NL2019171B1 - Method and system for production of natural polyelectrolytes such as microbial extracellular polymeric substances - Google Patents

Description

Octrooicentrum Nederland © 2019171 (2?) Aanvraagnummer: 2019171 © Aanvraag ingediend: 4 juli 2017 © B1 OCTROOI

Int. CL:

C02F 1/52 (2017.01) C02F 1/56 (2017.01) C02F 11/14 (2017.01) C02F 1/38 (2017.01) C02F 1/42 (2017.01) C02F 1/469 (2017.01) C02F 3/12 (2017.01)

0 Aanvraag ingeschreven:	© Octrooihouder(s):
14 januari 2019	Stichting Wetsus, European Centre of
	Excellence for Sustainable Water Technology
© Aanvraag gepubliceerd:	te LEEUWARDEN.
© Octrooi verleend:	© Uitvinder(s):
14 januari 2019	Bernard Gerhard Temmink te LEEUWARDEN.
	Victor Olusola Ajao te LEEUWARDEN.
© Octrooischrift uitgegeven:
8 mei 2019
	© Gemachtigde:
	ir. P.J. Hylarides c.s. te Den Haag.

(54) METHOD AND SYSTEM FOR PRODUCTION OF NATURAL POLYELECTROLYTES SUCH AS MICROBIAL EXTRACELLULAR POLYMERIC SUBSTANCES © The present invention relates to a method and system for the production of natural, biodegradable polymeric flocculants from a fluid, such as a waste fluid, such flocculants and their use. The method comprising the steps of:

- providing a reactor comprising at least one reactor vessel, one fluid inlet, one fluid outlet, one flocculant outlet, and at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet;

- inoculation of the reactor;

- providing feed to the at least one fluid inlet;

- forming the flocculants;

- separating the flocculants using the membrane; and

- providing the flocculants at the flocculant outlet.

NL B1 2019171

Dit octrooi is verleend ongeacht het bijgevoegde resultaat van het onderzoek naar de stand van de techniek en schriftelijke opinie. Het octrooischrift komt overeen met de oorspronkelijk ingediende stukken.

METHOD AND SYSTEM FOR PRODUCTION OF NATURAE POLYELECTROLYTES

SUCH AS MICROBIAL EXTRACELLULAR POLYMERIC SUBSTANCES

The invention relates to a method for the production of natural, biodegradable polymeric flocculants from a fluid, lor example a waste fluid. For example, the method discloses the manufacturing of microbial Extracellular Polymeric Substances (EPS) that can be applied as flocculants for waste fluid treatment or other fluids containing (colloidal) particles.

It is known from practice to use carboxyl cellulose flocculants and (biodegradable) flocculants. Conventional production methods for these flocculants include EPS production strategies involving identification and isolation of EPS producing microbial strains with single organic substrate feeding. Conventional EPS production uses pure cultures which need to be fed with expensive and unsustainable carbon sources as well as with other valuable nutrients.

From practice it is also known to use inorganic coagulants that are cheap and easy to use. However, inorganic coagulants do not flocculate efficiently at low dosages, are non-specific, leave residual metal pieces in treated water, and produce toxic sludge (metal hydroxide). This makes disposal of this sludge difficult, expensive and non-reusable, for example in agriculture and, therefore, the associated food chain. Synthetic organic polyelectrolytes (Pes)/flocculants, have higher flocculating efficiency, lower dosage requirements, ability to dewater sludge more effectively, and can form strong and dense flocs. Nonetheless, they suffer non-negligible drawbacks of slow' biodegradability and generation of toxic degradation products/monomer residues that may enter the food chain and cause severe neurotoxic or carcinogenic effects. Besides, unreacted chemicals used to synthesize lite monomer units, such as formaldehyde, epichlorohydrin and dimethylamine, are toxic and have been found as sources of contaminants in ‘treated’ water. Hence, the use of synthetic flocculants can hardly be considered a sustainable wastewater treatment approach, especially in open systems such as dredging and mining applications.

An objective of the present invention is to provide a method for the production of natural, biodegradable polymeric flocculants from a waste fluid that obviates or at least reduces the aforementioned problems and/or is more efficient as compared to conventional methods.

The objective is achieved with the method for the production of natural, biodegradable polymeric flocculants from a fluid, such as a waste fluid, according to the invention, the method comprising the steps of:

- providing a reactor comprising:

- at least one reactor vessel:

- at least one fluid inlet;

- at least one fluid outlet:

- al least one flocculant outlet; and

- at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet;

- inoculation of the reactor;

- providing feed to the at least one fluid inlet;

- forming the flocculants:

- separating the flocculants using the membrane: and

- providing the flocculants at the flocculant outlet.

Production of natural, biodegradable polymeric flocculants from a fluid, such as a waste fluid enables cost, effective manufacturing. This is achieved by the use of readily available raw material for the manufacturing process. The flocculants can be used for waste fluid treatment and/or treatment of other fluids containing (colloidal) particles. This use of the flocculants will therefore be cost effective and cheap to use. In presently preferred embodiments the fluid relates to fluids such as a waste fluid.

In the context of the present invention waste fluids include fresh and saline waste fluids, for example. The waste fluid could be obtained as domestic waste fluid and/or industrial waste fluids. Examples of industrial waste fluids are waste fluids from chemical industry, agriculture industry, food processing industry, pharmaceutical industry and health care industry.

In the context of the present invention EPS relates to Extracellular Polymeric Substances and includes organic matter such as flocculants.

Microbial Extracellular Polymeric Substances (EPS) applied as flocculants are generally considered as biopolymers excreted by micro-organisms. These microbial EPS are products of biochemical secretion and/or cell lysis.

The production of flocculants is performed in a reactor vessel. Preferably, the reactor vessel comprises a volume such that the hydraulic retention time is below 6 hours, more preferably below 4 hours and most preferably below 2 hours. The solids retention time is significantly below 3 days, preferably below 2 days and more preferably below 1 day. The reactor vessel involves at least one fluid inlet including a pipe, a tube, a valve, for example. The reactor vessel also involves a fluid outlet and/or flocculant outlet. These outlets may involve a pipe, a tube, an overspill, a container, a valve, for example.

According to the method of the invention the reactor vessel is inoculated. Preferably, inoculation involves micro-organisms that preferably originate from a biological waste water treatment plant. This enables to recover valuable resources, for example poly electrolytes. These micro-organisms are readily available and can be used in a non-sterile environment. As compared to conventional sterile pure micro-organism cultures that need to be fed with non-sustainable carbon sources as well as with other valuable nutrients, the present invention enables the use of non-sterile micro-organisms that are less demanding in nutrients source and cheaper as compared to sterile micro-organisms. This renders the manufacturing method of the in vention more cost effective and more sustainable.

After inoculation the flocculants are formed comprising organic microbial EPS. The EPS is separated by a membrane and collected at the flocculant outlet. The flocculants are preferably formed in the reactor vessel volume. It will be understood that according to the invention another separation technique can also be applied in addition to or as an alternative for the membrane separation.

The method of the invention uses waste fluid, such as a waste water, as feedstock. Such feedstock typically involves biodegradable and preferably water soluble organic pollutants. In one of the embodiments of the invention the waste water flows comprises fresh and saline waste water conditions containing ethanol and glycerol, for example. This enables an effective manufacturing process.

As a further effect of forming of the flocculants in accordance with the method of the invention less exploited natural flocculants comprising organic microbial EPS are provided. These flocculants are products of biochemical secretions and/or cell lysis, and can make up as much as 50-90% of the organic matter content of microbial aggregates. These microbial EPS include high molecular weight substances, for example polysaccharides, proteins, lipids, and combinations thereof. Examples of combinations are liposaccharides, glycoproteins and lipoproteins.

Flocculants produced by the method of the invention can show comparable or better flocculation properties as compared to conventional flocculants. For example, the natural flocculants produced according to the method of the invention appear to be less shear sensitive as compared to conventional flocculants from synthetic polymers achieving a larger operation window, specifically a wider range of shear conditions.

In a preferred embodiment of the in vention the feedstock has a chemical oxygen demand to nitrogen ratio above 5, preferably above 8, and most preferably above 10 and/or a chemical oxygen demand to phosphorous ratio above 10, preferably above 15, and most preferably above 20.

Experiments have shown that the method of the invention effectively provides the desired flocculants.

In a presently preferred embodiment the forming and/or separating of the flocculants from the fluid preferably comprises the step of aerating.

Performing an aerating step contributes to the amount of dissol ved oxygen in the reactor vessel. Therefore, aerating improves the activity of the micro-organisms that are present in the reactor. Under these conditions tests show that a mixed-culture of micro-organisms develops and mineralises a small fraction of the organic pollutants to carbon dioxide and water (typically less than 30%) and produces EPS, These may be used for the flocculants.

In a preferred embodiment of the invention a dissolved oxygen level of at least 0.5 mg O₂/L, preferably at least 0,75 mg CE/L, and most preferably at least 1 mg O?/L is maintained to obtain further improvement of the yield of the flocculants formation.

Providing and maintaining the oxygen level in the ranges mentioned has a stimulating effect on the productivity of the micro-organisms, and thus on the manufacturing process of the flocculants.

In a further preferred embodiment of the invention the formation of the flocculants provides extracellular poly meric substances of polymers or proteins or a mixture of polymers and proteins.

Flocculants involving extracellular polymeric substances of polymers or proteins or a mixture of polymers and proteins provide an effective and efficient product. Preferably , the polymer fractions are polysaccharides and the charge density is 0,2 - 7 meq/g, preferably 0.35 - 6 meq/g, and most preferably 0.5 5 meq/g.

In one of the embodiments of the invention the waste fluid comprises one or more of fresh and saline waste waters comprising feedstock for the production of microbial EPS.

In experiments the saline and fresh water originating polymers gave a flocculation activity of 80% or above. This activity could even be improved by the addition free calcium ions in a concentration below 200 mg/L, preferably below 150 mg/L, more preferably below 100 mg/L. and most preferably below 50 mg/L. The addition of calcium results in the increase of the flocculation activity.

In a preferred embodiment of the invention flocculants production is combined with biological waste water treatment, preferably comprising the treatment and production under fresh water and/or saline conditions.

The use of these condition results in an effective combination of purification of waste water and the recovery of valuable recourses. This provides efficient and cost-effective purification and recovery in a single operation.

The invention also relates to a system for the production of environmentally safe, biodegradable, organic microbial extracellular polymeric substances from a waste fluid, the system being capable of performing the method in one or more of the embodiments according the invention, wherein the system comprising:

- at least one reactor vessel;

- at least one fluid inlet;

- at least one fluid outlet;

- at least one flocculants outlet; and

- at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet.

The system provides the same effects and advantages as those described for the method.

More specifically, the system enables an efficient and effective water treatment and flocculants production involving at least one reactor, at least one fluid inlet, at least one fluid outlet, at least one flocculants outlet and at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet.

In further embodiments of the invention the system could be extended with different sensors, for example a pH sensor, a temperature sensor, an oxygen level sensor, and/or a level control sensor. It will be understood that further or alternative sensors may also be applied in accordance with the present invention. Preferably, the sensors are connected to a controller/processor that enables monitoring and/or control of the production process. For example, this may involve maintaining the manufacturing within specific boundaries, such as dissolved oxygen level.

The invention also relates to flocculants that are produced by a method according to one ofthe embodiments ofthe invention.

The flocculants provide the same effects and advantages as those described for the method and/or system.

In a presently preferred embodiment the flocculants produced by the method in the disclosed system, wherein the EPS comprising a molecular weight, ranging between 2 kDa and 10000 kDa, preferably ranging between 3 kDa and 8000 kDa, more preferably ranging between 5 kDa and 6000 kDa, and most preferably ranging between 10 kDa and 2000 kDa,

An effect of (maintaining) the EPS in these range(s) is the effective recovery and regaining of valuable recourses, preferably in combination with the cost effective treatment of waste fluid.

The invention further also relates to a use ofthe environmentally safe, biodegradable, organic microbial extracellular polymeric substances from a waste fluid for the production of flocculants.

The use provides the same effects and advantages as those described lor the method, the system and/or the flocculants.

In a presently preferred embodiment the use of the flocculants is cheap and cost effective.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

Figure 1 show's a schematic overview of the method according to the present invention: and

- Figure 2 shows an embodiment of the system capable of performing the method described in the description.

Method 2 (Figure 1) for the production of environmentally safe, biodegradable, organic microbial extracellular polymeric substances, preferably from a waste fluid, follow's a sequence of different steps.

In the illustrated embodiment this starts with providing 4 a reactor and a feedstock. The reactor is inoculated in inoculation step 6 and supplied 8 with microorganisms if these are not already present in the feedstock. As a next step, after inoculation 6, forming 12 of flocculants occurs from the waste fluid. The flocculants are separated from the remaining fluid in separation step 14, preferably using a membrane such as an ultrafiltration membrane. Flocculants are collected in collecting slept8 resulting in a valuable product and treated waste water. The left over fluid could be recycled in recycling step 16 and returned to the reactor and mixed w'ith the waste and/or recycle fluid.

In an illustrated embodiment of the invention, system 102 (Figure 2) produces environmentally safe, biodegradable, organic microbial extracellular polymeric substances from a waste fluid involving method steps of method 2.

System 102 comprises a feed tank 104 that can be filled with waste fluid 106. System 102 has outlet 108 connecting tank 104 to inlet pump 110. Pump 110 provides feedstock to inlet 112, In the illustrated embodiment inlet 112 is part of a so-called submerged membrane bioreactor 114, It will be understood that other reactor types and/or parts could also be appl ied in accordance with the invention.

In the illustrated system, in use, fluid 116 is present in reactor 114. In fluid 116 flocculants 118 are formed, specifically in compartment/reactor part 120. In compartment/reactor part 122 comprising (ultrafiltration) membrane 124 flocculants 118 are separated from fluid 116. Alternatively, a separation is achieved by centrifugation or by a sodium based cation-exchange resin, all followed by dialysis to remove low' molecular weight compounds (<3 kDa).

Reactor 114 is provided with permeate outlet 126 that is connected to permeate pump 128 for further transport of permeate 130. Aeration base 132 enables aerating fluid 116. Waste outlet 134 is connected to waste pump 13 for further transport of waste 138. Sensors 140 enable monitoring and/or control of the production process.

Experiments have been performed wdth system 102. In the experiments parameters as mentioned in tables 1 and 2 are applied.

In the experiments, in the fresh water application the reactor was inoculated with aerobic sludge from a municipal waste water treatment plant and in the saline application the reactor was inoculated with aerobic sludge from a saline w'aste water treatment plant for chemical industries. The polymers were produced from a mimicked industrial waste water, mainly containing ethanol and glycerol, both under fresh and saline waste water conditions. The sheet membrane in the experiments had a nominal pore size of 0.2 pm. After extraction using a ultrafiltration membrane, followed by dialysis to remove low' molecular weight compounds (<3 kDa) and freeze-drying, solutions of these polymers were prepared and used to flocculate kaolin clay suspensions under fresh and saline water conditions and in the absence and presence of calcium ions. Kaolin clay was used to mimic usually negatively charged surface water and waste water particles.

Table 1 MBRs set-up and operation parameters

Parameter	Saline and freshwater MBRs
Reactor type	Submerged membrane bioreactor
Effective volume (L)	3.3
Temperature (°C)	20 + 1
pH	7.5 ± 0.1
Solids retention time, SRT (d)	15
Hydraulic retention lime, HRT (h)	2
Dissolved oxygen concentration (mg/L)	4.0 ± 1.0
Operation time (d )	50
Inlet CODa (mg 1..0	500 ± 40 mg/L
Inlet TNb (mg/L)	32 + 2 mg/L
Carbon/nitrogen ratio (g COD/g TN)	16 ± 1

¹¹ COD: Chemical oxygen demand. ’TN: Total nitrogen - sum of all NH_rN, NOa-N, NO₂-N, organic N

Table 2 Composition of synthetic waste water in both reactors

Compound	Concentration (mg/L)	Nutrient solution	Concentration (mg/L)
Glycerol	205	FeCl3.6H2O	1500
Ethanol	120	ilbo.	150
Ml,·,Cl	100	CoC12.6H2O	150
Yeast extract	60	ZnSo..;.7H3O	120
K2HPO4	7,5	MnCk2H2O	120
ΚΗ ΡΟ;	12.5	Na2MoO4.2H2O	60
MgCl2.6H2O	100	CuSO4.5H2O	60
CaCl.-2H.-O	150	KI	30
NaCT'	30000
Nutrient solution	2mL/L

* NaCl was fed only to the saline MBR

Flocculation tests show the applicability of the method according to the invention to produce flocculants, Furthermore, the results show an EPS yield after extraction, purification and lyophilisation as given in table 3.

Table 3 EPS yield after extraction, purification and lyophilisation.

EPS fraction	Mg EPS/g VSS	Mg EPS/g C0D.ertlinv(J	Mg EPS/g CODi>llet	%(gEPS/g C0DrenwYt.d)
FW SEES	123.5+1.7	83.7 + 1.1	79.3 ±1.1	2.9 + 0.1
FW B-EPS	173,5 + 3.1	117.6 + 2.1	111.4 + 2,0	7.1+0.2
Sal S-EPS	142.5 + 3.3	66,2+1,5	61.7 + 1.5	4.4 + 0.1
Sal B-EPS	250.7 + 3.0	116,5 + 1.4	108.5+1.3	6,7 + 0.1

Data is expressed as mean ± standard deviation of duplicate extraction (VSS: volatile suspended solids; COD_inler: Chemical Oxygen Demand of inlet waste water; COD_remov_e,i‘ Chemical Oxygen Demand removed during waste water treatment).

Tests and experiments performed with system 102 and parameters as mentioned in table and 2 resulted in a mixture of polymers of variable molecular weight ranging between 10 kDa and 2000 kDa.

The present invention is by no means limited to the above described and preferred embodiments thereof. The rights sought are defined by the following claims within the scope of 15 which many modifications can be envisaged.

Claims (15)

1. CLAUSES

   1. Method for production of natural, biodegradable polymeric flocculants from a fluid, such as a waste fluid, the method comprising the steps of:

   - providing a reactor comprising:

   - at least one reactor vessel;

   - at least one fluid inlet:

   - at least one fluid outlet;

   - at least one flocculant outlet: and

   - at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet;

   - inoculation of the reactor;

   - providing feed to the at least one fluid inlet:

   - forming the flocculants;

   - separating the flocculants using the membrane; and

   - providing the flocculants at the flocculant outlet.
2. 2. Method according to clause 1, wherein the fluid comprises biodegradable and soluble organic pollutants.
3. 3. Method according to clause 2, wherein the pollutants comprises a chemical oxygen demand to nitrogen ratio above 5, preferably above 8, and most preferably above 10 and/or a chemical oxygen demand to phosphorous ratio above 10, preferably above 15, and most preferably above 20.
4. 4. Method according to one or more of the foregoing clauses, wherein inoculation of the reactor comprises inoculation with micro-organisms from a biological waste water treatment plant.
5. 5. Method according to one or more of the foregoing clauses, separating and/or wherein forming the flocculants comprises the step of aerating.
6. 6. Method according to clause 5, wherein forming and/or separating a dissolved oxygen level of at least 0.5 mg O?/L, preferably at least 0.75 mg O2ZL, and most preferably at least 1 mg O2/L is maintained.
7. 7. Method by process according to one of the foregoing clauses, wherein the formation of the flocculants provides extracellular poly meric substances of polymers or proteins or a mixture of polymers and proteins,
8. 8. Method according to clause 7, wherein the polymer fractions are preferably polysaccharides, and the charge density is 0,2 - 7 meq/g, preferably 0,35 - 6 meq/g, and most preferably 0,5 5 meq/g.
9. 9. Method by process according to one or more of the foregoing clauses, wherein the waste fluid comprises one or more of fresh and/or saline waste waters comprising microbial extracellular polymeric substances.
10. 10. Method according to one or more of the foregoing clauses, further comprising the combined biological waste water treatment and flocculants production, comprising the treatment and production under fresh water and/or saline conditions.
11. 11. System for the production of biodegradable, organic microbial extracellular polymeric substances, the system comprising:

    - at least one reactor vessel;

    - at least one fluid inlet;

    - at least one fluid outlet;

    - at least one flocculants outlet; and

    - at least one membrane provided in the reactor vessel between the fluid inlet and the fluid outlet.
12. 12. System according to clause 11, further comprising two independent chambers.
13. 13. Flocculants produced by the method and/or in the system of one or more of the foregoing clauses, wherein the flocculants comprising a flocculation activity of 80% or above,
14. 14. Flocculants of clause 13, wherein the extracellular polymeric substances comprising a molecular weight, ranging between 2 kDa and 10000 kDa, preferably ranging between 3 kDa and 8000 kDa, more preferably ranging between 5 kDa and 6000 kDa, and most preferably ranging between 10 kDa and 2000 kDa.
15. 15. Use of microbial extracellular polymeric substances for the production of flocculants from a waste fluid.

    CONCLUSIES

    1. Werkwijze voor productie van natuurlijk, biologische afbreekbare polymerische flocculanten uit een vloeistof, zoals een afvalvloeistof, omvattende de stappen van:

    het voorzien van een reactor omvattende:

    ten minste één reactorvat;

    ten minste één vloeistof inlaat:

    ten minste één vloeistof uitlaat;

    ten minste één flocculant uitlaat: en ten minste één membraan voorzien in het reactievat tussen de vloeistof inlaat en de vloeistof uitlaat;

    het enten van de reactor;

    het voorzien van een toevoer aan de ten minste ene vloeistofïnlaat;

    het vormen van de flocculanten;

    het scheiden van de flocculanten gebruik makend van het membraan; en het voorzien van de flocculanten bij de flocculant uitlaat.

    2. Werkwijze volgens conclusie 1, waarbij de vloeistof omvattende biologisch en oplosbare organische verontreinigingsstoffen.

    3. Werkwijze volgens conclusie 2, waarbij de verontreinigingsstoffen omvattende een chemisch zuurstof vraag tot stikstof ratio van boven 5, bij voorkeur boven 8, en met meeste voorkeur boven 10 en/of een chemisch zuurstof vraag tot fosfor ratio van boven 10, bij voorkeur boven 15, en met meeste voorkeur boven 20.

    4. Werkwijze volgens één of meer van de voorgaande conclusies, waarbij enting van de reactor omvat enting met een micro-organisme van een biologische afvalwaterbehandelmgsinstallatie.

    5. Werkwijze volgens één of meer van de voorgaande conclusies, scheiding en/of waarbij vorming van de flocculanten omvat de stap beluchten.

    6. Werkwijze volgens conclusie 5, waarbij tijdens vorming en/of scheiding een opgelost zuurstof niveau is gehandhaafd van ten minste 0.5 mg O₂/L, bij voorkeur ten minste 0.75 mg O₂/L, en bij meeste voorkeur ten minste 1 mg O₂/U.

    7. Werkwijze volgens één of meer van de voorgaande conclusies, waarbij de vorming van flocculanten extracellulaire polymerische substanties voorzien van polymeer of eiwitten of een mengsel van polymeren en eiwitten.

    8. Werkwijze volgens conclusie 7, waarbij de polymeer fracties bij voorkeur polysachariden zijn en de ladingsdichtheid is 0.2 - 7 meq/g, bij voorkeur 0.35 - 6 meq/g, en bij meeste voorkeur 0.5 5 meq/g.

    9. Werkwijze volgens één of meer van de voorgaande conclusies, waarbij het afvalvloeistof omvat één of meer van zoet en/of zout af valwater om vattende microbiële extracellulaire polymerische substanties.

    10. Werkwijze volgens één of meer van de voorgaande conclusies, verder omvattende een gecombineerde biologische afvalwaterbehandeling en flocculanten productie, omvattende de behandeling en productie bij zout water en/of zout water condities.

    11. Systeem voor de productie van biologisch afbreekbare, organische microbiële extracellulaire polymerische substanties, het systeem omvattende:

    ten minste één reactorvat:

    ten minste één vloeistof inlaat;

    ten minste één vloeistof uitlaat;

    ten minste één flocculanten uitlaat; en ten minste één membraan voorzien in het. reactievat tussen de vloeistof inlaat en de vloeistof uitlaat.

    12. Systeem volgens conclusie 11, verder omvattende twee onafhankelijk kamers.

    13. Flocculanten geproduceerd volgens de werkwijze en/of in het systeem volgens één of meer van de voorgaande conclusies, waarbij de flocculanten omvattende een flocculatie activiteit van 80% of hoger.

    14. Flocculanten van conclusie 13, waarbij de extracellulaire polymerische substanties omvattende een moleculair gewicht, in een bereik tussen 2 kDa en 10000 kDa, bij voorkeur in een bereik tussen 3 kDa en 8000 kDa, bij meer voorkeur in een bereik tussen 5 kDa en 6000 kDa, en bij meeste voorkeur tussen 10 kDa en 2000 kDa.

    15. Gebruik van microbiële extracellulaire polymerische substanties voor de productie van flocculanten uit een af val vloeistof.

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