Chapter 22 Water Pollution and Treatment Water Pollution

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 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

Approaches to surface water pollution • Reduce the sources of pollution – Most environmentally preferable way • Treat the water to remove pollutant – Chlorination – Filtration – Settling Tanks – p. H 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 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