Chapter 21:Water Pollution

21.1 Water Pollution Water pollution: the degradation of water

quality A pollutant is any biological, physical, or

chemical substance that is harmful to desirable living organisms

Water pollutants include… heavy metals, sediment, certain radioactive

isotopes, heat, fecal coliform bacteria, phosphorous, sodium, nitrogen, and pathogenic bacteria and viruses.

Pollutant Category Examples of Sources Comments

Dead organic matter Raw sewage, agricultural waste, urban garbage

Produces BOD and diseases

Pathogens Excrement & urine Recent cholera epidemics in Africa

Organic chemicals Pesticides, herbicides, industry that makes dioxin

Seep thru ground during planting

Nutrients Phosphorous, nitrogen from lead use (urban & agriculture)

Major cause of artificial eutrophication

Heavy metals Agricultural, urban & industry using mercury, lead, selenium, cadmium, etc.

Mercury from industrial processes discharged into water

Acids Sulfuric acid from coal and mines into groundwater

Acid mine drainage is major pollution problem

Heat (thermal pollution) Hot water from power plants Causes ecosystem distruption

Sediment Construction and agricultural runoff; natural erosion

Loss of soil resources, low water quality

Radioactivity Nuclear power industry, military, natural sources

Health effects vigorously debated

Agriculture: Most vegetation can tolerate a wide range of water quality, allowing for agricultural water to vary in physical, chemical, and biological properties.

Industrial Processes: The quality of water needed for industrial purposes varies widely depending on what the process involves; some processes need distilled water, or water with a specific quality.

Domestic (Household) Supply: Water in a domestic supply must be free of any materials harmful to health or household plumbing and appliances i.e. Insecticides, pesticides, pathogens, etc.

Major uses for water today:

21.1 Water Pollution Some pollutants may be a pollutant to one

environment, but not to others The primary problem with water pollution today

is a lack of clean, disease-free drinking water The U.S. treats drinking water before

consumption, eliminating most waterborne diseases, but in many other parts of the world this is not the case.

Major uses for water today include agriculture, industrial processes, and domestic supply.

Domestic Water Use: How safe is it?

Water for domestic use is drawn from surface and groundwater It is stored in reservoirs and ponds so solids and sediment settle increasing the

clarity All water must then be treated to meet national drinking water standards (see

p424) Next, the water is run through a water plant where it is filtered and chlorinated Once it reaches people’s homes it is treated even further through charcoal filters

in the tap Many people do not like to drink tap water because it runs through metal pipes

and contains chlorine, but the drinking water in the US is considered the safest in the world and the added chlorine is necessary because it eliminates waterborne disease

Although our drinking water may be the safest in the world, little is known of the long term effects of the minimal amounts of toxins that are contained in the water

These may be heavy metals and organic chemicals that require more research These concerns have caused the bottled water industry to become a multi-billion

dollar industry

21.2 Biochemical Oxygen Demand (BOD)

When there is dead organic matter in a stream, bacteria breaks it down using oxygen from the water

If there is too much bacterial activity due to dead material, the oxygen supply will deplete and make a zone inadequate to sustain life for other organisms

Therefore, a stream with a low enough oxygen level is considered polluted The Biochemical Oxygen Demand is the amount of oxygen required for the

biochemical decomposition process Scientists determine water quality by measuring the amount of oxygen

consumed by microorganisms as they break down organic matter in small samples

This is commonly practiced at wastewater treatment plants Dead organic matter comes from sources such as leaves falling off a tree,

agricultural runoff, and runoff from urban sewage An example of too much organic matter going into a body of water at once is

a sewage treatment plant that overflows from storm runoff and runs off into streams untreated

This could cause the oxygen supply to become too low to support life in the water This also causes three zones to form in the water

1) pollution zone: High BOD 2) Active decomposition zone: dissolved oxygen content reaches a minimum due to rapid

decomposition 3) recovery zone: dissolved oxygen increases and BOD is reduced

http://www.youtube.com/watch?v=4vFD6fCMDTA

Sources and Processes of Water Pollution:

• An increasing population often results in increases pollutants in the environment.

• The U.S. Environmental Protection Agency has set thresholds on water pollution levels for some pollutants. If the pollutant is present in a greater concentration that the threshold the water in unsuitable for use.

Surface Water Ground Water

Urban Runoff Leaks from waste disposal sites

Agricultural Runoff Leaks from buried tanks and pipes

Accidental spills of chemicals

Seepage from agricultural activities

Radioactive materials Saltwater intrusion into coastal aquifers

Runoff from industrial sites

Seepage from cesspools and septic systems

Leaks from storage tanks/pipelines

Seepage from acid-rich water from mines

Sediment from sources ie. Agricultural lands and construction sites

Seepage from mine waste piles

Air fallout into rivers, lakes, and oceans

Seepage from pesticides, herbicide nutrients, etc.

Seepage from accidental spills

Inadvertent seepage of solvents and chemicals from industrial sites.

21.9: Groundwater Pollution

Groundwater- water found beneath the Earth’s surface within the zone of saturation under the water table

Almost 50% of Americans’ drinking water comes from groundwater

This concerns environmentalists; groundwater can be easily polluted by hard-to-detect toxins Only a small portion is known to be contaminated, but as

groundwater contamination testing is becoming more commonplace, we’re finding higher proportions of contaminated groundwater

Causes of Groundwater Pollution

Increasing human population increases stress on groundwater supply

Runoff from precipitation Road salts, oil, fertilizers, pesticides

Waste disposal sites in the US are producing chemical plumes that migrate into the groundwater Approx. 75% of 150,000 sites suspected of this

http://www.youtube.com/watch?v=5xs1jLlbztE

5 Principles of Groundwater Pollution

Some pollutants, like gasoline, are lighter than water; float on the groundwater

Some pollutants have 3 phases: liquid, vapor and dissolved. Dissolved phases chemically combine with groundwater. Ex: salt

dissolves in. Some pollutants are heavier than water, and sink downward

thru the groundwater Particulates, cleaning solvents

Treatment must address physical and chemical properties of the pollutant

Ex: extraction well for gas because gas floats on water Emphasis should be placed on prevention of pollution instead

of clean up (cheaper, less environment damage)

Treatment Options Bioremediation – A method of treating

groundwater pollution problems that utilizes microorganisms in the ground to consume or break down pollutants

Vapor extraction system A well pump extracts vapor from gasoline

underground before it affects water in homes Removal and disposal of soil (near contaminated

areas) Very expensive; big environmental consequences

› Case Study: Long Island

Nassau county: groundwater pollution caused by saltwater infiltration and shallow aquifer contamination

Shallow-aquifer pollution associated with urbanization Urban runoff, household sewage from cesspools and

septic tanks, salt (for de-icing highways) and industrial and solid waste

Pumping of groundwater over the past 15 years has led to declining water levels As groundwater is removed from coast, subsurface

outflow to ocean decreases, allowing salt water to migrate inland

Saltwater Intrusion

21.10 – Wastewater Treatment

When used for industrial or municipal purposes, water is often degraded

Wastewater Treatment – Process of treating wastewater (primarily sewage) in specially designed plants that accept municipal wastewater. Generally divided into three categories: Primary treatment, secondary treatment, and advanced waste-water treatment

21.10 – Wastewater Treatment

Conventional Methods: Septic tank disposal systems in rural areas Centralized water treatment plans in cities

Recent innovative approaches: Application of wastewater to the land Wastewater renovation and reuse

21.10 – Septic Tank Disposal Systems

In rural areas, there is no central sewage systems or wastewater treatment facilities available

Result: individual septic tanks By law, an evaluation is needed for the site

of a potential septic tank

21.10 – Primary treatment Incoming raw sewage enters the plant’s

sewer line Sewage then enters the grit chamber Then enters the primary sedimentation tank Sludge is removed and transported to the

digester for further processing Removes 30 to 40% of BOD

21.10 – Secondary Treatment

Most common method of secondary treatment is activated sludge

Wastewater from primary sedimentation tank enters the aerotation tank

Waste water mixed with air Enters the final sedimentation tank, sludge settles

out Treated by anaerobic bacteria Discharged to a river, lake, or ocean Removes about 90% of BOD

21.10 - Advanced Wastewater Treatment

Primary and secondary treatment do not remove all pollutants from incoming sewage

Additional pollutants can be removed by adding more steps of treatment

The treated water is released into the surface water and can be used for irrigation or municipal properties

Advanced wastewater treatment is used when it is important to maintain good water quality

21.10 – Chlorine Treatment Chlorine is frequently used to disinfect water in the process

of wastewater treatment It’s very effective in killing the pathogens that have

historically caused outbreaks of serious waterborne diseases It has been recently discovered that chlorine treatment

produces very small quantities of chemical byproducts Some of these are potentially hazardous to humans and

animals How much of a risk these chemical byproducts are is a

matter of debate and is rather controversial However, evidence suggests that these byproducts create a

risk of cancer and other possible side effects

21.11 Land Application of Wastewater

Wastewater renovation and conservation cycle - First is returns treated water to crops via irrigation systems, then it naturally purifies water wastewater through percolation (renovation), and lastly it reuses the treated water.

21.11 Land Application of Wastewater

Resource recovery wastewater treatment plant- Both environmentally preferred and economically viable. It uses methane gas as fuel.

How it Functions- First wastewater is run through filters, then it is put through anaerobic processing, and finally the nutrient rich water is run over an incline and onto plants.

21.11 Land Application of Wastewater

Wastewater and wetlands Treating wastewater through wetland systems is

attractive to communities that find it difficult to purchase wastewater treatment plants.

Louisiana applies nitrogen and phosphorus rich wastewater to wetlands and increases plant production/ improves water quality.

Arizona constructed artificial wetlands that contain bacteria that reduce Nitrate concentration in the wtaer.

21.12- Water Reuse Water reuse can be inadvertent, indirect, or direct Inadvertent- water is withdrawn, treated, used,

treated, and returned to the environment, followed by further withdrawals and use

Millions depend on it who live near large rivers Risks- poor treatment= poor water quality Diseases or viruses may develop before or after

treatment, making potential health risks New diseases may form

Indirect water reuse Planned water usage US used several thousand cubic meters of

treated wastewater per day to be applied to surface recharge areas

Treated water enters ground water storage to be reused for agricultural and municipal purposes

Direct water reuse Treated water is pumped directly from a treatment plant

to the next user Used in agriculture, industry, irrigating golf courses, on

institutional grounds, and parks Growing rapidly Las Vegas hotels use water from rivers, fountains, canals,

and lakes (required to treat and reuse waste water) Little direct use of water is used for human consumption

(except in emergencies) because of risks and negative cultural attitudes toward using treated water

21.13 Water Pollution and Environmental Law

Environmental Law- branch or law dealing with conservation and use of natural resources and control of pollution

In the US, laws at the federal, state, and local levels address these issues

First federal law to protect water resources- Refuse Act of 1899 = protected navigable streams, rivers, and lakes from pollution

Many federal laws have been passed to clean up or treating pollution problems or treating wastewater.

Also, there has been a focus on preventing pollutants from entering water

Prevention has the advantage of avoiding environmental damage and costly cleanup/treatment

Water Laws 1990’s was a time of debate in the US over water pollution. US tried to rewrite the Clean Water Act in 1994 to give

industry more flexibility to comply with environmental regulations with water pollution

Gov. saw this as a way to save money without causing environmental degradation

Environmentalists saw it as a step backwards to cleaning up water resources.

Congress was wrong; people are willing to pay more for clean water

Unfortunately, congress continues to debate and little has been resolved

In 2000, the US president aimed to protect thousands of streams and lakes from nonpoint agricultural, industrial, and urban pollution sources.

This will be enforced by the Environmental Protection Agency, which will work with local communities and states to develop plans to reduce pollution in streams, lakes, and estuaries

Problems- It is difficult to regulate, it will take 15 years to implement completely, and it has been opposed by Congress, agricultural groups, the utility industry, and the US Chamber of Commerce.

Main objections- it is costly (billions of dollars) and that local and state gov’ts are better suited to control their own water pollution regulations

The god news is that these regulations mark a new phase in water pollution control in the US

Water Laws