Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-03-30
2001-12-11
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S205000, C210S908000, C210S916000
Reexamination Certificate
active
06328899
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and an apparatus for treating wastewater containing organic sulfur compounds, and more particularly, a method for biologically decomposing wastewater containing organic sulfur compounds such as dimethyl sulfoxide (hereinafter referred to DMSO), etc., while suppressing offensive odor, and an apparatus for carrying out such decomposition.
2. Description of the Prior Art
Accompanying introduction of DMSO as release agents and cleaning agents in the field of the electronic industry, needs for decomposing of DMSO are increasing. For such needs, the present inventors have developed a biological treatment method of decomposing DMSO, as described in Japanese Patent No. 2769973.
For biologically decomposing DMSO, nitrogen and phosphorus are needed. However, rinsing water generated through the manufacturing process of electronic parts does not contain nitrogen and phosphorous, so that ammonia or other ammonium compounds, as a source of nitrogen has to be added to the rinsing water.
Therefore, a conventional apparatus for biologically decomposing wastewater includes an ammonia reservoir tank
5
a
in addition to a pH adjustment tank
1
a
and a biological treatment tank
2
a
, as illustrated in FIG.
2
. The ammonia reservoir tank
5
stores ammonia or ammonium compounds for supplying them to the pH adjustment tank
1
a
. This conventional apparatus, however, poses a problem of involving the additional expenses for purchasing ammonium compounds, etc., to be used as the source of nitrogen, and necessitating the installation of the ammonia reservoir tank, resulting in the large size of equipment.
On the other hand, factories, which manufacture electronic parts, use tetramethylammonium hydroxide (hereinafter referred to TMAH) as a developing solution, and discharge wastewater having a TMAH concentration of about 0.5 to 2 wt. %, the disposal of which wastewater requires considerable cost. The factories also discharge monoethanolamine in addition to TMAH, which poses a problem of how to treat it. Conventionally, specialized companies or the like usually dispose of MEA containing wastewater or TMAH containing wastewater, while there has been developed, in these years, a technique for biologically treating such wastewater without the necessity of the other wastewater to be mixed therewith. However, those conventional methods pose a problem of requiring considerable cost for the treatment of the wastewater, which will be carried out in a different place from the factory.
The unit cost for treating the TMAH containing wastewater is about 50,000 Japanese yen (JNY) per 1 m
3
. When the wastewater of 15 m
3
is to be treated, it would cost about 750,000 JNY per day.
For TMAH, it contains nitrogen in an amount of 15.3 wt. %. This means that, even if TMAH contained in the wastewater has a concentration of 1 wt. %, the wastewater to be treated has a nitrogen concentration of 1530 mg/L. To remove nitrogen of such a high concentration, additional equipment or the like for removing nitrogen would be required.
It is an object of the present invention to provide a method of treating wastewater containing organic sulfur compounds that is capable of treating the wastewater without the use of ammonia or other ammonium compounds as the source of nitrogen, and hence reducing the cost for it, as well as omitting the ammonia reservoir tank and hence reducing the space for the installation of the wastewater treatment equipment.
It is another object of the present invention to provide a method of treating wastewater containing sulfur compounds that is capable of reducing cost for treating waste materials such as TMAH and MEA.
It is a still further object of the present invention to provide an apparatus for carrying out the above method.
SUMMARY OF THE INVENTION
In accordance with the above objects, there is provided a method of treating wastewater containing organic sulfur compounds. The method includes treating the wastewater containing the organic sulfur compounds by adding wastewater containing a quaternary ammonium compound or wastewater containing an amine thereto.
The quaternary ammonium compound is preferably tetramethylammonium hydroxide.
The amine is preferably monoethanolamine.
The amount of the quaternary ammonium compound or the amine to be added in the wastewater containing the organic sulfur compounds is preferably adjusted according to the concentration of organic substances in the wastewater containing the organic sulfur compounds.
More preferably, the amount of the quaternary ammonium compound or the amine is adjusted to enable the resultant wastewater, which contains the organic sulfur compounds, and the quaternary ammonium compound or the amine, to contain nitrogen in an amount of 3 to 60 wt. % with respect to the total organic carbon (hereinafter referred to TOC) of the resultant wastewater.
According to another aspect of the present invention, there is provided an apparatus for treating wastewater containing organic sulfur compounds, which includes a pH adjustment tank for adjusting the pH value of the wastewater containing the organic sulfur compounds, a biological treatment tank for biologically treating the wastewater containing the organic sulfur compounds whose pH value has been adjusted in the pH adjustment tank, and a reservoir tank for storing wastewater containing a quaternary ammonium compound or wastewater containing an amine to be fed to the wastewater containing the organic sulfur compounds.
The present inventors have directed their attentions to the fact that the quaternary ammonium compound and the amine respectively contain nitrogen, and found the utilization of nitrogen contained in the quaternary ammonium or the amine as the source of nitrogen in the biological treatment tank for biologically treating the wastewater containing the organic sulfur compounds such as DMSO.
Nitrogen is contained in, for example, TMAH, in an amount of about 15.3 wt. %, and hence is utilized as the source of nitrogen in the course of biological treatment. This simultaneously achieves both reduction of the amount of at least one of the quaternary ammonium compound and the amine, and the reduction of the expenses for purchasing the source of nitrogen used for biological treatment of DMSO.
The method of the present invention, which includes treating the wastewater containing the organic sulfur compounds by adding the wastewater containing the quaternary ammonium compound or the wastewater containing the amine thereto, can utilizes the quaternary ammonium compound or the amine as the source of nitrogen for the biological treatment of the wastewater containing the organic sulfur compounds This achieves the simultaneous treatments of the wastewater containing the organic sulfur compounds, and the wastewater containing the quaternary ammonium compound or the wastewater containing the amine
Consequently) the above arrangement can omit ammonia conventionally used as the source of nitrogen, and hence advantageously reduce the expenses for purchasing ammonia.
In addition, the above arrangement can omit a reservoir tank for ammonia, and therefore produce an advantageous effect of reducing the space for the wastewater treatment facility.
Unlike the conventional methods, the utilization of the quaternary ammonium compound or the amine themselves as the source of nitrogen can produce an effect of reducing the cost of the waste treatment of TMAH and the like.
REFERENCES:
patent: 4300995 (1981-11-01), Liotta
patent: 4816139 (1989-03-01), Keyworth
Chifuku Hiroyuki
Muratani Toshiaki
Takamura Yoshio
Yano Takahiro
Barry Chester T.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Shinko Pantec Co. Ltd.
LandOfFree
Method and apparatus for treating wastewater containing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for treating wastewater containing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for treating wastewater containing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2557998