JPS5910312A - Method for controlling sludge charging to sludge thickener - Google Patents

Abstract

PURPOSE:To maintain a specified concn. of charged sludge and settling speed of the sludge and to eliminate the need for measuring sludge distribution by detecting the flow rates and concns. of initially settled sludge and excess sludge, and controlling the rate of diluting water. CONSTITUTION:Sewage is released through a settling basin 14, an aeration tank 15, a final settling basin 16, and an effluent conduit 17. The initially settled sludge settled in the basin 14 and the excess sludge settled in the final settling basin are removed with removable pumps 18, 21, and are fed to a thickener 1. The treated water removed with a feed pump 25 from the conduit 17 is fed as diluting water into the thickener 1. The values detected with flowmeters 19, 22, concn. meters 20, 23 are inputted to a calculator 11, and a calculator 12, which calculate the set value Qw of the flow of the treating water to be fed. The flow of the treating water to be fed is controlled with a controller 13 in accordance with said value.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for controlling sludge input into a sludge thickening tank for maintaining the concentration of sludge drawn into the sludge thickening tank at a predetermined value in a sewage treatment plant 62. It is related to

[Technical background of the invention and its problems]

In sludge thickening tanks at sewage treatment plants, it is necessary to draw out thickened sludge at an appropriate concentration.

For this reason, conventionally, the sludge concentration distribution in the sludge thickening tank is measured to determine the amount of sludge to be extracted and the amount of sludge to be extracted.

An example of a method for measuring sludge concentration distribution is shown in Figure 1-1.

In FIG. 1, the sludge concentration level meter 4 is suspended from the upper part of the sludge thickening tank 1 with a lobe, and is immersed in the sludge to measure its concentration.

In this case, the inside of the thickening tank L is the sludge scraper 2 and the scum scraper @
3 is still rotating, so when lifting the lobe @ 5, it is necessary to raise and lower the level meter 4 in synchronization with the rotation of the raking machine 2.3, which is not only troublesome to operate, but also However, the measurement accuracy was also insufficient.

In FIG. 1, numeral 6 is an IJ mitswitch for position detection, 7 is a rope pulling controller, and 8 is a sludge drawing pump.

[Object of the Invention] The present invention controls the placement and concentration of sludge input into a sludge thickening tank according to the required drawing concentration, and the sludge input method in a sludge thickening tank eliminates the need for a troublesome sludge concentration level meter. The purpose is to provide a control method.

[Summary of the invention]

The present invention detects the respective flow rates and concentrations of initial settling sludge and surplus sludge introduced into a sludge thickening tank, and calculates the required dilution cover setting value from the above detected values and a preset target sludge concentration of input sludge. Then, treated water with a flow rate corresponding to the upper dilution flow rate setting value is added to the above-mentioned initial settled sludge and excess sludge and put into the sludge thickening tank. This is a method for controlling sludge input into a sludge thickening tank that allows for extraction.

[Embodiments of the invention]

An embodiment of the invention is shown in FIG. 1-.

Fig. 2 4 = The sewage is first collected in a sedimentation tank 14, an aeration tank 15,
The water is discharged through a final settling pond 16 and an outflow culvert 17.

Initial settling sludge settled in the initial settling tank 14 and final settling tank 1
The precipitated surplus sludge is drawn out by drawing pumps 18 and 21, respectively, and sent to the thickening tank 1 (3).

Further, the treated water drawn out from the discharge stream @17 by the injection pump 25 is injected into the concentration tank 1 as dilution water.

In this case, the flow rate Q of the initial settling sludge detected by the flow meter 19 and the concentration meter 20, the IlI degree C1, and the flow rate meter 22 and
The concentration C2 of the sludge concentration detected by the sludge concentration meter 23 is calculated manually using the following equation (1).

The flow M Qt and the concentration C of the mixed sludge are calculated by calculating the equation (2).

Qy = Q, 10Q2 ・・・・・・・・・・・・
...(1) The above calculation result Qy+Cy is further processed by the calculation unit 1.
Target diluted sludge concentration a input into 2 and injected into the thickening tank
For ll2, the set value Q of the amount of water to be injected and processed from the outlet drain
w is calculated using equation (3) below.

When the injection treatment water amount set value Qw is calculated, the controller 13 operates in accordance with this, and the injection treatment water amount is controlled by Qw(4)6.

Further 1: If necessary, the target diluted sludge concentration, C11, and the actual concentration C8 of the water injected into the thickening tank detected by the concentration meter 27.
It is also possible to compare and correct the amount of water to be injected Qw according to the difference.

Next, a method for setting the target diluted sludge concentration C8 will be described.

Figure 3 shows the relationship between sludge concentration and sedimentation rate in a thickening tank.Curve A shows how the sludge interface of sewage with a height Ho1 and a uniform concentration co settles with time t. , the slope of the tangent at time t, l2 indicates the sedimentation velocity v1 at that time.

Further, curve B shows the sedimentation state when the concentration is lower than co, and curve p shows the sedimentation state when the concentration is higher than co.

, and Fig. 4 shows the temporal change in concentration C obtained from Fig. 3, and curves A and B are respectively curves A + in Fig. 3.
B t=corresponds, and the general port relationship is established.

As can be seen from Figures 3 and 4, the lower the concentration, the faster the sedimentation rate and the clear sludge interface.

However, since 62 requires dilution water to achieve a low concentration, an economical dilution concentration is determined experimentally and this is set as the target diluted sludge concentration C.

When the configuration shown in Fig. 92 is used, the concentration of sludge introduced into the sludge thickening tank is adjusted to an appropriate value corresponding to the required sedimentation rate, and the sludge rapidly settles to form a clear sludge interface.

Therefore, the distribution of sludge concentration in the thickening tank can be directly calculated as 1=
This eliminates the need for measurement, and therefore it is possible to omit a sludge concentration level meter that is troublesome to handle.

〔Effect of the invention〕

According to the present invention described above, when initially settling sludge and excess sludge are introduced into the sludge thickening tank of a sewage treatment plant, a portion of the treated water is additionally introduced as dilution water at the same time. :
L is to maintain the concentration of sludge input into the thickening tank at a low concentration within a certain range, equalize the sedimentation rate of the sludge, and make the sludge interface clear. A rational method for controlling sludge input into a sludge thickening tank that eliminates the need for complicated sludge distribution measurements can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the arrangement of a conventional sludge concentration level meter, #IcQ is a system diagram showing an example of the sludge injection control &l]') i method of the sludge thickening tank according to the present invention, and Fig. 3 Figure 4 shows the height of the thickening tank towards the sludge boundary and the height of the sludge boundary 1, respectively.
FIG. 3 is a diagram showing temporal changes in height L and sludge concentration. l...Sludge thickening tank 8...Sludge extraction pump 11.12...Calculator 13...Controller 14...First settling tank 16...Final settling tank 17. ... Outlet culvert 18.21, 24.25 ... Pump 19.22,
26.29・・・・・・Welfare total 20.23.27.30
...Concentration meter (8733) Agent Patent attorney
Yoshiaki Inomata (and 1 other person) Figure 1 (7) Figure 2 Figure 3 Figure 4 Time

Claims (1)

[Claims] Detect the flow rate and concentration of the initial settling sludge and surplus sludge introduced into the sludge thickening tank, calculate the required dilution water volume setting value from the above detected value and the preset target sludge concentration of the input sludge, and Dilution water position setting value I: A sludge injection control method for a sludge thickening tank, characterized in that treated water of a corresponding flow rate is added to the above-mentioned initial settling sludge and surplus sludge and then fed into the sludge thickening tank.