JPS6214324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a plurality of filtration devices used, for example, in sewage treatment, and in particular, to improving the efficiency of operation of filtration devices and saving and controlling power equipment such as pumps and blowers for cleaning. The present invention relates to a cleaning method that is simplified.

Upflow filtration devices have recently begun to be widely used for tertiary treatment of sewage because the filter layer has a high ability to capture suspended solids (SS) and the upper surface is covered with treated water. However, in urban areas, the amount of wastewater treated at a single sewage treatment plant typically reaches several hundred thousand tons, so sewage treatment is carried out by installing dozens of filtration devices in parallel. However, since sewage is highly turbid, it is necessary to clean the filtration device about once a day, and since the flow rate of sewage fluctuates, the filtration device must be quickly cleaned during low flow periods and prepared for high flow times. There is a problem with cleaning timing.

In order to satisfy the above requirements, even if all the filtration devices are divided into groups and the filtration devices in each group are sequentially washed all at once, one cleaning usually requires several washing and draining operations. Since it is necessary to repeat the process several times, it is necessary to start and stop the cleaning equipment such as pumps and blowers each time, which makes the control complicated. Furthermore, as the amount of ss increases, it becomes necessary to adjust the cleaning schedule accordingly and perform cleaning under optimal conditions.

It is an object of the present invention to solve the above-mentioned problems and provide a method for cleaning a filtration device that can be easily adapted to changing cleaning conditions.

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

FIG. 1 shows an upflow filtration device used in the present invention. The filtration device has a pressure regulation tank 1 and a filtration tank 2 located lower than the pressure regulation tank 1, and the pressure regulation tank 1 is connected to a raw water inflow pipe 3,
An overflow pipe 4 and a water level detection device 5 are provided,
The bottom of the pressure regulating tank 1 and the lower part of the filtration tank 3 are connected to the raw water supply pipe 6.
and a valve 7 is provided thereto. During filtration, the valve 7 is opened, raw water to be filtered is injected from the inlet pipe 3, and the water level in the pressure regulating tank 1 is maintained at a height corresponding to the filtration resistance of the filtration tower 2. In this case, the downward flow in the pressure regulating tank 1 has a flow velocity that does not trap air bubbles, that is, 0.125 m/
The capacity of the pressure regulating tank 1 is determined to be less than 1 second, and raw water containing no air bubbles is supplied to the filtration tank 2.

The filtration tank 2 has a support part 9 in which strainers 8 are evenly arranged at the bottom and a filter layer 10 thereon.
consists of a lower support layer 11 made of gravel and a sand layer 12 deposited thereon, and a grid member 13 is provided near the top surface of the sand layer 12 to prevent the sand layer 12 from scattering. The raw water that has flowed into the lower part of the filter tank 2 flows upward through the filter layer 10 from the strainer 8, and during this time, the raw water in the raw water is
Since ss is captured throughout the filter layer, the processing capacity of the filtration tank 2 is extremely large, unlike surface layer filtration in a conventional downward flow type filtration tank. Furthermore, since the grid member 13 is provided, the surface of the sand layer 12 is kept in a stable state without being disturbed even when raw water is passed through it at high speed.

The treated water from which the ss has been removed enters an overflow gutter 14 provided above the filter layer 10, and from there is discharged through a treated water pipe 15 or sent to a reuse site.

Through the above filtration operation, ss is gradually stored in the filter layer 10 and the filtration resistance increases, but this is detected by the water level detection device 5 as an increase in the water level in the pressure regulating tank 1. Instead of the water level detection device 5, a pressure gauge provided at the bottom of the pressure regulating tank 1 may be used to detect the filtration resistance.

When the filter resistance reaches a predetermined value, the filter layer 10 must be washed to restore throughput. For this purpose, a cleaning operation consisting of the following partial steps (a) to (g) is performed.

(a) Draining process Close the valve 7 and open the valve 17 of the drain pipe 16 provided at the bottom of the filtration tank 2. As a result, the water level in the filter tank 2 gradually decreases. When the water level drops to a few centimeters above the surface of the filter layer 10, the valve 17 is closed.
The time to close the valve 17 can be determined by a timer or a level meter 5' that sets the water draining time. Note that when the valve 7 is closed, the water level of the raw water in the pressure regulating tank 1 rises and is returned from the overflow pipe 4 to a raw water tank (not shown).

(b) Air cleaning process After the water draining process is completed, compressed air is supplied into the tank by opening the valve 19 of the air supply pipe 18 provided at the bottom of the filtration tank 2, or by starting the blower (not shown) if the valve 19 is omitted. supply As a result, sand layer 1
2 to remove the suspended matter adhering to the filter medium. At this time, the suspended solids attached to the support layer 11 are also peeled off by the air.

(c) Air/water cleaning process After air cleaning for a certain period of time, valve 7 is opened and raw water is supplied. As a result, an upward flow of a mixture of water and air is generated in the filter layer 10, and the residual suspended solids adhering to the filter layer 10 are further peeled off, and this and the suspended solids peeled off in the air washing step in the previous section are moved upward. Transport. When the water level reaches the vicinity of the overflow gutter 14, the valve 19 is closed to stop the air supply to prevent the filter medium from flowing out, and this process is completed. Closing of the valve 19 can be performed using a timer or a level meter 5' in the same manner as in the draining process.

Note that instead of supplying raw water, the mixed water may be supplied by opening the valve 21 of the washing water pipe 20 whose water source is raw water or treated water. This step may be omitted if unnecessary.

(d) Water washing step After the above step is completed, the valve 21 is opened and raw water is supplied at a flow rate 2 to 5 times the flow rate of raw water supplied during filtration. As a result, cleaning wastewater containing suspended matter is collected in the overflow gutter 14, and from there, it is sent to the drain pipe 22 and the valve 23.
The wastewater is then sent to a washing wastewater treatment facility. In this case, the valve 24 of the treated water pipe 15 is kept closed.

In this step, treated water may be supplied instead of raw water, but this is not a good idea since supplying treated water will reduce the amount of treated water accordingly.

(E) Repeating Steps Steps (a) to (d) are repeated to completely remove the SS trapped in the filter layer 10.

(F) Sand tightening process After completing the process in the previous section, open the valve 17 and remove the filter layer 10.
A downward flow is generated inside the filter, and the filter layer 10, which had been slightly expanded in the previous process, is tightened. For this tightening, it is sufficient to generate even some downward flow, so the valve 17 may be opened for a short time using a timer.

In addition, the drain pipe 16 in this process and (a) process
Runoff water is returned to the raw water tank.

(g) Water disposal process After the sand tightening process is completed, the valve 7 is opened to supply raw water and the treated water is obtained from the overflow gutter 14. However, since it contains some turbidity at the beginning of the filtration process after washing, the water is kept constant. During the period, the valve 24 is closed and the valve 23 is opened to take out the treated water from the drain pipe 22, and then the valve 23 is closed and the valve 24 is opened to begin the filtration process.

Figure 2 shows the above-mentioned upward flow filtration devices F ₁ , F ₂ . . .
... is a control system diagram for operating Fn. The control device C inputs the filtration signal f from each filtration device _F1 ...Fn and the sewage inflow signal g to the sewage treatment plant, and determines when to start cleaning each filtration device _F1 ...Fn. is determined, and control signals for the blower B, cleaning pump P, and each valve V in the cleaning process are output. For this reason, the control device C is provided with an arithmetic unit, a sequence controller, a timer, a relay, and the like.

However, when many filtration devices are operated in parallel, the number of parallels is determined based on the maximum amount of sewage inflow in a day, and the amount of sewage inflow in a day is generally
As shown in the figure, it is highest at noon and lowest early in the morning.
Therefore, when cleaning, for example, the cleaning start time is determined based on the change in the amount of sewage inflow from the previous day, and the cleaning process time on the day, etc., and the cleaning is controlled by taking into account the time when the amount of sewage inflow is small. Device C controls the cleaning process.

In the present invention, the control device F ₁ ......Fn is divided into groups including several filtration devices, and the cleaning process of each filtration device in each group is sequentially shifted in time for each group and between groups. The cleaning process is performed continuously. Each group has a different cleaning start time for the filtration devices that make up the group, but the cleaning process proceeds at the same time.

Figure 4 shows three filtration devices F ₁ , F ₂ , F ₃ and F ₄ ,
1st, 2nd, 3rd including F ₅ , F ₆ and F ₇ , F ₈ , F ₉
The overall cleaning process diagram for Groups A, B, and C is shown.
The cleaning process of each filtration device is combined so that it proceeds in order from the one with the largest filter resistance, and each filtration device undergoes steps A, B, C, and D multiple times (in the figure, 2
After repeating the process (times), the cleaning process is completed at steps H and H.

The time a for the first water removal step A is freely set by a timer, and the total time of steps B and C, the time of step D, and the time of the second and subsequent steps A are set as a fixed time b, respectively. Let c be the total time. Also, within the same group, for example,
The processes are sequentially shifted so that the _first process B of _F2 starts at the same time as the first process C of F1 ends, and the first process B of _F3 starts at the same time as the first process _C of F2 ends. put.

Further, between groups A and B, the processes are shifted in time so that the first process B of F4 starts at the end of the last process _C of _F3 . The same applies to groups B and C.

In such a case, the air supply carried out through steps B and C can be done by simply turning off the valve 19 without stopping the blower.
By simply opening and closing, the first steps B and C of each of F ₁ , F ₂ , and F ₃ are sequentially switched, and then the process continues.
The process switches sequentially to the final steps B and C of F ₁ , F ₂ , and F ₃ . Similarly, when the last step of _F3 is completed, the process switches to the first step of _F4 . Thus, the blowers in groups A, B, and C are operated continuously.

The supply of cleaning water in step 2 is similarly carried out by simply opening and closing the valve 21, with the pump continuously operating through _F1 to _F9 .

Now, if the total cleaning time of _F1 is T ₀ , then T ₀ = a + (3m-1) b + c, where m is the number of times steps A, B, C, and D are repeated. In the example in Figure 4, m = 2. Therefore, T ₀ = a + 5b + c, and the cleaning time T ₁ for the entire group A is T ₁ = T ₀ + 2b.In other words, the cleaning time for one filtration device is only 2b.
It is possible to complete the cleaning of three filtration devices by adding only .

Also, the difference in cleaning start time (starting time) between groups A and B is T=T ₁ - (a+b+c)=6b Continuous cleaning time for n groups A, B, C...
Tn becomes Tn=T ₀ +(n-1)T.

For example, a=8 minutes, b=7 minutes, c=5 minutes, m=
2. If n=2, T ₀ = 48 minutes, T ₁ = 62 minutes, T = 42 minutes, T ₂ = 102 minutes T ₁ /T ₀ = 1.291, T ₂ /T ₀ = 2.167, that is, 3 pieces Or the cleaning time for 6 filtration devices is 1
1.291 times the cleaning time of each filtration device or
2.167 times is sufficient, and the overall cleaning time can be greatly shortened. In this case, the times of steps A, H, and G can be set freely, but the influence on the total cleaning time is extremely small.

If the blower has a structure that allows for shut-off operation by using a multi-stage turbo, the supply of cleaning water and air will be stopped at the last part of steps B and C, and the valve 16 will be opened to drain the water containing turbidity downward. It is possible to
This can facilitate water washing in step 2.

Furthermore, if each cleaning process is staggered in time as described above, the power equipment such as the blower or air compressor in processes B and C, and the cleaning water supply pump in process D will be one each for each continuous cleaning process. is enough,
Moreover, since this can be operated continuously and water can be supplied to each filtration device simply by switching the valves, there is little load variation in the power equipment, and control and maintenance are easy.

When applying the present invention to a sewage treatment facility that has a large number of filtration devices, the filtration devices are divided into a number of systems capable of continuous cleaning during periods when the amount of sewage inflow is small, and each system is run in parallel. Continuous cleaning is sufficient. In this case, if data regarding the cleaning power equipment and the control of each valve, such as the cleaning start time and the time required for each cleaning process, is incorporated into the minicomputer, it becomes possible to automate the cleaning of the entire filtration device and perform optimal cleaning control.

The present invention has the above-mentioned configuration, and can quickly clean a large number of filtration devices with the minimum amount of cleaning equipment.Especially during times of the day when the amount of sewage inflow is small, such as during sewage treatment, the amount of inflow of sewage can be maximized. It has the effect of quickly and efficiently cleaning a large number of filtration devices commensurate with the amount of sewage inflow.
This is an effective cleaning method when automating the cleaning of filtration equipment in large-scale sewage treatment facilities.

Note that the present invention can also be applied to cleaning a downward flow filtration device, except for the process.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic structural explanatory diagram of an upflow filtration device, FIG. 2 is a control system diagram for operating a large number of upflow filtration devices, and FIG.
The figure is a diagram of fluctuations in sewage inflow at a sewage treatment plant.
The figure is a cleaning process diagram. 2, F ₁ to Fn...filtration device, A, B, C... group, B, H, D... partial process.

Claims (1)

[Scope of Claims] 1. A method for cleaning a filtration device in which sewage is treated using a large number of filtration devices operated in parallel, including a partial step that requires at least supply of cleaning water and air during the cleaning process of each filtration device. The same partial processes of the partial processes of each filtration apparatus do not overlap, and the corresponding partial processes of the next stage filtration apparatus start at the same time as the partial process of the previous stage filtration apparatus ends. A method for cleaning a filter device, characterized in that the cleaning step for each filter device is started, and the cleaning steps for a plurality of filter devices are progressed. 2. In a method for cleaning filtration equipment that treats sewage using a large number of filtration equipment operated in parallel, all filtration equipment is divided into groups containing a plurality of filtration equipment, and during the cleaning process of each filtration equipment in each group, at least one The same partial processes in the partial processes of each filtration device do not overlap, and when the partial process in the previous stage filtration device is completed, the corresponding partial steps in the next stage filtration device are completed. The cleaning process of each filtration device is started with a time difference in order so that the partial processes start, and the cleaning process of a plurality of filtration devices is progressed. A method for cleaning a filtration device, characterized in that a time difference is provided so that the corresponding first partial step of the filtration device to be cleaned first in the next stage group starts when the last partial step of the filtration device of the next stage group is completed.