JPH0677730B2 - Organic wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention removes persistent organic substances such as chromaticity components and phosphorus present in organic wastewater such as sewage secondary treated water and various industrial wastewater. It is about the method.

[Conventional technology]

The total amount of COD _Mn in wastewater discharged to public water areas is partially enforced, and the need to reuse treated water of sewage and other organic wastewater is increasing. It is shifting from degradable to persistent. As a method for removing hardly decomposable organic substances, an adsorption method, a coagulation-sedimentation method, a decomposition method using an oxidizing agent, etc. have been proposed.

Further, as a method for removing phosphorus in water, there are a coagulation sedimentation method, a biological dephosphorization method, a catalytic dephosphorization method and the like. Of these, the catalytic dephosphorization method is a granular material (phosphorus ore, bone charcoal, MgO) that has the ability to remove phosphorus in the presence of calcium and alkali.
, Etc.) to remove phosphorus in water, and it has been noted that the so-called hardly dehydratable sludge does not come out in the process of phosphorus removal.

[Problems to be Solved by the Invention]

By the way, of the conventional methods for removing persistent organic substances,
The adsorption method requires frequent replacement or regeneration of the adsorbent,
This will significantly increase the cost of water treatment. Also,
The coagulation-sedimentation method using a coagulant has a small removal rate of 10 to 30% and cannot be expected to have high removal ability. Further, the decomposition method using an oxidizing agent such as O ₃ , H ₂ O ₂ and Cl ₂ not only requires a large amount of injection of the oxidizing agent to obtain a high removal rate, but also the liquid after the oxidative decomposition is recycled. Had to handle.

On the other hand, the catalytic dephosphorization method has a problem that when organic substances that are difficult to decompose are contained in water, these organic substances cover the surface of the particulate matter in a long period of time, and the phosphorus removal performance is deteriorated.
As a method of solving this, the granular material coated with an organic substance is immersed in an acid or alkaline solution, but there have been problems such as treatment of the waste liquid for regeneration and dissolution of crystallized calcium phosphate.

An object of the present invention is to solve the above-mentioned conventional problems and provide a method for efficiently and stably removing hardly decomposable organic matter and phosphorus in organic wastewater.

[Means for Solving the Problems]

The present invention is a method for treating organic wastewater, which comprises adjusting the pH of the organic wastewater to 3.0 to 6.0 and then contacting it with a granular filter medium having an organic substance adsorption capacity under aerobic conditions.

The present invention is also characterized in that the treated organic wastewater is further contacted with a granular material having a phosphorus removing ability in the presence of calcium and alkali.

Further, the present invention is a method for treating organic wastewater, which comprises adjusting the pH of the organic wastewater to 8.5 to 9.5, and then contacting it with a granular filter medium having an organic matter adsorption capacity under aerobic conditions, and After adjusting the pH of the organic wastewater from which carbonic acid components in the water have been removed as much as possible to 8.5 to 9.5, it is contacted with a granular filter medium having an organic substance adsorption capacity under aerobic conditions, and in the presence of calcium and alkali. It is also characterized in that it is brought into contact with a granular material having a phosphorus removing ability.

[Work]

The operation of the present invention will be described below with reference to the drawings showing an example of an embodiment.

In FIG. 1, the sewage secondary treated water that is the raw water 1 is introduced into the pH adjusting tank 2, and the mineral acid solution 3 is injected while interlocking with the pH value of the pH electrode 4, and the pH is 3.0 to 6.0, preferably 3.0. Adjust to ~ 5.5. In order to reduce the injection amount of the mineral acid solution 3, the biological nitrification action is promoted in the sewage secondary treatment step of the previous stage, and M-
It is better to lower the alkalinity component.

This pH adjusted water is introduced into the reaction tank 5 through the inflow pipe 6,
In the reaction tank 5, a granular filter material 7'having an organic substance adsorption capacity is provided.
Is supported by the lower gravel layer 8 and keeps the inside of the packed bed 7 in an aerobic state while the pH-adjusting water that has flowed in passes through them in a downward flow.

As means for maintaining the inside of the packed bed 7 in an aerobic state, a gas containing at least air or oxygen is blown into the packed bed 7, or air is blown directly into the raw water 1 to dissolve oxygen or raw water. Examples of the method include a method in which an acid is supplied to 1 and water is passed through the packed bed 7 after aeration, or a combination thereof is used, and the method is not particularly limited. In the type in which air or the like is blown into the filling layer 7, it is possible to blow from various levels of the filling layer 7, but it is preferable to blow from below the filling layer 7. For example, as in the illustrated example, in the gravel layer 8 that supports the packed bed 7, an air diffuser 9 connected to the blower 10 is provided to efficiently distribute oxygen evenly throughout the packed bed 7. The whole can always be kept aerobic. The position of the air diffuser 9 is preferably lower than the packed bed 7 as in the illustrated example, but it may be inside the packed bed 7. Further, instead of the gravel layer 8 which supports the packed bed 7, a support plate 13 such as a perforated plate (see FIG. 2) may be used, and in this case, the position of the air diffuser 9 may be above or below the support plate.

When the water flow in the reaction tank 5 is continued in this manner, a microbial film is formed on the surface of the granular filter medium 7 ', the organic matter adsorbed and concentrated on the granular filter medium 7'is decomposed, and the organic matter is adsorbed by the microorganisms. The treated water flows out of the tank through the treated water outflow pipe 11. Such a reaction proceeds efficiently under the unique condition of pH 3.0 to 6.0.

In addition, the water flow direction to the packed bed 7 of the pH adjusting water may be an upward flow instead of the downward flow as described above.

If such a treatment is continued for a long time, clogging occurs in the packed bed 7 and the water flow resistance increases. When a certain water flow resistance is reached, the cleaning air is discharged from the inside of the gravel layer 8 through the air cleaning pipe 12 and the cleaning water is discharged through the treated water outflow pipe 11, and the packed bed 7
The SS trapped inside is removed and part of the microbial film is peeled off.

Further, as the granular filter medium 7 ', an adsorbent having a large specific surface area (preferably 100 m ₂ / g or more) such as activated carbon, bone charcoal or zeolite can be used, but activated carbon or bone charcoal is most preferable. When such a granular filter medium is used, heavy metals can also be removed in the pH range (3.0 to 6.0) of the above operation.

In the example of FIG. 2, a granular filter material 7'having an organic substance adsorbing capacity having a large particle size is used, and the packing layer 7 is supported on a supporting plate 13 such as a porous plate. Air is blown directly from the blower 10 onto the water surface below the support plate 13,
The operation is almost the same as that in the case of FIG. 1, but the treatment efficiency can be improved by circulating the treated water from the lower part of the reaction tank 5 to the upper part of the reaction tank 5 by the circulation pump 14.

Further, FIG. 3 shows an embodiment in which not only COD _Mn in the raw water 1 but also phosphorus is effectively removed. Third
In the figure, the raw water 1 which is the secondary treated water of sewage is adjusted to pH 3.0 to 6.0 with the mineral acid solution 3 and kept in an aerobic state by blowing air and brought into contact with the granular filter medium in the reaction tank 5. The treatment is the same as the treatment method shown in FIG. 1 or FIG. 2 described above, but when treated in this manner, COD _{Mn in the} raw water is removed and at the same time carbonic acid substances are also removed. These substances are
It is known as a substance that inhibits the phosphorus removal reaction in the catalytic dephosphorization method using phosphate rock or the like, but since it has already been removed as described above, calcium and alkali 15 are added to the treated water from the reaction tank 5. Then, after adjusting in the adjusting tank 16, it is introduced into the contact dephosphorization tank 17 to remove phosphorus in the water.

Further, in the treatment as shown in FIGS. 1 and 2, instead of the mineral acid solution 3 injected into the raw water 1, an alkaline solution is injected to adjust the pH of the raw water 1 to 8.5 to 9.5, It is also effective to contact a granular filter medium having an organic substance adsorption capacity under aerobic conditions. Although such treatment under alkaline conditions is slightly less efficient than the treatment under acidic conditions (pH 3.0 to 6.0) described above, COD _Mn content is lower than that of conventional bioactive carbon treatment in the normal pH range. The removal rate was good.

When the catalytic dephosphorization method is combined with this removal of COD _Mn under alkaline conditions, the combination is as shown in FIG. That is, the fourth
In the figure, decarbonation tank 18 is prepared by adding mineral acid solution 3 to raw water 1.
After removing the carbonic acid substance by blowing air (at the same time, DO is fed into the raw water), adjust the calcium concentration with calcium and alkali 15 in the adjusting tank 16 and adjust the pH to 8.5 to 9.5 at the same time. The COD _Mn is removed by passing water through the reaction tank 5 filled with water, and then introduced into the catalytic dephosphorization tank 17 to remove phosphorus in the water. In this case, when the activated carbon packed bed is aerated, the carbonic acid substance in the water is re-inhaled, so that the reaction tank 5 is not aerated.

Further, as shown in FIG. 5, the reaction tank 5 and the contact dephosphorization tank 17 are integrated, and an activated carbon filling layer is laminated on the phosphate rock filling layer.
When the COD / phosphorus removing tank 19 is used, the apparatus and the process can be simplified.

〔Example〕

Example 1 A cylindrical column having an inner diameter of 50 mm and a height of 3,000 mm filled with activated carbon 2 having an effective diameter of 0.8 mm and having a diffusing bulb at the bottom was used as a raw water for secondary treatment of sewage, and a 1% sulfuric acid or 1% NaOH solution was added thereto. Was added to adjust the pH to 2.0, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.0, 9.
It was adjusted to 5, 10.0 respectively and water was passed downward at 33 cc / min. At the same time, air was supplied from the diffuser bulb into the column at 0.1 / min. At this time, the pH at each water passage and the COD _Mn removal ability in water were as shown in Table-1.

The raw water quality was COD _Mn 10.0 to 15.0 (mg /) SS 1.5 to 3.0 (mg /) M-alkalinity 100 to 150 (mg /) Ca 60 to 80 (mg /).

As is clear from Table-1, at the pH of the present invention, the removal rate of COD _{Mn in} the sewage secondary treated water is remarkably high, and the COD _{Mn of} the treated water is high.
The concentration (average value) could be 4.0 mg / or less, and the regeneration of activated carbon was unnecessary during the experimental period of one year.

Example 2 Activated carbon having an effective diameter of 0.8 mm, bone charcoal, and zeolite each having 2
50 mm inner diameter and 3000 mm height filled with a diffusing bulb at the bottom
Table 2 shows the results when water was passed through each of the cylindrical columns at a flow rate of 33 cc / min in a downward flow with the pH of the raw water as shown below being 4.5.

Raw water quality: COD _Mn 9.8 to 17.0 (mg /) SS 1.6 to 3.5 (mg /) M-alkalinity 98 to 120 (mg /) Ca 60 to 80 (mg /) Example 3 The slaked lime and calcium chloride were added to the treated water of pH 4.5 of Example 1 to adjust the pH to 9.0 and Ca 70 to 90 mg /.
50mm inner diameter × height filled with phosphate rock 1 with an effective diameter of 0.45mm
When water was passed through a 3000 mm cylindrical column at a downward flow rate of 30 cc / min, the phosphorus removal rate was 85% (raw water phosphorus concentration 1.0 mg /, effluent phosphorus concentration 0.15 mg /), COD _Mn removal rate for about 1 year. 8
7.5% was obtained.

On the other hand, as a comparative example, the raw water of Example 1 (secondarily treated sewage water) was subjected to aeration (G / L = 5) in a decarbonation tank with a retention time of 15 minutes at pH 4.5, followed by slaked lime and chlorination. When calcium was added to adjust the pH to 9.0 and Ca 60 to 80 mg / min, and water was passed through the cylindrical column in the same manner as above, the phosphorus concentration in the effluent water tended to increase slightly, and the phosphorus removal rate was 60% per year on average. % (Raw water phosphorus concentration 1.0 mg /, effluent phosphorus concentration 0.4 mg /), COD _Mn removal rate was 10%.

Example 4 The raw water of Example 1 (secondarily treated sewage water) was subjected to aeration (G / L = 5) at a pH of 4.5 in a decarbonation tank with a residence time of 15 minutes, and then slaked lime and calcium chloride were added. Add, pH 9.0, Ca
It was adjusted to 70 to 90 mg /. Then, this was passed through a cylindrical column having an inner diameter of 50 mm and a height of 3000 mm, which was packed with 2 activated carbons having an effective diameter of 0.8 mm, at an upward flow rate of 33 cc / min.

When this treated water was passed through a cylindrical column with an inner diameter of 50 mm and a height of 3,000 mm filled with one phosphate ore with an effective diameter of 0.45 mm at an upward flow rate of 30 cc / min, the phosphorus removal rate was 70% for about one year.
(Phosphorus concentration of raw water 1.0 mg /, phosphorus concentration of runoff water 0.3 mg /), C
About 75% of OD _Mn removal was obtained.

On the other hand, as a comparative example, the same raw water was decarbonated and pH adjusted in the same manner as above, and then the inner diameter was filled with 2 sands with an effective diameter of 0.8 mm.
Upflow water was supplied to a cylindrical column of 50 mm x 3000 mm in height. The inside diameter of this treated water filled with one piece of phosphate rock with an effective diameter of 0.45 mm
When water was passed through a 50 mm × 3000 mm high column at an upward flow rate of 30 cc / min, the phosphorus concentration in the effluent tended to rise slightly, and the phosphorus removal rate was 50% per year on average (raw water phosphorus concentration 1.0 mg). /
The phosphorus concentration in the effluent was 0.5 mg /), and the COD _Mn removal rate was 10%.

〔The invention's effect〕

As described above, according to the present invention, by adjusting the pH of the organic wastewater to the optimum range, the organic wastewater is brought into contact with the granular filter medium having an organic substance adsorption capacity under aerobic conditions by an extremely simple operation. The hardly decomposable organic substance can be efficiently and stably removed, and efficient phosphorus removal can be expected by the subsequent catalytic dephosphorization step.

[Brief description of drawings]

1 to 5 are explanatory views showing an embodiment of the present invention. 1 ... Raw water, 2 ... pH adjusting tank, 3 ... Mineral acid solution, 4 ...
pH electrode, 5 ... Reaction tank, 6 ... Inflow pipe, 7 ... Packed bed,
7 '... granular filter medium, 8 ... gravel layer, 9 ... air diffuser, 10 ...
… Blower, 11 …… Treatment water outflow pipe, 12 …… Air cleaning pipe, 13
...... Support plate, 14 ...... Circulation pump, 15 …… Calcium and alkaline agents, 16 …… Adjustment tank, 17 …… Contact dephosphorization tank, 18 ・ ・ ・
… Decarbonation tank, 19 …… COD, phosphorus removal tank.

Front Page Continuation (72) Izumi Hirasawa, Izumi Hirasawa, 1-2-6 Konan, Minato-ku, Tokyo EBARA IN FILCO Co., Ltd. (72) Hiroshi Nakamura, 1-27, Konan, Minato-ku, Tokyo In-house (56) Reference JP 54-3359 (JP, A) JP 57-10382 (JP, A) JP 62-289288 (JP, A) JP 50-104184 (JP, A) )

Claims (4)

[Claims] 1. After adjusting the pH of the organic wastewater to 3.0 to 6.0,
A method for treating organic sewage, which comprises contacting with a granular filter medium having an organic substance adsorption capacity under aerobic conditions. 2. After adjusting the pH of the organic wastewater to 3.0 to 6.0,
A method for treating organic sewage, which comprises contacting with a granular filter medium having an organic substance adsorption capacity under aerobic conditions, and further contacting with a granular substance having a phosphorus removal capacity in the presence of calcium and alkali. 3. After adjusting the pH of the organic wastewater to 8.5 to 9.5,
A method for treating organic sewage, which comprises contacting with a granular filter medium having an organic substance adsorption capacity under aerobic conditions. 4. The pH of the organic wastewater from which carbonic acid components in water are removed as much as possible is adjusted to 8.5 to 9.5, and then contacted with a granular filter medium having an organic substance adsorbing ability under aerobic conditions, and further calcium and A method for treating organic sewage, which comprises contacting with a granular material having a phosphorus removing ability in the presence of an alkali.