JP3377941B2 - Leachate treatment method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating leachate and an apparatus therefor, and more particularly to a water treatment method and a water treatment apparatus for desalting and highly treating leachate wastewater at a managed final disposal site.

[0002]

2. Description of the Related Art At present, it is common practice to dispose of all waste materials or landfill at a final disposal site after intermediate treatment such as incineration.

The leachate generated at this final disposal site contains pollutants such as salts and organic substances that are leached from the waste, and requires advanced water treatment.

Therefore, in order to remove the leachate contaminants,
Conventionally, a water treatment device as shown in FIG. 3 has been used.

That is, the waste water is stored in the flow rate adjusting tank 31, calcium is removed in the calcium removing tank 32, and then organic matter is removed and denitrifying in the biological treatment tank 33. The treated water is separated, and the treated water is treated as treated water after passing through the sand filter tank 35, the activated carbon treatment tank 36 and the chelate adsorption treatment 37.

[0006]

However, when the leachate is treated with such a water treatment device, although some salts such as calcium and some organic substances can be removed, some salts such as calcium can be removed. Other than the above, salts such as NaCl, organic substances that are hardly biodegradable, and organic substances that are difficult to adsorb activated carbon cannot be completely removed. Therefore, when the treated water is discharged as it is to a river or the like, there is a problem that the river or soil may be contaminated by these salts and undecomposed organic matter.

Therefore, it is conceivable to treat sewage using a permeable membrane such as a reverse osmosis membrane capable of removing salts and hardly decomposable organic substances in raw water that cannot be removed by such a water treatment device.

When the raw water containing salts and organic substances is permeated, this permeable membrane separates the salt organic substances into a concentrated liquid and treated water from which salts have been removed to remove salts.

However, when treated with such a permeable membrane, the treated water separated is easy to treat whether it is reused or discharged as it is, but raw water contains organic substances. If so, the organic matter is mixed into the concentrated liquid without being decomposed, and therefore the concentrated liquid cannot be discharged and reused as it is, and how to carry out this post-treatment has been an important issue.

The present invention has been made to solve such a problem, and an object of the present invention is to easily carry out post-treatment of a concentrated solution obtained by membrane separation.

[0011]

The present invention has been made as a method for treating leachate and an apparatus therefor in order to solve such a problem. The characteristic feature of the treatment method is that leachate containing organic matter is treated. After separation by the membrane separation treatment device, the separated concentrated liquid is evaporated to dryness in the evaporator 23, and the exhaust gas from the evaporator 23 is condensed in the condenser 24, and then condensed by the condenser 24. The biological treatment of condensate.

Another feature of the treatment method is that the leachate containing organic matter is separated by a membrane separation treatment device, the separated concentrated liquid is evaporated to dryness by an evaporation device 23, and then the evaporation device 23. It is to pyrolyze the solid content discharged from the.

Further, the treatment device is characterized in that a membrane separation treatment device for introducing leachate containing organic matter, an evaporation device 23 for evaporating the concentrated liquid from the membrane separation treatment device to dryness, and an evaporation device 23 are used. It comprises a condensing device 24 for condensing the exhaust gas and a biological treatment device 25 for biologically treating the condensate condensed by the condensing device 24.

Another feature of the treatment apparatus is that the membrane separation treatment apparatus introduces the leachate containing organic substances, the evaporation apparatus 23 that evaporates the concentrated liquid from the membrane separation treatment apparatus to dryness, and the evaporation apparatus. And a heating device 26 for thermally decomposing the solid content discharged from 23.

The concentrated water concentrated by the membrane separator is
Concentrated with high concentration of salts. The salt (by-product salt) obtained by evaporating this contains an organic substance together with the salt.

This by-product salt is packed in bags and stored (landfill).
If it is reused, it may be reused for industrial purposes.In particular, if it is reused for industrial purposes, be sure that organic substances are decomposed and that dioxin etc. are concentrated even when stored. When thinking, it is desirable to perform thermal decomposition.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the structure of the apparatus for treating exudate water according to the present embodiment will be described. In FIG. 1, reference numeral 1 is a regulating pond for storing and adjusting the leachate from the final disposal site 2 as raw water, and 3 is the adjusting tank. It is a coagulation sedimentation tank for coagulating sedimentation of raw water supplied from the pond 1.
(Suspended solid) Decomposition, and if necessary, calcium and the like in raw water will be removed.

At this time, when polyaluminum chloride (PAC), soda ash (Na ₂ CO ₃ ) or iron is removed as a coagulant, sodium hypochlorite (NaClO) or the like is used to adjust the pH. Caustic soda (NaOH) or hydrochloric acid (HCl) is used for the.

Reference numeral 4 denotes a pH for further adjusting the pH of the treated water as the separated liquid which has been coagulated and settled in the coagulating and settling tank 3.
In the pH adjusting tank 4, hydrochloric acid (HCl) is added in the pH adjusting tank 4 in order to adjust the pH to be weakly acidic in order to prevent scaling of the reverse osmosis device.

Reference numeral 5 is a sand filter for filtering the treated water whose pH has been adjusted in the pH adjusting tank 4, and this sand filter 5 is S
Iron removal, manganese removal, and the like are performed when necessary for removing S.

Air is introduced into the sand filter 5.

Reference numeral 6 is a filtered water tank for storing the filtrate filtered by the sand filter 5.

Reference numeral 7 denotes a reverse osmosis membrane device into which the treated water from the filtered water tank 6 is introduced, and the flat membrane shown in FIG. 2 is used as the reverse osmosis membrane. Further, when NaClO is added to the treated water immediately before the introduction into the reverse osmosis membrane device 7 for the purpose of removing iron, NaHSO ₃ is added and reduced. When the scale formation tendency is strong, the dispersant CX-2500 (manufactured by Shinko Pantec) is injected.

Numeral 8 is a second reverse osmosis membrane device for introducing the permeated liquid separated and permeated by the reverse osmosis membrane device 7,
As shown in FIG. 2, the reverse osmosis membrane device 8 includes a reverse osmosis membrane portion 14 in which a disk-shaped reverse osmosis membrane 12 is provided between disk-shaped spacers 13 in a cylindrical device body 11. Are stacked and configured.

A raw water flow passage 15 for introducing raw water is provided on the inner peripheral surface of the main body 11 of the reverse osmosis membrane device 2, and the raw water flow passage 15 is provided.
From this, raw water is introduced to the surface of the reverse osmosis membrane 12. Further, an end plate 16 is provided above the reverse osmosis membrane portion 14 so as to withstand a pressure higher than the osmotic pressure.

Reference numeral 18 denotes a treated water pipe penetrating the central portion of the reverse osmosis membrane portion 14, and the treated water pipe 18 discharges the treated water separated by the reverse osmosis membrane 12.

Further, 19 is a concentrated water pipe, and each reverse osmosis membrane 12
The concentrated water concentrated by is discharged to the outside of the apparatus main body 11.

Reference numeral 9 is a neutralization sterilization tank for neutralizing and sterilizing the permeate that has passed through the second reverse osmosis membrane device 8. In the neutralization sterilization tank 9, caustic soda (NaOH) and hydrochloric acid (HC) are used.
1) or sulfuric acid (H ₂ SO ₄ ) is added.

Reference numeral 10 denotes a discharge pond in which the treated water neutralized and sterilized in the neutralization and sterilization tank 9 is discharged.

Reference numeral 20 denotes an NF membrane device provided with a nanofilter (NF) as a permeable membrane into which the concentrated water separated by the reverse osmosis membrane device 7 is introduced and filtered.
In the membrane device 20, an NF membrane can remove salts in concentrated water, particularly salts of divalent or more negative ions, such as CaSO _4, by filtration, and can remove most of organic substances.

The NF membrane device 20 is housed in a state in which a large number of plate type rectangular NF membranes are stacked in a cylindrical body, and the end portion of the laminated body is an end plate provided with water passage holes. It is sealed with.

Reference numeral 21 is a high-pressure reverse osmosis membrane apparatus for treating concentrated water, which is provided for further desalting the filtered water filtered by the NF membrane apparatus 20. Similar to the osmosis membrane device 7, a plurality of modules in which disk-shaped reverse osmosis membranes are provided between spacers are stacked in a cylindrical device body. It can be operated at a water height of 200 bar.

The high-pressure reverse osmosis membrane device 21 is formed to be capable of performing a separation treatment in which the concentrated water is highly concentrated by applying a higher pressure than the reverse osmosis membrane device 7.

22 is the NF membrane device 20 and the reverse osmosis membrane device 7
In the crystallization tank 22 into which the concentrated water separated in (1) is introduced, the salts remaining in the treated water are precipitated as solid matter in the crystallization tank 22.

23 is a dryer as an evaporator for evaporating and drying the solid matter generated in the crystallization tank 22, and 24 is a condenser for condensing the exhaust gas from the dryer 23.

Reference numeral 25 is an aeration tank as a biological treatment tank for biologically treating the condensate condensed in the condenser 24. Sodium phosphate (Na ₃ PO ₄ ) is added to the aeration tank 25. It

Reference numeral 26 denotes a calcining and refining furnace as a heating device for calcining the solid matter evaporated and dried by the dryer 23, and 27 denotes a storage of by-product salt produced from the calcining and refining furnace 26. A by-product salt storage tank is shown. The evaporative drying device and the firing and refining furnace may be the same device.

Next, a treatment method for treating leachate by the leachate treatment apparatus having the above-mentioned structure will be described.

First, raw water is supplied to a coagulation sedimentation tank 3 from a regulating pond 1 for adjusting leachate leached from a final waste disposal site 2 as raw water, and polyaluminum chloride as a coagulant is supplied in the coagulation sedimentation tank 3. (PAC) or Ca removal is necessary, soda ash (Na ₂ CO ₃ ) or iron removal is required, sodium hypochlorite (NaClO) is added, and caustic soda (NaOH) is added for pH adjustment. ) And hydrochloric acid (H
Cl) is also added.

More specifically, Ca contained in raw water,
Sodium ash (Na ₂ CO ₃ ) in an amount equal to or more than the value obtained by subtracting the equivalent of bicarbonate from the equivalent of Ba was added, and caustic soda (NaO) was added.
H) is used to set the pH to 9.5-11.5. In some cases, soda ash may be slightly less than the equivalent.

20 to 50 mg / L of aluminum salt coagulant was used.
Sometimes added, Ca, Ba to CaCO ₃, BaCO₃age
To separate the precipitate.

By removing Ca and Ba by such aggregation and precipitation, CaCO ₃ , CaCO ₄ , BaCO ₃ and Ba are removed.
It is possible to prevent scaling of the reverse osmosis membrane device due to CO ₄ , CaSO ₄ , BaSO ₄ , Ca ₃ (PO ₄ ) _2, or the like.

Further, as described above, the pH is set to 5.0 to 7.0 by adding an acid such as hydrochloric acid (HCl), and suspended solids generated by lowering the pH can be removed by filtration. it can.

Next, the treated water coagulated and precipitated in the coagulation sedimentation tank 3 is introduced into the pH adjusting tank 4 and the pH thereof is adjusted by adding hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ), or the like.

Next, the treated water after the pH adjustment is the sand filter 5
The sand filter 5 removes iron and manganese when necessary.

Next, the permeated liquid filtered by the sand filter 5 is introduced into the filtered water tank 6 and further into the reverse osmosis membrane device 7. If NaClO remains at the inlet of the reverse osmosis unit,
Add HSO ₃ etc. and reduce. In order not to damage the membrane and when there are many scale components, add dispersant CX-2500 or the like.

The reverse osmosis membrane of the reverse osmosis membrane device 7 is a semipermeable membrane which can be filtered at the molecular level when a pressure higher than the osmotic pressure is applied, and also removes phosphorus, organic substances, nitrogen and other salts such as calcium and sodium. be able to.

As described above, the reverse osmosis membrane device 7 has a structure in which the disc-shaped reverse osmosis membranes 12 are laminated, and applies pressure when raw water flows between the surface of the reverse osmosis membrane 12 and the spacer 13. The reverse osmosis membrane 12 permeates only water and the desalted treated water is accumulated inside the membrane, and the treated water passes through a treated water pipe 18 vertically provided in the central portion of the apparatus main body 11 and the reverse osmosis membrane device 7 Is discharged as treated water.

On the other hand, the raw water is discharged as concentrated water from the reverse osmosis membrane device 7 through the concentrated water pipe 19 passing between the reverse osmosis membrane 12 and the spacer 13.

The treated water discharged from the reverse osmosis membrane device 7 is further desalted by the second reverse osmosis membrane device 8 and discharged as high-purity treated water.

The treated water discharged from the second reverse osmosis membrane device 8 is stored in the neutralization sterilization tank 9 such as caustic soda (NaOH) or hydrochloric acid (H).
Cl) or sulfuric acid (H ₂ SO ₄ ) is neutralized and sterilized, and then discharged to the discharge pond 10.

On the other hand, the concentrated liquid discharged from the reverse osmosis membrane device 7 is introduced into the NF membrane device 20.
Can effectively remove most of salts, particularly divalent or higher valent ions such as CaSO ₄ and organic substances in the concentrated solution by filtration.

Then, the concentrated water treated by the NF membrane device 20 is introduced into the high pressure reverse osmosis membrane device 21. At this time, since CaSO _{4 and the} like are removed from the concentrated water by the NF membrane, the high pressure reverse osmosis is carried out. It is possible to prevent performance deterioration due to the scale of these salts adhering to the reverse osmosis membrane of the membrane device 21.

Further, a part of the concentrated liquid generated in the NF membrane device 20 and the highly concentrated liquid generated in the high pressure reverse osmosis membrane device 8 is introduced into the crystallization tank 22.

In the crystallization tank 22, salts contained in these can be deposited and removed as solids.

The solid matter thus precipitated in the crystallization tank 22 and the liquid concentrated by the high-pressure reverse osmosis membrane device 28 are supplied to the dryer 23 as an evaporator, and the exhaust gas from the dryer 23 is It is supplied to the condenser 24 and condensed.

The condensate condensed by the condenser 24 contains low-boiling organic matter, ammonia, etc. depending on the water quality of the raw water, the pH value at the inlet of the evaporator, etc., and is therefore supplied to the aeration tank 25 as a biological treatment tank. , Biological treatment, BOD removal, and / or nitrification in the aeration tank 25.

Then, the treated water that has been biologically treated is stored in the regulating pond 1.
Return to and process again.

Thus, by biological treatment,
Even if the condensed water contains a large amount of volatile organic substances and the condensed water contains a large amount of BOD and nitrogen components, the organic substances in the condensed liquid are removed and the water quality is improved.

On the other hand, the solid matter evaporated and dried in the dryer 23 is reused for industrial purposes and, if purification is required, it is supplied to the firing and refining furnace 26 for firing and refining.

As a result of the calcination and purification as described above, the dried and solidified salt is free of organic substances, organic chlorine compounds such as dioxins contained in trace amounts, and water.

As the calcination and purification method, organic matter is completely combusted and decomposed at 800 ° C. or higher, exhaust gas is treated and salt is rapidly cooled so that dioxin is not generated at the time of combustion, or after the organic matter is incinerated by injecting air first. Deoxidation is carried out by dechlorinating in a reducing atmosphere having an oxygen concentration of 1 to 2% or less without introducing air at 350 to 550 ° C.

It is also possible to perform the drying and solidification (evaporating apparatus) and the baking and refining in the same apparatus.

For example, when used as an industrial salt for electric equipment refining as a reuse destination of a by-product salt, if necessary, Ca,
It is desirable to remove Fe and Mn. In such a case, Ca is removed by Na ₂ CO ₃ or the like in the coagulating sedimentation tank.
In addition, the coagulation-sedimentation equipment and iron removal and manganese removal filtration are used
e, Mn are removed. Generally, by-product salts are easier to reuse if they have a composition close to that of natural salts. Therefore, even if a chloride such as polyaluminum chloride is used as a coagulant,
_It is desirable to use HCl over ₂ SO ₄ . For this purpose, the removal of Ca, the removal of Fe and Mn, and the removal of the organic matter by firing are also carried out if necessary.

Next, the by-product salt produced in the calcination refining furnace 26 is stored in the by-product salt storage tank 27.

Further, the solid matter generated by the coagulation sedimentation in the coagulation sedimentation tank 3 is dehydrated as sludge, supplied to the sludge dehydration tank 29, and further returned to the final disposal site 2. If sludge from the crystallization tank in front of the NF equipment and concentrated water from the high-pressure reverse osmosis equipment are treated separately, the concentrated water from the high-pressure reverse osmosis equipment will pass through the NF membrane, and harmful organic substances will be removed. , Mg
Since a small amount of such a divalent salt is included, the baking and refining process is simplified.

The water quality of permeated water, concentrated water, etc. treated by the above-mentioned treatment of leachate is shown in the following Tables 1 and 2 in comparison with the water quality of leachate as raw water.

[0069]

[Table 1]

[0070]

[Table 2]

Table 3 shows the estimated composition of the concentrated salt.

[0072]

[Table 3]

In the above embodiment, the reverse osmosis membrane device was used as the membrane separation device, but the type of the membrane separation device is not limited to this, and the point is that an organic substance having a separation membrane,
A membrane separator that disperses the salt may be used.

In the above embodiment, the dryer is used as the evaporator for evaporating and drying the separated concentrated liquid, but the kind of the evaporator is not limited to this.

Further, in the above embodiment, biological treatment was performed using the aeration tank 25. However, the method is not limited to the method using the aeration tank 25, and any method such as a floating method, a carrier method, a biofilm, etc. may be adopted. It is also possible to adopt an appropriate method depending on the water quality.

Further, the adjusting basin 1, the coagulating sedimentation tank 3, the pH adjusting tank 4, the sand filter 5, the filtered water tank 6, the neutralization sterilization tank 9, the discharge tank 10, the NF membrane device 20, the high pressure reverse osmosis membrane device 21, The crystallization tank 22 and the like are not essential to the present invention and may be provided as needed.

Furthermore, in the above embodiment, the solid matter after evaporation to dryness was purified by baking, but it is also possible to carry out post-treatments other than baking purification.

Further, in the above embodiment, the reverse osmosis membrane device 7 is used.
The treated water separated in step 1 was treated by the second reverse osmosis membrane device 8 provided further downstream, but it is not a condition to provide such a second reverse osmosis membrane device.

However, if the reverse osmosis membrane treatment is performed in multiple stages as in the above embodiment, the quality of treated water is further improved.

Further, in the above embodiment, the reverse osmosis membrane device using the disc-shaped flat plate reverse osmosis membrane is used as the second reverse osmosis membrane device 8. However, the shape of the reverse osmosis membrane to be used is as follows. In addition to this, a reverse osmosis membrane of any shape such as a hollow fiber type, a spiral type and a tubular type may be used.

[0081]

As described above, according to the present invention, after leachate containing organic matter is separated by the membrane separation treatment device, the separated concentrated liquid is evaporated to dryness by the evaporation device, and from the evaporation device, The exhaust gas of is condensed by a condenser, and then the condensate condensed by the condenser is biologically treated,
There is an effect that the treatment of the concentrated liquid after the membrane separation treatment, which has been a problem in the past, can be effectively performed.

By drying and calcining and refining the concentrated liquid, the by-product salt can be reused as an industrial salt.

Further, since the condensate after evaporation to dryness is biologically treated, there is an effect that the entire apparatus becomes compact as compared with a biological treatment apparatus used for general wastewater treatment.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a water treatment device as one embodiment.

FIG. 2 is a schematic sectional view of a reverse osmosis membrane device.

FIG. 3 is a schematic configuration diagram of a conventional water treatment device.

[Explanation of symbols]

7 ... Reverse osmosis membrane device 23 ... Dryer 24… Aggregator 25… Aeration tank 26 ... Firing and refining furnace

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 1/44 C02F 1/44 K (72) Inventor Kiyoshi Kinoshita 1-29, Minamino, Shijo-Nawate City, Osaka (72) Inventor Ushikoshi Ken-ichi 540-41 Nakamura, Inami-cho, Kako-gun, Hyogo Prefecture (56) Reference JP-A-11-165171 (JP, A) JP-A-11-131965 (JP, A) JP-A-10-137759 (JP, A) Special Kaihei 9-253693 (JP, A) JP-A-8-192188 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 9/00 501-504 C02F 1/44

Claims (4)

(57) [Claims] 1. Leachate containing organic substances is separated by a membrane separation treatment device, and the separated concentrated liquid is evaporated to dryness by an evaporator 23, and exhaust gas from the evaporator 23 is condensed.
A method for treating leachate, comprising condensing at 24, and then subjecting the condensate condensed by the condensing device 24 to biological treatment. 2. Leachate containing organic matter is separated by a membrane separation device, the separated concentrated liquid is evaporated to dryness by an evaporator 23, and then the solid content discharged from the evaporator 23 is heated. A method for treating leachate, which comprises decomposing. 3. A membrane separation treatment device for introducing leachate containing organic matter, an evaporation device 23 for evaporating and drying the concentrated liquid from the membrane separation treatment device, and a condensing device for condensing exhaust gas from the evaporation device 23. A treatment apparatus for leachate, comprising 24 and a biological treatment apparatus 25 for biologically treating the condensate condensed by the condenser 24. 4. A membrane separation treatment device for introducing leachate containing organic matter, an evaporation device 23 for evaporating and drying the concentrated liquid from the membrane separation treatment device, and a solid content discharged from the evaporation device 23 is heated. A treatment device for leachate, comprising a heating device 26 for decomposing.