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

e.V., Bonn). Project AiF 18818 N.

www.technologieseminar-lmvt.de