JP2001050927A - Cleaning apparatus for residual chlorine analyzer of discharge water in sewer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cleaning apparatus which prevents a drop in the measurment accuracy of the concentration of residual chlorine and which extends the cycle interval of an inspection maintenance operation to be longer, by a method wherein the apparatus as a whole is maintained to be always clean. SOLUTION: In this cleaning apparatus, a water-collecting device 1 which collects a sample as discharge water from a river water discharge conduit is provided, and a residual chlorine analyzer 2 which measures residual chlorine in the sample as the discharge water collected by the water collecting device 1 is provided. In the cleaning apparatus, a cleaning-water supply means 4 is provided, a measuring-tank cleaning means to which cleaning water is introduced from cleaning-water supply means 4 and by which the inside of a cleaning tank 24 installed at the residual chlorine analyzer 2 and a measuring electrode are cleaned is provided, a sand-filter device cleaning means by which the inside of a sand filtration device 22 installed at the residual chlorine analyzer 2 and sand are cleaned is provided, a container 13 which is installed at the watercollecting device 1 is provided, a water-collecting device cleaning means by which a water collecting pump 14 and pipes in respective parts are cleaned is provided, and a control device 6 which controls the respective cleaning means is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a residual chlorine meter for measuring the residual concentration of chlorine injected for sewage treatment in a sewage treatment plant for treating sewage for discharge into rivers. In more detail, in a device that continuously measures the residual chlorine concentration of the effluent to the treated river using the polarographic method, microorganisms and interfering substances that cause measurement errors and decrease in sensitivity stay or The present invention relates to a cleaning apparatus for a residual chlorine meter that always keeps the entire apparatus clean in order to suppress the adhesion.

[0002]

2. Description of the Related Art Conventionally, as a cleaning device for a residual chlorine meter,
There has been an ozone cleaning method for periodically cleaning the inner wall of a measuring tank and a measuring electrode. This ozone cleaning method is a method in which ozone water in which ozone is dissolved is poured into a measuring tank as cleaning water, and the interfering substances and microorganisms attached by the oxidizing action of ozone are oxidized and washed away. There is also a method of cleaning the inside of a measurement tank with enclosed glass or ceramic beads. The following methods were used for washing with beads.
The first method is a method of agitating the inside of the measuring tank by a stirrer or jetting of washing water to wash the interfering substances and microorganisms attached to the measuring electrode and the inner wall of the measuring tank. The second method is a method in which beads are sealed so that the measurement electrode is buried, and the measurement electrode itself is constantly rotated or vibrated to polish the measurement electrode. In the second method using beads, the measurement electrode is polished by rotating in the beads.
The measurement can be performed while (washing), but the inner wall of the measuring tank cannot be washed.

[0003]

According to the conventional cleaning method as described above, only the inside of the measuring tank including the measuring electrode can be cleaned. When the microorganisms adhere to and propagate on the uneven portion, the propagated microorganisms flow out into the sample of the effluent that passes through the pipes and pumps, and the concentration of the microorganisms becomes higher than the actual effluent. Microorganisms themselves cause residual chlorine consumption, so that the higher the concentration of microorganisms, the more residual chlorine in the effluent sample is consumed. Therefore, there was a problem that the residual chlorine concentration of the sample was lower than the actual residual chlorine concentration of the effluent. For this reason, inspection and maintenance of the entire apparatus must be performed frequently, and if inspection and maintenance is neglected, there has been a problem that the measurement accuracy of the residual chlorine concentration is reduced. In addition, the method using ozone requires an expensive ozone generator, but since the amount of ozone generator used is limited to cleaning the inside of the measuring tank, it is not possible to clean other parts. In addition, since ozone has an extremely strong oxidizing power, not only does it oxidize microorganisms and interfering substances, but also there is a problem that each part of the apparatus to be ozone-washed is quickly deteriorated.

[0004] The present invention always keeps the entire apparatus clean and suppresses the growth of microorganisms in the entire apparatus, thereby preventing a decrease in the accuracy of the residual chlorine concentration measurement by the polarographic method and extending the cycle of inspection and maintenance. The purpose is to extend.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and a water sampling device for sampling a sample of discharged water from a river discharge culvert, and a water sampling device using the water sampling device. A residual chlorine meter comprising: a residual chlorine meter that measures and outputs residual chlorine of a sample of the discharged effluent;
Cleaning water supply means, measurement tank cleaning means for introducing cleaning water from the cleaning water supply means, for cleaning the inside of the measurement tank and the measurement electrode provided in the residual chlorine meter, and provided in the residual chlorine meter. Sand filtering device cleaning means for cleaning the inside of the sand filtration device and sand, water sampling device cleaning means for cleaning a strainer, a water sampling pump and piping of each part provided in the water sampling device, and a cleaning device for these And a control device for controlling the

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a cleaning apparatus according to the present invention. 1 is a water sampling apparatus for collecting a sample of effluent from a river discharge culvert 11, 2 is a residual chlorine meter, 3 is a residual chlorine meter for measuring reagents. 1 is a reagent supply device for supplying to 1, 4 is a cleaning water supply device for supplying cleaning water to the residual chlorine meter 1 and the water sampling device 2, 5 is a cleaning agent supply device for supplying a cleaning agent when the sand filtration device 22 is washed. , 6 are control devices for controlling these devices. In FIG. 1, the solid line represents the piping of the residual chlorine measurement system, the broken line represents the piping of the cleaning liquid (chemical) supply system, and the two-dot chain line represents the wiring of the control system.

In the water sampling apparatus 1, a water sampling pipe 12 provided with a tip thereof facing a river discharge channel 11 is connected to a water sampling pump 14 via a strainer 13.
Is connected to a sand filtration device 22 of the residual chlorine meter 2 through a pipe 20. On the opposite side of the pipe 20, a drain pipe 29 located downstream from the water sampling pipe 12 is provided to drain excess effluent water sample or washing water.
Is connected. As the water sampling pump 14, a pump that stops operation as soon as possible when stopping from the operation state is used.

As shown in FIG. 3, the sand filter 22 of the residual chlorine meter 2 is filled with sand 22b to a depth of about half of a water tank 22a, and a sample of discharged water is poured from the upper part of the water tank 22a. It is supposed to be. Further, a filtration outlet 22d provided at a lower portion of the water tank 22a is provided with a mixing pump 23 for mixing a reagent for measurement and a sample of effluent at a specified ratio.
Is connected to one suction port of the water tank 22a.
When the water level is full, the overflow pipe 22c
Is connected. The overflow pipe 22c is connected to a drain pipe 19 located downstream of the water sampling pipe 12 of the river discharge channel 11. The discharge port of the mixing pump 23 is connected to the measuring tank 24, and the outlet of the measuring tank 24 is connected to the drain pipe 19.

As shown in FIG. 4, glass or ceramic beads 24a are sealed in the measuring tank 24, and the measuring electrodes 24b are disposed so as to be buried in the beads 24a and rotate for rotation. Drive 24
d is provided. In addition, a nozzle 24c for injecting cleaning water into the inside facing the bottom of the measuring tank 24 is provided. The residual chlorine measurement signal output from the measurement tank 24 is connected to the control device 6 via an amplifier circuit (not shown) built in the converter 25. This converter 25 is further connected as a cleaning control output to a fifth solenoid valve 31 described below via a cleaning output terminal 26 for controlling cleaning of the measuring tank 24,
It is connected to the control device 6 via a control output terminal 27 for controlling the start of the cleaning control.

The reagent supply device 3 is connected to a water supply (not shown), and a pure water generator 32 for generating pure water, a reagent preparation tank 3
3. A transfer pump 34 and a reagent tank 35 for storing the prepared reagent are sequentially connected, and the reagent tank 35 is connected to the other suction port of the mixing pump 23.

The cleaning water supply device 4 includes a cleaning water tank 36 for storing tap water from a water supply (not shown), and a cleaning water supply device for supplying cleaning water (tap water) to the residual chlorine meter 2 and the water sampling device 1. The washing water tank 36 is provided with a faucet (not shown) which automatically opens when the water level drops and supplies tap water. The discharge port of the cleaning water pump 37 is connected to the pipe 15 between the strainer 13 and the water sampling pump 14 via the cleaning water pipe 51, and to the pipe 16 on the discharge side of the water sampling pump 14 via the cleaning water pipe 52. A water pipe 53 is connected immediately before the sand filter 22 of the pipe 20, and a washing water pipe 54 is connected to a filter outlet 22 d of the sand filter 22. It is connected to the nozzle 24c. These washing water pumps 3
Cleaning water piping 51, 52, 53, 54, 5 from 7 to each part
5 are the first to the first for supplying and stopping the washing water, respectively.
Five solenoid valves 17, 18, 21, 30, 31 are provided. These solenoid valves 17, 18, 21, 30, 31 are normally closed type.

The cleaning agent supply device 5 includes a cleaning agent tank 38 storing a hypochlorite (eg, NaClO) solution as a cleaning agent and a cleaning agent supply pump 39. The fourth solenoid valve 30 is connected to the sand filtration device 22 on the way of the washing water pipe 54 to the filtration outlet 22 d of the filtration device 22.

As shown in FIG. 2, the control device 6 is provided with a memory 40 for holding and outputting the residual chlorine measurement signal as necessary, and the output of the memory 40 is a display device 41 for displaying the residual chlorine concentration. And a signal output terminal 59 for outputting to a central monitoring station (not shown). The control device 6 includes the converter 2
Sequencer 42 connected to control output terminal 27 from 5
The control output of the sequencer 42 is connected to the drive contacts 43 to 49 and the hold control terminal of the memory 40. The drive contact 43 is connected to the water sampling pump 14, the drive contact 44 is connected to the washing water pump 37, the drive contact 45 is connected to the detergent pump 39, the drive contact 46 is connected to the first solenoid valve 17 provided in the washing water pipe 51, The drive contact 47 is connected to the second solenoid valve 18 provided in the washing water pipe 52 by a drive contact 48.
Corresponds to the third solenoid valve 21 provided in the washing water pipe 53,
The drive contact 49 is connected to the fourth solenoid valve 30 of the washing water pipe 54. The drive contact 43 of the water sampling pump 14 is a normally closed type, and the other drive contacts 44 to 49 are a normally open type.

Next, the operation of the apparatus having the above configuration will be described. First, the reagent supply device 3 and the washing water supply device 4
Will be described. The reagent supply device 3 removes chlorine and other impurities from tap water by a pure water device 32 to generate pure water, and stores the pure water in a reagent preparation tank 33. When a prescribed amount of pure water accumulates in the reagent preparation tank 33, a corresponding amount of reagent is charged and stirred, and is transferred to the reagent tank 35 by the transfer pump 34. The washing water supply device 4 is used for washing the device and so on so that a predetermined amount of tap water is always stored. When the water level drops, a water faucet (not shown) is automatically opened to supply tap water. Be done

Next, the operation at the time of measuring the residual chlorine will be described. When measuring the residual chlorine, the converter 25 does not output the drive control signals from the cleaning output terminal 26 and the control output terminal 27, and the respective drive contacts 43 to 49 maintain the normal state. Therefore, the normally closed drive contact 33 is closed to operate the water sampling pump 14, and the normally open drive output contacts 44 to 49 are open. The first to fifth solenoid valves 17, 18, 21, 30, and 31 for stopping and supplying (water) are all closed, and the cleaning water pump 37 and the cleaning agent pump 39 are stopped.
As long as the present apparatus is operating, the mixing pump 23 continues to operate irrespective of measurement or cleaning. In this measurement operation state, as shown by the thick line in FIG.
Thus, a sample of the discharged water is collected from the river discharge channel 11 through the water sampling pipe 12, and trash and earth and sand are removed by the strainer 13 and sent to the sand filtration device 22. The effluent sample which is not completely removed by the strainer 13 is removed by the sand filtration device 22. Is done.

The effluent sample from which the turbid matter has been removed is sucked by the mixing pump 23 and mixed with the reagent stored in the reagent tank 35 at a specified ratio, and mixed in a specified ratio.
Sent to In the measuring tank 24, the residual chlorine concentration of the sample of the discharged effluent is measured by a polarographic method, amplified to an appropriate size (for example, 4 to 20 mA) by an amplifier built in the converter 25, and Output to the memory 40. Even during this measurement, the measurement electrode continues to rotate, and is polished (washed) by the beads 24a so that a uniform diffusion layer can always be maintained on the measurement electrode surface. In this measurement state, the memory 40 outputs the input residual chlorine measurement signal as it is to the display device 41 for display, and transmits the signal to the central monitoring station via the signal output terminal 59.

Next, the cleaning operation will be described. The cleaning is performed, for example, at intervals of 30 minutes, and is started when a drive control signal is output from the converter 25 to the cleaning output terminal 26 and the control output terminal 27. When a drive signal is output from the cleaning output terminal 26, the fifth solenoid valve 31 is opened. When a control signal is output from the control output terminal 27 at the same time, the sequencer 42 starts opening / closing control of the contacts 43 to 48. The sequencer 42 first outputs a hold signal to the hold control terminal of the memory 40, and maintains the output measurement signal at the value immediately before the start of cleaning until the cleaning operation is completed.

Then, the measuring tank 24 is washed for 60 seconds. The cleaning of the measuring tank 24 is performed by outputting a drive signal from the cleaning output terminal 26, whereby the fifth solenoid valve 31 is opened, the drive contact 44 is closed, and the cleaning water pump 37 starts operating. As shown by, washing water (tap water) is jetted from the washing water supply device 4 into the measuring tank 24 from the nozzle 24c as a jet stream. Then, the inside of the measuring tank 24 is stirred, and the inner wall and the measuring electrode are washed by the washing water and the enclosed beads 24a. The injected washing water is drained to the river discharge culvert 11 via the water distribution pipe 19. When the cleaning of the measuring tank 24 is completed, the drive signal from the cleaning output terminal 26 stops and the fifth solenoid valve 31 closes.

Seven seconds later than the start of washing of the measuring tank 24, backward washing of the sand filter 22 is performed for 5 minutes. When the sand filter 22 is washed, the drive contact 49 is closed and the fourth solenoid valve 3 is closed.
0 is opened, the drive contact 45 is closed, and the cleaning agent pump 39 is closed.
Starts driving. Then, as shown by the thick line in FIG.
Cleaning water mixed with a cleaning agent is sprayed from a filtration outlet 22d of the sand filtration device 22 to wash the turbid matter trapped in the sand 22b by the backward cleaning and to clean the inner wall of the water tank 22a. The washing water after the washing is drained from the overflow pipe 22c to the river discharge culvert 11 via the water distribution pipe 19. At the same time, the cleaning water mixed with the cleaning agent is sucked into the mixing pump 23, and the inside of the mixing pump 23 is also cleaned. The washing water that has washed the mixing pump 23 is drained from the water distribution pipe 19 to the river discharge culvert 11 via the measuring tank 24.

At the same time as the washing of the measuring tank 24 is started, the driving contact 43 opens to stop the operation of the water sampling pump 14. However, due to the water hammer phenomenon caused by the sudden stop of the flow, microorganisms adhering to the inner wall of the pipe are removed. Interfering substances peel to some extent. Five seconds after the pump 14 stopped, the water pump 1
The forward cleaning of the pipe 20 between the sand filter 4 and
Performed for 0 seconds. In this cleaning, the driving contact 47 is closed, the second solenoid valve 18 is opened, and the cleaning water is supplied from the cleaning water supply device 4 to the pipe 20 in the forward direction as shown by the thick line in FIG. Will be The washing water that has washed the pipe 20 passes through the sand filtration device 22 and is drained to the river discharge culvert 11 via the overflow pipe 22 c and the water distribution pipe 19.

Next, the reverse cleaning of the pipe 20 is performed for 60 hours.
Done for seconds. This back washing is performed by opening the drive contact 47 and closing the second solenoid valve 18, closing the drive contact 48 and opening the third solenoid valve 21, and as shown by the thick line in FIG.
The cleaning water is supplied to the cleaning water supply device 4 in the reverse direction, and the cleaning is performed. The washing water obtained by backwashing the pipe 20 is drained to the river discharge culvert 11 via a water pipe 29.

Next, the water sampling pipe 12 and the strainer 13
Is performed for 60 seconds. In this back washing, the drive contact 47 is opened, the second solenoid valve 18 is closed, and the drive contact 46
And the first solenoid valve 17 is opened. Then, as shown by the thick line in FIG. 8, the washing water is supplied from the washing water supply device 4 to the water sampling pipe 12 and the strainer 13 in the reverse direction to perform washing. By this back washing, dirt and earth and sand filtered by the strainer 13 are washed and discharged to the river discharge culvert 11.

Next, the water sampling pump 14 is washed for 20 seconds. The cleaning of the water sampling pump 14 is performed by
Is closed and the water sampling pump 14 is operated. Then, as shown by the thick line in FIG. 9, the cleaning water is supplied from the cleaning water supply device 4 to the pump 14, and the cleaning is performed. Wash water that has washed the water sampling pump 14 is drained to the river discharge culvert 11 via a water pipe 29. Excess washing water is drained to the river discharge channel 11 through the strainer 13 and the water sampling pipe 12.

During the washing of the pipe 20 in the forward direction and the backward direction, the washing of the water sampling pipe 12 and the strainer 13 in the backward direction, and the washing of the water sampling pump 14, the sand filter 22 is washed in parallel. I have. When all of these washings are completed, the drive contacts 44 and 45 are opened, the operation of the cleaning agent pump 39 and the washing water pump 37 is stopped, the drive contact 46 is opened, and the first solenoid valve 17 is closed. Then, all the drive contacts return to the state at the time of the measurement of the residual chlorine, but until the washing water in the measuring tank 24, the sand filtration device 22, the water sampling pump 14 and the piping of each part is replaced by the sample of the discharged water. , Sequencer 4
2 keeps outputting the hold signal to the hold control terminal of the memory 40 and maintains the output measurement signal at the value immediately before the start of cleaning. After a lapse of time sufficient to complete the replacement of the effluent with the sample, the output of the hold signal to the memory 40 is released, and the measurement signal of the measured residual chlorine is output from the memory 40 again. Then, the operation returns to the normal residual chlorine measurement state.

In the above-described embodiment, the conventional cleaning device for cleaning the measuring tank includes the pipe 20 of the water sampling device 1 and the water pump 1.
4 was added, so that the cleaning was started by a signal output from the converter 25 provided in the residual chlorine meter 2, but the present invention is not limited to this, and the control is not limited to this. The sequencer 42 provided in the apparatus 6 may perform control from the start to the completion of all cleaning including cleaning of the measurement tank.

In the above embodiment, the tap water as the washing water is temporarily stored in the washing water tank 36 and the washing water pump 3
Although the supply is performed at 7, the supply may be performed directly from the water supply as long as a sufficient amount of water and water pressure can be obtained during the cleaning operation. When the tap water is stored in the wash water tank 36, the chlorine concentration of the stored tap water decreases with time. Therefore, the tap water is stored for a long time in cleaning other than the sand filtration device 22 in which the cleaning agent is mixed during cleaning. In washing with tap water, the effect of removing chlorine-consuming substances such as microorganisms is reduced. Therefore, it is necessary to store tap water in the washing water tank 36 according to the washing cycle.

[0027]

According to the present invention, in addition to washing the measuring tank, the sand filter and the pump and piping of the water sampling apparatus for supplying the sample of the discharged water to the residual chlorine meter are also washed.
Microorganisms and interfering substances are extremely unlikely to accumulate in each part of the apparatus, and the cycle of inspection and maintenance can be greatly extended. In particular, the strainer 13 and the water sampling pipe 12 are washed by back washing, and the pipe 20 from the water sampling pump to the sand filtration device is made to wash by flowing the washing water in both the forward and reverse directions. Microbes and interfering substances are less likely to accumulate at seams such as pipes, etc., which are insufficient when cleaning in only the direction is effective, and the cleaning effect is high.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a residual chlorine meter cleaning apparatus of the present invention.

FIG. 2 is a block diagram showing a control device in FIG.

FIG. 3 is an explanatory view showing the sand filtration device in FIG. 1;

FIG. 4 is an explanatory view of a measuring tank in FIG.

FIG. 5 is an explanatory diagram showing a flow of a sample of effluent at the time of measuring residual chlorine by the residual chlorine meter cleaning device of the present invention.

FIG. 6 is an explanatory diagram showing the flow of the washing water when the sand filtering device, the measuring tank, and the mixing pump are washed by the residual chlorine meter washing device of the present invention, and when the pipe 20 is washed in the forward direction.

FIG. 7 is an explanatory diagram showing a flow of cleaning water when the piping 20 of the water sampling apparatus is reversely cleaned by the residual chlorine meter cleaning apparatus of the present invention.

FIG. 8 shows a water sampling pipe 12 provided by the apparatus for cleaning a residual chlorine meter according to the present invention.
FIG. 4 is an explanatory diagram showing a flow of cleaning water when cleaning the strainer 13.

FIG. 9 is an explanatory diagram showing a flow of cleaning water when the water sampling pump is cleaned by the residual chlorine meter cleaning device of the present invention.

[Explanation of symbols]

1 ... water sampling device, 2 ... residual chlorine meter, 3 ... reagent supply device, 4
... Washing water supply device, 5 ... Cleaning agent supply device, 6 ... Control device, 11 ... River culvert, 12 ... Sampling pipe, 13 ... Strainer, 14 ... Sampling pump, 15, 16 ... Piping, 17 ... First
Solenoid valve, 18: second solenoid valve, 19: water pipe, 20: piping, 21: third solenoid valve, 22: sand filtration device, 23: mixing pump, 24: measuring tank, 25: converter, 26: cleaning Output terminal, 27: control output terminal, 28: measurement signal output terminal,
29 ... drain pipe, 30 ... fourth solenoid valve, 31 ... fifth solenoid valve,
32 ... pure water device, 33 ... reagent preparation tank, 34 ... transfer pump, 35 ... reagent tank, 36 ... wash water tank, 37 ... wash water pump, 38 ... wash agent tank, 39 ... wash agent pump, 40 ... memory, 41: display device, 42: sequencer, 43 to 49: drive contacts, 51, 52, 53, 54,
55: Cleaning water pipe, 59: Measurement signal output terminal point.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 33/18 106 G01N 27/46 316Z

Claims (5)

[Claims] 1. A residual water sampling device for collecting a sample of effluent from a river discharge culvert, and a residual chlorine meter for measuring and outputting residual chlorine of a sample of effluent water collected by the water sampling device. In a chlorine meter, a measuring tank cleaning device for cleaning the inside of a measuring tank and a measuring electrode provided in the residual chlorine meter, and a sand filter for cleaning the inside of a sand filtering device and sand provided in the residual chlorine meter. A device cleaning device, a water sampling device cleaning device for cleaning a strainer, a water sampling pump and piping of each part provided in the water sampling device, a cleaning water supply device for supplying cleaning water to these cleaning devices, and a cleaning device And a control device for controlling the amount of residual chlorine in the sewage discharge water. 2. A measuring tank cleaning device comprising: a nozzle for injecting cleaning water into a measuring tank connected to a cleaning water supply device;
The sand filtering device washing device is connected to the washing water pump so that washing water is sprayed from a filter outlet provided at a lower portion of the sand filtering device to the inside, and the water sampling device washing means includes a strainer and a water sampling pump. The washing water pump is connected immediately after the sampling pump and immediately before the sand filtration device, and the washing water is supplied from the washing water pump to each part. 2. A residual chlorine meter cleaning apparatus for sewer discharge water according to claim 1, wherein an electromagnetic valve is provided in each of the pipes, and the electromagnetic valve, the washing water pump, and the water sampling pump are controlled by a control device. 3. The cleaning of the pipe between the water sampling pump and the sand filtration device is performed in a forward direction in which the cleaning water is supplied from the water sampling pump, and in a reverse direction in which the cleaning water is supplied from the sand filtration device. 3. The apparatus for cleaning a residual chlorine meter in sewer effluent according to claim 2, wherein the directional cleaning is performed sequentially. 4. The method according to claim 2, wherein at the start of the washing, microorganisms and interfering substances adhered and retained inside the piping of each part are removed by a water hammer phenomenon caused by suddenly stopping the water sampling pump. Cleaning device for residual chlorine in sewage discharge water. 5. A cleaning agent supply device is connected to a pipe for supplying cleaning water to the sand filtration device, and a cleaning agent is mixed with the cleaning water when cleaning the sand filtration device. Cleaning device for residual chlorine in sewage discharge water.