JPS61494A - Operational control of purification tank - Google Patents

Abstract

PURPOSE:To conserve power consumption by adjusting an air diffusion amount corresponding to the inflow amount of sewage to a purification tank, by performing intermittent operation in a predetermined duty ratio before the inflow of sewage or after a predetermined time is elapsed from the stoppage of the inflow of sewage. CONSTITUTION:The blower 13 for supplying air to an aeration tank 3 is continuously operated for a time permitting the inflow of sewage to the aeration tank 3 or before a predetermined time T3 is elapsed from the stoppage of the inflow of said sewage and intermittently operated in a predetermined duty ratio T2/(T1+T2) prior ot the inflow of sewage or after the predetermined time was elapsed. During a time when no sewage is flowed into the aeration tank 3, the aeration blower 13 is operated in the duty ratio of T2/(T1+T2) and, therefore, power consumption can be conserved by a time T1/(T1+T2). During this time, the concn. of dissolved oxygen in the aeration tank 3 is reciprocated in a concn. range necessary for maintaining bacteria.

Description

DETAILED DESCRIPTION OF THE INVENTION m-Industrial Application Field-1 This invention relates to a method for controlling the operation of an aerated septic tank. Since septic tanks are designed based on the expected maximum sewage inflow, most septic tanks are operated with sewage inflows below their treatment capacity. In particular, when there are few residents in a housing complex or during school holidays, the amount of sewage inflow is much lower than the designed value. However, even in such cases, the septic tank's aeration phase blower always continues to send air in an amount commensurate with its maximum processing capacity, and this blower consumes more than 60 to 70 percent of the septic tank's electricity. ing.

The aeration phase blower supplies the oxygen necessary to cultivate the microorganisms in the aeration tank, but the dissolved oxygen concentration required to maintain the microorganisms must be above ippm. It is said to be good. Furthermore, microorganisms consume a lot of oxygen when they are active, and their oxygen consumption is low at other times.

The active period is when the pollutants contained in the wastewater are decomposed, and it coincides with the time when the wastewater flows into the aeration tank. Therefore, the fact that the blower is constantly operating means that more oxygen than necessary is being supplied when no sewage is flowing in. When more oxygen than necessary is supplied to the aeration tank, the dissolved oxygen concentration in the aeration tank becomes high and becomes saturated. When we actually investigate septic tanks, we find that most have dissolved oxygen concentrations close to the saturated value. If the dissolved oxygen concentration is high, it is not only a waste of electricity, but also the P)l of the aeration tank decreases due to the action of nitrifying bacteria, which may lead to deterioration of the quality of treated water.

m-Prior Art--In order to prevent deterioration of water quality due to a decrease in pH in an aeration tank or to save energy including the same, several operation control methods have been employed in the past. The first method is to provide an air relief valve between the blower and the diffuser pipe to adjust the amount of diffused air. The second method is to periodically turn on and off the blower using a timer. The third method is to attach a dissolved oxygen meter to the aeration tank and turn the blower on and off based on the measured value, or to control the rotational speed of the motor for driving the blower.

-Problems to be Solved by the Invention- However, among these conventional methods, the first method described above is completely ineffective in terms of energy conservation, and furthermore, the amount of air diffused in the aeration tank is reduced. There is a risk that water quality will deteriorate due to insufficient convection of wastewater. The second method has no problem if the amount of sewage flowing in is constant, but if the amount of sewage flowing in fluctuates, it will follow this (
The problem is that it cannot be done. In addition, the third method is functionally complete, but the dissolved oxygen meter is expensive and difficult to handle, so it is difficult to install it in a septic tank without a resident manager, and it is difficult to control the rotational speed of the motor. If this is done, there is a risk that the water quality will deteriorate due to a decrease in the amount of air diffused.

In view of the problems of the conventional methods as described above, this invention was made with the aim of obtaining a more rational operation control method, in which the amount of aeration is adjusted according to the amount of wastewater flowing into the septic tank. The present invention aims to provide a method for controlling the operation of an aerated septic tank, which does not consume unnecessary power, and also allows a simple configuration of the control device.

m-Means for solving the problems--1 The means employed in the present invention to solve the above problems will be explained using the reference numerals of the illustrated embodiments. The method includes continuously operating a blower 13 that supplies air to the aeration tank 3 while sewage is flowing into the aeration tank 3 and until a predetermined time T3 has elapsed after the inflow has stopped; Before the inflow of wastewater and after the predetermined time has passed, a predetermined duty ratio T2/(TI+7
2) is for intermittent operation. The above time interval T1,
T2. T3 is determined by measuring the dissolved oxygen concentration in the aeration tank while actually operating the septic tank, and TI is determined by measuring the dissolved oxygen concentration in the aeration tank at the lowest point in the tank after stopping the aeration in the aeration tank. T2 for an appropriate time during which the value does not fall below ippm.
T is the time from when the blower is restarted after the above 11 hours have elapsed until the dissolved oxygen concentration in the aeration tank returns to its original value.
3 is the time required for the dissolved oxygen concentration in the aeration tank to return to its original value by continuing to operate the blower after the inflow of sewage has ended. When sewage flows into a septic tank, microbial activity becomes active and the dissolved oxygen concentration in the aeration tank decreases. Note that the original value of the dissolved oxygen concentration here is the value below the upper limit of the dissolved oxygen concentration required for the aeration tank to operate normally, and in practice it is normally maintained while continuously aerating. It can be determined by measuring the dissolved oxygen concentration in an aeration tank that is being operated.

1-Operation--While sewage is not flowing into the aeration tank 3, the aeration phase blower 13 is operated at a duty ratio of T2/(T1+72), so TI/(Tit-72) You can save electricity consumption by an amount of time. During this time, the dissolved oxygen concentration in the aeration tank will fluctuate within the concentration range necessary to maintain microorganisms. Further, if sewage flows in, the blower is operated during the inflow and for 13 hours after the inflow stops, thereby supplying the amount of oxygen necessary to purify the inflowing sewage.

11 Embodiment 11 FIGS. 1 and 2 show examples of septic tanks in which the method of the present invention is adopted. In FIG. 1, 1 is an inflow pump tank, 2
is a sedimentation separation tank, 3 is an aeration tank, 4 is a sedimentation tank, 5 is a drainage pump tank, 6 is a wastewater inflow pipe, 7 is a level switch,
8 is a transfer pump, 9 is an aeration pipe provided in the aeration tank 3, 10 is an air lift pump for returning sludge, 11 is a level switch for the drainage pump tank 5, 12 is a drainage pump for discharge, 13 is an aeration pipe 9 and a blower 114 that supplies air to the air lift pump 10; a solenoid valve that opens and closes an air flow path to the air lift pump 10; and 15, a control device.

When wastewater flows in from the inflow vibro, this is detected by the level switch 7, and the pump 8 is activated to send the wastewater to the sedimentation separation tank 2. As a result, the water in each tank is sequentially swept away to the downstream tank and flows into the drain pump tank 5. When the water level in the drain pump tank 5 rises, the level switch 11
When this is detected, the drain pump 12 is started.
It is released into the river. By operating the advection pump 8, the inflow pump tank 1
When the water level decreases, the pump 8 stops, and the flow of wastewater to each area is stopped. Air is supplied into the aeration tank 3 through an aeration pipe 9, and organic matter in the sewage is decomposed by aerobic microorganisms (activated sludge) in the tank. Activated sludge that has separated from the contact material in the aeration tank 3 and flowed into the settling tank 4 is settled in the settling tank 4, and is transferred to the settling tank 21 by the air lift pump 10, which is operated from time to time.・111°
°11"060 uses the head to collect wastewater into sedimentation separation tank 2.
There are also some that do not have a transfer pump 8 so that the water flows down.

The one shown in Fig. 2 is provided with a flow rate adjustment tank 16 in place of the inflow pump tank 1 and the sedimentation separation tank 2 shown in Fig. 1.
As far as the operation control method of the present invention is concerned, there is no difference in its function and operation.

FIG. 3 shows an example of a sequence circuit for carrying out the method of the present invention in such a purifying apparatus. In the figure, Xl
to X4 are relays, Xl is a relay for driving the transfer pump 8, and x4 is a relay for driving the blower 13.

TI to T3 are timers, and the respective set times are the above-mentioned time intervals T1 to T3. LS is a contact point of the level switch 7, and SV is a contact point of a relay for the solenoid valve 14.

The relay X4 for driving the blower 13 is the relay X2, x3
Or, when the solenoid valve SV is energized, it is energized and the blower 1 is energized.
3 is driven. Part A in the circuit is operated by the blower when sewage flows into the aeration tank 3 and for 13 hours after the inflow stops.
13, when sewage flows into the septic tank and the liquid level in the inflow pump tank 1 rises, the level switch LS is turned on, the relay X1 is energized, and the transfer pump 8 is driven. At the same time, the contact 17 is turned on, and the relay x2 is energized and self-held by the contact 18. Inflow pump tank 1
When the liquid level decreases, the level switch LS is turned off, the transfer pump 8 is stopped, the contact 19 is turned on, and the timer T3 starts timing operation. When time T3 elapses after the transfer pump 8 stops, the contact 20 turns off and the blower 13 stops.

When the relays x2 are not energized, the blower 13 is operated intermittently by the B portion of the circuit. That is, when T1 time elapses after the blower 13 stops, the contact 21
is turned on, relay X3 is excited, self-held at contact 22, and contact 23 is turned off to reset timer TI. The blower 13 is operated by excitation of the relay x3, and after a period of time T2 has elapsed, the contact 24 is turned off to stop the blower 13, and the contact 23 is turned on and the timer T1 starts timing operation. By repeating the above operations, the blower 13 has a duty ratio T2/(
It is operated intermittently at TI + T2).

FIG. 4 shows the above operation in a time chart. Note that since it is necessary to operate the air lift pump 10 when returning the sludge, the blower 13 is operated regardless of the above operation.

In addition, in a purification apparatus that does not have the transfer pump 8 described above, the operation of the drainage pump 12 may be detected and controlled instead of the operation of the transfer pump 8. Although there is a time delay of about 5 to 10 minutes from the time the wastewater flows into the purification device until the drainage pump 12 is started, there is no practical problem.

Next, Tl, T2. A specific example of the setting value of T3 and its effect will be described. The processing capacity is 14 with the tank configuration shown in Figure 2.
5n (/day, the original value of dissolved oxygen concentration in the aeration tank is 7.9
When measurements were taken in the septic tank at ppm, the dissolved oxygen concentration was 6.5 ppm due to the inflow of sewage into the aeration tank. ippm and returned to the original value 30 minutes later, and when aeration was stopped when there was no inflow of wastewater, the dissolved oxygen concentration decreased to 4.3 ppm after 1 hour, 3.4 ppm after 2 hours, and Data was obtained that the concentration returned to the original value 30 minutes after operating the vapor phase blower from a state of 3.5 ppm. Considering the fact that the measurement point is not necessarily the point with the lowest dissolved oxygen concentration, and in consideration of safety, T1 was set to 60 minutes and T2 and T3 were set to 30 minutes based on the above data. The discharge water quality of this septic tank before adopting the method of the present invention was B
OD is 14.9ppm, SS is 6.0ppm, PH is 7
°0 (average value of two measurements). On the other hand, after adopting the method of the present invention with the above time settings, the quality of the discharged water is as follows: BOD is 5.5 ppm, SS is 5゜lppm, P
H was 7.0 (average value of three measurements), and it was recognized that the quality of the effluent water was clearly improved. Additionally, the amount of electricity used by the purifier was reduced by approximately 60 percent.

11 Effect 1 - A As understood from the above explanation, in method 1 of the present invention, the aeration phase blower is operated intermittently when sewage does not flow into the septic tank, and when sewage flows into the septic tank, the aeration phase blower is operated intermittently. Since the blower is operated according to the amount of waste water, the blower is not operated unnecessarily even though there is no inflow of sewage, which is extremely economical. Furthermore, since the blower is operated intermittently, there is no problem of convection in the aeration tank due to insufficient aeration, and the control device can be simplified. moreover,
Since the dissolved oxygen concentration in the aeration tank does not become excessively high, the quality of the discharged water is also improved.

[Brief explanation of the drawing]

1 and 2 are diagrams schematically showing a purifying apparatus, FIG. 3 is a diagram showing an example of a sequence control circuit for implementing the method of the present invention, and FIG. 4 is a timing chart thereof. In the figure, 1 is an inflow pump tank, 3 is an aeration tank, 6 is a sewage inflow pipe, 7 is a health inch, 8 is a transfer pump, 9 is an aeration pipe, 11 is a health inch, 12 is a drainage pump, 13
is a blower, 115 is a control device, 16 is a flow rate adjustment tank, T1
is the stop time of the blower during intermittent operation, T2 is the operation time of the blower during intermittent operation, and T3 is the time during which the blower continues to operate after the flow of sewage into the aeration tank has stopped. Patent applicant: Hokkoku Kiseki Kogyo Co., Ltd. Agent: Takao Nishi, patent attorney Figure 1

Claims (1)

[Claims] (1) A blower that supplies air to the aeration tank is operated continuously while sewage is flowing into the aeration tank and until a predetermined period of time has passed after the inflow has stopped, and An operation control method for an aeration-type septic tank, characterized in that after the predetermined period of time has elapsed, intermittent operation is performed at a predetermined duty ratio.