Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-06-29
2001-07-17
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S610000, C210S614000, C210S615000, C210S617000, C210S631000, C210S652000, C210S195100, C210S195200, C210S205000, C210S900000, C210S903000, C210S908000, C210S915000
Reexamination Certificate
active
06261456
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a waste water treatment method and waste water treatment equipment for concurrently treating in one tank fluorine, nitrogen, organic matter and the like in waste water discharged from a semiconductor plant or a liquid crystal plant.
In a semiconductor plant or a liquid crystal plant, a large amount of organic matter such as IPA (isopropyl alcohol) and acetone as well as hydrofluoric acid including fluorine together with nitric acid and ammonia water including nitrogen. There is also used ammonium fluoride as a compound of fluorine and nitrogen.
From the point of view of the water pollution control law, it is required to treat the organic matter that increases the fluorine content, nitrogen content and the COD (Chemical Oxygen Demand) to a specified concentration in the case of a waste water that contains nitrogen and organic matter in addition to fluorine. Depending on the location of the plant, a severer additional standard is provided, and accordingly, a severer treatment is sometimes performed in conformity to the above standard and the standard owned by each individual enterprise.
In this case, defluorination is necessary for satisfying the regulation value of the fluorine concentration by the law, the additional standard of administration and the in-house standard of each enterprise. Further, denitrification is also necessary for satisfying the regulation value of the total nitrogen concentration in a waste water, the additional standard of administration and the in-house standard of each enterprise. The removal of the organic matter is necessary for reducing the COD that serves as a regulation value of waste water.
Conventionally, in a semiconductor plant, a mixed waste water having pH 2 to pH 3 containing nitrogen and organic matter in addition to fluorine has been treated as follows.
That is, as shown in
FIG. 11
, first, fluorine is chemically treated to be neutralized by chemicals such as slaked lime in a coagulo-sedimentation process
32
. After the fluorine is neutralized, then nitrogen is treated (nitrified) to nitrate nitrogen while biologically treating the organic matter by aerobic microorganisms in a nitrification tank
33
. Subsequently, an organic matter that serves as a hydrogen donor is excessively added from an organic matter tank
26
to a denitrification tank
29
so as to treat the nitrate nitrogen as nitrogen gas dissipating into the atmospheric air. Next, the organic matter excessively added to the denitrification tank
29
is biologically treated in a re-aeration tank
31
.
As defluorination equipment for removing fluorine in waste water, there is the one shown in FIG.
12
. In this defluorination equipment, a fluorine containing waste water is put through two calcium carbonate containing tanks
101
and
102
, and the water flowing from the calcium carbonate containing tank
102
is introduced into a circulation tank
103
. Then, the waste water inside the circulation tank
103
is introduced into a membrane filter unit
104
, which separates the waste water into a concentrated water including calcium carbonate crystals flowing out of the last calcium carbonate containing tank
102
and a permeated water. Subsequently, the thus-separated concentrated water is sent back to the circulation tank
103
. Part of the concentrated water is sent back to the first calcium carbonate containing tank
101
. The permeated water is discharged into a reservoir tank
105
.
According to the above defluorination equipment, the fluorine in the waste water reacts with the calcium carbonate located inside the calcium carbonate containing tanks
101
and
102
and becomes calcium fluoride. Then, after a lapse of a specified time of treatment, the calcium fluoride is extracted from the calcium carbonate containing tanks
101
and
102
. Thus, the fluorine is removed in the form of calcium fluoride.
As another defluorination equipment, there is calcium fluoride collecting equipment as shown in FIG.
13
. In this calcium fluoride collecting equipment, calcium carbonate located inside a calcium carbonate silo
107
is added to a fluorine containing solution located inside a calcium carbonate reaction tank
106
. Then, through a high-temperature aerating process (high-temperature decompression deaerating process) at a temperature of 50° C. to 100° C., calcium fluoride is collected. It is to be noted that the reference numeral
108
denotes a blower for the aeration and the reference numeral
109
denotes an air diffusion pipe.
The pieces of equipment shown in FIG.
12
and
FIG. 13
can also treat fluorine, but they cannot treat the organic matter.
In view of the above, there is waste water treatment equipment for treating a fluorine waste water containing organic matter, as shown in FIG.
14
. This waste water treatment equipment removes both fluorine and organic matter in the waste water by skillfully utilizing chemical reaction and biotic reaction with aerobic microorganisms by, for example, making calcium carbonate mineral
124
a
, which serves as a filler, flow strongly and weakly.
In
FIG. 14
are shown a first water tank
111
for executing a principal treatment, a second water tank (sedimentation tank)
112
, a third water tank (sludge concentration tank)
113
, a polychlorinated aluminum tank
114
, clarifiers
115
and
116
, blowers
117
through
119
, a line mixer
120
, a diffuser
121
and air diffusion pipes
122
and
123
. There are further shown calcium carbonate mineral pieces
124
a
through
124
c
, an inorganic sludge
125
and microorganic sludge
126
.
FIG. 15
shows another type of waste water treatment equipment. This waste water treatment equipment is to treat fluorine waste water containing organic matter by using calcium carbonate mineral. This waste water treatment equipment uses all the fillers in a fixed state. Therefore, the calcium fluoride generated as a consequence of the reaction of fluorine in the waste water with calcium remains between the calcium carbonate mineral pieces
146
in the fixed state and exists as a mass for a long time. Then, the mass gradually becomes larger to spread throughout the inside of the whole tank, as a consequence of which the treatment efficiency reduces. In
FIG. 15
are shown a first reaction regulation tank
131
, a second reaction regulation tank
132
, a third water tank
133
that serves as a reaction coagulation tank, a fourth water tank
134
that serves as a sedimentation tank, a fifth water tank
135
that serves as a sludge concentration tank, a filter press
136
, water sprinkling tanks
137
and
138
, blowers
139
through
141
, air diffusion pipes
142
and
143
and clarifiers
144
and
145
. There are further shown calcium carbonate mineral
146
, a charcoal
147
and plastic filler
148
.
The pieces of equipment shown in FIG.
14
and
FIG. 15
can treat fluorine and organic matter, but they cannot treat nitrogen.
In view of the above, there can be considered equipment as shown in
FIG. 16
besides the equipment shown in
FIG. 11
as equipment capable of treating fluorine, organic matter and nitrogen. This waste water treatment equipment is intended for treating fluorine waste water containing nitrogen and organic matter. This equipment treats the organic matter and fluorine in the waste water by means of a second water tank
72
. This tank
72
also nitrifies ammoniacal nitrogen and nitrite nitrogen to nitrate nitrogen. Subsequently, denitrification is executed by dissipating nitrogen into the atmospheric air in the form of nitrogen gas with the addition of excessive amount of adding organic matter (methanol or the like) that serves as a hydrogen donor by means of an organic matter tank pump
87
while introducing the waste water into a denitrification tank
89
. Subsequently, the organic matter excessively added to the denitrification tank
89
is biologically treated by a re-aeration tank
91
.
As prior art treatment equipment for treating nitrogen and fluorine containing waste water, there is the one disclosed in the prior
Sakata Kazuyuki
Yamasaki Kazuyuki
Nixon & Vanderhye
Prince Fred
Sharp Kabushiki Kaisha
Simmons David A.
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