JPH10235386A - Temperature control device for aeration tank - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To stabilize the temperature in the tank of an aeration tank to reduce fluctuations in the concentration of dissolved oxygen in the tank, thereby stabilizing the operation of wastewater treatment equipment and the quality of treated water. Provided are a control device capable of performing the control and a method for controlling wastewater treatment equipment using the control device. SOLUTION: An activated sludge drainage is provided in the order of a raw water tank, a neutralization tank having a heating device, and an aeration tank, and the neutralization tank and the aeration tank are connected by a raw water supply pipe having a heat exchanger for cooling. A temperature control device comprising the following instrumentation equipment in the aeration tank of a processing facility. a) Raw water temperature detector and raw water temperature controller for measuring the temperature of raw water supplied from the neutralization tank to the aeration tank b) Temperature detector in the aeration tank and temperature controller in the aeration tank c) Heating of the neutralization tank Heating medium supply control valve for equipment d) Cooling medium supply control valve of heat exchanger for cooling raw water

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control apparatus for an activated sludge aeration tank used in general wastewater treatment plants and sewage treatment plants such as chemical factories, and a method for controlling the temperature of an aeration tank using the same. Things.

[0002]

2. Description of the Related Art In a wastewater treatment process by the activated sludge method, wastewater is received in a raw water tank, pH and nutrition are adjusted in a neutralization tank as pretreatment, and air or oxygen is supplied into an aeration tank. In general, aerobic microorganisms oxidize and decompose organic matter, aggregate sludge as required, and then separate and settle in a sedimentation tank to obtain treated water.

In order to stabilize the operation and wastewater quality in such treatment, it is usual to control the concentration of dissolved oxygen in the aeration tank to be constant, and therefore the dissolved oxygen in the aeration tank is controlled. A method of supplying oxygen or air into the tank depending on the concentration is often used. However, with this control method alone, the dissolved oxygen concentration in the aeration tank fluctuates due to fluctuations in the temperature of the wastewater to be received, seasonal changes in temperature, and daily changes. It was difficult to stabilize.

[0004]

Therefore, an operating method for controlling the temperature of the aeration tank within a specific range has been proposed. In this method, too, hot water or the like is contained in the tank to control the temperature of the aeration tank. When cold water is supplied or heat exchange equipment is installed in an aeration tank, there is a problem in that the temperature distribution generated at that time affects the activity of microorganisms, and controllability deteriorates.

That is, the problem to be solved by the present invention is:
A control device capable of stabilizing the temperature in the tank of the aeration tank and reducing the fluctuation of the dissolved oxygen concentration in the tank, thereby stabilizing the operation of the wastewater treatment equipment and the quality of the treated water, and using the same. An object of the present invention is to provide a method for controlling a wastewater treatment facility.

[0006]

Means for Solving the Problems As a result of repeated studies on the above points, the present inventors have found that good results can be obtained by adjusting the temperature at a specific location. completed. That is, the gist of the present invention is that a raw water tank (1), a neutralization tank (2) having a heating device, and an aeration tank (3) are provided in this order, and the neutralization tank (2) and the aeration tank (3) are provided. Raw water supply pipe (1) having a heat exchanger (16) for cooling
The temperature control device for the aeration tank of the activated sludge wastewater treatment equipment connected in 2) is a control device including the following instrumentation equipment.

A) Raw water temperature detector (4) for measuring the temperature of raw water supplied from neutralization tank (2) to aeration tank (3) b) Temperature detector (6) in the aeration tank and inside the aeration tank Temperature controller (7) c) Raw water temperature controller for adjusting the temperature of raw water supplied to the aeration tank based on the output of the raw water temperature detector (4) and the output of the temperature controller in the aeration tank (7). (5) d) A heating medium supply control valve (8) for the heating device of the neutralization tank, which is a heating operation end of the raw water temperature controller (5) e) A cooling operation end of the raw water temperature controller (5) The cooling medium supply control valve (9) of the heat exchanger (16) for cooling the raw water to be formed The gist of the present invention is that the temperature controller (7) in the aeration tank is on the master side and the raw water temperature controller (5) is the slave. The above-described control device in which a cascade control loop on the side is formed,
And the above control device using a split range adjuster as the raw water temperature adjuster (5). Furthermore, the gist of the present invention resides in a method for controlling the temperature of an aeration tank of an activated sludge wastewater treatment facility using the above-described control device.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The activated sludge wastewater treatment equipment to be used in the present invention is provided with a raw water tank (1), a neutralization tank (2) having a heating device, and an aeration tank (3) in this order. The tank is a facility connected to a raw water supply pipe (12) having a heat exchanger (16) for cooling.

The raw water tank (1) is a tank for receiving wastewater from one or a plurality of drainage systems, and a neutralization tank (2).
Before the wastewater is treated with activated sludge,
This is a tank for performing adjustment and / or nutrition adjustment. Depending on the scale of the treatment equipment, the raw water tank and the neutralization tank can be combined into one tank. This neutralization tank is provided with a heating device. As the heating device, any of an indirect heating device such as a jacket and a coil and a direct heating device such as a steam blowing tube may be used.
This is preferable in terms of simplicity of inspection.

[0010] An aeration tank for performing wastewater treatment with activated sludge and a neutralization tank are connected by a raw water supply pipe having a heat exchanger for cooling. The type of the heat exchanger is not particularly limited, and may be, for example, a double tube type or a multi tube type. The location of the heat exchanger is not particularly limited as long as it is in the middle of the connection pipe between the neutralization tank and the aeration tank.
In order to avoid the influence of the outside air temperature on the raw water after the temperature control and to perform the efficient operation, it is preferable to provide the raw water at a position close to the aeration tank.

As described above, in controlling the temperature in the tank of the aeration tank, the method of adjusting the temperature of the raw water supplied to the aeration tank without installing a heating / cooling device in the aeration tank is adopted. This has the effect of reducing the occurrence of temperature distribution in the tank and, therefore, eliminating the risk of inactivating or reducing the activity of microorganisms. In order to effectively control the above wastewater treatment equipment, a control device equipped with the following instrumentation is used.

A) Raw water temperature detector (4) for measuring the temperature of raw water supplied from neutralization tank (2) to aeration tank (3) b) Temperature detector (6) in aeration tank and inside aeration tank Temperature controller (7) c) Raw water temperature controller for adjusting the temperature of raw water supplied to the aeration tank based on the output of the raw water temperature detector (4) and the output of the temperature controller in the aeration tank (7). (5) d) A heating medium supply control valve (8) for the heating device of the neutralization tank, which is a heating operation end of the raw water temperature controller (5) e) A cooling operation end of the raw water temperature controller (5) Cooling medium supply control valve (9) of heat exchanger (16) for cooling raw water to be used As these temperature detector, temperature controller and control valve, those generally used for instrumentation can be used.

[0013] In addition, steam is preferable as the heating medium, and cooling water (re-cooled water, cold water, or the like) is preferable as the cooling medium from the viewpoint of easy availability. By connecting such instrumentation devices so as to form a cascade control loop in which the temperature controller (7) in the aeration tank is on the master side and the raw water temperature controller (5) is on the slave side, fluctuations are small. , Stable control becomes possible.

Further, if a split range controller is used as the raw water temperature controller (5), the operating end can be switched between heating and cooling with one controller, so that the apparatus can be made compact and the equipment cost can be reduced. Becomes possible. Further, the temperature control method of the aeration tank according to the present invention is to control the temperature in the tank of the aeration tank of the activated sludge wastewater treatment equipment by using the above-described control device.

[0015]

The embodiments of the present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention. FIG.
The temperature control device in the aeration tank comprises a cascade control loop in which the temperature controller in the aeration tank (7) is a master-side controller and the split-range-type raw water temperature controller (5) is a slave-side controller.

Here, steam (hereinafter sometimes abbreviated as "steam") is used as a heating medium, and cooling water is used as a cooling medium. When the steam supply control valve (8) needs to be heated in winter, the cooling water supply control valve (9)
They can be used in summer when cooling is required. For example, in winter, the temperature controller (7) in the aeration tank, which is the master-side regulator, calculates the amount of steam required to approach the target temperature from the deviation between the target temperature in the aeration tank and the actual temperature. , A signal is sent as a set value to the raw water temperature split range controller (5). The raw water temperature split range controller (5), which is a slave controller, adjusts the steam supply control valve (8) so as to follow the set value. In the summer, similarly, the cooling water supply control valve (9) is used to cool the raw water.

That is, the fluctuation of the raw water temperature is absorbed by the slave-side controller, and the temperature in the aeration tank, which is the main purpose, can be kept constant. FIG. 2 is a graph in which the time variation of the inside temperature of the aeration tank before and after the start of the inside temperature control of the aeration tank using the control device of FIG. 1 is measured. The temperature in the aeration tank indicated by TT1 was ± 0.5 ° C. with respect to the target temperature of 36 ° C. after the control was started, despite the fluctuation range of 6 to 7 ° C. before the control was started. You can see that it is within the range.

FIG. 3 shows the time variation of the dissolved oxygen concentration (DO) in the aeration tank when the operation shown in FIG. 2 is performed. Before the temperature control of the aeration tank was started, the fluctuation range was about 1 ppm, but after the control was started, it was about 0.5 ppm, and it is observed that the temperature tends to further decrease.

[0019]

By using the control device of the present invention,
Since the temperature can be controlled without affecting the activity of the microorganisms in the aeration tank, fluctuations in the dissolved oxygen concentration in the tank can be reduced. This makes it possible to stabilize the operation of the wastewater treatment facility and the quality of the treated water.

When the concentration of dissolved oxygen and the temperature in the aeration tank are kept constant, the habitat of the aerobic microorganisms in the aeration tank is stabilized, and the organic matter (COD, B
An improvement in the decomposition rate of the OD component can also be expected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a temperature control device for an aeration tank of the present invention and a wastewater treatment facility using the same.

FIG. 2 is a graph showing temporal fluctuations in the temperature inside the aeration tank before and after starting the temperature control of the aeration tank using the temperature control device of FIG. 1;

FIG. 3 is a graph showing the temporal variation of the dissolved oxygen concentration in the aeration tank before and after starting the temperature control of the aeration tank using the temperature control device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Raw water tank 2 ... Neutralization tank 3 ... Aeration tank 4 ... Raw water temperature detector 5 ... Raw water temperature split range controller (TC2) 6 ... Temperature detector in aeration tank 7 ... Temperature controller in aeration tank (TC1) 8 ... Heating medium (steam) supply control valve 9 ... Cooling medium (cooling water) supply control valve 10 ... Steam supply pipe 11 ... Cooling Water supply pipe 12 Raw water supply pipe 13 Oxygen supply pipe 14 Exhaust gas discharge pipe 15 Drainage receiving pipe 16 Cooling heat exchanger TT1 Temperature inside aeration tank TT2 ..Raw water temperature DO: dissolved oxygen concentration meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiaki Yamamoto 3-10, Utsudori, Kurashiki-shi, Okayama Pref.

Claims (4)

[Claims] 1. A raw water tank (1), a neutralization tank (2) having a heating device, and an aeration tank (3) are provided in this order, and the neutralization tank (2) and the aeration tank (3) are provided for cooling. A temperature control device for an aeration tank of an activated sludge wastewater treatment facility connected by a raw water supply pipe (12) having a heat exchanger (16), the control device including the following instrumentation equipment. a) Raw water temperature detector (4) for measuring the temperature of raw water supplied from neutralization tank (2) to aeration tank (3) b) Temperature detector in aeration tank (6) and temperature controller in aeration tank (7) c) Raw water temperature controller (5) for adjusting the temperature of raw water supplied to the aeration tank based on the output of the raw water temperature detector (4) and the output of the temperature controller in the aeration tank (7). d) A heating medium supply control valve (8) for the heating device of the neutralization tank, which forms a heating operation end of the raw water temperature controller (5). e) Raw water cooling, which forms a cooling operation end of the raw water temperature controller (5). Medium supply control valve (9) for heat exchanger (16) 2. A temperature control device for an aeration tank according to claim 1, wherein a cascade control loop is formed in which the temperature controller in the aeration tank is on the master side and the raw water temperature controller is on the slave side. . 3. A temperature control device for an aeration tank according to claim 1, wherein a split range adjuster is used as the raw water temperature adjuster (5). 4. A method for controlling the temperature of an aeration tank of an activated sludge wastewater treatment facility using the control device according to claim 1.