the rapid reaction tank to perform a certain amount of agglutination reaction, and then returned to the sedimentation tank. It is desirable that the position where the treated water to which the flocculant is added is returned into the center well 13 is below the inlet 18 of the advancing water to the center well 13.

The above method can be carried out by installing a rapid stirring tank on the ground for an existing septic tank buried underground. In this case, a rapid stirring tank is installed on the existing septic tank underground. It is only necessary to additionally install two pipes that connect to the water, so that the quality of the discharged water from the existing septic tank can be easily improved.

In the rapid stirring tank 10, a sulfuric acid band, PAC
(Polyaluminum chloride), a coagulant such as ferric chloride, polyiron, aluminum sulfate, etc., and an acid (sulfuric acid, hydrochloric acid, etc.) or an alkaline aqueous solution (sodium hydroxide, etc.) for adjusting the pH to secure coagulation conditions Can be supplied.

The coagulant, acid and alkali aqueous solution are supplied to the pre-tank 5
An appropriate amount can be added by controlling the supply pumps 19, 20, and 21 of these chemicals in accordance with the amount of water advancing from the tank to the sedimentation tank 7 and the pH of the rapid stirring tank 10. The operation state of the pump 9 for sending water (referred to as an introduction pump in this specification) 9 and ON by the pH meter 28
It can be realized by performing -OFF operation, proportionally controlling a variable speed pump, and the like. Further, the stirring of the rapid stirring tank 10 can be performed by mechanical stirring or stirring by a stream of advancing water pumped up from the precipitation tank by the introduction pump 9.

That is, the present invention comprises a biological reaction tank 5 and a sedimentation tank 7 for sedimenting and separating suspended particulate matter in the treated water. The sedimentation tank 7 is provided with a center well 13 and has a In the wastewater treatment apparatus in which the treated water flows into the center well, the advection water flowing into the sedimentation tank 7 is sucked from the center well 13 by the introduction pump 9 and guided to the rapid stirring tank 10, where it is aggregated in the rapid stirring tank. And a coagulation aid (polymer coagulant) in a coagulation tank 11 provided in connection with a rapid stirring tank as required, and suction of the introduction pump in the center well 13 By returning to a position below the position, the suspended particulate matter in the treated water in the sedimentation tank 7 and the substance that has formed flocs due to the flocculation effect can be efficiently settled and separated.
It is characterized by improving the quality of treated water discharged from the settling tank.

[0013]

FIG. 1 shows a first embodiment in which the present invention is applied to a wastewater treatment apparatus having a flow rate adjusting tank, and FIG. 2 shows a case in which the present invention is applied to a wastewater treatment apparatus having a sedimentation separation tank. It is the figure which each showed 2nd Example typically. 1 and 2, 1 is an inflow pump tank, 2 is a flow control tank, 3 is a sedimentation separation tank, and 4 is a flow control tank 2 from FIG.
Alternatively, an inflow pump for sending wastewater to the sedimentation separation tank 3 in FIG. 2, 5 is a biological reaction tank such as a contact aeration tank, and 6 is a flow control tank 2 in FIG.
Is a transfer pump for sending treated water from the reactor to the biological reaction tank 5, 7 is a sedimentation tank, and 8 is an advection pipe for guiding treated water from the biological reaction tank to the sedimentation tank.

The inflow pump tank 1, the flow rate adjusting tank 2, the biological reaction tank 5 and the sedimentation tank 7 shown in FIG. 1 are formed by partitioning the inside of one or a plurality of housings with partition walls. It is buried and installed. The same applies to the inflow pump tank 1, the precipitation separation tank 3, the biological reaction tank 5, and the precipitation tank 7 shown in FIG. These casings are provided with an inflow pipe for wastewater, a discharge pipe for treated water, a disinfection tank for discharged water, and the like, but these are omitted in the drawings.

On the other hand, on the ground, an introduction pump 9, a rapid stirring tank 10, a flocculation tank 11, and a supply device for a flocculant, an acid, an alkali, and a flocculant are installed. is set up.

At the center of the underground sedimentation tank 7, a center well 13 composed of a vertical cylinder is disposed, and an advection pipe 8 for guiding treated water from the biological reaction tank 5 to the sedimentation tank 7 is provided in the center well. 13 is open inside. An introduction pipe 14 and a return pipe 15 are opened inside the center well 13. The opening position 16 of the introduction pipe is the opening position 17 of the return pipe.
The opening position 17 of the return pipe is higher than the opening position 18 of the advection pipe from the biological reaction tank. Introductory pipe 1
An introduction pump 9 is provided in the middle of 4, and the discharge pipe of the introduction pump communicates with the rapid stirring tank 10. A flocculation tank 11 is provided in connection with the rapid stirring tank 10, and the treated water flows from the rapid stirring tank 10 to the flocculation tank 11, flows from the flocculation tank 11 to the return pipe 15, and is returned to the precipitation tank.

In the rapid stirring tank 10, the coagulant supply pipe 25, the acid supply pipe 26, and the alkali supply pipe 25 communicate with the coagulant tank 22, the acid tank 23, and the alkali tank 24 via the respective supply pumps 19, 20, and 21. Pipe 27
Is communicated. The rapid stirring tank 10 is provided with a pH meter 28 for measuring the pH of the treated water in the tank. On the other hand, the coagulation tank 11 is provided with an auxiliary supply pipe 31 that communicates with an auxiliary tank 30 that stores a polymer coagulant serving as an aggregation auxiliary via a supply pump 29.

The controller 12 includes an inflow pump controller 4
a, a transfer pump control unit 6a, an aeration air supply control unit (not shown) for the biological reaction tank, etc., and an introduction pump control unit 9
a and an agglutination reaction control unit 10a. The agglutination reaction control unit 10a of FIG. 1 receives the signal of the transfer pump control unit 6a, controls the operation of the introduction pump 9 by the introduction pump control unit 9a, and receives the operation of the introduction pump 9 and the signal of the pH meter 28. , And the supply pumps 19, 20, 21, and 29 for the respective chemicals are controlled. The agglutination reaction control device 10a in FIG.
In response to a signal from the inflow pump control section 4a, the introduction pump control section 9a controls the introduction pump 9 so that the operation of the introduction pump 9 and p
In response to the signal from the H meter 28, the supply pump 19 for each chemical solution,
20, 21, and 29 are controlled.

Hereinafter, depending on the presence or absence of the flow control tank 2 and the sedimentation separation tank 3, the introduction pump 9, the chemical supply pumps 19 and 20,
An example of how to control the operation of 21, 29 and the rapid stirring tank 10 will be described. a: Operation of the introduction pump 9 a1: When the flow rate adjusting tank 2 is provided: linked with the operation of the transfer pump 6. The start and stop times are delayed depending on the characteristics of the facility. a2: When there is a sedimentation separation tank 3 and an inflow pump tank 1: linked with the operation of the inflow pump 4. The start and stop times are delayed depending on the characteristics of the facility. a3: When there is a sedimentation separation tank 3 but no inflow pump tank 1:
Operate constantly or operate by detecting fluctuations in the water level in the sedimentation tank. The detection of the water level fluctuation can be performed in the biological reaction tank 5 or the sedimentation separation tank 3. Since the amount of water to be transferred to the sedimentation tank fluctuates, precise operation is not possible. a4: It is possible to operate in conjunction with the inflow water measurement system. The start and stop times are delayed depending on the characteristics of the facility.

B: Operation of the chemical pump The supply of the coagulant and the polymer coagulant is linked with the operation of the introduction pump 9. The supply of acid and alkali is linked to the introduction pump and controlled by a pH controller. Usually, since the coagulant is acidic, the pH adjustment is often required only with the alkali, and when the amount of the coagulant added is small or the alkalinity of the advection water is high, the addition of alkali may not be necessary.
When the pH can be kept within the range of 5.8 to 8.6 by adding a certain amount of alkali to the amount of the coagulant added, or when the above pH is maintained without adding alkali. In such a case, it is not necessary to adjust the pH.

C: Rapid stirring tank Usually, the capacity of the rapid stirring tank is about 10 minutes for the residence time and about 20 to 30 minutes for the flocculation tank. A stirrer is installed to promote the mixing of the chemicals, the rapid stirring tank is rapidly stirred, and the flocculation tank is slowly stirred. A stirrer is not required if the agitated water is sufficiently stirred by the water flow supplied to the tank.

[0022]

(1) The quality of treated water can be improved. Water quality can be improved by improving or removing BOD (biochemical oxygen demand), COD (chemical oxygen demand), SS (suspended particulate matter), phosphorus and its compounds, nitrogen and its compounds, etc. of treated water. In addition, the transparency of the treated water can be improved and the chromaticity can be reduced. Further, metals and organic compounds that form flocs and become insoluble by flocculation and sedimentation can be removed. For example, the amount of coagulant required for removing phosphorus in a rapid stirring tank (P: A
1 or P: Fe molar ratio of about 1 to 5), it is possible to remove phosphorus in the treated water.

(2) It can be easily added to existing equipment. By adding two pipes in the sedimentation tank, the pipes can be easily and inexpensively added, and the quality of treated water in an existing septic tank or the like can be improved. Further, since the equipment cost is low, the quality of the treated water can be improved with a small cost even with a newly installed device.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a first embodiment.

FIG. 2 is a block diagram schematically showing a second embodiment.

[Explanation of symbols]

 5 Biological reaction tank 7 Sedimentation tank 9 Introducing pump 10 Rapid stirring tank 11 Coagulation tank 13 Center well 15 Return pipe 16 Opening position 17 Opening position 19-21 pump 29 Coagulation auxiliary agent supply pump

Claims (4)

[Claims] 1. The treated water treated in the biological reaction tank (5) is transferred to the center well (13) of the sedimentation tank (7), and suspended particulate matter in the treated water is settled and separated in the sedimentation tank (7). A coagulating sedimentation method of a wastewater treatment apparatus, wherein advancing water flowing into a sedimentation tank (7) is guided from a center well (13) into a rapid stirring tank (10) by an introduction pump (9), and the rapid stirring tank (10 A) a coagulant is added to the treated water in step (iii), and the water is returned to a position below the suction position of the introduction pump in the center well (13). 2. A wastewater treatment system comprising a biological reaction tank (5) and a sedimentation tank (7) for sedimenting and separating suspended particulate matter in the treated water, wherein a coagulant supply means (19, 20, 21) is provided. ), And an introduction pump (9) for introducing treated water to the rapid stirring tank (10) from a suction port (16) opened in the center well (13) of the precipitation tank (7). A return pipe (15) for returning the treated water of the rapid stirring tank (10) into the center well (13), and the return port (17) of the return pipe is located below the center well at the position of the center well. (13) A coagulation sedimentation device for a wastewater treatment device, wherein the coagulation sedimentation device is open inside. 3. The coagulation sedimentation apparatus according to claim 2, further comprising a coagulation tank (11) provided with a coagulation aid supply means (29) at a stage subsequent to the rapid stirring tank (10). 4. A return port for treated water to which a coagulant has been added (17).
Is located below the inlet (18) of the advancing water from the pre-tank (5) to the center well (13) of the settling tank (7).
Or the coagulation sedimentation apparatus according to 3.