JP3104764B2 - Excess sludge flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling excess sludge flow in a sewage treatment apparatus using an activated sludge method.

[0002]

2. Description of the Related Art A sewage treatment apparatus using an activated sludge method is shown in FIG.
As shown in (1), the inflowing sewage is first flowed into the sedimentation basins 1A, 1B, and 1C to settle and remove settling pollutants, and then the supernatant water is guided to the aeration tanks 2A, 2B, and 2C, and air is supplied from a blower (not shown). While mixing with the activated sludge, the sludge in the supernatant water of the sedimentation basin is first adsorbed to the activated sludge,
Purifies by oxidative degradation by microorganisms. The mixed liquid of the first settling tank supernatant water and the activated sludge is supplied from the aeration tank to the final settling tank 3
A, 3B, and 3C, settle and separate into activated sludge and supernatant water in the final sedimentation basin, and the supernatant water is discharged into public waters after sterilization. The activated sludge settled in the final sedimentation basin is returned to the aeration tank as return sludge by the return sludge pumps 4A, 4B, and 4C, and is recycled. The activated sludge increased by the purifying action is extracted as excess sludge from the returned sludge line by the excess sludge pumps 5A, 5B, 5C and the excess sludge flow control valves 6A, 6B, 6C, and the excess sludge is flowed by the excess sludge flow meters 7A, 7B, 7C. Is charged into the sludge thickening tank 8 while measuring. There are various methods for determining the amount of excess sludge to be withdrawn. In FIG. 2, the ML for measuring the concentration of the suspended liquid mixture (hereinafter referred to as MLSS) in the aeration tank is used.
The signals of the SS meters 9A, 9B, 9C and the MLSS preset in the required excess sludge flow rate calculators 10A, 10B, 10C
A method is shown in which the amount of excess sludge to be extracted is determined from the target concentration of the concentration and is output to the excess sludge flow control devices 11A, 11B, 11C.

[0003]

The sewage treatment apparatus based on the activated sludge method described above usually has a plurality of treatment lines as shown in FIG. 2, and the excess sludge is discharged from the final sedimentation pond of one sewage treatment line. Is connected to the excess sludge pipe line of the other sewage treatment system, and is finally collected into one pipe line and connected to the sludge concentration tank 8. There is a difference between each sewage treatment line, such as the length of the pipe line and the presence or absence of a bent section.If it is necessary to withdraw a large amount of excess sludge, use a sewage treatment line that can sufficiently extract excess sludge. Not occur. As a result, the amount of activated sludge retained by each sewage treatment line varies greatly, and the disadvantage of increasing the complexity of operating the sewage treatment equipment, such as the amount of air blown to the aeration tank and the individual management of the activated sludge residence time in the system, increases. there were. In view of the above, an object of the present invention is to keep the amount of excess sludge withdrawn in a plurality of sewage treatment lines uniform and to realize the simplicity of operation of the sewage treatment device.

[0004]

A sewage treatment apparatus having a plurality of sewage treatment lines by the activated sludge method, wherein excess sludge from each sewage treatment line is collected in one pipe and transferred to a concentration tank. Calculating the required excess sludge flow rate for each sewage treatment system using the MLSS concentration constant control algorithm of the aeration tank, etc., and a surplus sludge flow meter provided in each excess sludge extraction pipe And a control signal for calculating the ratio of the required excess sludge flow rate to the measured flow rate, and a control signal such that the measured flow rate ratio of each sewage treatment system is substantially the same from the output of the measured flow rate calculator. Provided with a measured flow rate regulator and an excess sludge flow control device that adjusts the excess sludge flow according to the output of the measured flow rate regulator, the excess sludge from the final sedimentation basin of each sewage treatment system The ratio of the amount and the required excess sludge flow measured sludge flow rate so as to control to be the same.

[0005]

According to the present invention, the arrival ratio of the amount of excess sludge extracted from a plurality of sewage treatment lines to the required amount can be made substantially the same, so that the states of the plurality of sewage treatment lines can be made uniform and the operation of the sewage treatment device can be simplified. .

[0006]

FIG. 1 shows an embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted. In the figure, 12A, 12B, and 12C are measured flow rate calculators, 13 is a measured flow rate adjuster, 14 is a reference measured flow rate setter that is set in advance to determine the necessity of the flow rate adjustment operation, and 15 is a flow rate An adjustment operation duration monitoring device 16 for monitoring the duration of the adjustment operation is a required excess sludge flow rate monitoring device that determines whether the output of the required excess sludge flow calculation device has become smaller than the previous output. Next, the operation will be described. Measured flow ratio calculators 12A, 12
In B and 12C, the required excess sludge flow rate calculators 10A and 10A
Excess sludge flow meter 7A, 7B for output of B, 10C,
The ratio of the output (actually measured flow rate) of 7C is (1), (2),
The calculation is performed by the equation (3), and the calculated value is output to the measured flow rate ratio adjuster 13. a _A = QM _A / QD _A (1) a _B = QM _B / QD _B (2) a _C = QM _C / QD _C (3) Here, QM _A , QM _B , and QM _C are surplus sludge flow meters 7.
A, 7B, 7C is the output _{of, QD A, QD B, QD} C
A request excess sludge flow calculator 10A, 10B, 10C _{output, a A, a B, a} C is measured flow ratio calculator 12
Outputs from A, 12B, and 12C. The measured flow ratio adjuster 13 includes the measured flow ratio calculators 12A and 12B,
The calculated ratio of 12C is compared with the reference measured flow ratio a _REF preset in the reference measured flow ratio setting device 14, and if all the measured flow ratios a _A , a _B , and a _C are higher than the reference measured flow ratio a _REF. , required excess sludge flow rate QD _A, QD _B, QD
Without modifying _C , the excess sludge flow control device 11A,
Output to 11B and 11C. Next, the reference measured flow rate a
A case where a series of the measured flow rate ratio lower than _REF exists will be described. Now the measured flow rate a _A of the sewage treatment system _A
Is smaller than the reference measured flow ratio a _REF , the required excess sludge flow Q of the sewage treatment systems B and C is
D _B, make modifications for QD _C. Correction is (4),
(5) using, so that the actual flow rate ratio of all the sewage processing sequence is the same as the smallest measured flow ratio a _A, calculates the modification request excess sludge flow QDC. _{QDC B = QM B / a A} (4) QDC C = QM C / a A (5) (4), (5) outputs a correction request excess sludge flow rate calculated by the equation excess sludge flow controller 11B, and 11C I do. Such Doing corrective action excess sludge amount flowing through pipeline decreases, measured excess sludge flow rate QM _A of do not fix processing sequence A is increased, the greater the measured flow ratio a _A. Largely became a _A (4), by substituting in (5), take corrective action again. In this way, the maximum possible flow rate can be realized while maintaining the uniformity of the excess sludge flow rates of a plurality of systems. The end of the adjusting operation by such a correction of the required excess sludge flow rate is determined by a stop command output after a lapse of a set time from the adjusting operation continuation time monitoring device 15 started at the start of the adjusting operation, or requested when the required excess sludge flow rate decreases. This is performed by a stop command output from the surplus sludge flow monitoring device 16. In the embodiment, the MLSS constant control algorithm is used to calculate the required excess sludge flow rate, but the calculation is performed using the ratio to the inflow sewage flow rate or the number of days (sludge age) in which activated sludge stays in the system as an index. Depending on the method. Although the adjustment of the excess sludge flow rate is performed by the flow rate control valve, the adjustment may be performed by controlling the number of rotations of the excess sludge pump.

[0006]

As described above, according to the present invention, the ratio of the measured excess sludge flow rate to the required excess sludge flow rate of each sewage treatment line becomes the same, and each sewage treatment line can be maintained in substantially the same state. The operation of the sewage treatment apparatus including a plurality of sewage treatment systems can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a surplus sludge flow control device showing an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional excess sludge flow control device.

[Description of sign]

 1A, 1B, 1C First settling tank 2A, 2B, 2C Aeration tank 3A, 3B, 3C Final settling tank 4A, 4B, 4C Return sludge pump 5A, 5B, 5C Excess sludge pump 6A, 6B, 6C Excess sludge flow control valve 7A , 7B, 7C Surplus sludge flow meter 8 Sludge concentration tank 9A, 9B, 9C MLSS meter 10A, 10B, 10C Required surplus sludge flow calculator 11A, 11B, 11C Excess sludge flow controller 12A, 12B, 12C Actual measurement flow ratio calculator 13 Measured flow ratio adjuster 14 Reference measured flow ratio 15 Adjustment operation duration monitoring device 16A, 16B, 16C Required surplus sludge flow monitoring device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-138187 (JP, A) JP-A-60-175597 (JP, A) JP-A-59-109290 (JP, A) JP-A-59-109290 59293 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 3/12

Claims (1)

(57) [Claims] 1. A sewage treatment apparatus comprising a plurality of sewage treatment lines by the activated sludge method, wherein excess sludge from each sewage treatment line is collected in one pipe and transferred to a concentration tank. Required sludge flow calculator for calculating the required excess sludge flow for each sewage treatment system using the MLSS control algorithm, etc., a surplus sludge flow meter provided in each surplus sludge extraction pipe, and a required surplus sludge flow And a measured flow rate calculator that calculates the ratio of the measured flow rate, and an output of each measured flow rate calculator that calculates the measured flow rate ratio of each sewage treatment system so that the measured flow rate ratios are approximately the same. A surplus sludge flow control device that adjusts the surplus sludge flow according to the output of the measured flow rate ratio controller, and measures the surplus sludge flow from the final sedimentation basin of each sewage treatment system with the required surplus sludge flow An excess sludge flow control device, wherein the sludge flow ratio is controlled to be the same.