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Water Pollution
Objective:Name, describe, and cite
examples of the eight major types of water pollution.
Types of Water Pollution
Water pollutants are divided into eight categories:
1. Sediment pollution2. Sewage3. Disease-causing agents4. Inorganic plant and algal nutrients5. Organic compounds6. Inorganic chemicals7. Radioactive substances8. Thermal pollution.
1. Sediment Pollution
Caused by soil particles that enter the water as a result of erosion.
Causes problems by reducing light penetration(turbidity), covering aquatic organisms, bringing toxic pollutants into the water, and filling in waterways.
1. Sediment Pollution
2. Sewage
Wastewater carried off by drains or sewers and includes water that contains human wastes, soaps and detergents.
Can carry disease causing agents Generates two serious problems – enrichment
and oxygen demand. Enrichment is the fertilization of the water. High BOD (Biological oxygen demand) for
microorganisms to break down the sewage.
2. Sewage
3. Disease-causing agents
Wastewater contains many bacteria, viruses, protozoa, parasitic worms, and other infectious agents that cause human and animal diseases.
Typhoid, cholera, bacterial dysentery, polio, and infectious hepatitis are some of the common diseases transmissible through water.
3. Disease-causing agents
E. coli is typically used as an indication of the amount of sewage present in water and as an indirect measure of the presence of disease-causing agents
The fecal coliform test is for E. coli. 1 bacterium : 100ml safe for drinking 200 b : 100ml safe for swimming. 2000b: 100ml safe for boating. 2x106b: 100ml raw sewage
3. Disease-causing agents
4. Inorganic plant and algal nutrients.
Fertilizer runoff is the major contributor of nutrients which include nitrogen and phosphorus to water.
Excessive growth of plants and algae disrupts the balance between producers and consumers.
Leads to other problems, including enrichment, bad odors, and high BOD.
4. Inorganic plant and algal nutrients.
Excess nutrients can lead to “dead zones” in water ways.
A condition called hypoxia occurs. There is not enough dissolved oxygen (DO) to support fishes, shrimp, or other aquatic organisms.
The largest dead zone reported was in the Gulf of Mexico.
4. Inorganic plant and algal nutrients
5. Organic Compounds
Most of the organic compounds found in water are synthetic chemicals produced from human activities.
pesticides, solvents, industrial chemicals, and plastics.
Most synthetic compounds are toxic. Some have been linked to cancer or birth
defects. Long term effects are relatively unknown.
5. Organic Compounds
6. Inorganic Chemicals
Most inorganic chemicals find their way into both surface water and groundwater from sources such as industries, mines, irrigation runoff, oil drilling, and urban runoff from sewers.
Some are toxic to aquatic organisms. Two common examples are lead and
mercury.
6. Inorganic Chemicals Lead
More than 10% of all municipal water supplies contain lead levels that exceed the safe limit.
Extra lead comes from corroding lead water pipes, lead soldering, pesticides, and fertilizers.
Mercury Settles in the
sediment, converted to methyl mercury compounds and readily enters the food chain.
Mercury accumulates in the muscles of aquatic organisms; reaching dangerous levels in top carnivores.
6. Inorganic Chemicals
7. Radioactive Substances
Enter the water from industries, mines and processing of radioactive minerals such as uranium and thorium.
Radon can temporarily dissolve in groundwater and them enter the air in your home.
8. Thermal Pollution
Occurs when heated water produced during certain industrial processes is released into waterways.
The rise in temperature has several effects: Chemical reactions, including the
decomposition of wastes, occurs faster. Less oxygen dissolves in warm water. Affects reproductive cycles, digestion rates,
and respiration rates of various organisms.
8. Thermal Pollution
Objective:Explain how humans
induce artificial eutrophication and
groundwater pollution.
Eutrophication
The enrichment of a lake or pond by excess inorganic plant and algal nutrients.
This can happen naturally however artificial or cultural eutrophicationis when enrichment is accelerated due to human activities such as excess sewage and fertilizer runoff.
Groundwater Pollution
Why are we concerned? About half of Americans obtain their drinking
water from ground water.
How is it contaminated? The most common way for groundwater to
become contaminated is by pollutants seeping into ground from landfills, underground storage tanks, backyards, golf courses, and agricultural lands.
Groundwater Pollution
Assumed that rock and soil purified water that reached the groundwater
Groundwater pollution cleanup is Very costly Takes many years Some cases, impossible.
Problem is compounded by
Injecting hazardous materials in deep wells.
Water Purification
Objective:Describe how drinking
water is purified in the U.S.
Water Purification
In the U.S., most water supplies are treated before being used so that water is safe to drink.
Step 1: If the water is turbid, it is treated with aluminum sulfate to cause the suspended particles to clump together and settle out.
Water Purification
Step 2: Water is then filtered through sand to remove particles and microorganisms.
Some systems have the water go through activated carbon granules to remove any organic compounds in the water.
Water Purification
Step3: The water is disinfected to kill any remaining disease-causing agents.
The most common way to disinfect water is by adding chlorine.
A small amount of chlorine is left in the water for protection during the distribution.
Other disinfection methods use ozone or ultraviolet radiation to kill disease-causing agents.
The Chlorine dilemma
The addition of chlorine to our water supply has undoubtedly saved millions of lives.
However chlorine has been linked to several kinds of cancer, increased risk of miscarriages, and rare birth defects.
We do not know the long term effects from low levels of chlorine in drinking water.
What are the options?
The Chlorine dilemma
Stop chlorinating. Could face a outbreak similar to what
happened in Peru when a cholera epidemic infected 300,000 people when they stopped chlorinating their water.
Filtering through activated carbon reduces the need for chlorine by 30%.
Use ozone or ultraviolet radiation but are many times more expensive than chlorine.
Wastewater Treatment
Objective: Distinguish among septic, primary, secondary, and tertiary
treatments for wastewater.
Municipal Sewage Treatment
Wastewater, including sewage, usually undergoes several treatments at a sewage treatment plant to prevent environmental and public health problems.
The treated wastewater is discharged back into the environment.
Primary Treatment
Involves removing the suspended and floating particles through mechanical processes.
The wastewater is screened and goes through gravitational settling.
Primary Treatment
The solid material that settles out is known as primary sludge.
Primary treatment does little to remove inorganic and organic compounds that remain suspended in the water.
Primary Treatment
If this was the only treatment, the water would be disinfected with chlorine and discharged into the environment.
Less then 10% of wastewater treatment facilities use primary treatment only.
Secondary Treatment
Uses microorganisms to decompose the suspended organic material in the wastewater.
This can be accomplished by two possible methods.
Trickling filters
Wastewater trickles through aerated rock beds that contain bacteria and other microorganisms.
These degrade the organic material in the water.
Activated Sludge Process Wastewater is aerated
and circulated through bacteria-rich particles.
The bacteria degrade suspended organic material.
After several hours, the particles and microorganisms are allowed to settle out, forming secondary sludge.
Secondary Sewage Treatment
Water that has undergone primary and secondary treatment is clear and free of organic wastes such as sewage.
About 60% of wastewater treatment facilities use both primary and secondary treatments.
Primary & Secondary Treatment.
Tertiary treatment
Even after primary and secondary treatment, wastewater still contains pollutants, such as dissolved minerals, heavy metals, viruses, and organic compounds.
Tertiary treatment uses a variety of biological, chemical, and physical processes.
Tertiary treatment
Is used to remove phosphorus and nitrogen from the water.
Also used to purify water that is reused.
About 30% of wastewater treatment facilities have all three levels of treatment.
What to do with the sludge?
Five possible ways to handle sludge: Anaerobic digestion – breakdowns
sludge, gives off methane, until it resembles humus and can be used as fertilizer.
Incinerated or dumped in landfills. Ocean dumping - banned in the U.S. in
1991.
Septic Systems
Used in private residences, typically in rural areas.
Set-up similarly to the primary and secondary treatments in a municipal sewage treatment.
Sewage is piped to a septic tank where particles settle to the bottom.
Septic systems
Grease and oils form a scum layer on the top that is decomposed by bacteria.
Septic systems
Wastewater containing suspended organic and inorganic material flows into a drain field where bacteria decompose the remaining organic matter in well-aerated soil.
Potential problems with septic.
Require care in order to operate properly. Use bleach or other strong chemicals
sparingly because they could kill the bacteria. Don’t overload the system with too much
organic matter.(I.e garbage disposals) The sludge from the septic tanks need
cleaned out every 2-5 years. Could contaminate soil or groundwater with
bacteria.
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