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Domestic Wastewater Treatment inDeveloping Countries

Domestic Wastewater Treatment inDeveloping CountriesDuncan MaraLondon Sterling, VA

First published by Earthscan in the UK and USA in 2004Copyright Duncan Mara, 2003All rights reservedISBN: 1-84407-019-0 paperback1-84407-020-4 hardbackTypesetting by MapSet Ltd, Gateshead, UKPrinted and bound in the UK by Cromwell Press, TrowbridgeCover design by Danny GillespieFor a full list of publications please contact:Earthscan8–12 Camden High Street, London, NW1 0JH, UKTel: 44 (0)20 7387 8558Fax: 44 (0)20 7387 8998Email: earthinfo@earthscan.co.ukWeb: www.earthscan.co.uk22883 Quicksilver Drive, Sterling, VA 20166-2012, USAEarthscan publishes in association with WWF-UK and the International Institute forEnvironment and DevelopmentA catalogue record for this book is available from the British LibraryLibrary of Congress Cataloging-in-Publication DataMara, D. Duncan (David Duncan), 1944Domestic wastewater treatment in developing countries / Duncan Mara.p. cm.Includes bibliographical references and index.ISBN 1-84407-020-4 (alk. paper) – ISBN 1-84407-019-0 (pbk. : alk. paper)1. Sewage disposal–Developing countries. 2. Sewage--Purification–Developingcountries. I. Title.TD627.M37 2004628.3'09172'4–dc2003023959This book is printed on elemental chlorine free paper

ContentsList of Figures and TablesPrefacePrincipal NotationList of Acronyms and Abbreviationsixxiiixvxvii1What is Domestic Wastewater and Why Treat It?Origin and composition of domestic wastewaterCharacterization of domestic wastewaterWastewater collectionWhy treat wastewater?Investment in wastewater treatment1125562Excreta-related DiseasesEnvironmental classification of excreta-related diseasesGlobal burden of excreta-related diseases88183Essential Microbiology and BiologyIntroductionVirusesBacteria and ArchaeaProtozoaAlgaeHelminthsFreshwater micro-invertebrates20202224353737384Effluent QualityWastewater treatment objectivesWastewater re-useDischarge to inland watersDischarge to coastal watersBATNEEC or CATNAP?4141424352545BOD Removal KineticsFirst-order kineticsHydraulic flow regimesLimitations of simple first-order kineticsWorked examples5656606467

vi Domestic Wastewater Treatment in Developing Countries6Domestic Wastewater Treatment OptionsSustainability issuesAppropriate wastewater treatment optionsSustainable wastewater treatment options696971727Domestic Wastewater Flows and LoadsDomestic wastewater flowsDomestic wastewater loadsFuture projections747477778Preliminary TreatmentPurposeScreeningGrit removalFlow measurement78787881849Waste Stabilization PondsTypes and functions of WSPAdvantages of WSPPerceived disadvantages of WSPWSP usageHigh altitude WSPWSP or other treatment processes?Macrophyte pondsAdvanced pond systems858589939410010010110210Anaerobic PondsFunctionDesignHigh-rate anaerobic pondsAnaerobic ponds in seriesDesign example10510510811011011211Facultative PondsFunctionDesignAlgal biomassPurple pondsWind-powered pond mixersDesign examples11411411812513013213212Maturation PondsFunctionPathogen removal mechanismsDesign for E coli removalDesign for helminth egg removal136136137141148

Contents viiBOD removalNutrient removalPond effluent polishingDesign example14814915115213Physical Design of WSPPond locationGeotechnical considerationsPond liningPond geometryInlet and outlet structuresBy-pass pipeworkAnaerobic pond coversTreebeltSecurityOperator facilitiesUpgrading and extending existing WSP15815815816216316616916917117217317314Operation and Maintenance of WSPStart-up proceduresRoutine maintenanceDesludging and sludge disposalStaffing levelsPond rehabilitation17517517517617918015Monitoring and Evaluation of WSPEffluent quality monitoringEvaluation of pond performanceData storage and analysis18218218318616Wastewater Storage and Treatment ReservoirsSingle reservoirsSequential batch-fed reservoirsHybrid WSP–WSTR systemDesign examples18818818919019017Constructed WetlandsSubsurface-flow wetlandsWetlands or waste stabilization ponds?19419419818Upflow Anaerobic Sludge Blanket ReactorsTreatment principlesDesignUASBs or anaerobic ponds?200200202206

viii Domestic Wastewater Treatment in Developing Countries19BiofiltrationFunctionDesignFly controlDesign example20720720721121220Simple Activated Sludge VariantsAerated lagoonsOxidation ditches21321322521Wastewater Re-use in AgricultureWhy re-use wastewater?Public health protectionCrop healthTreatment options for re-useQuantitative microbial risk analysisIrrigation with untreated wastewater23023023224224524625122Wastewater Re-use in AquacultureWhat is aquaculture?Wastewater-fed aquacultureWastewater-fed fishpond designIntegrated agricultural–aquacultural re-useDesign example253253256257259260ReferencesIndex262289

List of Figures and TablesFIGURES1.12.13.13.23.33.4Composition of Domestic Wastewater3Four-year old African girl with a Distended Abdomen15The Tree of Life23Common Bacterial Shapes25The Bacterial Batch-culture Growth Curve27The Catabolic, Anabolic and Autolytic Reactions of AerobicMicrobiological Oxidation293.5 Five of the Commonest Ciliated Protozoa in WastewaterTreatment Works363.6 Micro-invertebrates Used to Assess the Biological Quality ofTropical Waters394.1 The Dissolved Oxygen Sag Curve444.2 Discharge of an Effluent into a River505.1 Generalized BOD Curves575.2 Thirumurthi Chart for the Wehner–Wilhelm Equation625.3 Typical Tracer Study Results637.1 Diurnal Variation of Wastewater Flow and Load at Nakuru,Kenya768.1 Simple Manually Raked Screen798.2 Mechanically Raked Screen808.3 Flow Elements in a Parabolic Channel828.4 Trapezoidal Approximation to a Parabolic Section839.1 One of the Phase II 21-ha Primary Facultative Ponds at Dandora,Nairobi, Kenya859.2 Algal–bacterial Mutualism in Facultative and Maturation Ponds869.3 Typical WSP Layout879.4 Variation of Discount Rate and Land Price below which WSPare the Cheapest Treatment Option919.5 The Phase I WSP at Dandora, Nairobi, Kenya959.6 The ‘55 East’ WSP Series at Werribee, Melbourne, Australia979.7 The Mangere WSP, Auckland, New Zealand, in 19969910.1 Anaerobic Pond, with Partial Scum Coverage, at Ginebra,Valle del Cauca, Southwest Colombia10610.2 Variation of the Proportions of Hydrogen Sulphide, Bisulphideand Sulphide with pH in Aqueous Solutions107

x Domestic Wastewater Treatment in Developing Countries10.3 High-rate Anaerobic Pond with a Mixing Pit11.1 Diurnal Variation of Dissolved Oxygen in a Facultative Pond11.2 Variation of Surface BOD Loading on Facultative Ponds withTemperature According to Equations 11.2 and 11.311.3 Diurnal Variation in Facultative Pond Effluent Quality11.4 Variation of Chlorophyll a with Surface BOD Loading onPrimary Facultative Ponds in Northeast Brazil11.5 Photosynthetic Purple Sulphur Bacteria12.1 Variation of kB with Surface BOD Loading on PrimaryFacultative Ponds in Northeast Brazil12.2 Variation of kB with In-pond Chlorophyll a Concentration inPrimary Facultative Ponds in Northeast Brazil13.1 Embankment Protection by Concrete Cast in situ13.2 Embankment Protection by Precast Concrete Slabs13.3 Embankment Protection by Stone Rip-rap13.4 Anaerobic Pond Lined with an Impermeable Plastic Membrane13.5 Anchoring the Pond Liner at the Top of the Embankment13.6 Calculation of Top and Bottom Pond Dimensions13.7 Inlet Structure for Anaerobic and Primary Facultative Ponds13.8 Inlet Structure on a Facultative Pond with Integral Scum Box13.9 Inlet Structure for Secondary Facultative and Maturation Ponds13.10 Outlet Weir Structure13.11 By-pass Pipework for Anaerobic Ponds13.12 Covered Anaerobic Pond at the Western Treatment Plant,Melbourne, Australia13.13 Partial View of the Al Samra WSP, Amman, Jordan13.14 Fence and Warning Notice in English and Kiswahili at a PondSite in Nairobi, Kenya13.15 Upgrading a WSP Series to Treat Twice the Original Flow14.1 Sludge Depth Measurement by the ‘White Towel’ Test14.2 Pond Desludging in Northern France14.3 A Very Badly Neglected Facultative Pond in Eastern Africa15.1 Details of Pond Column Sampler16.1 Single WSTR in Israel16.2 Wastewater Storage and Treatment Reservoir Systems16.3 Sequential Batch-fed WSTR at Arad, Israel17.1 A 100-m Long Subsurface-flow Constructed Wetland in Egypt17.2 A Horizontal-flow Constructed Wetland at a Hotel in Kandy,Sri Lanka18.1 A UASB at Ginebra, Valle del Cauca, Southwest Colombia18.2 Schematic Diagram of a UASB18.3 Influent Distribution Channel and Distribution Boxes18.4 Details of a Submerged Phase Separator19.1 Sectional Perspective View of a Circular Biofilter19.2 Distribution of Settled Wastewater on to a Rectangular 95197201202203205208209

List of Figures and Tables xi19.3 Rectangular Biofilters with High-density Polyethylene Netting toControl Fly Nuisance20.1 An Aerated Lagoon20.2 Floating ‘Aire-O2 Triton’ Aerator–mixer20.3 Typical Oxidation Ditch Installation21.1 Excess Prevalence of Ascaris and Hookworm Infections inSewage Farm Workers in India21.2 Excess Intensity of Ascaris and Hookworm Infections in SewageFarm Workers in India21.3 Ascaris Prevalence among Residents of Western Jerusalem,1935–198221.4 Ascaris Prevalence among Residents of Selected German CitiesImmediately After the Second World War21.5 Generalized Model Showing the Levels of Relative Risk toHuman Health Associated with Different Combinations ofControl Methods for the Use of Wastewater in Agriculture andAquaculture21.6 Drip Irrigation of Cotton with Maturation Pond Effluent atNicosia, Cyprus21.7 Classification of Irrigation Waters Based on Conductivity andSodium Absorption Ratio22.1 Some of the Kolkata East Wastewater-fed Fishponds22.2 Harvesting Indian Major Carp from the Kolkata EastWastewater-fed n of Human Faeces and UrineWastewater Strength in Terms of BOD5 and CODAverage BOD5 Contributions per Person per DayEnvironmental Classification of Excreta-related DiseasesMajor Excreta-related Pathogens Identified Since 1973Global Diarrhoeal Disease and Geohelminthiases Statistics for1990Micro-invertebrate Groups Used to Assess the Biological Qualityof Tropical WatersSimplified Biotic Index for Tropical WatersNormalized Unit Values for Dissolved Oxygen, Total DissolvedSalt and Turbidity Used to Calculate WQIminThe UK Royal Commission’s Classification of River WaterQualityThe UK Royal Commission’s Standards for Wastewater EffluentsDischarged into RiversEffluent Quality Requirements for Domestic WastewatersDischarged into the Marine Environment of the Wider CaribbeanRegion24591718404049505154

xii Domestic Wastewater Treatment in Developing 522.1BOD Removal Results in Primary Facultative Ponds in NortheastBrazilComparison of Factors of Importance in Wastewater Treatmentin Industrialized and Developing CountriesCosts and Land Area Requirements for WSP and OtherTreatment ProcessesExcreted Pathogen Removals in WSP and ConventionalTreatment ProcessesDesign Values of Volumetric BOD Loadings on and PercentageBOD Removals in Anaerobic Ponds at Various TemperaturesVariation of BOD Removal with BOD Loading and RetentionTime in Anaerobic Ponds in Northeast Brazil at 25ºCExamples of Algal Genera Found in Facultative and MaturationPondsPerformance of a Series of Five WSP in Northeast BrazilBacterial and Viral Removals in a Series of Five WSP inNortheast BrazilSettling Velocities for Parasite Eggs and CystsHelminth Egg Removal in Waste Stabilization Ponds inNortheast BrazilReported Values of kB(20) and φ for Use in Equation 12.2Performance Data for WSP with Different Depths and Length-toBreadth Ratios in Northeast Brazil at 25ºCRecommended Staffing Levels for WSP SystemsParameters to be Determined for Level 2 Pond Effluent QualityMonitoringParameters to be Determined for the Minimum Evaluation ofWSP PerformanceOperational Strategy for Three Sequential Batch-fed WSTR foran Irrigation Season of Six MonthsSolubility of Oxygen in Distilled Water at Sea Level at VariousTemperaturesDesign Criteria for Oxidation Ditches in India and EuropeCrop Yields for Wastewater and Freshwater Irrigation in IndiaRecommended Maximum Concentrations of Boron in IrrigationWaters According to Crop ToleranceRecommended Maximum Metal Concentrations in IrrigationWatersPhysicochemical Quality of Three Waste Stabilization PondEffluents in IsraelValues of N50 and α for Excreted Viral and Bacterial PathogensPercentage of Free Ammonia (NH3) in Aqueous Ammonia(NH3 NH4) Solutions at 1–25 C and pH 185191219227230245246247249259

PrefaceThis book is primarily written for final year undergraduate civil engineeringstudents in developing country universities, for post-graduate masters studentsin environmental, public health and sanitary engineering, and for practisingengineers working in developing countries or working on wastewatertreatment projects in these countries. The primary emphasis of the book is onlow-cost, high-performance, sustainable domestic wastewater treatmentsystems. Most of the systems described are ‘natural’ systems – so called becausethey do not require any electromechanical power input. The secondaryemphasis is on wastewater re-use in agriculture and aquaculture – after all, itis better to use the treated wastewater productively and therefore profitably,rather than simply discharge it into a river and thus waste its water and itsnutrients. The human health aspects of wastewater use are obviouslyimportant and these are covered in detail, including an introduction toquantitative microbial risk analysis.Over the last 30 or so years that I have been working on wastewaterengineering in developing countries, I have been helped by many colleaguesand friends. I particularly wish to express my gratitude to all of the following:Professor Richard Feachem (University of California San Francisco andBerkeley), Dr Mike McGarry (Cowater International, Ottawa), EmeritusProfessor Gerrit Marais (University of Cape Town), Professor Howard Pearson(Universidade Federal do Rio Grande do Norte), Emeritus Professor HillelShuval (Hebrew University of Jerusalem), Professor Sandy Cairncross and DrUrsula Blumenthal (London School of Hygiene and Tropical Medicine),Emeritus Professor Takashi Asano (University of California Davis), ProfessorMarcos von Sperling (Universidade Federal de Minas Gerais), Professor PeterEdwards (Asian Institute of Technology) and Dr Andy Shilton (MasseyUniversity); and at the University of Leeds: Emeritus Professor Tony Cusens,Emeritus Professor Donald Lee, Professor Ed Stentiford, Dr Nigel Horan andDr Andy Sleigh. Advice on the content of Figure 3.1 was generously providedby Dr Ian Head (University of Newcastle).Docendo dedici. Many of my former doctoral students have made majorcontributions, including Dr Rachel Ayres, Dr Harin Corea, Dr Tom Curtis, DrMartin Gambrill, Dr Steve Mills, Dr John Oragui, Dr Miguel Peña Varón,Professor Salomão Silva, Dr David Smallman, Dr Rebecca Stott and Dr HuwTaylor.

xiv Domestic Wastewater Treatment in Developing CountriesFinally, but most importantly, I wish to express a lifelong gratitude toKevin Newman, Emeritus Professor of Classics at the University of Illinois,who taught me as a teenager how to think – the greatest gift a teacher canbestow.

Principal �θκλµφareabreadthconcentrationdepth; dissolved oxygen deficitnumber of helminth eggsnet evaporationsoluble BODfirst-order rate constant for BOD removalfirst-order rate constant for surface reaerationfirst-order rate for E coli removalBOD; lengthmassflowinfectivity constantsolidstemperaturetimevolume; velocitycell concentrationyield coefficientoxygen consumedcoefficient of retardation; infectivity constant; ratio of oxygentransfer in wastewater and tap waterratio of oxygen solubility in wastewater and distilled watersludge loading factordispersion numberporosityretention timefirst-order rate constant for soluble BOD removalloading ratespecific growth rateArrhenius constant

xvi Domestic Wastewater Treatment in Developing entfacultativeinfluentmaturation, mean, mixtureriversurfacevolumetric

List of Acronyms and AbbreviationsAIPSAIWPS ced integrated pond systemadvanced integrated wastewater ponding systembest available technology not entailing excessive costbiochemical oxygen demandcheapest available technology narrowly avoiding prosecutioncarbonaceous BODchemical oxygen demanddissolved oxygenEuropean UnionFood and Agriculture Organizationfaecal coliformsgross algal oxygen productiongross dissolved oxygen productionhigh-rate algal pondsNational River Conservation Directorateoperation and maintenancephotosynthetically active radiationphotosynthetic photon flux densityquantitative microbial risk analysissolids retention timesuspended solidstheoretical oxygen demandupflow anaerobic sludge blanket reactor(s)United States Agency for International DevelopmentUnited States Environmental Protection AgencyWorld Health Organizationwaste stabilization pond(s)wastewater storage and treatment reservoir(s)

1What is Domestic Wastewater andWhy Treat It?ORIGIN AND COMPOSITION OF DOMESTIC WASTEWATERDomestic wastewater is the water that has been used by a community andwhich contains all the materials added to the water during its use. It is thuscomposed of human body wastes (faeces and urine) together with the waterused for flushing toilets, and sullage, which is the wastewater resulting frompersonal washing, laundry, food preparation and the cleaning of kitchenutensils.Fresh wastewater is a grey turbid liquid that has an earthy but inoffensiveodour. It contains large floating and suspended solids (such as faeces, rags,plastic containers, maize cobs), smaller suspended solids (such as partiallydisintegrated faeces, paper, vegetable peel) and very small solids in colloidal (ienon-settleable) suspension, as well as pollutants in true solution. It isobjectionable in appearance and hazardous in content, mainly because of thenumber of disease-causing (‘pathogenic’) organisms it contains (Chapter 2). Inwarm climates wastewater can soon lose its content of dissolved oxygen andso become ‘stale’ or ‘septic’. Septic wastewater has an offensive odour, usuallyof hydrogen sulphide.The composition of human faeces and urine is given in Table 1.1, and forwastewater, in simpler form, in Figure 1.1. The organic fraction of both iscomposed principally of proteins, carbohydrates and fats. These compounds,particularly the first two, form an excellent diet for bacteria, the microscopicorganisms whose voracious appetite for food is exploited by public healthengineers in the microbiological treatment of wastewater. In addition to thesechemical compounds, faeces and, to a lesser extent, urine contain manymillions of intestinal bacteria and smaller numbers of other organisms. Themajority of these are harmless – indeed some are beneficial – but an importantminority is able to cause human disease (Chapter 2).Sullage contributes a wide variety of chemicals: detergents, soaps, fats andgreases of various kinds, pesticides, anything in fact that goes down the kitchensink, and this may include such diverse items as sour milk, vegetable peelings,tea leaves, soil particles (arising from the preparation of vegetables) and sand

2 Domestic Wastewater Treatment in Developing CountriesTable 1.1 Composition of Human Faeces and UrineQuantitiesQuantity (wet) per person per dayQuantity (dry solids) per person per dayApproximate composition (%)MoistureOrganic matterNitrogenPhosphorus (as P2O5)Potassium (as K2O)CarbonCalcium (as CaO)FaecesUrine1

Principal Notation xv List of Acronyms and Abbreviations xvii 1 What is Domestic Wastewater and Why Treat It? 1 Origin and composition of domestic wastewater 1 Characterization of domestic wastewater 2 Wastewater collection 5 Why treat wastewater? 5 Investment in wastewater treatment 6 2 Excreta-related Diseases 8

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