Water Pollution Flashcards
Source of thermal pollution
Power station cooling/condensing water. Hot industrial processes
Effects of thermal pollution
Raising the temperature of water bodies above the range of tolerance for some organisms. Denaturing of enzymes above 40 degrees celsius. Reduction in dissolved oxygen as temperature rises leads to the death of organisms close to the lower end of their range. Increase in metabolic rate reducing energy for growth. Increased rate of development e.g. early egg hatching. Introduced species from warmer habitats. Reduced resistance to disease. Increase in pollutant toxicity as toxins are metabolised more rapidly.
Controls of thermal pollution
Cooling towers (always say this one first), forced draft cooling, cooling ponds
Cooling towers
A method of reducing the temperature of effluent water to reduce thermal pollution and deoxygenation. Warm water is passed through sprays to increase surface area. Heat energy is transferred to the surrounding cool air which rises and is dispersed to the atmosphere. Cool air is drawn in through grids at the base of the tower creating a continuous updraft of cool air. The shower spay also increases dissolved oxygen before water is returned to a local body of water.
Forced draft cooling
Forced Draft Cooling Towers are mechanical draft cooling towers that use fans to force cool air through the system. The airflow is introduced at the base of the tower and moves upward or horizontally to interact with the water, cooling it through direct contact and evaporation. Smaller than traditional cooling towers however require energy for the fans and can be noisy.
Sources of oil pollution
Shipping/oil tanker incidents, Oil exploration/drilling, oil rig incidents, oil pipeline damage, leakage from storage tanks, discharge of oil tank washing water from ships, vehicle engine oil leaks or discarded, industrial machine oil leaks
What naturally happens to oil in the environment?
Lighter fractions will evaporate, medium fractions will be digested by bacteria, heavier fractions will remain as tar balls for years. In open water oil spills will disperse in weeks. Oil spills cause most harm near shorelines and sensitive ecosystems.
Effects of oil pollution
Direct toxins such as benzine, asphyxiation due to oil covering, reduced photosynthesis due to lack of light, damage to birds feathers and insulating properties, reduced dissolved oxygen from the atmosphere due to oil film, reduced feeding and rearing of young due to increased preening, masking of smells that may be required for food or mates
Prevention of oil pollution by tanker operation
Improved navigation systems, use of GPS, Automatic Identification Systems, Improved shipping routes, The use of inert gas systems, improved tank washing procedures, improved oily waste disposal
Improved navigation systems to prevent oil pollution
The use of GPS and AIS to avoid collisions with other ships and the shore as well as grounding in shallow waters
Use of GPS to prevent oil pollution
Global Positioning System, a satellite based radio navigation system which can accurately pinpoint position in relation to a planned route or known hazards
Automatic Identification Systems to prevent oil pollution
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships. Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen or an electronic chart display and information system. AIS is intended to assist a vessel’s watchstanding officers and allow maritime authorities to track and monitor vessel movements.
Improved shipping routes to prevent oil pollution
Pre planned shipping routes where oil tankers in particular travel at a greater distance from the shore and sensitive ecosystems in order to allow more time to assist in the event of engine failure avoiding collisions with the shore.
The use of inert gas systems to prevent oil pollution
Filling empty fuel tanks with an inert gas such as exhaust gasses to avoid the explosive mix of fuel vapours and oxygen
Improved tank washing procedures to prevent oil pollution
Oil tanks were regularly washed with sea water to remove tar sludges and the water discharged into the sea. Oil is now recirculated in port and sludge removed with cargo.
Improved oily waste disposal to prevent oil pollution
Oily waste water is now unloaded at the oil terminal and oil can be separated from the water prior to discharge.
Prevention of oil pollution by tanker design
Double Hull, Twin engines/rudders/fuel tanks, separate oil and ballast water tanks
Double Hull to prevent oil pollution
All large tankers now have double hulls, two layers of steel between the oil and the sea with a gap of 2 metres. Oil is more likely to be contained within the inner hull upon damage to the outer hull.
Twin engines/rudders/fuel tanks to prevent oil pollution
Having pairs of essential equipment, reduces the chance of a ship drifting and colliding with the shore or other ships in the event of breakdown or failure.
Ballast water
As a ship offloads cargo or uses fuel it must take on ballast water in order to sit low enough in the water for the propeller and rudder to work properly
Separate oil and ballast water tanks to prevent oil pollution
In the past ballast water was carried in empty oil tanks and pumped back into the sea when no longer required carrying residual oil. Modern tankers have separate oil and ballast water tanks to avoid oil pollution.
Prevention of oil spills on land
Bund walls, oil interceptors, collection and recycling of industrial, engine and cooking oil
Bund wall to prevent oil pollution
A wall that surrounds a tank which would contain the contents if the tank leaks or bursts.
Oil interceptors to prevent oil pollution
used for drainage systems on major roads and car parks, oil flows from the surface into a separate oil tank whilst water flows from the base into drains