JPH0474076B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention removes trace amounts of contaminated water, such as secondary treated sewage water, industrial wastewater, and water source water with advanced organic contamination, by using activated carbon to which organisms are attached. Organic matter, odor components, ammonia nitrogen (NH ₄ −N)
This paper relates to a water treatment method for biodegrading substances such as substances under aerobic conditions. [Prior Art] In the field of water supply, water sources are becoming increasingly contaminated, and organic pollution is becoming particularly significant. In response to this water source pollution, research and development are being carried out on purification technologies different from conventional ones. One of these is the biological activated carbon treatment technology. This treatment method involves passing contaminated water containing dissolved oxygen through an activated carbon layer. The pollutants in the contaminated water are adsorbed onto the activated carbon, and biological decomposition and other biological effects occur. Because activated carbon has a negative removal effect, more pollutants are removed than the amount that activated carbon can theoretically adsorb. [Kurosawa et al. “Water pollution research”
Vol. 11, No. 9, pp. 590-598 (1988)]. Here, the pollutants adsorbed by the activated carbon are removed by the biological removal action, and this biological removal action is called a biological regeneration action because it appears as if the adsorption capacity of the activated carbon is restored. Activated carbon is expensive, and without a bioregenerative effect, this would be just an adsorbent and would require frequent replacement.
Not economical. Therefore, replacement frequency is low.
Biological activated carbon treatment methods that are expected to have biological regeneration effects are expected to continue to develop in the future. [Problem to be solved by the invention] However, the conventional biological activated carbon treatment method
The only thing that can be said is that ``when an activated carbon adsorption tower was installed, a biological activated carbon effect was observed by chance,'' and from the perspective of biological regeneration, it is difficult to say that sufficient effects have been brought out. The present invention aims to maximize the biological regeneration effect of activated carbon in a water treatment method for purifying contaminated water in an aerobic state using activated carbon to which living organisms are attached. [Means for Solving the Problems] The present invention provides a water treatment method for purifying contaminated water in an aerobic state using activated carbon to which living organisms are attached. The above-mentioned problem has been fundamentally solved by a water treatment method characterized in that the water is passed through a layer of activated carbon in this order, and then a layer of activated carbon with a particle density of 0.6 g/cc to 1.0 g/cc. Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows one embodiment of the present invention, in which contaminated water 1 such as secondary treated sewage water is collected in a treatment tank 2.
Enter from the top. Activated carbon (A) 3 and activated carbon in treatment tank 2
(B) 4 is packed in a fixed bed, and a layer of activated carbon (A) 3 is formed in the upper part of the treatment tank 2, and a layer of activated carbon (B) 4 is formed in the lower part of the treatment tank 2. The most important thing in this invention is to reduce the particle density of contaminated water.
A layer of activated carbon A having a particle density of 0.3 g/cc or more and less than 0.6 g/cc is passed through in this order, and a layer of activated carbon B having a particle density of 0.6 g/cc or more and 1.0 g/cc or less. Conventionally, regarding the treatment effects of biological activated carbon, attention has been focused on its micropores (pores), especially the amount of pores with a radius of several angstroms. This is because the size of the pollutant components dissolved in water is approximately several Å, so activated carbon, which has many micropores with a pore diameter of several Å, has a large adsorption capacity for these pollutants. This is based on the idea that biological regeneration effects will be enhanced. However,
Regarding the adsorption effect of activated carbon, there are not only molecular sieving effects related to the size of the adsorbed substance, but also hydrophilicity, hydrophobicity, and potential issues, so it is not possible to discuss only the size of the adsorbed substance, but it depends on various factors. Generally, only the size of the adsorbed substance is considered because it has the greatest influence on the adsorption effect. However, the inventors believed that the biological regeneration effect is largely related not only to the adsorption capacity of activated carbon itself, but also to the amount of microorganisms retained, and through experiments, they found that the amount of microorganisms retained depends on the particle density of activated carbon. I understood. That is, when activated carbon has a low particle density, it holds a large amount of microorganisms, but when it has a high particle density, it holds a small amount of microorganisms. This is because activated carbon with a low particle density is generally 10 μm (10 ⁵ Å)
This seems to be because the ratio of macropores on the order of several micrometers is high, and bacteria on the order of several μm can easily breed there. Furthermore, activated carbon with a low particle density has a high ratio of macropores, which has the disadvantage that the number of micropores on the order of the number + Å that can adsorb pollutants is slightly reduced. No major improvement can be expected,
In some cases, on the contrary, the bioregenerative effect may be reduced. Therefore, we investigated the relationship between the activated carbon's pore radius, pore volume, and other properties of activated carbon with different particle densities, and the relationship between these and biological regeneration effects. The relationship with volume etc. is the first example.
It was as shown in the table.

[Effect]

The particle density used in the present invention is 0.3 g/cc or more 0.6
Activated carbon (A) with less than g/cc has a high ratio of macropores of 1 μm or more and a high ratio of macropores on the order of 10 μm, so bacteria with a size on the order of several μm can easily breed, so it does not have sufficient biological effects. It will be done.
In addition, activated carbon (B) with a high particle density of 0.6 g/cc to 1.0 g/cc has a low ratio of macropores of 1 μm or more and a slightly high ratio of micropores of several + Å, so it adsorbs a large amount of pollutant components. . Then, the contaminated water is treated with activated carbon A and activated carbon B.
Although it is not clear why the biological regeneration effect increases significantly when these are passed in this order, it is assumed that the following is probably the reason. As mentioned above, a large amount of bacteria adheres to activated carbon A, but since the bacterial group includes bacteria that decompose pollutants that are adsorbed substances, they secrete degrading enzymes, and some of the enzymes are absorbed into activated carbon A. However, it is thought that some of it reaches the activated carbon B together with the contaminated water and compensates for the lack of bacteria in the activated carbon B. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited to this example. Example 1 Secondary treated sewage water was treated according to the present invention as water to be treated. In addition, as a comparative example, the same water to be treated was treated using another treatment method. The experimental apparatus used a column with a diameter of 160 mm and a height of 5500 mm. Table 2 shows the specifications of the activated carbon used in the experiment, and Table 3 shows the experimental conditions. As shown in Table 3, Comparative Example 1 is a case where activated carbon A alone is used, Comparative Example 2 is a case where activated carbon B is used alone, and Comparative Example 3 is a case where activated carbon B and activated carbon A are filled in that order. It is.

【table】

[Table] When the TOC removal rate of 30% is considered as breakthrough, the usable period of activated carbon until replacement and the amount of sludge generated were calculated. The results are shown in Table 4.

[Table] Treated water SS does not change much from the beginning of operation, but treated water TOC gradually increases as days pass. In the present invention, treated water with the best quality was obtained compared to Comparative Examples 1, 2, and 3. On the other hand, in the present invention, the usable period of activated carbon before replacement is approximately 1.5 to 2 times longer than in the comparative example.
In addition, the amount of sludge generated is for activated carbon A alone (Comparative Example 1)
This is almost the same as in the case of , and even if the activated carbon A having a low particle density is not used in its entirety, almost the same effect as when the entire amount is used can be expected. Example 2 In place of activated carbon A and activated carbon B in Example 1, a test was conducted under the same experimental conditions as in Example 1 (Table 3), except that the particle densities of both activated carbons were close to each other. Activated carbon A (upper layer side) with a particle density of 0.58 g/cc and activated carbon B (lower layer side) with a particle density of 0.65 g/cc were used. Table 5 shows the specifications of these activated carbons. Table 6 shows the treatment effects when using these activated carbons.

【table】

〔Effect of the invention〕

The present invention combines activated carbon with a low particle density and activated carbon with a high particle density in series.
The biological regeneration effect increases, and as a result, the frequency of backwashing of activated carbon is reduced compared to conventional methods, and the period of use before replacing activated carbon can be extended to about 1.5 times compared to conventional methods. The available period has been significantly extended. Furthermore, the amount of sludge generated can be made almost the same as when activated carbon with a low particle density is used alone. Furthermore, by installing an aeration pipe at the bottom of the activated carbon packed bed, the entire packed bed can be maintained in an aerobic state, making it effective even for contaminated water with high oxygen demand, such as secondary treated sewage water. can be processed. At this time, when the water to be treated is passed in a downward flow, a gas-liquid countercurrent effect is exhibited, so the amount of air supplied can be saved, resulting in energy savings. In addition, if the water to be treated is passed in a downward flow and the particle size of the activated carbon with a low particle density in the upper layer is made larger than the particle size of the activated carbon with a high particle density, the activated carbon will Since clogging can be prevented, pretreatment such as coagulation and sedimentation equipment can be omitted.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of an apparatus for carrying out one embodiment of the invention. Explanation of symbols: 1... Contaminated water, 2... Treatment tank, 3... Activated carbon A, 4... Activated carbon B, 5... Diffusion pipe, 6... Oxygen-containing gas, 7... Treated water pipe, 8... Treated water.

Claims (1)

[Claims] 1. In a water treatment method that purifies contaminated water in an aerobic state using activated carbon with attached living organisms, contaminated water is treated with a layer of activated carbon with a particle density of 0.3 g/cc or more and less than 0.6 g/cc, or a layer of activated carbon with a particle density of 0.6 g/cc or more. A water treatment method characterized by passing through layers of activated carbon in order of 1.0 g/cc or less.