Note: Descriptions are shown in the official language in which they were submitted.
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BACRGROUND OF TH~ INVENTION
The present invention pertains to a method and apparatus for
the biological, and also chemical trea~ment of sewage utilizing
aeration, with aeration basins, activator basins in which the sewage
is separated into liquid and concentrated sludge, secondary settling
basins, and means for collecting the settling sludge, all
concentrically disposed within an outer basin.
Apparatus for biological treatment of sewage are known
comprising a number of stages, with an activator stage for separating
liquid from sludge and at least one secondary settling stage for the
sludge to settle. These apparatus have the disadvantage of requiring
a large amount of floor space. Compact sewage treatment flocculation
plants are known (FR-A 1,081,214), in which interaction with a
flocculator takes place in a central basin, while secondary settling
action occurs in a surrounding annular basin. Additionally, a
two-stage treatment power plant is known (CH-A 462,273), in which
treatment of sewage is achieved through precipitation.
It is an object of the present invention to provide a new
and improved method and apparatus for treatment of sewage.
It is also an object of the present invention to provide for
more compact, space-saving treatment of sewage.
It is another object of present invention to provide for
improved relation and disposition of various sewage-treatment stages
with respect to one another.
It is a further object of the present invention to provide
for more uniform loading and reaction during sewage treatment.
It is still another object of the present invention to
provide for reduction of overall volume of sewage to be treated,
while maintaining the same flow rate thereof.
It is still a further object of the present invention to
provide a new and improved method and apparatus for treating sewage,
in which both the activator basin for separating sewage liquid from
sludge and the secondary settling basin are disposed in a single
container.
It is also a further object of the present invention to
provide a new and improved method and apparatus for treating sewage,
in which aeration of the flowing sewage takes place above the
activator basin for separating sewage liquid from sludge by
circulation of the sewage content of the activator basin, and the
secondary settling ba~in functions according to present
classification systems or according to fluidized bed filtra~ion.
These and other objects are attained by the present
invention which provides a method for the treatment of sewage to
separate clear li~uid from sewage sludge, said method comprising the
steps of
separating a flow of sludge from the sewage into a first
flow constituting a major sludge portion to be further treated, and a
second flow constituting excess sludge,
aerating the first flow,
directing the thus-aerated first flow into an activator
basin arranged concentrically in an outer basin, the activator basin
having a conically-shaped basin concentrically arranged therein,
separating liquid from the aerated first flow in the
activator basin to form a more concentrated sludge in the activator
basin,
aerating the thus-separated li~uid and mixing the same with
additional first flow of sludge for further treatment,
directing the more concentrated sludge from the activator
basin to the conically-shaped basin concentrically arranged therein
and subjecting the same to settling therein, thereby forming clear
liquid and further concentrated sludge,
separating the thus-formed clear liquid, and
removing the thus-formed further concentrated sludge.
The present invention also provides an apparatus for
treating sewage to separate clear liquid from sewage sludge,
comprising
an activator basin for separating liquid from a first flow
of sludge thereinto, to form a more concentrated sludge therewithin,
a conically-shaped insert concentrically disposed within tbe
activator basin,
a settling basin concentrically disposed within the
conically-shaped insert and connected with the activator basin in a
manner such that the more concentrated sludge is directed into the
settling basin where the more concentrated sludge is subjected to
settling action,
directing means for directing the settled sludge out of the
settling basin,
separating means for dividing the sludge drawn through the
directing means into additional first flow of sludge constituting a
major portion of sludge to be further treated, and a second flow
constituting excess sludge,
valve means for regulating the first and second sludge flows
and disposed within one of the first and second sludge flows,
aerating means for aerating the first flow of sludge, and
mixing means for mixing the liquid separated within the
activator basin with the aerated first flow of sludge.
In the method according to the present invention, the
further concentrated sludge from the conically-shaped basin (i.e. a
secondary settling basin) is collected at a central location
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therefrom, and preferably by means of a pump, is conveyed to a
separation device such as a centrifugal separator, in which the
sludge is separated into a first flow for further treatment, and a
second flow which constitutes excess sludge and is channeled off.
The first flow of sludge, i.e. the return flow of sludge, is then
aerated before being directed to the ring-shaped activator basin.
Liquid sewage withdrawn from the activator basin, which may be
optionally mixed with fresh sewage feed, is then mixed with the
aerated return flow of sludge from the separation device. This
mixture is then passed to the activator basin, where, after retention
therein to separate out the sewage liquid, the concentrated sludge is
directed into the conically-shaped, secondary settling basin.
In the case where sewage has an especially high biological
or chemical oxygen requirement, the method of the present invention
may be modified in such manner that the activator basin is disposed
discrete sections, with intermixing and especially aeration of the
first flow of sludge, liquid is separated from the activator basin
and any fresh sewage feed occurring in the first such section of the
activator basin. Additional aeration of the combined sewage flow may
take place at the transition of the first section into the second
section of the activator basin, with any degasification that is
required being carried out in the second section of the activator
basin. Finally, the degasified sewage flow is directed by way of a
flow~off conduit into a central sedimentation channel, and into the
secondary settling basin.
In the apparatus according to the present invention, a
conically-shaped or truncated cone-shaped insert (i.e. in the shape
of a funnel) is concentrically disposed within a cylindrically-shaped
activator basin. The point or base surface of the cone-shaped insert
may be disposed at or above the bottom of the activator basin, with a
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substantially cylindrical, secondary settling basin disposed within
the conically-shaped insert. Means for directing the settled sludge
out of the settling basin is disposed within the conically-shaped
insert. Such directing means may comprise a base sludge reamer
and/or a central sludge pit, into which a suction pipe of a sludge
pump extends.
The suction pipe is connected with a pressure conduit, which
is in turn connected to means for dividing the sludge drawn through
said directing means into an additional first flow of sludge, and a
second flow of excess sludge. The separation means may be a
centrifugal separator for example. Additionally, valve means such as
a control valve is provided in the underflow or overflow discharged
from the separation device (i.e. in the first or second flows of
sludge), with means for aerating the first flow of sludge also being
provided. Such aerating means may constitute an aerator annularly
disposed about the activator basin. Additional features of the
present invention are described in more detail below.
The present invention is described in more detail by
reference to the accompanying drawings, in which
FIG. 1 is a side sectional view of a sewage treatment method
and apparatus according to the invention;
FIG. 2 is a top sectional view along line II-II of Fig. l;
FIG. 3 is a side sectional view, similar to Fig. 1, of a
sewage treatment apparatus and method according to another embodiment
of the present invention; and
FIG. 4 is a sectional view, similar to Fig. 2, of the
embodiment of Fig. 3.
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DETAILED Dl~SCRIPTION OF TEil~ PRE:FERRED EMBODIM~NTS
Referring to the figures, a cylindrical basin 1 is
illustrated in Fig. 1, in which a truncated, conically-shaped insert
2 is dispoæed in the ~orm of a funnel, whereby the larger diameter of
the funnel 2 (i.e. the greater base surface) is provided in the area
of the liquid level as illustrated. The smaller base surface of the
funnel is disposed at or just above the bottom of the basin 1. The
arrangement of the truncated portion of the conical insert 2 above
the bottom of the basin 1 facilitates the easy insertion of a base
~ludge reamer 18 at the bottom of an activator basin 3, creating an
annular area whereby the driving gear of the base sludge reamer 18 is
directed through a secondary settling basin 23 formed within the
truncated cone-shaped insert 2.
This secondary settling basin 23 also contains a base sludge
reamer 4 which conveys sludge precipitated within the settling basins
23 into a centrally-disposed sludge pit 5. The deposited sludge is
evacuated from the sludge pit 5 through a suction or evacuation pipe
6 by means of a sludge pump 7. The precipitated sludge is thus
raised above the liquid level of the secondary settling basin 23.
The conical insert 2 is suspended from a bridge 17 above the bottom
of the basin 1, so that the base sludge reamer 18 disposed in the
activator basin 3 can be coupled to a drive of the base sludge reamer
4 disposed in the secondary settling basin 23.
A pressure conduit 8 is engaged with the evacuation pipe 6
above the sludge pump 7, and is also engaged with a separation device
9. The precipitated sludge mass is divided within the separation
device 9 into two partial flows, an overflow 10 and an underflow 11.
This separation device 9 is preferably a centrifugal separator such
as a cyclone. When the centrifugal separator is a cyclone, it has
been found that the more critical bacterial colonies are located in
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377.
the underflow 11, while the number of inactive, dead bacteria in the
overflow 10 is generally greater. Therefore, a regulating valve 12
is disposed in the underflow 11, by means of which the quantity of
the sludge flowing through the underflow or the overflow can be
regulated.
The sludge drained off through the overflow 10 is removed as
excess sludge, while the sludge flowing through the underflow 11 is
then conveyed to an aerator 13 where it absorbs atmospheric oxygen by
flowing past aeration opening~ and becoming saturated or
supersaturated with oxygen. This saturated sludge is then introduced
into a mixing vessel 19, where it is mixed with sewage liquid removed
from the circular activator basin 3. This liquid flowing from the
circular activator basin 3 has also been aerated in a similar
apparatus.
In the case of certain sewage, especially chemical sewage,
the more vigorous bacteria colonies are found in the overflow 10.
Therefore, in this situation, it is the overflow 10 that is aerated,
and the underflow 11 is drained off as excess sludge. Since the
sewage liquid from the activator basin 3 and the sludge have
different oxygen requirements, as well as different reaction times,
the present apparatus allows for optimal gasification to take place.
The intermixed liquid-sludge flow is now channeled to a circular area
16 in which a partial degasification takes place by enlargement of
the free surface thereof. A reaction time for degasification may be
set and determined from the existing statistical settling time.
After suitable degasification, the mixture of liquid-sludge
is once again aerated by a syphon 20 and conveyed to the actual
activator basin 3. The lower opening of the syphon 20 is in the form
of a laterally extending arm 21 ~see Fig. 2) so that the liquid
therein is subjected to rotary motion in the circular area of the
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activator basin 3. ~s a result of this, intermixing is enhanced on
the one hand, preventing sedimentation of the sludge therein, and on
the other hand, a longer settling or reaction time is achieved. The
surface water within the activator basin 3 is collected by way of a
duct 14' and conveyed through a conduit 22 to a central sink channel
15 within the secondary settling basin 23, where ~he actual
separation of sludge and clear water (liquid) takes place. The sink
conduit 15 forms a ring slot 30 within thè settling basin 23 as
illustrated in Fig. 1, with the clear liquid level rising above the
ring slot 30 to the upper portion of the settling basin 23, and over
into the channel 14 n . The clear water is collected in and drained
off through the duct 14" the clear water conduit 24.
The conduits 14' and 14" are preferably formed as a double
conduit 14, with the middle separating wall therebetween extending
above the liquid level as illustrated. An infeed 25 of fresh sewage
liquid expediently takes place through a standpipe 26 of circulating
liquid from the activator basin 3, or by way of a similar device
directly into the mixing vessel 19 which is designed as a common
rising conduit for both the aerated sludge and the aerated sewage
liquid from the activator basin 3.
As illustrated in Fig. 2, the number of aeration components
or recycling conduits is, for example, arranged in three-fold
symmetry. In actual practice, the number of required parallel
conduits may be conveniently determined by any number of factors,
such as economic considerations. Thus, as illustrated in Figs. 3 and
4 a five-fold symmetry is selected, e.g., for a somewhat simplified
construction of components in another embodiment of the present
invention.
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Fig. 3, in contrast to Fig. 1, illustrates mixing vessels 19
separately disposed away from the basin 1. These mixing vessels 19
each have an overflow channel 27 from which the intermixed liquid and
sludge flows through radially-disposed channels 28 with respect to
the cylindrical basin 1, or by way of syphons with repeated aeration,
into the circulator activator basin 3. The truncated conical ins~rt
2 of Fig. 1 has been replaced by a conical, funnel-shaped insert 2'
which is formed with such a pitch that no sludge will adhere to the
walls of the inse~t, and the sludge precipitated within the settling
chamber 23 is directed through the suction pipe 6' by the sludge pump
7.
In this embodiment, the suction pipe 6' is, for practical
purposes, formed as the central sludge pit. The activator basin 3
also has a conical base, with openings 25 disposed thereat for the
suctioning off of liquid from within the activator basin 3 that is
required for aeration. The openings 29 are arranged in the region of
the tip of the conically-shaped bottom of the activator basin 3, as
best seen in Fig. 3. This design eliminates the need for base sludge
reamers in this particular embodiment, thus achieving simplification
of the overall construction of sewage treatment apparatus. In this
situation, a rate control or cutoff device must naturally be
provided. However, it is not absolutely necessary to provide a
channel 14' as illustrated in Fig. 1, since the conduit 22 can be led
directly from the activator basin 3 to the sink conduit 15 in which
the actual separation of sludge and liquid ensues within the settling
basin 23.
The clear liquid within the settling basin 23 then rises
through a ring slot 30 into the upper portion of the settling basin
23, flowing over a dividing wall 31 into the channel 14" from which
the clear liquid is drained off through the conduit 24. The clear
377
liquid drainoff can, as indicated in the figures, ensue by way of a
conduit 24 disposed through the activator basin 3. ~owever, if
emptying of the activator basin 3 is desired, then the clear water
drainoff ensues by way of a syphon connected to the reamer bridge 17
which diverts the clear water from the channel 14~ into a
gutter-shaped clear water conduit (not shown).
As seen from the broken line representation in Fig. 4, the
openings 29 for the sewage liquid from the activator basin 23 which
is to be aerated, are located above a circular area 32 which is
connected by way of a conduit 33 with a circulation pump 34 directing
flow through a riser pipe or pipes to the aeration component. The
present invention is not limited to circular basins, but can also be
analogously applied with respect to rectangularly-shaped basins.
The preceding description of the present invention is merely
exemplary, and is not intended to limit the scope thereof in any way.
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