Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to an improved installation ~or the anaerobic
purification of waste or effluent water comprising organic decomposable im-
purities.
m e installation comprises a reaction or decomposition zone into
which waste water comprising impurities is fed.
It is known, that waste water comprising decomposable organic sub-
stances can be purified by an anaerobic microbial decomposition process, wherebymethane and carbon dioxide are being formed.
The use of this process for the direct purification of waste water,
particularly of concentrated industrial effluent water has been tried, but it
sho~-ed several disadvantages. A stable fermentation process can hardly be
obtained, and a useful practice comparable with aerobic purification could not
be realised in a technical scale. In the ~ournal ~'H20"(1974), Nr. 7, pp. 281-
289 the state of the art has been given, with a comprehensive literature
; reference.
It has been described in said publication, page 281, that in using
a methane-developing fermentation for the treatment of less concentrated waste -
water (having 0.1 through 0.5% by weight of organic matter), one of the most
important problems i3 to find a practically acceptable ~ay for separating the
sludge. A stable methane-developing fermentation can be accomplished in a
continuous way only if the total amount of active bacterial material in the
reactor can be maintained at a constantly high level.
On page 283, Figure 1 of said publication an experimental device
is shown, wherein a setting zone next to and at the top of a recipient for the - -
interception of the gas is provided, said recipient at its lower side having
a circular opening, which serves as the inlet as well as the outlet of the
after-settler. With such a device a stable and continuous process cannot be
achieved.
The problems reflected, which relate to the experiences as described
with an experimental device having a contents of 16 liters are being still more
severe with industrial reactors having a volume of dozens or several hundreds
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of cubic metres.
In the existing conventional sludge fermentation tanks e g. a reten-
tion period of the entire mixture of about 30 days is a normal feature. For
an efficient purification of waste water this sludge retention period (i.e.
life-time of the sludge) might not be made shorter (at least 10 days, see the
above publication, page 287 at the bottom), while at the same time the rete~-
tion period of the liquid should be reduced to several hours (viz. 3 through
6 hours). An effective purification can be achieved in such a short period
only if relatively high concentrations of sludge are present in the reactor
(i.e. dozens of grams per liter). In order to obtain this, an eff~ciently
working system is necessary, wherein the following requirements are met-
~1. The ascending gas bubbles are being collected, and the gas will be removed
efficiently, such that no foam or liquid droplets will be entrained.
2. The liquid is separated from the mixture of sludge and liquid in such a
way that a substantially sludge-free effluent will be produced.
3. me sludge separated from said liquid will be concentrated and be recycled
into the reactor zone at the highest possible rate.
The separation of sludge and effluent in the conventional aerobic
purification system is in general carried out by means of an after-settler
separate from the aeration zone, and the concentrated sludge is recirculated
into the aeration zone through a conduct by means of a pu p or by other means.
Since in aerobic systems considerable sludge formation is obtained,
part of the concentrated sludge is cocurrently removed from the system (gutter
sludge).
This is entirely different from anaerobic purification, for the
followine reasons:
; a) In view of minor sludge formation only small amount of sludge has to be
removed.
b) There is no need for using the underflow of the after-settler in order to
obtain a concentrated gutter sludge, since at the bottom of the reactor there
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exists a very high sludge concentration as a result of the good settling
properties of the anaerobic sludee.
c) m e retention period of the sludge outside the reactor ought to be
restricted to a minimum, because otherwise gas formation and flotation might -- -
occur, such that the function of the settler device would become inefficient.
Several attempts to use anaerobic purification on industrial scale
have failed, substantially for reasons of the issue mentioned in the last-
above passage.
It is an ob~ect of the present invention to comply with the require-
ments as mentioned in the above under 1 through 3, without occurrence offlotation and of other proble~s.
It is a further ob~ect of the present invention to obtain the
following advantages:
- Simple construction
- Easiness of access to all constructional parts
- Absence of moving constructional parts, including recycling pump devices
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- Possibility of an optimal adaptation of the installation to the typical
properties of a certain envisaged type of waste water and of sludge, as well
as to the input ch~rge, by a proper selPction of the mutual ratios of
dimensions and by a control or adjustment of the inlet-opening or openings
of the settler-device.
- A continuous process.
Still another object of the present invention is to provide a
compact efficient installation for the anaerobic purification of industrial
and/or domestic waste waters or effluents.
Other objects will be elucidated by the specification in detail
of the invention, by the Figures enclosed and by the claims.
Detailed specification of the invention:
In order to comply with all the requirements mentioned in the
above, use is made according to the present invention of the principle, that
a column of a liquid in which gas-bubbles are present, will have a lower
specific weight than a liquid without such bubbles.
This principle, upon which the known device of the mammoth pump
is based, renders a number of specific advantages as well as disadvantages
as compared with other types of pumps, and it is used only in special fields.
Surprisingly, it has been found according to the present invention
that this principle can be used to transport the liquid from the anaerobic
reactor zone into the after-settler compartment and to recycle the sludge
back into the reactor, without an input of energy and without moving
mechanical parts.
According to the present invention, there is provided an installation
for the anaerobic purification of effluent or waste water by means of an
anaerobic reactor, comprising a reactor tank or container with an after-
settling compartment in an upper part thereof for separating sludge and liquid,
characterized in that said after-sett~ng compartment comprises a supply open-
ing for entry of a mixture of sludge and liquid from a reactor zone in the
reactor tank and a lower-positioned outlet opening to said reactor zone,
whereby the sludge, separated by settling in the after-settling compartment
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returns with liquid into said reactor zone, while deflecting means is
provided in the reactor zone, which shields the supply opening and the outlet
opening to and from said after-settling compartment respectively so that
upward flow of developed gases is kept away from said openings, a shield
for said supply opening being positioned much higher than said outlet opening
so that developed rising gas entrains liquid and sludge upwardly to said
supply opening in the reactor zone to cause circulation of liquid and
sludge into and from the after-settling compartment and from and into the
reactor tank respectively, separate interception and outlet means for said
developed gases permitting an amount of anaerobic sludge to be continuously
separated and recycled such that the purification process by fermentation
proceeds continuously and equably.
In another aspect, the invention provides a pTocess for the anaerobic
purification of effluent or waste water in a reactor tank, comprising having
gas generated by fermentation of bacteria therein flow upwards so as to lift
water and sludge to an inlet opening to an after-settling compartment in an
upper part of the reactor tank, separating the gas from said water and sludge
near said inlet opening so that the gas is guided away from said inlet open-
ing and water and sludge flow through said opening into the after-settling
compartment, withdrawing purified water from an upper part of said compartment
and allowing sludge settled in the after-settling compartment to flow back
into the reactor tank through a discharge opening in the bottom of the after-
settling compartment at a distance below said inlet opening, deflecting
rising gas below said discharge opening so as to prevent it from rising
therethrough into said after-settling compartment, generating a circulation
of water and sludge from the reactor tank into said after-settling compartment -
and said sludge returning from said compartment into the reactor tank by means
- of said gas flowing upwards in the reactor tank.
The installation is preferably provided with means for the control -
and adjustment of the height of the inlet openings of the after-settler.
The inlet opening into the after-settler is positioned in top of
a shielding bulkhead which conducts the ascending gas bubbles in a direction
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at the side of the horizontal projection of said inlet opening into the
interception zone for same, while the liquid with sludge is allowed to flow
around said bulkhead to the inlet opening.
The outlet opening at the bottom of the after-settling compartment
is positioned higher than the bulkhead which is placed oblique or horizontally
in the reactor zone and which prevents the ascending gas bubbles to reach the
outle~ opening.
Over the bulkhead is a vertical channel a vertical wall of which
being substantially protruding into an overflow to the after-settler compart-
ment, said wall under said overflow forming an intercepting zone with thewall of the after-settling compartment, wherein the gas is intercepted and
from which the gas can be removed under controlled overpressure.
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The after-settline compartment is widening in a conical way in the
upward direction and it has at its top a zone to collect foam which is open
at its lower side, and delimited by a wall, into which protrude one or several
tubings, leading from that wall of said after-settling compartment in an oblique
way upward until said delimiting wall, such that inlet openings are formed for
the mixture of sludge and water to pass into said after-settling compartment.
The installation comprises ad~ustable means for the control of the
height of the inlet opening for the mixture of sludge and water to pass into
the aM er-settling compartment.
One or several tubes may be constructed in a sliding way movable
along their longitudinal axis such that the height of the inlet opening from
the reactor zone into the after-settling compartment at the end of said tubes
protruding into said reactor zone may be varied in a controllable way said
sliding tubes are positioned in fixed tubes which extend from the wall of the
after-settling compartment to the wall of the foam collecting zone.
From German Patent Specification 275,498 an installation is known
for the treatment of waste water sludge, in which the fresh sludge is mixed
with Permented sludge. In a reaction compartment a mixing funnel can be placed
in such a position that the installation shows some resemblance to the instal-
lation according to the present invention.
However, in this device according to German Patent Specification
275,498 the fresh sludge is directed into the mixing funnel, flowing out of
same at the bottom and is mixed with fermented sludge, and the ascending gas is
substantially directed to the bottom of said funnel in order to improve the
sludge mixing.
The invention is further explained with reference to the en~losed
drawings, which represent a schematic view of the installations with devices
according to the present invention, and which are given only by way of example
and should not be regarded as a limitation.
In these drawings, the following is depicted:
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Figure 1 shows a radial sectional view of a cylindrical installation
which is an embodiment of the invention.
Figure 2 shows a prespective view of a rectangular installation
which is an embodiment of the invention.
Figure 3 shows a longitudinal sectional view of another rectangular
embodiment of the installation according to the invention, wherein a gutter
channel is positioned between the 2 compartments of the after-settling
compartment.
In these figures the following parts are shown:
1 - reactor wall
2 - wall of the after-settler
3 - conducts forming the inlet openings into the after-settler
4 - zone for collecting foam
5 - bulkhead under inlet openings --
6 ~ bulkhead under outlet openings
7 - gas conveyance
8 - over flow drain
9 - gas collecting zone
10)- horizontal planes wherein between the liquid columns 12 and 13 are
113 positioned
12 - column of liquid in the after-settler with much sludge and without gas
bubbles
13 - column of liquid outside of the after-settler having less sludge but
with gas bubbles
The after-settling compartment in Figure 1 has the shape of a
circular funnel or knotted cone with an angle of slope of e.g. 45 having an
opening 14 at its lower side. In said funnel openings 15 may be present at
e.g. four positions, wherein the conducts 3, in this example cylindrical pipes,
have been fixed. In Figure 1 also for this item a slope angle of 45 has been
selected such that the axle of the pipes is perpendicular to the wall of said
funnel. However, this is not obligatory for the function of the device. The
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four pipes 3 reach into the central zone 4 which is open at it3 l~wer an~
upper sides.
Under each pipe 3 there is a bulkhead 5 e.e. consisting of a semi-
cylindrical piece of pipe which prevents gas bubbles ascendine to reach into
the pipes 3, since said bubbles during said ascending are directed into a
direction outside the reach of the openings 15 by means of the bulkhead shield-
ing.
Under the opening 14 of the funnel a shape 6 is positioned, which is
made of two conical parts. By this shape ascending gas bubbles are directed
to the s~de outside the reach of the opening 14; also the recycling of the
sludge from zone 2 into the reactor is directed in a controlled way.
m e reactor wall ~ has not been depicted much lower than the bulkhead
5, however, this zone is extending lower in a distance of 2 to 4 meters, viz.
at least in a distance of the same height as that of the after-settling compart-ment 2. At the bottom of the reactor compartment there is an inlet for the
waste water to be treated, which might be sub~ected to a prepurification, and
furthermore there is an outlet for drawing off and cleaning of the installation,said outlet may be closed during normal function of the installation.
me function of the installation is as follows: -
An amount of water with active sludge for anaerobic decomposition is
fed into the Peactor zone of the tank and continuously waste water to be purified
is added. By the fermentation reaction gas bubbles are being formed in the
liquid and the impurities of the waste water are gradually decomposed into
methane and some carbon dioxide and water. m e gas functions as a bubble pump,
; and around the after-settling compartment 2 an upward effect is carried out in
the liquid. Thus said liquid is flowing with part of the sludge through open-
ings 15 into the conducts 3 and therefrom into the foam collecting zone 4,
where the foam is floating upon the liquid and may be removed either by skimming -
means or by separate (not depicted) overflo~ or by chemical agents. Water and
- 30 ~ludge drop into the funnel of the after~settling compartment, and at the bottom
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of the funnel a higher concentration of sludge is effected. The mixture leaves
the funnel 2 through opening 14.
The ascending gas bubbles do not flow with the liquid into the open-
ings 15 but are directed with liquid around the shielding bulkhead 5, such that
the liquid can reach said opening but the gas bubbles rise till the zone 9
wherefrom the gas is carried off through the gas exit 7 under a certain over-
pressure which is sufficiently high to have some gas remaining in the zone 9,
~n spite of the higher liquid level in the after-settling zone 2.
The circulation of the liquid and the sludge as described takes place
mainly by the difference in specific gravity of the mixture of water sludge and ~-
gas bubbles in the zone between the level lines 10 and 11, i~.e. over the column
12 ~ithin the after-settling compartment 2 and the column 13 outside of this
compartment in the reactor~ Within the after-settling compartment an ascending
liquid flow is superposed upon said circulation movement, whereby the liquid in
the foam collecting zone 4 flows downward and splits into two flow streams in
the lower part; this results in a descending flow to the opening 14 with the
concentrated sludge and an ascending flow around the zone 4 to the overflow ô,
and said fl~ i compensated by the waste water to be treated which is fed at
the b~ttom of the installation.
The flow due to the overflow 8 will arrive in a zone which is gradual-
ly widening in a direction to the top, and thus the flow rate is decreasing,
with the result that the liquid will be stripped of sludge particles in an
efficient way.
Into the conduct pipes 3 inner pipe 16 may be telescoped, which may
be pushed in the conduct pipes and back, in order to vary the height of the
inlet openings 18 at their lower ends, such that an inherent circulation in
the natural manner can be ad~usted and controlled as described in the above.
In Figure 2 a rectangular reactor tank is depicted, in this figure
the front and back walls are omitted, as well as the lower part of the reactor
tank, for a better understanding of the invention.
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In said lower part of the reactor tank there is an inlet for the
waste water to be treated, and this lc~er part i8 about as hiBh as the part of
the installation displayed.
In this embodiment as shown, the bulkheads 5 and 6 for directing the
gas bubbles are made in the form of straight shaped beveled bodies of sheet
material as shown in the drawing, said bulkheads shielding the rectangular
openings 14 and 15 in top of them from ascending gas bubbles, such that said
bubbles cannot reach the zone 9 and cannot ascend inside said openings 14 and -~
15. Another bulkhead 19 forms a separation between the surface of the foam
collecting compartment 4 and the surface of the compartment from which the
purified effluent is drained through the overflow gutter 8. Vertically ad~ust-
able bulkheads 20 and 21 are used for the control of the supply into the after-
settling compartment and the removal from the reactor zone through opening 15.
In Figure 3 two after-settling compartments 2 ad~acent to each other
are depicted, which may have either circular or rectangular horizontal sectional
shapes. At the ad~acent sides there are vertical conduct pipes 3, in the cen- ~ -
tral part a mutual conduct channel 3 for both after-settling compartments,
further this installation is in principle substantially equal to that as shown
in Figures 1 and 2. -~,
Further to these embodiments other types can be constructed, wherein
the use of the same principle as the above is applied, since said principle may
be used for general applications in several different kinds of constructions of
after-settling installations.
The following example is described for the understanding of one
particular embodiment of such an installation according to the present invention.
Example:
i In a cylindrically shaped reactor tank having a contents of 6 m3 an
after-settling device according to Figure 1 had been assembled. The distance
between both horizontal planes 10 and 11, which caused the effect of the sludge
after-settling device, was 25 cm. Into this reactor sludge waste water was
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supplied at the sump of the tank with a rate of 1 m3 per hour. m e chemlcal
oxygen demand (C.O.D.) of the supplied fluid was 3000 gram per m3 The reten-
tion time was 4 hours.
Initially into this reactor a sludge had been supplied as an inocu-
lating material from a sludge fermentation tank of a municipal waste water
purification installation. After a short period of adaptation the amount of
gas developed was 1 m3 per hour comprising about 90% by volume of methane
(natural gas).
me growth or increase of sludge was very small, which is inherent
to anaerobic decomposition, it appeared to be practically possible to separate
the sludge from the flow in such an efficient way that a concentration of 35
through 40 gram organic sludge material per liter fluid could be maintained in
the reactor.
m ere were no disturbances in continuous operation, and the efficacy
has been proven by the fact, that at a retention time of 4 hours of the liquid -
a retention time of the sludge material of 25 days was observed.
mus, in a very economical way a purification of waste water has been
obtained by means of the installation according to the present invention, while
methane had been recovered, which could be used as an energy source.
me purified water showed the properties as required by environmental
authorities.
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