Describe the Sources and Effects of Some Major Types of Water Pollution

Water Pollution

Objectives

©  Describe the sources and effects of some major types of water pollution

©  Appreciate why access to sewage treatment and clean water are important

©  Explain ways to control water pollution, including technological and legal solutions

Water pollution

© Any physical, biological, or chemical change in water quality that adversely affects living organisms can be considered pollution

Point sources

©  Discharge pollution from specific locations

©  Factories, power plants

©  Easy to control through regulations

Non-point sources

©  Non-point sources - Scattered or diffuse, having no specific location of discharge

©  Agricultural fields, feedlots

©  Very difficult to monitor and regulate

Atmospheric deposition

© Ultimate in non-point source pollution

© Contaminants carried by air currents and precipitated into watersheds or directly onto surface waters

© Agricultural (atrazine, toxaphene) and industrial (PCBs, dioxins) contaminants in the Great Lakes that cannot be accounted for by local sources alone

© Most thought to have been deposited from the atmosphere

© Several studies have indicated health problems among people who regularly eat Great Lakes fish

Infectious agents

© Main source of waterborne pathogens is improperly treated human waste

© Animal wastes from feedlots and fields is also important source of pathogens

Infectious agents

Infectious agents

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

© Waters monitored for coliform bacteria - intestinal bacteria including Escherichia coli (E. coli)

© Estimated 1.5 million Americans fall ill from fecal contamination annually

© Drinking water generally disinfected via chlorination

Oxygen-demanding wastes

©  Certain organic materials added to water stimulates oxygen consumption by decomposers

©  Sewage

©  Paper pulp

©  Food-processing wastes

Oxygen-demanding wastes

© Water with an oxygen content > 6 ppm will support “desirable” aquatic life

© Water with < 2 ppm oxygen will support mainly detritis feeders and decomposers (e.g. worms, bacteria, fungi)

© Oxygen is added to water by diffusion from wind and waves, and by photosynthesis from green plants and algae

© Oxygen is removed from water by respiration and oxygen-consuming chemical processes

Oxygen-demanding wastes

©  Effects of oxygen-demanding wastes on rivers depend on volume, flow, and temperature of river water

©  Faster flowing water has more oxygen

©  Lower temperature water has more oxygen

©  Oxygen sag - oxygen levels decline downstream from a pollution source as decomposers metabolize waste materials

Oxygen sag

Oxygen sag

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

© Some amount of eutrophication is normal

© Cultural eutrophication - Increase in biological productivity and ecosystem succession caused by human activities

Eutrophication

Eutrophication

Gulf of Mexico hypoxia

© In 1974, scientists found areas where oxygen had disappeared from bottom sediments and the water column

© First thought to be a minor natural disturbance

© Hypoxic area in 1993 after Mississippi floods doubled in size

© Stays from May to September

© Influx of nitrogen from Midwest/Great Plains is cause

© Hypoxic area continues to grow

Harmful algal blooms (HABs)

© HABs have become increasingly common in slow-moving and shallow waters, usually due to pollution

© Algal blooms produce toxins

© Red tides are blooms of deadly aquatic algae

© Cryptosporidium in 1993 entered the Milwaukee public water supply, making 400,000 people sick and killing at least 100 people

Pfiesteria piscicida

© First discovered in 1988 in open sores in fish in Chesapeake Bay

© Very complicated life cycle

© No fewer than 24 different life forms

© In 1997, fish kills led to the closing of Pocomoke River to all shellfish and fish harvests

© Economic loss was $15-20 million in MD alone

© Causes skin rashes, neurological disorders and death in humans

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 is serious source of metal pollution in water

Inorganic pollutants

© 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

© Coal mining

© Acid precipitation

Organic chemicals

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

© Many are highly toxic and bioaccumulate

Organic chemicals

©  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

Pesticide runoff

Sediment

©  Human activities have accelerated erosion rates in many areas

©  Human-induced erosion and runoff contribute about 75 billion metric tons of suspended solids to world surfaces each year

©  Fills lakes, obstructs shipping channels, makes drinking water purification more costly

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

Thermal pollution

©  Caused by altering vegetation cover and runoff patterns

©  Industrial cooling processes often use heat-exchangers to extract excess heat, and then discharge heated water back into original source

Ocean pollution

©  Estimated 6 million metric tons of plastic bottles, packaging material, and other litter tossed from ships into the ocean annually

Oil pollution

©  Few coastlines in the world remain uncontaminated by oil or oil products

©  Estimated 3-6 million metric tons of oil are discharged into the world’s oceans

©  Transport creates opportunities for major spills

Oil pollution

Groundwater and drinking water

©  About half the U.S. population, and 95% of rural residents, depend on underground aquifers for drinking water

©  For decades, groundwater was assumed impervious to pollution and was considered the gold standard for water quality

Groundwater and drinking water

©  EPA estimates 4.5 trillion liters of contaminated water seep into the ground in the U.S. every day

©  MTBE - Gasoline additive, and suspected carcinogen, is present in many urban aquifers

©  In agricultural areas, fertilizers and pesticides commonly contaminate aquifers and wells

Groundwater pollution

Water pollution control

©  Source reduction

©  Cheapest and most effective way to reduce pollution is avoid producing it or releasing it into the environment

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

©  Soil conservation

Non-point sources and land management

© Some main causes of non-point pollution:

© Agriculture

© Urban runoff

© Construction sites

© Land disposal

© Preserving wetlands

© In urban areas, reducing materials carried away by storm runoff is helpful

Watershed protection in the Catskills

© Water supply for New York City

© Worked with local farmers to reduce non-point pollution and preserve land

© Saved billions of dollars by performing watershed protection rather than building a treatment plant

Human waste disposal

©  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

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

Municipal sewage treatment

©  Tertiary treatment - Removal of plant nutrients (nitrates and phosphates) from secondary effluent.

©  Chemicals, or natural wetlands

©  In many U.S. 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

Low-cost waste treatment

©  Living systems such as wetlands

©  Effluent flows through wetlands where it is filtered and cleaned by aquatic plants and microscopic organisms

Water legislation

©  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 (BPT) are required

Clean Water Act (1972)

©  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

Other important water legislation

©  Safe Drinking Water Act (1974)

©  Regulates water quality

©  CERCLA (1980) (aka Superfund)

©  Cleans up abandoned or inactive sites

©  Great Lakes Water Quality Agreement (1972)

©  London Dumping Convention (1990)

Other important water legislation

©  Laws are only as good as:

©  To the degree they are not weakened

©  To the degree they are funded

Water quality today in US

©  Areas of Progress

©  In 1999, EPA reported 91.4% of all monitored river miles and 87.5% of all accessed lake acres are suitable for their designated uses

©  Most progress due to municipal sewage treatment facilities

Remaining problems

© Greatest impediments to achieving national goals in water quality are sediment, nutrients, and pathogens, especially from non-point discharges

© About three-quarters of water pollution in the U.S. comes from soil erosion, air pollution fallout, and agricultural and urban runoff

Surface waters in other countries

© At least 2.5 billion people in less developed countries lack adequate sanitation, and about half of these lack access to clean drinking water

© Sewage treatment in wealthier countries of Europe generally equal or surpass the U.S.

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

Surface waters in other countries

© 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