Recent Advances in Membrane Technology

Dr Bob Lovitt

Swansea University - Membranology Ltd

Pressure driven Membrane technologies

Current markets • Desalination

– Now the dominant technology

• Food processing – Beverages

• Cider, beer, wine. (clarification, beverage recovery)

– Milk • Massive influence on the industry with many new products

– Vegetable processing • Being considered for natural product recovery

• Waste water treatment – Water reuse – Recovery from wastes streams

Water Treatment Products

Membrane Markets

MF and UF for Water treatment

RO/NF membranes

Desalination costs

Capital expenditure in the power industry

Current Drivers and Limitations • Costs

– Energy – Membrane replacement – Capital costs – Osmotic pressure

• Fouling – Avoiding fouling – Cleaning

New demands • Environmental technology

– More water reuse • Decontamination of water • Metals • Organics ( endocrine conjeners, pesticides, priority pollutants

– Resource recovery • Metals (Rare earth metals) • Nutrients (P, N, K) • Organic acids (fatty acids from AD systems)

• Product recovery from aqueous environments – Natural product recovery

• Pigments • Bioactives (Low molecular weight) peptides, amino sugars) • Flavours (Tea)

– Algal biorefinary • Nutrient formulation • Harvesting • Algal component fractionation

Advances in Membrane technology • Drivers for membrane process development

– New demands • Regulatory push • Resources recovery/circular economy • Waste reduction

– New processes and applications • MBR • Hybrid applications

– New membrane materials – Better understanding of theory

• New separation strategies • Management of fouling

Membrane separations and transport processes

Requires a detailed knowledge of the process environment • Membrane surfaces • Solutions properties • Complex interactions bewteen particles/ surfaces in the liquid environment

Membrane reactors

• MF/UF based membrane systems

• Inside-out MBR.

• Outside-in MBR. – Intensified water recovery and sludge separation

Membrane Bioreactors

• Basic Concept.

Feed

Cell/Enzyme

Separation

Reactor Spent/transformed

Feed

Cell Recycle

Advantages ……….. and disadvantages • Initial filtration step in product recovery

and water recycle

– As cells do not interfered with recovery and vice-versa

• Relatively robust

• Physical separation with no additions

• No phase change in most systems

• Perfusion Reactor

– Reduced inhibition

– High cell concentration

– High volumetric productivity

– Manipulation of the system with product formation and little growth

• Gassing system possible

• Additional costs • Capital cost

• Energy for pumping

• Effective membrane

management: a must • Cleaning and regeneration need

care

• Operational complications • Gas disengagement

• Fouling avoidance

MBR

5

4

2

6

131

P P

17

P

21 20

PP

3 16

11

1514

78

12

P

19

18

PP

9

10

Figure.2 A diagram of membrane cell-recycle bioreactor: (1) Feed tank (100L), (2) Feed membrane (Filtering area: 0.2 m2), (3) Bioreactor (26L) (4) Heat exchanger, (5) Product

membrane (1 m2), (6) the alkali tank (6L, 2 N NaOH), (7) Centrifugal pump, (8) Peristaltic pump,

(9) Nitrogen gas in and out, (10) Inoculums input, (11) Liquid level indicator/transmitter, (12) Cell

bleed, (13) Feed tank heating/cooling, (14) Diaphragm valve, (15) Pressure gauge, (16)

Solenoid/Pinch valve, (17) Pressure indicator/transmitter, (18) Flow meter indicator/transmitter,

(19) Temperature indicator/ transmitter, (20) pH sensor, (21) Weight cell sensor. Total volume of

the fluid to circulate through the system was 36L including the volumes of bioreactor and

connections.

Membrane Bioreactor Design

Sterilisation of feed by membrane filtration

Inoculation from batch

Feeding strategies manual control using alkali consumption as a measure of activity. Feed control by pump on permeate flow and level control

Limits to operation membrane filtration conditions, fouling by medium and cells

Membrane Bioreactor

Membrane bioreactors: Comparative productivity.

Membrane Bioreactors: enhanced product

recovery & water recycle

Concetrated

Feed

MF/UF Cell

Separation

Reactor Concentrated Spent transformed Feed

Cell Recycle

NF/RO product concentration

purification

Water/medium

recycle Cell bleed

Hybrid membrane systems

• Freeze desalination RO/Freezing – Overcoming osmotic pressure limitations for water recovery

• Membrane/ stripping Ammonia stripping

– Concentrates materials to facilitate stripping

• Membrane/ion exchange

– Boron removal

• Combined membrane systems for refineries

Microalgae Biorefinery Options

Regional economics, demands, resources - all play a role in the best strategy and spectrum of products to be produced.

Microalgae Biorefinery Options

Regional economics, demands, resources - all play a role in the best strategy and spectrum of products to be produced.

Membrane

technology

Membrane integration

• Nutrient recovery and fractionation

– e.g. Fractionation of digester fluids

Membrane technology

•Suitable technology for pre-treatment and separation •Technology quite well developed but not widely industrially applied for waste processing Benefits of membrane filtration include: •Physical separation (water does no change phase)

•No additives (chemicals and/or other materials) are added other than when membranes are manufactured •There is a wide range of membrane process based on the membrane pore size

•Filtration allows manipulation of the nutrient content, when combined with leaching and acidification using MF or selective separation and concentration using subsequent NF and RO processes

Benefits of membrane technology

Advantages and commercial benefits of nutrients recovery

•Reduced demand on WWTP as reduced carbon is extracted so reducing costs and energy requirements of oxidation and CO2 release •The extraction of reduced carbon (as VFA) for reuse and substitution of VFA’s derived from petrochemicals reducing reliance on fossil carbon for chemicals of favourable nutrients •Ammonia recovery would save CO2 production and enhance the formation of a potentially valuable product if in a concentrated form •Phosphate is a finite resource is becoming increasingly expensive (800% rise between 2006 to 2008, $50 to $400) with a current value of over $500 per tonne

Although its production is carbon neutral it’s been achieved by mining causing environmental and social issues.

Fig.2. Schematic diagram of advantages of the process

Zacharof &Lovitt, Water Science &Technology, Under review, 2014

Nutrient

recovery

Algae

Export Options

AD

Coarse filtratio

n

MF Nutrient

PBR

Dewatered course solid

MF Algae harvesting

Food Waste etc.

Fine solids Water

CO2, Heat,

Engine Power O2

O2

Protein recovery

Protein Feed

Compost

Cell debris

N and P minerals

Power

Integration of AD with algal production

Nutrient Recovery Methodology: Filtration

E-3

P-4

P-2

E-1

P-8P-7P-10

E-5

E-4

V-2

E-2

V-3

P-5

P-6

V-1

P-3

P-9

Membralox

Ceramic Microfiltration

(MF) membrane

Pore size: 0.2μm

Regenerative

Pump

Kennet K12

Feed Vessel

Pressure valve

Pressure gauge

(0-4 bar)

Pressure gauge

(0-4 bar)

Valve

ValveDrain

Regenerative

Pump

RG550

Heat Exchanger

P-11

P-6

P-12

Picture of the processing system Diagram of the processing system

Permeate composition Table 1: The influence on nutrient composition of a multi-step acidic and non-acidic DF.

Both experiments 1 and 2 started with an initial filtration step (A) and are independent of

each other. Experiment 1 was a two step recovery process with A1 being obtained under

acidic conditions. In experiment 2 was a three step recovery process with B2 obtained

through non-acidic DF and C2 through acidic DF.

Treatmen

t Sample

NH3-N

mM

Std Dev

(%)

PO4-P

mM

Std Dev

(%) N:P

A (initial permeate) 48.99 7.8 1.34 15.3 36.6

1 B1 (acidic DF) 19.36 2.2 2.31 3.5 8.4

2 B2 (non-acidic DF) 26.00 7.0 0.83 5.6 31.5

C2 (acidic DF) 14.45 8.0 1.72 1.6 8.4

Nanofiltration: small molecule recovery

• The most sophisticated and powerful method for small molecule recovery

• Will require combined use of several membranes to make NF work – Tea flavour recovery – Vegetable waste processing – Potato processing – Peptide recovery

AD or Acidogenic

Reactor

Coarse filtration

MF

Freezer Dewatered course solid

Food Waste etc. Fine solids

Heat

Engine Power O2

Fatty acid salts

Compost N and P minerals

NF/RO

Low salt Contaminated

Ice Concentrates, and differential crystallisation

clarified solution

Clean water

Produce recovery using Integrated membrane-freeze-thaw process

clarified solution

H2O

Net energy from CHP = 405 kWh/te, Energy required to freeze 1 te water contain 2 % solids at 25oC = 119 kWh Energy required to freeze 1 te using MFT process 56 kWh assuming 50% efficiency, (i.e.15% available energy from CHP)

Membranology: Spin of the University in 2013

• Membrane and fluid characterisation • Process innovation • Laboratory equipment • Consultancy • Continuing professional development

Undertaken several small projects and Innovate UK grants • Mainly with water processing and resources recovery systems

Thanks very much !

Aknowledgements.

– Myrto Zacherof

– Michael Gerardo

– Paul Williams

– Darren Oatley-Radcliffe