Water-Quality Engineering in Natural Systems

1 Introduction 1 1.1 Background . 1 1.2 Sources of Water Pollution . 3 1.2.1 Point Sources 3 1.2.1.1 Domestic wastewater discharges 3 1.2.1.2 Sanitary sewer over ows 4 1.2.1.3 Combined sewer over ows 4 1.2.1.4 Stormwater discharges 5 1.2.1.5 Industrial discharges . 5 1.2.1.6 Spills . 5 1.2.2 Nonpoint Sources 6 1.2.2.1 Agricultural runoff 6 1.2.2.2 Livestock . 7 1.2.2.3 Urban runoff . 7 1.2.2.4 Landlls . 8 1.2.2.5 Recreational activities 8 1.3 Control of Water Pollution 8 2 Water Quality 11 2.1 Introduction . 11 2.2 Physical Measures . 11 2.2.1 Flow Conditions 12 2.2.2 Substrate 14 2.2.3 In-Stream Habitat . 15 2.2.4 Riparian Habitat 16 2.2.5 Thermal Pollution . 17 2.3 Chemical Measures . 17 2.3.1 Dissolved Oxygen 18 2.3.2 Biochemical Oxygen Demand . 21 2.3.3 Suspended Solids 24 2.3.4 Nutrients 25 2.3.4.1 Nitrogen . 26 2.3.4.2 Phosphorus 28 2.3.5 Metals 29 2.3.6 Synthetic Organic Chemicals . 30 2.3.6.1 Pesticides . 30 2.3.6.2 Volatile organic compounds . 31 2.3.7 Radionuclides 31 2.3.8 pH 32 2.4 Biological Measures . 32 2.4.1 Human Pathogenic Microorganisms . 33 2.4.2 Indicator Organisms 39 2.4.3 Biological Integrity . 43 Problems . 44 3 Fundamentals of Fate and Transport 47 3.1 Introduction . 47 3.2 The Advection-Diffusion Equation 47 3.2.1 Nondimensional Form . 52 3.2.2 Transformations of the Diffusion Equation 54 3.2.2.1 Conservative tracers . 54 3.2.2.2 Non-conservative tracers with rst-order decay 55 3.2.3 Moment Property of the Diffusion Equation . 56 3.3 Fundamental Solutions of the Advection-Diffusion Equation 58 3.3.1 Advection and Diffusion in One Dimension . 58 3.3.1.1 Spatially and temporally distributed sources . 62 3.3.1.2 Impermeable boundaries 67 3.3.1.3 Continuous plane source 71 3.3.2 Advection and Diffusion in Two-Dimensions . 77 3.3.2.1 Spatially and temporally distributed sources . 78 3.3.2.2 Continuous line source in owing environment 79 3.3.2.3 Continuous plane sources 81 3.3.3 Advection and Diffusion in Three-Dimensions 84 3.3.3.1 Spatially and temporally distributed sources . 86 3.3.3.2 Plane source . 86 3.3.3.3 Instantaneous point source in shear ow 87 3.3.3.4 Continuous point source with constant diffusion coefficient . 89 3.3.3.5 Continuous point source with variable diffusion coefficient 94 3.3.3.6 Instantaneous line source 95 3.3.3.7 Instantaneous volume source 96 3.4 Advection and Diffusion of Heat . 97 3.5 Transport of Suspended Particles . 98 3.6 Fate and Transport of Microorganisms in Natural Waters . 101 3.7 Turbulent Diffusion . 102 3.7.1 Relationship of Turbulent Diffusion Coefficient to Velocity Field . 103 3.7.2 Eulerian Approximation 106 3.8 Dispersion 110 Problems . 116 4 Rivers and Streams 127 4.1 Introduction . 127 4.2 Transport Processes 130 4.2.1 Initial Mixing 130 4.2.2 Longitudinal Dispersion 138 4.2.2.1 Field measurement 139 4.2.2.2 Empirical estimates . 142 4.3 Models of Spills . 146 4.3.1 Substances with First-Order Decay 146 4.3.1.1 Instantaneous release 147 4.3.1.2 Continuous release 151 4.3.2 Spills of Volatile Organic Compounds 152 4.4 Models of Dissolved Oxygen 156 4.4.1 Oxygen Demand of Wastewater 157 4.4.2 Reaeration . 158 4.4.3 Streeter-Phelps Model . 162 4.4.4 Other Considerations . 168 4.4.4.1 Nitrification . 168 4.4.4.2 Photosynthesis, respiration, and benthic oxygen demand 175 4.4.4.3 Distributed sources of BOD . 179 4.4.5 Chapra-Di Toro Model . 182 4.4.6 Empirical Models 187 4.4.7 Numerical Models . 187 4.5 Models of Nutrients 187 4.6 Models of Pathogens 188 4.7 Contaminant Loads . 190 4.7.1 Total Maximum Daily Loads . 191 4.7.1.1 Derivation of the load duration curve . 191 4.7.1.2 Applications of the load duration curve 195 4.7.1.3 Other TMDL approaches 202 4.7.2 Long-Term Contaminant Loads 203 4.8 Management and Restoration . 207 4.8.1 Nonstructural Techniques . 207 4.8.2 Structural Techniques . 209 Problems . 213 5 Groundwater 227 5.1 Introduction . 227 5.2 Contaminant Sources 228 5.2.1 Septic Tanks 228 5.2.2 Leaking Underground Storage Tanks . 230 5.2.3 Land Application of Wastewater . 230 5.2.4 Irrigation Return Flow . 231 5.2.5 Solid Waste Disposal Sites . 234 5.2.6 Waste Disposal Injection Wells 235 5.2.7 Agricultural Operations 235 5.3 Fate and Transport Models 235 5.3.1 Instantaneous Line Source . 239 5.3.2 Continuous Line Source 240 5.3.3 Continuous Plane Source . 242 5.3.4 Continuous Point Source 245 5.3.5 Consideration of Uncertainty . 246 5.4 Transport Processes 246 5.5 Fate Processes . 257 5.5.1 Sorption . 257 5.5.2 First-Order Decay . 266 5.5.3 Combined Sorption and Decay 268 5.5.4 Biocolloids . 270 5.5.4.1 Conventional colloid ltration theory . 270 5.5.4.2 Modified colloid ltration theory 271 5.5.4.3 Accounting for dieoff 271 5.6 Nonaqueous-Phase Liquids . 272 5.6.1 Residual Saturation 274 5.6.2 Raoult's Law 276 5.6.2.1 Effects on saturation vapor pressure 276 5.6.2.2 Effects on saturation concentration 277 5.6.2.3 Soil samples . 280 5.7 Monitoring Wells 281 5.8 Remediation of Subsurface Contamination 287 5.8.1 Remediation Goals . 288 5.8.1.1 Vadose zone . 288 5.8.1.2 Saturated zone 288 5.8.2 Remediation Strategies 289 5.8.2.1 Free-product recovery 290 5.8.2.2 Excavation and disposal . 293 5.8.2.3 Soil-vapor extraction 294 5.8.2.4 Bioventing 300 5.8.2.5 Air sparging . 300 5.8.2.6 Pump-and-treat systems 301 5.8.2.7 Bioremediation 309 5.8.2.8 In situ reaction walls 310 5.8.2.9 In situ containment . 310 5.8.2.10 Natural attenuation . 312 Problems . 313 6 Watersheds 323 6.1 Introduction . 323 6.2 Urban Watersheds . 324 6.2.1 Sources of Pollution 326 6.2.2 Fate and Transport Processes . 329 6.2.2.1 Event mean concentration model 330 6.2.2.2 Buildup-washoff models . 337 6.2.3 Stormwater Control Measures . 340 6.2.3.1 Source control measures . 341 6.2.3.2 Hydrologic modifications 342 6.2.3.3 Attenuation of pollutants 346 6.2.3.4 Collection system pollution control . 348 6.2.3.5 Detention-retention facilities 349 6.3 Agricultural Watersheds 354 6.3.1 Sources of Pollution 356 6.3.2 Fate and Transport Processes . 358 6.3.2.1 Erosion 359 6.3.2.2 Soil pollution . 369 6.3.3 Best Management Practices 376 6.3.3.1 Cropping practices 377 6.3.3.2 Integrated pest management 378 6.3.3.3 Nutrient management 378 6.3.3.4 Terraces and diversions . 379 6.3.3.5 Critical area treatment . 379 6.3.3.6 Sediment basins and detention-retention ponds 380 6.3.3.7 Animal waste storage and treatment 380 6.3.3.8 Livestock exclusion fences 381 6.3.3.9 Filter strips and eld borders 381 6.3.3.10 Wetland rehabilitation 382 6.3.3.11 Riparian buffer zones 382 6.3.3.12 Irrigation water management 382 6.3.3.13 Stream bank stabilization 383 6.3.3.14 Range and pasture management 383 6.4 Airsheds . 384 Problems . 386 7 Lakes and Reservoirs 389 7.1 Introduction . 389 7.2 Physical Processes . 393 7.2.1 Circulation . 393 7.2.2 Sedimentation . 395 7.2.3 Light Penetration 397 7.3 Eutrophication . 399 7.3.1 Biomass-Nutrient Relationships 401 7.3.2 Measures of Trophic State . 405 7.3.3 Depth of Anoxia 410 7.4 Thermal Stratication . 411 7.4.1 Layer Characteristics 413 7.4.2 Gravity Circulation 413 7.4.3 Water-Quality Impacts . 415 7.4.4 Measures of Mixing Potential . 416 7.4.4.1 Richardson number . 416 7.4.4.2 Densimetric Froude number . 417 7.4.5 Articial Destratication . 418 7.5 Water-Quality Models . 420 7.5.1 Zero-Dimensional (Completely Mixed) Model 420 7.5.1.1 Conservation of mass model 420 7.5.1.2 Conservation of energy model . 424 7.5.2 One-Dimensional (Vertical) Models 427 7.5.2.1 Conservation of mass model 427 7.5.2.2 Conservation of energy model . 429 7.5.2.3 Estimation of the vertical diffusion coefficient . 431 7.5.3 Two-Dimensional Models . 435 7.6 Management and Restoration . 439 7.6.1 Control of Eutrophication . 439 7.6.1.1 Control of point sources . 440 7.6.1.2 Control of nonpoint sources . 440 7.6.1.3 Chemical treatments for phosphorus 440 7.6.1.4 Limitation of internal loading 440 7.6.1.5 Control of algal development. 442 7.6.2 Control of dissolved oxygen concentrations . 442 7.6.2.1 Artificial circulation . 442 7.6.2.2 Water fountains . 444 7.6.2.3 Hypolimnetic aeration 444 7.6.2.4 Oxygen injection . 444 7.6.2.5 Pump-and-baffle aeration system 445 7.6.2.6 Snow removal to increase light penetration 445 7.6.3 Control of Acidity . 445 7.6.4 Control of Aquatic Plants . 446 Problems . 449 8 Wetlands 457 8.1 Introduction . 457 8.2 Natural Wetlands 457 8.2.1 Classification 458 8.2.1.1 Marshes 458 8.2.1.2 Swamps 459 8.2.1.3 Bogs 461 8.2.1.4 Fens 462 8.2.2 Delineation of Wetlands 462 8.2.2.1 Vegetation 463 8.2.2.2 Soils 466 8.2.2.3 Hydrology 466 8.2.3 Water Budget 466 8.2.3.1 Net surface water in ow . 469 ix 8.2.3.2 Net groundwater in ow . 469 8.2.3.3 Evapotranspiration . 469 8.3 Constructed Treatment Wetlands . 469 8.3.1 Classification 470 8.3.1.1 Free water surface wetlands . 472 8.3.1.2 Horizontal subsurface ow wetlands 473 8.3.1.3 Vertical ow wetlands 475 8.3.2 Design of FWS Wetlands . 475 8.3.2.1 Hydrology and hydraulics 475 8.3.2.2 Performance-based sizing 482 8.3.2.3 Other considerations . 486 Problems . 490 9 Oceans and Estuaries 493 9.1 Introduction . 493 9.2 Ocean-Outfalls . 494 9.2.1 Near-Field Mixing . 497 9.2.1.1 Single plumes . 497 9.2.1.2 Line plumes . 506 9.2.1.3 Design considerations 513 9.2.2 Far-Field Mixing 517 9.3 Multiport Diffusers for Dense Discharges . 524 9.4 Oil Spills 528 9.4.1 Physical Properties of Oil . 529 9.4.2 Environmental Conditions . 532 9.4.3 Fate and Transport Processes . 536 9.4.3.1 Transport . 536 9.4.3.2 Initial spreading . 538 9.4.3.3 Dispersion 540 9.4.3.4 Evaporation . 545 9.4.3.5 Emulsification 550 9.4.3.6 Dissolution 554 9.4.3.7 Photo-oxidation . 559 9.4.3.8 Biodegradation 559 9.4.3.9 Interaction with suspended particulate material . 560 9.4.3.10 Shoreline stranding . 561 9.4.4 Toxicity . 562 9.5 Chemical Spills . 564 9.5.1 Chemical Properties 564 9.5.1.1 Density 564 9.5.1.2 Solubility . 564 9.5.1.3 Saturation vapor pressure and boiling point 565 9.5.1.4 Flash point 565 9.5.1.5 Behavior classifications . 565 9.5.1.6 Toxicity 566 9.6 Estuaries 566 9.6.1 Classification of Estuaries . 567 9.6.2 Water-Quality Issues 569 9.6.3 Salinity Distribution 569 9.6.4 Dissolved Oxygen{The Estuary Streeter-Phelps Model . 572 9.6.5 Flow and Circulation 575 9.6.5.1 Flushing time 577 9.6.5.2 Net 579 Problems . 580 10 Analysis of Water Quality Measurements 587 10.1 Introduction . 587 10.2 Probability Distributions 587 10.2.1 Properties of Probability Distributions 588 10.2.2 Mathematical Expectation and Moments 588 10.3 Fundamental Probability Distributions 590 10.3.1 Normal Distribution 590 10.3.2 Log-Normal Distribution 593 10.3.3 Uniform Distribution 595 10.4 Derived Probability Distributions . 596 10.4.1 Chi-Square Distribution 596 10.4.2 Student's t Distribution 598 10.4.3 F Distribution . 599 10.5 Estimation of a Population Distribution from Sample Data 600 10.5.1 Sample Probability Distribution . 601 10.5.2 Comparisons of Probability Distributions 603 10.5.2.1 The chi-square test . 603 10.5.2.2 Kolmogorov-Smirnov test 605 10.6 Estimation of Parameters of Population Distribution 606 10.6.1 Method of Moments 606 10.6.2 Maximum Likelihood Method . 608 10.6.3 Method of L-moments . 610 10.7 Probability Distributions of Sample Statistics 611 10.7.1 Mean 612 10.7.2 Variance . 612 10.7.3 Coefficient of Skewness . 613 10.7.4 Median . 613 10.7.5 Coefficient of Variation 613 10.7.6 Useful Theorems 615 10.8 Confidence Intervals 615 10.8.1 Mean 616 10.8.2 Variance . 616 10.8.3 Variance Ratios . 617 10.9 Hypothesis Testing . 618 10.9.1 Mean 619 10.9.2 Variance . 620 10.9.3 Population Differences . 620 10.9.3.1 t test . 620 10.9.3.2 Analysis of variance . 621 10.9.3.3 Kruskal-Wallis test 625 10.9.4 Normality 627 10.9.4.1 Shapiro-Wilk test 627 10.9.4.2 Shapiro-Francia test . 629 10.9.4.3 Data transformations to achieve normality 630 10.9.5 Trends 630 10.9.5.1 Mann-Kendall test 631 10.9.5.2 Sen's slope estimator 632 10.10Relationships between Variables 634 10.10.1 Correlation . 634 10.10.2 Regression Analysis 636 10.10.2.1 Confidence limits of predictions 639 10.10.2.2 Coefficient of determination . 639 10.11Functions of Random Variables 640 10.11.1 Addition and Subtraction . 641 10.11.2 Multiplication 642 10.11.3 Division . 643 10.11.4 Other Functions 644 10.12Kriging . 646 10.12.1 The Stationary Case 646 10.12.2 The Intrinsic Case . 651 Problems 657 11 Modeling 667 11.1 Introduction . 667 11.2 Code Selection . 668 11.3 Calibration . 668 11.3.1 Sensitivity Analysis 670 11.3.2 Performance Analysis . 672 11.3.2.1 Error statistics 672 11.3.2.2 Modified error statistics . 675 11.3.2.3 Coefficient of determination . 676 11.3.2.4 Nash-Sutcliffe efficiency . 677 11.3.2.5 Index of agreement . 679 11.3.2.6 Hydrologic measures . 679 11.3.3 Parameter Estimation . 680 11.3.3.1 Multi-objective optimization 681 11.3.3.2 Bayesian approaches . 681 11.3.3.3 Generalized likelihood uncertainty estimation (GLUE) 683 11.4 Validation 684 11.5 Simulation 685 11.6 Uncertainty Analysis 685 11.6.1 Monte Carlo Analysis . 685 11.6.2 Latin Hypercube Sampling 686 11.6.3 Bayesian Monte Carlo Analysis 686 11.6.4 Analytical Probability Models . 687 11.6.5 First-Order Uncertainty Analysis . 688 A Units and Conversion Factors 691 A.1 Units . 691 A.1.1 Derived Units 692 A.1.2 Abbreviations 692 A.1.3 Prefixes693 A.2 Conversion Factors . 693 B Fluid Properties 695 B.1 Water 695 B.2 Organic Compounds in Found in Water . 696 B.3 Air at Standard Atmospheric Pressure 698 C Statistical Tables 699 C.1 Areas Under Standard Normal Curve . 699 C.2 Critical Values of the t Distribution . 702 C.3 Critical Values of the Chi-Square Distribution 704 C.4 Critical Values of the F Distribution (a = 0.05) . 705 C.5 Critical Values for the Kolmogorov-Smirnov Test Statistic . 707 D Special Functions 709 D.1 Error Function . 709 D.2 Bessel Functions 710 D.2.1 Definition 710 D.2.2 Evaluation of Bessel Functions 710 D.3 Gamma Function 715 D.4 Exponential Integral 716 Bibliography 717 Index 756