Membrane Desalination


Balaban Desalination Publications

Additional information at

Reverse Osmosis, Nanofiltration and Hybrid Systems

Process, Design, Applications and Economics

By Mark Wilf with chapters by: Leon Awerbuch, Craig Bartels, Mike Mickley, Graeme Pearce and Nikolay Voutchkov


This is process and application guidebook encompasses the latest state of the art of commercial membrane desalination technology.  This unique book provides a thorough overview and understanding of the RO, NF, and hybrid system, all with a detailed discussion on how to apply, design and operate potable systems and how to evaluate project economics using innovative membrane technologies.  A must read for all project engineers, plant designers, planners, utility directors, and operation managers, involved in municipal and industrial membrane projects.  Also scientists and academics interested in membrane desalination will find in this guidebook an insight into latest trends in commercial membrane desalination technologies for potable water applications.  A step by step approach to designing, operating and cost evaluation of membrane system is explained in simple practical terms, all backed up by sample process calculations and case studies.


The contents of the book provides information, education and real life examples of the following major subjects:


  • Principles of membrane separation – provides explanation of membrane technology and factors that affect membrane element performance in field operation.
  • RO/NF system configurations and system design parameters – provides information on major components, process steps and configuration of desalination plants and modern approach to membrane plant design process including optimization of power consumption.
  • Application of RO and nanofilotrtaion technology in wastewater reclamation plants – provides overview of suitable membrane technology for wastewater processing, practical range of design parameters and experience based performance expectation.
  • Cost estimation and planning process of membrane desalination projects – provides detailed information on cost factors to be considered in preparation of desalination project budget. It also includes detailed discussion on their relative importance in different types of desalination project alternatives such as Turn-key, DBB, DBO and BOOT.
  • Concentrate disposal – described in terms of concentrate disposal constrains and engineering solutions presently available. A detailed evaluation of economics of various concentrate disposal alternatives is included.
  • Hybrid systems – provides information on this new emerging technology and system configurations. It describes various alternatives of hybrid process configurations, potential economic benefits and provides range of operating parameters.
  • Appendixes section – includes examples of process configurations, budgeting of RO seawater system and detailed evaluation of a specific case of concentrate disposal.


The contributors to the book are well known professionals in the desalination field with extensive involvement in research and development of membrane products and desalination processes. The book contents reflect their R&D work and experience in design, procurement and operation of numerous membrane systems. The information included in this guidebook represents the current state of the art of commercial membrane desalination technology.



Table of contents


Introduction to reverse osmosis – basic terms

Water salinity – concentration units

The osmotic process

Permeate recovery

Average feed salinity

Net driving pressure

Salt separation in reverse osmosis process

Water transport

Salt transport

Salt passage and salt rejection

Temperature effect on transport rate

Average permeate flux

Specific permeability of a membrane

Concentration polarization

Commercial RO-NF membrane technology

Cellulose acetate membranes

Composite polyamide membranes

Membrane module configurations

Plate and frame membrane elements

Hollow fine fiber membrane elements

Spiral wound membrane elements

Spiral wound elements categories

RO system configuration

Membrane assembly unit

Concentrate staging

Flow distribution

Permeate staging

Partial two pass configuration

Calculation of system performance

Manual method of membrane system performance calculations

Use of computer programs for projection of membrane performance

Normalization of system performance

Feed water supply systems and pretreatment

Well water

Surface water

Raw water intake and concentrate discharge

Conventional filtration pretreatment

Membrane filtration pretreatment (by Graeme Pearce)

Chemical stabilization of permeate

RO/NF system design parameters

Feed water types

Feed water composition

Feed water temperature

Sparingly soluble constituents

Particulate matter

Organic matter


Permeate recovery ratio

Permeate flux rate

Membrane age

RO/NF system design

System design guidelines

The design process of RO/NF system

Site and feed water supply

Selection of pretreatment process

Energy consumption of RO process

Pumping equipment for RO applications

Optimization of energy consumption

Configuration of RO trains

Control and monitoring system

Permeate processing

Special design cases

Achieving low boron limits with seawater RO technology

Nitrate reduction with brackish RO membranes

System design verification through operation of a pilot unit.

System commissioning

System operation

Membrane fouling and performance restoration

Membrane elements fouling process

Performance restoration

Nanofiltration technology and applications (by Craig Bartels)

Nanofiltration overview

Nanofiltration membrane characteristics

Membrane types

Separation mechanism

Membrane properties

Nanofiltration process consideration

Pretreatment requirements

Process design features

Nanofiltrtaion applications

Potable water

Industrial process fluid purifications

Other applications

Wastewater treatment and reclamation by RO and NF process (by Craig Bartels)



Membrane selection

Wastewater reclamation process design

Permeate flux rate

Biofouling control

Recovery rate

Commercial plant data and design

Singapore wastewater treatment plants

Southern California wastewater treatment plants

Operating cost advantages

Other wastewater treatment applications



Budgeting of membrane desalination projects (by Nikolay Voutchkov)

Overview of desalination cost estimating procedure and practice

Project cost definition

Definition of capital cost

Definition of operating and maintenance cost

Definition of cost of water

Key factors influencing water cost

Cost factors within the control of plant owner

Project risk profile

Cost factors beyond the control of plant owner

Types and accuracy of project cost estimates

Conceptual cost estimates

Preliminary cost estimates

Budgetary cost estimates

Detailed cost estimates

Cost models

Preparation for project budgeting

Project cost estimation and analysis

Capital cost

Construction cost

Costs for project engineering services

Project development costs

Project financing costs

Operation and maintenance cost

Waste stream disposal

Environmental and performance monitoring

Indirect O&M cost

Cost of water

Fixed components of water cost

Other fixed costs

Variable components of water cost

Trends of water cost

Project implementation

Project delivery alternative

Design-Bid-Built (DBB)

Design-Bid-Operate (DBO)

Built-Own-Operate-Transfer (BOOT)

Project schedule

RO concentrate management (by Mike Mickley)

Nature of concentrate

Concentrate management options

Traditional concentrate disposal options

Concentrate disposal challenges

Consideration of concentrate management options

Beneficial use

Volume reduction

Zero liquid discharge

Seawater desalination discharge

Nanofiltration concentrate disposal

Other topics related to concentrate disposal

Presence of contaminants

Major ion toxicity

Hybrid Systems and Technology  (by Leon Awerbuch)

Hybrid – the new alternative

The “classic scheme”

The “classic scheme” variant

The once-through MSF scheme

The “duo-cycle ROMED” scheme

The direct-drive steam turbine scheme

R&D related to improving hybrid systems

Quantifying the benefits of the hybrid SWRO/thermal plant scheme in cogeneration stations.

Savings due to reduced seawater requirements

RO membrane Life

Membrane performance as a function of seawater temperature

Nanofiltration membranes performance as a function of  temperature

Savings due to control of SWRO plant feed temperature

Savings due to blending SWRO and distillation plants’ products

Increased recovery ratio

Feedwater deaeration

Hybrid plant cost savings – summary

Examples of existing hybrids

Hybrid variations

Hybrid Using Nanofiltration – Membrane Softening

Nanofiltration Hybrid Background

Design Experience with Nanofiltration Hybrid for MSF.

Design And Construction Of The Commercial Let NF Plant.

Nanofiltration Hybrid Variations

Hybrid Systems Using Vapor Compression Distillation

Hybrid Systems Using MSF-MED

Hybrid Systems and Desalination Aquifer Storage  Recovery (DASR)

Resources Conservation and Environmental Impacts of Various Hybrid Configurations





Examples of RO membrane unit configurations

Example of desalination plant cost estimate. (Nikolay Voutchkov)

Example of feasibility evaluation of RO concentrate disposal alternatives  (Mike Mickley)

Units conversion table

Common symbols used in process and instrumentation diagrams.