Chair of Food- and Bioprocess Engineering TUM School of Life Sciences Weihenstephan Technische Universität München Towards ‘Zero liquid discharge’: Utilization of processing side streams as diafiltration media in microfiltration Dipl.-Ing. (FH) Michael Reitmaier, Dipl.-Ing. Hans-Jürgen Heidebrecht Univ.-Prof. Dr.-Ing. Ulrich Kulozik Technical University of Munich London, 19th April 2017 Dipl.-Ing. (FH) Michael Reitmaier | Chair of Food and Bioprocess Engineering 1
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Chair of Food- and Bioprocess Engineering TUM School of Life Sciences Weihenstephan Technische Universität München
Towards ‘Zero liquid discharge’: Utilization of processing side
streams as diafiltration media in microfiltration
Dipl.-Ing. (FH) Michael Reitmaier,
Dipl.-Ing. Hans-Jürgen Heidebrecht
Univ.-Prof. Dr.-Ing. Ulrich Kulozik
Technical University of Munich
London, 19th April 2017
Dipl.-Ing. (FH) Michael Reitmaier | Chair of Food and Bioprocess Engineering 1
Food- and Bioprocess Engineering
Motivation
2
• Dairy processing characteristically requires very large quantities of fresh water
• Discharge of wastewater is a dominant environmental problem
• Fractionation of milk proteins by microfiltration in diafiltration mode:
Water and time consuming
Variability in characteristics of products on market
Project aims:
• Improvement of process sustainability by
Reduction of fresh water consumption and generation of wastewater
Valorization of processing side streams
• Optimization of filtration performance and reduction of product variability
Food- and Bioprocess Engineering
Separation challenge of skim milk
3
Whey proteins (WP)
α-Lactalbumin, β-Lactoglobulin
(mean diameter 2-4 nm)
should permeate a membrane with a
pore size of 0.1 µm
Casein micelles
(mean diameter 180-200 nm)
No permeation at a pore size
of 0.1 µm expected
Milk proteins
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10
Durchmesser (nm)
Hä
ufi
gk
eit
(%
)
Whey proteins
0
2
4
6
8
10
12
14
16
0 100 200 300 400 500
Durchmesser (nm)
Häu
fig
keit
(%
)
Whey
protein
s
Diameter [nm]
Hä
ufi
gk
eit
[%
]
Fre
quency [
%]
Diameter [nm]
Casein
Fre
quency [
%]
Food- and Bioprocess Engineering
Fractionation of milk proteins by microfiltration
4
UF-Permeate –Lactose/Salt
(further processing)
MF-Retentate – micellar casein UF-Retentate – native whey protein
CaseinCPC
Molke
MF-Permeate – ideal whey
SWM modul(10 kDa)
DF-Medium: Water, UF-, NF-, RO-Permeate
Whey proteinWPC/WPI
Skim milk
Pore size(0,1 µm)
Investigations on the applicability of different protein free washing media
for the milk protein fractionation by microfiltration (MF) / ultrafiltration (UF)
Food- and Bioprocess Engineering
pH [-]
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0
Co
nd
uctivi
ty [µ
S/c
m]
0
2000
4000
6000
8000
10000
UF per. (skim milk, sweet whey)
UF per. (sour whey, TCW)
NF per.
RO per.
Vapor condensates
Tap water
Characterization of industrial samples: Conductivity and pH range
5
• Conductivity ranges from ~0 to 9000 μS/cm
• pH ranges from 4.3 to 7.8
Increased and decreased levels of ionic strength and pH compared to milk milieu in DF
Skim milk
Food- and Bioprocess Engineering
Changes of milk milieu during DF with different media
6
[adapted from Gaucheron 2011]
Distribution of minerals in bovine milk in physiological conditions (pH 6.7)
Calcium,
Natrium,
Phophate,
Citrate
pH cCasein
(Lactose )
Carbonate,
Lactate
Food- and Bioprocess Engineering
Changes of filtration characteristics
7
[adapted from Altmann 2000]
Colloidal interactions • Hydrophilic/hydrophobic
• Electrostatic
• Van-der-Waals
• Steric effects
Filtrate
Hydrodynamic
lift force FL
Friction force Ff Drag force FCF
Colloidal interactions
and drag force FJ
Diffusion
Crossflow velocity
Hypotheses: The structure of the deposit layer (mainly casein micelles) will change
depending on the DF media and therefore affect the filtration performance
Food- and Bioprocess Engineering
Whey protein decrease during application of constant volume DF in MF
8
DSpV
Vp
C
C DSDS
expexp
00
CDS [g.l-1] Conc. in MF retentate after diafiltration
C0 [g.l-1] Conc. in product before DF
DS [-] Diafiltration step
p [-] Permeation
VDS [L] Volume of added DF-medium
V0 [L] Hold-up volume
t
Per
C
Cp
Re
The higher the permeation the less
diafiltration steps are needed to
obtain a certain level of purity
DF-Medium MF-Retentate – micellar casein
Micellar casein
MF-Permeat – whey proteins
Skim milk
Pore size(0,1 µm)
Flu
x (
J )Membran
A
VJ
per
The higher the flux the less time is
required for one DF step
Food- and Bioprocess Engineering
c [
mg/L
]
0
50
100
150
200
Sodium
Magnesium
Calcium
DF trials at pilot scale with different types of media
9
Filtration setup:
TAMI Isoflux® gradient membrane,
23 channel, 0.14 µm
DpTM = 1.1 bar, tw = 150 Pa,
ϑ = 50 °C
Liquids used:
Pasteurized skim milk (cold stored)
DF media:
• UF permeate, obtained from skim
milk at 50 °C
• Deionised water
• Hard tap water 18 dGH
• Tap water mixed with deionised
water => 9 dGH
• Softened water
Samples
of tap
waters
Tap
water
used
Softened
water
Food- and Bioprocess Engineering
DF step [-]
0 1 2 3 4 5
Flu
x [L
/m²h
]
0
100
150
200
250
Influence of diafiltration media on the flux at 50 °C
10
TAMI Isoflux 0,14 µm, = 50 °C, TMP = 1.1 bar, t= 150 Pa
Deionised water
Tap water 9 dGh
UF permeate
• Flux for UF permeate decrease due to initial formation of deposit layer
• Different water types lead to differently pronounced increase of flux
Tap water 18 dGh
Softened water
Food- and Bioprocess Engineering
Filtration time [min]
0 30 60 90 120 150 180 210
c r
el
-Lg [
%]
0
10
20
30
40
50
60
70
80
90
100
Deionised water
UF permeate
Tap water 18 dGh
Tap water 9 dGh
Softened water
Whey Protein decrease over DF time
11
TAMI Isoflux 0,14 µm, = 50 °C, TMP = 1.1 bar, t= 150 Pa
Application of ion-free processing side streams like vapor condensates / RO-
permeates can enhance filtration performance
Food- and Bioprocess Engineering
Summary: Improvement of process sustainability
12
DF-Medium: UF-Permeate –Lactose/Salt
MF-Retentate – micellar casein UF-Retentate – native whey protein
CaseinCPC
Molke
MF-Permeate – ideal whey
SWM modul(10 kDa)
DF-Medium: Water, RO-Permeate, NF-Permeate
Whey proteinWPC/WPI
Skim milk
Pore size(0,1 µm)
Spray drying
WPC/WPI and CPC powder
2. Investigation of functionality1. Investigation of process efficiency as function of the DF-medium
• Reduction of fresh water and wastewater by replacing fresh water as diafiltration media
• Valorization of processing side streams
• Faster process with decreased energy demand due to optimized filtration efficiency
• Reduction of product variability of spray dried casein and whey protein concentrates
• Selective change of functional properties of the protein fractions by using certain
diafiltration media for a specific purpose => definition of optimum medium composition
Food- and Bioprocess Engineering
This research project is financially supported by the
German Ministry of Economics and Technology (via AiF)
and the FEI (Forschungskreis der Ernährungsindustrie