Water and Its Pollution Lecture 9 Water and Its Pollution

A Glimpse Into Water’s Unique Properties Liquid water dissolves a variety of compounds - known as the universal solvent - is easily polluted by water-soluble wastes - in living organisms: carry dissolved nutrients; flush waste products

Main Uses of Water Domestic Use - domestic and municipal use account for 6 - 8% of worldwide withdrawals - improved water supply helps reduce diseases - humans are approx. 70% water

Main Uses of Water cont’d 2. Industrial Use - worldwide withdrawals of water for energy production & industrial processing is ~ 23% - most water is used for cooling & cleaning - it takes 100,000 gallons (380,000 litres) to make an automobile

Main Uses of Water cont’d 3. Agricultural Use - consumes the greatest quantity of fresh water - globally ~ 69% of the water withdrawn is used for irrigation - irrigation water efficiency is < 30%

Main Uses of Water cont’d 4. Transport - use of seas and rivers - e.g., river barges, freight ships

Main Uses of Water cont’d 5. Recreation / Tourism - use of seas and rivers - e.g., rafting, canoeing, snorkeling, swimming, river-boat casinos, scuba diving, cruise ships

WHERE IS OUR WATER STORED? Watershed - also called drainage basin or catchment area - areas of land that drain into bodies of water Surface Water - precipitation that does not soak into the ground or return to the atmosphere - forms streams, lakes, wetlands

Surface Runoff - water flowing off the land into bodies of surface water Groundwater - water that sinks into the soil and is stored in slow flowing and slowly renewed underground reservoirs - underground water

Groundwater Pollution groundwater is easy to deplete and pollute because it is renewed very slowly pesticides and nitrates are the most common contaminants pollution is caused from: landfills, underground storage tanks, hazardous waste dumps, leaking underground sewers, industrial-waste storage lagoons e.g. red mud lakes

Water Pollution Water is becoming scarce in some parts of the world & its quality is being degraded.

8 Principal Water Pollutants Sediment Inorganic Plant Nutrients Pathogens Organic Chemicals Inorganic Chemicals Radioactive Chemicals Thermal Pollution Sewage

1. Sediment (or suspended matter) insoluble particles of soil and other solids that are suspended in water occurs mostly when soil is eroded from land biggest water pollutant clouds water (lowers rate of photosynthesis)

2. Inorganic Plant Nutrients (excess nutrients) - come from soil erosion and human & animal waste water-soluble nitrates and phosphates can cause excessive growth of algae - causes eutrophication: over-nourishment of aquatic ecosystems with plant nutrients

3. Pathogens (disease-causing agents) - from sewage and livestock wastes - include disease-causing bacteria, parasitic worms, protozoa and viruses greatest cause of sickness and death in LDCs

4. Organic Chemicals / Compounds - include oil, gasoline, plastics, pesticides, cleaning solvents, detergents - threaten human health harm aquatic life

5. Inorganic Chemicals - consist of acids, salts & compounds of toxic chemicals, e.g., mercury, lead high levels can: · make water unfit to drink · harm aquatic life · depress crop yields · accelerate corrosion of equipment

6. Radioactive Chemicals can cause birth defects, cancer, genetic damage capable of being biologically amplified to higher concentrations as they pass through food webs e.g. DDT (Dichloro-Diphenyl-Trichloroethane) PCBs (Polychlorinated Biphenyls)

7. Thermal Pollution is an increase in water temperature that has harmful effects on aquatic life generally caused by heat that is absorbed by water used to cool electric power plants water temperature increase lowers oxygen content aquatic organisms more vulnerable to disease

8. Sewage & other oxygen demanding wastes organic wastes that an be decomposed by aerobic bacteria can lead to depletion of oxygen and death of aquatic life

Sources of Water Pollution Point Source - single, identifiable source that discharges pollutants into the environment - e.g., the drainpipe of a meat packing plant

Sources of Water Pollution cont’d Non-point Source - large or dispersed land areas, e.g., crop fields, streets & lawns, that discharge pollutants into the environment over a large area

MAIN SOURCES OF WATER POLLUTION Agriculture Municipal Waste Industrial Waste

AQUATIC ECOSYSTEMS UNDER THREAT

Coral Reefs the most threatened ecosystem in the coastal zone greatest threats come from eroded soil produced by: deforestation construction agriculture poor land management

Wetlands under severe human attack cut & converted to wood chips cut and drained for farmland & aquaculture ponds drained & dumped up for housing development

Oceans covers > 70% of Earth’s surface water evaporates as part of the water cycle mix and dilute many human-produced wastes to less harmful levels, if they are not overloaded affected by oil pollution

Sustainable Use of Water Conservation Recycling Rainwater harvesting Efficient sewage treatment Proper solid waste disposal Soil conservation Population control