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, pathogenic bacteria

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.

• • •

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 zones A pollution zone – BOD high An active decomposition zone DO 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

•

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

Approaches to surface water pollution

• • Reduce the sources of pollution – Most environmentally preferable way Treat the water to remove pollutant – Chlorination – Filtration – VOC removal – Nitrate removal – Settling Tanks – pH adjustments (Lime)

•

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 Reuse

Inadvertent: – 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