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2623 results in Civil and geotechnical engineering

Page 20 of 132

  • 2 - Water Demand

  • from Part I - Concepts Related to Water
  • Sudha Goel
  • Book:
    Water and Wastewater Engineering
    Published online:
    11 August 2021
    Print publication:
    21 November 2019, pp 35-66

  • Summary

    Learning Objectives

  • • Determine water requirements for different uses, communities, and future populations

  • • Define consumptive and non-consumptive uses of water

  • • Cite appropriate standards for different uses of water and determine minimum water requirements

  • • Describe how scale affects quantification of water use

  • • Describe differences in water use and supply in rural and urban communities in India

  • • Model available population data to forecast future populations in different communities

  • • Justify the use of different population forecasting methods for different conditions

  • • Quantify seasonal and daily variations in water demand for design of water supply systems

    • Water is the most important requirement for sustaining life. Design of water supply systems requires that the water source be adequate in terms of quantity, quality and sustainability. Design of wastewater systems requires knowledge of water quantities used and treatment standards to be achieved. This chapter deals with the different uses of water and how much needs to be supplied at a minimum.

    Figure 2.1 shows the flow of water through water supply and wastewater systems for any given location, e.g., a city, town, or small community. Water is extracted from a groundwater or surface water resource and is taken for treatment to a water treatment plant. The degree of treatment provided depends on the quality of the raw water. After treatment, the water is sent into the distribution system from where it reaches individual consumers. These consumers may be single households, apartment buildings, offices, industries or factories, commercial or business establishments, or any other place where clean water is required.

    After use, the discarded water is termed ‘wastewater’ and in general, it goes into drains in sewered communities. The wastewater in sewerage systems is taken for treatment to a wastewater treatment plant. After treatment, the wastewater is discharged on land or in the sea, or it can be reused for horticulture, irrigation, industrial uses, and cleaning activities depending on the degree of treatment provided. Where drainage or sewerage systems are not present, the wastewater may be drained into cess pits, septic tanks, or reused after providing some treatment.

    DESIGN OF WATER SUPPLY SYSTEMS

    The most important task in the design of water supply systems is identification of an appropriate source of water.

  • Preface

  • Sudha Goel
  • Book:
    Water and Wastewater Engineering
    Published online:
    11 August 2021
    Print publication:
    21 November 2019, pp xi-xii

  • Summary

    ‘Water and Wastewater Engineering’ is a core course in undergraduate programs in civil engineering. The course objective is to ensure that a student is able to evaluate different water resource options for their sustainability, quantity and quality, and to design appropriate municipal water supply and wastewater systems. These water supply systems will necessarily require sourcing of water, its collection, treatment and distribution. Wastewater generated within these systems has to be treated in treatment plants so that it can be reused or disposed of on land or in water bodies after achieving discharge standards. Wastewater reuse has become an extremely important topic these days due to severe water scarcity in many parts of the world, including India.

    This textbook covers all aspects of municipal water and wastewater systems and is designed for a one-semester course. Prior to designing water and wastewater treatment plants, it is necessary to identify and develop an appropriate water source. For this, the student must be familiar with different types of water resources: surface water and groundwater, and concepts related to their quantity and quality. These are covered in the first and second chapters of this book. Fundamental concepts from chemistry, microbiology, and chemical engineering are covered in the first part of the book (Chapters 3 and 4) as these are necessary for understanding water quality issues, and designing water and wastewater systems. The second part of the book includes the design of conventional water treatment plants with unit processes like aeration, sedimentation, coagulation, filtration, and disinfection; design of conventional wastewater treatment plants with unit processes like screening, sedimentation, biological processes, activated sludge process and trickling filters or biofilters, sludge treatment, and disposal; water distribution methods; wastewater collection, reuse, and disposal options; and non-conventional treatment strategies for removal of specific pollutants like fluoride, arsenic, nitrate, and natural organic matter.

    This textbook started as a spin-off of an online course of the same name. However, several topics that could not be covered in the online course are also included in the textbook. The text material has been expanded and the number of problems increased. Solutions to all problems are provided. Some of the problems will require the use of spreadsheets or other software for graphing and calculations.

  • 6 - Biological Processes for Water and Wastewater Treatment

  • from Part II - Water and Wastewater Treatment Processes
  • Sudha Goel
  • Book:
    Water and Wastewater Engineering
    Published online:
    11 August 2021
    Print publication:
    21 November 2019, pp 263-342

  • Summary

    Learning Objectives

  • • Estimate the quantity and quality of wastewater generated in a community

  • • Analyze variations in wastewater quantities, flow and quality and determine treatment requirements

  • • Explain the advantages and disadvantages of attached versus suspended biological growth processes

  • • Use available models and equations to design attached or suspended growth biological processes

  • • Analyze and design clarifiers for hindered and compression settling (for thickened sludge)

  • • Evaluate the extent and type of sludge management options available and applicable for a given water or wastewater

  • • Compare and contrast anaerobic versus aerobic digestion

  • • Analyze potential for energy recovery from wastewater

  • • Evaluate and design appropriate processes for sludge dewatering and disposal

  • • Describe conditions under which Type 3 and 4 settling takes place and how it can be modeled

  • • Design sludge thickeners for hindered and/or compression settling

  • • Explain the conditions under which anaerobic sludge digestion is an appropriate treatment process, i.e., pre-conditions

  • • List the different types of anaerobic digesters that can be used

  • • Explain the conditions under which aerobic digestion of sludge is more appropriate than anaerobic digestion

  • • Describe the need for sludge dewatering prior to disposal

  • • Describe the need for disinfection in water or wastewater treatment and design the process

  • • Evaluate the merits and demerits of different types of disinfectants

    • The main objective of wastewater treatment is to ensure that water resources to which wastewater is returned are not contaminated for downstream users and for future uses. Reasons for treating wastewater can be divided into two categories:

  • a. Public health concerns: Untreated wastewater can cause long-term contamination not only of water but also of soil, sediments and the biota that grows in contact with the contaminated water. Contaminated wastewater may contain pathogenic organisms and serve as a habitat for disease vectors like mosquitoes. Further, contamination of any parts of the food web can lead to bioaccumulation of contaminants in the tissue of organisms leading to various health problems such as cancers, reproductive and developmental defects.

  • b. Environmental concerns: There is growing awareness of the importance of maintaining and preserving ecosystems. Any activities that are detrimental to the health of these ecosystems, including discharge of untreated wastewater, are not acceptable. There are several other reasons for ensuring that wastewater discharged to land, water or sea is adequately treated.

Water and Wastewater Engineering
  • Sudha Goel
  • Published online:
    11 August 2021
    Print publication:
    21 November 2019
  • This comprehensive textbook highlights the fundamental concepts and design principles related to water and wastewater engineering. Problems and issues arising from the lack of sustainable conventional treatment practices and potential methods for resolving problems are discussed in detail. The book starts with an introduction to water resources and the need for water and wastewater treatment, followed by evaluation of water demand in terms of quantity and quality. Mass transfer and transformation processes that are necessary for understanding the complexity of water pollution issues and treatment processes are discussed in detail. Pedagogical features include learning objectives, chapter-wise study outlines, detailed solutions to important problems and self-evaluation exercises with answers. Case studies for specific water treatment requirements are provided to enable the students to choose and apply only relevant treatment processes in their design.

  • 8 - Water Transport and Distribution Systems

  • from Part II - Water and Wastewater Treatment Processes
  • Sudha Goel
  • Book:
    Water and Wastewater Engineering
    Published online:
    11 August 2021
    Print publication:
    21 November 2019, pp 382-396

  • Summary

    Learning Objectives

  • • Describe different types of conduits and conditions for their use

  • • Describe different types of distribution reservoirs and conditions for their use

  • • Design distribution networks

    • A major issue in the design of water supply schemes is the collection, transport and distribution of water from the source. Collection of water from different sources, i.e., surface water versus groundwater, will differ for obvious reasons and was covered in Chapter 1.

    The next major issue is the transport and distribution of water from the source or treatment plant to the community or service area. Different situations require different methods of transport and distribution. Distribution systems can be of three types: gravity, pumped or combined (Peavy, Rowe, and Tchobanoglous 1985).

    Gravity distribution systems: If the source is elevated with respect to the community then water can be supplied directly by gravity. Examples are highland lakes or reservoirs that are used as water sources for many cities around the world such as New York and Mumbai.

    Pumped distribution systems: If the source is at a lower elevation compared to the community or service area then it has to be pumped directly to the service area.

    Combined distribution systems: If the source is at a lower elevation compared to the community or service area, then water can be pumped and stored in surface or elevated distribution reservoirs in the service area or adjacent to the service area resulting in a combined distribution system where gravity and pressure are used. Toronto pumps water out of Lake Ontario, treats the water and stores it in underground reservoirs and elevated reservoirs (called water towers) for further distribution to the service area.

    Different types of distribution reservoirs can be built; they can be under-ground, over-ground or elevated. Water is then supplied from these distribution reservoirs to the community or to elevated storage reservoirs built within the community. Thus, combinations of direct gravity supply, pumped and/or elevated supplies are possible depending on the geography of the water source vis-à-vis the community. Definitional sketches of water supply conduits and service reservoirs are provided in Fair, Geyer, and Okun (1966).

    The last issue in water supply systems is the analysis of pipe flows and head losses through the distribution system. Hardy–Cross method for analysis of pipe flow in distribution networks is covered in the last section.

  • 4 - Mass Transfer and Transformation

  • from Part I - Concepts Related to Water
  • Sudha Goel
  • Book:
    Water and Wastewater Engineering
    Published online:
    11 August 2021
    Print publication:
    21 November 2019, pp 135-174

  • Summary

    Learning Objectives

  • • Analyze and quantify natural or engineered systems based on a mass balance approach

  • • Describe Brownian diffusion and the Stokes–Einstein equation for particle diffusion

  • • State Fick's first and second laws of diffusion for dissolved compounds

  • • Derive equations for different reaction orders including unknown reaction order

  • • Model or analyze the effect of environmental variables like temperature and pH on reactions and their kinetics

  • • Compare and contrast the different types of ideal reactors

  • • Describe the salient features of a batch reactor and derive a mass balance equation for it

  • • Describe the salient features of a CSTR and derive a mass balance equation for it

  • • Describe the salient features of a PFR and derive a mass balance equation for it

  • • Analyze pulse and step inputs of tracers to different types of reactors

  • • Determine average hydraulic residence times and dispersion numbers for the different types of reactors

  • • Use tracer data to model engineered and natural systems and predict their behavior/efficiency

  • • List and explain factors affecting growth of organisms including bacteria in nature or in the lab

  • • Determine bacterial growth rates for a specific set of conditions

  • • Describe different biochemical or metabolic pathways by which organisms derive energy for maintenance and creation of new biomass

  • • Derive equations for bacterial growth rates

    • A mass balance approach can be utilized for analyzing and quantifying the behavior of contaminants in any system: natural or engineered. Basic concepts of mass transfer and transformation can be applied to all processes including those in water and wastewater treatment, no matter how simple or complex they may be. Mass transfer and transformation are based on the laws of conservation of mass. The concept of applying mass balances to any system and using the steady-state simplification to predict system behavior is introduced in the first section. The concept of reactions or mass transformation and their application to chemical or biological reactions or transformations is dealt with in the second section of this chapter. Zero-, first-, second-, mixed-order reactions are defined in this unit. The third section includes definitions of the three basic types of ideal reactors and how their behaviors differ.

  • 15 - Upscaling Petrophysical Properties

  • from Part IV - Reservoir Engineering Workflows
  • Knut-Andreas Lie
  • Book:
    An Introduction to Reservoir Simulation Using MATLAB/GNU Octave
    Published online:
    22 July 2019
    Print publication:
    08 August 2019, pp 558-596
    • Chapter
      • You have access
      • Open access
    • PDF
    • Export citation

  • Summary

    One of the most challenging tasks in reservoir engineering is to homogenize data from a fine to a coarser model in a systematic and robust manner. This chapter reviews a variety of such upscaling methods. Simple averaging is sufficient for additive properties but only correct in special cases for nonadditive properties like permeability. The correct effective permeability depends on the applied flow field. In flow-based upscaling, one solves local flow problems with various types of boundary conditions to determine effective permeabilities or transmissibilities. We outline the most common methods, and discuss methods that reduce the influence of the prescribed boundary conditions by computing flow solutions on larger domains. Computations are achieved by imposing boundary conditions derived from a global flow solution. A number of cases compare the accuracy of different upscaling methods, and we discuss how flow diagnostics can be used for quality control. The last example summarizes major parts of the book by going all the way from geological horizons via flow simulation to upscaled models with flow diagnostics quality control.

  • 8 - Mathematical Models for Multiphase Flow

  • from Part III - Multiphase Flow
  • Knut-Andreas Lie
  • Book:
    An Introduction to Reservoir Simulation Using MATLAB/GNU Octave
    Published online:
    22 July 2019
    Print publication:
    08 August 2019, pp 231-271
    • Chapter
      • You have access
      • Open access
    • PDF
    • Export citation

  • Summary

    This chapter introduces the basic equations used to describe multiphase flow. It also introduces key concepts such as saturation, wettability, relative permeability, and capillary pressure. Combining the multiphase extension of Darcy's law with mass conservation of fluid phases or chemical components gives a system of parabolic PDEs. The chapter derives the so-called fractional flow formulation and discusses several special cases of two-phase flow equations. The chapter ends with a discussion of various analytical and semi-analytical 1D solutions, including the classical Buckley–Leverett problem.

  • 10 - Solvers for Incompressible Immiscible Flow

  • from Part III - Multiphase Flow
  • Knut-Andreas Lie
  • Book:
    An Introduction to Reservoir Simulation Using MATLAB/GNU Octave
    Published online:
    22 July 2019
    Print publication:
    08 August 2019, pp 289-336
    • Chapter
      • You have access
      • Open access
    • PDF
    • Export citation

  • Summary

    This chapter teaches you how to simulate incompressible, two-phase flow using a sequential formulation that splits the equation system into an elliptic pressure equation and a hyperbolic (or parabolic) saturation equation. We discuss fluid objects, the sequential solution procedure, and explicit and implicit transport solvers in some detail. The second part of the chapter is devoted to a number of simulation examples that highlight typical flow behavior. Examples include gravity segregation, homogeneous quarter five-spots, heterogeneous quarter five-spots with viscous fingering, and buoyant migration of CO2 in a sloping aquifer. Furthermore, we discuss water coning, gravity override, capillary fringes, and a simplified simulation of the Norne field model. We end the chapter by a discussion of various sources of numerical errors, including splitting and grid-orientation errors.

  • 5 - Incompressible Solvers for Single-Phase Flow

  • from Part II - Single-Phase Flow
  • Knut-Andreas Lie
  • Book:
    An Introduction to Reservoir Simulation Using MATLAB/GNU Octave
    Published online:
    22 July 2019
    Print publication:
    08 August 2019, pp 143-173
    • Chapter
      • You have access
      • Open access
    • PDF
    • Export citation

  • Summary

    This chapter explains how the mathematical models from Chapter 4 are implemented and integrated to form a full simulator. To this end, we introduce data structures to represent fluid behavior, the reservoir state, boundary conditions, source terms, and wells. We then explain in detail how the two-point flux approximation (TPFA) scheme is implemented in MRST for general unstructured grids. We also outline the basic solver used to compute time-of-flight and tracer partitions. We end the chapter by presenting a few examples that demonstrate how to set up simulations in MRST and set appropriate boundary conditions, source terms, or well models. The examples include the famous quarter-five spot problem, a corner-point grid with four intersecting faults, and a model of a shallow-marine reservoir (SAIGUP).

Page 20 of 132