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1

Workshops – Session 3.1

Water Reuse

Tuesday - February 25, 2014

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2

Membrane Technology in WastewaterReclamation / Reuse

TorOve Leiknes, Gary Amy 

KAUST – King Abdullah University of Science and TechnologyWDRC – Water Desalination and Reuse Center

([email protected])

Workshops – Session 3.1Water Reuse

Tuesday - February 25, 2014

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Outline

The evolution of wastewater treatment (WWT)Brief history of membrane technology applied to WWT

Changing paradigms of advanced WWT

Key aspects of MBR technologyPros and cons of MBR technology

Key challenges in MBR technology

The potentials of membranes in advanced WWT

Summary

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Conventional wastewater treatment:

Primary Secondary   Tertiary

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Membranes in WWT

50 years evolution:

GACRO

Sand filter 

AS

Air stripping

Sludgetreatment

RecarbonationGACRO

Sand filter 

AS

Air strippingAir stripping

Sludgetreatment

Recarbonation

MF/UF RO

AS

Sludgetreatment

Pre-treatment

MF/UF RO

AS

Sludgetreatment

MF/UF RO

AS

Sludgetreatment

  Sludgetreatment

RO

MBR Pre-treatment

1. For tertiary treatment

2. Process optimization

3. Replace conventional treatment4. Membr 

ane bioreactors

5. ……… ?

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Membranes and wastewater:

End of 1960’s:

- UF: for municipal wastewater, sludge separation in AS (1969)

1970’s and 1980’s:

- MF/UF of industrial wastewater (f.ex. textile industry, oily wastewater,

separation of metals, organic compounds)- In connection with separation in anaerobe digestion

1990’s:

- Membrane bioreactor concepts

- Submerged MBR becomes “state-of-the-art”

 Application distinction:Municipal / industrial

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Membranes and wastewater:

Why the interest in MBR developments?

1989: Proto type of current MBR solutions, Yamamoto et.al. 

• Flux: ~ 3-9 LMH

• Sludge: 10-11 kg/m3

•TMP: ΔP ~ 1.33 bar 

 • Energy: 0.007 kWh/m3

• Treatment efficiencies:- 93 - 95% COD

- 94 - 99% TOC

- no SS

(Gander et al., 2000)

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MBR is a proven technology:

Yamamoto, 2009:

Evolution of development and

implementation of membrane

technology (MBRs) in WWT.

Global trends / markets:

In < 15 yrs from 1 to ~ 500 mill USD

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 Advanced WWT:

“The driving factor for the

growth of this market is

waster stress…”

Non-conventional water sources (impaired water quality)

Need to recycle and reuse wastewater

The concept of “fit for purpose”

Stricter environmental regulations worldwide

Need for new advanced WWT technologies

Sustainable wastewater management practice

Why the interest of

membranes in advancedWWT?

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Changing paradigms…

The status of the global water resources is changing

There is an increasing demand for water

Water scarcity is becoming a daily reality for millions

Many factors are affecting both quality and availability

In some regions non-conventional / impaired quality watersources are becoming the norm

There is a need for new and efficient treatment

technologies

The concept of “fit for purpose”… treatment options?Sustainable water management solutions are required for

the future

The result, changing paradigms in WWT…

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Changing paradigms…

 Advanced wastewater treatment

Changing paradigm – a shift from CAS to MBR

Wastewater is a resource!

WWT can be a resource factory

The water itself! wastewater reclamation / reuse

Constituents in the water (i.e. phosphorus, nutrients etc.)

Energy (i.e. heat, bio-gas etc.)

Product formation (i.e. bio-polymers etc.)

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Basic principles of MBRs:

Replacing sedimentation inCAS with membrane

filtration for the separation

of biomass from the

aqueous phase.

Principle of an AS-MBR process:

http://www.thembrsite.com/feature_reducing_energy_demand.php

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MBR technology

Biological process Membrane process

 Aeration

Feed characteristics

Hydraulics

Membrane module

Biomass characteristics:- Floc structure- EPS (free/bound)

Bulk characteristics:- viscosity

Membrane fouling:- reversible / irreversible

Clogging:- membrane channels- aeration system

Aerobic phaseMass transfer

Air scouringCleaning

Retention times:

- Hydraulic (HRT)- Solids (SRT)

Flux / TMP

FoulingCleaning

Membrane characteristics- pore size / surface properties

Module configuration- Geometry / dimensions

Composition of feedTreatment requirements- Nutrient removal- End use of treated water

 O p er  a t i  n g p ar  am e t  er  s 

   O  p  e  r  a   t   i  n  g  p  a  r  a  m

  e   t  e  r  s

Interactions,

“Fouling”

Process parameters

biological

membrane

hydrodynamics

Interaction between the biological

and membrane processes

Membrane fouling is a major

problem - biofouling

Fundamentals and key aspects of MBR technology:

   1   9   8   0

   1   9   8   5

   1   9   9   0

   1   9   9   5

   2   0   0   0

   2   0   0   5

   2   0   1   0

0

1000

2000

3000

 c  u  m  u   l  a   t   i  v  e  n  u  m   b  e  r  o   f  p  a  p  e  r  s 

publication year

scientific publications 1983-2010

55% published in 2006-2009

biofouling is a major problem

but what is biofouling?

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What is biofouling?

Is it the biofilm itself or constituents ofthe biofilm?

How significant is the floc structure?

How significant is the EPS? “Bound vs.free”?

What is the composition of the EPS?

Which is more important,polysaccharides – proteins?

How should it be measured / reported orquantified?

Does composition / structure change?

How dynamic is biofouling?

Can it be removed?

Biofilm “fingerprinting”?

Is quorum sensing a key phenomenon?

How sensitive is the biofilm interactionto stress?

Behavior

Response

Impact

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Why the concern on biofouling?

 Advanced water treatment = energy water  - energy nexus

Example USA:

3% of total electricity generated is

consumed for water and wastewater

treatment

by 2016, water treatment is expectedto consume >100 mill ion kWh / day

increase of 30% from 1996 levels

60-75% of the energy required is

consumed in the aeration processes

more stringent requirements = more

energy demands

MBRs are considered energy intensive

MBRs aeration demands:

► 38 % - membrane air scouring

► 35 % - aerobic biological process

Source

www.gewater.com

Biofouling mitigation and control 

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Key MBR issues:

The key issues of MBRs:

High aeration demands (e.g. energy)

Membrane fouling, biofouling in particular  

Design of membrane filtration units

Changes in biological treatment processes

Membrane cleaning

What are the MBR advantages / disadvantages? 

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MBR cons…

Commonly expressed concerns about MBRs:

MBRs are too energy demanding

Plants are expensive, high investment costs 

Complicated operations, membrane maintenance / cleaning

Need more skilled personnel

Membrane life-time and replacements

Does not eliminate the need for advanced post-treatment (e.g. RO)

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MBR energy…

Biofouling mitigation and control by:

- choice of operating modes (e.g. aeration)

- improved module and reactor designs (e.g. CFD)

 Aeration in MBRs:

• Membrane module operation – air scouring

• Bioprocess operation – oxygen for aerobic degradation

• Coarse bubbles - membrane operation

• Fine bubbles - bioprocess operation

Can represents 70-80% of the

energy demands!

 Anoxic AerobicPre-treatedwastewaterSludge recirculation

Permeate

 Air

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MBR aeration

Biological needs:

• Objective:

• Oxygen transfer for aerobic

degradation

• Practice:

• Fine bubble diffusers

• Challenge:

• Change in fluid viscosity

• Poorer masstransfer efficiencies,

more energy

• High operating costs

• Change in biomasscharacteristics?

Membrane needs:

• Objective:

• Generate crossflow hydrodynamic

conditions

• Generate high shear stress on surface

• Remove deposition on membrane surface

• Practice:

• Continuous aeration for air scouring

• Intermittent aeration (on/off cycles)

• Relaxation techniques (no production

during aeration)

• Challenge:

• High specific aeration demands

• High operating costs

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MBR aeration

- Same fundamental Monod kinetics apply

- Process must be designed for oxygen necessary to degrade both organic

matter and to convert NH4 to NO2/NO3 as required- Determines oxygen transfer rate (OTR)

Challenge:

- Parameters in OTR equation affected by high SS concentrations

- Particularly viscosity and the α -factor

- Correlations have been proposed

where µ is viscosity (kg/(m s))

x is the correlation exponential

MBR: MLSS of 12 g/L → α -value of 0.6

CAS: MLSS of 3-5 g/L → α -value of 0.8

Consequence → higher aeration demand 

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MBR aeration

Impact of aeration on aerobic process (modeling):

Deterministic – including biofouling products into the ASM models foractivated sludge

 Aspects included:

- affect of aeration on the behavior of SMP and EPS

- biomass associated products (BAP), best observed in endogenous respiration conditions

- uptake associated products (UAP), which are released during the consumption of a substrate

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MBR aeration

EPS / SMP behavior as a function of SRT

Modeling Yobs as a function of SRT

20-40 days optimal SRT for

minimizing foulant species

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MBR aeration

P. Cote et al. Desalination 288 (2012) 145–151

Before  After

Significance of aeration:

- reduced sludging

- reduced fouling- more efficient systems

Tremendous efforts in R&D

have reduced aeration

demands, increased

efficiencies, yet aeration isstill one of the key energy

issues in MBRs.

Example GE Zenon 

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- Influence of aeration mode

MBR module designs:

- Influence of module design

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- Impact on module design

(open vs, closed)

- Air loads

- Choice of aeration cycling

- Impact on hydraulics

Example: modeling a full-scale plant, FS modules

(EUROMBRA project)

MBR module designs:

Resulting biofoulingbehavior? 

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Photographs of

fouled flat-sheets

Computed shear-stress

distribution (0-4 N/m2)

- insights into the air distribution within a module

- shear stress distribution on the surface of the flat-sheet membranes

(EUROMBRA project)

Example: CFD modeling of aeration, FS modules

MBR module designs:

• Improved module design and performance

• Less fouling

• Less energy consumption 

R

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MBR developments:

In summary;

Great steps and achievements have been accomplished in

making MBR a viable advanced wastewater treatment option.

Stipulated average annual

growth rates

Large regional difference

China and Middle East key

future markets

Region 

 Annual growth 

(% / year) 

N. America 

15 % 

Middle East  25 % 

Europe  10 % 

 Asia Pacific  10 % 

China  20 % 

Japan  10 % 

Total  20 % 

Market prediction growth rates:

MBR

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MBR pros…

Commonly expressed benefits of MBRs:

Consistently high effluent water quality

Competitive to advanced tertiary WW treatment 

Small foot-print, compact treatments plants

Modular, can be scaled to any treatment plant size

Well-suited for retrofitting / upgrading

Produces high quality water well-suited for reclamation / reuse

MBR

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MBR pros…

Effluent water quality:

What can be achieved by MBR processes?

Effluent BOD < 5 mg/L

Effluent TSS < 5 mg/L

Total Phosphorus < 1 mg/L

Total Nitrogen < 8 mg/L (lower if DN)

 Ammonia < 1 mg/L

Turbidity < 0.4 NTU

Bacteria up to 6 Log Removal

Viruses up to 3 Log Removal

COD, TSS, N, P

Example of removal efficiencies: 

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Example of hygienic capacity compared with CAS:

Organism Size (um)

Enteric Virus 0.025 –  

0.075

Coliform Bacteria 1 –  3

Cryptospoidiumoccyst

3 –  8

Giardia cyst 7 - 14

1,00E+00

1,00E+01

1,00E+02

1,00E+03

1,00E+04

1,00E+05

1,00E+06

1,00E+07

1,00E+08

1,00E+09

1,00E+10

Coliforme Esch.-Coli

   C   F   U

  p  e  r   1   0   0  m

   l

Influent

Effluent CAS

Effluent MBR

Guide value

Hygienic parameters

MF / UF

(Brepols. 2010)

No need for additional disinfection

MBR pros…

MBR

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Compound MBR Rejection (%) CAS Rejection (%)

Estrone 94 – 99 88 – 98

17-β-Estradoil 96 – 100 91 – 98

17-α-Ethinylestradiol 82 – 94 60 – 100

Bisphenol A 93 – 100 83

Nonylphenol 81 -

(Hegemann et al., 2002; Zuhlke et al., 2003; Clara et al., 2004)

Comparing MBRs capacity to remove emerging compounds of

concern compared with CAS – e.g. EDCs:

MBR pros…

MBR

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MBR pros…

Costs / energy consumption:

Example – GE Zenon; drop in relative membrane costs, increased capacity

P. Cote et al. Desalination 288 (2012) 145–151

The costs of MBRs have dropped drastically through commercialization

Extensive R&D efforts have increased unit capacities

Energy to operate systems keeps dropping.

Costs  Capacity

MBR

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Investment cost, new and retrofitted WWTPs

1989 - 2006

0

200

400

600

800

1000

1200

1400

16001800

2000

0 10 20 30 40 50 60 70 80 90 100

Treatment Capacity, MLD

   S  p  e  c   i   f   i  c  c  o  s   t ,   E   U   R  p  e  r   P   E

CAS

CAS with tertiary treatment

MBR

Cost function (all WWTPs)

Comparison of CAS – MBR

Erftverband, Germany(Brepols, 2009)

Investment costs

Energy consumption,

(~ 0,9 kWh/m3)

MBR pros…

MBR

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Example – Nordkanal, Germany:

MBR pros…

MBR footprint compared to CAS:

MBR pros

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energy consumption < 0,7

kWh/m3 can be achieved

Case study -

Heenvliet WWTP,

The Netherlands

(EUROMBRA project)

MBR pros…

Retrofit / upgrade:

MBR

MBR status

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MBR status…

MBRs, a proven technology!

• Competitive for tertiary treatment requirements

• BAT for wastewater reuse / recycling

MBR

Large scale installations

Retrofitting / upgrading

Package plants

MBR vs CAS TF?

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MBR vs. CAS-TF?

Principle: MBR CAS-TF

Bioreactor with MF/UF Clarifier – Bioreactor – clarifier – MF/UF

Case study: (P. Cote et al. Desalination 167 (2004) 1-11)

Process performance:

- Suspended Solids: both below detection limit

- Physical barrier on microorganisms: both- MBR has higher MLSS conc., better control of SRT, more diversified biomass

giving overall improved removal of COD/SOCs

- MBR has enhanced TN removal

- Phosphorous removal similar in both

- MBR better than CAS-TF

MBR vs CAS TF

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MBR vs. CAS-TF

Comparison of plant size, capital costs, O&M costs, Total life-cycle costs:

Size defined by HRT and plant surface area: 

MBR

CAS-TF

MBR

CAS-TF

HRT – MBR 75% (small plants) to 50% (large plants) < CAS-TF

Land space – MBR is about 50% of CAS-TF 

MBR vs CAS TF

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MBR vs. CAS-TF

Costs – 1. capital. 2. O&M, 3. life-costs

1.

2.

3.

1. capital: MBR < CAS < CAS-TF 

- eliminating secondary clarifiers

- reduced size of aeration tanks

- reduced footprint

- all offset added costs for the

membrane system and fine screens

2. O&M: CAS < CAS-TF < MBR

- CAS-TF/MBR similar, 20-30% > CAS

- MBR > CAS-TF mainly from

membranes air scouring

3. life-costs: CAS < MBR < CAS-TF 

- (20 years, 6% interest rate, 2.5% inflation rate)

- membrane filtrated wastewater compared

to CAS, adds 5-20% on total life-cost

depending on plant size

MBR post treatment

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MBR post-treatment…

“Post-treatment”

What if the water quality after MBR / CAS-TF is not enough?

“pretreatment” to NF/RO

 AOP – advanced oxidation processes

mineralization and water stability

ensuring water hygiene

Post-treatment options: 

MBR post treatment

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MBR post-treatment…

Potentials of MBR / CAS-TF with post-treatment:

Removal of unregulated compounds:

Emerging disinfection by-products (DBPs) (e.g., NDMA)

Endocrine disrupting compounds (EDCs):

Steroidal hormones (e.g., estrone)

Bisphenol A

Pharmaceutical active compounds (PhACs) and other emerging organic

contaminants

analgesics, antiepileptics, lipid regulators, antibiotics

flame retardants, 1,4-dioxane

MBR post treatment

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MBR post-treatment…

DOC removal during Pilot-Scale MF/RO and MF/NF (Drewes, 2003)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Tertiary effluent

mean

NF-90 NF TFC-S RO TFC HR RO TFC HR

full-scale

   D   O   C   (  m  g   /   L   )

0.430.34 0.24 0.16

Composition?

TOC < 1.0 mg/L

but 1 mg/L = 1,000 μg/L = 106 ng/L!

MBR post treatment

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MBR post-treatment…

Rejection of Pharmaceuticals / EDCs with MF/RO (Drewes, 2003)

445

15

65

40 35

115100

 n.d.n.d.n.d.n.d.n.d.n.d.<10

0

50

100

150

200

250

300

350

400

450

500

  c  a  r   b

  a  m  a  z

  e  p   i  n

  e

  d   i  c   l  o   f  e  n

  a  c

  g   e  m   f   i   b

  r  o  z   i   l

   i   b  u  p

  r  o   f  e

  n

   k  e   t  o

  p  r  o   f

  e  n

  n  a  p  r

  o  x  e  n

  p  r   i  m

   i  d  o  n

  e

  n  g   /   L

Scottsdale tertiary effluent

Scottsdale tertiary effluentafter MF/RO

18.9

186

0.17   0.060

20

40

60

80

100

120

140

160

180

200

NP/OP Total APEO Total APEC

  m   i  c  r  o  g  r  a  m   p

  e  r   l   i   t  e  r

RO-Feed

RO (TFC-XLE) permeate

WR-199A

Pharmaceuticals: full-scale MF/RO 

EDCs: pilot-scale MF/RO 

MBR post-treatment

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MBR post-treatment…

Comparing NF vs. RO as a post-treatment option:

Rejection of hydrophilic non-ionic organics 

Rejection of hydrophilic ionic organics

0

0.2

0.4

0.6

0.8

1

100 150 200 250

Molecular weight (Da)

   R  e   j  e  c   t   i  o  n

ESNA

RO-XLE

NF – ESNA

RO - XLE

0

10

20

30

40

50

60

70

80

90

100

   N  a  p

  r  o  x  e

  n

  d   i  c

   l  o  f  e  n  a

  c

   i   b  u  p

  r  o  f  e  n

  m  e

  c  o  p  r  o  p

   k  e  t  o  p  r  o  f  e  n

  g   e  m

  f   i   b  r  o  z   i   l

   P  r   i  m

   i  d  o  n

  e

   R  e   j  e  c   t   i  o  n   (   %   )

Jo/k=1.3

DI

Jo/k=1.3

EfOM

TFC-HR

0

10

20

30

40

50

60

70

80

90

100

   N

  a  p  r  o  x  e  n

  d   i  c   l

  o  f  e  n

  a  c

   i   b  u

  p  r  o  f  e  n

  m  e  c

  o  p  r  o  p

   k  e

  t  o  p  r  o  f  e  n

  g   e  m  f   i   b  r

  o  z   i   l

   P  r   i  m

   i  d  o  n  e

   R  e   j  e  c   t   i  o  n   (   %   )

Jo/k=2.4

DI

Jo/k=2.4

EfOM

TFC-SR2

N/A

DI

EFOM

DI

EFOM

MWCO = 100 Da vs. 400 Da

Summary

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Summary

In a changing world with water scarcity reclamation / reuse of

wastewater is becoming a necessityChanging paradigms of advanced wastewater treatment

MBRs are a realistic, viable solution to advanced treatment

for high quality effluents treating water of impaired quality

CAS cannot meet current standards for wastewater reuse

MBR has been shown to be a better solution than CAS-TF

MBRs with post-treatment can provide very high effluent

qualities well suited for multiple reuse purposesTreatment scheme can remove unregulated emerging

contaminants of concern

The technology is available, advancement in regulations and

policies are needed

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46

Part II

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47

Looking towards future MBR solutions inwastewater reclamation / reuse

TorOve Leiknes, Gary Amy 

KAUST – King Abdullah University of Science and Technology

WDRC – Water Desalination and Reuse Center

([email protected])

Workshops – Session 3.1Water Reuse

Tuesday - February 25, 2014

Outline

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Outline

“Rethinking” MBR systemsLooking for new MBR solutions for wastewater reuse

New trends and directions

Coupling alternative biological processes with membrane

separation technologies

Overview of novel MBR systems being developed

Where is MBR development headed?

Summary

Statement:

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Statement:

MBRs, is a proven technology!• Competitive for tertiary treatment requirements

• Competitive for for wastewater reuse / recycling

MBR developments

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MBR developments

“Rethinking” MBRs…

1. MBR reactor designs 2. Biological processes 3. Novel / hybrid solutions

Overall reactor designs and

hydraulics – CFD

Membrane module designs

Improved air-scouring

systems (e.g. less energy)

 Alternative filtration unitdesign / operation

Improved hydrodynamics

Biofouling mitigation

- new membrane materials

- anti fouling surfaces

- quorum sensing

Using alternative biological

process

Biofilms vs. suspended

 Aerobic vs. anaerobic

Nutrient removal

Removal efficiency ofemerging contaminants

Biological product formation

(e.g. biogas, biopolymers)

Implementing microalgae

systems

Coupling MBRs with other

unit processes: coagulation,

adsorption, AOP etc.

 Alternative membrane

separation systems: NF,

FO/PRO, MD, MABR etc.

Potentials of algae MBR

solutions

Integrated systems

1 MBR reactor designs:

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1. MBR reactor designs:

Large-scale CFD vs. modules: (Example Nordkanal plant, EUROMBRA project)

Impact of inlet design / construction

Impact of additional mixers

1 MBR reactor designs:

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1. MBR reactor designs:

Enhanced membrane filtration reactor design:

I. Ivanovic & T.O. Leiknes, The biofilm membrane bioreactor (BF-MBR) - a review, Desalination and Water Treatment, 2012, 37 (1-3), 288-295

?Completely mixed reactor (CM-MR)

→ CM with sludge hopper (SH-MR)→ modified SH-MR (MSH-MR) 

BF-MBR- one step system

- membrane unit for enhanced

particle removal

- alternative fouling controlstrategies 

1. MBR reactor designs:

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1. MBR reactor designs:

Performance of alternative membrane reactors:

General:

• Separation factor (Ks) increased; CM-

MR → SH-MR → MSH-MR

• Fouling rate decreased drastically

CM-MR

SP-MR

MSP-MROperation:

• TMP to express fouling rate;CM-MR → SH-MR → MSH-MR

• Lowest fouling rate for MSH-MR

• Why?

1. MBR reactor designs:

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1. MBR reactor designs:

Impact of colloidal fraction on membrane filtration:

Inlet

Example of PSD analysis:

• Zones in MSH-MR unit

Reduction in colloidal fraction correlates with improved performance!

Summary:

1. External membrane reactor should be designed as an enhanced particle

separation unit (with focus on colloidal material)

2. Reactor design will affect composition of water around the membrane and thus

fouling rates and overall performance

3. Potential to reduce air scouring for sustainable operation, i.e. energy

1. MBR reactor designs:

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1. MBR reactor designs:

 AS - fouling BF - fouling

Understanding membrane fouling: AS: BF:

24 hours

168 hours

312 hours

 Applying CLSM techniques 

Estimates biofouling

porosity / hydraulicresistance

Understanding biofouling in MBRsystems will be an ongoing activity

in all future developments as a

function of operating conditionsand system design! 

2. Biological processes:

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2. Biological processes:

Can the biology be done differently? Comparing aerobic and anaerobic processes:

Pros and cons:

• anaerobic – low sludge production

• anaerobic – potentially net energy balance

• aerobic – higher kinetics, nutrient removal

• plus, plus…

(Veolia)

2. Biological processes:

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g p

Matching the biological treatment to the reuse purpose

 Agricultural reuse

Crops for human consumption

Crops for animal feed

Urban landscaping (e.g. parks)

Recreational (e.g. golf courses)

Water needs:

- plant nutrients / fertilizers- emerging compounds of

concern

- water hygiene / risk

- environmental impacts

Industrial reuse

Cooling water

Process water

Water needs:

- low TDS

- ultra-pure water

- water stability

- tailored properties

Potable reuse

Direct reuse

Indirect reuse (e.g. aquifer

recharge, reservoirs)

Water needs:

- meet drinking water

standards

- emerging compounds ofconcern

- water hygiene / risk

- disinfection by products

- nutrient removal

 Anaerobic / Aerobic Anaerobic

2. Biological processes:

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 Anaerobic - MBR

g p

H. Ozgun et al. / Separation and Purification Technology 118 (2013) 89–104

Alternative An-MBR flow schemes:

2. Biological processes:

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 An-MBR

g p

 Adapted from: H. Lin et al. / Desalination 314 (2013) 169–188 

Comparing:

Well suited for high strength wastewater

Energy aspects; low requirement – net production (e.g. biogas)

Still relatively low fluxes, biofouling more of a challenge than in MBR

Full commercial large-scale systems still not available

Pros and cons:

2. Biological processes:

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Effluent

Influent

Excess sludge

Gas collectionAir

(recycle)

Aerobic BF

Anaerobic BF/AS

 Anaerobic / Aerobic - MBR

g p

Systems integration:

One-stage (upflow)

Multiple biological processes

Multiple use of aeration

Integrated solids management

Energy recovery

Maximizing biological processes

with membrane separation

3. Novel / hybrid solutions:

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y

Membrane distillation MBR (MD-MBR)

Examples of novel processes being developed:

http://www.desalination.biz/news/magazine

 _article.asp?id=5145&title=

Principle:

Water vapor is extracted

from the wastewater and

condensed on the permeate

side.

System developments:

Relatively high temperature in biological

reactor – thermophilic bacteria

 Application to wastewater treatment has

been limited

Mainly laboratory scale results found in

literature

R&D phase at small scalePotential of concept is acknowledged

3. Novel / hybrid solutions:

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y

MD-MBR case study:

Phattaranawik et.al. Desalination, doi:10.1016/j.desal.2007.02.075

System status:

No wastewater

treatment to

date

R&D phase at

small scale

Overall summary:

Very high quality effluent achieved

Low fluxes

Need waste-heat for economic

operation

Membrane integrity an issue

3. Novel / hybrid solutions:

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y

Forward osmosis MBRs (FO-MBR)

Concept principle: 

 A. Achilli et al. / Desalination 239 (2009) 10–21 

 J.-J. Qin et al. / Water Science & Technology—WST 62.6 (2010) 1353-1360 

Study comparing MBR with FO-MBR:

3. Novel / hybrid solutions:

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Forward osmosis MBRs (FO-MBR)

System status:

No full-scale commercialization to date

R&D phase at small scale

Challenges in FO-MBR development:

Choice of draw solution and applicability to wastewater reclamation

Competitive fluxes compared to other membrane processes

 Although on average less, membrane fouling is still an issue

Waste management

FO-MBR potentials:Very high effluent qualities, f.ex. 99% TOC and 98% NH4

+-N removal

efficiencies

Less membrane fouling, easier cleaning by backwashing

3. Novel / hybrid solutions:

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y

Membrane aerated bioreactors (MABR)

Treatment concept:

Principle: • Gas permeable membrane supplies oxygen directly to the

biofilm – no bubbles, optimal mass transfer, less energy

• Biofilm stratification provides both aerobic and anaerobic

zones allowing flexible bioreactor designs

• Efficient simultaneous nitrification / denitrification

• Potential biological conversions of recalcitrant emerging

contaminants (e.g. pharmaceuticals)

• Combined aerobic and anaerobic reactor

• Gas transfer membranes (e.g. oxygen)

• Minimization of energy for aeration

• Selection of specialized biomass for desiredconversions

DO COD

Air

Water flow

Biofilm

Gas permeable membrane

Air

Water flowBiofilm

DO COD

System status:

No commercialization to date

R&D phase at small scale

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