Chapter 22

Water Pollution and Treatment

Water Pollution• Degradation of water quality

• Any biological, physical or chemical substance that, in an identifiable excess is known to be harmful to other desirable living organisms

• Heavy metals, sediment, radioactive isotopes, heat, coliform bacteria, phosphorus, nitrogen

Water pollution• US EPA has set limits on certain pollutants

(contaminants)

• Difficulties in determining effects of exposure to low levels of pollutants.

• Standards have been set for a small fraction of more than 700 identified drinking water contaminants.

Surface Water Pollution• Water Pollutants are emitted from

– Point Sources• Distinct and confined sources such as pipes from

industrial or municipal sources.

• Old sewage treatment systems

– Nonpoint Sources• Diffused and intermittent

• Ex) runoffs from streets, agriculture, mining, forestry.

• Difficult to monitor and control

Biochemical Oxygen Demand• The amount of oxygen required for

biochemical decomposition process

• When BOD is high the oxygen content is low, to support life.

• 3 zonesA pollution zone – BOD high

An active decomposition zoneDO reaches a minimum to

actively decompose

A recovery zone – DO increases

And BOD is reduced

Waterborne Disease• Outbreaks of waterborne diseases

– Milwaukee, WI – Cryptosporidium – 100 deaths

– Fecal Coliform Bacteria – 1998 Ga Water Park

– Walkerton, ON – E.Coli – Cow manure washed into water supply wells from heavy rains.

• 5 people died, 20 ICU, 500 ill – CUT BACKS IN TESTING

Nutrients

• Eutrophication– The process by which a body of water develops

a high concentration of nutrients – Phophorus or nitrogen

• Cultural Eutrophication– When eutrophication is accelerated by human

processes that add nutrients to a body of water• Fertilizers, detergents, sewage treatment plants

Eutrophication• A body of water develops a high concentration of

nutrients.• The nutrients cause an increase in the growth of

aquatic plants as well as photosynthetic blue-green bacteria and algae

• Algae may form surface mats, shading and reducing light to the algae below; reducing photosynthesis.

• Algae die and decompose, bacteria feed on the dead algae,BOD increases, oxygen is reduced. Other organisms die.

Acid Mine Drainage• Water with a high concentration of sulfuric

acid that drains from mines

• Serious water pollution problem

• Damages aquatic ecosystems, pollutes bodies of water and degrades water quality

Approaches to surface water pollution

• Reduce the sources of pollution– Most environmentally preferable way

• Treat the water to remove pollutant– Chlorination– Filtration– Settling Tanks– pH adjustments (Lime)– VOC removal – Nitrate removal

Groundwater Pollution• 50% of people in US

depend on groundwater

as a water source.

-Groundwater has always

been thought to be PURE

-Pollution sources can be

dumping chemicals, leaking

underground tanks, natural

occurring elements

Wastewater Treatment

• Septic Tank Disposal Systems

• Waste Treatment Plants– Primary Treatment– Secondary Treatment– Advanced Treatment– Chlorine Treatment

Wastewater Renovation and Conservation Cycle

• Steps:– 1. Return of treated wastewater to crops– 2. Renovation or natural purification by slow

percolation of the wastewater into soil to eventually recharge the groundwater resource with clean water

– 3. Reuse of the treated water

Water ReuseInadvertent: – water is withdrawn, treated and returned to the

environment

Indirect:– Ex) the wastewater renovation and conservation cycle

Direct:– The use of treated wastewater that is piped directly

from a treatment plant to the next user

Water Pollution and Environmental Law

• Environmental Law– The branch of law dealing with conservation

and use of natural resources and control of pollution