NATURAL ORGANICS REMOVAL USING MEMBRANES - CHAPTER 1 ppt

viii Contents 2.5.8 Charge and Acidity 2.5.9 Solubhty and Aggregation of Natural Organics 2.5.10 Micelle Formation of Natural Organics and Surfactant Characteristcs 2.5.1 1 Structure/Fr

NATURAL ORGANICS REMOVAL USING MEMBRANES

BY PHONE: 800-233-9936 Or 71 7-291 -5609, AM- PM Eastern Time

BY CREDIT CARD: American Express, VISA, Mastercard

PERMISSION TO PHOTOCOPY-POLICY STATEMENT

Authorization to photocopy items for internal or personal use, or the internal or personal use

of specificclients, is granted by Technomic Publishing Co., Inc provided that the base fee of

US $5.00 per copy, plus US $.25 per page is paid directly to Copyright Clearance Center,

222 Rosewood Drive, Danvers, MA 01923, USA For those organizations that have been granted a photocopy license by CCC, a separate system of payment has been arranged The fee code for users of the Transactional Reporting Service is 1-58716101 $5.00 + $.25

PRINCIPLES, PERFORMANCE AND COST

Scbd of Civil and Environmtul Engineeriw

University of New Soutb Wak, Australia

Natural Organics Removal Using Membranes

~ T E C H N O M I C ~ U ~ ~ ~ C ~ ~ ~ O ~

Technomic Publishing Company, Inc

851 New Holland Avenue, Box 3535

Lancaster, Pennsylvania 17604 U.S.A

Copyright O 2001 by Andrea I Schiifer

All rights reserved

No part of this publication may be reproduced, stored in a

retrieval system, or transmitted, in any form or by any means,

electronic, mechanical, photocopying, recording, or otherwise,

without the prior written permission of the publisher

Printed in the United States of America

l 0 9 8 7 6 5 4 3 2 1

Main entry under title:

Natural Organics Removal Using Membranes: Principles, Performance and Cost

A Technomic Publishing Company book

Bibliography: p

Includes index p 401

Library of Congress Catalog Card No 2001088343

ISBN NO 1-58716-093-5

F o r Moans Jade

This page intentionally left blank

2.2.1 Nature of Different Natural Organics

2.2.2 Definition of Compounds

Chemical Formation, Humification and Xgmg Biologcal Activity

Soil and Vegetation Weather and Seasonal Variations Lake Waters versus Freshwater Streams Groundwa ter

Pollution by Human Activity Availability for Research

2.4.1 Ion Eschange Resin

2.4.2 Reverse Osmosis

2.4.3 Desalting

2.4.4 Purification

2.5.1 Concentration Measurements of Natural Organics

2.5.2 Aromaticity and Reactivity

viii Contents

2.5.8 Charge and Acidity

2.5.9 Solubhty and Aggregation of Natural Organics

2.5.10 Micelle Formation of Natural Organics and Surfactant Characteristcs

2.5.1 1 Structure/Fractal Dimension of Natural Organics

2.6.1 Particulate/Dissolved Organic Carbon Separation

2.7.1 Effect of Organic Concentration

2.7.2 Effect of Ionic Strength

2.7.3 Effect of pH

2.8 INTERACTIONS OF NATURAL ORGANICS WITH OTHER SOLUTES 26

2.8.1 Cations

2.8.2 Trace Metals

2.8.3 Interactions with Other Compounds

2.9.1 Characterisation of Natural Organics and Colloid Systems

2.9.2 Organic Adsorption onto Colloids

2.9.3 Colloid Stabilisation and Mobilisation

2.9.4 Aggregate Formation and Structure

2.10.1 Drinking Water Standards

2.10.2 Treatabllity of Natural Organics by Different Processes

2.10.3 Disinfection By-Product Formation

2.10.4 Bacterial Regrowth, B i o f h s and Conditioning Films

2.10.5 Membrane Fouling

Chapter 3 - Membrane Review 39

Contents ix

3.3.1 Membrane Materials for hIF and UF

3.3.2 Membrane Materials for N F and R 0

3.3.3 TFC Membrane Modification in N F

3.3.4 Membrane Selection, Testing and Evaluation

3.4.1 hficrofdtration (MF) 55

3.4.2 Ultrafiltration (Ul?) 55 3.4.3 Nanofdtration and Reverse Osmosis 57 3.4.4 Variation of Rejection due to Fouling 62

3.5.1 Organic Fouling 63 3.5.2 Inorganic F o u h g or Scaling 68 3.5.3 Colloid and Particle Fouling 69

3.6.1 Microscopic Techniques

3.6.2 Surface Charge

3.6.3 Hydrophobicity and State of Water

3.6.4 Deposit Morphology and Surface Analysis

3.7.1 Pretreatment for Rejection Increase and Fouling Prevention

3.7.2 Backwashing, Backflushing, and Operation Mode

3.7.3 Membrane Cleaning

3.8 MEMBRANE PROCESS APPLICATIONS I N WATER TREATMENT 84

3.8.1 Membrane Processes versus Conventional Treatment

3.8.2 Membranes versus other Alternatives

3.8.3 Micro filtration

3.8.4 Ultrafiltration

3.8.5 Nanofdtration and Reverse Osmosis

3.8.6 Hybrid Membrane Processes

3.8.7 Cost

4.6.3 Inductively Coupled Plasma L\tomic Emission Spectroscopy (ICP-L\ES)

4.6.4 Ion Chromatography (IC)

4.7.6 Cation Content of Organics

4.7.7 High Performance Size Exclusion Chromatography (HPLC-SEC)

4.7.8 Ultra filtration Fractionation

4.7.9 Liquid Chromatography - Organic Carbon Detection &C-OCD)

4.7.10 Humic Solubhty and Aggregation

4.7.11 Viscosity

4.7.12 Matrix Assisted Laser Desorption/Ionisation (MALDI)

4.7.13 Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT)

4.8.1 Stable Hematite Colloids in Absence of Organics

4.8.2 Colloids at pH 3 with Organics

4.8.3 Reaction Limited Aggregation @M)

4.8.4 Diffusion Limited Aggregation (DLA)

4.8.5 SPO: Aggregates with Organics

4.8.6 OPS: Colloids Stabilised with Organics

4.8.7 Coagulation

4.9.1 Zeta Potential and Mobhty of Particles

4.9.2 Particle Size and Structure ;inalysis/Fractal Dimension (Malvern)

4.9.3 Aggregate Size

4.9.4 ,iggregate Structure

4.9.5 Photon Correlation Spectroscopy (PCS)

4.10.1 Zeta Potential of Membranes

4.10.2 Field Emission Scanning Electron mcroscopp (FESEhl)

4.10.3 Electron Dispersive Spectra (EDS)

Contents xi

4.10.4 X-Ray Photoelectron Spectroscopy P P S )

4.10.5 Contact Angle Measurements

4.10.6 Determination of Membrane Mass Deposit

Chapter 5 - MicrojItration 131

5.4 MF O F ORGANICS I N T H E ABSENCE O F INORGANIC COLLOIDS l36

5.5 M F O F INORGANIC COLLOIDS I N T H E ABSENCE O F ORGANICS 137

5.5.1 Effect of Primary Particle Size

5.8.1 Effect of Membrane Type 148 5.8.2 Effect of Organic Type and Concentration 148 5.8.3 Effect of Primary Particle Size 149 5.8.4 Effect of Calcium Concentration 149 5.8.5 Effect of pH 149

5.9.1 Stable Colloids in the Absence of Organics

5.9.2 Aggregated Colloids with Subsequent Adltion of Organics (SPO)

5.9.3 Stabilised Colloids (OPS)

6.3.1 Pure Water Flus

6.3.2 Molecular Weight Cut-Off or Pore Size

6.3.3 Membrane Surface Rdughness

6.3.4 Membrane Surface Charge

6.41 Effect of Ionic Strength

6.4.2 Effect of pH

6.4.3 Effect of Organic Concentration

6.4.4 Effect of Calcium Concentration

6.4.3 Effect of Organic Type

6.4.6 Cation Rejection by UF

6.4.7 UV254,,/DOC Ratio

6.4.8 Comparison of UF Fractionation and Size Exclusion Chromatography (SEC)

6.4.9 Chemical Analysis of the UF Fractions Using LC-OCD

6.5.1 Theoretical Considerations

6.5.2 Effect of KC1

6.5.3 Effect of CaClz

6.5.4 Effect of pH

6.5.5 Effect of IHSS Fulvic Acid

6.5.6 Aggregate Characteristics and Their Effect on Membrane Filtration

6.6.1 Calcium Concentration

6.6.2 Organic Type

6.6.3 Effect of Flus on Fouling

6.6.4 Blochng Law Analysis

6.7 FILTRATION OF INORGANIC COLLOIDS A N D ORGANICS 197

6.7.1 Stable Colloids in the Absence of Organics

6.7.2 Aggregates in the Absence of Organics

6.7.3 Colloids Stabhsed by Organics (OPS)

6.7.4 Aggregates in Presence of Organics (SPO)

6.7.5 Comparison of klembrane Deposits Formed by OPS and SPO Systems

Contents xiii

6.8.1 Effect of Ferric Hydroside Flocs on Flus in the *ibsence of Organics

6.8.2 Effect of Ferric Chloride on Rejection and Flus

6.8.3 Coagulation of OPS Systems

6.8.4 Coagulation of SPO Systems

6.8.5 Blochng Law Analysis

7.2.1 Membrane Compaction and Baseline

7.2.2 Protocol for Rejection Experiments

7.2.3 Protocol for Recycle Experiments

7.3.1 Effect of Temperature on Water Flux

7.3.2 Membrane 'Pore Size'

7.3.3 hIembrane Surface Charge

7.3.4 Surface Roughness

7.3.5 Contact Angle

7.4.1 Salt Rejection in the Absence of Organics

7.4.2 Organics and Salt Rejection in Synthetic Surface ?Vater Solutions

7.5.1 Mass Balance for Deposit Calculations

7.5.2 Estimation of Adsorption of Organics on Membrane Surface

7.5.3 Concentration Polarisation and Osmotic Pressure

7.5.4 Mass Transfer Coefficient and ?Vall Concentration

7.5.5 Osmotic Pressure in Solutions and Boundary Layer

7.5.6 Solubility of Calcium and Natural Organic Matter (Nob9

7.6.1 Effect of Background Electrolyte

7.6.2 Effect of Organic Type

7.6.3 Effect of Calcium Concentration

7.6.4 Critical Fouling Conhtions

7.6.5 Effect of Organic Concentration and Type

7.6.6 Effect of pH

7.6.7 Effect of Transmembrane Pressure

7.6.8 Effect of Inorganic Colloids

xiv Contents

7.7.1 Effect of Organic Type 265 7.7.2 Effect of Ferric Chloride on Treatment of Solutions containing Colloids and H A 266 7.7.3 Effect of Ferric Chloride Addition at Critical Fouling Conditions 268 7.7.1 Permeate LC-OCD Analysis 269 7.7.5 Suggested Mechanisms 270

8.3.1 Rejection of Organics and Cations

8.3.2 Rejection Mechanisms

8.4.1 Organics and Calcium 285 8.4.2 Colloidal Systems 287

8.5.1 Effect on Rejection

8.5.2 Effect on Flux

8.6.1 Dependence of Product Quality on Organic Type and Solution Chemistry 29 1 8.6.2 Water Quality 291

8.7.1 Membrane Cost

8.7.2 Membrane Requirements

8.7.3 Water Quality and Membrane Cost

8.7.4 Effect of Ferric Chloride Pretreatment

8.8.1 Energy Requirements 298 8.8.2 Chemicals Addition 298 8.8.3 Concentrate Disposal 299 8.8.4 Health Aspects 300 8.8.5 Treatment Considerations 301

Contents XV

Chapter 9 - S.ummay ei Concl.sion

Chapter 10 - F.urtber Research

Appendix 1 - Concentration ofNaturaI Organic Matter

XI 1.1 Conventional hlethods

A l 1.2 Concentration Using Membranes

X1 l 3 Comparison of Membrane and Adsorption Concentrates

A l 1.4 Method Selection

A1.2.1 Choice of Location 316 A1.2.2 Kaw \X7ater Characteris tics 317

A1.3.1 Microfiltration and Reverse Osmosis Equipment

X1.3.2 Membrane Process Operation

A1.4.5 Cation Analysis 326 X1.4.6 Overall Rejection 327 X1.4.7 MF Backwash Efficiency 329 A1.4.8 Membrane Cleaning and Storage 329 X1.4.9 Mass Balance 329

Appendix 2 - FiItration System Characterisation 333

A2.1.1 Perspes Stirred Cell

A2.1.2 Stainless Steel Stirred Cell

A2.3 SHEAR I N A CYLINDRICAL CHAMBER STIRRED BY A RADIAL

A2.3.1 General Description of Flow

A2.3.2 Theoretical Analysis for Shear Predction in Stirred Cell

A2.3.3 Implications of Shear on Agglomerates in Solution

xvi Contents

Appendix 3 - Hematite Pqbarution (C-F~~Q,) 4 1

Appendix 4 - Inshlnment Ca&ation 34 7

'14 l 6 Errors and Interferences

,142.1 hiethod

-14.22 ,ibsorbance Characteristics of NOhf

A4.2.3 Errors and Interferences

Appendix 5 - Sohtion Speciation Using MinteqA2

A 5 2 1 livailability of Sofhvare and Data Input 358

,-\5.3.1 pH Calculations as a Function of Partial CO2 Pressure 359 X5.3.2 Solution Speciation 360 A5.3.3 Calcium Precipitation 361 ii5.3.4 Speciation of Systems Containing Organics 363 ,15.3.5 Comments on the Membrane Boundary Layer Concentrations 364

Glossary & Symbols

References

FOREWORD

Membrane technology is rapidly becoming the preferred method for water treatment The past decade has seen an exponential growth in the number of membrane- based plants in operation and this growth seems unabated The reasons for this are many including the recognition that membranes can provide a more complete barrier to pathogens, that the product water quality is less dependent on the feed quality and that membrane plant are compact with modest energy demand At the same time we have seen a dramatic reduction in the cost of membranes making them economically competitive with traditional processes

This book, by Andrea Schafer, deals with the other important requirement in water treatment, the removal of natural organic matter (NOM) For many water sources NOM is a problem and must be removed to avoid the formation of trihalomethanes, by-products in the dsinfection process The Water Industry, wishing to use membranes, has a choice of options for NOM removal This book provides valuable input to that choice For applications with moderate to high NOM the choice could be Nanofiltration and for low or intermittent NOM the choice could be Micro- or Ultrafiltration with chemical coagulant as required However the optimal choice remains a moot point, driven by costs and operational issues

Having interests in the application of membranes and in physico-chemical aspects of water treatment

we have been fortunate to work with and support Andrea Schafer in her journey into the complex world of NOM and membrane treatment The literature on both topics is very large and growing This book is comprehensive in its coverage of other work However few texts have tackled the combined topics in such detail as this Importantly this text provides a detailed and meaningful comparison between the membrane options

In this study each membrane is fully characterised using a range of techniques, and then subjected to a well-defined protocol The author has used a wide range of feed materials, includng the international 'standards' as well as a preserved sample from a local water source Real 'raw water' includes NOM, colloids and cations in varylng amounts and the author provides an in depth study of the interaction of these species with the different types of membrane, from microporous MF to nanoporous NF Factors such as membrane and species charge, floc properties and the effect of coagulants are discussed The final chapter of this text brings together the issues of performance of the range of membranes and provides a comparison based on treated water quality and estimated treatment costs

This book is very timely and provides a mine of information for the reader We are sure you will find the journey a rewardmg one

Professor Tony Fane Director UNESCO Centre for Membrane Science and Technology, Australia Professor David LVaite Director Centre for Water and Waste Technology,

University of New South Wales, Sydney, Australia

PREFACE

This book represents a comprehensive manual for scientists and engineers involved in water treatment where natural organics, often referred t o as color, are of concern The work explains the three pressure-driven membrane processes of choice: microfiltration, ultrafiltration, and nanofiltration, with the objective of producing and recording comparable results for each process, so as to be able to conclude which process is most suitable under specified conditions

As a prerequisite, a detailed account of natural organics is provided, including the characteristics

of the "organic color" of waters that can result in the formation of potentially carcinogenic chlorination by-products

Initially prepared as a doctoral dissertation, the current work was requested by researchers worldwide for it scope of investigation and original data, which led to its publication as a monograph After an extensive literature review of both natural organics and their fate in the environment (Chapter 2) and a presentation of membrane filtration principles applicable to water treatment (Chapter 3), a detailed description is provided of experimental particulars

designed to permit the application of results t o other studies (Chapter 4) In this chapter, stress is placed on colloid-organic interactions, which are often overlooked in water treatment The study used stirred cell equipment, polymeric membranes, and synthetic surface water containing natural organics, inorganic colloids, and cations

The subsequent three chapters show the retention results of microfiltration, ultrafiltration and nanofiltration, respectively, with all processes being capable of removing a significant amount of natural organics Pretreatment with ferric chloride was required to achieve significant organic removal with MF and high MWCO UF Fouling mechanism investigations demonstrated that the crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics Mechanisms were dependent on the pore to solute-size ratio and varied from pore plugging by particles in MF, pore adsorption of calcium-organic complexes in UF, to precipitation of a calcium-organic complex in

NF Thorough chemical characterization of the organics used demonstrated that only size and aromaticity can be related to fouling

As a conclusion the book compares processes (Chapter 8) based on water quality parameters and cost It is shown that the cost of microfiltration with chemical pretreatment is similar to that of nanofiltration for comparable natural organics rejections