Purification apparatus

A purification apparatus and method for enabling the purification of the lake and pond waters, is installed as a fluidized bed sewage system directly on the raw water area. The apparatus takes in the raw waters in the lake and pond and purifies the water. The purified water is fed back to the raw water area by the pump. With this purification apparatus, the salt materials such as phosphate in the lakes, and the overall area of the waters can be purified while preventing the generation of phytoplanktons.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to a purification apparatus and method for 
purifying directly the lakes and ponds in which the density of acid such 
as nitric and phosphoric due to gray water, animal uric acid sewage and 
sewage flowing into the lakes and ponds is adequately controlled. 
In case of purifying the organic raw water in conventional systems a 
contact purification method uses biological films. Contact aeration 
process water treatment method is one of these purification methods. As 
for an actual implementation of contact aeration process water treatment 
method, what is well known conventionally is a multi-layered processing 
apparatus in which the processed water is forced to contact directly the 
contact media including aerobic microbes, and the purification process is 
achieved while the processed water running through the several multilayers 
developed from upstream to down stream. In an apparatus disclosed in 
Japanese Patent Open No. 62-74489 (1987), the contact aeration layer is 
buried under the ground apart from the polluted water site, and the 
multi-layered purification system is made not to be found on the ground. 
As for other contact purification methods, what is often used is the 
submerged filter contact purification method, in which biological films 
are adhered on the filter media and the raw water is led to the filter 
media. In this method, two sub categories exist; in the fixed bed method, 
the contact media to which biological films adhere are fixed as the 
submerged filters, and on the other hand, in the fluidized bed method, the 
contact media with its specific gravity defined relatively larger than the 
specific gravity of water, for example, about 1.2, may be allowed to move 
freely in the processed water. As for the later category, the fluidized 
bed method, as disclosed in Japanese Patent Open No. 1-218691 (1990), 
there is such an example that the raw water with very high impurity 
density is purified by using the fluidized bed contact purification method 
accompanying with fresh air exposure. And as disclosed in Japanese Patent 
Open No. 6-99185 (1995), there is such an example that the raw water is 
purified by supplying the processed water mixed with the fresh air into 
the fluidized bed buries under ground. 
If the purification facility is constructed in the shore or surrounding 
area of the lakes and ponds, and conventional purification method usually 
used in the sewage water treatment plant and/or the water purification 
plant is applied, a large amount of energy is required in addition to the 
minimum amount of energy to operate the purification facility. This is 
because the pressure loss occurs for transporting the raw water from the 
water intake port to the water treatment plant and because the pump work 
is required for transporting the raw water from the lake water level to 
the higher water level in which the water purification plant exists. In 
selecting the building site for the purification plant, a relatively 
small-scale sewage system can be built under ground. However, for 
purifying the lake and pond waters, it is required to treat larger amount 
of waters with lower impurity density than the sewage water treatment 
plant does. For the purification of lakes and ponds, the size of the 
sewage system becomes larger and it is difficult to locate the sewage 
system in the underground site, and therefore, there is such a problem 
that a building site for the purification facility can not be always 
selected to be at an optimal place. 
If the sewage system is installed underground and the aeration process is 
required for injecting the chemical materials into the raw waters, there 
is not any sufficient way for preventing completely the flow-out of the 
filter media outside the facility to the lake waters. 
An object of the present invention is to provide a purification apparatus 
operable with lower power. 
Another object of the present invention is to provide a purification 
apparatus with which newly added systems can be integrated if necessary. 
Yet another object of the present invention is to provide a purification 
apparatus which enables to control the density of impurities contained in 
the purified water. 
Another object of the present invention is to provide a purification 
apparatus which operates water treatment efficiently for large amount of 
water in the lakes and ponds. 
In order to achieve the above objectives, the purification apparatus of the 
present invention is so configured as to contain a water inlet port for 
in-taking water; a filter container in which filter media for purifying 
the process water taken in through the water inlet port are filled; and a 
pump for discharging the purified water processed by the filter media, in 
which the filter container in which the filter media is filled is placed 
inside the waters to which the purification operation is applied. 
In the purification apparatus of the present invention, a fluidized bed 
filter container in which the filter media are filled and a pump are 
placed in the water to which the purification operation is applied, and 
the water level of the fluidized bed is so maintained to be lower than the 
water level of the waters to which the purification operation is applied 
by way of discharging the purified water in the upper part of the 
fluidized bed to the waters to which the purification operation is applied 
by the pump. The water flow from the water inlet port to the fluidized bed 
filter container can be established by the head pressure difference 
between the water level of the waters to be purified and the water level 
of the fluidized bed. 
The purification apparatus of the present invention is placed in the waters 
area such as lakes ponds and oceans, and comprises a purification part for 
removing the pollution materials and/or specified materials contained in 
the waters to be purified; a water inlet part for taking in the raw water 
in the waters to be purified and forwarding the raw water to the 
purification part; a water discharge part for feeding back the purified 
water processed in the purification part; and a pump, in which the 
purification part is floating on the waters area to be purified and the 
purification part, the pump and the water discharge part are connected 
sequentially. 
The purification apparatus of the present invention is placed in the waters 
area such as lakes ponds and oceans, and comprises a purification part for 
removing the pollution materials and/or specified materials contained in 
the waters to be purified; a water inlet part for taking in the raw water 
in the waters to be purified and forwarding the raw water to the 
purification part; a water discharge part for feeding back the purified 
water processed in the purification part; and a pump, in which the 
purification part is floating on the waters area to be purified and the 
purification part contains a fluidized bed filter system. 
In addition, in the purification apparatus of the present invention, a 
float is placed in the filter container, and a wire and an anchor are used 
for stably fixing the filter container floating on the waters to be 
purified. A sand filter for catching the floating materials in the water 
is also placed between the water inlet port and the filter media. A 
reverse scrubbing mechanism is also included for refreshing the sand 
filter when blinding or clogging in the sand filter occurs. A solar panel 
and a battery storing electric power are also equipped in order to utilize 
the solar energy used for the electric power supplied to the pump. A 
control scheduler generates operation signals for the purification 
apparatus in order to establish the operation with respect to the 
pre-defined operation modes. 
In order to achieve the above objectives, the purification apparatus of the 
present invention is so configured as to contain a water inlet port for 
taking in water; and a filter container assembled in a unit in which 
filter media for purifying the process water taken in through the water 
inlet port are filled, in which a plurality of filter containers, each 
assembled in an individually separated unit, are connected to the water 
inlet ports. 
The purification apparatus of the present invention is so configured as to 
contain a water inlet port for taking in water; a filter container in 
which filter media for purifying the process water taken in through the 
water inlet port are filled; and a pump for discharging the purified water 
processed by the filter media, in which the water intake port and the 
water discharge port for discharging the purified water are formed in the 
horizontal direction, and the water inlet port and the water discharge 
ports are connected to each other. 
In the purification apparatus of the present invention, the private sewage 
system is comprised of at least two or more units, and unit connectors 
between units are also provided. In addition, the purification apparatus 
has apparatus for judging the abnormal status of the operation of the 
pump; and an abnormal signal generator for generating an abnormal signal 
when any abnormal status is detected by the judgment means. 
In order to achieve another object, a lake purification apparatus of the 
present invention, placed in the water area such as lakes, rivers and 
oceans, comprises a purification part for removing the pollution materials 
and/or specified materials contained in the waters to be purified; a water 
inlet part for taking in the raw water in the waters to be purified and 
forwarding the raw water to the purification part; a water discharge part 
for feeding back the purified water processed in the purification part; 
and a pump, in which the purification apparatus is floating on the water 
area to be purified, and the discharged water from the water discharge 
port is so operated as to reach the area far from the water inlet port and 
to satisfy the following relationship, 
EQU N2&lt;N0, 
EQU N2&lt;N1, and 
EQU (N1-N2)/(N0-N2)&gt;0.95, 
where 
N0 is the average density of the target material to be removed by the 
purification apparatus and contained in the water of the water area to be 
purified; 
N1 is the density of the target material to be removed and contained in the 
water taken in from the water inlet part of the purification apparatus; 
and 
N2 is the density of the target materials contained in the water discharged 
from the water discharge part. 
In order to achieve yet another object, a lake purification apparatus of 
the present invention, placed in the water area such as lakes, rivers and 
oceans, comprises a purification part for removing the pollution materials 
and/or specified materials contained in the waters to be purified; a water 
inlet part for taking in the raw water in the waters to be purified and 
forwarding the raw water to the purification part; a water discharge part 
for feeding back the purified water processed in the purification part; 
and a pump, in which the purification apparatus is floating on the water 
area to be purified, and the purification part is so assembled with a 
plurality of individually separated sewage systems, a water path is so 
formed that the water taken in from the water inlet part may be 
sequentially supplied to the plurality of sewage systems in series, and 
the final stage of the downstream of the water path connects to the water 
discharge part. 
The purification apparatus of the present invention comprises a 
purification part for removing the pollution materials and/or specified 
materials contained in the waters to be purified; a water inlet part for 
taking in the raw water in the waters to be purified and forwarding the 
raw water to the purification part; a water discharge part for feeding 
back the purified water processed in the purification part; and a pump, in 
which the purification apparatus is floating on the water area to be 
purified, and the purification part is so assembled with a plurality of 
individually separated sewage systems, a water path is so formed that the 
water taken in from the water inlet part may be sequentially supplied to 
the plurality of sewage systems in series, and the final stage of the 
downstream of the water path connects to the water discharge part. In 
purifying the waters in lakes and ponds, it is necessary to treat large 
amount of water with its density lower, and therefore, it is necessary to 
reduce the process loss as much as possible with an adequate layout of 
sewage systems by shortening the distance between the water treatment 
plant and the inlet port of the raw water. With this configuration, in 
order to consider the water level changes due to rain and water discharge, 
the sewage system floating on the water can be fixed in a definite 
position with a float and an anchor mounted on the sewage system, which 
leads to the shorter distance between the water inlet port and the sewage 
system and the lower process loss in transporting the water between them. 
In addition, as the wider area on the water surface can be efficiently 
used, a unit of the water inlet port and the sewage system can be located 
in a designated position for which the water purification is required 
among the whole waters areas. 
The filtered materials captured in the filter is led to the filtered 
material reservoir by opening the reverse scrubbing valve. 
Owing to the above described configuration, the components of the apparatus 
can be replaced by parts when maintenance work is required, and the number 
of the sewage systems to be installed initially and their combination can 
be arranged conditionally according to the allowable initial investment. 
In addition, the necessary additional systems may be allowed. As the 
number of units to be deployed can be adjusted according to the area size 
of the waters to be purified, a mass production of units is made possible 
and the cost merits with more inexpensive fabrication cost than an 
integrated model can be achieved. 
In addition to the reduction of the fabrication cost, the density of 
impurities contained in the purified water to be discharged finally can be 
controlled by determining an optimal number of sewage systems. 
And furthermore, by making the sewage system float on the waters, the 
effect of the water level changes can be reconciled. If the distance 
between the water inlet part and the water discharge part is set to be 
large enough and the feedback ratio of the purified water from the water 
discharge part to the water inlet part is controlled so as to be less than 
5%, the designated generic performance of the sewage system can be 
achieved without making the scale size of the sewage system larger. In 
this case, as at least one part of the fluidized bed purification 
apparatus is exposed above the water level, a new water surface is formed 
between the apparatus and the water area to be purified. Thus, as for the 
flowing out of the filter media, the filter media do not contact directly 
to the water area, the risk of the flowing out of the filter media may be 
estimated to be lower than the case in which the sewage system is placed 
below the water surface. 
As the waters to be processed is forced to be exposed to the water surface 
before entering the fluidized bed and the waters are naturally exposed to 
the air, it is preferable for the biological process for the aerobic 
microbe in the fluidized bed. In addition, if the depth of water is 
shallow, the exposure effect can be brought by the tank installed at the 
preliminary stage of the fluidized bed, and what is expected is such an 
effect that the pressure head difference between the water level of the 
waters to be purified and the water level of the water at the upper part 
of the fluidized bed can be made larger. By arranging the fluidized beds 
in series, there is another effect that the duration time for the waters 
to contact the air in the fluidized bed can be sufficiently larger to 
obtain a designated effect.

DETAILED DESCRIPTION OF THE DRAWINGS 
As shown in FIG. 1, the purification apparatus for purifying the lake water 
in this embodiment comprises the following main components; a fluidized 
bed container 1 filled with fluidized bed filter media 13, a water intake 
tube 8 for leading the raw water into the fluidized bed container 1, a 
float 2 for floating the fluidized bed container 1, a wire 3 for fixing 
the fluidized bed container 1 with the anchor 4 mounted on the lake bottom 
12, a water level sensor 11 for observing the water level 10 of the upper 
surface of the fluidized bed, a pump 5 for taking the purified water 
contained in the fluidized bed container 1 by the suction pipe 7, and a 
drainage (or discharge) pipe 6. 
The length of the wire 3 is selected to be longer, so that the position of 
the fluidized bed container 1 relative to the water surface is kept 
constant even if the water level of the lake may change. The purified 
water is taken in through the suction pipe 7 by the pump 5, and is 
discharged out to the waters to be purified by the drainage pipe 6. The 
water level 10 of the upper surface of the fluidized bed is observed by 
the water level sensor 11, and the pump 5 is so controlled that the water 
level 10 may be kept to be lower a designated value than the water level 9 
of the waters to be purified. Owing to the water level difference between 
the water level 9 of the waters to be purified and the water level 10 of 
the upper surface of the fluidized bed, the raw water is flowing through 
the water intake pipe 8 into the fluidized bed container where the water 
purification operation is achieved with the fluidized bed filter media 13. 
A stationary operation of the purification apparatus is established when 
the water level difference and the fluid path resistance when the raw 
water passes through the filter media are balanced. With this 
configuration, the necessary power for operating the purification 
apparatus is smaller without preparing the pressure container in the 
purification apparatus system, and therefore, an unmanned operation can be 
achieved safely with solar cells for the electric power supply. 
As shown in FIG. 2, in the purification apparatus for the lake water in 
this embodiment, the sewage system is located in a definite position in 
the lake waters with the float 2, the wire 3 and the anchor 4. As the 
sewage system is floating on the water surface with the float 2, the 
sewage system moves up and down in response to the changes in the water 
level 9 of the lake waters, and the water intake port 8 is kept in a 
constant position relative to the water level 9 of the lake waters. In 
this embodiment, there are four categories of water levels defined inside 
the sewage system; the water level 9 of the lake waters, the first water 
level 17, the second water level 18 and the water level 10 of the upper 
surface of the fluidized bed. At first, the raw water of the lake waters 
is taken in through the control valve 15 owing to the pressure head 
difference between the water level 9 of the lake waters and the first 
water level 17. Next, the intake raw water is lead through the sand filter 
14 into the lower end part of the fluidized bed filter media 13 due to the 
pressure head difference between the first water level 17 and the second 
water level 18. In this second stage, the processed water captures oxygen 
due to the air exposure effect on the water surface of the second water 
level, 18 in which the air and the water forming a liquid-vapor interface 
interact each other. In addition, the injection of chemical additives in 
the second water level 16 gives very effective mixture of waters and 
chemical additives. If the sand filter 14 is blocked and the pressure loss 
increases, the first water level 17 comes close to the water level 9 of 
the lake waters and become equal to the second water level 18 due to 
overflow. Thus, in case that the sand filter 14 fails to operate normally, 
even if the sand filter 14 suffers from blocking, the operation of the 
sewage system can be continued as the processed water bypasses the sand 
filter 14, and overflows and comes into the lower part of the fluidized 
bed filter media 13. The processed water purified by the fluidized bed 
filter media 13 is taken through the suction pipe 7 by the pump 5 and 
discharged to the lake through the water discharge pipe 6. 
Thus, as the raw water can be purified while the head pressure difference 
can be made smaller, as for the electric power, a solar panel 18 can be 
used for generating electric power for driving the pump 5. When sludge is 
stacked near the water level 10 of the upper surface of the fluidized bed, 
the water level 10 of the upper surface of the fluidized bed can be 
increased by stopping the pump 5, and the sludge flowing over into the 
sludge reservoir 20 can be extracted out by the sludge extraction pump 19. 
In this embodiment, the speed of the flow of the processed water passing 
through the fluidized bed filter media 13 is estimated to be about 1 
mm/sec, and the designated unit of the processed water passes through the 
fluidized bed filter media 13. 
As shown in FIG. 3, the purification apparatus for the lake waters in this 
embodiment is so configured as same as the embodiment shown in FIG. 2, in 
which the sewage system is fixed in the bottom of the lake by the fixing 
member 21. The water is led through the water intake port 8 mounted near 
the water surface 9 of the lake waters to the lower part of the fluidized 
bed filter media 13, which is driven by the pressure head difference 
between the water level 9 of the lake water and the water level 10 of the 
upper surface of the fluidized bed. In this embodiment, the purified water 
is taken through the suction pipe 7 by the pump 5, and is discharged 
through the water discharge pipe 6 to the lake water. The discharged water 
is spread out from the nozzle 22 like a fountain. When the pump 5 is 
forcibly stopped, the water level 10 of the upper surface of the fluidized 
bed increases and overflows, and then, the sludge stocked in the fluidized 
bed reservoir moves to the sludge reservoir 20 and can be extracted out by 
the sludge extraction pump 19. In case that the abnormal state in the 
operational conditions of the pump 5 is detected, the alarm lamp 23 is 
blinked, and the abnormal message signal reporting the existence of the 
abnormal state is sent to the facility management office by the 
communication system. 
The purification apparatus for the lake waters in the embodiment of FIG. 4 
is configured the same as the embodiment shown in FIG. 2, in which the 
sewage system is located in a definite position in the lake waters with 
the float 2, the wire 3 and the anchor 4. As the sewage system is floating 
on the water surface with the float 2, the sewage system moves up and down 
responsive to the changes in the water level 9 of the lake waters, and the 
water intake port 8 is kept in a constant position relative to the water 
level 9 of the lake waters. The water is led through the water intake port 
8 mounted near the water surface 9 of the lake waters to the lower part of 
the fluidized bed filter media 13, which is driven by the pressure head 
difference between the water level 9 of the lake water and the water level 
10 of the upper surface of the fluidized bed. The purified water is taken 
through the suction pipe 7 by the pump 5, and is discharged through the 
water discharge pipe 6 to the lake water. A solar panel 18 is used for the 
power source of the pump 5, and the excess electric power is charged into 
a battery. The stored electric power is used for the night-time electric 
power, and thus, the sewage system can be operated in an operation mode 
which is never subject to sun light exposure conditions. In this 
embodiment, the sand filter 14 is placed in the vertical direction. If the 
sand filter 14 suffers from blockage, the purified water to be discharged 
outside through the water discharge pipe 6 is fed back through the reverse 
scrubbing discharge pipe 26 for the internal usage as the reverse 
scrubbing operation in order to increase the second water level 16. With 
this reverse scrubbing operation, the second water level 16 becomes higher 
than the water level 9 of the lake water, and the water flow current in 
reverse direction occurs in the sand filter 14, with which the sand filter 
can be scrubbed. As a result, the filtered materials captured in the sand 
filter can be trapped into the filtered material reservoir 28 by opening 
the reverse scrubbing valve 27. 
The fluidized bed sewage system of the embodiment of FIG. 5 is composed of 
several individual units. In FIG. 5, the sewage system is composed of six 
separate units; the first unit 29, the second unit 30, the third unit 31, 
the fourth unit 32 and the fifth unit 33. As like in the third unit 31, 
the individual unit is composed of fluidized bed contact filter media and 
a container. The lower end of the individual unit connects to the common 
water intake port 34, from which the raw water is taken in, and the 
purified water is discharged from the upper part of the individual unit. 
Thus, as the sewage system is composed of several separate units, the 
designated unit can be replaced partially for the maintenance work, and 
the number of the units to be installed initially and their combination 
can be arranged conditionally according to the allowable initial 
investment. In addition, the necessary additional systems may be allowed. 
As the number of units to be deployed can be adjusted according to the 
area size of the waters to be purified, a mass production of units more 
inexpensive fabrication cost than an integrated model can be achieved. 
If an attempt is made to install the fluidized bed purification apparatus 
directly in the waters, there is no problem when the lake water is 
sufficiently deep. However, in shallow lake waters, as the depth of the 
fluidized bed can not be taken to be larger enough, and as the duration 
time for the contact operation between the raw water and the filter media 
is rather short, the expected purification effect can not be attained. As 
shown in FIGS. 6 and 7, the lake water purification apparatus has a 
multistage configuration including a plurality of fluidized bed 
purification systems arranged in a horizontal direction. Owing to the 
configuration in this embodiment, the duration time for the contact 
operation between the raw water and the filter media can be taken to be 
long enough in proportional to the number of connected purification 
systems. The raw water comes into the first sewage system from the left 
side shown in FIGS. 6 and 7, and is led to the lower part of the fluidized 
bed filter media 13. The purified water moves upward to the upper surface 
of the fluidized bed filter media 13 and is led to the water intake port 
to the second sewage system 36, where the purification operation similar 
to the first sewage system is undertaken, and finally, the purified water 
is discharged to the right side shown in FIGS. 6 and 7. In this apparatus, 
the individual sewage systems are formed in an identical shape, which 
leads to the reduction of fabrication cost as well as establishes the 
optimal control of the density of impurities contained in the purified 
water obtained finally by selecting the optimal stage numbers of sewage 
systems. 
As shown in FIG. 8, the raw water to be processed is transported by the 
first pump 37a and reaches the first tank 38a. As the upper surface of the 
first tank 38a contacts the fresh air directly, the resolved oxygen 
content in the water to be processed increases by the water surface being 
exposed directly to the oxygen in the fresh air. While the processed water 
travels to the upper part of the first fluidized bed 39a connected to the 
lower part of the first tank 38a, the nutrient salt such as phosphate is 
removed from the water in the fluidized bed 39a. The processed water 
reaching the upper part of the first fluidized bed 39a goes through the 
water path 37c, and reaches the lower part of the second fluidized bed 
40a. 
The water discharge power of the second pump 37b is so controlled that the 
water levels may decrease in order from the water level of the first tank 
38a, and the water level of the first fluidized bed 39a to the water level 
of the second fluidized bed 40a, and that the water level of the second 
fluidized bed 40a may be almost equal to the water level of the lake water 
to be purified. In addition, the water level of the processed water is 
raised up to the upper part of the second tank 38b by the second pump 37b. 
The processed water entering the second tank 38b is forced to travel 
through the third fluidized bed 39b and the fourth fluidized bed 40b, and 
is finally discharged outside the purification apparatus. In this 
operation, by making the speed of the flow of water discharged at the 
startup of the apparatus faster than the speed of the flow of the water 
taken into the apparatus, the shortcut flow on the lake waters between the 
water intake part and the water discharge part can be prevented and thus, 
the reduction of the purification performance of the apparatus due to the 
shortcut flow can be avoided. In addition, the operation for increasing 
the speed of the flow of water discharged at the startup of the apparatus 
to be faster than the speed of the flow of the water taken into the 
apparatus can be performed in the stationary operation of the purification 
apparatus if necessary. The sludge stacked in the bottom of the tank and 
the sludge reservoir 20 can be discharged though the sludge extraction 
pipe 41 by the reverse scrubbing operation including opening the reverse 
scrubbing valve 27. 
In this embodiment, the power of the pump is determined so that the total 
amount of waters processed by the purification apparatus in 10 days may 
cover the total amount of raw waters contained in the lake waters. In this 
embodiment, four stages of fluidized beds made of resin materials are 
defined, in which designated water level differences are established by 
controlling a couple of pumps. Thus, owing to the configuration of 
plurality stages of fluidized beds, the purification apparatus can be 
easily transported to the installation site on the lake water. In 
addition, by making the shape of the individual fluidized bed almost 
identical to one another, the reduction of fabrication cost can be 
attained. 
As shown in FIG. 9, a plurality of purification apparatus shown in any of 
FIGS. 1 to 7 are installed in the lake water 42. As shown in FIG. 9, the 
observation apparatus 43 for observing the specified water quality is 
installed in the lake water 42, and the water quality information of the 
lake water is transmitted via wireless communication from the observation 
apparatus 43 and is received by the antenna 45 of the control room 46. The 
water quality information is analyzed in the control room 46, and the 
operation mode of plural purification apparatus and/or the operation 
status are determined and sent back to the purification apparatus 44. By 
repeating this observation and control operation, it will be appreciated 
that the ineffective operation of the purification apparatus can be 
eliminated and that the running cost of the purification apparatus can be 
reduced. 
As shown in FIG. 10, in the purification apparatus for the lake water in 
this embodiment, on the water path from the water intake part 47 along to 
the water discharge part 51, nine units of sewage systems 48a, 48b, 48c, 
49a, 49b, 49c, 50a, 50b and 50c, in which the individual sets of sewage 
systems, (48a, 48b, 48c), (49a, 49b, 49c) and (50a, 50b, 50c), are 
arranged in series. In the following couples of sewage systems, the 
processed water can be exchanged and separated freely by the open-close 
shutters 48a, 49a; 48b, 49b; 48c, 49c; 49a, 50a; 49b, 50b; and 49c, 50c. 
Owing to the configuration shown in FIG. 10, even if, for example, the 
sewage system 48b fails to operate normally and is required to be closed 
under any circumstance, the water path between the sewage systems 48a and 
48b and the water path between the sewage systems 48b and 48c are closed, 
so that the processed water flow can be established from 48a via 49a, 49b, 
49c to 49c in series while the sewage system 48b is bypassed. Thus, even 
if any of sewage systems fails to operate normally, another sewage systems 
operating normally can continue to purify the processed water 
substantially. 
As described above, according to the purification apparatus of the present 
invention, the power loss due to the transportation of raw waters from the 
water area to the purification apparatus site can be reduced by locating 
the purification apparatus directly on the water area. In addition, an 
effective usage of the water area can be achieved, with which the optimal 
position in the water area can be selected for locating the sewage systems 
which can be operated with lower energy, which leads ultimately to the 
maximum effect for operating the purification apparatus. With this 
configuration, in order to consider the water level changes due to rain 
and water discharge, the sewage system floating on the water can be fixed 
in a definite position with a float and an anchor mounted on the sewage 
system, which leads to the shorter distance between the water inlet port 
and the sewage system and the lower process loss in transporting the water 
between them. 
The filtered materials captured in the filter are led to the filtered 
material reservoir by opening the reverse scrubbing valve, and thus, the 
filtered material captured in the filter can be washed out. 
Owing to the above described configuration, the components of the apparatus 
can be replaced with new parts when maintenance work is required, and the 
number of the sewage systems to be installed initially and their 
combination can be arranged conditionally according to the allowable 
initial investment. In addition, any necessary additional systems may be 
allowed. As the number of units to be deployed can be adjusted according 
to the area size of the waters to be purified, a mass production of units 
and more inexpensive fabrication cost than obtainable with an integrated 
model can be achieved. 
In addition to the reduction of the fabrication cost, the density of 
impurities contained in the purified water to be discharged finally can be 
controlled by determining an optimal number of sewage systems. 
As the level of one part of the fluidized bed purification apparatus is 
defined to be higher than the water level of the lake water, the risk of 
the flowing out of the filter media may be estimated to be lower than the 
case in which the sewage system is placed below the water surface. As the 
sewage system is so configured as that the water surface and the fresh air 
may contact each other, the density of the dissolved oxygen in the water 
is increased which is preferable for the biological process for the 
aerobic microbe in the fluidized bed. By installing a tank at the 
preliminary stage of the fluidized bed, the purification apparatus can be 
operated even with a shallow depth of the lake water. By forming the 
fluidized beds in multi stages, the duration time for the purification 
process is not subject to the depth of the lake water, and the expected 
effect of the purification operation can be attained to a reasonable 
extent. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.