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