September 25th Dinner Meeting

ASCE Environmental and Water Resources

Technical Group

Membrane Bioreactors for Wastewater Treatment

September 25, 2012

Tony Elberti, P.E.

Mr. Elberti is a project engineer/manager with Gannett Fleming and has 13 years engineering experience designing wastewater treatment processes and facilities.

He received his Bachelor of Science from Penn State University in 1999 in Civil Engineering with a Minor in Environmental Engineering and his Masters of Science from Villanova University in 2005 for Water Resource Management.

Tony Elberti Biography – contd.

Mr. Elberti has been involved in several pilot studies utilizing the A2O process with various Membrane Bioreactor (MBR) technologies and has permitted and designed four MBR facilities in New Jersey.

Here at GF, his responsibilities include process modeling, permitting, design, evaluation, energy auditing and value engineering.

Membrane Bioreactors(MBR)

MBR Presentation Outline

• Definition

• Evolution of technology

• How MBR’s work

• Applications

• Key Suppliers – differences

• Advantages and Disadvantages

• Summary

What is an MBR?

• Directly integrates with the activated sludge process

• Incorporates a membrane instead of clarification and filtration for solids separation

• Achieves tertiary quality effluent

• Have been used in Japan since the 1970’s but are considered an emerging technology today in USA.

MBR Definitions

• Immersed Membrane – Directly submerged membrane

• External Membrane – Separate vessel to house the membrane

• Flux – membrane loading rate per unit of area [gfd – gal/sq ft/day]

• Effective Pore Size

• TMP – Transmembrane Pressure – Across membrane surface (PSI)

• Permeability – Flux divided by pressure (gfd/psi)

• Lumen – Open center of membrane

• MOS – Membrane Operating System

• MCT – Membrane Cassette Tank

MBR Evolution of Technology

Conventional Process with Membranes

MBR

Activated Sludge

Clarifier Filter Membranes*

Sludge Holding

Activated Sludge

MOS

Sludge Holding

*Microfiltration

Higher Mixed Liquor = Smaller Footprint

• Conventional Process w/ Membranes

– Lower MLSS/Sludge Age (SRT)

– MLSS ~ 2,000 to 4,000 mg/l

– Higher sludge yield

– Larger footprint

• MBR

– Higher MLSS/Sludge Age (SRT)

– MLSS ~ 8,000 to 16,000

– Lower sludge yield

– Smaller footprint

Relative Tank Volumes

Conventional Process

100%

MBR

25%

Value over Conventional Treatment

• Fewer process steps to achieve comparable effluent

• Eliminates sludge settling issues (filamentous)

• Smaller Footprint

• Modular expansion capability

• Reduced sludge yield

• Higher quality effluent

– Low turbidity

– Excellent nutrient removal

– High rejection of organics, solids, and microorganisms

– More resistant to biological upset

M ixed liquor inAeration Ta nk

Permea ted Wa ter

Membrane Operating Systems

Anaerobic

Basin

Typical MBR Process Flow Diagram

Anoxic

Basin

Positive Displacement Process Blowers

Treated Effluent

Fine ScreenPermeate Pumps

Pre-

Aeration

Basin

Submersible Mixers

Positive Displacement Scour Air

Blowers

Recycle Pumps

Membrane Cassette Tank

WAS

Immersed Membrane Cassettes

Anaerobic

Recycle Anoxic

Recycle

How Do MBR’s Work?

• Production Mode

– Permeate Pumps + Scour Air

– TMP Increases

• Relax Mode

– High TMP triggers relax mode

– Scour Air only

• Clean in Place

– Sodium hypochlorite

– Smaller pore size requires higher order cleaning

• Backpulse Mode

– Scour Air and Permeate Pumps Reversed

How Do MBR’s Work?

MBR Operation and Design Considerations

• Flux

– Average 9 – 14 gfd

– Maximum 20 – 30 gfd

• Pore size

– 0.4 – 0.04 micron

• Sludge Retention Time

– More than 8 days (20 – 50 days common)

• Operating MLSS

– 8,000 – 16,000 (as high as 40,000 mg/L)

TIME

TM

P

TERMINAL TMP

MBR Applications

• Retrofits – Upgrades of existing facilities

– Increased flow in existing tankage

– More restrictive effluent requirements

– Nutrient Reduction

– Add-on to existing biological process

• New Build

– Advanced Nitrogen and Phosphorus Removal

– Effluent reuse or recharge

– Limited area available (small footprint)

– Long SRT’s required

Injection Well

Intrusion

BarrierSeaLevel

GOLF

COURSE

IRRIGATION

REUSE FOR SELECT

AGRICULTURE

WETLANDS

AUGMENTATION

URBAN

IRRIGATION

GROUNDWATER

AUGMENTATION

COOLING WATER

MBR APPLICATIONS

LIMITED SPACE

MARINE

GREEN LIVING

MBR: Key Players & Differences

Hollow Fiber MembraneFlat-Sheet Membrane

MBR: Flat Sheet vs. Hollow Fiber

Flat-Sheet Membrane

Diffuser case

Tube

Diffuser

Membrane case

Hollow Fiber Membrane

Diffuser

ManifoldManifold

MBR Advantages and Benefits

• Small footprint

• Reuse opportunities

• High quality effluent

• Nutrient credit potential

• Robust biological process

• Modular system – expandable

• Reduced disinfection requirements

• Capital and operational costs on decreasing trend

MBR Disadvantages and Limitations

• Limited flow capacity – equalization required

• Membranes subject to fouling and failing

• High capital and operating costs

• Cleaning chemicals necessary

• Increased foam potential

• Fine screening required

• More complex operations

MBR Summary

• MBR emerging technology capable of producing high quality effluent in a compact footprint

• Capital and operational costs still relatively high, but becoming more competitive

• Fine screening and Upstream BNR process

• More complex operations than conventional

• Robust biological system increased stability

• Numerous Reuse Applications

Questions