JPH05345186A - Method for automatic control of ph in oil-containing waste water treatment - Google Patents

Abstract

PURPOSE:To keep a sensor part under a good condition for a long time and to attempt to perform stable pH adjustment by a method wherein a part of an oil-contg. waste water and an oil-contg. floating substance is removed without changing pH of a liq. to be measured by means of a pretreatment apparatus to obtain a liq. to be measured with less sensor staining substance and this liq. is measured by means of a pH meter, etc. CONSTITUTION:In a method for controlling pH of a waste liq. contg. an oil- contg. floating substance, a part of an oil-contg. waste water is taken out and the oil-contg. floating substance is removed without changing pH of a liq. to be measured by means of a pretreatment apparatus 2 such as a wholly automatic pressurizing-type cleaning and filtering machine or a press-floatation separating apparatus to obtain a liq. to be measured with less sensor-staining substance. pH of this liq. is measured by a conventional pH meter 4 or a pH meter with an automatic cleaning device. As the result, it becomes possible to perform automatic control of pH of an oil-contg. waste water treating apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically controlling pH in oil-containing wastewater treatment equipment.

[0002]

2. Description of the Related Art Generally, for pH control in wastewater treatment, a glass electrode type sensor is directly immersed in a liquid to be measured to detect pH, and an acid or alkali solution is injected by an electric signal through a pH indicator controller. This is done by controlling the automatic valve or pump that operates.

In this method, since the sensor is directly immersed in the liquid to be measured, when oily suspended matter having high viscosity such as oily wastewater is present, this suspended matter adheres to the sensor, and as a result, However, there is a problem that the sensitivity of the sensor is lowered or cannot be detected, and the pH control is disturbed or disabled. To deal with this, Akira Kai
Like 62-14364, sensor cleaning with chemical solution, brush cleaning,
Sensor cleaning technologies such as ultrasonic cleaning and sensors with cleaning devices have been developed, but they all have the problem that they do not last long and are time-consuming.

[0004]

It is impossible to completely remove the oil-containing pollutants adhering to the sensor by cleaning the sensor by any of the conventional methods. Therefore, the sensitivity of the sensor is reduced in a short time. Decrease, pH measurement becomes impossible, p
Since it is not possible to control H automatically, wash the sensor by hand frequently (1/8 / 8Hr) and adjust the pH.
There was a problem that the function of the control had to be maintained.

The present invention solves the above problems and provides a stable and automatic pH control method for oil-containing wastewater treatment.

[0006]

According to the present invention, in order to solve the above-mentioned problems, if the oil-containing suspended matter is removed, the contamination of the pH sensor is extremely reduced. 2. Removal of oil-containing suspended solids hardly changes the pH of wastewater. Based on the findings of the above, a part of the oil-containing wastewater is extracted, and the oil-containing suspended solids are removed without changing the pH of the liquid to be measured by a pretreatment device such as a fully automatic pressure filter or a pressure floating separation device. Obtaining a solution to be measured with a small amount of sensor pollutants and measuring the pH of this solution with a conventional pH meter or a pH meter equipped with an automatic cleaning device keeps the sensor in good condition for a long period of time and provides stable pH control. Is made possible.

That is, according to the present invention, in a method for controlling pH of a waste liquid containing oil-containing suspended solids, a part of the liquid to be measured is extracted to remove electrode contaminants in the liquid by a pretreatment device, and then this treatment is performed. It is an automatic pH control method in the treatment of oil-containing wastewater, which is characterized by measuring the pH of water and adjusting the pH of the entire waste liquid using this measured value. FIG. 1 shows a specific configuration of the present invention.

Reference numeral 1 is a pump for supplying a liquid to be measured. 2 is a pretreatment device for removing oil-containing suspended solids in the liquid to be measured supplied by a pump, 3 is a measuring tank for receiving the liquid from which the oil-containing suspended solids have been removed by the pretreatment device, and measuring the pH, Reference numeral 4 is a pH sensor, 5 is a pH indicator controller, 6 and 7 are control valves for supplying a liquid for neutralization, which are controlled by an electric signal from 5.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
The solution to be measured is sent from the reaction tank 8 to the pretreatment device 2 at a rate of 300 l / min by the pump 1 having a capacity of 1.5 kw. A pressure floating separation device is used as the pretreatment device 2. Here, the oil-containing suspended solids in the liquid to be measured are removed, and the liquid is allowed to flow into the measuring tank 3 that receives the liquid for measuring the pH in a natural flow. The pH is detected by the pH sensor 4 equipped with the ultrasonic cleaning device installed in the measuring tank 3, and the control signals 6 and 7 for supplying alkali or acid are opened / closed by the electric signal of the pH indicator controller 5 so that the inside of the reaction tank The pH of the liquid is automatically controlled to a value (pH 6 to 8) suitable for the agglutination reaction.

The properties of the oil-containing wastewater treated in this manner are as follows: pH: 5.5-10.0 n-Hexane extract: 500-2,200 mg / l The properties were: pH: 5.0 to 9.5, n-hexane extract: 10 to 30 mg / l ☆ Grayish black oil-containing suspended solids: none.

As a result, in this oil-containing wastewater treatment equipment, the sensitivity of the pH sensor was reduced little, and it was possible to maintain stable pH control for a long period of 12 months. FIG. 2 is a graph showing the pH transition of the coagulation tank according to this example, and FIG. 3 is a graph showing the pH transition of the coagulation tank according to the conventional method. As can be seen from these figures, according to the present invention, the pH of the liquid is automatically and well controlled.

[0012]

EFFECTS OF THE INVENTION According to the present invention, it is possible to remarkably reduce the contamination of the pH sensor, and as a result, even if the conventional pH sensor is used, the oil-containing wastewater is not deteriorated without lowering the sensitivity of the pH sensor. The pH of the processing equipment can be automatically controlled, and the maintenance cost of the sensor can be significantly reduced.

Although the present invention has a drawback that the facility cost is slightly high, it can greatly reduce the maintenance cost and the risk of environmental pollution due to deterioration of water quality of wastewater due to incomplete pH control.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an oil-containing wastewater treatment facility according to an embodiment of the present invention.

FIG. 2 is a graph showing the pH transition of the coagulation tank according to this example.

FIG. 3 is a graph showing changes in pH of a flocculation tank according to a conventional method.

[Explanation of symbols]

 1 Supply pump for solution to be measured 2 Pretreatment device 3 pH measuring tank 4 pH sensor 5 pH indicator controller 6 Alkali supply control valve 7 Acid supply control valve. 8 reaction bowl.

Claims (1)

[Claims] 1. A method for controlling the pH of a waste liquid containing oil-containing suspended solids, wherein a part of a liquid to be measured is extracted to remove electrode contaminants in the liquid by a pretreatment device, and then the pH of the treated water is adjusted. Measure and use this measurement to determine the pH of all waste liquid
PH in oily wastewater treatment characterized by adjusting
Automatic control method.