JPS6314679B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optimal treatment method for wastewater treatment equipment.
This invention relates to a control method for maintaining the Do value. In general, in small and medium-sized wastewater treatment plants, wastewater treatment equipment called oxidation date systems is often used, as it is energy-saving and easier to operate and manage than the aeration method, activated sludge method, etc. However, this wastewater treatment equipment uses a horizontal rotor-rotating aeration system installed in the Deitzch tank that forms the circulation path to aerate and flow the wastewater, so it does not have the advantage of high nitrification and denitrification rates. However, since the operation is performed under the same operating conditions as originally set, it is not possible to respond appropriately to changes in the inflow load conditions due to changes in the amount and quality of sewage inflow, especially BOD. It has been extremely difficult to optimally control the Do value of water to a predetermined value. Therefore, under low load conditions, overaeration occurs, and only the nitrification reaction progresses, denitrification does not occur, which not only causes problems such as a decrease in PH value, but also consumes unnecessary power. Under load conditions, there were many drawbacks such as insufficient Do, nitrification reactions and denitrification were not promoted, and the quality of treated water deteriorated.

The present invention has been made to improve the above conventional drawbacks, and the water level in the circulation path is adjusted according to the difference between the detected value of Do detected at a predetermined position in the circulation path of a wastewater treatment device and the set value. The amount of oxygen supplied is adjusted according to the depth of immersion of the rotor.
The feature is that the Do value is controlled to a predetermined value, and it is possible to optimally control the Do value of treated water to a predetermined value even if the inflow load conditions of flowing water change. The purpose of the present invention is to provide a method for controlling the amount of oxygen supplied in a wastewater treatment device.

Embodiments of the present invention will be described below with reference to the drawings.

1 to 3, reference numeral 1 denotes a date tank having a circulation path 2, which is generally a track type circulation path 2.
is formed. 3 is the circulation path 2 of the deitsch tank 1
It is a horizontal rotor-rotating aeration device placed across the top, and both ends of its rotating shaft 4 are connected to a date tank 1, respectively.
A plurality of blade plates 7 are arranged radially in parallel with the axis of the rotating shaft 4 between circular end plates 6, 6 fixed parallel to both ends of the rotating shaft 4. The rotor 8 is configured as follows. By driving the motor 9, the rotor 8 is rotated clockwise as shown by the arrow in FIG. 2, thereby aerating and flowing the treated water. Reference numeral 10 denotes a wastewater inflow pipe, the outflow side of which is connected to a distributor pipe 11. The distributor pipe 11 connects the circulation path 2 to the upstream side at a predetermined distance from the aeration device 3 with respect to the mixed liquid 12 flowing in the direction of the arrow shown in FIG. Discharge holes 13 are provided at predetermined intervals on the downstream side of the discharge holes 13. It is designed to be more uniformly dispersed and released within the circulation path 2. In addition, 15 is an on-off valve provided in the middle of the wastewater inflow pipe 10, and this on-off valve 15 can be opened and closed to adjust the inflow amount of the raw waste water 14.

Further, on the upstream side of the distributor pipe 11, a flow channel 16 is provided passing through the side wall of the deutsch tank 1, and an opening 17 provided in the side wall of the deutsch tank 1, which serves as an inlet of the flow channel 16, is provided. A movable weir 18 is provided which is movable in the vertical direction by a drive device 21 with both ends guided by grooves provided in the opening of the deutsch tank 1. When the movable weir 18 is lowered, the mixed liquid 12 in the circulation path 2 is moved. The water exceeds the upper edge of the movable weir 18 and overflows into the flow channel 16, and the water level in the circulation channel 2 decreases. Reference numeral 19 denotes an outflow pipe that opens at the bottom of the flow channel 16, through which the mixed liquid 1 overflowing into the flow channel 16 is discharged.
2 is led to a sedimentation basin (not shown) or the like via an outflow pipe 19. In addition, the mixed liquid 1 led to a sedimentation tank etc.
2 is separated and concentrated in a sedimentation tank or the like, and is appropriately returned to the Deitch tank 1 as return sludge via a return means, where it is aerated. Furthermore, in order to raise the water level in the circulation path 2, the movable weir 18 may be pulled up to increase the effective water depth of the circulation path 2.

In this way, in the wastewater treatment device having the above configuration, the water level in the circulation path 2 can be changed arbitrarily by moving the movable weir 18, so the horizontal position of the rotor 8 of the aeration device 3 can be changed up or down. As shown in Figure 2, the water level is L-
By changing it from L to L'-L', the immersion depth l of the rotor 8 can be changed arbitrarily.

Figure 4 is a performance curve diagram that experimentally determined the relationship between the immersion depth l of the rotor 8 and the oxygen supply amount.As is clear from this figure, the relationship between the immersion depth l of the rotor 8 and the oxygen supply amount is There is a close relationship, and as the submersion depth l of the rotor 8 increases, the amount of oxygen supplied tends to increase in proportion to this. Therefore,
If the relationship between the immersion depth l of the rotor 8 corresponding to the diameter and rotational speed of the rotor 8 of the aeration device 3 to be installed and the oxygen supply amount is determined in advance through experiments, the immersion depth l of the rotor 8 can be changed. This makes it possible to obtain an arbitrary amount of oxygen supply.

The Do value of the mixed liquid 12 tends to increase as the amount of oxygen supplied by aeration increases, and conversely, when the amount of oxygen supplied decreases, the Do value tends to decrease. Therefore,
By changing the immersion depth l of the rotor 8,
It becomes possible to control the Do value of the mixed liquid 12.
Therefore, in the present invention, a Do value suitable for biological treatment of wastewater is set in advance and stored in the setting device, and the Do value of the mixed liquid 12 at a predetermined position in the circulatory system 2 is measured using the Do meters 22, 23. Comparator 2 detects the detected value and the setting value of the setting device.
If the detected value of Do is larger than the upper limit of the set value, the movable weir 18 is lowered to reduce the immersion depth l of the rotor 8, the oxygen supply amount is decreased, and the Do value of the mixed liquid 12 is set. lower to the value and vice versa
If the detected value of Do is smaller than the lower limit of the set value,
The movable weir 18 is raised to increase the immersion depth l of the rotor 8, increasing the amount of oxygen supplied and increasing the amount of mixed liquid 12.
The Do value is raised to the set value, and the Do of the mixed liquid 12 is maintained within the range of the set value suitable for biological treatment even if the inflow load conditions of sewage vary.
This allows the Do value to be automatically controlled to the optimum value.

In addition, in the drawings of this embodiment, the movable weir 1
Although the moving means 8 is omitted, the movable weir 18 is made movable by electric power or hydraulic pressure, and outputs an error signal according to the difference between the detected value of Do and the set value compared with the comparator. The movable weir 18 may be moved in response to this. In this case, the movable weir 18 receives the Do error signal from the comparator and moves up and down by about 10 to 20 mm at a time, detects the change in the Do value of the mixed liquid 12 at that position, and further detects the change in the Do value of the mixed liquid 12 at that position. If there is a difference, a feedback circuit that goes up and down can be incorporated to provide a step response.

As explained above, the present invention provides a wastewater treatment system in which wastewater is aerated and fluidized by a horizontal rotor-rotating aeration device installed in a deitch tank forming a circulation path. In addition to providing a flow channel through which the mixed liquid in the circulation path overflows, a movable weir is provided at the entrance of the flow channel to adjust the amount of overflow, and the Do value of the mixed liquid at a predetermined position in the circulation path is detected. The detected value is compared with the set value, and the movable weir is automatically moved according to the difference, changing the water level in the circulation path and adjusting the depth of water immersion of the rotor so that the Do value becomes a predetermined value. Since it is controlled, it has many excellent effects as follows.

(1) Even if the inflow load conditions of wastewater change, the mixed liquid
Since the Do value can be maintained within the optimum range, the quality of the treated water is stable and nitrification and denitrification can be performed extremely well.

(2) Simply raise and lower the movable weir without changing the number of rotors in operation or the rotation speed of the aeration equipment.
Since the amount of oxygen supplied can be adjusted by changing the water level in the circulation path, Do can be controlled extremely easily and inexpensively, and failures are rare.

(3) There is no need to over-aerate, exceeding the required amount of oxygen supply, so there is no waste in power consumption.

(4) It can be applied to existing wastewater treatment equipment without major modifications.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of a wastewater treatment device to which the present invention is applied, and FIGS.
FIG. 4 is a cross-sectional view taken along the arrows - and - in the figure, and is a performance curve diagram showing the relationship between the depth of immersion of the rotor and the amount of oxygen supplied. 1... Datetsu tank, 2... Circulation path, 3... Aeration device, 4... Rotating shaft, 5... Bearing, 6... End plate,
7... Wing plate, 8... Rotor, 9... Motor, 10
... Sewage inflow pipe, 11 ... Distributor pipe,
12...Mixed liquid, 13...Discharge hole, 14...Raw water, 15...Open/close valve, 16...Flow channel, 17...
Opening, 18...movable weir, 19...outflow pipe.

Claims (1)

[Claims] 1. In a Deitzch-type wastewater treatment equipment that uses a rotary rotor to aerate and flow wastewater, the Deitzch tank is provided with a flow channel through which the mixed liquid in the circulation channel overflows, and a flow channel is installed at the entrance of the flow channel. A movable weir is installed to adjust the amount of overflow, and the Do value of treated water at a predetermined position in the circulation path is detected.
The Do value is adjusted by comparing the detected value and the set value, automatically moving the movable weir according to the difference, and changing the water level in the circulation path to adjust the immersion depth of the rotor. A method for controlling the amount of oxygen supplied in a wastewater treatment device, characterized by: