JP2515255B2 - Automatic adjustment device for sludge concentration in sewage treatment tank - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a method and an apparatus for automatically adjusting sludge concentration in a sewage treatment tank.

[Background of the Invention]

In order to keep the treatment efficiency high in activated sludge treatment, a certain amount of microorganisms working on the inflow raw water to be treated is required. Conventionally, in continuous treatment such as the activated sludge method, a preliminary storage tank, etc. is provided to keep the inflow load into the treatment tank constant, and the sludge concentration is regularly measured to keep the sludge concentration constant. A certain amount of sludge is discharged as excess sludge out of the system. This includes JIS
MLSS using the dry weight method for suspended substances specified in
Alternatively, measure the MLVSS or measure the concentration of the treatment tank liquid using a photoelectric densitometer, and if the concentration is high, reduce the amount of sludge returned from the sedimentation tank, and change the sludge volume ratio discharged as excess sludge. Increase it.

However, in the activated sludge method for the purpose of denitrification, the sludge must be carefully extracted in order to keep the nitrifying bacteria in the treatment tank or the nitrification tank. Especially in the intermittent aeration automatic operation method (Patent No. 1160241) in which the sludge settling speed is used as an index of aeration and non-aeration, it is an essential requirement to keep the sludge concentration within a certain range.

[Object of the Invention]

An object of the present invention is to constantly maintain a constant sludge microorganism in a treatment tank liquid, reduce the amount of excess sludge, and automatically adjust the sludge concentration suitable for intermittent aeration conditions.

[Structure of Invention]

In the automatic sludge concentration adjusting device in the sewage treatment tank according to the present invention, the sewage treatment tank that circulates the treated water by aeration or agitation, and the sludge concentration that also performs aeration in addition to the precipitation action. A sludge transfer path having an adjusting tank and being led out from the lower part in the wastewater treatment tank and having its leading end portion introduced into the sludge concentration adjusting tank, and being led out from the lower part in the sludge concentration adjusting tank, A separate pump is attached to each of the sludge reduction channels with the discharge tip opening into the wastewater treatment tank, or a common pump is attached so that the flow path is switched by an electric valve, and the sludge concentration is increased. Provided in the upper part of the adjustment tank is a supernatant overflow channel for overflowing the supernatant water into the wastewater treatment tank when the water level in the sludge concentration adjustment tank rises, and a transmission type optical sensor is provided in the wastewater treatment tank. Then, by the optical sensor, sewage treatment tank If the sludge concentration in the wastewater treatment tank is determined to be higher than the predetermined concentration, the sludge transfer path will function by the pump, and if the sludge concentration in the wastewater treatment tank is determined to be lower than the predetermined concentration, the above sludge The function of the transfer path is stopped, and the sludge reduction path is electrically connected by the pump so that the function can be performed.

〔Example〕

In the drawings of the embodiments, 1 is a sewage treatment tank, 1a is a device for aeration or stirring in the sewage treatment tank 1, 2 is a settling tank type sludge concentration adjusting tank, and 2a is aeration in the sludge concentration adjusting tank 2. 3 is a sludge transfer path for transferring high-concentration sludge from the lower part of the sludge treatment tank 1 into the sludge concentration adjusting tank 2, and 4 is a sludge treating tank for sludge in the sludge concentration adjusting tank 1. 1
The sludge return path for returning to the inside is provided with separate pumps P as shown in FIG. 1 or with a common pump P as shown in FIG. The flow path is switched by the above. Reference numeral 6 denotes a supernatant overflow channel that is led out from the upper part in the sludge concentration adjusting tank 2 and has its outlet opening end opened into the wastewater treatment tank 1. It has a role of overflowing into the sewage treatment tank 1. Reference numeral 7 denotes a discharge path led out from a lower part of the sludge concentration adjusting tank 2, and a pump P discharges excess sludge. Reference numeral 8 denotes a transmissive optical sensor installed in the sewage treatment tank 1. When the optical sensor 8 determines that the sludge concentration in the sewage treatment tank 1 is higher than a predetermined concentration, a pump P is used. The sludge transfer mechanism 3 works,
Further, when the sludge concentration in the sewage treatment tank 1 is determined to be lower than a predetermined concentration, the sludge reducing passage 4 is electrically connected by the pump P so as to function. 9
Is a tap water supply valve that opens when the water level in the sludge concentration adjusting tank 2 drops, and 10 is set to a level slightly lower than the constant water level in the sludge concentration adjusting tank 5. These are water level detectors, and after these settled sludge is returned from the lower part of the sludge concentration adjusting tank 2 into the sewage treatment tank 1, the water level in the sludge concentration adjusting tank 2 is restored to a constant water level for the next adjustment. This is to prepare for the action.

After performing intermittent aeration in the sewage treatment tank 1, the sludge is precipitated and the supernatant water is discharged, and when the intermittent aeration process is performed again, the concentration is adjusted at a predetermined low water level l _0. The agitation device 1a circulates the liquid in the tank to make it a uniform state, and the sludge concentration is detected by the transmission type optical sensor 8 set in the wastewater treatment tank 1, and the concentration is higher than a predetermined value. If it is higher, the sludge transfer passage 3 functions by driving the pump P so that all or part of the circulating liquid flows into the sludge concentration adjusting tank 5. At that time, the sludge concentration adjusting tank 2 is set to perform intermittent or continuous aeration in synchronization with the wastewater treatment tank 1 except for the concentration adjusting time, and stop the aeration during the concentration adjusting time. As a result, the sludge concentration adjusting tank 2 is in a state of static sedimentation for about 1 to 3 hours, and during the sludge adjusting time, sludge particles in the sludge mixed solution transferred to the sludge treatment tank 1 are sludge. It precipitates in the lower part of the concentration adjusting tank 2, and the supernatant water overflows and flows back into the wastewater treatment tank 1 through the supernatant water overflow channel 6.

In this way, while the supernatant water from which sludge has been removed is recirculated, when high-concentration sludge is continuously transferred from the lower part of the wastewater treatment tank 1 into the sludge concentration adjusting tank 2, The sludge concentration gradually decreases and is diluted until it reaches a predetermined concentration detected by the transmissive optical sensor 8.

Further, when the amount of sludge in the sewage treatment tank 1 decreases, the pump P of the sludge reduction passage 4 is activated by the detection signal of the transmission type optical sensor 8 and settles down in the sludge concentration adjusting tank 2. The concentrated sludge is returned to the sewage treatment tank 1, and the transmission type optical sensor 8 continues until the sludge concentration in the sewage treatment tank 1 reaches a predetermined value.

When the water level in the sludge concentration adjusting tank 2 decreases due to the continuous transfer of the sludge, the tap water supply valve 9 is opened by the detection signal of the water level detector 10 to supply water up to the constant water level. To prepare for the adjustment action.

〔The invention's effect〕

According to the present invention, when the growth rate of sludge microorganisms in the sewage treatment tank is large, the sludge is drawn out and stored in the sludge concentration adjusting tank, and when the concentration decreases due to self-digestion, the sewage is discharged from the sludge concentration adjusting tank. By replenishing the sludge to the treatment tank, the sludge concentration in the wastewater treatment tank can be adjusted, and there is an advantage that a certain amount of sludge microorganisms can be always retained in the liquid in the wastewater treatment tank.

In addition, in the sludge concentration adjustment tank, the amount of sludge is reduced by performing intermittent aeration without adding a substrate that is a nutrient source for microorganisms in addition to the extraction sludge, reducing the amount of excess sludge and intermittent aeration conditions. The activation of adapted sludge microorganisms is embodied. Thereby, microorganisms most suitable for replenishment into the sewage treatment tank can be obtained, and methane gas or the like can be generated by anaerobic fermentation to prevent the concentrated sludge from expanding and floating.

The method and apparatus of the present invention are not only required for automatic intermittent aeration control, but also play a large role in, for example, small-scale wastewater treatment tanks and recreational facility wastewater treatment tanks with large fluctuations in inflow load. The method is useful for all biological suspension treatment methods such as the oxidation method, oxidation date method, and oxidation pond method, and can contribute to automation, unmanned operation, and energy saving of equipment. It is.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the device of the present invention. FIG. 1 shows an example in which separate pumps are attached to the sludge transfer passage and the sludge return passage, and FIG. 2 shows sludge transfer. An example is shown in which a common pump is attached to the path and the sludge reduction path, and the flow path is switched by an electric valve. 1 ... sewage treatment tank, 2 ... sludge concentration adjusting tank, 3 ... sludge transfer path, 4 ... sludge reduction path, 5 ... electric valve, 6 ...
Clear water overflow channel, 8 ... Transmission type optical sensor, P ... Pump.

Claims (2)

(57) [Claims] 1. A sewage treatment tank (1) having a sewage treatment tank (1) for circulating treated water by aeration or agitation and a sludge concentration adjusting tank (2) for causing precipitation. Sludge transfer path (3) that is led out from the lower part of the sludge and has its leading end introduced into the sludge concentration adjusting tank (2), and the leading end that is led out from the lower part in the sludge concentration adjusting tank (2) A separate pump (P) is attached to each of the sludge reducing passages (4) whose parts are opened into the sewage treatment tank (1), or the flow paths are switched by an electric valve (5). And a common pump (P) is attached to the upper part of the sludge concentration adjusting tank (2), and when the water level in the sludge concentration adjusting tank (2) rises, the supernatant water overflows into the wastewater treatment tank (1). A clear water overflow channel (6) is provided, and a transmission type optical sensor (8) is installed in the wastewater treatment tank (1). The light sensor (8), sewage treatment tank (1) in by connexion sludge transfer path to the pump (P) when the sludge concentration is determined to a higher concentration than the predetermined concentration (3)
Function, and when the sludge concentration in the wastewater treatment tank (1) is determined to be lower than a predetermined concentration, the function of the sludge transfer path (3) is stopped and the sludge is pumped by the pump (P). An automatic adjustment device for sludge concentration in a sewage treatment tank, which is electrically connected so that the reduction path (4) can function. 2. A sewage treatment tank (1) having a sewage treatment tank (1) for circulating treated water by aeration or agitation and a sludge concentration adjusting tank (2) for performing aeration and precipitation. ), And a sludge transfer path (3) that is led out from the lower part of the inside of the above) and has its leading end portion introduced into the sludge concentration adjusting tank (2),
Separate pumps (P) are attached to the sludge reduction passage (4) that is led out from the lower part of the sludge concentration adjusting tank (2) and has its leading end opened into the wastewater treatment tank (1). Or a common pump (P) is attached so that the flow path is switched by the electric valve (5), and the sludge concentration adjusting tank (2) is provided above the sludge concentration adjusting tank (2). A clear water overflow channel (6) for overflowing the clear water into the sewage treatment tank (1) when the water level rises is provided, and a transmission type optical sensor (8) is provided in the sewage treatment tank (1). When the optical sensor (8) determines that the sludge concentration in the wastewater treatment tank (1) is higher than a predetermined concentration, the pump (P) causes the sludge transfer path (3) to function, and When it is determined that the sludge concentration in the wastewater treatment tank (1) is lower than a predetermined concentration, the sludge transfer path (3) is used. There becomes electrically connected to I connexion sludge reduction path to the pump (P) (4) can function to stop, automatic adjuster of the sludge concentration in the sewage treatment tank.