Living with the Earth Chapter 9 - University of South Floridaeta.health.usf.edu/publichealth/phc6357/topic10/slide09_handout.pdf · 4 WATER and WASTEWATER - Moore 7 The Properties

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WATER and WASTEWATER -Moore

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LIVING WITH THE EARTH


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Objectives for this Chapter

• A student reading this chapter will be able to:– 1. List and describe the different stages of

the hydrological cycle and the relative amounts of freshwater on the planet.

– 2. List the three main consumers of water, noting each consumer’s major use of water.

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• A student reading this chapter will be able to:– 3.Discuss water scarcity, pointing out the

areas of the world at risk of water shortage and potential associated conflict. Describe some methods of water management.

– 4. List and describe several sources of freshwater, and describe the types of wells used to pump groundwater.


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• A student reading this chapter will be able to:– 5. Describe groundwater formation, including

a discussion of contamination, recharge, water mining, fossil water and some problems associated with overuse.

– 6.List the various sources and types of pollution threatening water supplies, noting the difference between point and nonpointsources.

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• A student reading this chapter will be able to:– 7. Briefly outline the Clean Water Act and the

Safe Drinking Water Act, explaining the purpose of each.

– 8.Describe the process and purpose of wastewater treatment. List the components of a septic system, and the components of a typical wastewater treatment plant. Define and describe BOD and sag curve.


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WATER and WASTEWATER

• Introduction– Water is cheap, accessible, plentiful, and

relatively safe to drink.– Differences in beliefs about the importance of

water quality, water scarcity, and water use can cause conflict and hinder a joint effort to protect the world’s water supplies.

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The Properties of Water

– Water is a unique compound (Fig. 9-1)– Water exerts a major influence on the earth’s

environments.– Water carries partial negative charge and

partial positive charge, and easily dissolves most polar molecules. It is critical to life.

– Water exists as a solid, a liquid, and a vapor. Water is essential in maintaining temperature of planet.


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Fig. 9-1

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Hydrological Cycle

– The hydrological cycle is a process involving the sun, the atmosphere, the earth and water (Fig. 9-2).

– This cycle consists of evaporation, condensation, transportation, transpiration, precipitation, and runoff.


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Fig. 9-2

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Water Resources

• Water covers 71% of the earth’s surface. The approximate amount of water on the earth is 1.3 billion cubic kilometers.

• Humans and animals require freshwater for consumption, which makes up only 3% of the total amount of water.


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Water and Health

• Access to clean water is critical to human well-being and survival.

• Over 1.7 billion people in the world lack access to clean drinking water.

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Water Shortage and Scarcity

• A 1995 World Bank report indicated that 40% of the world’s population live in countries facing water shortages.

• Globally, the demand for water has been increasing at about 2.3% annually, with a doubling of demand occurring every 21 years.


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Water Shortage and Scarcity

• One out of every five people on this planet lacks a clean water supply.

• At some point in the future, worldwide water use will be limited by physical, economic and environmental limitations.

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Water Rights and Conflicts

• Many major water sources cross national boundaries, ensuring disputes between countries staking their claim to this valuable resource.

• Bangladesh, India, Pakistan• NYC


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Water Consumption and Management

• Many factors impact the amount and the way a country uses water, including the economy, available technology, level of industry, and agriculture, culture, and climate.

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Water Consumption and Management

• Effective water management would improve water efficiency, decrease consumption, and help preserve remaining resources.

• Sustainable water use implies that current needs are met without diminishing the resource for future generations use and at no expense to environmental need.


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Water Use

• Overview– The three major water consumers in the world

are agriculture, industry, and households or individual use.

– In the United States, the average daily per capita water use from public supplies is approximately 180 gallons per day.

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Water Use

• Agriculture– Agriculture consumes the largest portion of

the freshwater supply, with over two-thirds of the world’s water demand used for irrigation.

– Sixty percent of this water is lost to evaporation or runoff.


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Water Use

• Industry– The industrial sector also uses large

quantities of water for numerous purposes, including manufacturing, cooling and condensation by power plants, and waste disposal.

– Approximate industrial water use in the United States is over 200 billion gallons per day.

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Water Use

• Domestic– Per capita domestic use in the United States

ranges between 75-135 gallons per capita per day (gpcd) (Fig. 9-3).

– The bulk of domestic water use serves for flushing toilets, showering, and watering lawns.


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Fig. 9-3

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Sources of Drinking Water

• Surface Water– The United States has vast amounts of

surface water, with 3.5 million miles of rivers and streams and 41 million acres of lakes.

– Due to its exposed state, surface water is prone to contamination from a number of sources, including diffuse pollution such as agricultural runoff.


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Surface Water

– Surface water sources and water sheds require protection and management to limit or prevent contamination.

– Watershed fencing, limited recreational access, and public education can help protect surface waters against pollution.

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Ground Water

– Groundwater volume worldwide is estimated to be 8.5 million km3 or 0.62% of the total water volume.

– Groundwater sources supply drinking water to 50% of the people living in the United States and to 90% of people living in U.S. rural areas.


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Ground Water

– When rain falls on the earth, some of the water percolates downward through the spaces in the soil, pulled by gravity.

– At a certain point, the water reaches an impermeable layer of rock. At this layer, the water stops moving (Fig. 9-4).

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Fig 9-4


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Wells

– Several types of wells exist, ranging from the crude to the sophisticated. Some wells are dug (Fig. 9-5) or bored; others are driven or drilled (Fig. 9-6).

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Fig. 9-5

dug well


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Fig. 9-6drilled well

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Groundwater Contamination

• Potential pollution sources in the United States include:– (1) over 23 million septic systems; – (2) between five and six million

underground storage tanks; – (3) millions of tons of pesticides and

fertilizers; and – (4) municipal landfills, and abandoned

hazardous waste sites.


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Groundwater Contamination

• Point Source– Refers to pollutants entering the environment

from a specific point such as a pipe or a specific source such as a factory or treatment plant.

• Non-point source– Refers to pollutants entering the environment

from a broad area and may include scattered sources (Table 9-1).

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Table9-1


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Recharge and Water Mining

– Recharge is the replacement of groundwater by natural processes.

– Water stress is an actual term defined as the ratio of water withdrawal to water availability.

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– Water systems such as the Ogallala aquifer are stressed from the large quantities of water being pumped out of these underground sources (Fig. 9-7).


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Fig. 9-7

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– Certain sources of groundwater are considered nonrenewable resources, like coal or oil.

– The overuse of these “fossil” waters is called water mining, because the resource is being permanently depleted.


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Subsidence and Salination

• Subsidence– Involves a settling of the soil as the water is

pumped out.• Salination

– As water is pumped out of the aquifer, the zone of saturation decreases at both the upper and lower levels. Saltwater can seep into the aquifer at the lower level, polluting the freshwater.

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The Following Laws Protect the Waters of the U.S.

• RCRA• CERCLA• SDWA• FIFRA• TSCA


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Water Pollution

– Much of the pollution that threatens our water supply today is anthropogenic in that it is generated by humans, and not part of a natural process.

– Industry, agriculture, and overpopulation have all contributed to pollution of the world’s water supply.

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Water Pollution

– Some strategies to protect water supplies include protection of areas near sources of drinking water, limitations on pollutant discharges into our waterways, and the processes of chlorination and filtration.


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Water Pollution

– Federal Water Pollution Control Act of 1972– Clean Water Act of 1977– The EPA estimates that public and private

costs for water pollution treatment is $64 million/year.

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Water Quality

– Water quality encompasses various characteristics of water, from taste, and color to temperature and purity.

– Water quality can vary, depending on its intended use: high quality is needed for drinking water; lower quality is sometimes acceptable for irrigation purposes, as in wastewater reuse.


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Water Quality

• Different types of pollutants may contaminate a water supply, these can be categorized as:– physical, – chemical, – biological and – radioactive contaminants.

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Types of Pollution

• Inorganic compounds– Of particular concern are lead, cadmium,

mercury, arsenic, and copper. – These substances can cause serious acute

and chronic health problems.


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Types of Pollution

• Synthetic Organic Chemicals– Synthetic organic compounds can be

classified as volatile organic compounds (VOCs) or synthetic organic chemicals (SOCs).

– Sources of synthetic organic compounds include industry, agriculture, even households.

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Synthetic Organic Chemicals

– VOCs present a threat to groundwater, where they are less able to vaporize and can accumulate.

– SOCs threaten surface waters, through both accidental and purposeful discharges into water ways.


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Types of Pollution

• Radiation– The most common radioactive substances in

water are radium, uranium, radon and certain man-made radionuclides.

– While naturally occurring radionuclides appear mainly in groundwater, surface waters are more likely to contain artificial radionuclides from atmospheric fallout.

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Sources of Pollution

• Point Source– Underground Injection Wells– Industrial Discharges

• National Pollution Discharge Elimination System (NPDES)


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• Nonpoint Source– Agriculture– Pesticides– Fertilizer

• Eutrophication

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• Nonpoint Source– Stormwater– Acid Mine Discharge– Waterborne Disease

• Over 900 deaths annually in the U.S.


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Water Treatment

• Municipal Water Treatment– In the United States, most of the drinking

water comes from 200,000 community water supply systems.

– These systems include approximately 140,000 small scale suppliers and 60,000 municipal supply systems, and supply water to 241 million Americans.

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Water Treatment

• The main steps of treatment are:– Sedimentation – coagulation-flocculation, – filtration, and – disinfection.


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Disinfection

– The most critical step in water treatment, disinfection, should destroy all organisms in the water supply.

– Chlorine is the major disinfectant used in United States’ water systems today.

– Trihalomethanes

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Regulations

• Safe Water Drinking Act– Allows the United States EPA to set Maximum

Contaminant Levels (MCLs) for water pollutants to protect the public health.

– Enforcement of the SDWA is left to the individual states, with oversight provided by the Office of Groundwater and Drinking Water, a division of the USEPA.


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Water Disposal and Treatment

• Sewage– In many developing countries around the

world, human waste pollutes the land and the water.

– This organic material can serve as food for organisms living in the water.

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Biological Oxygen Demand (BOD)

– As microorganisms decompose organic material in surface water, they use oxygen dissolved in the water.

– If a waterway is overloaded with biodegradable organic pollutants, this decomposition process can deplete the supply of dissolved oxygen.


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Biological Oxygen Demand (BOD)

– The deoxygenation and reaeration of water can be presented graphically as a Sag Curve.

– A Sag Curve demonstrates the level of dissolved oxygen over time, showing the critical level where aquatic life dies (Fig. 9-8).

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Fig. 9-8


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Types of Disposal

• Pit privies (Fig. 9-9)• Septic Systems (9-10, 9-11)• Municipal Sewage Treatment

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Fig. 9-9


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Fig. 9-10

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Fig 9-11 Failed septic system


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Fig 9-12a

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Fig 9-12b


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Municipal Sewage Treatment

– Sewage treatment speeds up water’s natural process of purification, through biooxidation, filtration and settling.

– Several stages of treatment include; primary; secondary; and tertiary treatments; and sludge disposal ( Fig. 9-13).

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Fig.9-13a


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Fig. 9-13b

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• Primary Treatment– Primary treatment is largely a mechanical

process, concerned with the removal of solids.

– Sewage first passes through a bar screen, then a grinder or Comminuter (Figs. 9-14a & 9-14b)

– Clarification or solids separation (Fig. 9-15a & 9-15b))


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Fig. 9-14a

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Fig 9-14b


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Fig. 9-15a

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Fig 9-15b


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• Secondary Treatment– Trickling filters and activated sludge treatment

employ bacteria to breakdown and digest organic material in the sewage (Figs. 9-16a & 9-16b)

– Sludge form primary or secondary treatment is dried (Fig 9-17a) and then disposed of in landfill or composted (Fig 9-17b)

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Fig. 9-16a


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Fig 9-16b

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Fig. 9-17a


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Fig. 9-17b

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• Tertiary Treatment– A number of tertiary treatments or advanced

wastewater treatment methods, including air stripping by ammonia and rapid granular filtration, reduce the BOD even more.


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• Sludge Treatment and Disposal– Sludge refers to the solids and liquids

separated out of wastewater during sewage treatment.

– Sludge disinfection is a crucial step, as it destroys pathogens in the sludge to prevent the spread of disease. Digested sludge may be air dried.

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Water Pollution and Health

– Increased risks of cancer and uncertainty about the future are just two issues the consumers of polluted water are faced with.

– Consumers armed with information about their water sources can protect themselves from exposure to polluted water.


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Future Outlook

– On a planet covered with water, yet plagued by waterborne disease, drought, and water mismanagement, we must promote conservation, efficiency, and frugality.

– Every drop counts.

Documents

Living with the Earth Chapter 9 - University of South Floridaeta.health.usf.edu/publichealth/phc6357/topic10/slide09_handout.pdf · 4 WATER and WASTEWATER - Moore 7 The Properties