CA2062843A1 - Process for the production of living agglomerates containing biologically active microorganisms - Google Patents

Abstract

A PROCESS FOR THE PRODUCTION OF LIVING AGGLOMERATES CON-TAINING BIOLOGICALLY ACTIVE MICROORGANISMS

A B S T R A C T

To produce living agglomerates containing active, incorporated microorganisms or enzymes, an aqueous suspen-sion of an adapted or selective, cultivated 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 is introduced into a stirred bioreactor, 2% by weight to 150% by weight, based on biomass dry matter, of a powdered or fine-particle, 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 0.5% by weight to 30% by weight of a film-forming and/or coagulat-able, 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.

Le A 28 257 - Foreign Countries

Description

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 Le A 28 257 - Foreian Countries 2 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 Le A 28 257 - Foreian Countries 3 ~ '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.

Le A 28 257 - Foreign Countries 4 ;~?~ 3 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, Le A 28 257 - Foreiqn Countries 5 ;~?~ 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 Le A 28 257 - Foreiqn Countries 6 ~?~ '3 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:

Le A 28 257 - Foreiqn Countries 7 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 Le A 28 257 - Foreian Countries 8 ;~?~ 3 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.

Le A 28 257 - Foreign Countries g ~ ~? ~ 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:

Le A 28 257 - Foreign Countries 10 ~?~ 3~

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:

Le A 28 257 - Foreiqn Countries 11 ~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:

Le A 28 257 - Foreiqn Countries 12 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 Le A 28 257 - Foreiqn Countries 13

Claims (6)

1. A process for the "in situ" production of living agglomerates containing active, incorporated microorganisms (and/or enzymes), characterized in that I.
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 of a film-forming and/or coagulatable, nonionic, anionic or Le A 28 257 - Foreign Countries 14 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.

2. A process as claimed in claim 1, characterized in that Nitrosomonas, Nitrobacter, Pseudomonas are used as micro-organisms for the nitrification of ammonium.

3. A process as claimed in claim 1, characterized in that Pseudomonas, Flavobacterium, Bacillus, Rhodococcus, etc., and mixtures thereof are used as microorganisms for miner-alizing slowly biodegradable substances under optional or aerobic conditions.

4. A process as claimed in claim 1, characterized in that Methanotrix, Methanosarcina and other methanogenic organ-isms or mixtures thereof are used as microorganisms for the methanization of suitable organic substrates.

5. A process as claimed in claims 1 to 4, characterized in that film-forming and coagulatable polymer dispersions based on olefinically unsaturated monomers are used as the aqueous polymer dispersions.

6. The use of the agglomerates obtained by the process claimed in claims 1 to 5 in biological wastewater treatment and in bioconversion processes.

Le A 28 257 - Foreign Countries 15