1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
WATER TREATMENT APPARATUS AND WATER TREATMENT METHOD
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
5 Field
[0001] The present invention relates to a biological
water treatment apparatus and to a biological water
treatment method for purifying urban sewage, organic
wastewater, and nitrogen-containing wastewater using a
10 biological treatment.
Background
[0002] One typical method of treatment of urban sewage,
organic wastewater, and nitrogen-containing wastewater is
15 an activated sludge process. An activated sludge process
is a process in which a microorganism group (activated
sludge) having a purification effect is stored in a
bioreactor tank, and aeration is provided while this and
wastewater are mixed together in contact with each other to
20 oxidize and decompose pollutants in the wastewater. To
achieve a sufficient degree of purification of these
pollutants, an appropriate amount of air needs to be
supplied to the bioreactor tank. Such air supply to a
bioreactor tank is known as aeration.
25 Energy required for aeration accounts for a
significant portion of the energy in water treatment that
uses an activated sludge process. To increase energy
efficiency in water treatment, a method has been proposed
for a conventional water treatment system, in which the
30 overall aeration air volume is reduced by improving
followability of the ammonia-degrading potential to a
variation in the ammonia nitrogen concentration of the
aerobic tank. Specifically, a method has been proposed in
3
which a first ammonia meter for measuring the ammonia
nitrogen concentration of the raw water, an aeration air
volume computation unit that calculates a target
operational volume, and an aeration air volume control unit
that controls the aeration air volume based 5 on the target
operational volume are included, and the aeration air
volume computation unit computes an aeration air volume
using a feedforward control system that operates based on
the raw water ammonia nitrogen concentration and a feedback
10 control system that provides feedback control based on the
aerobic tank ammonia nitrogen concentration (see, e.g.,
Patent Literature 1).
Citation List
15 Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. 2012-66231
Summary
20 Technical Problem
[0004] A conventional water treatment apparatus such as
one described above is required to further reduce the
amount of energy required for aeration to increase energy
efficiency in water treatment. For example, the
25 conventional water treatment apparatus aerates the aerobic
tank uniformly over the entire volume thereof at an
aeration air volume computed based on the ammonia nitrogen
concentration in the raw water or on the ammonia nitrogen
concentration in the aerobic tank. The aerobic tank is
30 often aerated uniformly over the entire volume thereof for
simplicity of apparatus design in view of a generally
complex configuration of a water treatment apparatus.
However, the raw water flowed into the aerobic tank is
4
sequentially treated over time in the downstream direction
in the aerobic tank. This results in different reaction
rates in the biological reaction occurring in the
bioreactor tank depending on positions in the aerobic tank,
thereby causing the required aeration 5 air volume to also
differ depending on the position in the aerobic tank. Thus,
the conventional water treatment apparatus fails to supply
air at an appropriate aeration air volume depending on the
position in the aerobic tank. A further reduction in the
10 amount of energy required for aeration has then been
demanded by efficient adjustment of the aeration air volume.
[0005] The present invention has been made in view of
the above-described situation, and it is an object of the
present invention to provide a biological water treatment
15 apparatus and a biological water treatment method that
enable a further reduction in the amount of energy required
for aeration.
Solution to Problem
20 [0006] A water treatment apparatus according to the
present invention includes: a first aeration unit and a
second aeration unit to each aerate the treatment target
water with the air, in a bioreactor tank that aerates, with
air, treatment target water that flows into the bioreactor
25 tank through an inlet, performs biological reaction
treatment, and drains the treatment target water out of the
bioreactor tank through a drain port; and an aeration rate
calculation unit to control an aeration rate of the first
aeration unit and an aeration rate of the second aeration
30 unit, wherein the first aeration unit is disposed at a
position less distant from the inlet than the second
aeration unit in the bioreactor tank, and the aeration rate
calculation unit provides control to produce different
5
aeration rates for the first aeration unit and the second
aeration unit.
[0007] A water treatment method according to the present
invention includes: a step of measuring an influent load of
treatment target water that flows into a 5 bioreactor tank; a
step of measuring an effluent pollutant concentration of
the treatment target water that flows out of the bioreactor
tank; a step of calculating, based on the influent load, an
inlet-side controlled aeration rate of each of a plurality
10 of aeration units to produce different inlet-side
controlled aeration rates for the respective aeration units,
and a step of calculating, based on the effluent pollutant
concentration, an outlet-side controlled aeration rates of
each of the aeration units to produce different outlet-side
15 controlled aeration rates for the respective aeration units,
the aeration units being disposed along a direction of flow
of the treatment target water in the bioreactor tank; a
step of determining an aeration rate for each corresponding
one of the aeration units by adding together the inlet-side
20 controlled aeration rate and the outlet-side controlled
aeration rate; and a step in which each of the aeration
units supplied with air that corresponds to a corresponding
one of the aeration rates aerates the treatment target
water with the air.
25
Advantageous Effects of Invention
[0008] The present invention enables a biological water
treatment apparatus and a water treatment method to be
provided that enable a further reduction in the amount of
30 energy required for aeration.
[0009] In addition, a water treatment method according
to the present invention enables the pollutant
concentration of effluent water that is to be drained to be
6
finely controlled, and also enables the treatment water
quality to be efficiently controlled using a proper
aeration rate, enables an appropriate aeration rate to be
set depending on the position of each aeration unit in the
reactor tank, enables water quality 5 to be efficiently
controlled, enables an appropriate amount of air to be
supplied from each aeration unit of the reactor tank even
under variation in the influent load of treatment target
water flowing in, and thus enables the pollutant
10 concentration of effluent water that is to be drained to be
brought closer to a target value.
Brief Description of Drawings
[0010] FIG. 1 is a configuration diagram of a water
15 treatment apparatus according to a first embodiment of the
present invention.
FIG. 2 is a configuration diagram of a water treatment
apparatus according to a second embodiment of the present
invention.
20 FIG. 3 is a configuration diagram of the aeration rate
calculation unit according to the second embodiment of the
present invention.
FIG. 4 is a configuration diagram of a water treatment
apparatus according to a third embodiment of the present
25 invention.
FIG. 5 is a configuration diagram of the aeration rate
calculation unit according to the third embodiment of the
present invention.
30 Description of Embodiments
[0011] First Embodiment.
A water treatment apparatus according to a first
embodiment of the present invention will be described with
7
reference to FIG. 1. FIG. 1 is a configuration diagram of
a biological water treatment apparatus.
[0012] Referring to FIG. 1, treatment target water
flowed in through a pipe 103 is purified by biological
reaction in a bioreactor tank 1 storing 5 activated sludge,
and purification-treated effluent water is drained through
a pipe 106. The activated sludge contained in the effluent
water drained out of the bioreactor tank 1 through the pipe
106 is let to settle in a settling tank 2. The supernatant
10 water obtained after the settling treatment is drained
through a pipe 108. In addition, the activated sludge
separated by the settling treatment is returned to the
bioreactor tank 1 through a pipe d, while the residue is
drained out to the outside world through a pipe e.
15 The bioreactor tank 1 includes an anaerobic zone 101,
where no aeration is performed, upstream of the bioreactor
tank 1. Downstream of the anaerobic zone, an aerobic zone
102 including aeration units disposed therein is provided,
where air supplied from the aeration units and the
20 activated sludge are mixed together. The water treatment
apparatus according to the first embodiment includes a
partition plate 100 between the anaerobic zone 101 and the
aerobic zone 102. Use of the partition plate 100 allows
air from the aeration units 30 to be reliably prevented
25 from leaking out into the anaerobic zone 101. It is
therefore likely that the anaerobic nature of the anaerobic
zone 101 is maintained at a high level. The configuration
of the present invention is not limited to the
configuration of this example, and the partition plate 100
30 may be omitted. Alternatively, separation may be achieved
by use of separate water tanks or circuit structures
instead of the use of the partition plate 100.
The water treatment apparatus according to the first
8
embodiment includes the multiple aeration units 30 (i.e., a
first aeration unit 31, a second aeration unit 32, and a
third aeration unit 33) along the flow direction of the
treatment target water in the aerobic zone 102 in the
bioreactor tank 1. The first aeration unit 5 is disposed at
a position less distant from the inlet than the second
aeration unit in the bioreactor tank 1, while the third
aeration unit is disposed at a position more distant from
the inlet than the second aeration unit in the bioreactor
10 tank 1.
The water treatment apparatus according to the first
embodiment also includes aeration rate calculation units 70
(i.e., a first aeration rate calculation unit 71, a second
aeration rate calculation unit 72, and a third aeration
15 rate calculation unit 73), which individually control
aeration rates of the respective aeration units, and air
supply units 40 (i.e., a first air supply unit 41, a second
air supply unit 42, and a third air supply unit 43), which
supply air to the respective aeration units 30 at the
20 respective aeration rates calculated by the respective
aeration rate calculation units 70.
[0013] An influent load measurement unit 5, which
measures an influent load of the treatment target water
flowing into the bioreactor tank 1, is fitted to the pipe
25 103, or installed to a water conduit other than the pipe,
to measure the influent load of the treatment target water
before the treatment target water flows into the bioreactor
tank 1. The influent load measurement unit 5 includes at
least one or more measurement devices selected from a
30 flowmeter and a pollutant concentration meter (i.e., an
ammonia nitrogen concentration meter, a total nitrogen
concentration meter, a biochemical oxygen demand (BOD)
meter, a chemical oxygen demand (COD) meter, etc.). In a
9
case in which a flowmeter and a pollutant concentration
meter are both used, the influent load may be calculated as
a product of the flow rate of the treatment target water
flowing into the bioreactor tank 1 and an influent
pollutant concentration. Moreover, in 5 a treatment plant
having no flowmeter, the opening degree of a gate of an
inlet conduit or the like may be used as an alternative to
a flowmeter. Furthermore, a water temperature meter may
also be installed, in addition to a flowmeter and/or a
10 pollutant concentration meter, to take into account
seasonal or other factors. The first embodiment assumes
that the influent load is calculated as a product of the
flow rate of the treatment target water flowing into the
bioreactor tank 1 and the influent pollutant concentration.
15 The first aeration rate calculation unit 71, the
second aeration rate calculation unit 72, and the third
aeration rate calculation unit 73 calculate the respective
aeration rates of air to be supplied to the respective
aeration units based on a value of the influent load input
20 via a signal line 5a, and send the respective aeration
rates calculated, to the first air supply unit 41, to the
second air supply unit 42, and to the third air supply unit
43, respectively, via signal lines 71a, 72a, and 73a. The
first air supply unit 41, the second air supply unit 42,
25 and the third air supply unit 43 supply air, according to
the respective aeration rates transmitted, to the first
aeration unit 31, to the second aeration unit 32, and to
the third aeration unit 33 in the bioreactor tank 1 through
pipes 41a, 42a, and 43a. In the bioreactor tank 1, the
30 treatment target water flowed in through the pipe 103 is
mixed and stirred with the activated sludge and with air
supplied from the first aeration unit 31, from the second
aeration unit 32, and from the third aeration unit 33 to
10
biologically oxidize and decompose pollution matter in the
water for purification.
[0014] A water treatment method according to the first
embodiment will next be described.
The influent load of the treatment 5 target water
flowing into the bioreactor tank 1 is measured by the
influent load measurement unit 5, and the result is fed to
the first aeration rate calculation unit 71, to the second
aeration rate calculation unit 72, and to the third
10 aeration rate calculation unit 73 via the signal line 5a.
The first aeration rate calculation unit 71, the second
aeration rate calculation unit 72, and the third aeration
rate calculation unit 73 calculate, based on the influent
load, setting values of the aeration rate of air to be
15 supplied from the first aeration unit 31, from the second
aeration unit 32, and from the third aeration unit 33.
Each of the aeration rate calculation units stores a
coefficient predetermined for the corresponding aeration
unit connected to that aeration rate calculation unit, and
20 calculates the sum of (a) and (b) described below based on
the influent load fed via the signal line 5a.
(a) A value calculated by multiplication of the
influent load of the treatment target water flowing into
the bioreactor tank 1 measured by the influent load
25 measurement unit 5, by a first coefficient predetermined
for that aeration unit
(b) Aeration unit constant
Feeding of the setting values of the aeration rate
calculated as described above to the respective aeration
30 units connected to the respective aeration rate calculation
units, causes air to be supplied at the respective aeration
rates from the respective aeration units to the bioreactor
tank.
11
[0015] In this regard, the first coefficient is an
optimum value obtained from simulation or from an analysis
result of actual plant data to enable an optimum aeration
rate to be obtained to let the aeration rate to quickly
follow a variation in the influent load 5 flowing into the
bioreactor tank 1. Thus, different optimum values are set
depending on the positions of, or on the number of, the
aeration units.
For example, in a case in which the influent load
10 measurement unit 5 includes a flowmeter and an ammonia
nitrogen concentration meter, the aeration rate calculation
unit 71 calculates a setting value G1 [Nm3/hr] of the
aeration rate of air to be supplied from the first aeration
unit 31 using Equation (1).
15 [0016]
[Formula 1]
... (1)
[0017] Here, SIN is an influent pollutant concentration,
and is an ammonia nitrogen concentration measurement value
[unit: mg/L] of the treatment target water flowing into the
bioreactor tank. QIN is a flow rate measurement value
20 [unit: m3/hr] of the treatment target water flowing into
the bioreactor tank. The factor k11 is the first
coefficient for the first aeration unit 31, and k13 is the
aeration unit constant for the aeration rate calculation
unit 71.
25 Similarly, the aeration rate calculation units 72 and
73 calculate respective setting values G2 and G3 [Nm3/hr],
the respective aeration rates of the second aeration unit
32 and 33 using Equations (2) and (3).
[0018]
[Formula 2]
12
... (2)
[0019]
[Formula 3]
... (3)
[0020] Here, k21 is the first coefficient for the second
aeration unit 32, and k23 is the aeration unit constant for
the second aeration unit 32. The factor k31 is the first
coefficient for the third aeration unit 5 33, and k33 is the
aeration unit constant for the third aeration unit 33.
In Equations (1), (2), and (3), the first coefficient
for each of the aeration units is, as described above, an
optimum value obtained from simulation or from an analysis
10 result of actual plant data to enable an optimum amount of
air supply to be obtained to let the aeration rate to
quickly follow a variation in the influent load flowing
into the bioreactor tank 1. Moreover, the values are set
to allow the first coefficients k11, k21, and k31 to
15 satisfy a relationship of k11≥k21≥k31. In addition, the
aeration unit constants k13, k23, and k33 are each a
constant to be set to provide fine adjustment of the
aeration rate of each aeration unit, and for example, are
each set to the minimum value of the aeration rate for that
20 aeration unit.
This results in a higher aeration rate of aeration of
an aeration unit closer to the inlet of the bioreactor tank
1, following a variation in the influent load of the
treatment target water flowing into the bioreactor tank 1.
25 The setting values G1, G2, and G3 of the aeration rate
calculated using Equations (1), (2), and (3) are
respectively fed to the first air supply unit 41, to the
second air supply unit 42, and to the third air supply unit
13
43 via the signal lines 71a, 72a, and 73a.
The first air supply unit 41, the second air supply
unit 42, and the third air supply unit 43 supply air at the
respective set rates into the bioreactor tank 1
respectively via the pipes 41a, 5 42a, and 43a and
respectively via the first aeration unit 31, the second
aeration unit 32, and the third aeration unit 33.
[0021] Note that the foregoing description discloses
that three aeration units are installed. Because two or
10 more aeration units are desirably installed in the aerobic
zone 102 in the bioreactor tank 1 along the flow direction
of the treatment target water, a plurality of aeration
units are installed. The aeration rate calculation unit is
capable of calculating, for the multiple aeration units, an
15 optimum aeration rate of air to be supplied from each of
the aeration units using Equation (4).
[0022]
[Formula 4]
... (4)
[0023] Here, Gi is a setting value of the aeration rate
for each of the aeration units. The parameter i=1, ∙∙∙, n
20 represents the number of each aeration unit, and represents
the order of the aeration unit along the flow direction of
the treatment target water in the bioreactor tank. The
number n is a natural number greater than or equal to 2.
SIN represents an ammonia nitrogen concentration
25 measurement value [unit: mg/L] of the treatment target
water flowing into the bioreactor tank. QIN represents a
flow rate measurement value [unit: m3/hr]. The factor ki1
represents the first coefficient for that aeration unit,
and ki3 represents the aeration unit constant for that
30 aeration unit.
14
Note that Equation (4) provides calculation of the
influent load of the treatment target water by a product of
the flow rate of the treatment target water flowing into
the bioreactor tank 1 and the influent pollutant
concentration. However, in a case in which 5 the flow rate
of the treatment target water flowing into the bioreactor
tank 1 is only measured, setting of, as the value of (a), a
value calculated by multiplication of the flow rate of the
treatment target water flowing into the bioreactor tank 1
10 by the first coefficient predetermined for that aeration
unit, enables the setting value of the aeration rate to be
calculated using Equation (4). Similarly, in a case in
which the ammonia nitrogen concentration of the treatment
target water flowing into the bioreactor tank 1 is only
15 measured, setting of, as the value of (a), a value
calculated by multiplication of the ammonia nitrogen
concentration of the treatment target water flowing into
the bioreactor tank 1 by the first coefficient
predetermined for that aeration unit, enables the setting
20 value of the aeration rate to be calculated using Equation
(4).
[0024] In addition, although FIG. 1 illustrates the
influent load measurement unit 5 as being connected to the
pipe 103 provided on the inlet side of the bioreactor tank
25 1, the influent load measurement unit 5 may also be fitted
at a fitting point 104 or at a fitting point 105 in the
bioreactor tank 1. The fitting point 104 is positioned on
the inlet side inside the bioreactor tank 1, in the
anaerobic zone. The fitting point 105 is positioned at a
30 position where the first aeration unit 31, i.e., the one
closest to the inlet in the bioreactor tank 1, is disposed,
that is, at a position on the entry side of the aerobic
zone.
15
The measurement point of the influent load measurement
unit 5 can be changed the fitting point to one of the pipe
103, the fitting point 104, and the fitting point 105
depending on the control purpose. In a treatment plant
subjected to an influent load that varies 5 significantly,
connection of the influent load measurement unit 5 to the
pipe 103 enables a variation in the influent load to be
promptly detected. This improves followability of the
aeration rate to the variation in the influent load, and
10 can thus stabilize effluent water quality. Meanwhile, use
of the fitting point 105 allows measurement of an actual
influent load flowing into the aerobic zone, thereby
enabling the aeration rate necessary for the treatment to
be accurately computed, and enabling the total aeration
15 rate to be thus minimized.
[0025] In addition to the treatment target water flowed
in through the pipe 103, the bioreactor tank 1 also
receives activated sludge that has returned from the
settling tank 2 through the pipe d. When a need exists to
20 take into account the effect of the returned activated
sludge in addition to the effect of a variation in the
influent load of the treatment target water, the influent
load measurement unit 5 will be fitted at the fitting point
104 near the entry of the bioreactor tank 1. This will
25 achieve measurement of the actual influent load flowing
into the bioreactor tank 1, thereby enabling a variation in
the influent load to also be quickly responded to while
taking into account the effect of the returned sludge.
This can provide a proper air supply, and can further
30 reduce the aeration rate as compared to when measurement is
performed at the pipe 103.
Note that when the influent load measurement unit 5 is
installed at the fitting point 104, it leads to calculating
16
the aeration rate of each aeration unit based on the
influent load of the treatment target water before passage
through the anaerobic zone, which produces a time lag in
controlling of aeration rate. Such time lag can be
eliminated for further reduction in the 5 aeration rate by
installing the influent load measurement unit 5 at the
fitting point 105, which is positioned at the entry of the
aerobic zone where the activated sludge is about to be
mixed with air in the bioreactor tank 1.
10 [0026] Moreover, FIG. 1 illustrates a case in which the
anaerobic zone and the aerobic zone, in which activated
sludge and air are mixed together, are provided in a single
bioreactor tank. However, a similar advantage will also be
achieved in a configuration in which the anaerobic zone and
15 the aerobic zone are formed in different water tanks, that
is, separated in the form of tanks which are an anaerobic
tank and an aerobic tank. In this case, multiple aeration
units are installed along the flow direction of the
treatment target water in the aerobic tank, and the
20 aeration rate calculation units and the air supply units
that supply air to the respective aeration units control
the aeration rates of the respective aeration units
individually. Specifically, a higher aeration rate is used
for an aeration unit closer to the inlet and a lower
25 aeration rate is set for the supply from an aeration unit
closer to the outlet in the bioreactor tank, based on the
influent load of the treatment target water.
Although FIG. 1 illustrates a configuration in which
only the anaerobic zone precedes the aerobic zone, the
30 configuration may also include two or more zones involving
no aeration being provided upstream of the aerobic zone, a
typical example of which is an anaerobic-anoxic-oxic method
(A2O method), which is a biological treatment for
17
simultaneously removing phosphorus and nitrogen. In this
case, a similar advantage will be achieved by positioning
the fitting point 104 on the inlet side inside the
bioreactor tank 1 and positioning the fitting point 105 on
the entry side of 5 the aerobic zone.
[0027] The water treatment apparatus and the water
treatment method according to the first embodiment each set
the amount of air to be supplied into the bioreactor tank 1
based on the influent load of the treatment target water
10 flowing or flowed into the bioreactor tank 1, thereby
improving followability of the aeration rate to an influent
load variation. This enables the aeration rate to be
promptly controlled based on the influent load variation,
and can thus reduce or prevent a variation in effluent
15 water quality. Setting a higher aeration rate for an
aeration unit closer to the inlet of the bioreactor tank 1,
can reduce or prevent a variation in water quality in an
upstream portion of the bioreactor tank, which is more
susceptible to a variation in the influent load. Moreover,
20 measurement of the influent load at a fitting point inside
the bioreactor tank allows the actual influent load to be
measured, thereby enabling the aeration rate necessary for
the treatment to be suitably calculated, and enabling the
total aeration rate to be thus reduced.
25 [0028] Second Embodiment.
A biological water treatment apparatus according to a
second embodiment of the present invention will now be
described with reference to FIG. 2. FIG. 2 is a
configuration diagram of a biological water treatment
30 apparatus. In the second embodiment, as a measurement unit
for performing a measurement on the treatment target water,
an effluent pollutant concentration measurement unit is
installed on the outlet side instead of the influent load
18
measurement unit installed on the inlet side, of the water
treatment apparatus according to the first embodiment.
Note that, in the second embodiment, elements identical or
equivalent to the corresponding elements in the first
embodiment are designated by like reference 5 characters, and
duplicate description thereof will be omitted.
An effluent pollutant concentration measurement unit 6,
which measures the pollutant concentration of effluent
water that is to be drained out of the bioreactor tank 1,
10 is fitted to the pipe 106 on the outlet side outside the
bioreactor tank, or installed to a water conduit other than
the pipe, to measure the effluent pollutant concentration
of the treatment target water flowed out of the bioreactor
tank. The effluent pollutant concentration measurement
15 unit 6 includes an instrument for measuring the pollutant
that is a target of water quality management in the water
treatment. Examples of the instrument include an ammonia
nitrogen concentration meter, a total nitrogen
concentration meter, a BOD meter, and a COD meter. In
20 addition, a water temperature meter may also be installed,
in addition to the pollutant concentration meter, to take
into account seasonal or other factors. The value of the
effluent pollutant concentration is sent to the first
aeration rate calculation unit 71, to the second aeration
25 rate calculation unit 72, and to the third aeration rate
calculation unit 73 via a signal line 6a.
A fitting point 107 is a possible fitting point of the
effluent pollutant concentration measurement unit 6,
alternative to the pipe 106, and is positioned on the
30 outlet side inside the bioreactor tank. The effluent
pollutant concentration measurement unit 6 may also be
fitted at the fitting point 107.
[0029] A water treatment method according to the second
19
embodiment will next be described.
FIG. 3 is a configuration diagram of the aeration rate
calculation unit 71 according to the second embodiment.
The aeration rate calculation unit 71 includes an effluent
pollutant concentration difference calculation 5 unit 8, a
proportional term calculation unit 9, an integral term
calculation unit 10, a derivative term calculation unit 11,
a target aeration rate calculation unit 12, and signal
lines connecting these calculation units to one another.
10 Referring to FIG. 3, a method for calculating an aeration
rate will be described that is performed in the first
aeration rate calculation unit 71, in the second aeration
rate calculation unit 72, and in the third aeration rate
calculation unit 73. Note that although FIG. 3 illustrates
15 the aeration rate calculation unit 71, the aeration rate
calculation units 72 and 73 are similarly configured.
The effluent pollutant concentration difference
calculation unit 8 calculates an effluent pollutant
concentration difference based on the effluent pollutant
20 concentration sent via the signal line 6a and on a
pollutant concentration target value of the effluent water.
On the basis of the effluent pollutant concentration
difference sent from the effluent pollutant concentration
difference calculation unit 8 via signal lines 8a, 8b, and
25 8c, the proportional term calculation unit 9 calculates an
amount GP of proportional control (P-control), the integral
term calculation unit 10 calculates an amount GI of
integral control (I-control), and the derivative term
calculation unit 11 calculates an amount GD of derivative
30 control (D-control). The values GP, GI, and GD are
respectively calculated using Equation (5-1), Equation (5-
2), and Equation (5-3).
[0030]
20
[Formula 5-1]
... (5-1)
[0031]
[Formula 5-2]
... (5-2)
[0032]
[Formula 5-3]
... (5-3)
[0033] Here, SOUT is the effluent pollutant concentration,
and is an ammonia nitrogen concentration measurement value
[unit: mg/L] of the treatment target water 5 flowed out of
the bioreactor tank. S0 is the pollutant concentration
target value of the effluent water, and is a target value
[unit: mg/L] of the ammonia nitrogen concentration of the
treatment target water flowed out of the bioreactor tank.
10 KP is the proportional gain, TI is the integration time,
and TD is the derivative time.
The target aeration rate calculation unit 12
calculates the setting value of the aeration rate of air to
be supplied to the first aeration unit 31 based on the
15 amount of proportional control sent via a signal line 9a,
on the amount of integral control sent via a signal line
10a, and on the amount of derivative control sent via a
signal line 11a. The setting value of the aeration rate
calculated is sent to the air supply unit 41 via the signal
20 line 71a.
Each of the aeration rate calculation units stores a
second coefficient and the aeration unit constant ki3
predetermined for the aeration unit connected to that
aeration rate calculation unit, and the target aeration
21
rate calculation unit 12 calculates the sum of (a) and (b)
described below based on the values GP, GI, and GD fed via
the signal lines 9a, 10a, and 11a. The aeration rate is
calculated using Equation (6).
(a) A value calculated by multiplication 5 of a sum
(GP+GI+GD) by the second coefficient predetermined for that
aeration unit
(b) Aeration unit constant
[0034]
[Formula 6]
... (6)
10 [0035] Here, Gi is a setting value of the aeration rate
of air to be supplied to each of the aeration units. The
parameter i=1, ∙∙∙, n represents the number of each
aeration unit, and represents the order of the aeration
unit along the flow direction of the treatment target water
15 in the bioreactor tank. The number n is a natural number
greater than or equal to 2. GP, GI, and GD are,
respectively, the amount of proportional control, the
amount of integral control, and the amount of derivative
control, each calculated from the effluent pollutant
20 concentration difference based on the effluent pollutant
concentration measured and on the pollutant concentration
target value of the effluent water. The factor ki2 is the
second coefficient for that aeration unit. And ki3 is the
aeration unit constant for the first aeration unit 31.
25 For example, the aeration rate calculation unit 71
calculates the setting value G1 [Nm3/hr] of the aeration
rate of air to be supplied to the first aeration unit 31
using Equation (7).
[0036]
[Formula 7]
22
... (7)
[0037] Here, k12 is the second coefficient for the first
aeration unit 31, and k13 is the aeration unit constant for
the first aeration unit 31.
Similarly, the aeration rate calculation units 72 and
73 calculate the respective setting 5 values G2 and G3
[Nm3/hr] of the aeration rate of the second aeration unit
32 and 33 respectively using Equations (8) and (9).
[0038]
[Formula 8]
... (8)
[0039]
[Formula 9]
... (9)
10 [0040] Here, k22 is the second coefficient for the
second aeration unit 32, and k23 is the aeration unit
constant for the second aeration unit 32; and k32 is the
second coefficient for the third aeration unit 33, and k33
is the aeration unit constant for the third aeration unit
15 33.
In Equations (7), (8), and (9), the coefficient
predetermined for each of the aeration units is an optimum
value obtained from simulation or from an analysis result
of actual plant data to enable an optimum aeration rate to
20 be obtained to allow the pollutant concentration of the
effluent water to be brought even closer to a predetermined
target value of the pollutant concentration, and moreover,
the values are set to allow the second coefficients k12, k22,
and k32 to satisfy a relationship of k12≤k22≤k32. The
25 aeration unit constants k13, k23, and k33 are each a constant
23
to be set to provide fine adjustment of the aeration rate
of each aeration unit, and for example, are each set to the
minimum value of the aeration rate for that aeration unit.
[0041] Thus, the aeration rates are calculated to
produce a greater amount of feedback control 5 of aeration
rate for an aeration unit closer to the outlet in the
bioreactor tank.
The setting values G1, G2, and G3 of the aeration rate
for the respective aeration units calculated as described
10 above are respectively sent to the first air supply unit 41,
to the second air supply unit 42, and to the third air
supply unit 43 via the signal lines 71a, 72a, and 73a.
Next, the first air supply unit 41, the second air
supply unit 42, and the third air supply unit 43 supply air
15 to the bioreactor tank 1 at the respective aeration rates
that have been set respectively via the pipes 41a, 42a, and
43a and respectively via the first aeration unit 31, the
second aeration unit 32, and the third aeration unit 33.
Note that the foregoing description assumes that three
20 aeration units are installed. Because two or more aeration
units are desirably installed in the aerobic zone 102 in
the bioreactor tank 1 along the flow direction of the
treatment target water, a plurality of aeration units are
installed. The aeration rate calculation unit is capable
25 of calculating, for the multiple aeration units, an optimum
aeration rate of air to be supplied from each of the
aeration units using Equation (6).
[0042] Although FIG. 2 illustrates the effluent
pollutant concentration measurement unit 6 as being
30 connected to the pipe 106 provided on the outlet side
outside the bioreactor tank, the measurement point of the
effluent pollutant concentration measurement unit 6 can be
changed the fitting point to one of the pipe 106 and the
24
fitting point 107 positioned on the outlet side inside the
bioreactor tank depending on the control purpose.
Use of a point in the pipe 106 allows water quality of the
effluent water flowed out of the bioreactor tank to be
directly measured, thereby providing 5 computation of the
aeration rate necessary to control the effluent water
quality to the target value. When emphasis is placed on a
reduction in the aeration rate to avoid excessive aeration
that will provide a higher level of water quality than
10 required, the effluent pollutant concentration measurement
unit 6 can be installed to the pipe 106.
Meanwhile, when a need exists for reliably preventing
the water quality of the effluent water from exceeding a
management value, the effluent pollutant concentration
15 measurement unit 6 is installed at the fitting point 107,
upstream of the outlet at the downstream end in the
bioreactor tank 1. Use of the fitting point 107 allows
water treatment to be continued until the treatment target
water completely flows out even after the effluent
20 pollutant concentration measurement unit 6 measures water
quality, thereby enabling the effluent water quality to be
reliably controlled to a level of, or less than, the
management value.
This means that the ammonia concentration is
25 accordingly reduced to the target value before complete
termination of the biological treatment reaction in the
reactor tank, thereby making it likely that the total
aeration rate will be higher than when the effluent
pollutant concentration measurement unit 6 is installed to
30 the pipe 106. This enables the water quality of the
eventual effluent water to be kept at an appropriate level
owing to treatment in a zone downstream of the fitting
point 107 even when the pollutant concentration measured by
25
the effluent pollutant concentration measurement unit 6
reaches or exceeds the target value due to delay in the
controlling of aeration rate.
[0043] According to the water treatment apparatus and
the water treatment method according 5 to the second
embodiment, the values of the aeration rate of air to be
supplied into the bioreactor tank 1 are set based on the
difference between the pollutant concentration and the
target value of the pollutant concentration, of the
10 treatment target water flowing or flowed out of the
bioreactor tank 1. This enables the pollutant
concentration of the treatment target water flowed out
after the biological reaction treatment to be brought
closer to the target value.
15 In addition, the aeration rates are calculated to
cause an aeration unit disposed closer to the outlet of the
bioreactor tank 1 to provide more stringent PID control to
control the effluent pollutant concentration of the
treatment target water to a target value, thereby enabling
20 the pollutant concentration of the effluent water to be
more finely controlled toward the target value, and thus
enabling the effluent water quality to be stably maintained.
[0044] Third Embodiment.
A biological water treatment apparatus according to a
25 third embodiment of the present invention will now be
described with reference to FIG. 4. FIG. 4 is a
configuration diagram of a biological water treatment
apparatus.
In the third embodiment, the influent load measurement
30 unit 5 fitted on the inlet side of the bioreactor tank and
the effluent pollutant concentration measurement unit 6
fitted on the outlet side of the bioreactor tank are both
installed. The value of the influent load is sent to the
26
first aeration rate calculation unit 71, to the second
aeration rate calculation unit 72, and to the third
aeration rate calculation unit 73 via the signal line 5a,
and the effluent pollutant concentration is also sent to
the first aeration rate calculation unit 5 71, to the second
aeration rate calculation unit 72, and to the third
aeration rate calculation unit 73 via the signal line 6a.
Note that, in the third embodiment, elements identical
or equivalent to the corresponding elements in the first
10 embodiment and in the second embodiment are designated by
like reference characters, and duplicate description
thereof will be omitted.
[0045] FIG. 5 is a configuration diagram of an aeration
rate calculation unit according to the third embodiment.
15 The aeration rate calculation unit 71 includes the effluent
pollutant concentration difference calculation unit 8, the
proportional term calculation unit 9, the integral term
calculation unit 10, the derivative term calculation unit
11, the target aeration rate calculation unit 12, and
20 signal lines connecting these calculation units to one
another. In addition, the configuration differs from the
configuration of FIG. 3 in that the target aeration
calculation unit 12 is also connected with the signal line
5a that transmits the measurement result from the influent
25 load measurement unit 5. Referring to FIG. 5, a method for
calculating the aeration rate will be described that is
performed in the first aeration rate calculation unit 71,
in the second aeration rate calculation unit 72, and in the
third aeration rate calculation unit 73. Note that
30 although FIG. 5 illustrates the aeration rate calculation
unit 71, the aeration rate calculation units 72 and 73 are
similarly configured. In addition, the effluent pollutant
concentration difference calculation unit 8, the
27
proportional term calculation unit 9, the integral term
calculation unit 10, the derivative term calculation unit
11, and the signal lines 8a, 8b, and 8c are identical or
equivalent to the corresponding elements illustrated in FIG.
5 3.
The target aeration rate calculation unit 12
calculates the setting value of the aeration rate of air to
be supplied from the first aeration unit 31 based on the
value of the influent load sent via the signal line 5a, on
10 proportional term information sent via the signal line 9a,
on integral term information sent via the signal line 10a,
and on derivative term information sent via the signal line
11a.
[0046] Each of the aeration rate calculation units
15 stores the first coefficient ki1, the second coefficient ki2,
and the aeration unit constant ki3 predetermined for the
corresponding one of the aeration units, and calculates the
sum of (a), (b), and (c) described below based on the value
of the influent load of the treatment target water flowing
20 into the bioreactor tank 1 sent via the signal line 5a, and
on the amount GP of proportional control, on the amount GI
of integral control, and the amount GD of derivative
control sent via the signal lines 9a, 10a, and 11a.
(a) An inlet-side controlled aeration rate based on a
25 value calculated by multiplication of the influent load of
the treatment target water flowing into the bioreactor tank
1 measured by the influent load measurement unit 5, by the
first coefficient predetermined for that aeration unit
(b) An outlet-side controlled aeration rate based on a
30 value calculated by multiplication of a sum (GP+GI+GD) by
the second coefficient predetermined for that aeration unit
(c) Aeration unit constant
By sending the setting values of the aeration rate
28
calculated as described above to the respective aeration
units connected to the respective aeration rate calculation
units, air is supplied at the respective aeration rates
from the respective aeration units to the bioreactor tank.
[0047] Note that the first coefficient, 5 the second
coefficient, and the constant described above are each an
optimum value obtained from simulation or from an analysis
result of actual plant data so that an optimum aeration
rate, which allows the pollutant concentration of the
10 effluent water that are drained out of the bioreactor tank
1 to be brought even closer to a predetermined target value
of the pollutant concentration, can be obtained. Thus,
different values are set depending on the positions of, or
on the number of, the aeration units. The first
15 coefficient is set to a higher value for a position closer
to the inlet of the bioreactor tank, while the second
coefficient is set to a higher value for a position closer
to the outlet of the bioreactor tank.
The aeration rate calculation unit adds together a
20 value, calculated based on the influent load of the
treatment target water, that produces a higher aeration
rate for an aeration unit closer to the inlet in the
bioreactor tank, and a value, calculated based on the
effluent pollutant concentration, that produces a greater
25 amount of feedback control of aeration rate for an aeration
unit closer to the outlet in the bioreactor tank, thus to
calculate each aeration rate. The setting value Gi
[Nm3/hr] of the aeration rate for each of the aeration
units is calculated using Equation (10).
30 [0048]
[Formula 10]
... (10)
29
[0049] Here, Gi is a setting value of the aeration rate
of air to be supplied to each of the aeration units. The
parameter i=1, ∙∙∙, n represents the number of each
aeration unit, and is the order of the aeration unit along
the flow direction of the treatment target 5 water in the
bioreactor tank. The number n is a natural number greater
than or equal to 2. SIN is the influent pollutant
concentration, and is the ammonia nitrogen concentration
measurement value [unit: mg/L] of the treatment target
10 water flowing into the bioreactor tank. QIN is the flow
rate measurement value [unit: m3/hr] of the treatment
target water flowing into the bioreactor tank. GP, GI, and
GD are, respectively, the amount of proportional control,
the amount of integral control, and the amount of
15 derivative control, each calculated from the effluent
pollutant concentration difference based on the effluent
pollutant concentration measured and on the pollutant
concentration target value of the effluent water. The
factor ki1 is the first coefficient for that aeration unit,
20 ki2 is the second coefficient for that aeration unit, and
ki3 is the aeration unit constant for the first aeration
unit 31.
For example, in the case in which the influent load
measurement unit 5 includes a flowmeter and an ammonia
25 nitrogen concentration meter, and the effluent pollutant
concentration measurement unit 6 includes an ammonia
nitrogen concentration meter, the aeration rate calculation
unit 71 calculates the setting value G1 [Nm3/hr] of the
aeration rate of air to be supplied from the first aeration
30 unit 31 using Equation (11).
[0050]
[Formula 11]
30
... (11)
[0051] Here, k11 is the first coefficient for the first
aeration unit 31. k12 is the second coefficient for the
first aeration unit 31. k13 is the aeration unit constant
for the first aeration unit 31.
Similarly, the aeration rate calculation 5 units 72 and
73 calculate the respective setting values G2 and G3
[Nm3/hr] of the aeration rate of the second aeration unit
32 and 33 using Equations (11) and (12).
[0052]
[Formula 12]
... (12)
10 [0053]
[Formula 13]
... (13)
[0054] Here, k21 is the first coefficient for the second
aeration unit 32, k22 is the second coefficient for the
second aeration unit 32, and k23 is the aeration unit
constant for the second aeration unit 32.
15 In addition, k31 is the first coefficient for the
third aeration unit 33, k32 is the second coefficient for
the third aeration unit 33, and k33 is the aeration unit
constant for the third aeration unit 33.
In Equations (11), (12), and (13), the first
20 coefficient and the second coefficient predetermined for
each of the aeration units are, as described above, each an
optimum value obtained from simulation or from an analysis
result of actual plant data so as to obtain an optimum
aeration rate allowing the pollutant concentration of the
25 effluent water to be brought even closer to a predetermined
target value of the pollutant concentration. Moreover, the
31
values are set to allow the first coefficients k11, k21, and
k31 to satisfy a relationship of k11≥k21≥k31, and to allow
the second coefficients k12, k22, and k32 to satisfy a
relationship of k12≤k22≤k32. In addition, similarly to the
first embodiment and the second embodiment, 5 each of the
aeration unit constants k13, k23, and k33 is set to the
minimum value of the aeration rate for that aeration unit
to provide fine adjustment of the aeration rate of each of
the aeration units.
10 Thus, the aeration rate calculation unit adds together
the value, calculated based on the influent load of the
treatment target water, that produces a higher aeration
rate for an aeration unit closer to the inlet in the
bioreactor tank, and the value, calculated based on the
15 effluent pollutant concentration, that produces a greater
amount of feedback control of aeration rate for an aeration
unit closer to the outlet in the bioreactor tank, thus to
calculate each aeration rate.
Note that the foregoing description assumes that three
20 aeration units are installed. Because two or more aeration
units are desirably installed in the aerobic zone 102 in
the bioreactor tank 1 along the flow direction of the
treatment target water, a plurality of aeration units are
installed. The aeration rate calculation unit is capable
25 of calculating, for the multiple aeration units, an optimum
aeration rate of air to be supplied from each of the
aeration units using Equation (10).
In addition, Equation (10) provides calculation of the
inlet-side controlled aeration rate based on a variation in
30 the influent load of the treatment target water by a
product of the flow rate of the treatment target water
flowing into the bioreactor tank 1 and the influent
pollutant concentration. However, in a case in which the
32
flow rate of the treatment target water flowing into the
bioreactor tank 1 is only measured, setting of, as the
value of (a), a value calculated by multiplication of the
flow rate of the treatment target water flowing into the
bioreactor tank 1 by the first coefficient 5 predetermined
for that aeration unit, enables the setting value of the
aeration rate to be calculated using Equation (4).
Similarly, in a case in which the ammonia nitrogen
concentration of the treatment target water flowing into
10 the bioreactor tank 1 is only measured, setting of, as the
value of (a), a value calculated by multiplication of the
ammonia nitrogen concentration of the treatment target
water flowing into the bioreactor tank 1 by the first
coefficient predetermined for that aeration unit, enables
15 the setting value of the aeration rate to be calculated
using Equation (4).
[0055] Although FIG. 4 illustrates the influent load
measurement unit 5 as being installed to the pipe 103 or
installed to a water conduit other than the pipe to measure
20 the influent load of the treatment target water before
flowing into the bioreactor tank 1, the influent load
measurement unit 5 may also be fitted, similarly to the
first embodiment, at the fitting point 104 or at the
fitting point 105 in the bioreactor tank 1. The fitting
25 point 104 is positioned on the inlet side in the bioreactor
tank 1, in the anaerobic zone. The fitting point 105 is
positioned at a position where the first aeration unit 31,
i.e., the one closest to the inlet in the bioreactor tank 1,
is disposed, that is, at a position on the entry side of
30 the aerobic zone.
The measurement point of the influent load measurement
unit 5 can be changed the fitting point to one of the pipe
103, the fitting point 104, and the fitting point 105
33
depending on the control purpose. In a treatment plant
subjected to an influent load that varies significantly,
connection of the influent load measurement unit 5 to the
pipe 103 enables a variation in the influent load to be
promptly detected. This improves followability 5 of the
aeration rate to the variation in the influent load, and
can thus stabilize effluent water quality. Meanwhile, use
of the fitting point 105 allows measurement of an actual
influent load flowing into the aerobic zone, thereby
10 enabling the aeration rate necessary for the treatment to
be accurately computed, and enabling the total aeration
rate to be thus minimized.
[0056] In addition to the treatment target water flowed
in through the pipe 103, the bioreactor tank 1 also
15 receives activated sludge that has returned from the
settling tank 2 through the pipe d. When a need exists to
also take into account the effect of the return activated
sludge in addition to the effect of a variation in the
influent load of the treatment target water, the influent
20 load measurement unit 5 is fitted at the fitting point 104
near the entry of the bioreactor tank 1. This achieves
measurement of the actual influent load flowing into the
bioreactor tank 1, thereby enabling a variation in the
influent load to also be quickly responded to while taking
25 into account the effect of the returned sludge. Due to the
position also enabling prompt response to a variation in
the influent load, this can provide a proper air supply,
and can further reduce the aeration rate as compared to
when measurement is performed at the pipe 103.
30 Note that installation of the influent load measurement
unit 5 at the fitting point 104 causes the aeration rate of
each of the first aeration unit 31, the second aeration
unit 32, and the third aeration unit 33 to be calculated
34
based on the influent load of the treatment target water
before passage through the anaerobic zone, which produces a
time lag in controlling of aeration rate. Such time lag
can be eliminated for further reduction in the aeration
rate by installing the influent load measurement 5 unit 5 at
the fitting point 105, positioned at the entry of the
aerobic zone where the activated sludge is about to be
mixed with air in the bioreactor tank 1.
Although FIG. 4 illustrates a configuration in which
10 only the anaerobic zone precedes the aerobic zone, the
configuration may also include two or more zones involving
no aeration being provided upstream of the aerobic zone, a
typical example of which is an anaerobic-anoxic-oxic method
(A2O method), which is a biological treatment for
15 simultaneously removing phosphorus and nitrogen. In this
case, a similar advantage can be achieved by positioning
the fitting point 104 on the inlet side inside the
bioreactor tank 1 and positioning the fitting point 105 on
the entry side of the aerobic zone.
20 [0057] Moreover, FIG. 4 illustrates the effluent
pollutant concentration measurement unit 6 as being
installed to the pipe 106 provided on the outlet side
outside the bioreactor tank or installed to a water conduit
other than the pipe, to measure the effluent pollutant
25 concentration of the treatment target water flowed out of
the bioreactor tank 1. However, the measurement point of
the effluent pollutant concentration measurement unit 6 can
be changed the fitting point to one of the pipe 106 and the
fitting point 107 depending on the control purpose
30 similarly to the second embodiment.
Use of a point in the pipe 106 allows water quality of
the effluent water flowed out of the bioreactor tank to be
directly measured, thereby providing computation of the
35
aeration rate necessary to control the effluent water
quality to the target value. When emphasis is placed on a
reduction in the aeration rate to avoid excessive aeration
that provides a higher level of water quality than required,
the effluent pollutant concentration measurement 5 unit 6 can
be installed to the pipe 106.
[0058] Meanwhile, when a need exists for reliably
preventing the water quality of the effluent water from
exceeding a management value, the effluent pollutant
10 concentration measurement unit 6 is installed at the
fitting point 107, upstream of the outlet at the downstream
end in the bioreactor tank 1. Use of the fitting point 107
allows water treatment to be continued until the treatment
target water completely flows out even after the effluent
15 pollutant concentration measurement unit 6 measures water
quality, thereby enabling the effluent water quality to be
reliably controlled to a level of, or less than, the
management value.
This means that the ammonia concentration is
20 accordingly reduced to the target value before complete
termination of the biological treatment reaction in the
reactor tank, thereby making it likely that the total
aeration rate will be higher than when the effluent
pollutant concentration measurement unit 6 is installed to
25 the pipe 106. This enables the water quality of the
eventual effluent water to be kept at an appropriate level
owing to treatment in a zone downstream of the fitting
point 107 even when the pollutant concentration measured by
the effluent pollutant concentration measurement unit 6
30 reaches or exceeds the target value due to delay in the
controlling of aeration rate.
[0059] The water treatment apparatus and the water
treatment method according to the third embodiment each set
36
the values of the aeration rate of air to be supplied into
the bioreactor tank 1 taking into account both the influent
load of the treatment target water flowing or flowed into
the bioreactor tank 1 and the difference between the
pollutant concentration of the effluent 5 water being
currently drained out of the bioreactor tank 1 and the
target value thereof. This enables the pollutant
concentration of the effluent water to be brought even
closer to the target value, and thus enables the water
10 quality to be more finely controlled.
[0060] In addition, computation of the aeration rate is
subjected to a condition of magnitude relationship among
the coefficients each predetermined for the first aeration
unit 31, for the second aeration unit 32, and for the third
15 aeration unit 33 respectively connected to the first air
supply unit 41, to the second air supply unit 42, and to
the third air supply unit 43 based on the positions thereof
in the bioreactor tank 1. This causes air to be supplied
from an aeration unit closer to the inflow port of the
20 bioreactor tank 1 depending primarily on the influent load
of the treatment target water flowing or flowed into the
bioreactor tank 1, and from an aeration unit closer to the
outflow port of the bioreactor tank 1 depending primarily
on the difference between the pollutant concentration of
25 the effluent water and the target value thereof. This can
provide suitable air supply at each particular point in the
bioreactor tank 1 even under variation in the influent load,
and enables the pollutant concentration of the effluent
water that is to be drained to be brought even closer to
30 the target value. Moreover, efficient water quality
control can be provided using proper amounts of air supply.
37
Reference Signs List
[0061] 1 bioreactor tank; 5 influent load measurement
unit; 6 effluent pollutant concentration measurement unit;
8 effluent pollutant concentration difference calculation
unit; 9 proportional term calculation 5 unit; 10 integral
term calculation unit; 11 derivative term calculation
unit; 12 target aeration rate calculation unit; 30
aeration unit; 31 first aeration unit; 32 second aeration
unit; 33 third aeration unit; 40 air supply unit; 41
10 first air supply unit; 42 second air supply unit; 43
third air supply unit; 70 aeration rate calculation unit;
71 first aeration rate calculation unit; 72 second
aeration rate calculation unit; 73 third aeration rate
calculation unit; 100 partition plate; 101 anaerobic
15 zone; 102 aerobic zone; 103, 106, 108 pipe; 104, 105, 107
fitting point.
38
We Claim :
1. A water treatment apparatus that aerates, with air,
treatment target water that flows into a bioreactor tank
through an inlet, performs biological reaction treatment,
and drains the treatment target water out 5 of the bioreactor
tank through a drain port, the water treatment apparatus
comprising:
a first aeration unit and a second aeration unit to
each aerate the treatment target water with the air; and
10 an aeration rate calculation unit to control an
aeration rate of the first aeration unit and an aeration
rate of the second aeration unit, wherein
the first aeration unit is disposed at a position less
distant from the inlet than the second aeration unit in the
15 bioreactor tank, and
the aeration rate calculation unit provides control to
produce different aeration rates for the first aeration
unit and the second aeration unit.
20 2. The water treatment apparatus according to claim 1,
comprising:
a third aeration unit to aerate the treatment target
water with the air, wherein
the third aeration unit is disposed at a position more
25 distant from the inlet than the second aeration unit in the
bioreactor tank, and
the aeration rate calculation unit provides control to
produce different aeration rates for the first aeration
unit, the second aeration unit, and the third aeration unit.
30
3. The water treatment apparatus according to claim 1 or
2, comprising:
an influent load measurement unit to measure an
39
influent load of the treatment target water, wherein
the aeration rate calculation unit provides control to
produce the different aeration rates for the respective
aeration units based on the influent load of the treatment
5 target water.
4. The water treatment apparatus according to claim 1 or
2, comprising:
an effluent pollutant concentration measurement unit
10 to measure an effluent pollutant concentration of the
treatment target water, wherein
the aeration rate calculation unit provides feedback
control to produce the different aeration rates for the
respective aeration units based on the effluent pollutant
15 concentration.
5. The water treatment apparatus according to claim 1 or
2, comprising:
an influent load measurement unit to measure an
20 influent load of the treatment target water; and
an effluent pollutant concentration measurement unit
to measure an effluent pollutant concentration of the
treatment target water, wherein
the aeration rate calculation unit determines the
25 aeration rate for each of the aeration units by adding
together an inlet-side controlled aeration rate and an
outlet-side controlled aeration rate, the inlet-side
controlled aeration rate being calculated to produce
different values for the aeration units based on the
30 influent load of the treatment target water, the outletside
controlled aeration rate being calculated to produce
different values for the aeration units based on the
effluent pollutant concentration.
40
6. The water treatment apparatus according to claim 3 or
5, wherein the influent load measurement unit measures an
influent load of the treatment target water before the
treatment target water flows into the bioreactor tank.
5
7. The water treatment apparatus according to claim 3 or
5, wherein the influent load measurement unit is installed
at a position closer to the inlet in the bioreactor tank.
10 8. The water treatment apparatus according to claim 3 or
5, wherein the influent load measurement unit is installed
at a position where one aeration unit that is closest to
the inlet in the bioreactor tank is disposed, out of the
plurality of aeration units.
15
9. The water treatment apparatus according to claim 4 or
5, wherein the effluent pollutant concentration measurement
unit measures an effluent pollutant concentration of the
treatment target water that flows out of the bioreactor
20 tank.
10. The water treatment apparatus according to claim 4 or
5, wherein the effluent pollutant concentration measurement
unit is installed in a portion closer to an outlet inside
25 the bioreactor tank.
11. A water treatment method comprising:
a step of measuring an influent load of treatment
target water that flows into a bioreactor tank;
30 a step of calculating, based on the influent load, an
inlet-side controlled aeration rate of each of a plurality
of aeration units disposed along a direction of flow of the
treatment target water in the bioreactor tank to produce
41
different inlet-side controlled aeration rates for the
respective aeration units; and
a step in which each of the aeration units supplied
with air that corresponds to a corresponding one of the
aeration rates aerates the treatment target 5 water with the
air.
12. A water treatment method comprising:
a step of measuring an effluent pollutant
10 concentration of treatment target water that flows out of a
bioreactor tank;
a step of calculating, based on the effluent pollutant
concentration, an outlet-side controlled aeration rate of
each of a plurality of aeration units disposed along a
15 direction of flow of the treatment target water in the
bioreactor tank to produce different outlet-side controlled
aeration rates for the respective aeration units; and
a step in which each of the aeration units supplied
with air that corresponds to a corresponding one of the
20 aeration rates aerates the treatment target water with the
air.
13. A water treatment method comprising:
a step of measuring an influent load of treatment
25 target water that flows into a bioreactor tank;
a step of measuring an effluent pollutant
concentration of the treatment target water that flows out
of the bioreactor tank;
a step of calculating, based on the influent load, an
30 inlet-side controlled aeration rate of each of a plurality
of aeration units, which are disposed along a direction of
flow of the treatment target water in the bioreactor tank,
to produce different inlet-side controlled aeration rates
for the respective aeration units, and
a step of calculating, based on the effluent pollutant
concentration, an outlet-side controlled aeration rates of
each of the aeration units to produce different outlet-side
controlled aeration rates for the respective 5 aeration
units;
a step of determining an aeration rate for each
corresponding one of the aeration units by adding together
the inlet-side controlled aeration rate and the outlet-side
10 controlled aeration rate; and
a step in which each of the aeration units supplied
with air that corresponds to a corresponding one of the
aeration rates aerates the treatment target water with the
air.
15
14. The water treatment method according to claim 12 or 13,
wherein
the step of calculating an outlet-side controlled
aeration rate includes,
20 calculating an amount of proportional control, an
amount of integral control, and an amount of derivative
control each based on an effluent pollutant concentration
difference calculated from the effluent pollutant
concentration and a pollutant concentration target value of
25 effluent water, and adding together the amount of
proportional control, the amount of integral control, and
the amount of derivative control.