JPH0651195B2 - Control method for batch type waste water treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a wastewater treatment apparatus using batch type activated sludge,
The present invention relates to a control method that maintains a stable and high processing function.

[Conventional technology]

In recent years, as compared with the continuous activated sludge method, a batch activated sludge method that is easy to maintain and suitable for small-scale wastewater treatment, for example, JP-A-55-152594 is well known.

This method is a treatment method in which each process of inflow, aeration, precipitation, and discharge is repeated in a single treatment tank as one cycle, but in order to maintain stable high treatment performance It is necessary to control withdrawal.

[Problems to be Solved by the Invention] In the conventional batch-type wastewater treatment equipment, the time is set to 1
The sludge is drawn out once every cycle or every cycle, but especially when the load fluctuation is large, the MLSS concentration in the tank fluctuates greatly and the treatment performance and sludge settling property deteriorate, and the supernatant liquid is discharged. Problems such as the inclusion of sludge in the soil tend to occur.

It is also considered to detect the sludge concentration and control the amount of extracted wastewater, but it is actually quite difficult to keep the sludge amount constant, and it is not practical because a complicated control device is required.

[Means for solving problems]

Installed a device for detecting the sludge interface near the low water level after discharge,
Compare the settling time of the interface with the preset time, and if the settling time is longer than the preset time, the sludge is drawn out, and the sludge concentration and sludge interface are adjusted to an appropriate state by a simple control method. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a batch type waste water treatment equipment of the present invention.
Reference numeral 1 is a raw water tank for storing waste water, which is made to flow into a treatment tank 2 by a raw water pump 3. An aeration device 5 is provided on the float 4 on the drainage surface of the treatment tank 2, and air is blown into the drainage by the aeration device 5 to perform necessary agitation with a stirring blade.

The float 4 is provided with a supernatant water withdrawing pipe 7 for withdrawing the supernatant water and with an arm 6 so as to follow the water level and swing. It is also possible to perform these aerations with a general blower and an air diffuser.

Next, the sensor 9 of the sludge interface meter 10 is provided near the low water level after the discharge of the treatment tank 2, that is, at the LWL position. Control device 11
Has a built-in timer, the sludge extraction pump 8 provided at the bottom of the treatment tank 2 is turned on and off while the sludge interfacial property and other signals from the measuring instrument are input, and the treated water is discharged from the inflow of raw water. Control all the operation schedule up to.

FIG. 2 shows an example of the operation schedule in the present invention. After inflowing raw water, continuous aeration or intermittent aeration is performed to perform biological treatment, and then sludge is allowed to settle.
At this time, a timer incorporated in the control device is activated to measure the time t required for the sludge interface to drop to the sensor unit after the start of precipitation.

Here, (1) When the interface does not lower to the sensor unit within a predetermined settling time t0 (t ≧ t0), an emergency sludge withdrawal command is output from the controller, and the sludge withdrawal pump is set to the set time T1.
It is driven only and sludge is pulled out.

(2) When the sludge interface lowering time t is longer than the set time t1 (t ≧ t1), the set time T1 is set based on the relationship between the MLSS concentration and the sludge interface settling time, which will be described later. The sludge extraction pump is operated for a predetermined time T2 and the sludge is extracted. However, the extraction time is T2 ≦ T1.

(3) When the sludge interface lowering time t is shorter than a predetermined settling time t0 and a set time t1 (t <t0, t <t1), sludge extraction is not performed.

In the case of sludge withdrawal, it is preferable that the emergency withdrawal shown in (1) is performed prior to the supernatant water discharge step, but normal drainage is completed even during the discharge step. It may be later.

In the discharge step, the supernatant water is discharged from the supernatant water intake fixed to the float through the supernatant water drawing pipe, but according to the method of the present invention, the sludge interface is already below the low water level (LWL) at the start of the discharge. Since it has reached, there is no need to worry about entraining sludge with clear water.

Fig. 3 shows the relationship between the sludge suspended matter (MLSS) concentration and the time required for the sludge interface to settle for 1 m.
By using this figure, the sedimentation velocity at the sludge interface can be measured and the MLSS concentration can be indirectly controlled. That is, the MLSS concentration in the processing tank is set to a certain concentration C0.
In order to keep it below, the sedimentation time t10 at the sludge interface corresponding to C0 is obtained from FIG. 3 and multiplied by the depth hm from the high water level (HWL) to the sensor part of the sludge interface meter t10 × h
The control may be performed with the above-mentioned set time t1.

The relationship between the MLSS concentration and the sedimentation time at the sludge interface shown in Fig. 3 changes somewhat depending on the type of wastewater and the treatment conditions. Therefore, it is necessary to obtain it by experiments or other methods before adopting this method. is there.

〔The invention's effect〕

The present invention, in the batch type waste water treatment device, provided a sensor of the sludge interface detection device in the vicinity of the low water level after the discharge, to measure the time until the sludge interface is lowered to the sensor unit after the start of precipitation,
If this time is longer than the preset time, the sludge interface and sludge concentration in the treatment tank can be managed in an appropriate state by controlling the sludge to be drawn out, so that the stable and high treatment function can be maintained. Have.

[Brief description of drawings]

FIG. 1 is an apparatus diagram of the present invention, FIG. 2 is an operation schedule of the present invention, and FIG. 3 is a graph showing the relationship between the sludge suspended matter (MLSS) concentration and the time required for the sludge interface to settle for 1 m. Is. 1 is a raw water tank, 2 is a treatment tank, 3 is a raw water pump, 4 is a float, 5 is an aerator, 6 is an arm, 7 is a supernatant water drawing pipe,
8 is a sludge drawing pump, 9 is a sensor, 10 is an interface meter,
11 is a control device.

Claims (3)

[Claims] 1. After inflowing wastewater into a treatment tank and performing aeration treatment,
In a batch-type wastewater treatment device that settles sludge and discharges supernatant water, a sensor for a sludge interface detection device is provided near the low water level after discharge of the supernatant water, and after this sensor starts precipitation, the sludge reaches a predetermined water level. A method for controlling a batch-type waste water treatment device, characterized in that the time until the interface is formed is measured, and when this time is longer than a preset time, sludge is drawn out. 2. The method for controlling a batch type waste water treatment device according to claim 1, wherein the preset time is settling time of sludge. 3. The batch processing apparatus control method according to claim 1, wherein the preset time is set based on the relationship between the MLSS concentration and the sedimentation time at the sludge interface.