Note: Descriptions are shown in the official language in which they were submitted.
3 ' 3
A PROCESS FOR THE PRODUCTION OF LIVING AGGLOMERATES CON-
TAINING BIOLOGICALLY ACTIVE MICROORGANISMS
In biological wastewater treatment, powdered active
carbon or lignite coke is often introduced continuously or
semicontinuously as a support material, acting not only as
a support for the biomass, but also - in order to reduce
the sludge index and by virtue of its active surface - as
a buffer for inhibiting, adsorbing wastewater ingredients
(Korrespondenz Abwasser 2, 129-135 (1987)).
However, because very fine carbon particles do not
sediment and are washed out, the use of powdered carbons
leads to the depletion of biomass in the reactor and to the
dissolution of huminic acids and hence to interference with
the operation of the reactor and to pollution of the
treated wastewater. Although the addition of polymeric
flocculation aids leads to the formation of flocs, the
flocs thus formed are not sufficiently shear-stable so that
they are soon redispersed or broken up.
In addition, the carbon continuously added has to be
additionally disposed of with the surplus sludge formed in
the activation stage and, hence, presents another disposal
problem.
The production of agglomerates from film-forming
polymer dispersions and fine-particle fillers is described
in German patent DE 35 26 184. This patent is concerned in
particular with the production of support materials by
mixing of the components in mixing units, such as screw
troughs, kneaders, and by subsequent coagulation, option-
ally using relatively high salt concentrations, changes in
pH or heat treatment and subsequent size-reduction of the
granules obtained which have high dry matter contents.
However, because the production conditions are extreme
so far as living cells are concerned, this method is
unsuitable for the in situ immobilization of living active
Le A 28 257 - Foreiqn Countries
cells.
Accordingly, there was a need for a simple industrial-
ly workable process for the production of biologically
active agglomerates containing living cells which would not
involve any modifications to existing plant and equipment.
There was also a need for higher volume-time yields and
higher process stability.
It has been found in accordance with the present
invention that living agglomerates containing immobilized
microorganisms can be produced relatively easily "ln situ"
in the stirred bioreactor providing the following compo-
nents are mixed with one another:
living, suspended microorganisms which grow under aerobic,
optional or anaerobic conditions,
II.
a powder-form or very fine-particle, solid surface-active
material, such as for example powdered active carbon, low-
temperature lignite coke, lignite, ion exchanger resin,
Al2O3, Fe2O3, Fe3O4, Tio2, CaCO3, bentonite, kaolin, glass
powder, etc. and
III.
an aqueous polymer dispersion capable of film formation/
coagulation.
Relatively large biologically active agglomerates are
formed from the components during the stirring phase and
have a much higher shear strength, sedimentation rate and
useful life than carbon particles covered with biomass or
biomass-containing carbon particles flocculated with poly-
electrolytes. In the context of the present invention, a
"bioreactor" is understood to be a reactor for growing and
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cultivating microorganisms, including biological wastewater
treatment plants (aerobic or anaerobic).
Accordingly, the present invention relates to a pro-
cess for the "in situ" production of living agglomerates
containing active, incorporated microorganisms, charac-
terized in that
an aqueous suspension of an adapted or selective, culti-
vated active biomass capable of growth in pure or mixed
culture with a biomass dry matter content of
0.1 g/l to 15 g/l, preferably
0.15 g/l to 12 g/l and, more preferably,
0.2 to 10 g/l
is introduced into a stirred bioreactor,
II.
2% by weight to 150% by weight, preferably
5% by weight to 120% by weight and, more preferably,
10% by weight to 100% by weight,
based on biomass dry matter, of a powdered or fine-par-
ticle, solid, adsorbing or ion-exchanging substance of
inorganic or organic origin is added with continuous
stirring
and the resulting suspension is intensively stirred with a
quantity - based on its dry matter content - of
III.
0.5% by weight to 30% by weight, preferably
1 % by weight to 25% by weight and, more preferably,
1.5% by weight to 20% by weight
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~ '5 ~
of a film-forming and/or coagulatable, nonionic, anionic or
cationic polymer dispersion having a solids content of 25%
by weight to 50% by weight
for 5 to 20 minutes until readily sedimenting~ compact
agglomerates are formed.
The polymer dispersion consists of an aqueous disper-
sion of polymers which have been produced by polymeriza-
tion, polycondensation or polyaddition and which are pref-
erably dispersed by anionic, cationic or nonionic interr.alemulsifiers incorporated in the polymer chain.
Particularly suitable polymer dispersions are disper-
sions of polymers or copolymers prepared from olefinically
unsaturated monomers, such as acrylonitrile, styrene,
methacrylonitrile, acrylic acid, methacrylic acid, methyl
methacrylate, allyl methacrylate, hydroxyalkyl acrylate,
N,N-dimethylaminoethyl methacrylate, acrylamide, ethane,
propane, vinyl chloride, vinyl acetate, 1,3-butadiene, 2-
methyl-1,3-butadiene,2,3-dimethyl-1,3-butadiene,2-chloro-
1,3-butadiene and p-divinylbenzene.
To produce the agglomerates according to the inven-
tion, component II (additive) is initially introduced into
the bioreactor containing the suspended biomass I and,
after it has been thoroughly distributed throughout the
entire volume of liquid, component III (dispersion) is
added with intensive stirring, the intensive stirring being
continued for another 15 to 20 minutes until the formation
of readily sedimenting agglomerates is complete.
The process according to the invention is particularly
advantageous in cases where strains of relatively low floc-
culation capacity or strains which form slowly sedimenting
flocs, such as for example the nitrifying bacteria Nitroso-
monas and Nitrobacter~ and other strains capable of miner-
alizing slowly degradable organics, such as Pseudomonas,
Flavobacterium, Rhodococcus, etc., are to be agglomerated.
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The process according to the invention is also suit-
able for the agglomeration of cultures growing under
optional and aerobic conditions, such as for example for
the acidogenic and methanogenic microorganisms Methano-
sarcina, Methanothrix, etc.
The agglomeration process according to the invention
has several advantages over the various immobilization
processes. It can be carried out very simply with gradual
addition of non-toxic components to the bioreactor itself
under standard reaction conditions, i.e. no drastic changes
in pH, controlled temperature increases, increases in ionic
strength by salt additions and with no addition of toxic
crosslinking or curing agents.
The "product" i.e. the agglomerates, remain in the
reactor and are not subjected to any other additional
process steps, such as separation, drying and siæe-reduc-
tion, applied in the production of other supports and may
be directly used as such.
In addition, no extra equipment or installation or
modification work is required for the circulation, aeration
and retention of the agglomerates.
The application of the agglomeration process according
to the invention also affords several advantages in terms
of process technology, including for example a reduction in
the sludge index, improved fluidiæability, increased
process stability and higher volume-time yields, which in
practice provides for stable, problem-free management of
the process.
Since the agglomerates sediment more quickly than the
suspended sludge flocs, they enter the following settling
tanks in smaller numbers, which in practice means an
increased residence time of the biomass in the reactor.
This is a crucial advantage, particularly in processes with
slow-growing biomass.
By virtue of the greater adhesion of the components,
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;~?~ 3
the agglomerates according to the invention show increased
dimensional stability in relation to biomass/carbon flakes
flocculated with linear flocculation aids based on poly-
acrylamide, which also leads to high process stability.
5 The improvement in process stab:ility in biological waste-
water treatment is of particular value when the composition
of the wastewater changes or variations in load occur. In
cases such as these, the situation can be remedied by
problem-oriented (in regard to the microorganism strains
10 used), temporary and automatically controlled application
of the process according to the invention.
Latex types
The following aqueous polymer dispersions may be used
as component III:
Latex A: anionic polymer, 40% dispersion, of butadiene,
acrylonitrile and methacrylic acid in a ratio by
weight of 62:34:4
Latex B: anionic polymer of butadiene, styrene and acrylic
acid in a ratio by weight 41:56:3
5 Latex C: polymer of butadiene and styrene in a ratio by
weight of 68:32
Latex D: cationic polymer of butadiene, styrene and
cationic co-monomer in a ratio by weight of
38:58:4.
The invention is illustrated by Examples 1 to 5.
Whereas the production of agglomerates and the higher
sedimentation rates achieved are illustrated in Example 1
35 with no biological application, Examples 2 and 5 are
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primarlly concerned with the increase in biological activ-
ity and process stability by agglomeration.
Example 1
Quantities of 1,000 ml biomass suspension containing
4 g~l nitrifying microorganisms (component I) are intro-
duced into five 2,000 ml capacity glass beakers e~uipped
with magnetic stirrers. Quantities of 1 g of component II
and then 0.1 g polymer dispersion (component III) are added
with intensive stirring. Agglomeration is complete after
about 15 minutes. The sedimentation rates and sludge
volumes of the agglomerates are determined in a graduated
1,000 ml measuring cylinder. The results are shown in the
following Table:
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2a'~ 3
Test Component ComponentSludge volume (ml/l)
II IIIAfter 4 8 16 30
mins. mins. mins. mins.
a) Non-immobilized biomass 740 540 430
A b) Low-temper- Latex A 610 415 335
ature lignite
coke
a) Non-immobilized biomass 700 380 280
B b) Low-temper- Latex B 480 310 240
ature lignite
coke
a) Non-immobilized biomass - 485 465
C b) Low-temper- Latex B - 465 430
ature lignite
coke
c) CaCO3 powder Latex D - 410 315
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Example 2
(Nitrification of an ammonium-rich wastewater)
Two aerobic treatment plants operated in parallel and
consisting of 7-liter aerated b:ioreactors followed by 3-
liter secondary sedimentation tanks with recycling of
sludge are inoculated with an activated sludge suspension
containing 4 g/l nitrifying biomass dry matter and contin-
uously charged with a synthetic wastewater containing 1,400
to 2,000 mg/l NH4-N, 500 to 1,000 mg/l ethanol, 300 mg/l
phenol and 500 mg/l 2-naphthalenesulfonic acid in order to
be able comparatively to investigate the nitrification of
this wastewater containing suspended microorganisms (reac-
tor A) and immobilized microorganisms (reactor B).
After addition of the biomass, 9 g/l neutralized low-
temperature lignite coke powder ("Braunkohlenfeinstkoks":
product name of Rheinische Braunkohlenwerke AG, Cologne,
Germany) and - with intensive air circulation - 0.5 g/l
latex A containing 40~ dry matter are introduced into
reactor B.
After about 10 minutes, the slightly foaming, milky
aqueous phase becomes clearer so that the agglomerate
particles are readily discernible.
Over the first few days, the two plants operated in
parallel are operated at an NH4-N space load of 0.3 to 0.4
g NH4-N/l day, after which the load is successively
increased. The results of the test which runs continuously
for 83 days are set out in the following Table:
As the results show, a high level of nitrification and
high process stability can be achieved by agglomeration
(immobilization) of the microorganisms at considerably
higher NH4 space loads.
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~ ~? ~ 3
Test Reactor N space load NH4-N concen- % Elimin-
day g NH4-N/l day tration (mg/l) ation
Influent Effluent
A 0.8 820 5 99.4
B 1.2 820 5 99.5
31 A 1.38 1420 160 88.7
B 1.42 1420 5 99.6
A 1.82 1730 240 86.1
B 1.82 1730 5 99.7
47 A 2.1 2120 630 70.3
B 2.15 2120 10 99.5
Example 3
The two 7-liter capacity aerobic plants operated in
parallel described in Example 1 are each inoculated as in
Example 1 with 4 g/l suspended nitrifying biomass. The
biomass in reactor B is immobilized by addition of 1 g/l
low-temperature lignite coke and 0.1 g/l latex A containing
40% dry matter.
A mixture of 60 to 80% by volume neutralized mixed
chemical wastewater and 20 to 40% communal sewage con-
taining 80 to 120 mg/l NH4-N was used as the substrate.
The two reactors were operated substantially in
parallel, i.e. the hydraulic residence time and the NH4-N
space load were substantially the same in both reactors.
The results of the test are shown in the following Table:
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Test Reactor N space load NH4-N concen- ~ Elimin-
day g NH4-N/l day tration (mg/l) ation
Influent Effluent
11 A 0.11 90 97
14.04 B 0.11 90 58 35.6
48 A 0.12 89 62 30.3
18.06 B 0.12 89 9 89~9
187 A 0.13 104 65 37.5
09.10 B 0.14 104 3 97.1
Whereas nitrification could never be properly "estab-
lished" in reactor A, it proceeded very stably and with
high conversion rates in reactor B after an adaption phase
lasting approximately 3 weeks.
Example 4
(Nitrification of communal sewage)
Two 25-liter aerobic plants operated in parallel are
each inoculated with 4 g/l nitrifying biomass. The biomass
in reactor B is immobilized by addition of 1 g/l low-
temperature lignite coke and 0.1 g/l latex A. The sub-
strate used is mechanically preclarified communal sewage to
which 50 mg/l NH4+-N were added in addition to the natural
NH4t-N content. The results of the nitrification test are
set out in the following Table:
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~q~3`~ ~3
Test Reactor N space load NH4-N concen- % Elimin-
day g NH4-N/l day tration (mg/l) ation
Influent Effluent
-
1 A 0.40 93 11 88.5
B 0.41 93 10.2 89.0
7 A 0.36 82 15.0 81.3
B 0.38 82 5.4 93.4
17 A 0.42 95 64 32.6
B 0.42 95 8.5 91.1
27 A 0.50 120 48 56.4
B 0.50 120 18 85.0
Example 5
Two anaerobic plants operated in parallel each con-
sisting of an 8.7 liter capacity, thermostatically control-
led, stirred methane reactor, siphon and gas burette are
each filled with anaerobic sludge containing 10 g/l biomass
dry matter. 2 g/l quartz sand and - with intensive stir-
ring - 0.2 g/l latex G are introduced into reactor B.
After stirring for 15 minutes, the plant is cor.tinuously
charged with a mixed wastewater (vapor condensates + alkali
extract from chlorine bleaching) from a sulfite pulp
factory. The results of the continuous anaerobic treatment
tests are set out in the following Table:
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U ~ 3
Test Reactor COD space load COD (mg/l) % Elimin-
day g COD/l day Influent Effluent ation
A 0.95 5330 1760 67.0
B 0.95 5330 1390 73.9
A 5510 2330 57.7
1.12
B 5510 1780 67.7
23 A 1. 23 5330 1961 63.2
B 1.23 5330 1270 76.2
58 A 1.6 4890 2820 42.3
B 1.6 4890 1700 62.2
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