Membrane Bioreactors Short Course Abstracts - National Water ...

Published by the 

National Water Research Institute 

NWRI-2006-02 

10500 Ellis Avenue • P.O. Box 20865 

Fountain Valley, California 92728-0865 USA 

(714) 378-3278 • Fax: (714) 378-3375 

www.NWRI-USA.org

Conference Planning Committee 

Chair: 

✦ SAMER S. ADHAM, Ph.D., MWH 

✦ SIMON J. JUDD, Ph.D., Cranfield University 

✦ GINA MELIN, National Water Research Institute 

✦ JEFFREY J. MOSHER, National Water Research Institute 

✦ TAMMY RUSSO, National Water Research Institute 

Sponsors 

The Conference Planning Committee is indebted to the following organizations and 

corporations whose support has helped make this conference a success. 

✦ NATIONAL WATER RESEARCH INSTITUTE 

✦ MWH 

✦ CRANFIELD UNIVERSITY 

✦ USFILTER 

✦ ZENON ENVIRONMENTAL CORPORATION 

✦ ORANGE COUNTY WATER DISTRICT 

✦ CORONA DEPARTMENT OF WATER AND POWER 

A Short Course on 

Membrane Bioreactors 

iii

Foreword 

ICROFILTRATION IV is the fourth in a series of conferences sponsored by the National 

MWater Research Institute (NWRI) devoted to low-pressure membrane (microfiltration 

and ultrafiltration) applications to water and wastewater treatment. 

Since the first NWRI-sponsored Microfiltration Conference in 1994, the technology has 

advanced and become a popular alternative to conventional treatment. MICROFILTRATION IV 

provides an update on the status of the technology and a focus on critical issues faced by 

end-users, such as new applications, regulatory perspectives, operational experiences, and 

fouling control. 

A special feature of MICROFILTRATION IV is a one-day short course on membrane bioreactors 

(MBRs), a promising technology that uses microfiltration to enhance the wastewater and 

reclaimed water treatment processes. The short course provides information on the state-of-the-art 

in MBRs and focuses on topics such as MBR design, procurement issues, and costs. 

The extended abstracts presented in this document were the contributions of conference speakers. 

The opinions expressed within the abstracts are those of individual authors and do not 

necessarily reflect those of the sponsors. 

NWRI gratefully acknowledges the efforts of all those involved with the planning, organizing, 

and sponsoring the conference, including MWH, Cranfield University, USFilter, Zenon 

Environmental Corporation, the Corona Department of Water and Power, and Orange County 

Water District. NWRI also extends special thanks to the conference moderators and speakers, 

whose expertise provided invaluable insight into the status and needs of membrane technology. 

NWRI would also like to extend sincere thanks to Gina Melin, Editor, and Tim Hogan, 

Graphic Designer, for their efforts in bringing this document to press and ensuring that the 

quality of each and every abstract reached their fullest potential. 

Lastly, this conference would not have been possible without the vision of Ronald B. Linsky, 

Executive Director of NWRI until his passing in August 2005. Ron will be fondly 

remembered for his energy, enthusiasm, and dedication to NWRI and the water community. 

Jeffrey J. Mosher 

Acting Executive Director 

National Water Research Institute 

Fountain Valley, California 



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Program and Contents 

WEDNESDAY, MARCH 22, 2006 

7:00 am - 9:00 am Registration Foyer of California Ballroom 

Session 1: Introduction 

California Ballroom 

Moderated by JEFFREY J. MOSHER, National Water Research Institute, California 

8:30 am - 8:45 am Welcome 

JEFFREY J. MOSHER, National Water Research Institute, California 

8:45 am - 9:15 am Membrane Bioreactors and ............................. 1 

the Future of Wastewater Treatment 

R. RHODES TRUSSELL, Ph.D., P.E., DEE, 

Trussell Technologies, Inc., California 

9:15 am - 9:45 am Biological Process Principles ............................ 3 

GEORGE TCHOBANOGLOUS, Ph.D., P.E., 

University of California, Davis, California 

9:45 am - 10:00 am Break 

Session 2: Fundamentals and Applications 

Moderated by SAMER S. ADHAM, Ph.D., MWH, California 

10:00 am - 10:45 am Membrane Bioreactor Process Fundamentals .............. 5 

SIMON J. JUDD, Ph.D., Cranfield University, England 

10:45 am - 11:05 am Commercially Available Membrane Bioreactor Systems ...... 11 

JAMES F. DECAROLIS, MWH, California 

11:05 am - 11:25 am Evaluation of Conventional Activated Sludge .............. 19 

Compared to Membrane Bioreactors 

R. SHANE TRUSSELL, Ph.D., P.E., 


11:25 am - 11:45 am Membrane Bioreactor Global Knowledgebase .............. 25 

GLEN T. DAIGGER, Ph.D., P.E., BCEE, NAE, 

CH2M HILL, Colorado 

11:45 am - 12:15 pm Panel Discussion 

12:15 pm - 1:30 pm Lunch The Atrium 



vii

Session 3: Case Studies – Real-World Issues with Membrane Bioreactors 

Moderated by GEORGE TCHOBANOGLOUS, Ph.D., P.E., 

University of California, Davis, California 

1:30 pm - 2:00 pm Design, Procurement, and Costs of. ...................... 29 

Membrane Bioreactor Systems 

STEPHEN M. LACY, P.E., DEE, MWH, Nevada 

2:00 pm - 2:20 pm Retrofit of an Existing .................................. 33 

Conventional Wastewater Treatment Plant with 

Zenon Membrane Bioreactor Technology 

DAVE N. COMMONS, 

City of Redlands Municipal Utilities Department, California 

2:20 pm - 2:40 pm Retrofit of an Existing .................................. 37 

Conventional Wastewater Treatment Plant 

with USFilter Membrane Bioreactor Technology 

JOHN HATCHER, Oconee County Utility Department, Georgia 

2:40 pm - 3:20 pm Membrane Bioreactor Applications: A Global Perspective .... 39 


3:20 pm - 3:45 pm Panel Discussion 

3:45 pm - 4:00 pm Break 

Session 4: Innovative Applications and Future Outlook of the Technology 

Moderated by R. RHODES TRUSSELL, Ph.D., P.E., DEE 


4:00 pm - 4:30 pm Membrane Aeration, Biofilms, ........................... 43 

and Membrane Bioreactors 

MICHAEL J. SEMMENS, Ph.D., P.E., 

University of Minnesota, Minnesota 

4:30 pm - 4:50 pm Future Outlook on Membrane Bioreactor Technology ....... 45 


4:50 pm - 5:15 pm Panel Discussion 

5:15 pm Short Course on Membrane Bioreactors Adjourns 

viii

THURSDAY, MARCH 23, 2006 ~ FIELD TRIPS 

8:30 am - 11:30 am Field Trips 

Those who are attending field trips must turn in field trip passes prior to bus departure. Please check in 

at the Foyer of the California Ball Room at least 30 minutes prior to departure. 

Field Trip Option A: 

MICROFILTRATION AT THE ORANGE COUNTY WATER DISTRICT 

The Groundwater Replenishment System Phase One plant is a 5-million gallon per day (mgd) 

advanced water treatment facility that contains three major processes: microfiltration, reverse 

osmosis, and advanced oxidation. The microfiltration 

process consists of a 6-mgd USFilter 

CMF-S submersible system. This process is a 

smaller-scale version of the 86-mgd microfiltration 

facility currently under construction at 

the same site. Driving time from the hotel to 

the Orange County Water District in 

Fountain Valley, California, is approximately 

20 minutes. 

Field Trip Option B: 

MEMBRANE BIOREACTOR AT THE CORONA DEPARTMENT OF WATER AND POWER 

Wastewater Treatment Plant 3 at the Corona Department of Water and Power was 

commissioned in 2001 to treat 1.1-mgd raw wastewater to Title 22 standards for recycling 

purposes. Currently, about 0.4 mgd of recycled water is 

produced, which is used to irrigate a nearby golf course 

and will soon irrigate surrounding schools and parks. 

The foundation for Plant 3 is the ZenoGem Process, a 

technology designed by Zenon that consists of a 

suspended growth biological reactor integrated with a 

microfiltration membrane system. Driving time from 

the hotel to the Corona Department of Water and Power 

in Corona, California, is approximately 35 minutes. 

Photos courtesy of the Orange County Water District, 

and the Corona Department of Water and Power 



ix

Abstracts 



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Membrane Bioreactors and 

the Future of Wastewater Treatment 

R. RHODES TRUSSELL, PH.D., P.E., DEE 

Trussell Technologies, Inc. 

Pasadena, California 

Adecade ago, membrane bioreactors (MBRs) weren’t even on our radar screen. Today, 

MBRs are the process of choice for small-scale reuse projects with demands for high 

water quality. Projects are popping up everywhere. Soon, MBRs will change the way we think 

about treatment for reuse, opening a new era of decentralized treatment. In the very longterm, 

just as membrane filtration will replace granular media filtration, MBRs will replace 

conventional biological processes that depend on gravity sedimentation or granular media 

filtration for solids separation. 

What is the appeal of the MBR? What are some of the limits of the process? How is our 

thinking about MBRs changing, and how will it change in the future? What problems must 

we solve for MBRs to reach their full potential? What can MBRs do to help us meet future 

regulations? 

The most obvious appeal of the MBR is that it produces an excellent effluent quality. The 

compactness of the MBR is another important element in its appeal. Finally, the MBR has 

great potential for automation. Important to both the design engineer and operator, the MBR 

eliminates the need for good sludge settleability as a central requirement. Effluent quality is 

less sensitive to operations, and precise control of the sludge residence time (SRT)/mixed 

liquor suspended solids (MLSS)/food to microorganisms (F:M) ratio is not as important. 

Finally, the MBR puts much greater distance between reclamation and the risk of microbial 

disease. Pathogens are not just reduced by a highly selective chemical or photochemical 

reaction, they are rejected by size exclusion. The MBR also makes longer SRTs feasible in a 

compact space, resulting in less biomass to waste, the removal of a broader variety of resistant 

compounds, and a more biostable effluent with a lower oxidant demand. Finally, the MBR 

produces an effluent that is immediately suitable for reverse osmosis treatment, should that be 

a requirement. 

In today’s world, there are two kinds of issues that we face in making decision about the 

deployment of MBRs: 

Type I Issues — Issues that must be resolved to improve reliability, cost, and/or 

performance. 

Type II Issues — Issues that are inherent to the process and must be understood by 

designers and operators of successful MBR projects. 

Correspondence should be addressed to: 

R. Rhodes Trussell, Ph.D., P.E., DEE 

President 


232 North Lake Avenue, Suite 300 

Pasadena, CA 91101-1862 USA 

Phone: (626) 486-0560 • Email: rhodes.trussell@trusselltech.com 



1

Examples of Type I issues are: (a) understanding the upper limits of the MLSS that the 

process can handle and how the reactor configuration affects this, (b) understanding the lower 

limits of SRT and hydraulic residence time (HRT), (c) the optimization of air scouring and 

energy consumption, (d) membrane cleaning, (e) design and operational practices that will 

extend membrane life, and (f) designing and operating the MBR process to optimize sludge 

filterability. 

Examples of Type II issues are the design and operation requirements imposed by the impact 

that fouling can have on hydraulic performance, by MBR’s limited ability to handle peaking, 

and on MBRs by reduced oxygen transfer at high MLSS. 

To date, most MBR installations have been small enough that it has basically been possible to 

ignore the biology. This will not do in the future. The future belongs to those who take full 

advantage of all that we have learned about the behavior of this complex biological system and 

integrate it with the unique capabilities and limitations of MBRs. Some examples of problems 

that must be addressed include: 

• The management of organisms associated with foaming. 

• The management of the biological system to produce a sludge that is easily 

filtered and dewatered. 

• The full integration of what we know about nutrient removal with the MBR 

process. 

In the meantime, there are places where MBR is attractive today, even for the conservative 

engineer. MBR is most appealing when its small footprint, ease of automation, and excellent 

effluent quality are all requirements. It is also most appealing when flow peaking can be 

easily addressed. Reuse projects that scalp the flow from nearby sewers are one of the more 

obvious examples. Moreover, MBR has the potential to rearrange our thinking about reuse. 

There are limits to the idea of pumping treated wastewater up into and throughout a 

community in purple pipe. MBR creates the potential for decentralized reuse systems with 

treatment systems located closer to the point of application and smaller, less-intrusive purple 

infrastructure. 

R. RHODES TRUSSELL, Ph.D., P.E., DEE, is recognized worldwide as an authority 

in methods and criteria for water quality and in the development of advanced 

processes for treating water or wastewater to achieve the highest standards. A Civil 

and Corrosion Engineer with 35 years of experience, he has worked on the process 

design for dozens of treatment plants ranging in size from 1 to 900 million gallons per 

day in capacity. At present, he is President of Trussell Technologies, Inc., an 

environmental engineering firm that focuses on the quality and treatment of water 

and wastewater. He is also active on numerous boards and committees, such as 

serving as Chair of the Water Science and Technology Board for the National Academies. Just recently, 

he retired from the U.S. Environmental Protection Agency’s Science Advisory Board after 17 years of 

service. Trussell received a B.S. in Civil Engineering and both an M.S. and Ph.D. in Sanitary 

Engineering from the University of California, Berkeley. 

2


Biological Process Principles 

GEORGE TCHOBANOGLOUS, PH.D., P.E. 

University of California, Davis 

Davis, California 

With proper analysis and environmental control, almost all wastewaters containing 

biodegradable constituents can be treated biologically. Therefore, it is essential that the 

environmental engineer understand the characteristics of each biological process to ensure 

that the proper environment is produced and controlled effectively. The overall objectives of 

the biological treatment of domestic wastewater are to: 

• Transform (i.e., oxidize) dissolved and particulate biodegradable constituents into 

acceptable end-products. 

• Capture and incorporate suspended and nonsettleable colloidal solids into a biological 

floc or biofilm. 

• Transform or remove nutrients, such as nitrogen and phosphorus. 

• More recently, to remove specific trace constituents and compounds. 

For industrial wastewater, the objective is to remove or reduce the concentration of organic 

and inorganic compounds. Because some of the constituents and compounds found in 

industrial wastewater are toxic to microorganisms, pretreatment may be required before 

industrial wastewater can be discharged to a municipal collection system. For agricultural 

irrigation runoff, the objective is to remove nutrients (specifically nitrogen and phosphorus), 

pesticides, and trace constituents that are capable of affecting the aquatic environment. 

The principal biological processes used for wastewater treatment can be divided into three 

main categories: suspended growth, attached growth (or biofilm), and combined suspended and 

attached growth processes. The successful design and operation of the biological processes 

requires an understanding of the: 

• Types of microorganisms involved. 

• Specific reactions that they perform. 

• Environmental factors that affect their performance. 

• Nutritional needs of microorganisms. 

• Microorganism reaction kinetics. 

These subjects are reviewed in light of process developments that have occurred over the past 

century. 


George Tchobanoglous, Ph.D., P.E. 

Professor Emeritus of Civil and Environmental Engineering 

University of California, Davis 

662 Diego Place 

Davis, CA 95616 USA 

Phone: (530) 756-5747 • Email: gtchobanoglous@ucdavis.edu 



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4 

For over 35 years, wastewater expert GEORGE TCHOBANOGLOUS, PH.D., P.E., 

has taught courses on water and wastewater treatment and solid waste management 

at the University of California, Davis, where he is Professor Emeritus in the Department 

of Civil and Environmental Engineering. He has authored or coauthored over 

350 publications, including 13 textbooks and five engineering reference books. 

Tchobanoglous has been past President of the Association of Environmental 

Engineering and Science Professors and currently serves as a national and international 

consultant to both government agencies and private concerns. Among his 

honors, he received the Athalie Richardson Irvine Clarke Prize from the National Water Research 

Institute in 2003 and was inducted to the National Academy of Engineers in 2004. In 2005, he 

received an Honorary Doctor of Engineering degree from the Colorado School of Mines. 

Tchobanoglous received a B.S. in Civil Engineering from the University of the Pacific, an M.S. in 

Sanitary Engineering from the University of California, Berkeley, and a Ph.D. in Environmental 

Engineering from Stanford University.


Membrane Bioreactor Process Fundamentals 

SIMON J. JUDD, PH.D. 

Cranfield University 

Bedfordshire, United Kingdom 

Introduction 

The use of microfiltration (MF) or ultrafiltration (UF) membranes in biological wastewater 

treatment has been well documented and extensively reviewed. Membrane filtration 

produces a high-quality, clarified, and disinfected permeate product. It also permits absolute 

control of solids retention time (SRT) and, thus, correspondingly, control of the mixed liquor 

suspended solids (MLSS) concentration. This both reduces the required reactor size and 

promotes the development of specific nitrifying bacteria, thereby enhancing ammonia removal, 

as well as producing less sludge. 

However, as with almost all other membrane processes, the production rate of membrane 

bioreactors (MBRs) is ultimately limited by membrane fouling. Fouling arises from the 

accumulation of solute, colloidal, and particulate species on or within the membrane, leading 

to a deterioration in membrane permeability. This phenomenon has led to the development 

of the low-fouling submerged configuration, first introduced 15 years ago, as opposed to 

sidestream systems, wherein the membrane is immersed in the bioreactor rather than fitted 

external to it (Figure 1). Submerged systems tend to allow greater hydraulic efficiencies, 

reflected in greater permeabilities, due to their operation at substantially lower fluxes than 

sidestream systems (Table 1), since fouling tends to increase with increasing flux. 

Out 

(membrane fouling) 

Feed 

(Screens) 

Bioreactor 

(Activity + Nature) 

Air 

(Energy) 

Sludge Waste 

(Quantity and Quality) 

Figure 1. 

Elements of a membrane bioreactor. 


Simon J. Judd, Ph.D. 

Professor in Membrane Technology and Director of Water Sciences 

Building 61 


Bedfordshire MK43 0AL United Kingdom 

Phone: (+44) (0)1234 754173 • Email: s.j.judd@cranfield.ac.uk 



5

Table 1. Summary of Membrane Bioreactor Process Conditions for Sewage Treatment 

Mitsubushi 

Orelis or 

Parameter Kubota Rayon Zenon Wehrle 

Membrane Geometry FS HF HF MT 

Process Configuration Submerged Submerged Submerged Side-stream 

Mean Air Velocity (m/s) 0.05 0.03 0.1 – 

Mean Liquid Velocity (m/s) 0.5* – – 1-3 

TMP (bar) 0.05-0.15 0.1-0.5 0.1-0.5 2-5 

Flux (LMH) ~25 ~15 ~25 70-100 

FS = Flat sheet. HF = Hollow fiber. MT = Multitube. LMH = Liters per cubic meter per hour. 

TMP= Transmembrane pressure. m/s = Meters per second. *As quoted by supplier. 

Fouling 

Fouling is a particularly acute problem in the case of MBRs, since the membrane is challenged 

with highly contaminated liquors having total solids concentrations of 20 grams per liter (g/L) or 

more arising from concentrated biomass. A second limitation, clogging – which refers to the 

filling of the membrane interstices with solids – is generally of less significance, but must still 

be suppressed for successful operation. There are a number of elements of a submerged MBR 

system (see Figure 1), all contributing to varying degrees of fouling and clogging, and their 

interrelationship is complex (Figure 2). 

In considering fouling and its causes and implications, the various elements of the system 

(see Figure 1) can be discussed in turn. Firstly, there are the feed characteristics. Various 

biochemical transformations in the bioreactor convert the organic matter in the feed into largely 

EPS 

• Free 

• Bound 

Feed Characteristics 

Biomass Characteristics 

Floc Characteristics 

• Size 

• Structure 

Bulk Characteristics 

• Viscosity/Rheology 

• Hydrophobicity 

Operation 

Retention Time 

• Hydraulic 

• Solids 

Hydraulics 

• Flux 

• TMP 

Reversible 

Fouling 

Irreversible 

Clogging 

Membrane 

Channels 

Aerator 

Ports 

Cleaning 

• Physical 

• Chemical 

Membrane Module Characteristics 

Pore 

• Size 

• Shape 

Surface Characteristics 

• Porosity 

• Charge/Hydrophobicity 

Configuration 

• Geometry 

• Dimensions 

Aeration 

• Design (Port Size) 

• Mean Flow Rate 

• Pulse Rate 

Figure 2. Inter-relationships between membrane bioreactor parameters and fouling. 

6

mineralized products, principally carbon dioxide and nitrate. In doing so, a variety of materials 

are released from the biomass in the reactor, which are collectively referred to as extracellular 

polymeric substances (EPS) and which contain a number of components that can foul the 

membrane to various extents. The relative and overall concentrations of the various components 

are determined both by feed characteristics and operational facets of the system and, in 

particular, by microbial speciation. Other foulants originate directly from unbiodegraded 

components of the feedwater, particularly for feeds of low biodegrability. 

Secondly, there is the actual process design and configuration of the MBR process, which in 

turn affects the key operator parameter values chosen. Submerged MBRs operate at lower 

fluxes and, as a result, lower transmembrane pressure (TMP) values (and so permeabilities) 

than the sidestream configuration. Therefore, they are inherently higher in energy efficiency, 

manifested as the specific energy demand in kilowatt-hour per cubic meter (kWh/m 3 ) 

permeate product. The configuration of the membrane module — principally, the membrane 

element geometry (planar or cylindrical), material physical properties (pore size, tortuosity, 

hydrophobicity, and surface porosity), and chemistry (polymeric or ceramic) — can also 

influence fouling. Although there are now a number of proprietary MBR technologies in the 

marketplace, the majority of them are based either on a flat sheet (FS) membrane 

configuration or on hollow fibers (HF). 

Thirdly, the operation of the MBR can profoundly impact fouling. There are two components 

of MBR operation: the membrane and the bioreactor. The bioreactor component (as with a 

conventional activated sludge process) is controlled by the relative values of the retention of 

solids and liquid (i.e., the solids [SRT] and hydraulic [HRT] retention times). Increasing the 

SRT and decreasing the HRT leads to higher levels of suspended solids (usually referred to as 

mixed liquor suspended solids [MLSS]) in the bioreactor, which increases the risk of clogging 

in both the membrane interstices and aerator ports. However, the impact of retention times 

on fouling is normally not significant in sewage treatment provided the MLSS is kept within a 

range of values in which fouling and foaming are suppressed (which tends to prevail at low 

MLSS values of around 4 to 6 g/L) and clogging is avoided by operating below a threshold 

MLSS value (which depends largely upon the membrane configuration). The main 

determinants for fouling control, however, relate directly to the membrane itself. 

Fouling Control 

In submerged MBRs, generally only three strategies are available for limiting fouling with 

regards to operation: reducing the flux, increasing aeration, or employing physical or chemical 

cleaning. Coarse bubble aeration produces scouring action at the surface of the membrane, 

which limits the build-up of foulant material. Lowering the flux reduces the rate at which 

foulants arrive at the membrane. However, both these modifications have cost implications, 

since a reduced flux implies a greater membrane area requirement and energy demand 

increases roughly linearly with increasing air flow rate. Cleaning demands downtime, and 

more rigorous cleaning using chemicals exerts chemical demand and produces chemical waste. 

A good operation of submerged MBR systems is based on obtaining the appropriate balance 

between operational flux, aeration, and cleaning. It follows that good MBR design is associated 

with maximizing the impact of aeration (in terms of reducing fouling) and facilitating 

cleaning with minimal downtime and chemicals consumption, as well as providing a high 

membrane area at low cost so as to permit a low flux. 

The constraints imposed by the challenging environment in which the membranes operate 

have meant that the municipal wastewater treatment MBR market is dominated by just two 



7

designs: the HF membrane-based product (Zenon) and the FS (Kubota). Much debate exists 

as to the relative merits offered by these two designs. The flat plate configuration tends to run 

at slightly higher permeabilities (flux per unit TMP) and is simpler in operation. On the other 

hand, unlike the HF, it cannot be backflushed. Both systems appear to maintain reasonable 

fluxes by applying relaxation – intermittent physical cleaning attained simply by closing the 

permeate valve and allowing air to scour the membrane surface. Both Kubota and Zenon have 

also recently developed design modifications for increasing efficiency. In the case of Kubota, 

this is achieved by stacking the membrane modules (already employed by Mitsubishi Rayon in 

its MBRs based on its Sterapore HF membrane). Zenon has introduced intermittent aeration, 

which effectively halves the specific energy demand associated with aeration, the main 

operating cost component. 

Technologies 

There are an increasing number of commercial MBR technologies, many of which are listed in 

Tables 2 and 3. It appears that almost all immersed MBRs are either rectangular FS or HF, 

and that most sidestream MBR technologies are multi-tubes (MT). The exceptions to these 

general observations appear to be: 

a. The Orelis Pleaide FS membrane used for sidestream treatment. 

b. The Polymem and Ultraflo sidestream HF systems. 

c. The hexagonal/octagonal rotating immersed Huber FS membrane. 

d) The Millenniumpore MT membrane, which has been used as an immersed module, 

as well as for air-lift sidestream. 

Table 2. Commercial Technologies 

Process Configuration 

Immersed 

Sidestream 

FS Colloide Novasep-Orelis 

Brightwater 

Huber* 

ITRI NWF 

Kubota 

Microdyn Nadir 

Toray 


Configuration 

HF Asahi-kasie Polymem 

Han-S Environmental 

Ultraflo 

ITT 

Koch/Puron 

Kolon 

Mitsubishi Rayon 

Motimo 

Siemens/USF-Memcor 

Zenon 

MT Millenniumpore Berghof** 

Millenniumpore 

Norit-Xflow** 

*Rotating membrane. 

**MT membrane products used by process suppliers such as Aquabio, Dynatec, Triqua, and Wehrle. 

8

Table 3. Commercial Membrane Product Specifications 

Membrane Pore Specific Propietary Name, 

Supplier (Configuration, Size Surface Membrane, 

Material) (µm) Area (m -1 ) or Module 

Berghof MT, PES 0.08 110 HyPerm-AE 

or PVDF 0.12 Hyperflux 

Brightwater FS, PES 0.08 110 Membright 

Toray FS, PVDF 0.08 130 Toray 

Kubota FS, PE 0.4 150 Kubota 

Colloide FS, PES 0.04 160 Sub Snake 

Huber FS, PES 0.038 160 VRM 

Millenniumpore MT, PES 0.1 180 Millenniumpore 

Koch HF, PES 0.05 260 Puron 

Zenon HF, PVDF 0.04 300 ZW500C-D 

Norit-Stork MT, PVDF 0.038 320 F4385 

290 F5385 

Mitsubishi Rayon HF, PE 0.4 425 SUR 

HF, PVDF 0.4 333 SADF 

USF-Memcor HF, PVDF 0.04 600-700 B10R, B30R 

Asahi-kasie HF, PVDF 0.1 710 Microza 

Polymem HF, PS 0.08 800 WW120 

Motimo HF, PVDF 0.1-0.2 1100 Flat Plat 

Moreover, almost all HF MBR membrane products currently on the market are verticallymounted 

and polyvinylidene difluoride (PVDF)-based, the exceptions being the Koch-Puron 

membrane (which is polyethersulphone [PES]), the Polymem polysulfone (PS) membrane, 

and the Mitsubishi Rayon SUR module (which is polyethylene [PE] material and also 

horizontally oriented). All HF products are in the coarse UF/tight MF region of selectivity, 

having pore sizes predominantly between 0.03 and 0.4 micrometers (µm), and all such 

vertically-mounted systems are between 0.7 and 2.5 millimeters (mm) in external diameter. 

Distinctions in HF MBR systems can be found mainly in the use of membrane reinforcement 

(essential for those HF elements designed to provide significant lateral movement) and, 

perhaps most crucially, the air-to-membrane contact. 



9

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PROFESSOR SIMON JUDD is the Director of Water Sciences at Cranfield 

University. He has been on the staff at the School of Water Sciences since August 

1992, and occupies the Chair in Membrane Technology. Judd has managed almost 

all biomass separation membrane bioreactor (MBR) programs conducted within the 

School and has been Principal or Co-Investigator on three major UK research 

council-sponsored programs dedicated to MBRs with respect to in-building water 

recycling, sewage treatment, and contaminated groundwater/landfill leachate. He 

also serves as Chairman of the Project Steering Committee of the multi-centered 

EU-sponsored EUROMBRA project. In addition to publishing extensively in the research literature, 

Judd has co-authored two textbooks in membrane and MBR technology, with a third one due out in July 

2006. Judd received a B.Sc. in Chemistry from the University of Bath, M.Sc. in Electrochemical 

Science from Southampton University, and a Ph.D. in Filtration Science from Cranfield University.


Commercially Available 

Membrane Bioreactor Systems 

JAMES F. DECAROLIS 

MWH 

San Diego, California 

ZAKIR HIRANI 

MWH 


SAMER S. ADHAM, PH.D. 

MWH 


NEIL TRAN, P.E. 

City of San Diego 


STEVE LAGOS 

City of San Diego 


Introduction 

The following paper provides a detailed description of four commercially available 

membrane bioreactor (MBR) systems currently established in the municipal wastewater 

treatment/water reclamation market in the United States. These systems are supplied by 

Zenon Environmental, Inc., USFilter, Ionics/Mitsubishi Rayon Corporation, and Enviroquip, Inc./ 

Kubota Corporation. Each of these suppliers has full-scale MBRs currently operating in the 

United States, and their systems are approved by the California Department of Health 

Services (CDHS) to meet Title 22 water recycling criteria. Details of each system are based 

on knowledge gained during hands-on pilot testing performed by the project team along with 

information provided by the manufacturers. The paper will also describe four newly developed 

MBR systems currently entering the United States market. These suppliers include Koch 

Membrane Systems (KMS), Kruger, Parkson Corporation, and Huber, Inc. The project team 

is currently evaluating the ability of these new technologies to meet Title 22 recycling criteria 

under grant funding provided by the United States Department of Interior, Bureau of 


James F. DeCarolis 

MWH Americas, Inc. 

Aqua 2030 Research Center 

North City Water Reclamation Plant 

4949 Eastgate Mall 

San Diego, CA 92121 USA 

Phone: (858) 824-6067 • Email: jdecarolis@sandiego.gov 



11

Reclamation. Lastly, the paper discusses MBR pilot-testing considerations based on nearly a 

decade of MBR research performed by the project team at the Aqua 2030 Research Center 

located in San Diego, California. 

Commercially Available Membrane Bioreactor Systems 

(Established in the United States) 

Zenon Membrane Bioreactor System 

The Zenon MBR system uses polyvinylidene fluoride (PVDF) ultrafiltration (UF) reinforced 

hollow fiber membranes (nominal pore size = 0.04 micron [µm]). Individual membrane 

elements are configured into membrane cassettes that are typically submerged directly into a 

designated membrane tank in direct contact with mixed liquor suspended solids (MLSS). The 

commercial designation of the membrane module currently used in the Zenon MBR system is 

ZW 500d, which has superseded previous generation modules offered by Zenon, including the 

ZW 500a and ZW 500c. Benefits of the 

ZW 500d configuration over its predecessors 

include a higher membrane packing density 

and lower air scouring requirements (Benedek 

and Cote, 2003). A photograph of a ZW 500d 

cassette is provided in Figure 1. Each cassette 

used in full-scale applications is typically 

designed to contain up to 48 individual 

membrane elements. Coarse bubble air is 

introduced from the bottom of the cassette to 

scour the surface of the membranes. This 

prevents solids from accumulating on the 

membrane surface, which could result in 

increased transmembrane pressure (TMP). A 

unique feature of the Zenon MBR system is 

the intermittent application of membrane air 

scour, which reduces energy consumption 

Figure 1. Photograph of Zenon 500d membrane 

cassette (Zenon, 2005). 

USFilter Membrane Bioreactor System 

The USFilter MBR system utilizes microfiltration (MF) hollow fiber PVDF membranes 

(nominal pore size of 0.08 µm) that are submerged in a separate membrane tank. The 

commercial designation of the original membranes used in USFilter’s MBR systems is B10R. 

Though still used in MBR package plants (

A unique feature of the USFilter MBR system is that it incorporates MemJet technology, 

which includes the injection of both air and mixed liquor at the bottom of the membrane 

modules. This operation causes the membranes to be scoured and fluidized and prevents 

particulate matter from accumulating on the membrane surface. 

Ionics/Mitsubishi Rayon Membrane Bioreactor System 

The Ionics/Mitsubishi Rayon MBR system uses 

polyethylene MF hollow fiber membranes (nominal 

pore size of 0.4 µm) that are submerged directly 

in an aeration basin. The commercial designation 

for the membranes is Sterapore HF. Though 

classified as MF, the membranes are characterized 

with a tight pore size distribution (absolute pore 

size= 0.5 µm). As shown in Figure 3, each 

membrane cassette contains individual hollow 

fibers membranes configured horizontally to make 

up an element. Each membrane cassette contains 

50 of the 1-square meter (m 2 ) Mitsubishi 

Sterapore HF MF membranes, for a total 

membrane area of 100 m 2 (1,076 ft 2 ). Air is 

supplied at the bottom of the tank for scour and Figure 3. Mitsubishi Sterapore HF membrane 

cassette. 

biological process. During filtration, vacuum 

pressure is applied, causing water to permeate through the membrane from the top and bottom. 

Kubota Membrane Bioreactor System 

The Kubota MBR system contains flat sheet, chlorinated polyethylene MF membranes (nominal 

pore = 0.4 µm) that are submerged directly in an aeration basin. The commercial designation 

of the flat sheet membrane cartridge is Type 510. Each cartridge is 1 m (H) x 0.49 m (W) x 

6 millimeters (mm) thick, and contains a membrane surface area of 0.8 m 2 . A photograph of 

the Type 510 membrane cartridge is provided in 

Figure 4. Each cartridge contains a support 

plate, spacer, permeate nozzle, and membrane 

layer on each side. Recently (2005), Kubota 

introduced a Type 515 membrane cartridge 

primarily for applications of 2 mgd or greater. 

The Type 515 cartridges are larger in dimension 

than Type 510 cartridges, resulting in increased 

membrane area per cassette. The Type 510 

cassette contains up to 150 individual cartridges 

(spaced 7 mm apart) and is equipped with a 

permeate manifold. During filtration, permeate 

water flows out of the cartridges through the 

permeate nozzle and into collection tubes that 

Figure 4. Kubota Type 510 membrane cassette. 

feed into the permeate manifold. A unique 

feature of the Kubota MBR system is that can be designed as a single or double deck (DD) 

configuration. The DD systems contain both upper and lower membrane cassettes. The 

lower cassettes are equipped with a coarse air bubble diffuser and provide structural support 

to the upper casts. This DD configuration offers several benefits (van der Roest et al, 2002), 

including the reduction of 1) the membrane footprint, 2) the biological volume consumed by 



13

the membrane system, and 3) air consumption used for membrane cleaning. The DD also 

yields a more controllable biological process and reduces the possibility of short circuiting. 

Newly Developed Membrane Bioreactor Systems 

Koch Membrane Systems Membrane Bioreactor System 

The KMS membrane bioreactor uses PURON ® hollow fiber UF membranes (nominal pore 

size = 0.05 µm) that are made of polyethersulfone (PES) and casted onto a braided support. 

The hollow fiber membranes are configured in bundles to form membrane modules and are 

submerged in a designated membrane tank. A unique feature of the KMS MBR is that each 

membrane is sealed at the top and potted only at the lower end. This design allows the nonpotted 

ends to move freely in the MLSS, which eliminates the possibility of clogging. An air 

nozzle is located in the center of each bundle to provide membrane air scour. A standard 

module contains nine membrane bundles for a total membrane area of 30 m 2 . The PURON 

hollow fiber module is shown in Figure 5. 

Figure 5. PURON membrane module (Koch Membrane Systems, 2005). 

Huber Membrane Bioreactor System 

The Huber MBR system uses flat sheet UF membranes (nominal pore size= 0.038 µm) 

submerged in a designated membrane tank. A unique feature of the Huber MBR system is 

that the membranes are supported on a Vacuum Rotation Membrane (VRM ® ) unit, which 

consists of individual rotating VRM plate membranes installed around a stationary hollow 

shaft. Two centrally arranged air tubes 

introduce scouring air into the interspaces 

between the plates. Permeate 

is drawn from the each plate via 

permeate tubes that collect permeate 

to a common pipe. These horizontal 

pipes meet at a center manifold, from 

which the permeate exits the system. 

The constant rotation (1.8 revolutions 

per minute [RPM]) of the VRM unit 

allows the membrane plates to be air 

scoured alternatively by just two 

centrally placed air tubes, thereby Figure 6. Huber VRM unit (plan view). 

14

educing the scouring air requirements. Energy efficiency is maintained by using only a 

2−horsepower motor for the rotation of the VRM. 

The VRM membranes are configured in plates (3-m 2 filter surface area per plate) that contain 

permeate channels, spacers, and permeate discharge nozzles. A VRM module is comprised of 

four such plates; modules (when arranged circularly) form a membrane element. Huber MBR 

membrane elements are offered in two sizes: VRM 20 (containing six modules) and VRM 30 

(containing eight modules). Standard VRM 20 systems are designed with a minimum of 10 

and maximum of 50 elements, while standard VRM 30 systems are designed with a minimum 

of 20 and maximum of 60 elements. A photograph of a VRM 20 unit mounted on the VRM 

drive is provided in Figure 6. 

Kruger Membrane Bioreactor System 

Kruger MBR system uses flat-sheet PVDF UF 

membranes (nominal pore size of 0.08 µm) 

submerged in a designated membrane tank. 

Membranes are supported on a polyolefin nonwoven 

material and Acrylonitrile Butadiene 

Styrene (ABS) plate. Each module contains 

100 flat-sheet membrane elements, with a total 

membrane area of 1,500 ft 2 . A photograph of the 

flat sheet module is provided in Figure 7. A 

unique feature of the Kruger MBR system is that 

the membrane is characterized with a tight pore 

size distribution (0.03 µm), allowing the fluid to 

Figure 7. Flat sheet module (Kruger, 2005). 

be equally distributed along the membrane surface 

during filtration (Kruger, 2005). It also allows the cleaning chemicals to be evenly distributed 

during maintenance cleaning, making cleaning more effective. 

Parkson Dynalift Membrane Bioreactor System 

The Parkson Dynalift MBR contains X-Flow ® PVDF tubular 

UF membranes with a nominal pore size of 0.03 µm. A unique 

feature of the Parkson MBR system is that the membranes are 

configured in modules and are external to the biological process. 

These tubular membranes provide a wide-channel, non-clogging 

design and, according to the manufacturer, can be operated at 

high MLSS levels of up to 15,000 milligrams per liter (mg/L). 

To eliminate high pumping energies, membranes are placed in a 

vertical orientation and MLSS is kept suspended inside the 

module using air-lift assisted cross-flow pumping. A photograph 

of the X-Flow membranes is provided in Figure 8. 

Aqua 2030 Membrane Bioreactor Research Program 

Figure 8. Parkson Corporation’s 

X-Flow membrane 

(Parkson, 2005) 

For nearly a decade, MWH and the City of San Diego in California have been researching 

MBR technology and its application for water reuse at the Aqua 2030 Research Center. 

The majority of this research was made possible under funding provided by the United States 

Department of Interior, Bureau of Reclamation, and was conducted in multiple phases from 

1997 to the present. Phase I (Adham and Gagliardo, 1998) included an extensive literature 

search on MBR technology and identified major MBR suppliers in the field. In addition, the 



15

project team implemented a worldwide survey of full-scale MBR applications for domestic 

wastewater treatment and developed rough cost estimates for the technology. Information 

gathered during the survey included operational characteristics such as capacity, MLSS 

concentrations, food-to-microorganism ratio, permeate flux, solids retention time (SRT), and 

hydraulic retention time (HRT), along with performance in terms of particulate, organic, 

nutrient, and microbial contaminant removal. 

Phase II testing (Adham et al., 2000) included the operation and evaluation of two pilot-scale 

MBRs (Zenon and Mitsubishi) over a 1-year period. The purpose of testing was to evaluate 

the performance of these systems during the treatment of municipal wastewater and to 

establish baseline operating conditions. Towards the end of the pilot-testing period, the 

project team worked with CDHS to establish criteria for MBR systems to gain Title 22 

approval. Based on these criteria, further testing of the Zenon and Mitsubishi systems was 

done in 2001 under funding provided by the National Water Research Institute (Adham et al., 

2001a and 2001b). Results from this testing, along with those acquired during the 

1-year operating period, were submitted to CDHS in September 2001. Shortly after, the two 

systems were granted conditional approval to meet Title 22 water recycling criteria. 

In June 2002, the project team embarked on Phase III (Adham and DeCarolis, 2004), which 

included the evaluation of four MBR pilot units (USFilter Corporation/Jet Tech Products Group; 

Zenon Environmental, Inc.; Ionics/Mitsubishi Rayon Corporation; and Enviroquip Inc./ 

Kubota Corporation). Pilot testing of these systems was conducted over a 16-month period on 

raw and advanced primary effluent to evaluate MBR performance and to determine the 

suitability of MBR effluent as a feed to reverse osmosis units. Data generated during this 

study demonstrated the ability of the Kubota and USFilter MBR systems to meet Title 22 

Water Recycling Criteria, and both were granted approval in 2002/2003 (California 

Department of Health Services, 2005). In addition, it was shown that MBR systems could 

successfully operate on advanced primary treated wastewater containing coagulant and 

polymer residual. 

Recently, the project team has begun Phase IV (U.S. Department of Interior, Bureau of 

Reclamation, 2005) of the MBR program. The purpose of this ongoing project is to evaluate 

four newly developed MBR systems entering the municipal wastewater market in the United 

States. These include systems from Koch Membrane Systems (Wilmington, Massachusetts), 

Parkson Corporation (Fort Lauderdale, Florida), Huber Technology, Inc. (Huntersville, North 

Carolina), and Kruger (Cary, North Carolina). Each of these systems has been designed with 

innovative features aimed to optimize operational performance and efficiency. As part of 

testing, each system will be evaluated to meet Title 22 requirements, which (upon approval) 

would double the number of approved systems available to the water reclamation industry. 

Based on the research program described above, the project team has identified several 

important factors to consider when pilot testing MBR systems for water reuse applications. 

These include: 

• Water Quality Goals (total nitrogen, phosphorus, establish a water quality sampling plan). 

• Selecting a Supplier(s) (system configuration, customer support, suppliers experience, 

capacity of full-scale potential plant, pilot rental fee). 

• Pilot Site (access to raw wastewater [20- to 40 gallons per minute]), access to sewer to 

dispose of waste, potable water supply for cleaning, adequate power supply available). 

16

• MBR Operating Conditions (flux, HRT, SRT, membrane cleaning frequency [maintenance 

and recovery cleans], backwash/relax frequency, recirculation rate for denitrification). 

• Special Considerations (pretreatment, operator requirements, duration of testing, post 

treatment requirements, operation and maintenance requirements, biological tank mixing 

requirements, redundancy and location of feed pumps, wasting, foaming control). 

Additional information regarding these considerations will be provided during the conference 

presentation. 

References 

Adham, S., and P. Gagliardo (1998). Membrane Bioreactors for Water Repurification – Phase I. Desalination 

Research and Development Program Report No. 34, Project No. 1425-97-FC-81-30006J, United States 

Department of Interior, Bureau of Reclamation. 

Adham, S., R. Mirlo R. and P. Gagliardo (2000). Membrane Bioreactors for Water Reclamation – Phase II. 

Desalination Research and Development Program Report No. 60; Project No. 98-FC-81-0031, United 

States Department of Interior, Bureau of Reclamation. 

Adham, S., D. Askenaizer, R. Trussell, and P. Gagliardo (2001a). Assessing the Ability of the Zenon Zenogem 

Membrane Bioreactor to Meet Existing Water Reuse Criteria, Final Report. National Water Research 

Institute. 

Adham, S., D. Askenaizer, R. Trussell, P. and Gagliardo (2001b). Assessing the Ability of the Zenon Mitsubishi 

Sterapore Membrane Bioreactor to Meet Existing Water Reuse Criteria, Final Report. National Water 

Research Institute. 

Adham, S., and J. DeCarolis (2004). Optimization of Various MBR Systems for Water Reclamation – Phase III. 

Final Report Project No. 01-FC-81-0736, Bureau of Reclamation. 

Benedek, A., and P. Cote (2003). “Long-Term Experience with Hollow Fiber Membrane Bioreactors.” 

Proceedings, International Desalination Association Conference. 

California Department of Health Services (2005). Treatment Technology Report for Recycled Water. Department 

of Health Services, State of California Division of Drinking Water and Environmental Management. 

Koch Membrane Systems (2005). Technical literature on the KMS Membrane Bioreactor. 

Kruger (2005). Technical literature on the BIOSEP FS MBR Process. 

Parkson Corporation (2005). Website: http://www.parkson.com/Content.aspx?ntopicid=196. 

U.S. Department of Interior, Bureau of Reclamation (2005). Project agreement number 05 FC 81157, 

October. 

USFilter-Memcor (2005). Technical information and correspondence provided by Wenjun Liu, Director of 

Bioprocess Technology. 

van der Roest, H.F., D.P. Lawrence, and A.G.N. van Bentem, (2002) Membrane Bioreactors for Municipal 

Wastewater Treatment. IWA Publishing. STOWA. 

Zenon (2005). Website: http://www.zenon.com/mbr/design_considerations.shtml. 



17

18 

JAMES F. DECAROLIS is a Senior Engineer with the Applied Research Department 

of the consulting firm, MWH, where he has been involved with several low-pressure 

membrane pilot studies conducted at the Aqua 2030 Research Center located in San 

Diego, California. In 2002/2003, he served as an on-site Project Engineer for a United 

States Department of Interior, Bureau of Reclamation (USBR) study evaluating the 

feasibility of using membrane bioreactor technology for water reclamation. In tandem 

with this project, he served as Project Engineer for a Desalination Research Innovation 

Partnership project to assess the ability of membrane bioreactors to serve as 

pretreatment to reverse osmosis during the treatment of municipal wastewater. Recently, he served as an 

on-site Engineer for an advanced water treatment pilot study conducted at North City Water Reclamation 

Plant, which evaluated ultrafiltration followed by reverse osmosis followed by ultraviolet plus peroxide for 

indirect potable reuse. He is currently serving as Project Manager for a USBR project evaluating newly 

developed membrane bioreactor systems for water reuse. DeCarolis received both a B.S. and M.S. in 

Environmental Engineering from the University of Central Florida.


Evaluation of Conventional Activated Sludge 

Compared to Membrane Bioreactors 

R. SHANE TRUSSELL, PH.D., P.E. 



Introduction 

Amembrane bioreactor (MBR) is a biological wastewater treatment process that 

implements a low-pressure membrane — microfiltration (MF) or ultrafiltration (UF) — to 

provide solid-liquid separation. Due to its compact footprint and consistent high-quality 

effluent, MBRs have captured the attention of the international wastewater treatment 

community. Although MBRs are ideal for water reclamation projects, the high-quality effluent 

and additional pathogen removal make MBRs a promising technology for discharging highquality, 

partially disinfected wastewater into streams and water bodies while using little or no 

chemical addition for disinfection. The purpose of this presentation is to compare and 

evaluate the principle differences, advantages, and disadvantages of the MBR process 

compared to a conventional, gravity-settled activated sludge. 

Brief Perspective on Membrane Bioreactor Development 

Biological processes have become the preferred process for municipal wastewater treatment. 

The activated sludge process (ASP) was pioneered by Arden and Lockett, who reused the 

flocculent solids from the previous aeration cycle to accelerate treatment rates (Ardern and 

Lockett, 1914). They called the accumulation of these flocculent solids activated sludge and 

found that treatment efficiency increased with higher proportions of activated sludge. The 

ASP has continued to develop over the past nine decades, and wastewater treatment plants 

are being designed today with an excellent understanding of how to optimize plant 

performance for organic, solids, and (more frequently) nutrient removal. However, regardless 

of how sophisticated and automated the plant design is, the solid-liquid separation is still 

performed by gravity sedimentation, and this means that operations staff must understand 

what influences sludge settleability to maintain good effluent quality. 

Relatively new to biological wastewater treatment is the MBR process. The development of 

the MBR process began in the United States with the direct filtration of activated sludge 

through a cloth filter along with the concept of coupling a membrane with activated sludge by 

Dorr-Oliver in Stamford, Connecticut (Stiefel and Washington, 1966). Thetford Systems in 

Ann Arbor, Michigan, commercialized the MBR process in the early 1970s. This new MBR 

process combined the three separate unit operations required in a conventional activated 


R. Shane Trussell, Ph.D., P.E. 

Principal 


232 North Lake Avenue, Suite 300 

Pasadena, CA 91101 USA 

Phone: (626) 486-0560 • Email: shane.trussell@trusselltech.com 



19

sludge treatment train into one compact process (Figure 1). The original MBR was an external 

MBR (EMBR) where mixed liquor was pumped from an aeration basin to the membrane 

module for solid-liquid separation. Yamamoto et al. (1989) developed the submerged MBR 

(SMBR) configuration where the membrane module was immersed directly in the mixed 

liquor and operated under suction pressure. It is the SMBR configuration that is currently 

dominating the municipal wastewater market and is the focus of this presentation, while the 

EMBR configuration is principally implemented on high-strength industrial wastewaters. 

Activated Sludge Process 

Aeration Basin 

Secondary Clarifier 

Microfiltration 

or Ultrafiltration 

Tertiary Treated 

Wastewater 

Primary Treated 

Wastewater 

(Equivalent to a 

1–3 mm screen) 

SMBR Process 

Aeration Basin 

Backwash Water 

WASTE 

Tertiary Treated 

Wastewater 

WASTE 

Figure 1. Flow schemes for activated sludge and SMBR processes. 

Submerged Membrane Bioreactors Versus the Activated Sludge Process 

Process Design: The SMBR process uses activated sludge technology, combining it with membrane 

filtration, to expand the normal operating region. The SMBR process is not affected by the 

limitations associated with gravity sedimentation for solid-liquid separation, and this allows 

operation at much higher mixed liquor suspended solids (MLSS) concentrations. The peak 

MLSS concentration at which the SMBR process is not sustainable due to rapid membrane 

fouling is complex and is an area of ongoing research. However, today’s SMBR plants are 

optimally designed for MLSS concentrations between 8 and 12 grams per liter (g/L) 

(Trussell et al., 2005a; Trussell et al., 2005b). 

Higher MLSS concentrations translate into a longer solids retention time (SRT) for a given 

hydraulic retention time (HRT). This means that for the same aeration basin volume needed 

for the ASP, the SMBR process could double the design SRT. Longer SRTs provide a more 

stable biological process that results in wastewater effluent with low oxygen demand. 

Traditionally, SMBRs have been designed to operate at SRTs greater than 20 days (d), and 

some small facilities only waste once or twice per year. These longer SRTs ensure that 

adequate organics removal and complete nitrification can occur even in cold climates. Longer 

SRTs also bring about the possibility that specialized microorganisms could propagate and 

remove organics that are difficult and slow to degrade. Most importantly, longer SRTs reduce 

biological sludge production, reducing the mass of solids that needs to be disposed. 

20

Alternatively, higher MLSS concentrations can translate into reduced aeration basin volume. 

This means that for the same SRT as the ASP, the SMBR process could reduce aeration basin 

volume significantly, reducing HRT by close to one-half. However, this concept brings to light 

one of the principle disadvantages of the SMBR process compared to ASP: the SMBR process 

has a minimum SRT, where organics present in the mixed liquor have not been adequately 

stabilized, and these organics result in rapid membrane fouling (Trussell et al., 2005a; 

Trussell et al., 2004). Some manufacturers have set a minimum SRT at 12 d, while others are 

willing to work with design engineers to design at reduced SRTs (as low as 8 d). A common 

design for the minimum SRT is to determine where nitrification fails at the wastewater 

temperature and then apply a safety factor to ensure nitrification does not fail. The ASP is not 

restricted by the interaction of the membrane with the mixed liquor, and many wastewater 

treatment plants with ASP operate with low SRTs to inhibit nitrification. Operation at these 

low SRTs in SMBRs results in rapid membrane fouling, and SMBR manufacturers do not 

recommend plant designs at these low SRTs. 

Effluent Water Quality: The principle difference in effluent water quality between an SMBR 

and an ASP is the solid-liquid separation mechanism. Both SMBR and ASP depend principally 

on the biological process to oxidize influent organics and nitrogen. However, SMBR uses a 

membrane for solid-liquid separation to obtain a higher quality effluent. A well-operated ASP 

will contain suspended solids ≤ 10 milligrams per liter (mg/L), turbidity ≤ 10 nephelometric 

turbidity units (NTU), and 5-day biological oxygen demand (BOD 5 ) ≤ 10 mg/L, while the SMBR 

process typically contains suspended solids ≤ 2 mg/L (non-detect), turbidity ≤ 0.2 NTU, and 

BOD 5 ≤ 2 mg/L (non-detect) (Trussell et al., 2000). The SMBR is retaining all suspended 

solids in the reactor and, even though the degree of biological soluble organics removal is solely 

a function of the SRT, the SMBR process is removing additional soluble organics because of 

the direct filtration of activated sludge. Any organics larger than the membrane pores are 

being retained in the reactor, and organics even smaller than the membrane pores are being 

retained due to additional filtration provided by the cake layer that develops in these high 

solids environments. The SMBR process uses membrane separations to improve the biological 

process and produce an effluent that exceeds the effluent quality produced in ASP. 

Peak Flows: The principle advantage of the SMBR process — the membrane — is also its 

principle weakness when it comes to addressing peak flows. Although highly dependent on 

the specifics of the design (i.e., temperature, design flux, etc.), the SMBR process is typically 

limited to a peaking factor of 1.5 Q (flow rate), while the ASP is capable of sustaining much 

larger peak flows (>2.5 Q) for a longer period of time. This is because all of the peak flow 

must be filtered through the membranes to exit the facility in the SMBR, but the peak flow 

passes effortlessly over a weir in the ASP. The SMBR process is most economical when 

designed to operate at a constant flow rate, and large peak flows are best addressed with flow 

equalization in most facilities. As future membrane costs continue to decrease, the issue of 

peak flows in SMBRs will become less important because design engineers will be able to 

ensure that adequate membrane area is installed to sustain membrane performance during 

peak flow events. 

Mixed Liquor Properties: The mixed liquor properties are important because they affect how 

easily sludge can be filtered through membranes, settled, or dewatered. There is a significant 

difference in selective pressures between the ASP and SMBR, and one would expect 

significant differences in mixed liquor properties as well. While the ASP requires biology that 

flocculates and settles well to remain in the system, the SMBR process retains all biomass, 

even single cells, in the mixed liquor. 



21

Although research is still needed to completely understand the differences and what 

influences these mixed liquor properties between the ASP and SMBR, Merlo et al. (2004) has 

revealed some key findings that highlight the differences in mixed liquor properties: 

1. SMBR sludge has a higher colloidal material content than ASP sludge. 

2. SMBR sludge has higher filament concentrations than ASP sludge. 

3. SMBR sludge particle size distribution (excluding colloidal) was controlled 

exclusively by the mixing intensity, G, and the same particle size distribution for an 

ASP was obtained for the SMBR. 

Merlo et al. (2004) provides explanations for these observed differences between SMBR and 

ASP mixed liquor properties: 

1. The SMBR mixed liquor has higher colloidal content because the membrane is 

retaining materials that would normally exit the ASP over the effluent weir. 

2. The SMBR mixed liquor has higher filament concentrations because the SMBR 

process is the perfect “trapping” environment. Unless designed with a surface 

wasting system, the SMBR process will retain all floating material, including 

filamentous microorganisms that float and may cause foam. 

3. A similar particle size distribution was obtained for an activated sludge reactor at high 

shear conditions (ASP) as that obtained for the SMBR (Figure 2). 

0.6 

0.5 

ASP 

Frequency 

0.4 

0.3 

0.2 

0.1 

0.0 

0.6 

0.5 

2-4 4-6 6-8 8-10 10-20 20-40 40-100 100-200 

SMBR 

Frequency 

0.4 

0.3 

0.2 

0.1 

0.0 

2-4 4-6 6-8 8-10 10-20 20-40 40-100 100-200 

Characteristic Length, micron 

Figure 2. Particle size distribution for ASP and SMBR at 5-d mean cell residence time 

(Adapted from Merlo et al., 2004). 

22

Still Need to Flocculate: A key conclusion of the SMBR process is that despite all of its 

differences from the ASP and the membrane providing an absolute barrier, the mixed liquor 

properties still play a significant role in the successful application of the process. A mixed 

liquor that is well flocculated and contains a lower concentration of colloidal material is 

inherently easier to filter and has a lower fouling potential than a dispersed sludge with high 

concentrations of colloidal material (Fan et al., 2006). Recently, this topic has become the 

focus of the two leading SMBR manufacturers in the United States market. One gave a 

recent workshop in 2005 on “Biohydraulics” while another presented a plot of colloidal 

material versus time to filter and indicated the preferred region for good sludge filterability. 

As SMBR technology advances, engineers will need to understand mixed liquor properties and 

biological characteristics to design an optimized SMBR for a specific application. 

Conclusions 

Relatively new to the wastewater treatment industry, SMBRs offer significant advantages 

compared to conventional ASP: a more compact reactor, higher effluent quality, and higher 

MLSS concentrations. However, there are currently significant disadvantages of the SMBR 

process that design engineers need to be informed about: high MLSS limit, low SRT limit, 

and peak flow issues. Finally, although the SMBR process retains everything larger than the 

membrane pores, the mixed liquor properties are still important to minimize fouling and 

ensure successful plant operation. We need to change from the concept of sludge settleability 

to sludge filterability. 

References 

Ardern, E., and W.T. Lockett (1914). “Experiments on the oxidation of sewage without the aid of filters.” 

J. Soc. Chem. Indtr., (33): 523. 

Fan, F., Z. Hongde, and H. Husain (2006). “Identification of wastewater sludge characteristics to predict 

critical flux for membrane bioreactor processes.” Water Res., (40): 205. 

Merlo, R., R.S. Trussell, S.H. Hermanowicz, and D. Jenkins (2004). “Physical, chemical and biological 

properties of submerged membrane bioreactor and conventional activated sludges.” WEFTEC, 

New Orleans, LA. 

Stiefel, R.C., and D.R. Washington (1966). “Aeration of concentrated activated sludge.” Biotechnol. Bioeng., 

(8): 379. 

Trussell, R.S., S. Adham, P. Gagliardo, R. Merlo, and R.R. Trussell (2000). “WERF: Application of membrane 

bioreactor (MBR) technology for wastewater treatment.” WEFTEC, Anaheim, CA. 

Trussell, R.S., S. Adham, and R.R. Trussell (2005a). “Process limits of municipal wastewater treatment with 

the submerged membrane bioreactor.” J. Environ. Eng.-ASCE, 131: 410. 

Trussell, R.S., R. Merlo, S.H. Hermanowicz, and D. Jenkins (2005b). “The effect of high mixed liquor 

suspended solids concentration, mixed liquor properties, and coarse bubble aeration flow rate on membrane 

permeability.” WEFTEC, Washington D.C. 

Trussell, R.S., R.P. Merlo, S. Hermanowicz, and D. Jenkins (2004). “The effect of organic loading on 

membrane fouling in a submerged membrane bioreactor treating municipal wastewater.” WEFTEC, 

New Orleans, LA. 

Yamamoto, K., M. Hiasa, T. Mahmood, and T. Matsuo (1989). “Direct solid-liquid separation using hollow fiber 

membrane in an activated-sludge aeration tank.” Water Sci. Technol., 21: 43. 



23

24 

R. SHANE TRUSSELL, Ph.D., P.E., is a Principal at Trussell Technologies, Inc., an 

environmental engineering firm that focuses on the quality and treatment of water 

and wastewater. He has 8 years of hands-on experience with processes for advanced 

wastewater treatment, particularly membrane filtration of secondary and tertiary 

effluents, membrane bioreactors, reverse osmosis, electrodialysis, ion exchange, 

granular activated carbon adsorption, and disinfection with ozone, chlorine, and 

chloramines. Where membrane bioreactors are concerned, he is a recognized 

authority, and he was the first to demonstrate that membrane fouling due to high 

solids concentrations and high food-to-microorganism ratios (low mean cell residence times) are fundamentally 

different in their nature. Trussel received a B.S. in Chemical Engineering from the University 

of California, Riverside, an M.S. in Environmental Engineering from the University of California, Los 

Angeles, and a Ph.D. in Environmental Engineering from the University of California, Berkeley.


Membrane Bioreactor Global Knowledgebase 

GLEN T. DAIGGER, PH.D., P.E., BCEE, NAE 

CH2M HILL 

Englewood, Colorado 

Introduction 

In 2001, the Water Environment Research Foundation (WERF) authorized a project to 

assemble a global knowledgebase summarizing the applications and performance of membrane 

bioreactors (MBRs) (Daigger et al., 2001). Available on the WERF website to WERF 

subscribers or for purchase as a CD-ROM, the knowledgebase contains eight elements, 

including: 

1. Tutorials (PowerPoint-based) to provide an introduction and overview to parties 

potentially interested in MBRs for a particular application. 

2. Published Literature Database Search Tool, which is an extensive searchable database 

consisting of abstracts from relevant technical papers. 

3. Gray Literature Database Search Tool, which is an extensive searchable database 

providing listing and source information for relevant gray literature (pilot-plant reports, 

manufacturer’s information, etc). 

4. Installation Database Search Tool, which is a searchable database providing summary 

information for a wide range of MBR installations and more detailed information for 

selected examples of various types of installations. 

5. Decision Tool, which provides a set of questions and answers to help the website user 

determine whether MBRs are potentially applicable for a specific application (should 

they be interested in learning more!). 

6. Preliminary Sizing Tool, which is used to develop preliminary sizes for a particular 

application (used in conjunction with the Decision Tool). 

7. Installations Survey Tool, which allows owners of MBR installations to input data on their 

application to share with others. 

8. Links to Related Websites, which allow access to information on MBRs contained in 

other websites. 

The searchable database format was selected due to the rapid development of this technology 

and allows updates to be completed easily as needed. 


Glen T. Daigger, Ph.D., P.E., BCEE, NAE 

Senior Vice President and Chief Technology Officer 

CH2M HILL 

9191 South Jamaica Street 

Englewood, CO 80112 USA 

Phone: (720) 286-2542 • Email: gdaigger@ch2m.com 



25

The website was initially completed and made available in 2002, then updated in 2004 due to 

the rapid development of the technology (Schwartz et al., 2006). Key observations associated 

with this knowledgebase are summarized below. 

Key Observations 

1. Several thousand MBR installations exist on a worldwide basis, with significant 

installations located on virtually every continent. A wide range of wastewaters are 

treated in MBRs, including municipal and a diverse range of industrial wastewaters, 

along with other applications such as landfill leachate. 

2. The vast majority of existing MBR applications are small, reflecting historical approaches 

to the application of MBR technology (Crawford et al., 2000). However, MBRs are 

increasingly being applied to larger plants (Crawford et al., 2005; Daigger et al., 2002). 

3. Technical analysis indicates that MBR technology is ready for a wide range of 

applications in both developed and developing countries (Daigger et al., 2005), including 

advanced wastewater treatment, water reclamation and reuse, pretreatment prior to 

reverse osmosis for water reclamation, grey water recycling, and the treatment of highly 

polluted environmental waters (Fleischer et al., 2005). 

4. MBR design and application has progressed through “three generations,” beginning with 

small installations intended to reliably produce high-quality effluent with minimal 

attention, to modest sized facilities capable of not only removing biodegradable organic 

matter, but also removing nutrients (Crawford et al., 2000). Fourth generation plants 

are now being implemented that resemble larger, conventional wastewater treatment 

facilities, but are using MBRs rather than conventional biological processes (Daigger and 

Crawford, 2005; Daigger et al., 2002). 

5. As the size and complexity of MBR facilities have increased, the method of procuring 

MBR equipment for these facilities has evolved from one similar to that used to procure 

“package” wastewater treatment plants to that used to procure conventional wastewater 

treatment equipment (Crawford et al., 2002). As a consequence, owners (and their 

engineers) are taking increased responsibility for the overall design of the wastewater 

treatment plant and are more carefully defining the responsibilities and scope of supply 

of the membrane suppliers. 

6. The performance characteristics of MBRs are increasingly well understood (Schwartz et 

al., 2006), resulting in increased consensus on the design of these facilities (Daigger and 

Crawford, 2005; Daigger et al., 2002). 

A result of these trends is that MBRs are becoming an accepted approach to wastewater 

treatment that can be successfully applied to a wide range of applications and facility sizes. 

The features of MBRs lead some to conclude that they can play an important role in delivering 

needed water to even the most disadvantaged worldwide, thereby playing an important role in 

meeting Millennium Development goals (DiGiano et al., 2004). 

26

References 

Crawford, G., G. Daigger, J. Fisher, S. Blair, and R. Lewis (2005). “Parallel Operation of Large Membrane 

Bioreactors at Traverse City.” Proceedings of the Water Environment Federation 78 th Annual Conference & 

Exposition, Washington DC, CD-ROM. 

Crawford, G., A. Fernandez, A. Shawwa, and G. Daigger (2002). “Competitive Bidding and Evaluation of 

Membrane Bioreactor Equipment – Three Large Plant Case Studies.” Proceedings of the Water Environment 

Federation 75 th Annual Conference & Exposition, Chicago, IL, CD-ROM. 

Crawford, G., D. Thompson, J. Lozier, G. Daigger, and E. Fleischer (2000). “Membrane Bioreactors – A 

Designer’s Perspective.” Proceedings of the Water Environment Federation 73 rd Annual Conference & 

Exposition on Water Quality and Wastewater Treatment, Anaheim, CA, CD-ROM. 

Daigger, G.T., B.E. Rittmann, S. Adham, and G. Andreottola (2005). “Are Membrane Bioreactors Ready for 

Widespread Application?” Environmental Science and Technology, 399A-406A. 

Daigger, G.T. and G.V. Crawford (2005). “Incorporation of Biological Nutrient Removal (BNR) Into Membrane 

Bioreactors (MBRs).” Proceedings of the IWA Specialized Conference, Nutrient Management in Wastewater 

Treatment Processes and Recycle Streams, Krakow, Poland, 235. 

Daigger, G.T., G.V. Crawford, and J.C. Lozier 2002). “Membrane Bioreactor Practices and Applications in 

North America.” Proceedings of the First Leading Edge Drinking Water and Wastewater Treatment Technology 

Conference, International Water Association. 

Daigger, G.T., G. Crawford, A. Fernandez, J.C. Lozier, and E. Fleischer (2001). “WERF Project: Feasibility of 

Membrane Technology for Biological Wastewater Treatment – Identification of Issues and MBR Technology 

Assessment Tool.” Proceedings of the Water Environment Federation 74 th Annual Conference & Exposition, 

Atlanta, GA, CD-ROM. 

DiGiano, F.A., G. Andreottola, S. Adham, C. Buckley, P. Cornel, G.T. Daigger, A.G. Fane, N. Galil, J.G. Jacangelo, 

A. Pollice, B.E. Rittmann, A. Rozzi, T. Stephenson, and Z. Ujani (2004). “Safe Water for Everyone.” 

Water Environment and Technology, 31-35. 

Fleischer, E.J., T.A. Broderick, G.T. Daigger, A.D. Fonseca, R.D. Holbrook, and S.N. Murthy (2005). 

“Evaluation of Membrane Bioreactor Process Capabilities to Meet Stringent Effluent Nutrient Discharge 

Requirements.” Water Environment Research, (77): 162-178. 

Schwartz, A.E., B.E. Rittmann, G.V. Crawford, A.M. Klein, and G.T. Daigger (2006). “Critical Review on the 

Effects of Mixed Liquor Suspended Solids on Membrane Bioreactor Operation.” Separation Science and 

Technology, In Press. 

GLEN T. DAIGGER, Ph.D., P.E., BCEE, NAE, is a recognized expert in wastewater 

treatment, especially the use of biological processes. At present, he is a Senior Vice 

President and Chief Technology Officer for the international consulting engineering 

firm CH2M HILL, where he has been employed for over 23 years. Among his 

responsibilities, he oversees wastewater process engineering on both municipal and 

industrial wastewater treatment projects on a firmwide basis. He is also the first 

Technical Fellow for the firm, an honor recognizing the leadership that he provides 

for CH2M HILL and for the profession in the development and implementation of 

new wastewater treatment technology. From 1994 to 1996, Daigger also served as Professor and Chair 

of the Environmental Systems Engineering Department at Clemson University. In addition, he formerly 

served as Chair of the Board of Editorial Review of Water Environment Research and as Chair of the 

Water Environmental Federation Technical Practice Committee. He is currently Chair of the 

Committee Leadership Council. Daigger received a B.S. and M.S. in Civil Engineering and a Ph.D. in 

Environmental Engineering from Purdue University. 



27


Design, Procurement, and Costs 

of Membrane Bioreactor Systems 

STEPHEN M. LACY, P.E., DEE 


Las Vegas, Nevada 

The membrane bioreactor (MBR) has integrated microfiltration with activated sludge to 

create a space-efficient facility capable of producing high-quality water. Like any process, 

there are advantages and disadvantages to using MBRs. Because of rapid growth in the 

application of plant configurations, it is important to understand the design principles 

necessary to result in a successful installation. Since MBRs are used in both large and 

“end-of-pipe” facilities, understanding the limitations of the process and the proper sizing 

of components becomes critical to success. 

The MBR process can have the same features and performance of any advanced secondary or 

Biological Nutrient Removal (BNR) facility, combined with the flexibility and performance of 

membrane filtration. In general, the membrane portion functions as a solid-liquid separation 

process. The effluent from an MBR can be expected to outperform any traditional or 

conventional treatment system. 

Initially, MBRs were installed in small facilities to handle a wastewater flow from a small area, 

or as a scalping plant to supply reuse-quality water to an individual user. Today, MBRs are 

seeing an expanded use as “end-of-pipe” facilities and to supply clusters of reuse water users 

as remote reclamation facilities. 

In this presentation, we will discuss several important design concepts and suggest design 

parameters that will provide flexibility in the operation of facilities, including the ability to 

properly maintain components. We will also discuss a procurement process for the membrane 

system. Finally, we will look at some of the costing developed for scalping-type facilities. 

Design Considerations 

It is important to note that with an MBR, there is no other option for producing an effluent 

other than through the membranes. The configuration of an MBR is greatly impacted by 

whether the facility will be used as a scalping plant or “end-of-pipe” treatment plant. 

Understanding both 1) how the MBR is being applied and 2) the required components needed 

for reliable operation are critical to proper design. Several MBR design considerations that 

will be discussed during the presentation include: 

• Screening (which is critical). 

• Handling peak flows. 


Stephen M. Lacy, P.E., DEE 


3014 West Charleston Boulevard 

Las Vegas, NV 89102 USA 

Phone: (702)878-8010 • Email: stephen.lacy@mwhglobal.com 



29

• Membrane flux rate (which should be selected to allow flexibility). 

• Foam control. 

• Waste sludge handling. 

• Low demand at scalping plants. 

A typical layout of an MBR facility configured for full BNR treatment is shown in Figure 1. 

This presentation will discuss the configuration of return streams and how to gain some 

advantage from the air used to agitate the membranes and avoid negatively impacting the 

biological process. 

Solids Recirculating System 

Anoxic 

Zones 

Screened 

& Degritted 

Wastewater 

Anaerobic 

Zones 

OxicZones 


Bays 

MLSS Recycle System 

Selectors Nitrification Membranes 

Figure 1. MBR flow schematic. 

Procurement of Membrane Systems 

MBR systems that are commercially available today do not lend themselves to a common 

design arrangement, thereby requiring custom application of each manufacturer’s system. 

There are three general ways to proceed with the selection and procurement of an MBR system: 

• Sufficiently isolate the membrane system from the remainder of the process units so 

that the system is independent with minimal impact on the plant layout, allowing the 

design to proceed without specific details required of the membrane system. 

• Implement the project on an alternative delivery basis, allowing the design-builder to 

select and work with a membrane system supplier. 

• Procure the membrane system early in the project design so that the facility is 

configured around specific equipment. 

In this presentation, we will focus on the latter of the options. 

The early procurement of the membrane systems can shorten the project schedule by allowing 

both the designers to customize the design around the specific equipment being installed and 

the equipment supplier to commence manufacturing while design is underway. Commonly, 

this procurement is accomplished in a two-step process. The first is a qualification-based 

selection to create a short-list of manufacturers. These manufacturers are invited to furnish 

proposals for their equipment as part of the second step. Because the equipment is varied in 

configuration and operation, an evaluated bid process is used to review the proposals and the 

final selection of the supplier. 

30

Cost Analysis of Membrane Bioreactor Systems for Water Reclamation 

Cost estimates were developed for full-scale MBR reclamation (scalping) systems ranging from 

0.2 to 10 million gallons per day (mgd). These estimates included both capital and operational 

costs related to the MBR process and subsequent disinfection. The costs associated with the 

membrane portion of the MBR systems were developed from cost quotes from four leading 

MBR suppliers. All other costs, including headworks, biological process, and disinfection 

costs, were estimated from preliminary conceptual design. Results of the analysis indicate 

that the total costs ($/1000 gallons) for 1-mdg MBR water reclamation systems, designed 

to operate on raw wastewater, ranged from $1.81 to $2.24. 

STEPHEN M. LACY, P.E., DEE, has more than 30-years experience in all facets of 

water and wastewater projects, from development through construction. He is a 

Project Manager for MWH Americas, Inc., working with the wastewater technical 

group. Over the past several years, Lacy has been involved in the testing, evaluation, 

and conceptual design for clients who are considering membrane treatment of their 

wastewater. He has also looked at wastewater membranes in the membrane 

bioreactor process and ultrafiltration of secondary effluent using submerged and 

pressure membrane configurations. A member of the Nevada Water Environment 

Association, he is currently Co-Chairman of both the Professional Development and Government Affair 

Committees. Lacy received a B.S. in Civil Engineering and an M.E. in Sanitary Engineering from the 

University of Idaho. 



31


Retrofit of an Existing Conventional Wastewater 

Treatment Plant with Zenon Membrane 

Bioreactor Technology 

DAVE N. COMMONS 

City of Redlands Municipal Utilities Department 

Redlands, California 

On May 31, 2001, the State of California Waste Discharge Requirement (WDR) permit 

for the wastewater treatment facility of the Wastewater Division of the City of Redlands 

Municipal Utilities Department was modified from requiring a Total Inorganic Nitrogen (TIN) 

12-month average effluent limitation of 15 milligrams per liter (mg/L) to a new permit effluent 

compliance level of 10 mg/L. The wastewater treatment plant, as configured at that time, 

could not meet this new compliance limitation because of insufficient aeration basin capacity. 

Because California was experiencing energy shortages in 2001, the City of Redlands 

Wastewater Division was also asked to provide to the Mountain View Power Company (a 

division of the Southern California Edison Company) a reliable source of high-quality cooling 

water that was not only low in total suspended solids (TSS) and biochemical oxygen demands 

(BOD), but also had less than 5 mg/L of total phosphates. 

The Wastewater Division evaluated the capability of a step feed, multi-anoxic zone nitrification/ 

denitrification treatment process modification with both pre-anoxic and post-anoxic zone 

configurations to the current treatment process to meet these nutrient requirements. It was 

determined that even thought both of these process modifications met the required effluent 

TIN limitation of 10 mg/L, neither would be able to meet the effluent TIN limitation on a 

sustained basis. It was also determined that the Division would not meet the total phosphates 

requirement of the power plant with the current plant configuration and treatment processes. 

After an extensive evaluation of the capabilities of conventional granular filtration technology 

versus membrane bioreactor (MBR) technology in different configurations, the City decided to 

upgrade 22.7 megaliters per day (ML/d) (6.0 million gallons per day [mgd]) of the Wastewater 

Division’s 35.96 ML/d (9.5 mgd) secondary-level activated sludge facility to a full tertiary-level 

treatment by using a dual-stage MBR facility. The dual-stage MBR configuration places the 

membrane cassettes in separate bioreactor tanks rather than within aeration basins. It was 

also decided that because the plant used anaerobic digestion for biosolids stabilization and 

because space was limited in the aeration basins for separate anaerobic zones, chemical 

precipitation using iron salts would be used for phosphate removal instead of using biological 

phosphorus removal. The iron salts were chosen over aluminum salts because ferrous chloride 

was already being used in the facility for hydrogen sulfide control in the anaerobic digesters. 


Dave N. Commons 

Water Operations Manager 

City of Redlands Municipal Utilities Department 

P.O. Box 3005 

35 Cajon Street, Suite 15A 

Redlands, CA 92373 USA 

Phone: (909) 798-7588 • Email: dcommons@cityofredlands.org 



33

This presentation will give a description of the treatment technology evaluation that led to the 

decision to construct an MBR facility instead of using conventional granular filtration 

technology to meet California’s Title 22 requirements for reclaimed water usage. A detailed 

evaluation of the start-up problems will then follow. This will include dealing with such issues 

as a lower-than-expected aeration influent soluble BOD, which required evaluating long-term 

methanol addition to resolve the low soluble BOD issue. An extensive explanation of start-up 

procedures will then follow, which will include testing protocol, treatment methodology 

experimentation, and treatment evaluation results that were necessary for the Wastewater 

Division to bring this dual-stage MBR facility into compliance with the both the State of 

California WDR permit requirements and the needs of the electrical power generating facility. 

The final section of the presentation will deal with a discussion of long-term process problems, 

challenges, and recommendations that resulted from the start-up and operations of a full 

tertiary treatment level, dual-stage MBR wastewater reclamation facility. 

As more wastewater treatment facilities use MBR facilities to meet high-quality wastewater 

effluent criteria needed for water reclamation because of the technology’s ability to meet 

high-level criteria on a consistent, low-cost basis, it is importance to evaluate the operational 

problems and challenges that these plants present. This presentation will provide insights into 

both start-up and long-term operating process issues. Since this conference is being held in 

California, a discussion of the operational issues and problems of the largest membrane 

bioreactor facility in the State of California (at the time of this submission), where water 

reclamation issues are paramount, should be relevant to conference attendees. 

Further Reading 

Commons, D. (2002). Twenty Week Evaluation of the Multi-Anoxic Zones Nitrification/ Denitrification 

Treatment Process for Removing Low Level Total Inorganic Nitrogen at the City of Redlands, California 

Wastewater Treatment Facility, WEFTEC 2002, Chicago, IL. 

Commons, D., G. Beliew, S.S. Nedic, and J. Cumin (2005). “MBR Reduces Potable Water Use, Increases 

Revenue,” Waterworld, September, Volume 21, No. 9. 

Pearson, D. (2005). “New Dual-Stage MBR Technology Yields Higher Quality Effluent at Reduced Operating 

Costs,” Industrial Waterworld, March/ April, Volume 6, No. 2. 

U.S. Environmental Protection Agency (1987). Phosphorus Removal, EPA/625/1-87/001, Washington, D.C. 

U.S. Environmental Protection Agency (1993). Nitrogen Control, EPA/625/R-93/010, Washington, D.C. 

Water Environment Federation (1996). Operation of Municipal Wastewater Treatment Plants, Volume III, 5 th 

Edition, Alexandria, VA. 

Water Environment Federation (1998). Biological and Chemical Systems for Nutrient Removal, Special 

Publication, Alexandria, VA. 

34

DAVE N. COMMONS has over 25 years of experience with wastewater treatment 

and collection and over 18 years of experience in the water treatment and distribution 

field. At present, he is the Water Operations Manager for the City of Redlands 

Municipal Utilities Department, where he oversees all City water supply sources, 

water and wastewater treatment facilities, and potable water distribution and 

wastewater collection systems, among others. Prior to joining the City of Redlands, 

he was the Water Utilities Operations Manager for the City of Corona Water Utilities 

Department in California and Field Operations Division Manager for the Sarasota 

County Utilities Department in Florida. Commons received a B.A. in Divinity and Education from 

Antioch Baptist Bible College and a Masters degree in Divinity and Religious Education from 

Southwestern Baptist Theological Seminary. He also holds Grade V Wastewater Operator, Grade T5 

Water Operator, and D5 Distribution Operator certificates in the State of California, with equivalent 

wastewater certificates in both the States of Georgia and Florida. 



35


Retrofit of an Existing Conventional Wastewater 

Treatment Plant with USFilter Membrane 

Bioreactor Technology 

JOHN HATCHER 

Oconee County Utility Department 

Watkinsville, Georgia 

In 2002, the Oconee County Utility Department (OCUD) sought to increase plant capacity 

at Calls Creek Wastewater Treatment Plant in Georgia. Different traditional treatment 

processes were looked at and weighed against the quality of the effluent that each produced. 

For the cost and quality of the system, membrane microfiltration emerged as the leading 

candidate. Traditional equipment would provide the quality of water needed to meet the 

present discharge permit, but may not have met it in the future. The quality of the water 

produced by membranes surpassed any other available technology for the price, and the 

decision was made to proceed in that direction. 

After deciding on the manufacturer, a pilot plant was provided by USFilter for evaluation and 

testing. The pilot plant passed all testing and met the effluent quality parameters that were 

needed. After completion of the pilot, OCUD moved forward with awarding the bid to 

USFilter to complete a design/build upgrade at Calls Creek. 

The construction process worked alongside the existing Orbal aeration basin and was 

integrated into it. Submersible pumps were installed in the center channel of the aeration 

tank, which pumped the mixed liquor into ultrafine wedge wire rotary screens. The screens 

removed all types of trash before the mixed liquor entered the membrane bioreactor (MBR) 

building for filtration. After filtration, the effluent was discharged to the existing ultraviolet 

system for disinfection before final discharge. The return activated sludge leaving the MBR 

was sent back to the aeration tank to begin the process all over again. 

The MBR system went online in April 2004 and has been in service since then. The system 

has provided high quality effluent and has allowed OCUD to look into the possibility of 

providing the treated effluent back to our customers as reuse water for irrigation. 


John Hatcher 

Wastewater Supervisor 

Oconee County Utility Department 

P..O Box 88 

Watkinsville, GA 30677 USA 

Phone: (706) 769-3963 • Email: callscreek@msn.com 



37

38 

JOHN HATCHER is the Wastewater Supervisor for Oconee County Utility Department, 

which provides drinking water and sanitary sewer service to its customers within the 

service areas inside Oconee County, Georgia. As Wastewater Supervisor, he is 

responsible for the daily operation and compliance of a conventional wastewater 

treatment plant and a land-application wastewater plant. Recently, he won two 

awards from the Georgia Water and Pollution Control Association, one of which was 

for the Calls Creek Wastewater Treatment Plant, which discharges into the Calls 

Creek watershed. Hatcher received a B.S. in Environmental Health Science from 

the University of Georgia. He is also a licensed water and wastewater treatment plant operator in the 

State of Georgia.

Session 3: Case Studies - Real-World Issues with Membrane Bioreactors 

Membrane Bioreactor Applications: 

A Global Perspective 




Pilot-Plant Studies 

Since membrane bioreactor (MBR) performance is highly dependent upon feedwater 

quality, a true comparison of the performance of different MBR technologies can only be 

achieved when they are tested against the same feedwater matrix. A number of comparative 

pilot trials have been conducted over the past 5 years, which permit a useful technology 

comparison (Table 1), albeit with certain caveats. The studies identified in Table 1 have all 

been conducted this millennium, and all employ at least one full-scale membrane module and 

at least three different technologies. Not all of these studies have been published, however. 

Table 1. 

Comparative Pilot-Plant Trials 

Reference 

Technology Adham Van der Tao Honolulu Lawrence Trento EAWAG 

Tested et al. Roest et al. et al. 

(2005) et al. (2005) (2005) 

(2002) 

Zenon X X X X X X 

Kubota X X X X X X 

Mitsubishi Rayon X X X X X 

Norit – X – 

Huber (X) X 

Memcor X X X 

Toray 

X 

Comparative Parameters 

To allow a comparison of disparate sets of data from various full-scale plants, normalization of 

the data is required. The most convenient parameters to use are flux (J, liters per cubic meter 

per hour [LMH]), permeability (K, LMH/bar), and specific aeration demand with respect to 

membrane area (SAD m , Nm 3 hr -1 m -2 or m hr -1 ) and permeate volume (SAD p , Nm 3 air per m 3 

permeate [i.e., unitless]). A comparison of such data for full- and pilot-scale plants is provided 

in Table 2. 




Building 61 






39

Table 2. Summary of Key Parameters 

Cap 1 Flux K SAD m 

2 SAD p 

2 MLSS Filt. cycle3 (min) Cleaning Cycle 4 

(MLD) (LMH) (LMH/bar) (Nm/h) (–) (g/L) on r or b Interval Type 

Zenon 

p 20 225 0.54 27 10-11 

p 35 225 0.54 15 10-11 

p 37.2 270 0.52 14 8-10 9.5 0.5b 

p 16 120 0.33 22 9 1b 

p 10 200 0.54 28 7 5 0.5b 

p 12.4 124 5 0.31 25 4-13 12 0.5b 

2* 18 95 1 56 15 10 0.75b 1w/6m mCIP/R 

48 18 144 0.29 16 8-10 10.5 1.5r 1w/15m mCIP/R 

0.15,i 12 71 0.65 54 10-15 10 0.5b 0.5w mCIP 

48 25 175 0.4 17 12 7 1 0.5m mCIA 

Mitsubishi Rayon 

p 7.5 200 0.33 52 9-12 1200 240r 

p 4.8 90 0.37 38 8 8 0.5b/1.5r 

0.38 10 30 0.65 65 12 

p 23 140 1 45 8-14 12 2r 

p 20 66 5 0.48 20 6-14 13 2r 

USF Memcor 

p 21.7 150 0.39 18 6-8 

p 21 182 0.2 17 

0.61 16 150 5 0.18 11 

Asahi-kasei 

0.9,i 16 80 0.24 15 Ind 

Koch Puron 

0.63 25 160 0.25 10 Mun 5 3w mCIP 

Kubota 

p 10.4 650 0.75 75 10-12 8 2r 

p 25 250 0.6 24 9-12 9 1r 

p 15 261 0.98 79 9 1r 

p 9.5 200 1.5 88 8 8 2r 

p 26 650 4 0.94 39 6-12 9 1r 

1.9 20 350 0.75 32 12-18 1380 60r 8-9m CIP 

13 33 330 1.06 32 8-12 1380 60r 6m CIP 

4.3 25 680 0.56 23 10-20 1-2 6m CIP 

Brightwater 

1.2 27 150 1.28 47 12-15 55 5r >18m CIP 

Toray 

0.53 25 208 0.54 22 6 

Huber 

0.11 24 250 0.35 22 Mun 9 1 none 

Colloide 

0.29 25 62.5 0.5 20 Mun 6 2 na 

1 Plant capacity or plant type (p = pilot plant); MLD = Megaliters per day. 

2 Specific aeration demand; Nm/h = Cubic namometers per hour air per cubic meters membrane. 

3 Filtration cycle (r = relaxation; b = backflush); on = Filtration period. 

4 Cleaning intervals (w = weeks; m = months). 

5 Maximum permeability. 

Intermittent aeration used for all Zenon plants other than *. 

CIP = Cleaning in place. mCIP = Maintenance cleaning in place. 

mCIP/R = Maintenance cleaning in place with relaxation. mCIA = Maintenance cleaning in air. 

40

It has generally been observed from lab-scale studies that attainable flux increases with increasing 

aeration rates due to increased scouring. This is manifested either as an increase in the 

critical or sustainable flux. In a full-scale plant, this would be expected to be manifested as an 

increase in sustainable net permeability with an increasing aeration rate. This, indeed, appears 

to be the case, with a general tendency for increasing permeability with increasing SAD m , 

though the data is highly scattered (Figure 1). Some of this data scatter can be attributed to 

obvious outliers, namely either a plant operating under sub-optimal conditions and/or a very 

small unstaffed plant, where blowers are more likely to be oversized to maintain permeability 

and, therefore, limit maintenance. Sustainable permeability also changes according to 

clearning protocols and the nature of aeration (i.e., the specifications of the aerator itself and 

the mode of application [continuous or intermittent]). Although physical cleaning is, to some 

extent, accounted for by using net rather than gross flux in calculating permeability, 

maintenance cleaning with hypochlorite permits higher permeabilities to be sustained. 

800 

700 

600 

500 

400 

300 

200 

100 

✶ 

▲ 

❖ 

♦ 

✦ 

✦ ❖ 

❖ ✦ 

✣ ▲ 

▲● 

■ 

✦ 

✦ 

✦ ❊ 

■ 

✦▲ 

■ 

■ 

■ 

■ 

▲ 

✦ 

■ 

✦ Zenon 

■ Kubota 

▲ M Rayon 

❖ USF 

✶ Huber 

● Colloide 

✣ Asahi-k 

♦ Puron 

✧ Brightwater 

❊ Toray 

✧ 

■ 

0 

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 

SADm, NM^3/hr per m^2 

Figure 1. Operating permeability versus specific aeration demand for data in Table 2. 

If the more obvious outliers are ignored, then some general trends can be identified from 

the data: 

a) Flat sheet (FS) systems tend to operate at high permeabilities (generally >200 LMH/bar) 

and are associated with high aeration demands, both as SAD m and SAD p . No trend 

is evident in this data subset, though all but the highest (and probably non-optimal) 

SAD p values lie within the range 20 to 39. 

b) Hollow fiber (HF) systems tend to operate at lower permeabilities (generally 

Physical cleaning appears to be predominantly by relaxation rather than by backflushing. 

Pilot−plant data indicate that the downtime for physical cleaning accounts for between 4 and 

20 percent of the operating time, with no profound difference between the two configurations. 

On the other hand, maintenance cleaning every 3 to 4 days using relatively low concentrations 

of hypochlorite (250 to 500 milligrams per liter [mg/L]) is routinely employed for the Zenon 

technology, whereas chemical cleaning is limited to infrequent recovery cleans alone for 

FS systems. For both FS and HF systems, such cleans are generally applied at intervals of 

6 to 18 months (depending on the flux) and generally employ hypochlorite concentrations 

between 1,000 and 5,000 mg/L sodium hypochlorite (NaOCl). Both maintenance and 

recovery cleaning are either brief or infrequent enough to add little to the percentage 

downtime. For example, an overnight soak of 16 hours every 6 months amounts to less than 

0.25 percent in such cases. For Zenon plants, the maintenance cleaning cycle is complete 

within 10 minutes and is employed no more than three times a week, again amounting to less 

than 0.4-percent downtime. Thus, for the majority of the most recent plants, the ratio of the 

net-to gross flux is determined by a period of relaxation alone, and the most onerous impact of 

chemical cleaning is chemical usage and chemical waste discharge. 












Science from Southampton University, and a Ph.D. in Filtration Science from Cranfield University. 

42


Membrane Aeration, Biofilms, 

and Membrane Bioreactors 

MICHAEL J. SEMMENS, PH.D., P.E. 

University of Minnesota 

Minneapolis, Minnesota 

The theory of membrane gas transfer has been studied and characterized in detail over the 

past 30 years. It is possible to accurately predict the gas transfer performance of 

membranes using numerous dimensionless correlations if the membrane area and operating 

conditions are known. Membranes are now widely used for gas transfer in a variety of 

applications, including blood oxygenation, vacuum degassing, and pervaporation. 

Environmental applications of membrane gas transfer have been slower to develop because of 

problems with biofilm fouling of the membrane surface. If we are to design effective 

membrane gas transfer processes for water/wastewater treatment, we need to understand how 

these biofilms impact gas transfer. How do these biofilms behave? Is biofilm formation 

always a bad thing or are there advantages? This presentation will examine the influence of 

biofilms on the gas transfer performance of membranes and explore opportunities for novel 

applications in membrane bioreactors. 

PROFESSOR MICHAEL J. SEMMENS, P.E., is Professor in the Department of 

Civil and Mineral Engineering at the University of Minnesota, where he has taught 

since 1977. His research interests include the development of physical and chemical 

processes for water, wastewater, and waste treatment; processes to identify factors 

that limit mass transfer and the kinetics of separation; membrane bioreactors, module 

design, and membrane applications in water and wastewater treatment; and the use 

of membranes for controlled gas delivery in biologically active environments, such as 

groundwater and sediment remediation projects, and wastewater treatment. 

Semmens received a B.S. in Chemical Engineering from the Imperial College of Science and Technology 

in London, England, an M.S. in Environmental Engineering from Harvard University, and Ph.D. in 

Environmental Engineering from University College in London, England. 


Michael J. Semmens, Ph.D., P.E. 

Professor, Department of Civil Engineering 

University of Minnesota 

500 Pillsbury Drive SE 

Minneapolis, MN 55455 USA 

Phone: (612) 625-9857 • Email: semme001@umn.edu 



43


Future Outlook on 

Membrane Bioreactor Technology 




Challenges 

Two areas having a direct bearing on the effective and efficient operation of membrane 

bioreactors (MBRs) are 1) cleaning and 2) dynamic effects. The cleaning of surfaces, as 

a subject for scientific investigation, pre-dates membrane process development since the 

fouling of heat exchangers, and the consequent loss of thermal efficiency has been an issue for 

many years. The fouling and cleaning of membranes relating to industrial process separations 

have also been the subject of research and development for over 20 years. Compared to this, 

the science of membrane cleaning in the context of MBRs is a young one — there have been a 

great number of investigations of MBR fouling, but much less on the appropriate chemicals 

and protocol for recovering permeability for irreversibly fouled membranes. Given the large 

number of parameters that determine the degree of permanent fouling and the candidate 

variable parameters that could determine cleaning efficacy, the scope of a rigorous study of 

cleaning is potentially extremely broad. Thus, it is not surprising that cleaning protocols have 

been developed in an ad hoc way through heuristic investigation. 

Dynamic effects exert the greatest influence on consistency in MBR performance, ultimately 

leading to equipment and/or consent failures, but have also been largely overlooked by the 

academic research community. Specifications for full-scale MBR installations are generally 

based on conservative estimates of hydraulic and organic (and or ammoniacal) loading. 

However, in reality, these parameters fluctuate significantly. Moreover, even more significant 

and potentially catastrophic deterioration in performance can arise through equipment 

malfunction and operator error. Such events can be expected to produce over short periods of 

time (Table 1): 

• Decreases in mixed liquor suspended solids (MLSS) concentration (either through 

the loss of solids by foaming or by dilution with feedwater). 

• Foaming problems, usually associated with the above. 

• Loss of aeration (through control equipment malfunction or aerator port clogging). 

• Loss of permeability (through the misapplication of backflush and cleaning 

protocols, hydraulic shocks, or contamination of the feed with some unexpected 

component). 




Building 61 






45

Table 1. Key Dynamic Determinants and Their Impacts 

Determinants 

MLSS dilution 

Aeration loss 

Backflush/cleaning loss 

Hydraulic shock 

Saline intrusion 

Variables 

Dilution factor and rate of concentration increase 

Percentage and period of reduction 

Period of loss 

Rate and level of flow increase 

Ultimate concentration factor and rate of 

concentration decrease 

An example of feedwater constituent fluctuation is seawater intrusion. It has been recognized 

for some time that rapid changes in salinity can impact microbial physiology, increasing levels 

of organic matter (as chemical oxygen demand [COD] or biochemical oxygen demand [BOD]) 

arising in activated sludge process (ASP) effluent and decreasing microbial activity. However, 

the phenomenon has not been investigated for MBRs, where such physiological changes might 

be expected to impact fouling. Further examples include fats, oils, and grease (FOGs) and 

bacteriological inhibitory substances, since the latter can then alter the system microbiology 

and, therefore, generate fouling. 

Outlook 

Despite the limitation imposed by fouling, the future of membrane bioreactors in municipal 

and industrial wastewater treatment seems assured. Valued at an estimated $216.6 million in 

2005, the global MBR market is rising at an average annual growth rate of 10.9 percent, 

significantly faster than the larger market for advanced wastewater treatment equipment and 

more rapidly than the markets for other types of membrane systems. It is expected to 

approach $363 million in 2010 (Hanft, 2006). The number of installations for both of the 

leading suppliers has undergone exponential growth since the first pilot trials of the submerged 

process in 1989 (Figure 1), driven by opportunities presented by increasingly stringent 

environmental legislation and by ever-decreasing process costs (Figure 2). Further 

incremental improvements can be expected as more is understood about the interrelationship 

between biomass characteristics, permanent fouling, and cleaning, and as membrane costs 

continue to be driven downwards. More significant “quantum leap” improvements are less 

easily envisioned, however, and it remains to be seen whether any profoundly original MBR 

products will arise from current research and development activity. 

References 

Hanft, S. (2006). Membrane Bioreactors in the Changing World Water Market. Business Communications 

Company, Report C-240. 

Kennedy, S., and C. Churchouse (2005). Progress in Membrane Bioreactors: New Advances, Experiences, and 

Applications of Membrane Bioreactors in the Treatment of Domestic and Industrial Wastewaters. Wakefield, 

United Kingdom. 

46

Kubota 

Zenon 

1500000 

1250000 

1000000 

750000 

500000 

250000 

0 

1995 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

2004 

Figure 1. Cumulative installed capacity in cubic meters per day (m3/d) for Kubota and Zenon. 

Relative cost / m 3 at 100 l/s 

160 

140 

120 

100 

80 

60 

40 

@ 8640 m 3 /d 

Costs Projected in 

1999 

Rent and rates 

Sludge disposal 

Screenings 

Membrane replacement 

Chemicals 

Maintenance 

Power 

Amortised capital 

Actual Costs 

20 

0 

1992 1994 1995 1996 1998 2000 2002 2004 2005 

Year 

Figure 2. MBR process costs (Kubota) versus time (Kennedy and Churchouse, 2005). 



47

48 












Science from Southampton University, and a Ph.D. in Filtration Science from Cranfield University.

Membrane Bioreactors Short Course Abstracts - National Water ...

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