Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2002-11-05
2004-11-30
Hopkins, Robert A. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S626000, C210S628000, C210S650000
Reexamination Certificate
active
06824684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment method and apparatus. For example, the present invention relates to an energy-saving wastewater treatment method and apparatus by which wastewater containing dimethylformamide, which is a toxic chemical substance, can be completely decomposed by using microorganisms. Further, the present invention relates to a wastewater treatment method and apparatus using a biological treatment tank having a submerged membrane and a foaming tank in combination.
Since the PRTR (Pollutant Release and Transfer Register) Law (the Law Concerning Reporting, etc. of Releases to the Environment of Specific Chemical Substances and Promoting Improvements in Their Management) came into operation in April 2001, much attention has been paid to the amount of releases of toxic chemical substances to environment.
Furthermore, today, when addressing to global environment is the most important issue, energy saving in wastewater treatment equipment is also an important theme.
Against such a backdrop, dimethylformamide used in a semiconductor factory has been designated as a toxic chemical substance (Class-1 designated chemical substance) by the PRTR Law, and thus thorough control and reduction of an amount of dimethylformamide release are being required. Wastewater containing dimethylformamide has been conventionally subjected to incineration due to its biological toxicity. In the case of incineration, however, a system with low environmental load cannot be provided since heavy oil or the like is used as an incineration fuel and wastewater needs to be transported to an incineration plant.
Furthermore, as a conventional technique, the technique described in Japanese Patent Laid-Open Publication No. 8-99092 has been proposed. This conventional technique relates to a wastewater treatment apparatus in which wastewater containing high-concentration organic matter is treated by increasing a microorganism concentration. That is, a vinylidene-chloride filler and a submerged membrane (referred to as a membrane filter) are installed in a catalytic oxidation tank as a bioreactor, and wastewater is treated by increasing the microorganism concentration. In this technique, however, no energy saving measure is taken. Specifically, no energy saving measure is taken for a blower, which has high power consumption as equipment. Furthermore, it is not disclosed in this technique that dimethylformamide as a toxic substance can be completely decomposed by a catalytic oxidation tank maintaining a high concentration of microorganisms.
Furthermore, as another conventional technique, the technique described in Japanese Patent Laid-Open Publication No. 9-70599 has been proposed. This conventional technique also relates to a wastewater treatment apparatus in which wastewater containing high-concentration organic matter is treated by increasing a microorganism concentration as in the case of the aforementioned apparatus described in Japanese Patent Laid-Open Publication No. 8-99092. In this conventional technique, a vinylidene-chloride filler and a submerged membrane (referred to as a membrane filter) are installed in a catalytic oxidation tank as a bioreactor, and wastewater is treated by increasing the microorganism concentration. However, no energy saving measure is taken in this technique, either. Specifically, no energy saving measure is taken for a blower, which has high power consumption as equipment. Furthermore, it is not disclosed that dimethylformamide as a toxic substance can be completely decomposed by a catalytic oxidation tank maintaining a high concentration of microorganisms.
Furthermore, a wastewater treatment apparatus shown in
FIG. 16
can be mentioned as another conventional technique. In this
FIG. 16
, reference numeral
101
denotes an aeration tank, in which microorganisms are propagated, and wastewater is introduced thereinto. In this aeration tank
101
, air supplied from a blower
102
is discharged from a diffusing pipe
103
to perform aeration by agitation in the aeration tank
101
, and thus oxygen in the air is supplied into the aeration tank
101
. Consequently, aerobic microorganisms are propagated in the aeration tank
101
to treat organic matter.
Subsequently, the wastewater biologically treated in this aeration tank
101
is introduced into a sedimentation tank
104
and separated into a solid and a liquid by sedimentation. The sedimentation tank
104
is equipped with a gathering device
105
and a sludge returning pump
106
for returning sludge sedimented in the sedimentation tank
104
to the aeration tank
101
. This sludge from the sludge returning pump
106
is partly dehydrated in a sludge treatment process. Electrical energy for operating the blower
102
is required in this wastewater treatment apparatus, but no rational energy saving method has been provided for this energy consumption.
Furthermore, a wastewater treatment apparatus shown in
FIG. 17
can be mentioned as another conventional technique. In
FIG. 17
, reference numeral
110
denotes a catalytic oxidation tank, in which microorganisms are propagated and a filler
109
is filled, and wastewater is introduced thereinto. In this catalytic oxidation tank
110
, air supplied from a blower
102
is discharged from a diffusing pipe
103
to perform contact aeration by agitation in the catalytic oxidation tank
110
, and thus oxygen from the air is supplied into the catalytic oxidation tank
110
. Consequently, organic matter is treated by propagating aerobic microorganisms in the catalytic oxidation tank
110
.
Subsequently, the wastewater biologically treated in this catalytic oxidation tank
110
is introduced into a sedimentation tank
104
and separated into a solid and a liquid by sedimentation. This sedimentation tank
104
is equipped with a gathering device
105
and a sludge returning pump
106
for returning sludge sedimented in the sedimentation tank
104
to the catalytic oxidation tank
110
. This sludge from the sludge returning pump
106
is partly dehydrated in a sludge treatment process. Electrical energy for operating the blower
102
is also required in this wastewater treatment apparatus, but no rational energy saving method has been provided for this energy consumption of the blower
102
.
Furthermore, as another conventional technique, a wastewater treatment apparatus shown in
FIG. 18
has been proposed. In
FIG. 18
, reference numeral
115
denotes a rotating disc tank, in which microorganisms are propagated, and wastewater is introduced thereinto. In this rotating disc tank
115
, a rotating disc
117
is driven by a motor
116
to be rotationally moved in water and air. Consequently, oxygen is supplied, and thus organic matter is treated by propagating aerobic microorganisms on a surface of the disc
117
.
Subsequently, the wastewater biologically treated in this rotating disc tank
115
is introduced into a sedimentation tank
104
and separated into a solid and a liquid by sedimentation. This sedimentation tank
104
is equipped with a gathering device
105
and a sludge returning pump
106
for returning sludge sedimented in the sedimentation tank
104
to the rotating disc tank
115
. This sludge from the sludge returning pump
106
is partly dehydrated in a sludge treatment process. Electrical energy for driving the rotating disc
117
is also required in this wastewater treatment apparatus, but there has been provided no wastewater treatment apparatus with which initial costs can be reduced and energy saving can be achieved.
Furthermore, examples of other conventional techniques include those described in Japanese Patent Laid-Open Publication Nos. 1-60371, 1-63372, 1-135595, 1-148398, 2-72864, 2-72865, 3-217298, 5-64796, 5-64797 and 5-269488.
These conventional techniques all relate to a method of decomposing dimethylformamide by specific microorganisms. However, it is difficult to manage wastewater treatment equipment so as to culture specific microorganisms in a biological treatment tank, in which other various bact
Chujo Kazumi
Yamasaki Kazuyuki
Hopkins Robert A.
Nixon & Vanderhye P.C.
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