JP2012192367A - Treatment device for organic waste water containing nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of decomposition of NHHCOduring evaporation concentration of RO (reverse osmosis) concentrated water in which NHHCOis concentrated, when organic waste water containing nitrogen is treated with methane fermentation, and after microorganisms are removed from the solution treated with methane fermentation, the solution is desalinated with the RO membrane separation device.SOLUTION: A treatment device includes: a methane fermentation tank 1 for subjecting organic waste containing nitrogen to methane fermentation treatment under an anaerobic condition; MF or UF membrane separation device 2 for separating the solution treated with methane fermentation into solid and liquid; an RO membrane separation device 5 for desalination of the filtrate; an evaporation concentration device 6 for further concentrating RO concentrated water; and a means for adding an acid to RO concentrated water. When an acid such as sulfuric acid or hydrochloric acid is added to RO concentrated water, NHHCOis converted to a stable strong acid such as (NH)SOor NHCl which does not decompose even when heated, and then RO concentrated water can be evaporated and concentrated.

Description

  The present invention relates to an apparatus for treating organic physical wastewater containing nitrogen. Specifically, the present invention relates to a treatment apparatus suitable for waste water treatment in which organic waste water containing nitrogen is subjected to methane fermentation treatment under anaerobic conditions and used as raw water for producing pure water.

  In electronic industry factories such as semiconductor manufacturing and liquid crystal manufacturing, alcohols such as isopropyl alcohol (IPA), butyl diglycol (BDG) and methanol, nitrogen such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH) Organic substances, sulfur-containing organic substances such as dimethyl sulfoxide (DMSO) are used as cleaning agents, stripping agents, and the like in process steps, and a large amount of waste water containing such organic substances is generated in pure water. In recent years, in these electronic industrial factories, water recovery has been progressing in which such wastewater is biologically treated and the treated water is reused as a raw material for producing pure water.

  When biologically treated water is reused for the production of pure water, the treated water may be treated with a solid-liquid separation device to separate microorganisms, and then desalted with a reverse osmosis (RO) membrane separation device (for example, JP, 2007-175582, A). Concentrated water obtained by this RO membrane separation apparatus may be discharged into sewers or the like, but in many cases, it is further concentrated by an evaporator or an evaporation tower and then discharged as industrial waste.

2007-175582

When biological treatment of organic physical wastewater containing nitrogen, such as the above-mentioned electronic industrial factory wastewater, is performed by methane fermentation under anaerobic conditions, nitrogen contained in TMAH, MEA, etc. is discharged as ammonia. , These are also neutralized with CO ₂ produced by the decomposition of organic matter and remain in the liquid as NH ₄ HCO ₃ . Since NH ₄ HCO ₃ is a substance with a high removal rate by the RO membrane, when the biologically treated water containing NH ₄ HCO ₃ is subjected to RO membrane separation treatment, NH ₄ HCO ₃ is concentrated in the RO membrane and most of it is concentrated water. To the side. NH ₄ HCO ₃ is decomposed into ammonia, carbon dioxide, and water by heating at about 70 ° C. in an aqueous solution, and therefore cannot be concentrated by an evaporator or an evaporation tower, and contains NH ₄ HCO ₃ . When evaporating and concentrating RO concentrated water, a facility for collecting and removing ammonia gas is required. For this reason, in the case where RO concentrated water cannot be discharged into the sewer, etc., it has led to an increase in industrial waste treatment costs.

In the present invention, when organic wastewater containing nitrogen is subjected to methane fermentation treatment, microbial cells are separated from the methane fermentation treatment liquid, and then desalted with an RO membrane separator to recover water, NH ₄ HCO ₃ is concentrated. It is an object of the present invention to provide a device that solves the problem of decomposition of NH ₄ HCO ₃ when evaporating and concentrating RO concentrated water, and enables evaporating and concentrating this RO concentrated water.

As a result of intensive studies to solve the above problems, the inventors of the present invention added NH ₄ HCO _{3 in} concentrated water to (NH ₄ ) ₂ SO ₄ or NH when an acid such as sulfuric acid or hydrochloric acid is added to RO concentrated water. such as ₄ Cl, to be converted into a salt of a stable strong acid does not decompose even when heated, have found that it is possible to evaporative concentration of RO concentrate.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A methane fermentation tank for subjecting nitrogen-containing organic wastewater to methane fermentation under anaerobic conditions, a microfiltration or ultrafiltration membrane separation device for solid-liquid separation of the methane fermentation treatment liquid, and the microfiltration or A treatment apparatus for organic physical wastewater containing nitrogen, comprising a reverse osmosis membrane separation apparatus for desalting the filtrate of an ultrafiltration membrane separation apparatus, and an evaporation concentration apparatus for further concentrating the concentrated water of the reverse osmosis membrane separation apparatus And a means for adding an acid to the concentrated water of the reverse osmosis membrane separation device introduced into the evaporation concentration device.

[2] The treatment apparatus according to [1], further comprising a biological desulfurization apparatus that oxidizes hydrogen sulfide in the biogas generated from the methane fermentation tank, and the sulfuric acid-containing liquid discharged from the biological desulfurization apparatus is acidified in the concentrated water. An apparatus for treating organic physical wastewater containing nitrogen, characterized by comprising means for adding as

[3] An apparatus for treating organic wastewater containing nitrogen, comprising spraying means for spraying a part of the concentrated water as a pH adjuster of the biological desulfurization device in [2].

According to the present invention, when organic wastewater containing nitrogen is subjected to methane fermentation treatment, microorganisms are separated from the methane fermentation treatment liquid, and then desalted by the RO membrane separator to recover water, NH ₄ HCO ₃ by but adding an acid to the RO concentrate enriched, the _NH 4 HCO ₃ in the concentrate water _{(NH 4),} such as 2 SO ₄ and _NH 4 Cl, the stable salts of strong acids that do not decompose on heating The RO concentrated water can be further concentrated by an evaporator or an evaporation tower, and can be treated as industrial waste. Moreover, by converting to such a strong acid salt, the amount of the concentrated salt itself can be reduced, and the amount of industrial waste generated can be reduced to reduce industrial waste treatment costs.

  The acid added to this RO concentrated water is a sulfuric acid-containing liquid discharged from a biological desulfurization apparatus that oxidizes hydrogen sulfide in biogas generated when methane fermentation treatment is performed on organic wastewater containing sulfur-containing organic substances such as DMSO. By using (usually about pH 1 to 5), acid as a chemical can be made unnecessary.

  Moreover, when using such a biological desulfurization apparatus, by using a part of RO concentrated water (normally about pH 8-12) as an alkali used for pH adjustment of a biological desulfurization apparatus, it is for pH adjustment of a biological desulfurization apparatus. Chemicals can also be dispensed with.

It is a systematic diagram which shows embodiment of the processing apparatus of the organic property waste water containing nitrogen of this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a treatment apparatus for organic physical wastewater containing nitrogen according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a system diagram showing an example of a treatment apparatus for organic physical wastewater containing nitrogen according to the present invention.
In FIG. 1, 1 is a methane fermentation tank, 2 is an immersion membrane separation tank, 3 is a filtrate tank, 4 is an RO water supply tank, 5 is an RO membrane separation apparatus, 6 is an evaporative concentration apparatus, and 7 is a biological desulfurization apparatus.

[Organic wastewater containing nitrogen]
In the present invention, the organic physical wastewater containing nitrogen to be treated is not particularly limited as long as it contains nitrogen and organic matter, and examples thereof include electronic industrial wastewater and chemical factory wastewater. In the manufacturing process of electronic parts such as semiconductors and liquid crystals, a large amount of organic physical wastewater containing various types of nitrogen is generated from the development process, peeling process, etching process, cleaning process, etc., and the wastewater is collected and purified to the pure water level. Therefore, these wastewaters are suitable as the wastewater to be treated of the present invention.

  Such wastewater usually contains organic nitrogen compounds such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH), and alcohols such as isopropyl alcohol (IPA), butyl diglycol (BDG) and ethyl alcohol. Furthermore, organic sulfur compounds such as dimethyl sulfoxide (DMSO) are included.

Wastewater, organics 200~50,000mg / L about as _{COD Cr} concentration, 50~5,000mg-N / L about the organic nitrogen compound as a T-N concentration, total sulfur concentration of organic sulfur compounds treated in the present invention It is preferable that the waste water contains about 10 to 1,000 mg-S / L.

[Methane fermentation treatment]
The organic physical waste water containing nitrogen as described above is first introduced into the methane fermentation tank 1 and subjected to methane fermentation treatment. This methane fermentation tank may be a single tank type in which the acid generation reaction and the methane generation reaction are performed in the same tank, or a two tank type in which each reaction is performed in separate tanks. Each reaction vessel may be of any method such as a floating method (stirring method) or a sludge bed method (sludge blanket method), or may be a carrier addition type or a granulated sludge type.

  Although it does not specifically limit as a methane fermentation tank, It is preferable to use the reaction tank of UASB (upward flow type anaerobic sludge blanket) and MBR (membrane bioreactor) system which can perform high load operation, especially MBR system.

The COD _Cr load of the methane fermenter is preferably 1 to ³⁰ kg / m ³ · d, particularly 2 to 10 kg / m ³ · d. The temperature of the methane fermenter is preferably 20 to 40 ° C. or 45 to 60 ° C., and the HRT is preferably about 3 to 72 hr, particularly preferably 20 to 48 hr.

[Solid-liquid separation of microorganisms]
Methane fermentation broth of methane fermentation tank 1 is fed to the submerged membrane separation tank 2 by a pump P _1, microbial bodies are solid-liquid separation by UF membrane or MF membrane modules 2M. The membrane module may be provided in a separate membrane immersion tank as shown in FIG. 1 or in a methane fermentation tank. Further, the treatment liquid may be circulated through an inner pressure type tank outer membrane that is not an immersion type.
An aeration tube 2A is provided below the UF membrane or MF membrane module 2M of the submerged membrane separation tank 2. Part of the biogas generated in the methane fermenter 1 is aerated by the blower B from the diffuser 2A, and the UF membrane or the MF membrane module 2M peels off the membrane surface by the aerated airflow of the biogas from the diffuser 2A. This prevents clogging of the film. The membrane shape of the UF membrane or MF membrane module 2M may be any of a flat membrane, a tubular membrane, a hollow fiber membrane, and the like.

  In this case, the gas of the gas phase in the submerged membrane separation tank 2 and the liquid in the tank are circulated to the methane fermentation tank 1 through the pipes 11 and 12, respectively.

[RO membrane separation treatment]
Withdrawn by dipping the membrane separation tank 2 of UF membranes, or pumps P ₂ from MF membrane module 2M filtrate, by the pump P ₃ via a filtrate tank 3 and RO water tank 4 is introduced into the RO membrane separation device 5 desalination It is processed. The permeated water of the RO membrane separation device 5 is discharged out of the system as treated water.

  On the other hand, a part of the concentrated water is circulated to the RO water tank, and the remainder (in FIG. 1, the other part of the RO concentrated water is fed to the biological desulfurization device 7) is evaporated by an evaporator, an evaporation tower, or the like. The concentrated salt 6 is fed to the concentrating device 6 and concentrated by heating. The concentrated salt is discharged out of the system and disposed of as industrial waste.

[Addition of acid to RO concentrated water]
In the present invention, an acid is added to this RO concentrated water, and NH ₄ HCO ₃ in the RO concentrated water is not decomposed even by heating at about 70 to 100 ° C. such as (NH ₄ ) ₂ SO ₄ or NH ₄ Cl. The salt is converted into a salt and introduced into the evaporative concentration apparatus 6.

In FIG. 1, a sulfuric acid-containing liquid (usually about pH 1 to 5) generated in the biological desulfurization apparatus 7 is introduced by the pump P ₄ as an acid to be added to this RO concentrated water. The sulfuric acid-containing liquid and a chemical acid may be used in combination.
The acid added to the RO concentrated water may be any acid that can form a more stable ammonium salt than NH ₄ HCO ₃ , and sulfuric acid, hydrochloric acid, or the like is usually used.

The amount of acid added to the RO concentrated water may be such that NH ₄ HCO _{3 in} the concentrated water is converted to a stable salt such as (NH ₄ ) ₂ SO ₄ or NH ₄ Cl. About 1 to 3 equivalents of NH ₄ HCO _{3 in} water is added. If the amount of acid added is too small, NH ₄ HCO ₃ remains, which is not preferable. If the amount is too large, the amount of chemical used or the amount of concentrated salt increases, which is not preferable.

[Evaporation concentration treatment]
In the evaporative concentration apparatus 6, the concentrated water to which the acid has been added is heated to about 60 to 100 ° C. and evaporated and concentrated under a reduced pressure of about 250 to 700 mmHg.

In the present invention, per the evaporative concentration of RO _concentrate, NH 4 HCO _{(NH 4)} a _NH 4 HCO ₃ concentration in water by adding an acid to the RO concentrate containing ₃ 2 SO ₄ or _NH 4 stable as Cl Therefore, NH ₄ HCO ₃ is not decomposed and ammonia is not generated under the above evaporative concentration conditions. Therefore, an ammonia gas collecting and removing device is unnecessary. In addition, the amount of concentrated salt can be reduced by converting NH ₄ HCO ₃ into (NH ₄ ) ₂ SO ₄ or NH ₄ Cl.

[Biodesulfurization treatment]
When the wastewater to be subjected to the methane fermentation treatment contains an organic sulfur compound such as DMSO, the biogas generated in the methane fermentation tank 1 contains hydrogen sulfide. Therefore, in the apparatus of FIG. Hydrogen sulfide is oxidized to sulfuric acid by introducing it into the apparatus 7 and subjecting it to biological desulfurization.

In this biological desulfurization apparatus 7, since hydrogen sulfide is oxidized and becomes sulfuric acid, the pH is lowered. Therefore, it is necessary to add an alkali and adjust the pH to about 3 to 6 suitable for biological desulfurization. In the apparatus of Figure 1, the alkali as RO membrane separator 5 concentrated water (usually about PH8～12) microbial layer of the biological desulfurization by introducing part biological desulfurization apparatus 7 from the pump P ₅ for the pH adjustment However, an alkali agent as a chemical may be separately sprayed, or both the alkali agent and RO concentrated water may be sprayed.

  The biological desulfurization apparatus 7 needs to be added with nutrients necessary for the desulfurization microorganisms, but the RO concentrated water is added with various kinds of water added to promote the methane fermentation process well in the pure water wastewater treatment. Therefore, the use of this RO concentrated water as an alkali for adjusting the pH of the biological desulfurization apparatus 7 makes it unnecessary to add nutrients to the biological desulfurization apparatus 7. You can also. However, a nutrient may be added separately from the RO concentrated water.

The desulfurization exhaust gas from the biological desulfurization apparatus 7 is discharged out of the system and sent to the place where methane gas is used. In addition, as described above, a part of the sulfuric acid-containing liquid generated in the biological desulfurization apparatus 7 is added as acid to the RO concentrated water from the pump P _4, and the remaining part is discharged out of the system as waste water.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example 1]
Waste water of the following water quality (main components are MEA, TMAH, DMSO) discharged from the liquid crystal manufacturing factory was treated with the apparatus shown in FIG. 1 (drainage amount 1.8 m ³ / d).

<Drainage water quality>
TOC: 100 to 300 mg / L (average 250 mg / L)
COD _Cr : 350 to 1,060 mg / L (average 880 mg / L)
TN: 42-130 mg-N / L (average 105 mg-N / L)
TS: 21-62 mg-S / L (average 51 mg-S / L)

First, 35 ° C. in complete mixing type methane fermentation tank 1 of the real volume 0.375m ^3, _{COD Cr} load of 4.2kg / ^{m 3} · d, is treated with HRT5hr, hollow fiber methane fermentation broth MF membrane module (Mitsubishi Solid-liquid separation was performed with 2M (manufactured by Rayon, membrane area 6 m ² , pore size 0.4 μm), and the filtrate was desalted with an RO membrane separator (manufactured by Nitto Denko, ES-20, 0.75 MPa). To 0.1 m ³ / d of RO concentrated water (pH 10-11), sulfuric acid-containing liquid (pH 3, sulfuric acid content 1,300-1,500 mg-SO ₄ / L) 0.05 m from biological desulfurization device 7 ³ / d was added, and the solution was evaporated and concentrated under reduced pressure at 70 ° C. and 300 mmHg with an evaporation concentrator (evaporator) 6 to obtain concentrated salt 40 to 50 L / d.
Of the remainder of the RO concentrated water, 0.1 m ³ / d was fed to the biological desulfurization apparatus 7.

The biogas obtained in the methane fermentation treatment tank 1 was circulated as an aeration gas in the diffuser pipe 2A of the submerged membrane separation tank 2 at 50 NL / min, and the remainder was desulfurized by the biological desulfurization apparatus 7.
This biological desulfurization apparatus 7 was sprayed with 0.1 m ³ / d of RO concentrated water to obtain a desulfurization exhaust gas of 600 NL / d and a sulfuric acid-containing liquid of 0.1 m ³ / d.
As described above, a part of this sulfuric acid-containing liquid was added to the RO concentrated water, and the remainder was discharged out of the system.

  In such a process, it was possible to stably perform the concentration process without generating ammonia during the heating and evaporation of the RO concentrated water in the evaporative concentration apparatus 6.

[Comparative Example 1]
In Example 1, when the same treatment was performed except that the sulfuric acid-containing liquid from the biological desulfurization apparatus was not added to the RO concentrated water, ammonia was generated by decomposition of NH ₄ HCO ₃ in the evaporation concentration apparatus 6 and evaporated. Concentration could not be performed.

DESCRIPTION OF SYMBOLS 1 Methane fermentation tank 2 Immersion membrane separation tank 3 Filtrate tank 4 RO water supply tank 5 RO membrane separation apparatus 6 Evaporation concentration apparatus 7 Biodesulfurization apparatus

Claims (3)

A methane fermentation tank for methane fermentation of an organic wastewater containing nitrogen under anaerobic conditions;
A microfiltration or ultrafiltration membrane separation device for solid-liquid separation of the methane fermentation treatment liquid;
A reverse osmosis membrane separation device for desalting the filtrate of the microfiltration or ultrafiltration membrane separation device;
In an apparatus for treating organic wastewater containing nitrogen, comprising an evaporating and concentrating device for further concentrating the concentrated water of the reverse osmosis membrane separator,
An apparatus for treating organic wastewater containing nitrogen, comprising means for adding an acid to the concentrated water of the reverse osmosis membrane separation apparatus introduced into the evaporation and concentration apparatus.   The treatment apparatus according to claim 1, further comprising a biological desulfurization device that oxidizes hydrogen sulfide in the biogas generated from the methane fermentation tank, and the sulfuric acid-containing liquid discharged from the biological desulfurization device is added to the concentrated water as an acid. An apparatus for treating organic physical wastewater containing nitrogen, characterized by comprising means.   The processing apparatus for organic waste water containing nitrogen according to claim 2, further comprising spraying means for spraying a part of the concentrated water as a pH adjuster of the biological desulfurization apparatus.

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