JPS5811085A - Automatic controller for floating and concentrating tank - Google Patents

Abstract

PURPOSE:To maintain the tickness of a floating concd. sludge layer in an optimum range by providing a thickness detector for the floating concd. sludge layer, a comparator for the output thereof and the preset upper and lower limit values of the thickness of the concd. sludge layer, and a controller for a concd. sludge scraper. CONSTITUTION:The thickness of a floating concd. sludge layer 3 is detected by a floating concd. sludge layer detector 10 provided in a floating tank 2. The upper and lower limit values of the layer 3 by which predetermined concn. of sludge and clarity of separated liquid are obtained are deforehand inputted to a comparator 11, which compares the upper and lower limit values and the output from the detector 10. A controller 12 emits and instruction for starting the operation of a sludge scraper 4 when the thickness of the layer 3 is equal to the upper limit value or larger than the same. At the point of the time when the thickness of the layer 3 decreases equal to or smaller than the lower limit value, the controller emits an instruction for stopping the scraper 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control device for flotation and concentration of sewage sludge, and more particularly to an automatic control device for maintaining the thickness of a flotation and thickening sludge layer within a certain range.

Conventionally, the gravity concentration method has often been adopted as a method for concentrating sewage sewage sludge. This method has the advantages of relatively low operating costs and relatively easy maintenance. However, since the driving force for enrichment is gravity, the fundamental (
=The drawback was that it was not possible to expect such a concentration effect. % (=In recent years, as the amount of organic matter contained in sewage sludge has increased, its concentration has deteriorated, and there are cases where the gravity concentration method cannot achieve the desired concentration rate.

Furthermore, because sludge often changes in quality depending on the season, the gravity concentration method has the disadvantage that stable treatment is difficult.

Since the gravitational concentration method has the above-mentioned drawbacks, in recent years flotation methods, which can provide stable processing, have been increasingly adopted.

The principle of the levitation method is as follows. Treated water after sludge separation (
A part of the separated water) is taken out as circulating water, and 4 to 5 KP/
After dissolving the air under the pressure of d, it is combined with the raw sludge water. At this time, the circulating water is released to the atmosphere and a large amount of fine bubbles are generated. These microbubbles adhere to the sludge and provide buoyancy, causing the sludge to float and become concentrated.

The purpose of concentration processes such as the gravity method and flotation method is, of course, to obtain highly concentrated sludge and clear separated water, and in this round flotation method, the thickness of the flotation thickened sludge layer is appropriately controlled. There is a need to. The thicker the floating thickened sludge layer, the higher the concentration of the thickened sludge. On the other hand, if the thickness of the floating thickened sludge layer is made too thick, the clarity of the separated water will decrease.

Conventionally, the thickness of the floated thickened sludge layer was controlled by the operator's experience and intuition by scraping the floated thickened sludge at an appropriate frequency using a timer (usually the scraping frequency was several times every 7 days or more). (Once at 7:00).

In this conventional method, load fluctuations in raw sludge water, etc.
Therefore, if the thickness of the floating thickened sludge layer becomes too thick, or vice versa, the clarity of the treated water and the concentration of the sludge may not be satisfied.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an automatic control device for a flotation thickening tank that can always obtain highly concentrated sludge and clear separated water.

The feature of the present invention is that in an apparatus for floating and concentrating sludge,
A comparator that compares the upper and lower limits of the thickness of the floated thickened sludge layer located at the top of the flotation tank, and an output from the comparator (-therefore, the thickened sludge scraping device d It consists of a device that instructs the start and stop of operation.

As mentioned above, it is most important to maintain the thickness of the thickened sludge layer within an appropriate range (= floating in the flotation method). The upper and lower limits of the thickness of the thickened sludge layer are set in advance. The sludge scraping device is stopped when the lower limit value is reached, and the sludge scraping device is always kept within the upper and lower limit values.

The figure is a diagram schematically showing an example of the apparatus of the present invention.

Raw sludge flows through pipe 1 and into tank 2.

At the same time, circulating water pressurized by the pressurizing pump 5 and sucking air from the pipe line 6 flows into the flotation tank 2 via the pipe line 8. Flotation tank 2
Since the circulating water is released to the atmosphere, the air dissolved in it is generated as fine bubbles, which adhere to the sludge and float the sludge from the top of the floating thickened sludge layer to the sludge scraping device 4. (Thus, the thickened sludge is scraped off and discharged to the thickened sludge receiving tank 9.

In such a flotation thickening tank, the thickness of the flotation thickened sludge layer 3 is detected by a flotation thickened sludge layer detection device 10 which is installed in the flotation tank 2 and can move up and down. The upper and lower limits of the thickness of the flotation thickened sludge layer 3 that can achieve the predetermined sludge concentration and separation liquid clarity are determined by experiment (=Yoshi), which are predetermined and input υ, and these upper and lower limit values and the flotation thickened sludge The controller 12 receives the output from the comparator 11, and when the thickness of the floated thickened sludge layer 3 is equal to or larger than the upper limit value, C2 is the sludge scraping system. An instruction is given to start operation of the device 4. When the sludge scraping device 4 is operated, the thickness of the floated thickened sludge layer 3 gradually decreases.
When the thickness of the sludge scraper becomes equal to or smaller than the lower limit, an instruction to stop the sludge scraping device 4 is issued.

Here, it is desirable to apply a light transmission method to the floating thickened sludge layer detection device 10, but it is not limited to this method.
The floating thickened sludge layer detection device 10 does not have to be vertically movable as described here, and the light source and light receiver may be installed at preset upper and lower limit positions.

As explained above (2. According to the present invention, the thickness of the floating thickened sludge layer, which is the most important management index, is always kept within the appropriate range (-
Because it can be maintained, highly concentrated sludge and clear separated liquid can always be stably obtained.

[Brief explanation of the drawing]

The drawings are diagrams schematically showing one embodiment of the present invention.

Claims (1)

[Claims] Equipment for flotation and concentration of sludge (2) The upper part of the flotation tank (
2. A device that detects the thickness of the floated thickened sludge layer, a comparator that compares the output from the device with preset upper and lower limits of the thickness of the floated thickened sludge layer, and An automatic control device for a flotation thickening tank, comprising a device that instructs to start and stop operation of a thickened sludge scraping device based on the output of the device.