Liquid purification or separation – Automatic control
Reexamination Certificate
2002-10-23
2004-09-14
Prince, Fred G. (Department: 1724)
Liquid purification or separation
Automatic control
C210S151000, C210S605000, C210S618000, C210S622000, C210S903000, C210S908000
Reexamination Certificate
active
06790347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wastewater treatment apparatus and method using a biological filtering process, and more particularly, to a batch style wastewater treatment apparatus and method using a biological filtering process.
2. Description of the Related Art
As a biological wastewater treatment process, there are suspended growth methods, in which suspended microorganisms are utilized. According to this technique, wastewater and microorganisms are mixed in a reaction tank and air is supplied from the bottom of the reaction tank, thereby facilitating contact between wastewater and microorganisms. The microorganisms present in the reaction tank are capable of removing pollutants using oxygen contained in the air supplied. A sequencing batch reactor (SBR) technique is one of the suspended growth methods.
FIG. 1
is a schematic representation of a sequencing batch reactor (SBR), for illustrating a wastewater treatment method using a SBR technique.
Referring to
FIG. 1
, wastewater to be treated is filled in a reaction tank
1
up to an inflow level H
i
and the wastewater is aerated using an aerator
3
while stirring, to permit a reaction to occur. If the reaction is completed, sludge is precipitated, and supernatant liquid is decanted until the level of the reaction tank becomes an outflow level H
o
, and then discharged. Then, before new wastewater is introduced into the reaction tank, the operation of the sequencing batch reactor is idled for a predetermined time in order to adjust a cycling time.
The SBR technique is a modified sequencing activated sludge process, in which an unsteady environmental pressure is applied to microbe consortia in a reaction tank for microbial selection, for overcoming problems arising from a heavy impact load, which may be generated during a sequencing activated sludge process, sedimentation from a settling reservoir and an increase in the settlement site area due to a secondary settling reservoir.
The SBR technique has advantages in terms of excellent impact absorbing ability and excellent sludge sedimentation capability. However, the SBR technique has the following problems.
First, the SBR technique involves complicated steps, including, wastewater filling; reaction, settlement, discharging and idling, requiring a long cycling time.
Second, a decanter for discharging treated water is required, which is economically inefficient and poor in stability.
Third, flow control is difficult due to a long cycling time.
Fourth, an objectionable smell is generated and floating scum is generated, making liquid-solid separation difficult.
Fifth, sludge may be easily drained during discharge or decanting.
Another biological wastewater treatment process includes a sequencing biological filtering method.
FIG. 2
shows a conventional wastewater treatment apparatus using a sequencing biological filtering process.
Referring to
FIG. 2
, a denitrification reaction in wastewater will be described. First, wastewater to be treated is introduced into a lower chamber
7
through a wastewater supply means
2
of a denitrification tank
5
in an anoxic condition and is allowed to upwardly pass through a filter medium layer
9
. Here, nitrate nitrogen returned from a nitrification tank
11
through an internal returning means
23
is denitrified using organic matter in the wastewater and denitrifying microorganisms inhabiting in the filter medium layer
9
.
Then, the wastewater having passed through the denitrification tank
5
is introduced into a lower chamber
13
of the nitrification tank
11
through a first discharging means
10
. In this case, air is supplied to the nitrification tank
11
through a process air introducing means
17
. The wastewater introduced into the lower chamber
13
is allowed to upwardly pass though the filter medium layer
15
and organic nitrogen and ammonium nitrogen contained therein are nitrified by nitrifying microorganisms.
Finally, the treated wastewater having passed through the nitrification tank
11
is discharged to a separate storage tank
21
through a second discharging means
19
. The completely treated water is discharged from the storage tank
21
. During backwashing, the treated water is introduced to the lower chamber
7
of the denitrification tank
5
and the lower chamber
13
of the nitrification tank
11
through a backwash water introducing means
25
to wash the filter medium layers
9
and
15
. Then, the wastewater used in backwashing is discharged to the sedimentation tank or settling reservoir by a backwash water discharging means
27
.
According to the sequencing biological filtering method implemented in the above-described manner, the wastewater can be effectively treated in terms of cost and performance since both physical filtering by a filter medium layer and biodegradation by microorganisms inhabiting in the filter medium layer are used for wastewater treatment, unlike in a sequencing physical filtering method in which only physical filtering by a filter medium is used.
Yet the sequencing biological filtering method has several problems.
First, biological removal of phosphorus due to phosphorus release and excessive uptake mechanism of a microbe membrane is impossible.
Second, nitrogen and phosphorus cannot be simultaneously removed in a single reaction tank.
Third, for the foregoing reason, at least two reaction tanks are required for wastewater treatment.
Fourth, clogging may be liable to occur to a filter medium layer, making it difficult to be suitably applied to high-concentration wastewater.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an object of the present invention to provide a batch style wastewater treatment apparatus using a biological filtering process.
It is another object of the present invention to provide a wastewater treatment method using the wastewater treatment apparatus.
To accomplish the first object, there is provided a wastewater treatment apparatus according to a first embodiment of the present invention.
The wastewater treatment apparatus includes a bottom portion and a plate formed above and spaced apart from the bottom portion to form a lower chamber with the bottom portion, an outlet installed on the bottom portion for drawing off water and sludge in the lower chamber before backwashing, a filter medium layer supported to the upper portion of the plate by the plate, the upper layer of which forms a bottom portion of an upper chamber, a wastewater introducing means connected to the lower chamber, for introducing wastewater to be treated into the lower chamber, a process air introducing means for supplying process air to the filter medium layer formed over the plate, a plurality of aerators formed over and spaced apart a predetermined distance from the plate, and mounted in a plurality of air flow pipes led to the process air introducing means, a backwash air introducing means for supplying backwash air to the lower chamber during backwashing, a backwash water introducing means for supplying backwash water to the lower chamber during backwashing, a plurality of nozzles extending from the lower chamber to the filter medium layer through the plate, a treated water discharging means for discharging the treated water having passed through the filter medium layer, and a returned water introducing means for returning the treated water having passed through the filter medium layer to the lower chamber.
To accomplish the above object, the present invention also provides a modification of the wastewater treatment apparatus according to the first embodiment of the present invention. That is to say, a wastewater treatment apparatus according to a second embodiment of the present invention includes a bottom portion and a plate formed above and spaced apart from the bottom portion to form a lower chamber with the bottom portion, an outlet installed on the bottom portion for drawing off water and sludge in the lower chamber before backwashing, a filter medium layer supported to the upper portion of the
Aohh Gyung-Hae
Jeong Yong-Dae
Lee Jae-Jin
Park Jong-Bok
Burns Doane Swecker & Mathis L.L.P.
Prince Fred G.
Samsung Engineering Co., Ltd.
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