JPS6314680B2 - - 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, it is more energy-saving than the aeration method or activated sludge method.
A wastewater treatment device called an oxidation date system, which is easy to operate and manage, is widely used. 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 it is operated under the same operating conditions as originally set, the amount and quality of wastewater flowing in, especially
It was not possible to respond appropriately to fluctuations in inflow load conditions due to changes in BOD, etc., and the
It has been extremely difficult to optimally control the value to a predetermined value. Therefore, under low load conditions, overaeration will occur, and not only will nitrification reaction proceed and denitrification will not occur, but it will also cause problems such as a decrease in pH value, and furthermore, it will consume unnecessary power. However, under high load conditions, Do is insufficient, nitrification reactions and denitrification are not promoted, and the quality of treated water deteriorates, among other drawbacks.

The present invention was made in order to improve the above-mentioned conventional drawbacks, and the present invention calculates the oxygen transfer rate from the oxygen uptake rate of activated sludge detected at a predetermined position in the circulation path, and then calculates the oxygen transfer rate of the treated water at the calculated oxygen transfer rate. Calculate the necessary immersion depth of the rotor corresponding to the set value of Do, change the water level in the circulation path according to that value, adjust the immersion depth of the rotor, and make the Do value a predetermined value. Oxygen supply in wastewater treatment equipment is characterized by a system that can optimally control the Do value of treated water to a predetermined value even if the inflow load conditions of sewage fluctuate. The purpose is to provide a method for controlling the amount.

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. This constitutes the rotor 8. By driving the motor 9, the rotor 8 is rotated clockwise as shown by the arrow in FIG. 2, thereby aerating and flowing the mixed liquid. 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 , and the raw sewage 14 led to the distributor pipe 11 via the sewage inflow pipe 10 flows through 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. teeth,
A movable weir 18 is provided which can be moved vertically 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 overflows over the upper edge of the movable weir 18 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, and the mixed liquid 12 overflowing into the flow channel 16 is guided through the outflow pipe 19 to a sedimentation pond (not shown) or the like. The mixed liquid 12 led to the sedimentation tank or the like is separated and concentrated in the sedimentation tank or the like, and is appropriately returned to the deitch tank 1 as return sludge via the return means, where it is aerated. In addition, circulation path 2
In order to raise the water level inside, the movable weir 18 can be pulled up to raise 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 and the oxygen transfer rate N using the Do value of the treated water as a parameter. Depth l and oxygen transfer rate N
There is a close relationship depending on the Do value of the treated water.
As the immersion depth l of the rotor 8 increases, the oxygen transfer rate N also tends to increase as shown in the figure. Therefore, the relationship between the immersion depth l of the rotor 8 corresponding to the diameter, length, and rotation speed of the rotor 8 of the aeration device 3 to be installed and the oxygen transfer speed N was tested in advance using the Do value of the treated water as a parameter. If the performance curve diagram shown in Fig. 4 is obtained, the immersion depth l of the rotor 8
By changing , the oxygen transfer rate N can be arbitrarily changed even if the Do value of the treated water is constant, and conversely, even if the oxygen transfer rate N is constant, the immersion depth l of the rotor 8 can be changed. By changing , it becomes possible to arbitrarily change the Do value of treated water.

That is, in the performance curve shown in Figure 4,
For example, if the Do value of the treated water is controlled to 2 ppm and the immersion depth l of the rotor 8 is 150 mm, the oxygen transfer rate N will be approximately 17 Kg-O ₂ /Hr. In addition, by operating the rotor 8 at a submergence depth l of 200 mm, the oxygen transfer speed N is
When the Do value of treated water is 5ppm at 13Kg−O ₂ /Hr,
When it is desired to keep the oxygen transfer rate N constant and lower the Do value to 2 ppm, it is understood from the performance curve shown in the figure that the immersion depth l of the rotor 8 should be set to 100 mm.

Therefore, in the present invention, a Do value suitable for biological treatment of wastewater is set in advance, and the relationship between the oxygen transfer rate N and the immersion depth l of the rotor 8 corresponding to the set Do value of the treated water is determined in advance. is stored in the microcomputer, and on the other hand, the oxygen uptake rate r of the activated sludge in the mixed liquid 12 at a predetermined position in the circulation path 2 is detected with an r _r meter, and the oxygen transfer rate N' is calculated from the detected value in the microcomputer. Calculate by computer. The oxygen transfer rate _N per unit volume of the mixed liquid 12 _is determined _by
= K _La (C _S − C _L )...It is expressed by equation (1). In addition, the overall oxygen transfer coefficient K _La is calculated as follows, where r is the oxygen uptake rate of activated sludge by microorganisms, and C _SW is _the oxygen saturation concentration in the mixed liquid. (C _SW −C _L ) …It is expressed by equation (2).

Therefore, if we detect the oxygen uptake rate r using an r _r meter, then
The oxygen transfer rate N can be determined from equations (1) and (2).

dc/dt=K _La (C _S −C) − r _r …(3) dc/dt; Oxygen concentration change rate In steady state, dc/dt=0, so r _r =K _La (C _S −C) … (4) Also, in the steady state, r _r (oxygen uptake rate) and N (oxygen transfer rate) are balanced, so N=K _La (C _S −C) …(5) In the present invention, (4 ), the r _r in the liquid, the C and liquid temperature at that time are detected, and the C _S value and K _La at that time are detected.
Find the value. (The r _r value and the N value at this point are equal.) Next, the preset Do value (=C ^* ) and C _S ,
Substitute the K _La value into equation (5) to find the N value.

N′=K _La (C _S −C ^* ) Next, calculate the necessary immersion depth at the oxygen transfer rate N′ calculated from the relationship between the set Do value and the rotor immersion depth (Figure 4), and The movable weir is automatically moved accordingly to change the water level.

On the other hand, microcomputers are equipped with processed water.
Since the relationship between the oxygen transfer speed N and the immersion depth l of the rotor 8 corresponding to the set value of Do is stored,
Mixed liquid 12 at the calculated oxygen transfer rate N'
The rotor 8 required to make the set Do value
The submergence depth l' is calculated using a microcomputer. That is, for example, set the Do value to 2ppm,
When the calculated oxygen transfer rate N' is 15Kg-O ₂ /Hr, as is clear from Figure 4, the Do value is
Rotor 8 immersion depth required to maintain 2ppm
l' will be calculated as 125mm. Therefore, the present invention automatically moves the movable weir 18 according to the immersion depth l' of the rotor 8 calculated in this way,
By changing the water level in the circulation path 2, the immersion depth l of the rotor 8 is adjusted to be l', so that the Do of the mixed liquid 12 can be adjusted to be suitable for biological treatment even if the inflow load conditions of sewage fluctuate. It is possible to maintain the Do value within the set value range and automatically optimally control the Do value.

In addition, in the drawings of this embodiment, the movable weir 1
Although the means of movement 8 is omitted, the movable weir 18 is movable by electric power or hydraulic pressure, and corresponds to the necessary immersion depth l' of the rotor 8 calculated by a microcomputer. The movable weir 18 may be moved in response to the signal until the submersion depth l of the rotor 8 becomes l'. In this case, the oxygen uptake rate r of the activated sludge in the mixed liquid 12 at a predetermined position in the circulation path 2 is intermittently detected at predetermined time intervals.

As explained above, the present invention provides a wastewater treatment apparatus in which wastewater is aerated and fluidized by a horizontal rotor-rotating aeration device provided in a deitsch tank forming a circulation path. In addition to providing a flow channel through which treated water overflows, a movable weir is installed at the entrance of the flow channel to adjust the amount of overflow, and the oxygen uptake rate of activated sludge in the treated water at a predetermined position within the circulation path is detected. Then, the oxygen transfer rate is calculated from the detected value, and from the relationship between the oxygen transfer rate and the immersion depth of the rotor, which corresponds to the preset Do value of the treated water, the necessary rotor transfer rate at the calculated oxygen transfer rate is calculated. The immersion depth of the rotor is calculated, and the movable weir is automatically moved according to the calculated immersion depth of the rotor, and the water level in the circulation path is changed to adjust the immersion depth of the rotor so that the Do value becomes a predetermined value. Since the height is adjusted, it has many excellent effects as described below.

(1) Even if the wastewater inflow load conditions change, the treated water
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.
The water level in the circulation path can be changed, and the movable weir is automatically and accurately moved so that the rotor is at the calculated immersion depth necessary to maintain the treated water Do at the set value. ,
Do control is accurate, extremely easy and inexpensive, 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 - and - lines in the figure, and is a performance curve diagram showing the relationship between the immersion depth of the rotor and the oxygen transfer rate using the Do value of the treated water as a parameter. 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 oxygen uptake rate of the activated sludge in the mixed liquid at a predetermined position in the circulation path is detected, and the oxygen transfer rate is calculated from the detected value, and the preset treated water is From the relationship between the oxygen movement speed and the rotor immersion depth corresponding to the set value of Do, calculate the required rotor immersion depth at the calculated oxygen movement speed, automatically move the movable weir accordingly, 1. A method for controlling the amount of oxygen supplied in a wastewater treatment device, characterized in that the depth of immersion in the rotor is adjusted by changing the water level in the circulation path so that the Do value becomes a predetermined value.