Flocculation In Natural And Engineered Environmental Systems - Chapter 1 pot

It is now well established that the majority of particles within natural freshwater and saltwater systems are present in a culated form i.e., flocs, and that the formation of flocs is es

FLOCCULATION in NATURAL and ENGINEERED ENVIRONMENTAL SYSTEMS

CRC PR E S S

Boca Raton London New York Washington, D.C

FLOCCULATION in NATURAL and ENGINEERED ENVIRONMENTAL SYSTEMS

Edited by Ian G Droppo • Gary G Leppard Steven N Liss • Timothy G Milligan

Library of Congress Cataloging-in-Publication Data

Flocculation in natural and engineered environmental systems/edited by Ian G Droppo [et al.].

p cm.

Includes bibliographical references and index.

ISBN 1-56670-615-7 (alk paper)

1 Flocculation 2 Water—Purification I Droppo, Ian G.

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2004056933

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In the history of environmental science, there has probably been no greater strugglethan the attempt to control the impact of the sediment and solids generated by natureand human influence (including industrial processing) on the terrestrial and aquaticenvironment and on socioeconomics in general Untold billions of dollars are spenteach year on dredging to maintain navigation channels and harbors Further costs areadded by the need to treat these sediments prior to disposal because of high levels ofcontamination resulting from anthropogenic impacts on the environment Significantfinancial burdens arise as a result of the need to remove solids during drinking waterand wastewater treatment processes, a necessity for sustainable development, and theprotection of human and aquatic health It is now well established that the majority

of particles within natural (freshwater and saltwater) systems are present in a culated form (i.e., flocs), and that the formation of flocs is essential for the effectiveperformance of engineering processes such as biological wastewater treatment.Flocculation is the process of aggregating smaller particles together to form lar-ger composite particles via various physical, chemical, and biological interactions.These larger composite particles behave differently in terms of their physical (e.g.,transport, settling), chemical (e.g., contaminant uptake and transformation), and bio-logical (e.g., community structure activities and metabolism) behavior relative totheir constituent individual particles due to differences in size, shape, porosity, dens-ity, and compositional characteristics Given these significant behavioral differencesbetween flocs per se and their individual component parts, flocculation influences awide array of environmental phenomena related to sediment–water and sediment–sediment interactions A few of these include sediment and contaminant transport invarious aquatic ecosystems, remediation of contaminated bed sediments, contamin-ated bed sediment stability, and habitat destruction resulting from sedimentation (e.g.,coral reef, salmon spawning grounds, mollusk habitat degradation) These concerns,coupled with the ubiquitous nature of flocs within natural and engineered systemsand the potential to influence floc properties to control better the environmental andengineering processes, have generated an increased emphasis on floc research.The traditional disciplines within saltwater, freshwater, and engineering researchhave, however, remained somewhat mutually exclusive in their approach to the study

floc-of flocculation processes This reality is facilitated by differences in external ables (e.g., environmental conditions), focus driven research, and discipline bias.Regardless of differences in discipline or approach, there is great scope and utility forthe sharing of information between scientists who work in these three floc environ-ments Often methods used in one environment can, and should, be used in another

vari-to further our understanding of flocculation processes While new developments in

v

vi Preface

genomics, nanotechnology, sampling, and modeling permit increasingly revealinginvestigations into floc structure, processes, and impact, there is still a fundamentallack of knowledge related to many aspects of the flocculation process

In light of the importance of flocculation within natural and engineered systems,

an international workshop was held on September 4 and 5, 2003, at the CanadaCentre for Inland Waters, Burlington, Ontario, Canada The workshop broughttogether academics and government scientists from around the globe to address thecritical issue of sediment flocculation within freshwater, saltwater, and engineeredsystems During the workshop, participants representing these three environmentspresented their research findings Three focus areas were used to structure theworkshop: (a) modeling, (b) physicochemical, and (c) biological aspects of floc-culation Following individual presentations, the participants were divided up intothree working groups to address assigned topics in the focus areas Each focus groupcontained researchers from the freshwater, saltwater, and engineered systems toensure a cross-communication of ideas between environments and to facilitate anunderstanding of the unifying principles of flocculation Participants ranged fromgeographers/geomorphologists who investigate flocculation as it relates to sedimentsource, transport, and fate within river systems, sedimentologists interested in floc-culation’s influence within depositional environments, biologists focusing on thebiopolymeric matrices and microbial consortia of flocs, oceanographers investig-ating sediment transport and delivery within estuaries and open ocean environments,and wastewater engineers/biologists interested in floc behavior within engineeredsystems

The peer-reviewed 20 chapters that comprise this text are organized by their onment of investigation The final chapter identifies the unifying principles that werediscussed within the workshop focus groups and from the preceding chapters Thetext provides a unique perspective in that it integrates the natural sciences and engin-eering fields as they relate to the central phenomenon of flocculation We hope thatthe array of information provided in this book will be valuable to all those interested

envir-in flocculation issues withenvir-in any environment

Ian G DroppoGary G LeppardSteven N LissTimothy G Milligan

The workshop and this resultant text would not have been made possible withoutthe generous support of our sponsors We would like to thank the National WaterResearch Institute of Environment Canada, the Department of Fisheries and Oceans,the Wastewater Technology Centre of Environment Canada, the Brockhouse Institutefor Materials Research of McMaster University, Ryerson University, and the Inter-national Association for Sediment Water Science for their support The editors areparticularly grateful to the Natural Sciences and Engineering Research Council ofCanada for their funding support related to research on flocculation

Each chapter has been peer reviewed by two or three reviewers consistent withthe standards set for international scientific journals We would like to thank thesereviewers for their efforts in this regard

Finally, we would like to thank the National Water Research Institute of onment Canada for hosting the workshop and John Lawrence, Michel Beland, andJohn Preston for their support The efforts of Elizabeth Wendel, Meenu Pall, DianneCrabtree, Allana Manto, Quintin Rochfort, Christina Jaskot, and Brian Trapp ofEnvironment Canada leading up to, during, and following the workshop are gratefullyacknowledged

Envir-About the Editors

Ian G Droppo is a research scientist with the

National Water Research Institute of EnvironmentCanada and is the current elected vice president ofthe International Association for Sediment WaterScience Dr Droppo holds adjunct professorships

at McMaster University, School of Geography andEarth Sciences and at the State University of NewYork, College at Buffalo, Department of Geographyand Planning He holds undergraduate and M.Sc.degrees in physical geography from McMaster Uni-versity, Canada and a Ph.D in physical geographyfrom the University of Exeter, United Kingdom Hewas a recent recipient of Leverhulme InternationalVisiting Fellowship held at the University of Exeter in the United Kingdom Dr.Droppo’s research interests center around sediment dynamics within natural andengineered systems with particular emphasis on flocculation processes He has appliedthis knowledge in multiple environments including urban stormwater management,remediation of contaminated bed sediments, contaminated bed sediment stability,and in the source, fate, and effect of sediments and associated contaminants withinnumerous aquatic environments His research is supported by awards from Environ-ment Canada, the Natural Sciences and Engineering Research Council of Canada,and a range of industrial partners He has given many invited lectures and seminars atinternational conferences, workshops, and universities and has taught many sedimentchemistry monitoring courses in developing countries Dr Droppo has carried outcollaborative research in Canada, United States of America, United Kingdom, Japan,Mexico, Australia and Thailand leading to over 85 peer-reviewed journal publications,book chapters, and technical reports

x About the Editors

Gary G Leppard is an environmental biochemist and microbiologist who studies

the roles of natural and engineered aquatic aggregates (flocs, biofilms) in the transportand fate of contaminants In concert with these activities, he develops electron-opticalmeans to analyze the colloidal structure of natural dispersing agents and the flocs ofwater treatment tanks He joined the staff of the National Water Research Institute ofEnvironment Canada at Burlington (ON) in 1975, as a research scientist While alsoholding a professorship at McMaster University and membership in the BrockhouseInstitute for Materials Research (Hamilton, ON), he is a Fellow of the InternationalUnion of Pure and Applied Chemistry and a Consulting Fellow of the World Innov-ation Foundation In sequence, he was an invited scientist at the University of Paris

(France), the University of Milan (Italy), Laval versity (Quebec City), the National Research Coun-cil of Canada (Ottawa), the University of Geneva(Switzerland), the University of Vienna (Austria),and the Rudjer Boskovic Institute (Croatia)

Uni-Dr Leppard received degrees in several fields

of biology and biological chemistry from the versity of Saskatchewan (Saskatoon, SK) and fromYale University (New Haven, CT, United States)

Uni-A Ph.D in cell biology, with a specialization inelectron-optical methods, was received from Yale in

1968 Research interests then extended into chemistry, wastewater treatment, materials science,and the activities of natural microbial consortia Hisinterdisciplinary research has led to awards from theNorth Atlantic Treaty Organization, the Commis-sion of the European Communities, and the RITEinnovative technology organization in Japan, as well as a role on the editorial board

biogeo-of the Encyclopedia biogeo-of Analytical Science Current scientific interests focus on thecontrol, by nanoscale phenomena, of macroscale effects in aquatic environments.These interests are coupled to the development of technology for commercial use,and include environmental projects for synchrotron laboratories

About the Editors xi

Steven N Liss is a professor of applied

microbio-logy in the Department of Chemistry and Biomicrobio-logy

at Ryerson University and is the Associate Dean(Research, Development and Science Programs)for the Faculty of Engineering and Applied Sci-ence Dr Liss holds adjunct professorships at theUniversity of Toronto in the Departments of Chem-ical Engineering and Applied Chemistry and CivilEngineering Dr Liss holds an undergraduate degree

in microbiology and immunology from the versity of Western Ontario (1980) and graduatedegrees in applied microbiology from the Univer-sity of Saskatchewan (M.Sc, 1983; Ph.D., 1987)

Uni-Dr Liss currently leads research projects on themicrobiology of wastewater treatment, water wells,and environmental biotechnology His research issupported by awards from the Natural Sciences and Engineering Research Council ofCanada, the National Centres of Excellence, Ontario Centres of Excellence, Environ-ment Canada, Canada Foundation for Innovation (CFI), and a wide range of industrypartners Specific research activities include microbial floc architecture in engineeredand natural systems, microbial ecology, water quality, filamentous microorganismsand bulking problems, biofouling and microbial-based tools for studying, and mon-itoring biological treatment systems including DNA microarrays His laboratory hasdeveloped expertise related to the physicochemical properties of microbial structures,their composition and structure, and the application of advanced optical microscopy

in studying microbial structures and physiology His research in wastewater biology led to the Ryerson Distinguished Research Award in 1998 Dr Liss hassupervised 32 graduate students at the masters and Ph.D levels He is the author andco-author of over 100 peer-reviewed journal publications, book chapters, conferencepresentations, and technical reports

micro-xii About the Editors

Timothy G Milligan is a researcher with the

Mar-ine Environmental Sciences Division, Fisheries andOceans Canada As head of the Particle DynamicsLaboratory at the Bedford Institute of Oceanography

he leads the group’s research into the behavior offine particulate material in aquatic environments Hereceived his B.Sc in geology and M.Sc in ocean-ography from Dalhousie University and has beeninvolved with flocs for over 30 years While his ini-tial contact was in pulp mill effluent, it was the timespent with the late Dr Kate Kranck, a pioneer inflocculation studies in the marine environment, thatgave him his love of mud Areas of interest includethe mechanisms governing the loss of sediment fromriver plumes, the effect of flocculation on the trans-port and fate of contaminants, and environmentalimpacts of offshore oil and gas and aquaculture Mr.Milligan has led research projects in a wide range of geographical areas, from theAmazon to the Canadian Arctic While his work concentrates mainly on the marineenvironment, the fate of terrestrially derived sediments and associated contaminantshas led him into the study of fluvial transport as well Mr Milligan has been involved

in many international ventures, several of which have received funding from the U.S

Office of Naval Research His work combines in situ techniques with process-based

parameterization of the size distributions of the component grains in suspended andbottom sediment to better understand the fate of mud in both marine and freshwatersystems Over 80 peer-reviewed primary publications, book chapters, and technicalreports have been produced from this work

D Grant Allen

Department of Chemical Engineering

and Applied Chemistry

Pulp & Paper Centre

State University at Buffalo

Buffalo, New York, U.S.A

State University at Buffalo

Buffalo, New York, U.S.A

Holger Daims

Department of Microbial Ecology

Institute for Ecology and Conservation

Horn Point Laboratory

Cambridge, Maryland, U.S.A

Carl T Friedrichs

Virginia Institute of Marine ScienceCollege of William and MaryGloucester Point, Virginia, U.S.A

David D Fugate

Virginia Institute of Marine ScienceCollege of William and MaryGloucester Point, Virginia, U.S.A

Jean-Francois Gaillard

Department of Civil and EnvironmentalEngineering

Northwestern UniversityEvanston, Illinois, U.S.A

Gill G Geesey

Department of MicrobiologyMontana State UniversityBozeman, Montana, U.S.A

Adam P Hitchcock

Brockhouse Institute for MaterialsResearch

McMaster UniversityHamilton, Ontario, Canada

xiv Contributors

George A Jackson

Department of Oceanography

Texas A&M University

College Station, Texas, U.S.A

Department of Chemistry and Biology

Faculty of Engineering and Applied

COE Environmental Institute

The Pennsylvania State University

University Park, Pennsylvania

John M Phillips

Environment AgencyBlandford ForumDorset, U.K

Alain Reinhardt

Analytical and BiophysicalEnvironmental ChemistryUniversity of GenevaGeneva, Switzerland

Heidi Romine

Virginia Institute of Marine ScienceCollege of William and MaryGloucester Point, Virginia, U.S.A

Texas A&M University

Galveston, Texas, U.S.A

Steven E Suttles

University of Maryland Center for

Environmental Science

Horn Point Laboratory

Cambridge, Maryland, U.S.A

Laurenz Thomsen

School of Engineering and Science

International University Bremen

Bremen, Germany

John E VanBenschoten

Department of Civil, Structural and

Environmental Engineering

State University of New York at Buffalo

Buffalo, New York, U.S.A

Fintan Van Ommen Kloeke

Department of MicrobiologyMontana State UniversityBozeman, Montana, U.S.A

Desmond E Walling

Department of GeographyUniversity of ExeterExeter, Devon, U.K

Kevin J Wilkinson

Analytical and BiophysicalEnvironmental ChemistryUniversity of GenevaGeneva, Switzerland

Johan C Winterwerp

W.L Delft HydraulicsDelft, The Netherlands

Chapter 1 Methods for Analyzing Floc Properties 1

Steven N Liss, Timothy G Milligan, Ian G Droppo, and Gary G Leppard

Chapter 2 Overview of Flocculation Processes in Freshwater Ecosystems 25

Gary G Leppard and Ian G Droppo

Chapter 3 Intra-Storm and Seasonal Variations in the Effective Particle

Size Characteristics and Effective Particle Density of FluvialSuspended Sediment in the Exe Basin, Devon, United Kingdom 47

John M Phillips and Desmond E Walling

Chapter 4 The Composite Nature of Suspended and Gravel Stored Fine

Sediment in Streams: A Case Study of O’Ne-eil Creek,British Columbia, Canada 71

Ellen L Petticrew

Chapter 5 Effects of Floc Size and Shape in Particle Aggregation 95

Joseph F Atkinson, Rajat K Chakraborti, and John E VanBenschoten

Chapter 6 Mapping Biopolymer Distributions in Microbial Communities 121

John R Lawrence, Adam P Hitchcock, Gary G Leppard, and Thomas R Neu

Chapter 7 Contrasting Roles of Natural Organic Matter on Colloidal

Stabilization and Flocculation in Freshwaters 143

Kevin J Wilkinson and Alain Reinhardt

Chapter 8 An Example of Modeling Flocculation in a Freshwater

Aquatic System 171

Bommanna G Krishnappan and Jiri Marsalek

xviii Contents

Chapter 9 Transport of Materials and Chemicals by Nanoscale Colloids

and Micro- to Macro-Scale Flocs in Marine, Freshwater, andEngineered Systems 191

Peter H Santschi, Adrian B Burd, Jean-Francois Gaillard, and Anne A Lazarides

Chapter 10 Variability of Suspended Particle Concentrations, Sizes, and

Settling Velocities in the Chesapeake Bay Turbidity Maximum 211

Lawrence P Sanford, Patrick J Dickhudt, Laura Rubiano-Gomez, Marissa Yates, Steven E Suttles, Carl T Friedrichs, David D Fugate, and Heidi Romine

Chapter 11 Organic Rich Aggregates in the Ocean: Formation, Transport

Behavior, and Biochemical Composition 237

Chapter 14 Extracellular Enzymes Associated with Microbial Flocs

from Activated Sludge of Wastewater Treatment Systems 295

Gill G Geesey and Fintan Van Ommen Kloeke

Chapter 15 Molecular Analyses of Microbial Community Structure and

Function of Flocs 317

Holger Daims

Chapter 16 Using Atomic Force Microscopy to Study Factors

Affecting Bioadhesion at Molecular to Nanoscale Levels 339

Bruce E Logan

Chapter 17 Impact of Stresses or Transient Conditions on Deflocculation

in Engineered Microbial Systems 351

Fernando Morgan-Sagastume and D Grant Allen

Chapter 20 Opportunities, Needs, and Strategic Direction for

Research on Flocculation in Natural andEngineered Systems 407

Ian G Droppo, Gary G Leppard, Steven N Liss, and Timothy G Milligan

1 Methods for Analyzing

Floc Properties

Steven N Liss, Timothy G Milligan, Ian G Droppo, and Gary G Leppard

CONTENTS

1.1 Introduction 1

1.1.1 Floc Size 2

1.1.2 Sample Handling and Stabilization 4

1.2 Floc Settling Velocity 5

1.3 Floc Density and Porosity 7

1.3.1 Floc Structure: Correlative Microscopy 9

1.3.2 Extracellular Polymeric Substances 10

1.4 Surface Charge and Hydrophobicity 11

1.5 Microbial Ecology 13

1.6 Conclusion 14

References 14

1.1 INTRODUCTION

The function–structure relationships of flocs are important to environmental scientists, microbiologists, and engineers Ultimately, their goals include being able to solve practical problems more effectively, and to provide better information for modeling ecological processes and contaminant transport in aquatic environments and in the operation of engineered systems (e.g., wastewater and drinking water) Methods and analytical tools play a critical role in floc research and in achieving these goals These are intended to do one of two things: (i) to provide descriptive and quantitative information that may lead to a fuller understanding of flocculation and (ii) to have tools that may be applied to the management of floc processes in engineered and environmental systems

At present, few standard methods with good reproducibility are available, although several physical, chemical, and microbiological measurement and analyt-ical techniques have been developed Earlier reviews give a comprehensive review

of the methods and techniques for the measurement of physical characteristics for activated sludge1and an overview of the principles, methods, and applications of particle size analysis in primarily saltwater systems.2Eisma et al.3and Dyer et al.4

2 Flocculation in Natural and Engineered Environmental Systems

conducted a comparative study in the Elbe estuary to evaluate several different in situ

methods for determining floc size and settling velocity More recently, several entries

in the Encyclopaedia of Environmental Microbiology5provide overviews of methods,particularly advanced optical microscopy and molecular tools applied to the study ofmicrobial structures including flocs.6Common to all these reviews is the wide range

of methods employed to determine some of the most basic of parameters that describeflocs in the environment

In engineered systems, advances have been achieved primarily in studying flocproperties (ecology, structure, and physicochemical characteristics) of individual flocsfrom full-scale systems and from laboratory-scale reactors that were run under well-controlled conditions In contrast, studies in the marine and freshwater environmentshave concentrated on bulk properties such as gross morphology, size, and settling

velocity in samples collected with an emphasis on in situ measurements One reason

for the difference between measurements in the natural environment and engineeredsystems is the availability of flocs and the ease with which they can be sampledintact Those involved with studying natural systems have tended to focus on the grossproperties and behavior of floc Engineered systems are suited to detailed examination

of surface properties and molecular determinants in floc behavior

In this chapter, we present an overview of the principal methods presently beingused in engineered, freshwater, and marine systems Some aspects of the methodspresented can be applied to both natural and engineered systems Our goal is to provide

an insight into the work being carried out in the different aquatic environments so thatresearchers can consider adapting the techniques presented to their respective fields

1.1.1 FLOCSIZE

Floc size is a widely measured floc characteristic Floc size influences propertiessuch as mass transfer (transport and settling),7 biomass separation, and sludgedewatering.8–10 Flocs are generally observed as two-dimensional (2D) projections,and there is no simple means of specifying size or shape.11 However, flocs arehighly irregular in shape, porous, and three-dimensional Equivalent spherical dia-meter (ESD), frequently calculated from the two-dimensional area, is often used tocharacterize floc size due to its simplicity and its application in Stokes’ law.11–13Bache et al.11 defined the effective diameter as the geometric mean

(dmin ∗d

max)

based on the maximum(dmax) and minimum (dmin) dimensions across the 2D floc

image Barbusinski and Koscielniak14and Li and Ganczarczyk15described floc sizebased on the average floc diameter defined as one half of the sum of the longest andshortest dimensions of the flocs measured

Flocs in suspension are found over a range of sizes that describe a continuousdistribution Several standard parameters are available to describe floc size distribu-

tions Median (d50), upper quartile (d25), and mode have all been used to describethe size distribution of flocs in suspension.13,16,17Due to the open architecture andpoorly defined association of particles within a floc, researchers use fractal geometry

to describe floc structure.18−23 Depending on the nature and the sizing technique

employed, there is no evidence to show which definition is the best representation offloc size However, researchers should be clear in their definition of floc size whenreporting results

Methods for Analyzing Floc Properties 3

In general flocs range in size from a few microns to a few millimeters whenmeasured by ESD One exception is large assemblages of diatoms or other biologicallyderived material Sometimes referred to as marine snow to differentiate it from moreinorganic rich flocs, these patches of aggregated organic material can reach ESDsmany orders of magnitude larger than what could be considered normal flocs Whenmarine snow becomes buoyant during decomposition, as was observed in the AdriaticSea during the mucilage phenomenon, “floc size” can exceed 1 m.24−27

Many methods and instruments have been developed in the past to measure flocsize distributions in natural and engineered systems One of the earliest methods wasthe Coulter Counter, which determined the size distribution of particles in suspension.This method was popular in the marine environment as the electrolyte concentration

in seawater permitted samples to be analyzed without alteration However, stressesapplied during the counting process can disrupt flocs which raises the issue that thismethod may be of little value for estimating floc size.28,29

The determination of floc size has relied primarily on imaging of flocs followed byimage analysis to ascertain the parameters describing the size distribution.12,30,31Bothmicroscopic observations and photographic techniques13,32–35have been used In situ

photography of flocs, although relatively easy to employ, does not allow measurement

of very small flocs due to resolution limits Often these systems can only image downfrom 50 to 100 µm, although a 10 : 1 camera system with a resolution of 10 µm

has been developed.36,37Recent advances in digital photography should improve the

resolution of in situ camera systems The main advantage of these instruments is their

ability to measure floc size with minimal disturbance to the natural stress environment

of the flocs However, they were developed for the natural environment, and may bedifficult to apply in an engineered system as they are limited by the concentration ofparticles in suspension

Microscopic methods usually incorporate a camera and computerized digitizer

to provide images for analysis The increased resolution of microscopic systemsallows for accurate, reproducible, and relatively fast estimates of floc morpholo-gical parameters Specialized techniques such as confocal microscopy and electronmicroscopy (discussed in detail later in the chapter) allow the internal structure offlocs to be examined The obvious drawback for microscopic analysis is the require-ment to remove flocs from their natural environment and the associated instrumentcosts

Common to both photographic and microscopic methods is the requirement toconduct image processing and analysis on the captured image to determine floc sizeand other descriptive parameters Image processing and analysis comprises severalsteps.38Different algorithms are applied to the digital image to improve the quality

of the image and to separate a floc from its background Each area of coherent pixelswith values within a selected range of threshold values is then used to calculate thedifferent parameters used to describe floc size There are differing views on the number

of pixels required to define a particle with values ranging from 3 to 35 pixels.39,40Several different image analysis systems are available on the market but all are based

on the same principles for manipulating a matrix of pixel values Clear explanations