Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2000-08-15
2002-10-15
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S620000, C210S702000, C210S195200, C210S202000, C210S205000, C210S903000, C210S908000, C210S915000, C210S631000
Reexamination Certificate
active
06464874
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a waste water treatment method as well as a waste water treatment apparatus capable of simultaneously and effectively treating organic matters and fluorine contained in waste water with respect to organic matter-containing fluorine waste water discharged from semiconductor factories so that sludge produced from the waste water treatment apparatus is minimized.
Generally, in conventional fluorine-related waste water treatment, there have been provided no waste water treatment apparatuses in which both chemical sludge zone and biological sludge zone are present in one reaction tank.
Also, in conventional common waste water treatment, there have been provided no waste water treatment apparatuses in which three zones of (1) chemical sludge zone, (2) biological sludge zone and (3) aeration zone equipped with a membrane separation unit are built in one reaction tank.
Further, conventionally, there have been provided no waste water treatment apparatuses capable of treating fluorine and nitrate nitrogen contained in waste water simultaneously in one reaction tank.
Further, there have been provided neither fluorine waste water treatment methods nor waste water treatment apparatuses which treat nitrate nitrogen, a component other than fluorine, by recycling high-concentration biological sludge produced from other waste water treatment equipment so as to reduce waste materials.
Further, there have been provided neither waste water treatment methods nor waste water treatment apparatuses for transferring settlings derived from a reaction tank not to a settling tank but directly to a concentration tank, where a dehydrating process is performed so as to reduce waste materials.
(First Prior Art Example)
Now a first prior art example relating to waste water treatment of fluorine waste water is described in detail with reference to FIG.
16
. The waste water treatment apparatus of this first prior art example does not include any recycling process of sludge containing unreacted chemicals. The waste water treatment apparatus cannot remove any nitrate nitrogen contained in waste water.
In this waste water treatment apparatus, fluorine waste water is introduced to a raw water tank
101
. Fluorine waste water stored in the raw water tank
101
, after controlled in water quality and water quantity, is transferred to a slaked lime reaction tank
114
by a raw water tank pump
102
. In this slaked lime reaction tank
114
, calcium derived from added slaked lime and fluorine contained in the waste water react with each other, resulting in calcium fluoride
130
as a reaction product.
Unfortunately, although a rapid agitator
115
as an agitator means for accelerating the reaction is set at the slaked lime reaction tank
114
and serving for agitation therein, unreacted slaked lime flows out of the slaked lime reaction tank
114
so as to enter into a polychlorinated aluminum reaction tank
116
, because of the waste water retention time in the slaked lime reaction tank
114
being within 1 hour. At this polychlorinated aluminum reaction tank
116
, a rapid agitator
115
is set as well, so that granular calcium fluoride
130
as a reaction product generated through reaction in the slaked lime reaction tank
114
is flocculated by polychlorinated aluminum as an inorganic flocculant, thus forming flocs. Also, unreacted slaked lime is also flocculated by polychlorinated aluminum, forming flocs. These flocculated flocs of slaked lime are not in the form of calcium ions, utterly ineffective for fluorine treatment, hence a waste of chemicals and resulting in unreacted chemicals
129
.
Then, polymer flocculants are added in a polymer-flocculant flocculation tank
117
, so that the flocs of calcium fluoride
130
are formed into more stable, larger flocs. Meanwhile, unreacted flocs due to slaked lime, although ineffective for fluorine treatment, are also formed into more stable, larger flocs by the addition of the polymer flocculants.
The more stable, larger flocs of calcium fluoride
130
and the more stable, larger flocs of slaked lime flow into a settling tank
119
, settling there, and are collected together to the center of the bottom of the settling tank
119
by a settling-tank collector
120
. These scraped-up flocs result in sludge. That is, the quantity of this sludge is a total of sludge due to the calcium fluoride
130
, and unreacted slaked lime sludge or unreacted flocculant sludge, i.e., sludge due to the unreacted chemicals
129
, which has been a cause of high volume of waste materials.
Then, the sludge scraped up to the bottom center of the settling tank
119
flows into, and is concentrated by, a concentration tank
122
where a concentration-tank collector
123
is set. Thereafter, the sludge is transferred to filter presses
125
by filter press pumps
124
, and dehydrated there.
It is noted that two filter presses
125
are provided on account of high volume of sludge produced from this waste water treatment apparatus. Also, supernatant liquid of the concentration tank
122
is introduced to the raw water tank
101
through overflow piping (not shown).
Meanwhile, as a need of the times in these days, there are demands for a waste water treatment method and a waste water treatment apparatus which are small in the quantity of dehydrated cake after the dehydration, i.e., the quantity of sludge.
However, in the foregoing first prior art example, as described above, a large quantity of sludge would be involved because of the generation of the sludge of calcium fluoride and the sludge of unreacted slaked lime (unreacted chemicals). Varying depending on the conditions of factory waste water and the way of operation of waste water treatment equipment, sludge relating to unreacted chemicals generally amounts to a double or more of the quantity of the calcium fluoride sludge.
(Second Prior Art Example)
Next,
FIG. 17
shows a process flow for returning part of sludge derived from the settling tank
119
of the first prior art example to the raw water tank
101
by a sludge return pump
121
as a second prior art example. This second prior art example is also incapable of treating nitrate nitrogen, although capable of treating fluorine, in the waste water. However, in this second prior art example, since part of sludge derived from the settling tank
119
is returned to the raw water tank
101
, sludge containing unreacted chemicals is consumed by fluorine waste water. On this account, the second prior art example is smaller in sludge generation, as compared with the first prior art example.
(Third Prior Art Example)
Next,
FIG. 18
shows a process flow for returning part of sludge derived from the settling tank
119
of the first prior art example to the slaked lime reaction tank
114
by a sludge return pump
121
as a third prior art example. This third prior art example is also incapable of treating nitrate nitrogen, although capable of treating fluorine, in the waste water.
However, in this third prior art example, since part of sludge derived from the settling tank
119
is returned to the slaked lime reaction tank
114
, sludge containing unreacted chemicals is consumed by fluorine waste water in the slaked lime reaction tank
114
. On this account, the third prior art example is smaller in sludge generation, as compared with the first prior art example.
(Fourth Prior Art Example)
Next,
FIG. 19
shows a process flow of a fourth prior art example. The waste water treatment apparatus of this fourth prior art example is capable of treating fluorine and some amount of nitrate nitrogen. The reason why the apparatus can treat some amount of nitrate nitrogen is that denitrifying bacteria as anaerobic organic matters are generated in upper part of a return sludge reaction tank
143
and treat nitrate nitrogen. However, in order to securely treat the nitrate nitrogen contained in the fluorine waste water of general semiconductor factories, the amount of denitrifying bacteria cannot be said enough.
According to the process flow of this four
Chujou Kazumi
Sawai Norio
Yamasaki Kazuyuki
Nixon & Vanderhye P.C.
Prince Fred
Simmons David A.
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