JPH03183A - Method for removing cod by use of coal ash - Google Patents

Abstract

PURPOSE:To treat waste water contg. COD at a low cost without using an expensive adsorbent, etc., by bringing the waste water into contact with coal ash. CONSTITUTION:The waste water contg. COD discharged from the stack gas desulfurizer of a thermal power plant, for example, is firstly stored in a storage tank 1, then passed successively through a fluorine treating tank 2 and a heavy metal treating tank 3, treated and sent to a COD treating tank 4. Coal ash 7 is charged into the COD treating tank 4 from a coal ash storage place 5 through a coal ash supply passage 6, and the coal ash and the waste water are agitated by supplied air and mixed. After COD is adsorbed on the coal ash, then air supply is stopped to settle the inside of the tank, hence coal ash is deposited, and the supernatant liq. with the pH regulated is discharged. The deposited coal ash is sent to a recovered coal ash storage place 12 via a recovery passage and then disposed. A large amt. of coal ash is generated from a thermal power plant utilizing coal, and the coal ash is advantageously utilized in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for removing COD (chemical oxygen demand) from wastewater containing COD using coal ash.

(Prior Art) COD contained in industrial wastewater, such as wastewater discharged from a flue gas desulfurization device of a thermal power plant, causes water pollution and needs to be removed.

Conventionally, the sulfuric acid thermal decomposition method and the COD adsorbent treatment method have been widely used as methods for removing COD from wastewater. Among these conventional methods, the former sulfuric acid thermal decomposition method involves adding sulfuric acid to the wastewater. This method decomposes COD and converts it into harmless components.The latter COD adsorbent treatment method involves bringing wastewater into contact with a COD adsorbent made of polymer resin, so that COD components are adsorbed onto the adsorbent. was to be removed.

(Problems to be Solved by the Invention) The two conventional methods described above have a problem in that they are expensive because they use sulfuric acid or COD adsorbents. As the amount of wastewater continues to increase, putting pressure on management, finding a way to dispose of it at a low cost has become an issue.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a COD removal method using coal ash that can be treated at low cost.

(Means for Solving the Problems) This invention to achieve the above object is to bring COD-containing wastewater into contact with coal ash so that the coal ash becomes carbonated.
COD using coal ash to capture and remove OD components
This is a removal method.

(Function) When a liquid containing impurities comes into contact with a solid, an adsorption effect occurs in which the impurities in the liquid are captured on the solid surface due to interactions between molecules. This is a conventional adsorbent treatment method, and the coal ash of the present invention plays the role of this adsorbent.

In other words, coal ash consists of many particles, each of which has countless holes on its surface, and the COD in the wastewater is captured on the surface of the coal ash particles and absorbed into the holes, where it is adsorbed and removed. It is something.

(Example) Examples of the present invention will be described in detail below based on the drawings.

Figure 1 is a schematic diagram showing the flow of a wastewater treatment system. For example, wastewater containing COD discharged from a flue gas desulfurization equipment at a thermal power plant is first stored in a storage tank (1), and then pumped to a fluorine treatment tank (2). , the CO according to the present invention is sequentially sent to the heavy metal treatment tank (3) and subjected to fluorine treatment and heavy metal treatment.
It is sent to D treatment tank (4).

Coal ash (7) is put into this COD treatment tank (4) from the coal ash storage area (5) via a coal ash supply path (6), and air is also sent in from the air supply path (8) to remove waste water. Stir and mix with coal ash to bring the wastewater into sufficient contact with the coal ash.

When the coal ash (7) is magnified with a microscope, there are many holes and unevenness on the surface of the coal ash particles (7a) as shown in Figure 3, and the deep holes (7b) are similar to the enlarged cross-sectional view in Figure 4. The COD component (9) in the wastewater is adsorbed to the holes and irregularities in the state shown in Figure 4, and then the air supply is stopped. The inside of the COD treatment tank (4) is calmed down to settle the coal ash (5), and the supernatant liquid is sent to the next pH adjustment tank 0■ by a pump, and after adjusting the pH, it is discharged.

The coal ash (7), which has adsorbed the COD component (9) and settled, is collected via the coal ash recovery route (11) to the recovered coal ash storage area 02), and loaded onto a ship or truck.
It is transported to a coal ash disposal site or an industrial waste disposal site.

Coal ash (7) is supplied from the coal ash supply path (6) to replenish the insufficient coal ash during the next COD treatment or COD treatment.

03) is the sludge collection road, where the sludge that has settled in the fluorine treatment tank (2) and heavy metal treatment tank (3) is collected, stored in the sludge storage tank 04), dehydrated by the dehydrator 05), and loaded onto trucks for industrial use. Transported to waste disposal site.

FIG. 2 is a longitudinal cross-sectional view of a C○D treatment container, which is another embodiment of the present invention, used in place of the COD treatment tank (4) of the wastewater treatment equipment shown in FIG. is a metal with a rubber lining (20a) on its inner surface, and is a closed type, with a strainer (21) installed near the lower end of the interior to block the space, and this strainer (21) does not allow coal ash (7) to pass through. A filter medium made of plastic through which only water can pass is supported by a strainer support plate (21a) having many holes.

A drainage inlet (22) is provided at the upper end of this container body 02 [D, and a drainage outlet (23) is provided at the lower end, and a coal ash supply channel (6) is provided at the upper side of the container at a position close to the upper side of the strainer (21). A coal ash recovery path 03) is connected to the internal strainer (21), and coal ash (7) is packed into the upper part of the internal strainer (21), occupying most of the internal space up to the vicinity of the coal ash supply path (6). ing.

In this state, when fluorine-treated and heavy metal-treated wastewater flows in from the wastewater inlet (22), it penetrates into the coal ash (7) and flows down, removing the COD components (9) in the wastewater as shown in Figure 4. The coal ash particles (7a) are adsorbed to the water, and the purified wastewater flows out from the wastewater outlet (23), resulting in the pH shown in Figure 1 below.
It is sent to processing tank 00).

During this COD treatment, the coal ash recovery path (
Coal ash (7) that has adsorbed the COD component (9) is recovered from the IQ, and new coal ash (7) is supplied from the coal ash supply path (6).

Next, we will show the results of a COD reduction test using coal ash conducted at the Chugoku Electric Power Co., Inc.'s Shimonoseki Power Plant.

Test 1 Table 1 shows the results of a test using the COD treatment tank (4) shown in FIG. 1 at a mixing ratio of coal ash and wastewater of 1=3 to 3:1.

According to Appendix Table 1, it was found that coal ash (7) efficiently adsorbed COD in wastewater. and coal ash (7
) and wastewater, the larger the amount of coal ash, the higher the COD reduction effect, but the difference is small, and from a practical standpoint, 1:1 is judged to be appropriate.

Try! S! 2 Using the COD treatment tank (4) shown in Figure 1, we conducted a test of COD reduction by type of wastewater over time, using a mixture ratio of coal ash and wastewater of 1:1. The results are shown in Appendix 2. show.

According to Appendix Table 2, it was confirmed that coal ash has a COD reduction effect even if the type of wastewater changes. It was confirmed that the COD component was significantly reduced in one day with oral changes, and that the reduction effect reached saturation in about five days.

(Effect of the invention) COD using coal ash according to this invention as explained above
According to the removal method, by using coal ash, which is disposed of as waste, in place of conventional COD adsorbents, the cost of COD adsorbents becomes zero, especially in thermal power plants that use coal. Since coal ash is generated, it must be disposed of, and even if it is used as a COD adsorbent and then disposed of, the disposal cost remains the same, and therefore COD treatment can be carried out at low cost and advantageous.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention in a flowchart;
Figure 2 is a vertical cross section of a COD removal container which is another embodiment to replace the COD treatment tank in Figure 1, Figure 3 is an enlarged view of coal ash viewed under a microscope, and Figure 4 is a view of coal ash particles in drainage water. CO of
FIG. 3 is an enlarged cross-sectional view showing a state in which D is adsorbed. 4. COD treatment tank 7. Coal ash 7a. Coal ash particles 9. COD component 20. COD removal container Fig. 2

Claims (1)

[Claims] A COD removal method using coal ash, which comprises bringing COD-containing wastewater into contact with coal ash.