METHOD OF CONDITIONING A MIXED LIQUOR CONTAINING NONIONIC
POLYSACCHARIDES AND/OR NONIONIC ORGANIC MOLECULES
FIELD OF THE INVENTION
This invention pertains to a method of conditioning a membrane biological reactor
(MBR) mixed liquor containing one or more nonionic polysaxwhaiides and/or nonionic organic
molecules.
BACKGROUND OF THE INVENTION
Biological treatment of wastewater for removal of dissolved organics is well known and
is widely practiced in both municipal and industrial plants. This aerobic biological process is
generally known as the "activated sludge" process in which microorganisms consume the organic
compounds through their growth. The process necessarily includes sedimentation of the
microorganisms or "biomass" to separate it from the water and thus the final effluent with
reduced Biological Oxygen Demand (BOD) and TSS (Total Suspended Solids) is obtained. The
sedimentation step is typically done in a clarifier unit. Thus, the biological process is constrained
by the need to produce biomass that has good settling properties. These conditions are especially
difficult to maintain during intermittent periods of high organic loading and the appearance of
contaminants that are toxic to the biomass.
Membranes coupled with biological reactors (MBRs) for the treatment of wastewater are
well known, but are not widely practiced yet In these systems, ultrafiltration (UF),
microfiltration (MF) or nanofiltration (NF) membranes replace sedmentation of biomass for
solids-liquid separation. The membrane can be installed in the bioreactor tank or in an adjacent
tank where the mixed liquor is continuously pumped from the bioreactor tank and back
producing effluent with much lower total suspended solids (TSS), typically less than 5 mg/L,
compared to 20 to 50 mg/L from a clarifier. More importantly, these MBRs de-couple the
biological process from the need to settle the biomass, since flie biomass separation from the
water is achieved by membrane. This allows operation of the biological process at conditions
that would be untenable in a conventional system including: I) high MLSS (bacteria loading) of
10-30 g/L, 2) extended sludge retention time, and 3) short hydraulic retention time. In a
conventional system, such conditions could lead to sludge bulking and poor settleability.
The benefits of the MBR operation include low sludge production, almost complete solids
removal fix)m the effluent, effluent disinfection, combined COD, solids and nutrient removal in a
single unit, high loading rate capability, no problems with sludge bulking, and small footprint.
Disadvantages include aeration limitations, membrane fouling, and membrane costs.
1
Membrane costs are directly related to the membrane area needed for a given volumetric
flow through the membrane, or "flux." Flux is expressed as liters/m'^/hour (LMH) or gallons/tf /
day (GFD). Typical flux rates in MBRs vary from approximately 10 LMH to about 20 LMH.
These flux rates are relatively lower compared to those observed in drinking water applications
(>50 LMH) with membranes having similar pore size and chemistries. These lower flux rates are
mainly due to fouling of the membranes, and are the main reason for slower growth of MBR
systems for wastewater treatment
The MBR membrane interfaces with so-called "mixed liquor" which is composed of
water, dissolved solids such as proteins, polysaccharides, suspended solids such as colloidal and
particulate material, aggregates of bacteria or "floes", firee bacteria, protozoa, and various
dissolved metabolites and cell components. In operation, the colloidal and particulate solids and
dissolved organics deposit on the surface of the membrane. Colloidal particles form a layer on
the surfece of the membrane called a "cake layer." Cake layer formation is especially
problematic in MBRs operated in the "dead end" mode where there is no cross flow; i.e., flow
tangential to the membrane. Depending on the porosity of the cake layer, hydraulic resistance
increases and flux declines.
In addition to the cake formation on the membrane, small particles can plug the
membrane pores, a fouling condition that may not be reversible. Compared to a conventional
activated sludge process, floe (particle) size is reportedly much smaller in typical MBR units.
Since MBR membrane pore size varies fix>m about 0.04 to about 0.4 yaa, particles smaller than
this can cause pore plugging. Pore plugging increases resistance for permeation through
membrane and decreases flux.
In addition to these physical fouling mechanisms, the soluble polysaccharides (firom
"Biopolymer") adsorb on the membrane surface as well as on the pore walls and form a slimy
layer, thus contributing significantly to the total resistance for water permeation. It is known in
the literature that extra-cellular polysaccharides secreted by bacteria include both anionic (e.g.
uronic acids) as well as nonionic oligo and polysaccharides (e.g. hexoses and pentoses).
Conditioning the mixed liquor with cationic, amphoteric or zwitterionic polymers results in
complexation of only charged polysaccharides. The nonionic oligo/polysaccharides still form a
slimy layer on the membrane surface, resulting in increased resistance for permeation.
Therefore, there is a need to develop improved methods of conditioning the mixed liquor
in MBR systems to also address tiie fouling caused by nonionic oligo/polysaccharides and/or
nonionic organic molecules, and increase the flux of the membranes.
2
FIGURES/DRAWINGS
Figure 1 shows the effect of sequential addition of PGA (polygalacturanic acid) and
Product A in Pilot MBR mixed liquor on suction pressure increase for a 24 hr period.
Figure 2 shows the effect of sequential addition of PGA and I^oduct A in Pilot MBR
mixed liquor on suction pressure increase for a period of S days.
Figure 3 shows the effect of sequential addition of PGA and Product A in Western US
MBR plant mixed liquor on suction pressure increase for a 24 hr period.
SUMMARY OF THE INVENTION
This invention pertains to a method of conditioning a membrane biological reactor mixed
liquor containing one or more nonionic polysaccharides and/or one or more organic molecules
that are nonionic comprising: (a) selecting one or more anionic polymers fhat have the ability to
complex or associate with one or more nonionic polysaccharides and/or one or more organic
molecules that are nonionic; (b) adding a composition containing one or more water soluble
anionic polymers selected from step (a) to the mixed liquor; and (c) adding one or more water
soluble amphoteric, carionic or zwitterionic polymers, or combination thereof to the mixed liquor
after performing step b.
This invention also pertains to a method of conditioning a membrane biological reactor
mixed liquor containing one or more nomonic polysaccharides and/or one or more organic
molecules that are nonionic comprising: (a) selecting one or more anionic polymers that have the
ability to complex or associate with one or more nomonic polysaccharides and/or one or more
organic molecules that are nonionic; (fa) adding one or more water soluble amphoteric, cationic
or zwitterionic polymers, or combination thereof to the mixed liquor; and (c) adding a
composition containing one or more water soluble anionic polymers selected from step (a) to the
mixed liquor;
DETAILED DESCRIPTION OF THE INVENTION
Throughout this patent application the following terms have the indicated meanings.
"MBR" means membrane biological reactor.
"Amphoteric polymer" means a polymer derived from bofli cationic monomers and
anionic monomers, and, possibly, other non-ionic monomer(s). Amphoteric polymers can have a
net positive or negative charge. The amphoteric polymer may also be derived from zwitterionic
3
monomers and cationic or anionic monomers and possibly nonionic monomers. The amphoteric
polymer is water soluble.
"Cationic polymer" means a polymer having an overall positive charge. The cationic
polymers of this invention may be prepared by polymerizing one or more cationic monomers, by
copolymerizing one or more nonionic monomers and one or more cationic monomers, by
condensing epichlorohydrin and a diamine or polyamine or condensing ethylenedichloride and
ammonia or formaldehyde and an amine salt. The cationic polymer is water soluble.
"Zwitterionic poljntner" means a polymer composed fcom zwitterionic monomers and,
possibly, other non-ionic monomer(s). In zwitterionic polymers, all the polymer chains and
segments within those chains are rigorously electrically neutral. Therefore, zwitterionic
polymers represent a subset of amphoteric polymers, necessarily maintaining charge neutrality
across all polymer chains and segments because both anionic charge and cationic charge are
introduced within the same zwitterionic monomer. The zwitterionic polymer is water-soluble.
"Anionic polymer" means a polymer having an overall negative charge. It also means, in
addition to the negative charge, the anionic polymer has functionalities and ability for association
with neutral/non-ionic oligo/polysaccharide and/or other non-ionic organics present in the mixed
liquor of MBR. It may be natural or synthetic. The anionic poljmier is water-soluble.
"Mixed Liquor" or "sludge" means a mixture of wastewater, microorganisms used to
degrade organic materials in the wastewater, organic-containing material derived from cellular
species, cellular by-products and/or waste products, or cellular debris. Mixed liquor can also
contain colloidal and particulate material (i.e. biomass / biosolids) and/ or soluble molecules or
biopolymers (i.e. neutral and charged oligo/polysaccharides, proteins, etc.);
MLSS: Mixed Liquor Suspended Solid (mg L'' or ppm) means the concentration of
biomass which is treating organic material, in the mixed liquor.
DMAE.MCQ means dimethylaminoethylacrylatcmethylchloride quatemaiy salt
"Nonionic" means having a net neutral charge. For example, a polysaccharide that is a
non-ionic polysaccharide has a net neutral charge.
"Polysaccharide/polysaccharides" include polysaccharide(s) and/or oligosaccharide(s).
PREFERRED EMBODIMENTS
As stated above, the anionic polymers selected must have the abihty to associate with one
or more types of nonionic polymers and/or organic molecules that are nonionic.
One of ordinary skiU in the art would understand what the word associate means. For
example, association of a target molecule(s), e.g. nonionic polysaccharides and/or other nonionic
4
organic molecules with anionic polymer may occur by one or more of the following manners of
association: H-bonding, ionic bonding; covalent bonding; co-ordination bonding, and Van der
Waals' forces.
Factors such as mixed liquor salinity, pH, temperature and presence of H-bond breaking
compounds such as urea may enhance or inhibit association.
In one embodiment, the association between anionic polymers and non-ionic
polysaccharides in the mixed liquor is through H-bonding
The amount of anionic polymer(s) added to the system depends on the type of mixed
liquor.
In one embodiment, flie anionic polymer is a polygalacturonic acid.
In another embodiment, the anionic polymers are selected from the group consisting of:
glucuronic acid; mannixronic acid; pyruvic acid; alginic acid; saUs thereof; and combination
thereof.
In another embodiment, the anionic polymers with no limitation on stereochemistry or
linkage type between the monomers are selected.
In another embodiment, the anionic polymers are homopolysaccharides or
heteropolysaccharides.
In anodier embodiment, the anionic polymers could be branched or linear.
In another embodiment, the anionic polymers may be selected from those containing
carboxylic acid, sulfonic acid or phosphoric acid functionality and H-bonding groups such as -
OH, -NH and/or -SH. Various amounts of anionic polymers may be added to the mixed liquor.
In another embodiment, the amount of anionic polymer added to the mixed liquor is from
about 5 ppm to about 10,000 ppm based upon active solids. In a further embodiment, the amount
of anionic polymer added to the mixed liquor is from about 10 ppm to about 200 ppm based upon
active solids.
The target species for said anionic polymers include neutral/nonionic polysaccharides,
containing e.g. several -OH groups, and/or other nonionic organic molecules.
The nonionic polysaccharides may be of various types. Depending on the mixed liquor
that is being conditioned by the polymers, the types of nonionic polysaccharides may vary from
system to system.
In one embodiment, the non-ionic polysaccharides are selected from the group consisting
of: rhanmose, pyranose, galactose, mannose, dextrans and glucans.
Those skilled in the art would know that the non-ionic polysaccharides could be other
types of hexoses and pentoses, than those mentioned above.
5
In one embodiment, the non-ionic polysaccharides could be homopolysaccharides or
heteropolysaccharides.
In another embodiment, the non-ionic polysaccharides could be branched or linear.
In another embodiment, the non-ionic organic molecules from mixed liquor that are
targeted for association by the anionic polymers are selected from the group consisting of:
amines; alcohols; glycerols; glycols; and a combination thereof
After performing the addition of the step of adding anionic polymers to the mixed liquor,
including, but not necessarily, subsequent to the addition of anionic polymers, one or more water
soluble amphoteric, cationic, or zwitterionic polymers, or a combination thereof are added to the
mixed liquor.
In one embodiment, die amphoteric polymers are selected from the group consisting of:
acrylic acid/DMAEA-MCQ copolymer, DADMAC/acrylic acid copolymer, DADMAC/acrylic
acid/acrylamide terpolymer, and a combination thereof.
In another embodiment, the amphoteric polymers have a molecular weight from about
5,000 daltons to about 2,000,000 daltons.
In another embodiment, the amphoteric polymers have a molecular weight from about
1,000,000 daltons to about 2,000,000 daltons.
In another embodiment, the amphoteric polymers have a cationic charge equivalent to
anionic chai:ge equivalent ratio of about 0.2:9.8 to about 9.8:0.2.
In another embodiment, the amphoteric polymer is a 70 mole %/30 mole % blend of
DMAEA.MCQ and acrylic acid. This is a preferred amphoteric poljoner because it consistently
exhibits good flux enhancement.
In another embodiment, the cationic polymer is a copolymer of acrylamide and one or
more cationic monomers selected from the group consisting of: diallyldimethylammonium
chloride; dimethylaminoethylacrylate methyl chloride quaternary salt;
dimethylarainoethylmethaciylate methyl chloride quaternary salt; and
dimethylaminoethylacrylate benzyl chloride quaternary salt.
In another embodiment, the cationic polymers have a cationic charge of at least about 5
mole percent.
In another embodiment, the cationic polymers have a cationic charge of 100 mole
percent.
In another embodiment, the cationic polymers have a molecular weight of from about
2,000,000 daltons to about 5,000,000 daltons.
6
In another embodiment, the cationic polymer is selected from the group consisting of:
polydiallyldimethylammonium chloride; polyethyleneimine; polyepiamine; polyepiamine
crosslinked with ammonia or ethylenediamine; condensation polymer of ethylenedichloride and
ammonia; condensation polymer of triethanolamine and tall oil fatty acid;
poly(dimethylaminoethylmethacrylate sulfuric acid salt); and poly(dimethylaminoethylacrylate
methyl chloride quaternary salt).
In another embodiment, the amphoteric polymers are selected from the group consisting
of: dimethylaminoethyl acrylate methyl chloride quaternary salt/acrylic acid copolymer;
diallyldimethylammonium chloride/acrylic acid copolymer; dimethylaminoethyl acrylate methyl
chloride salt'N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammoniumbetaine
copolymer, acrylic acid/N J^-dimethyl-N-methacrylamidopropyl-N-(3 -sulfopropyI)-ammonium
betaine copolymer and DMAEA-MCQ/Acrylic acid/N,N-dimethyl-N-methacrylamidopropyl-N-
(3-sulfopropyl)-ammonium betaine teipolymer.
In another embodiment, the zwitterionic polymers are selected fh)m the group consisting
of: N, N-dimethyl-N-(2-acryloyloxye1hyl)-N-(3-sulfopTopyl) ammonium betaine; copolymer of
aciylamide and N, N-dimethyl-N-(2-acryloyloxyethyl)-N-{3-suIfopropyl) anunonium betaine;
and terpolymer of acrylamide, N-vinyl-2-pyTrolidone; and l-(3-suIfopropyl)-2-vinylpyridinium
betaine.
In another embodiment, the water soluble zwitterionic polymer is composed of about 1 to
about 99 mole percent of N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammonium
betaine and about 99 to about 1 mole percent of one or more nonionic monomers.
In another embodiment, the water soluble zwitterionic polymers have a molecular weight
from about 5,000 daltons to about 2,000,000 daltons.
In another embodiment, die anionic polymers have a molecular weight from about 1,000
daltons to about 2,000,000 daltons.
The conditioning method may be a part of broader method of purification.
In one embodiment, the method further comprises: purifying the conditioned mixed liquor
by further processing the mixed liquor through one or more membranes selected from the group
consisting of: ultrafiltration membranes; microfiltration membranes; nanofiltration membranes;
and reverse osmosis membranes.
The conditioning protocol can be applied to various types of treatment facilities.
In one embodiment, the mixed liquor is from a membrane biological reactor for treating
municipal, institutional (e.g. resorts, apartment complexes, hotels, schools), or industrial
wastewater.
7
There may be various amounts of nonionic polysaccharides in the mixed liquor.
In one embodiment, there is at least 10% of nonionic polysaccharides based upon the total
amount of nonionic species in the mixed liquor.
The following examples are not meant to be limiting.
EXAMPLES
A. EXPERIMENTAL PROTOCOL
Since polygalactuionic acid (PGA) is one of the anionic polysaccharides found in extracellular
polysaccharides, it was chosen for testing. Product A (an amphoteric DMAEA.MCQ
(70 mole%)-Acrylic acid (30 mole%) copolymer with net positive charge) was used for second
step after conditioning the mixed liquor with PGA. Currently the MBR plants typically run at
12-25 LMH due to severe fouling at higher fluxes. Therefore, fouling control for longer period at
higjier flux of e.g. 36 LMH would be of great interest to MBR users.
The experimental protocol involved the following sequence:
1) addition of mixed liquor in the flow-through cell tanks containing cleaned
membranes (7.5 L each in control and treatment),
2) addition of Na salt of PGA (referred hereafter as PGA) at various concentrations
in the treatment tank and mixing for 10 minutes under aeration (10 Liter/min),
3) addition of 250 ppm-active product A and mixing for 10 minutes under aeration,
and
4) permeate suction at 36 LMH and 10 lit/min membrane aeration (flat plate
membrane with active area of 0.1 m^), while monitoring the suction pressure
B. RESULTS
Figure 1 shows the effect of addition of PGA at various concentrations, followed by
product-A for mixed liquor conditioning on the suction pressure of membrane at 36 LMH flux
with a mixed liquor obtained from a pilot MBR that was operated using a synthetic wastewater.
Higher the suction pressure, higher the membrane fouling. MBR plants typically clean the
membranes after the suction pressure reaches 7-8 psi. It is apparent from Figure 1 that the
suction pressure for control reached 12 psi within 30 minutes, whereas at (he end of the 24 hours,
the suction pressures decreased from 10 psi with Product -A alone, to 8 psi with 50 ppm PGA+
8
250ppra-activeProduct-A and to about 3 psi with 100 or 200 ppm PGA+ 250 ppm-active
Product-A. The next experiment was conducted to evaluate the sustainability of above results for
longer period with 200ppra PGA+250 ppm-active Product-A, with sludge replacement and
treatment every 24 hours. As shown in Figure 2, the sequential addition resulted in suction
pressure increase up to only 3 psi after 5 days of continuous operation.
The method of this invention was also tested with mixed liquor obtained fitom Western
US full-scale municipal MBR plant. This mixed liquor had lower MLSS (0.97%) and
polysaccharide level (7 ppm) compared to pilot MBR mentioned above (1.25-1.5% and 50-70
ppm, respectively). Therefore PGA and Product-A concentrations were chosen to be 20 ppm and
25 ppm, both as active solids, respectively. The results for a 24 hours experiment are shown in
Figure 3. The beneficial efifect of sequential addition is apparent with this low fouling mixed
liquor as well.
Thus, the sequential chemical addition method resulted in fouling reduction at high flux
of 36 LMH, with both high fouling and low fouling mixed liquors. Also, the COD removal was
about 90% and thus not affected by the method of this invention.
9

CLAIMS
We claim:
1. A method of conditioning a membrane biological reactor mixed liquor containing one or
more nonionic polysaccharides and/or one or more organic molecules that are nonionic
comprising:
a. selecting one or more anionic polymers that have the ability to complex or
associate with one or more nonionic polysaccharides and/or one or more organic
molecules that are nonionic;
b. adding a composition containing one or more water soluble anionic polymers
selected from step (a) to the mixed liquor, and
c. adding one or more water soluble amphoteric, cationic or zwitterionic polymers,
or combination thereof to the mixed liquor after performing step b.
2. The method of claim 1 wherein said anionic polymer is polygalacturonic acid
3. The method of claim 1 wherein said amphoteric polymer is a DMAEA.MCQ-Acrylic acid
copolymer with net positive charge.
4. The mefliod of claim 1 wherein the amount of anionic polymers added to the mixed liquor
is from about 10 ppm to about 200 ppm based upon active solids.
5. The method of claim 1 wherein 1000 ppm as active solids of amphoteric polymer is
added to the mixed liquor, wherein said amphoteric polymer is DMAEA.MCQ (70
mole%)-Acrylic acid (30 mole%) copolymer with net positive charge
6. The method of claim 1 further comprising purifying the conditioned mixed liquor by
further processing the mixed liquor through one or more membranes selected from the
group consisting of: ultrafiltration membranes; microfiltration membranes; nanofiltration
membranes; reverse osmosis membranes; and a combination thereof.
7. The method of claim 1, wherein the amphoteric polymers are selected from the group
consisting of: acrylic acid/DMAEA-MCQ copolymer; DADMAC/acrylic acid copolymer;
DADMAC/acrylic acid/acrylamide terpolymer; and a combination thereof
8. The method of claim 1, wherein the amphoteric polymers have a molecular weight from
about 5,000 daltons to about 2,000,000 daltons.
9. The method of claim 1, wherein the amphoteric pol5Tners have a molecular weight from
about 1,000,000 daltons to about 2,000,000 daltons.
10
10. The method of claim 1, wherein the amphoteric polymers have a cationic charge
equivalent to anionic charge equivalent ratio of about 0.2:9.8 to about 9.8:0.2.
11. The method of claim 1, wherein the amphoteric polymers are a 70%/30% blend of
DMAEA.MCQ and acrylic acid.
12. The method of claim 1, wherein the cationic polymers are copolymers of aciylamide and
one or more cationic monomers selected from the group consisting of:
diallyldimethylammonium chloride; dimethylaminoethylacrylate methyl chloride
quaternary salt; dimethylaminoethylmethacrylate methyl chloride quaternary sah; and
dimethylaminoethylacrylate benzyl chloride quaternary salt
13. The method of claim 1, wherein the cationic polymer has a cationic charge of at least
about 5 mole percent.
14. The method of claim 1, wherein the cationic polymer has a cationic charge of 100 mole
percent.
15. The method of claim 1, wherein the cationic polymer has a molecular weight from about
2,000,000 daltons to about 5,000,000 daltons.
16. The method of claim 1, wherein the cationic polymer is selected from the group
consisting of: polydiallyldimethylammonium chloride; polyethyleneimine; polyepiamine;
polyepiamine crosslinked with ammonia or ethylenediamine; condensation polymer of
ethylenedichloride and ammonia; condensation polymer of triethanolamine and tall oil
fatty acid; poly(dimethylaminoethylmethacrylate sulfuric acid salt); and
poIy(dimethylaminoethylacTylate methyl chloride quaternary salt).
17. The method of claim 1, wherein the amphoteric polymer is selected from
dimethylaminoethyl acrylate methyl chloride quaternary salt''acrylic acid copolymer;
diallyldimethylammonium chloride/acrylic acid copolymer; dimethylaminoethyl acrylate
methyl chloride salt/N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-
ammonium betaine copolymer, acrylic acid/N,N-dimethyl-N-methacrylamidopropyl-N-
(3-sulfopropyl)-amraonium betaine copolymer; and DMAEAMCQ/Acrylic acid/N,Ndimethyl-
N-methacrylamidopropyl-N-(3-sulfopropyl)-ammonium betaine terpolymer.
18. The method of claim 1, wherein the zwitterionic polymers are selected from the group
consisting of: N, N-dimethyl-N-(2-aciyloyloxyeihyl)-N-(3-sulfopropyl) ammonium
betaine; copolymer of aciylamide and N, N-dimethyl-N-{2-acryloyloxyethyl)-N-(3-
sulfopropyl) ammonium betaine; and terpolymer of aciylamide, N-vinyl-2-pjTTolidone,
and l-(3-sulfopropyl)-2-vinylpyridimum betaine.
11
19. The method of claim 1, wherein the zwitterionic polymer is composed of about 1 to about
99 mole percent of N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-
ammonium betaine and about 99 to about I mole percent of one or more nonionic
monomers.
20. The method of claim 1, wherein the zwitterionic polymer has a molecular weight from
about 5,000 daltons to about 2,000,000 daltons.
21. The method of claim 1 wherein the anionic polymer has a molecular weight from about
1,000, daltons to about 2.000,000 daltons.
22. The method of claim 1, wherein the association between anionic polymers and a nonionic
polysaccharides in the mixed liquor is through H-bonding.
23. The method of claim 1, wherein the anionic polymers are selected from the group
consisting of: glucuronic acid, maimuronic acid, pyruvic acid, alginic acid, salts thereof,
and combination thereof.
24. The method of claim 1, wherein the non-ionic polysaccharides are selected from the
group consisting of: rhamnose, pyranose, galactose, mannose, dextrans, glucans, and a
combination thereof.
25. The method of claim 1, wherein die non-ionic organic molecules from mixed liquor that
are targeted for association by the anionic polymers are selected from the group
consisting of: amines, alcohols, glycerols, glycols, and a combination thereof
26. The method of claim 1 wherein the mixed liquor is from a membrane biological reactor
for treating municipal, institutional, or industrial wastewater.
27. A method of conditioning a membrane biological reactor mixed liquor containing one or
more nonionic polysaccharides and/or one or more organic molecules that are nonionic
comprising:
a. selecting one or more anionic polymers that have the ability to complex or
associate with one or more nonionic polysaccharides and/or one or more organic
molecules that are nonionic;
b. adding one or more water soluble amphoteric, cationic or zwitterionic polymers,
or combination thereof to the mixed liquor, and
c. adding a composition containing one or more water soluble anionic polymers
selected from step (a) to the mixed liquor.
12
28. A method of conditioning a membrane biological reactor mixed liquor containing one or more
nonionic polysaccharides and/or one or more organic molecules that are nonionic substantially as herein
described with reference to the foregoing description and the accompanying drawings.
Dated this 1*' day of December 2010. / ^/^^ /
V. SJ^radVadehra
V QW