Part 6: Water Pollution

Point source pollution - source is from drain pipes, ditches, sewer outfalls, factories and power plants - easy to monitor and regulate

Nonpoint source pollution - runoff from farm fields and feedlots, lawns and gardens, golf courses, construction sites, atmospheric deposits - no specific location so harder to monitor and regulate

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Types and Results of Water Pollution• Infectious agents - 25 million deaths a year• Organic materials - biological oxygen demand (BOD)

increase resulting in oxygen sag• Plant nutrients - eutrophication, toxic tides• Metals - mercury and lead poisoning• Nonmetallic salts - poison seeps and springs• Acids and bases - ecosystem destabilization• Organic chemicals - birth defects, cancer• Sediments - clogged estuaries, death of coral reefs• Thermal pollution - thermal plume

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Infectious Agents

• Main source of waterborne pathogens is untreated and improperly treated human waste.– Animal wastes from feedlots and fields is also an important

source of pathogens.

– In developed countries, sewage treatment plants and pollution-control devices have greatly reduced pathogens.

– Tests for water quality are done for coliform bacteria (intestinal bacteria). Such tests are easier and cheaper.

• Escherichia coli (E. coli) is the major coliform bacterium species

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Basics for Understanding Environmental Implications of Oxygen-Demanding Wastes

• Water with a Dissolved Oxygen Content (DOC) content > 6 parts per million (ppm) will support desirable aquatic life, whereas water with < 2 ppm oxygen will support mainly detritivores and decomposers.

• Oxygen is added to water by diffusion from wind and waves, and by photosynthesis from green plants, algae, and cyanobacteria. Oxygen is removed from water by respiration and oxygen-consuming processes.

• Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen consumed by aquatic microorganisms in respiration.

• When organic wastes are added to rivers, microorganisms demand oxygen for respiration used in consuming the increase in food resource. As a result, DOC levels decline downstream (oxygen sag) from a pollution source as decomposers metabolize organic waste materials.

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Oxygen sag

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Plant Nutrients and Cultural Eutrophication

• Oligotrophic - Bodies of water that have clear water and low

biological productivity.• Eutrophic - Bodies of water that

are rich in organisms and organic

material.– Eutrophication - Process of

increasing nutrient levels and biological productivity.

• Cultural Eutrophication - Increase in biological productivity and ecosystem succession caused by human activities.

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Three "waters" I have measured:

BODWater mg/liter pH------------------------------------------------------- 1) 205 6.9 2) 73,000 2.5 3) 89,000 6.6

Which one would you rather drink?

BODWater mg/liter pH Win05 Win06 Win07------------------------------------------------------------------ 1) 205 6.9 >200 >200 >200 2) 73,000 2.5 1 0 1 3) 89,000 6.6 2 1 2

Three "waters" I have measured:

BODWater mg/liter pH what is it? ------------------------------------------------------------------- 1) 205 6.9 Snoqualmie Pass Sewage 2) 73,000 2.5 Coca Cola Classic 3) 89,000 6.6 Whole milk

Inorganic Pollutants• Metals

– Many metals such as mercury, lead, cadmium, and nickel are highly toxic.

• Highly persistent and tend to bioaccumulate in food chains.– Lead pipes are a serious source of drinking water pollution.– Mine drainage and leaching are serious sources of environmental

contamination.

• Nonmetallic Salts– Many salts that are non-toxic at low concentrations can be mobilized by

irrigation and concentrated by evaporation, reaching levels toxic to plants and animals.

• Leaching of road salts has had detrimental effect on many ecosystems.

• Acids and Bases– Often released as by-products of industrial processes.

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Organic Chemicals

• Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc.

• Two most important sources of toxic organic chemicals in water are:– Improper disposal of industrial and household

wastes.– Runoff of pesticides from high-use areas.

• Fields, roadsides, golf courses

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Sediment

• Human activities have accelerated erosion rates in many areas.– Cropland erosion contributes about 25 billion

metric tons of suspended solids to world surfaces each year.

• Sediment can either be beneficial (nourish floodplains) or harmful (smother aquatic life).

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Thermal Pollution• Raising or lowering water temperatures from normal

levels can adversely affect water quality and aquatic life.– Oxygen solubility in water decreases as temperatures

increase. • Species requiring high oxygen levels are adversely affected by

warming water.

• Industrial cooling often uses heat-exchangers to extract excess heat, and discharge heated water back into original source.– Thermal Plume

• Produce artificial environments which attract many forms of wildlife.

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Part 7: Water Quality Today10-29

Groundwater and Drinking water Pollution

• About half the US population, and 95% of rural residents, depend on underground aquifers for drinking water.– For decades, groundwater was assumed

impervious to pollution. It was considered the gold standard for water quality.

• An estimated 1.5 million Americans fall ill from fecal contamination annually.

– Cryptosporidium outbreaks

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Groundwater Pollution10-31

Progress and Problems in Other Countries

• Sewage treatment in wealthier countries of Europe generally equal or surpass the US.

• In Russia, only about half of the tap water supply is safe to drink.

• In urban areas of South America, Africa, and Asia, 95% of all sewage is discharged untreated into rivers.

• Two-thirds of India's surface waters are contaminated sufficiently to be considered dangerous to human health.

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Part 8: Pollution Control

• Nonpoint Pollution Sources and Land Management– Reduce nutrient loading thru land use regulations– Source reduction is cheapest and most effective way to

reduce pollution. To work society must get public and business leaders to avoid producing or releasing substances into the environment.

• Studies show as much as 90% less road salt can be used without significantly affecting winter road safety.

• Soil Conservation• Banning phosphate detergents

• Sewage Treatment• Remediation

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Sewage Treatment• Rationale

– More than 500 pathogenic bacteria, viruses, and parasites can travel from human or animal excrement through water.

• Natural Processes– In many areas, outdoor urination and defecation is the

norm.• When population densities are low, natural processes can

quickly eliminate waste.

• Artificial Wetlands Are a Low Cost Method – Natural water purification

• Effluent can be used to irrigate crops or raise fish for human consumption.

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Municipal Sewage Treatment• Primary Treatment - Physical separation of large solids from the

waste stream.• Secondary Treatment - Biological degradation of dissolved

organic compounds.– Effluent from primary treatment transferred into trickling bed, or

aeration tank• Effluent from secondary treatment is usually disinfected (chlorinated)

before release into nearby waterway.

• Tertiary Treatment - Removal of plant nutrients (nitrates and phosphates) from secondary effluent.– Chemicals, or natural wetlands.

• In many US cities, sanitary sewers are connected to storm sewers.– Heavy storms can overload the system, causing by-pass dumping

of raw sewage and toxic runoff directly into watercourses.

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Sewage Treatment10-36

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Water Remediation

• Containment methods confine liquid wastes in place, or cap surface with impermeable layer to divert water away from the site.

• Extraction techniques are used to pump out polluted water for treatment.– Oxidation, reduction, neutralization, or

precipitation.• Living organisms can also be used effectively

to break down polluted waters.

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• Clean Water Act (1972)– Goal was to return all U.S. surface waters to "fishable

and swimmable" conditions.• For Point Sources, Discharge Permits and Best Practicable

Control Technology are required.– Set zero discharge for 126 priority toxic pollutants.

• Areas of Contention– Draining or Filling of Wetlands

• Many consider this taking of private land.

– Un-funded Mandates• State or local governments must spend monies not repaid by

Congress.

Part 9: WATER LEGISLATION

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