JP2648241B2 - PH control method in purification treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying water to be treated such as sewage or the like, in which the pH value is controlled.
H control method.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, in the treatment of water to be treated such as sewage, water to be treated is supplied from a water supply pipe 1 to a mixing tank 2 and agitated by a stirrer 3. While performing the treatment, the inorganic water (FeCl 3)
₃ , sulphate, etc.) are added to aggregate the particles contained in the water to be treated. Then, the pH value of the mixed solution 6 is measured by the pH sensor 5 immersed in the mixing tank 2, and based on the measured value, the flow rate of the pump 9 interposed in the pH adjusting agent supply pipe 8 is controlled by the control device 7. The pH was controlled so that the pH value of the water to be treated was 4 to 7 by adjusting the alkaline agent supplied from the pH adjusting agent supply pipe 8. Further, the coagulated sludge flowing from the mixing tank 2 to the pump tank 10 is subjected to solid-liquid separation by the membrane separation device 11, and the solid sludge is separated from the pump tank.
10 and the excess sludge was discharged through the sludge extraction pipe 12.

[0003]

However, according to the conventional configuration described above, there is a problem that the electrode surface of the pH sensor 5 has reduced sensitivity due to adhesion of sludge or the like, and an error occurs in pH control. Further, there is a problem that a vicious cycle occurs in which sludge that easily adheres is formed, and sludge with poor filterability is formed, which negates filtration efficiency in a membrane separation device in a subsequent process.

[0004] It is an object of the present invention to provide a pH control method in a purification treatment capable of always performing accurate pH control while preventing a decrease in sensitivity of a pH sensor due to sludge in water to be treated.

[0005]

In order to solve the above-mentioned problems, a pH control method in a purification treatment according to the present invention comprises the steps of: charging water to be treated, a coagulant, and a pH adjuster into a mixing tank; In a purification process in which a liquid is separated into a solid and a liquid by a membrane separation device, the pH value of the treated water subjected to membrane separation is measured by a pH sensor arranged in a permeate flow path of the membrane separation device, and based on the measured pH value. It is configured to control the amount of the pH adjuster added to the mixing tank.

[0006]

In the above construction, by measuring the pH value of the permeate containing no suspended solids separated by membrane by the membrane separator, the sensitivity of the pH sensor is not degraded due to the adhesion of sludge, and an accurate value is always obtained. Measured and accurate pH
By adding a regulator, sludge having good filterability is formed, and the filtration efficiency in the membrane separation device is improved.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a mixing tank 21 is provided with a treated water supply pipe 22 for supplying treated water such as sewage, an inorganic coagulant (FeCl 2).
_3. A coagulant supply pipe 23 for supplying a pH adjuster and a pH adjuster supply pipe 24 for supplying a pH adjuster are open.
A first pump 25, a second pump 26, and a third pump 27 are interposed in 22, 23 and 24, respectively.

The mixing tank 21 communicates with a membrane separation device 29 having an ultrafiltration membrane or a microfiltration membrane via a pressure pump 28. The concentrated sludge side of the membrane separation device 29 communicates with the mixing tank 21. The permeate side communicates with the permeate flow path 30.
Further, a pH sensor 31 is disposed in the permeated liquid of the permeated liquid flow path 30, and a control device 32 connected to one end of the pH sensor 31 is connected to the third pump 27 via a signal line. ing. Further, a sludge extraction pipe 33 is provided in communication with the mixing tank 21, and a suction pump 34 is provided in the middle of the sludge extraction pipe 33.
Is interposed. The mixing tank 21 is provided with a stirrer 35.

The operation of the above configuration will be described below. The mixing tank 21 is supplied with water to be treated supplied by the first pump 25 through the water supply pipe 22, coagulant supplied by the second pump 26 through the coagulant supply pipe 23,
The pH adjusting agent supplied through the pH adjusting agent supply pipe 24 by the pump 27 is supplied. Further, the mixed liquid 36 in the mixing tank 21 stirred by the stirrer 35 is pumped to the membrane separation device 29 by the pressure feed pump 28, and is separated into solid and liquid in the membrane separation device 29.

[0010] The concentrated sludge containing solids separated by the membrane is returned to the mixing tank 21, and the permeated liquid permeating the membrane is taken out through the permeated liquid channel 30 as treated water. Further, the pH value of the treated water is measured by the pH sensor 31 in the permeate flow path 30, and the control device 32
By controlling the flow rate of the third pump 27, the addition amount of the pH adjuster is adjusted.

At this time, since the pH sensor 31 is provided in a permeated liquid containing no floating contaminants, ie, treated water, which has been subjected to membrane separation by the membrane separation device 29, the sensitivity of the pH sensor 31 is deteriorated due to adhesion of sludge. Instead, accurate measurement is always performed, and sludge having good filterability is formed by adding an accurate pH adjuster, thereby improving the filtration efficiency in the membrane separation device 29. The filtration membrane used in the membrane separation device 29 may be either a tubular type or a flat type.

FIG. 2 shows another embodiment of the present invention, in which members having the same functions as those in the previous embodiment are assigned the same reference numerals and description thereof is omitted. In FIG. 2, the mixing tank
The partition 21 is divided into a plurality of sections by a partition wall 41, and a stirrer 35 is disposed in a first section, and a membrane separation device 29 is immersed in each of the subsequent sections.

In such a configuration, the same operation and effect as those of the first embodiment can be obtained.

[0014]

As described above, according to the present invention, by measuring the pH value of the permeate containing no suspended solids which has been subjected to membrane separation by a membrane separation apparatus, the pH value due to the adhesion of sludge is measured.
To prevent the deterioration of the sensitivity of the H sensor and always perform accurate measurement, and to improve the filtration efficiency in the membrane separation device by forming sludge with good filterability by adding an accurate pH adjuster. Can be. In addition, by membrane separation, control can be performed with a pH value substantially the same as the pH value of the mixing tank, and no time delay occurs.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a purification treatment facility showing one embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a purification treatment facility showing another embodiment of the present invention.

FIG. 3 is an overall configuration diagram of a conventional purification treatment facility.

[Explanation of symbols]

 21 Mixing tank 24 Coagulant supply pipe 27 Third pump 29 Membrane separator 31 pH sensor 32 Controller

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C02F 1/66 510 C02F 1/66 510K 530 530L 540 540D 9/00 502 9/00 502E 502P 503 503C 504 504C 11/12 11/12 C 11/14 11/14 B

Claims (1)

(57) [Claims] In a purification treatment in which water to be treated, a coagulant, and a pH adjuster are charged into a mixing tank, and the mixed liquid in the mixing tank is separated into a solid and a liquid by a membrane separation device, the permeated liquid flow path of the membrane separation device is used. Of treated water membrane-separated by a pH sensor located at
A pH control method in a purification treatment, comprising measuring an H value and controlling an amount of a pH adjuster to be added to a mixing tank based on the measured pH value.