JPH0768277A - Highly advanced treatment of sewage - Google Patents

Abstract

PURPOSE:To provide highly advanced treatment method of sewage by which not only color, organic substances such as COD, and SS but also NH4-N, pathogenic bacteria, etc., which are difficult to removed by a conventional method, are removed and whose treatment cost is low. CONSTITUTION:After the pH of raw water is adjusted to at 5-7, the water is led to a treatment tank 2 to which an oxidant is added and which is filled with granular manganese dioxide and the resulting oxidized liquid is aerated in an aeration and water treatment tank 3. At the time of the clogging of the treatment tank, the layer of granular manganese dioxide is back-washed. At the time treatment function lowers, following the back-washing, the activated liquid is brought into contact with the layer of the granular manganese dioxide to activate the granular manganese dioxide. Further, as a part of an oxidizing agent, the drawn-out activated waste liquid may be added to raw water.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is used for purification of organic wastewater containing not only chromaticity, COD, NH ₄ -N, SS, but also organisms such as pathogens as secondary treated water of sewage. The present invention relates to advanced sewage treatment methods.

[0002]

2. Description of the Related Art As an advanced treatment method for sewage, a treatment tank 52 filled with granular activated carbon 51 as shown in FIG.
A method is known in which sewage is passed at 100 to 200 m / day and the polluted components in the sewage are adsorbed on the granular activated carbon 51. However, this method can remove chromaticity, COD, SS, etc. well, but the removal rate of pathogenic bacteria is not so good.
There was a drawback that NH ₄ -N could not be removed at all. Further, the granular activated carbon 51 used here is not only expensive, but also has a drawback that the treatment cost is high because it has a short life when used for treating dirty water such as sewage.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and it is difficult to remove the organic matter such as chromaticity and COD and SS by the conventional method while maintaining the processing performance by the conventional method. The purpose of the present invention is to provide an advanced sewage treatment method capable of removing NH ₄ -N, pathogenic bacteria, and the like, which have been previously mentioned, and further significantly reducing the treatment cost as compared with the conventional method.

[0004]

The present invention, which has been made to solve the above problems, adjusts the pH of raw water to 5 to 7 and then passes it through a treatment tank filled with granular manganese dioxide by adding an oxidizing agent. It is characterized in that it is watered and the obtained oxidizing solution is aerated to obtain highly treated water. Incidentally, electrolytic manganese dioxide is used as the granular manganese dioxide, and when the treatment tank is clogged, a method of backwashing the granular manganese dioxide layer in the order of air washing, simultaneous backwashing, and water backwashing can be adopted. Also,
When the treatment performance deteriorates, following the above backwashing, after extracting the total amount of water in the treatment tank, the activation liquid is contacted with the layer of granular manganese dioxide to activate the granular manganese dioxide,
The entire activated waste liquid can be withdrawn. Further, the extracted activation waste liquid can be added to the raw water as a part of the oxidizing agent.

[0005]

According to the present invention, chromaticity in sewage, organic matter such as COD and NH ₄ -N can be removed by the oxidizing action of granular manganese dioxide, and SS can be removed by the filtering action of the granular manganese dioxide layer. It The pathogenic bacteria in the sewage are killed by the bactericidal action of the coexisting oxidizing agent. It should be noted that manganese dioxide changes to MnO 2 when an organic substance or the like is oxidized, but since it returns to manganese dioxide again by the oxidizing agent, the treatment performance does not deteriorate. Therefore, chromaticity, organic matter such as COD, SS, NH ₄ —N, and pathogenic bacteria can be removed without using expensive activated carbon.

[0006]

The present invention will be described in more detail below with reference to the flow sheet of FIG. In FIG. 1, 1 is a pH adjusting tank, 2 is a treatment tank having a granular manganese dioxide layer made of electrolytic manganese dioxide or palladium-impregnated electrolytic manganese dioxide, 3 is an aeration tank and a treatment water tank, 4 is an acid storage tank, and 5 is an oxidizing agent. Storage tank 6 is an activated waste liquid storage tank. Also, 7 is a pump,
8 is a blower, 9 is a pH indicator controller, 10 is a stirrer, and 11 is a level controller. The raw water is stirred with the acid supplied from the acid storage tank 4 in the pH adjusting tank 1 and adjusted to pH 5 to 7.
To remove organic substances such as COD, it is better to have a low pH, but it is preferable to adjust the pH to a higher value from the viewpoint of treated water pH, and the treated water pH should be 5.8 while maintaining a high rate of organic matter removal.
To reduce the pH to ~ 8.6, adjust the pH of the raw water as shown in Fig.2.
Adjust to 5-7.

The raw water whose pH has been adjusted in this way is then added with an oxidizing agent and supplied to the treatment tank 2. In addition to chlorine-based oxidizers such as NaClO, permanganate and hydrogen peroxide can be used as the type of oxidizer to be added, but since ozone oxidizes manganese dioxide to permanganate, granular dioxide is used. The manganese is heavily worn and cannot be used. In addition, since permanganate is mixed with Mn ^{++ in the} oxidizing solution, a separate treatment is required.

The addition rate of the oxidizing agent is preferably 20 to 50% of the required amount of the oxidizing agent which completely decomposes COD. Figure 3 shows an example of using NaClO as the oxidant, but the required amount of oxidant (theoretical value)
The COD removal rate decreases below 20% of CO2, and the COD removal rate does not improve further above 50%, but the residual chlorine (R-Cl) derived from the added oxidant in the treated water increases. However, the oxidizer is wasted.

When the raw water having the pH adjusted to 5 to 7 and the oxidizing agent added thereto is supplied to the treatment tank 2 as described above, the chromaticity in the raw water, organic matter such as COD, etc. are caused by the oxidizing action of the granular manganese dioxide. And NH ₄ —N are decomposed and removed. In addition, SS is removed by the filtering action of the granular manganese dioxide layer, and the pathogenic bacteria are killed by the bactericidal action of the coexisting oxidizing agent.

As the granular manganese dioxide, electrolytic manganese dioxide is usually used. In this case, when the electrolytic manganese dioxide oxidizes and decomposes organic substances, MnO is produced on the surface of the granular manganese dioxide, and the coexisting oxidizing agent causes MnO + NaClO →
It reacts like MnO ₂ + NaCl and returns to manganese dioxide again. If the amount of the coexisting oxidant is smaller than the amount of MnO 2 generated here, a portion where MnO 2 does not return to manganese dioxide is formed, and the treatment performance gradually decreases.

As the granular manganese dioxide, in addition to electrolytic manganese dioxide, palladium-impregnated electrolytic manganese dioxide is used. When palladium-impregnated electrolytic manganese dioxide is used, the added oxidizing agent becomes an active enzyme by the action of electrolytic manganese dioxide along with the reaction by electrolytic manganese dioxide, and after this is adsorbed by palladium, it oxidatively decomposes organic substances and the like in raw water. Since the reaction also occurs at the same time, the effect is further enhanced as shown in FIG. Here, in the case of palladium-impregnated electrolytic manganese dioxide, since the palladium itself only undergoes a treatment commensurate with the amount of the active enzyme adsorbed, there is no deterioration in treatment performance over time, but the electrolytic manganese dioxide portion is accompanied by the treatment as described above. Since MnO 2 is produced as a result, when the amount of coexisting oxidant is smaller than the amount of MnO 2 produced, there is a portion where MnO 2 does not return to manganese dioxide, and the treatment performance gradually declines.

The water flow rate in the treatment tank 2 is preferably LV = 300 m / day or less as shown in FIG. If the water flow rate exceeds this value, the diffusion of pollutants such as COD into granular manganese dioxide will not be accompanied and the treatment performance will decline. The contact time between raw water and granular manganese dioxide should be SV = 6 / hr or less. However, if the SV is too small, the treatment tank 2 will become large and the required amount of granular manganese dioxide will increase, so if these are taken into consideration, SV =
1 / hr to 6 / hr is preferable.

When the treatment is continued in this manner, the water level in the treatment tank 2 gradually rises due to the clogging of the granular manganese dioxide layer, and as described above, the amount of MnO that cannot return to MnO ₂ increases. Then the processing capacity will decrease. First, when the granular manganese dioxide layer is clogged, the granular manganese dioxide layer is backwashed in the order of air washing → simultaneous backwashing → water backwashing. Backwash speed is usually 0.5 to 1.5 m / min
The time is 0.5 minutes for air washing, 1 minute for simultaneous backwashing, and 1 to 5 minutes for water backwashing. By repeating this operation 1 to 3 times, SS is discharged out of the system and the clogging is eliminated. At this time, if the processing performance is reduced, the backwashing is followed by the activation treatment.

In the activation, the water filled in the treatment tank 2 is drawn out as a backwash drain after the backwashing is completed, and an activating solution containing an oxidant is supplied to bring it into contact with the granular manganese dioxide layer for a certain period of time. . Due to this activation operation, MnO ₂
MnO ₂ which could not be returned to MnO ₂ returns to MnO ₂ in the same way as the activation reaction in the middle of the treatment, and the oxidizing power is exerted again.

The time for contacting the activation liquid with the granular manganese dioxide layer varies depending on the concentration of the oxidizing agent contained in the activation liquid and the required degree of activation, but it is usually about 5 to 20 minutes. Further, the concentration of the oxidant contained in the activation liquid is such that there is no problem with the activation if about 10% of the initial concentration of the oxidant remains in the activation waste liquid after activation, but as described below, the oxidizer in the activation waste liquid In order to further utilize the above, an oxidizer of 0.2% or more is required. As shown in Fig. 6, when the oxidizing agent is NaClO, the concentration of the oxidizing agent contained in the activator solution is 0.5 as available chlorine.
% Or more is preferable.

When the activation is completed in this way, the entire activation waste liquid is drawn out and stored in the activation waste liquid storage tank 6 and added to the raw water as a part of the oxidizing agent during the treatment. The above-mentioned backwashing and activation operations may be carried out when necessary, but in particular the activation operation needs to be determined according to the removal rate of COD, etc. to be maintained or the desired quality of the treated water.

The water treated in the treatment tank 2 enters the aeration tank / treatment water tank 3 as an oxidizing solution. Here the oxidant is aerated,
It is discharged as highly treated water. As described above, the aeration of the oxidizing liquid is necessary because the pH of the oxidizing liquid is often low because the pH of the raw water is adjusted to 5 to 7 in order to improve the treatment performance in the treatment tank 2. This is to increase the pH of the oxidizing solution to meet the water quality standard value of 5.8 to 8.6.
The increase in the pH of the oxidizing solution due to the aeration is considered to be due to the decarbonation of the carbonic acid or bicarbonate generated by the oxidation in the treatment tank 2. The amount of aeration may be about 0.5 to 1 m ³ air / m ³ tank · Hr, which is the same as the amount of aeration in ordinary activated sludge treatment, and the aeration time is 15 to 30 minutes as shown in FIG.

Next, Tables 1 and 2 show the results of treating the same raw water with the treatment method of the present invention and the conventional activated carbon treatment method. Comparing the example using the electrolytic manganese dioxide of the present invention with the conventional method, SS, COD, BOD, chromaticity, etc. are the same results as the conventional method, NH ₄ -N and general bacteria,
For E. coli, the results are significantly superior to the conventional method. Also, it can be seen that the processing cost can be greatly reduced to 1/17 of the conventional method. Further, in the case of using the palladium-impregnated electrolytic manganese dioxide, the treatment cost can be kept the same as that of using the electrolytic manganese dioxide, and the water quality such as COD, BOD, and chromaticity can be further improved.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

As is apparent from the above description, the advanced sewage treatment method according to the present invention can be applied to chromaticity, COD, BOD
The removability of NH ₄ -N, general bacteria and E. coli is much better than that of the conventional method. Therefore, it is possible to fully comply with the recent trends of COD and nitrogen emission regulations. In addition, the treatment cost can be greatly reduced to 1/17 of the conventional method, and it can be applied to systems that require large-scale treatment such as sewage treatment.

[Brief description of drawings]

FIG. 1 is a flow sheet of the present invention.

FIG. 2 is a graph showing the relationship between the adjusted pH of raw water, the COD removal rate, and the pH of treated water.

[Figure 3] Oxidant addition ratio, COD removal rate and treated water R-Cl
It is a graph which shows the relationship of.

FIG. 4 is a graph comparing COD removal rates when electrolytic manganese dioxide and palladium-impregnated electrolytic manganese dioxide are used.

FIG. 5 is a graph showing the relationship between COD removal rate and LV and SV.

[Fig.6] Recovery time of contact time and COD removal rate and activation waste liquid R-
It is a graph which shows the relationship of Cl.

FIG. 7 is a graph showing the relationship between the aeration time of an oxidizing solution and the pH of highly treated water.

FIG. 8 is a flow sheet of a conventional method.

[Explanation of symbols]

1 pH adjusting tank, 2 treatment tank with granular manganese dioxide layer consisting of electrolytic manganese dioxide or palladium-impregnated electrolytic manganese dioxide, 3 aeration tank and treated water tank, 4 acid storage tank, 5
Oxidizer storage tank, 6 activation waste liquid storage tank, 7 pump, 8 blower, 9 level adjuster, 10 stirrer, 11 pH indicator controller

Claims (5)

[Claims] 1. After adjusting the pH of raw water to 5 to 7, water is passed through a treatment tank filled with granular manganese dioxide by adding an oxidizing agent,
A method for advanced treatment of sewage, which comprises aerating the obtained oxidizing solution to obtain highly treated water. 2. The advanced sewage treatment method according to claim 1, wherein the granular manganese dioxide is electrolytic manganese dioxide. 3. The advanced sewage treatment method according to claim 1, wherein the granular manganese dioxide layer is backwashed in the order of air washing, simultaneous backwashing, and water backwashing when the treatment tank is clogged. 4. When the treatment performance deteriorates, following the backwashing of claim 3, the total amount of water in the treatment tank is withdrawn, and then the activation liquid is brought into contact with the layer of granular manganese dioxide to activate the granular manganese dioxide. The advanced treatment method for sewage according to claim 3, wherein all the activated waste liquid is drawn out. 5. The advanced sewage treatment method according to claim 4, wherein the extracted activation waste liquid is added to raw water as a part of an oxidizing agent.