Affordable Membrane Quality Effluent

Integrated Membrane Fixed-Film Activated

Sludge (IMFAS): Affordable Membrane Quality Effluent

Sarah Hubbell – Entex TechnologiesJeff Devine – Ashbrook Simon Hartley

Andrew Shuler – U. of New MexicoClaudia Gunsch – Duke University

Sneak Preview

• MBR = Expensive• Sustainable membrane treatment• Benefits of IFAS• Pilot testing at N. Durham• Positive Conclusions

MBR Advantages

• High Quality Effluent• Small Footprint

MBR Disadvantages

• High Capital Cost• High energy requirements• High maintenance costs

Standard MBR Process

Process Flow

Wastewaterinlet

Membrane

High rateclarifier

MembranefeedA

naero

bic zo

ne

Aero

bic d

igeste

r

An

oxic zo

ne

Aero

bic zo

ne

6 mmscreen

Permeate

Permeatestorage

Backflush

Backwash Waste

NaOCl

RAS WAS

Reuse

High ratebiological process

NO3 recycle

Alternative: Integrated Membrane Activated Sludge

Integrated Fixed-Film/Activated Sludge

Increases Effective Biomass

Upgrades without new real estate and tanks

For BOD – Ammonia – Total N

Does not increase clarifier solids loading

BioWeb - New York City - 1996

IFAS Benefits

Improves Operation

Improves system stability

Resists toxic and hydraulic shock loads

Better solids settling – lower SVI’s

Reduced Sludge Production

BioWeb

Greensboro, NC - 1997

Integrated Membrane Fixed-film Activated Sludge (IMFAS)

• Minimizes membrane area 20 gpf/ft2 ADF – 40 peak

• 6 mm single set of pre-screens vs. 1 - 2 mm dual screening

• Energy Savings vs MBR no air scour blower

less process air required due to better O2 transfer

Prescreening Requirements

• MBR: Fine 0.5 mm – 2 mm screens

• IMAS: Standard 6 mm screens

Footprint

• MBR: Aggressive bioreactor HRT

• IMFAS: Higher rate bioreactor & clarifier than conventional

activated sludge

• Bioreactor footprints are similar

Fouling = Maintainence

• MBR: High MLSS = high fouling

• IMFAS: Clarified effluent = low fouling

Better Oxygen Transfer

WE&TNov 2006Fine pore Coarse pore Mechanical

Alp

ha

MLSS, g/l

MBR

IMAS

Decr

easi

ng E

nerg

y C

onsu

mpti

on

• MBR: requires membrane air scour & MLSS recirculation pumping

• IMAS: no air scour, no recirc pumping

Greater Energy Efficiency

Power ConsumptionMBR @ 10k ppm MLSS & Cyclic Air Scour

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

MBR IMAS

Mis c ellaneous

R ec irc ulation P umps

Membrane A ir S c our

P roces s A ir

Higher Membrane Fouling Feed = Higher Capital and O&M Costs

Membrane Fouling Environment

MBR

IMAS

En

erg

y C

on

sum

pti

on &

Mem

bra

ne A

rea

10,000 GPDPackagePlant

Duke University IMFAS Study

• Both suspended and fixed biomass

• IMFAS HRT is lower than an MBR• Smaller footprint

• IMFAS biomass settles faster• Smaller clarifier

Pilot Trailer at N. Durham WWTP

BioPortz

Without Biomass

With Biomass

Plastic—HDPE

Pilot Trailer Setup

Anaerobic Anoxic Aerobic

Clarifier Membrane Unit

Nitrate recycleRAS

RAS

Two Train Setup

• Anaerobic-anoxic-aerobic system (A2O)• IMFAS train: BioPortz in both aerobic reactors

Anaer. Anoxic Aerobic

IMFAS train

IMAS train

HRT (h) = 1 1 1 2 2

Pilot Equipment

Kinetic Benefit of IFAS

0.00

0.20

0.40

0.60

0.80

1.00

1. Anaerobic 2. Anoxic 3. Aerobic 1 4. Aerobic 2

NO

3/N

H3

ra

te

Suspended phase

Attached phase

IFMAS Pilot Results

IFMAS Pilot Results

• Delivers Membrane Quality Effluent

• Offers Much Lower Energy Consumption

• Requires Less Membrane

• Competitive Footprint