Water Supply and Pollution Control (8th Edition): A Comprehensive Textbook for Environmental Engineering Students
Water Supply and Pollution Control (8th Edition)
Water is essential for life, health, agriculture, industry, energy, recreation, and the environment. However, water resources are facing increasing pressures from population growth, urbanization, climate change, pollution, overexploitation, and degradation. Therefore, it is crucial to ensure adequate water supply and quality for various uses while preventing or minimizing water pollution and its impacts on human health and ecosystems.
Water Supply and Pollution Control (8th Edition)
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In this article, we will explore the concepts, principles, practices, challenges, and opportunities of water supply and pollution control. We will cover the following topics:
What is water supply and pollution control?
Why is water supply and pollution control important?
What are the main challenges and opportunities in water supply and pollution control?
What are the sources and types of water pollutants?
How are water quality standards and regulations established?
What are the conventional and advanced methods of water treatment?
How are water sources and demands assessed and managed?
How are water distribution networks designed and operated?
What are the components and functions of water supply systems?
How are wastewater sources and characteristics determined?
How are wastewater collection networks designed and operated?
What are the components and functions of wastewater treatment systems?
What are the benefits and challenges of water reuse?
How are reclaimed water quality and safety ensured?
What are the applications and technologies of water reuse?
Introduction
What is water supply and pollution control?
Water supply is the provision of sufficient quantity and quality of water for various purposes, such as domestic, agricultural, industrial, recreational, and environmental uses. Water supply involves the assessment, development, management, and distribution of water resources from various sources, such as surface water, groundwater, rainwater, and reclaimed water.
Water pollution is the contamination of water bodies or watercourses by substances or activities that adversely affect the water quality and the health of humans and ecosystems. Water pollution can be caused by point sources, such as industrial effluents, municipal sewage, and agricultural runoff, or by nonpoint sources, such as urban stormwater, atmospheric deposition, and diffuse land use. Water pollution can affect the physical, chemical, and biological properties of water, such as temperature, pH, dissolved oxygen, nutrients, metals, pathogens, and toxins.
Water pollution control is the prevention, reduction, or removal of water pollutants from water bodies or watercourses to protect or restore the water quality and the health of humans and ecosystems. Water pollution control involves the regulation, monitoring, treatment, and disposal of wastewater and stormwater from various sources.
Why is water supply and pollution control important?
Water supply and pollution control are important for several reasons:
Water is essential for human survival and well-being. According to the World Health Organization (WHO), about 2.2 billion people lack access to safely managed drinking water services, and about 4.2 billion people lack access to safely managed sanitation services. Lack of safe water and sanitation can lead to diseases, such as diarrhea, cholera, typhoid, dysentery, hepatitis A, and schistosomiasis. Improving water supply and sanitation can prevent millions of deaths and improve the quality of life of billions of people.
Water is vital for food security and economic development. Agriculture accounts for about 70% of global freshwater withdrawals, and industry accounts for about 20%. Water scarcity and pollution can threaten food production and industrial output, as well as increase the costs and risks of water supply. Ensuring adequate water supply and quality for agriculture and industry can enhance food security and economic growth.
Water is important for environmental sustainability and biodiversity. Water supports various ecosystems and habitats that provide essential services and benefits for humans, such as flood control, groundwater recharge, climate regulation, nutrient cycling, recreation, and cultural values. Water pollution can degrade ecosystems and habitats, as well as endanger the survival of many species of plants and animals. Protecting and restoring water quality and ecosystems can conserve biodiversity and ecosystem services.
What are the main challenges and opportunities in water supply and pollution control?
Water supply and pollution control face several challenges and opportunities in the 21st century:
Population growth and urbanization: The global population is expected to reach 9.7 billion by 2050, with about 68% living in urban areas. This will increase the demand for water supply and sanitation services, as well as generate more wastewater and stormwater that need to be managed. Population growth and urbanization also pose challenges for land use planning, infrastructure development, service delivery, governance, financing, and public participation in water supply and pollution control.
Climate change: Climate change is projected to alter the hydrological cycle and affect the availability and variability of water resources. Climate change can also exacerbate water-related hazards, such as floods, droughts, storms, sea level rise, and saltwater intrusion. Climate change can also affect the quality of water resources by changing the temperature, precipitation, evaporation, runoff, and infiltration patterns, as well as increasing the risk of waterborne diseases, algal blooms, and invasive species. Climate change can also affect the demand for water supply and sanitation services by changing the patterns of human activities, such as agriculture, industry, and recreation. Climate change poses challenges for adaptation and mitigation in water supply and pollution control.
Technological innovation: Technological innovation can offer new solutions and opportunities for improving water supply and pollution control. For example, new methods and technologies for water treatment can enhance the removal or recovery of pollutants or resources from wastewater and stormwater, such as nutrients, metals, organic matter, energy, and biogas. New methods and technologies for water distribution and supply systems can improve the efficiency and reliability of water delivery and reduce water losses or leakage. New methods and technologies for water reuse can expand the potential sources and applications of reclaimed water for various purposes, such as irrigation, industrial uses, urban uses, potable reuse, and environmental enhancement. New methods and technologies for monitoring and modeling can improve the data collection and analysis of water quantity and quality parameters, as well as support decision making and management in water supply and pollution control.
Water Quality Water Quality and Treatment
What are the sources and types of water pollutants?
Water pollutants are substances or activities that adversely affect the water quality and the health of humans and ecosystems. Water pollutants can originate from various sources, such as:
Industrial sources: These include factories, mines, power plants, refineries, and other industrial facilities that discharge wastewater or effluents containing chemicals, metals, organic matter, heat, or radioactive materials into water bodies or watercourses.
Municipal sources: These include households, businesses, institutions, and other urban or rural areas that generate sewage or wastewater containing human wastes, food wastes, detergents, oils, grease, pathogens, or pharmaceuticals. Municipal sources also include stormwater runoff from impervious surfaces, such as roads, roofs, parking lots, and sidewalks, that carry sediments, nutrients, pesticides, metals, bacteria, or litter into water bodies or watercourses.
Agricultural sources: These include farms, ranches, orchards, and other agricultural lands that produce runoff or leachate containing fertilizers, pesticides, animal wastes, organic matter, salts, or pathogens into water bodies or watercourses.
Natural sources: These include natural phenomena or processes that introduce substances or activities into water bodies or watercourses, such as volcanic eruptions, wildfires, landslides, earthquakes, erosion, weathering, or biological activity.
Water pollutants can be classified into different types based on their physical, chemical, or biological properties, such as:
Suspended solids: These are solid particles or materials that are suspended or floating in water, such as clay, silt, sand, organic matter, or microplastics. Suspended solids can reduce the clarity or transparency of water, as well as clog or damage pipes, filters, or pumps. Suspended solids can also affect the aquatic life by reducing the light penetration or oxygen diffusion in water, as well as by carrying other pollutants or pathogens attached to them.
Dissolved solids: These are solid particles or materials that are dissolved in water, such as salts, minerals, metals, or ions. Dissolved solids can affect the taste, odor, hardness, or conductivity of water, as well as the corrosion or scaling of pipes, fixtures, or appliances. Dissolved solids can also affect the aquatic life by altering the pH, osmotic pressure, or toxicity of water.
Nutrients: These are substances or elements that are essential for the growth and metabolism of living organisms, such as nitrogen, phosphorus, or carbon. Nutrients can be beneficial for the aquatic life in moderate amounts, but they can also cause problems when they are excessive or imbalanced in water. Excess nutrients can lead to eutrophication, which is the enrichment of water by nutrients that stimulates the growth of algae and other aquatic plants. Eutrophication can reduce the dissolved oxygen and biodiversity in water, as well as produce unpleasant odors or tastes.
Pathogens: These are microorganisms or organisms that can cause diseases or infections in humans or animals, such as bacteria, viruses, protozoa, or parasites. Pathogens can enter water through human or animal wastes, sewage overflows, stormwater runoff, wildlife activity, or recreational contact. Pathogens can pose serious health risks for humans and animals that consume or contact contaminated water. Some common waterborne diseases caused by pathogens are diarrhea, cholera, typhoid fever, dysentery, hepatitis A, and schistosomiasis.
Toxins: These are substances or compounds that can have harmful effects on humans or animals at certain concentrations or exposures, such as pesticides, herbicides, fungicides, insecticides, heavy metals, organic chemicals, pharmaceuticals, hormones, or endocrine disruptors. Toxins can enter water through industrial effluents, agricultural runoff, household wastes, atmospheric deposition, or accidental spills. Toxins can affect the health and reproduction of humans and animals by causing acute or chronic toxicity, cancer, mutations, or hormonal imbalances.
How are water quality standards and regulations established?
Water quality standards and regulations are established by various authorities and agencies at different levels, such as international, national, regional, or local, to protect or restore the water quality and the health of humans and ecosystems. Water quality standards and regulations can include:
Water quality criteria: These are scientific guidelines or recommendations that specify the acceptable levels or ranges of water quality parameters or indicators for different water uses or purposes, such as drinking water, recreational water, irrigation water, industrial water, or aquatic life protection. Water quality criteria can be based on physical, chemical, or biological properties of water, such as temperature, pH, dissolved oxygen, nutrients, pathogens, or toxins.
Water quality standards: These are legal rules or requirements that define the desired levels or ranges of water quality parameters or indicators for specific water bodies or watercourses based on their designated uses or classifications. Water quality standards can be derived from water quality criteria by considering other factors, such as social, economic, or technical feasibility. Water quality standards can also include antidegradation policies or provisions that prevent or limit the deterioration of existing water quality.
Water quality regulations: These are legal rules or requirements that prescribe the actions or measures that need to be taken by various entities or stakeholders to comply with or achieve the water quality standards. Water quality regulations can include permits, licenses, certifications, plans, programs, monitoring, reporting, enforcement, compliance assistance, incentives, or penalties.
What are the conventional and advanced methods of water treatment?
Water treatment is the process of improving the quality of water for various uses or purposes by removing or reducing the water pollutants or contaminants. Water treatment can involve physical, chemical, or biological methods or technologies that can be classified into conventional or advanced methods.
Conventional methods of water treatment are those that have been widely used and proven for a long time. They include:
Coagulation and flocculation
Coagulation and flocculation are processes that use chemicals, such as alum, iron, or polymers, to destabilize and aggregate the suspended solids or colloids in water into larger particles or flocs that can be easily removed by sedimentation or filtration. Coagulation and flocculation can also enhance the removal of other pollutants, such as nutrients, metals, organic matter, or pathogens, by adsorption or precipitation.
Sedimentation and filtration
Sedimentation and filtration are processes that use gravity or pressure to separate the solid particles or flocs from water. Sedimentation is the process of settling the solid particles or flocs at the bottom of a tank or basin by gravity. Filtration is the process of passing water through a porous medium, such as sand, gravel, cloth, or membrane, that traps and removes the solid particles or flocs by physical straining or adsorption. Sedimentation and filtration can also remove other pollutants, such as nutrients, metals, organic matter, or pathogens, by adsorption or biological activity.
Disinfection and chlorination
Disinfection and chlorination are processes that use chemicals, such as chlorine, ozone, or ultraviolet light, to inactivate or kill the pathogens in water. Disinfection and chlorination can also oxidize other pollutants, such as organic matter, metals, or toxins, by breaking down their molecular bonds or structures. Disinfection and chlorination can also provide residual disinfection or protection against recontamination of water during storage or distribution.
Advanced methods of water treatment are those that have been developed or improved in recent years. They include:
Membrane processes and reverse osmosis
Membrane processes and reverse osmosis are processes that use semipermeable membranes to separate dissolved solids or ions from water by applying pressure. Membrane processes and reverse osmosis can also remove other pollutants, such as organic matter, metals, pathogens, or toxins, by size exclusion or charge rejection. Membrane processes and reverse osmosis can produce high-quality water for various applications, such as desalination, potable reuse, or industrial uses.
Biological treatment and activated sludge
Water Distribution and Supply Systems
How are water sources and demands assessed and managed?
Water sources and demands are assessed and managed by various methods and tools that aim to balance the water availability and water use for various purposes. Water sources and demands can be assessed and managed by:
Water resources assessment: This is the process of collecting, analyzing, and reporting the data and information on the quantity and quality of water resources from various sources, such as surface water, groundwater, rainwater, and reclaimed water. Water resources assessment can also include the identification and evaluation of the potential impacts of climate change, land use change, or water development projects on water resources.
Water demand analysis: This is the process of estimating, forecasting, and projecting the current and future water use for various purposes, such as domestic, agricultural, industrial, recreational, and environmental uses. Water demand analysis can also include the identification and evaluation of the factors that influence water use, such as population growth, urbanization, economic development, technological innovation, or water conservation measures.
Water resources planning: This is the process of developing, evaluating, and selecting the strategies and actions that aim to achieve the optimal allocation and utilization of water resources for various purposes. Water resources planning can also include the formulation and implementation of policies, regulations, incentives, or programs that support the sustainable management of water resources.
Water resources management: This is the process of applying the strategies and actions that aim to ensure the adequate quantity and quality of water supply for various purposes while preventing or minimizing water pollution and its impacts on human health and ecosystems. Water resources management can also include the coordination and cooperation among various entities or stakeholders involved in water supply and pollution control.
How are water distribution networks designed and operated?
Water distribution networks are systems of pipes, pumps, valves, meters, hydrants, tanks, towers, and other components that convey water from the source or treatment plant to the point of use or consumption. Water distribution networks are designed and operated by various methods and tools that aim to ensure the efficiency and reliability of water delivery and reduce water losses or leakage. Water distribution networks are designed and operated by:
Hydraulic analysis: This is the process of applying the principles of fluid mechanics to calculate or simulate the flow rate, pressure, velocity, head loss, or energy consumption in water distribution networks under various scenarios or conditions. Hydraulic analysis can also include the identification and evaluation of the hydraulic performance or problems in water distribution networks, such as pipe friction, pump efficiency, valve operation, pressure fluctuation, or water hammer.
Network design: This is the process of determining or optimizing the size, location, configuration, or layout of the components or elements in water distribution networks based on various criteria or objectives, such as cost, reliability, flexibility, or redundancy. Network design can also include the selection or specification of the materials, standards, or specifications for the components or elements in water distribution networks, such as pipe diameter, pump capacity, valve type, or tank volume.
Network operation: This is the process of control