JPH02157089A - Treatment of oil-containing waste water - Google Patents

Abstract

PURPOSE:To allow the water quality of raw water to automatically reach objective water quality while conserving a chemical agent by measuring the oil concn. and flow rate of raw water and injecting a flocculant corresponding to the product of the measured values to perform the flocculating separation of an oil component and measuring the concn. of the oil component remaining in treated water to correct the injection amount of the flocculant. CONSTITUTION:Raw water is sent to a CCl4 extracted substance measuring device 8 by a raw water sampling pump 7 to measure the concn. of a CCl4 extracted substance. At the same time, a flow rate is measured by a raw water flowmeter 3 and the multiplication of the above mentioned concn. and flow rate is performed by an operator 9. A flocculant is injected in waste water whose pH is controlled by a pH control tank 4 in the injection amount operated by the operator 9 from a flocculant storage tank 12 through a flocculant injection pump 13 in the pH control tank 4 to form the flocs of the oil component. Treated water floating under pressure is sampled by a treated water sampling pump 17 to be analyzed by the CCl4 extracted substance measuring device 8 and the analyzed value is compared with an objective value to correct the injection amount of the flocculant. By this method, the optimum injection of a chemical agent is certainly and automatically realized without generating wastefulness at all.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for treating oil-containing wastewater generated in the steel industry, petrochemical industry, automobile industry, and the like.

``Conventional technology'' In the steel industry, petrochemical industry, automobile industry, etc., wastewater containing oil is generated. For example, in the steel production process, alkaline waste water is generated, but in the cold rolling process, there is a process (cleaning process) to degrease and wash the rolling oil that has adhered to the plate surface during the tandem process and clean the surface. In this process, an alkaline agent is used, and this wastewater contains a large amount of oil, so it cannot be discharged untreated.

In order to treat this wastewater, a pressure flotation treatment method is generally used. This method uses acidic chemicals to adjust Pl+ to the Pl+ area (generally circles I5 to 8) where flocculants and coagulant aids are highly effective, then adds a flocculant to coarsen the flocs, and then uses micro air. It is floated under pressure.

The amount of flocculant and flocculation aid mentioned above was determined by the operator himself while measuring the water quality on site.
This type of treatment technology has various drawbacks, such as the efficiency of water quality measurement to determine the input amount and the amount of chemicals to be injected based on this, so as a proposal for rational injection of chemicals without waste, JP-A-62-204811, JP-A-60-
No. 7991 and Japanese Patent Application Laid-open No. 62232540, and
Improvements in oil content measurement, which is one of water quality measurements, are proposed in Japanese Patent Publication No. 13539/1983.

Furthermore, recently, so-called image processing methods have been proposed.

This method constantly measures the density of flocs using image processing to find floc shapes with good sedimentation properties, while achieving stable treated water quality with the minimum amount of flocculant input.

``Problems to be Solved by the Invention'' However, the above-mentioned proposals actually have the following drawbacks.

For example, in the above-mentioned Japanese Patent Application Laid-Open No. 62-204811, the quality of raw water to be treated changes from moment to moment, and manual water quality measurement is dependent on (1) basically Unmanned wastewater treatment facilities are impossible.

(2) Manual water quality measurement takes time, and if processing is performed based on measurement results taken at long intervals, it becomes necessary to add more coagulant and auxiliary agents than originally required. Ru.

In addition, if more than the required amount is added, the shape of the flocs will deteriorate, making it impossible to treat by pressurized flotation and making it impossible to achieve the target value of treated water.

There are other difficulties.

Also, this Japanese Patent Application Publication No. 62-204811, Japanese Patent Application Publication No. 60-7
No. 991 and JP-A-62-232540 both state that it is sufficient to determine the amount of chemicals to be added by analyzing the raw water, but in reality, the quality of the raw water is constantly changing and it is difficult to determine the amount to be added. Since it does not have a fine adjustment function, it has the disadvantage that it is inevitably set at a safe value and that it is unavoidable to dispense the required amount.

It should be noted that some of the input amount determining mechanisms described above are too complicated, and like the equipment used in the image processing method described above, the equipment cost is too high.

In view of the above-mentioned circumstances, the present invention provides a treatment result that uses the integrated value of the amount of chemical input calculated from raw water in the pressure flotation treatment of oil-containing wastewater without requiring any expensive equipment. The aim is to automatically correct the situation accordingly and provide treatment methods that can reliably save on chemicals.

"Means for Solving the Problems" In order to achieve the above object, in the treatment method of the present invention, the oil concentration and flow rate of raw water are measured, and a predetermined amount of input corresponding to the product of these measured values is determined. A flocculant is added to coagulate and separate the oil content, the oil concentration remaining in the treated water is measured, and this is compared with a preset target value for the oil concentration in the treated water to correct the above-mentioned input amount. .

The oil concentration may be measured by carbon tetrachloride extraction-infrared absorption method, hydrophobic solvent extraction-evaporation distillation method.

"Operation" According to the treatment method configured as described above, a predetermined amount of chemicals are added to raw water based on the predetermined relationship between oil content and flocculant and the results of raw water sampling. Measurements are taken to determine whether the wastewater has reached a predetermined target value, and fine adjustments are made to the amount of chemicals added to the raw water.

As a result, it is possible to automatically reach the target water quality while using fewer chemicals.

"Example" An example will be explained with reference to the drawings. In FIG. It is transferred to the pH adjustment tank 4. In the PIljJl tank 4, the wastewater is primarily treated to 5 to 8 Pl+ by injecting an acidic agent into the acid storage tank 10 via an acid injection pump 11 while measuring a total of 16 Pl+. This Pl+ adjustment is a prerequisite for increasing the efficiency of the flocculant.

Here, the input amounts of the flocculant and flocculant aid for removing oil from the wastewater are determined by the following method.

First, the raw water is collected by Cc14 using the raw water sampling pump 7.
Water is sent to the extractable substance measuring device 8, and the CcZ4 extractable substance concentration is measured.

In addition, the above Ccl, extraction measurement was carried out in the above-mentioned Special Publication 1984
It is not necessary to rely on continuous measurement as in No. 539, and intermittent measurement may be used.

This is because it is necessary to install a raw water tank 1 in wastewater treatment equipment (as a buffer in case of equipment trouble), but the buffering function of this raw water tank 1 allows the oil concentration of the raw water to decrease for a short time (
This is because there is no significant change in the amount of Cd4 (about 30 minutes), and if continuous measurement is performed, a large amount of Cd4 is required.
This is because Cl2 cannot be released untreated and is also expensive.

At the same time as the above Cd4 extraction measurement process, the raw water flowmeter 3
The flow rate is measured, and the arithmetic unit 9 multiplies the concentration and the flow rate. This value serves as the reference value for adding flocculant and auxiliary agent. The calculator 9 uses this reference value and
The amount of flocculant to be added is calculated from a predetermined relational expression between oil content and flocculant.

In the PH adjustment tank 4, the amount of flocculant calculated by the calculator 9 is injected into the wastewater whose pH has been adjusted in the Pl + adjustment tank 4 from the flocculant storage tank 12 via the flocculant injection pump 13, and oil content is removed. flocs are formed.

This secondary treated wastewater is fed into the flocculating tank 5, where the flocculant in the amount accumulated by the calculator 9 is added from the flocculant storage tank 14 via the flocculant injection pump 15. The oil flocs become coarser.

The calculation of the amount of flocculant input above is based on the oil concentration of the treated water of 1 m
g/i, coo 8 to 1 (bng/E) as the target value.

That is, as shown in FIG. 2, the Cc of raw water! A proportional relationship was found between the concentration of 4 extracted substances and the amount of flocculant input required to reach the above target value.

The diagonal relationship is as follows.

y=o,], 8χ+25.7 where y: Concentration of Cl74 extracted material in raw water
).

The wastewater containing coarsened oil flocs is sent to the pressure flotation tank 6, the flocs are removed by pressure flotation, and the wastewater is discharged.

The flocculant input amount calculated from the above relational expression is not fixed, but is constantly optimized.

That is, the pressurized and floated treated water is sampled by the treated water sampling pump 17, analyzed by the Cl74 extractable substance meter 8, and compared with a target value to correct the input amount. As a method of correction, for example, the calculated input amount is further increased by a coefficient. If the treated water is below the target value, for example 0
．． It is decreased by 1, and if it exceeds the processing target value, it is decreased to 0.
It goes up one by one. As a result, optimal drug injection without any waste can be automatically realized.

"Effects of the Invention" Since the present invention is configured as described above, it produces the effects described below.

(1) Each piece of equipment required is simple and inexpensive, and the cost required for implementation is low.

(2) Since unmanned means can be used to measure each part, unmanned operation is possible.

(3) Since the amount of drug input is optimized, drug costs are reduced.

[Brief explanation of the drawing]

Figure 1 is a flow diagram showing the method of the present invention, Figure 2 is raw water Cd
4 is an example of a correlation diagram between extract (oil content) and flocculant (PAC). 1... Raw water tank, 2... Raw water pump, 3... Raw water flow meter, 4... PH adjustment tank, 5... Coagulation tank,
6... Pressurized flotation tank, 7... Raw water sampling pump, 8... Ccf4 extractable substance measuring device, 9.
... Computing unit, 10... Acid storage tank, 11... Acid injection pump, 12... Coagulant storage tank, 13... Coagulant injection pump, 14... Coagulation aid storage tank, 15... Coagulation aid injection pump, 16... PI meter, 17... Treated water sampling pump.

Claims (1)

[Claims] (1) Measure the oil concentration and flow rate of raw water, add a predetermined amount of flocculant corresponding to the product of these measured values to coagulate and separate the oil, and measure the oil concentration remaining in the treated water. A method for treating oil-containing wastewater, characterized in that the input amount is corrected by comparing this with a preset target value for oil concentration in treated water.