5. Non-point Sources of Pollution
• As water from rainfall and snowmelt flows
over and through the landscape, it picks
up and carries contaminants from many
different sources.
• The polluted water ends up in streams,
lakes and the ocean.
• Water also carries pollutants into
underground drinking water as it soaks
into the ground.
14. Point Sources of Pollution
• Occur when harmful substances are
emitted directly into a body of water.
15. The main sources of pollutants are
sewage and industrial wastes.
• Pathogens - Disease causing
agents, e.g. bacteria and virus
• Organic wastes, e.g. animal
wastes
• Soluble inorganic chemicals --
acids, salts and heavy metals
• Suspended particles which make
the water looks cloudy and turbid
• Heat - Hot water released by
industrial and power plants
• Radioactive wastes
18. INCREASED WASTES
INCREASED POPULATION OF BACTERIA
THAT DECOMPOSE WASTE
INCREASED DEMAND FOR OXYGEN
DEATH OF AQUATIC ORGANISMS
INCREASED
NUTRIENTS
ALGAL BLOOMINCREASED WASTES
INCREASED POPULATION OF BACTERIA
THAT DECOMPOSE WASTE
INCREASED DEMAND FOR OXYGEN
DEATH OF AQUATIC ORGANISMS
25. 1. Primary Sewage Treatment
• Filtration of debris and suspended
solids
26. 2. Secondary Sewage Treatment
• Bacteria are used to remove up to 90%
of biodegradable wastes
27. 3. Advanced or Tertiary Sewage
Treatment
• a series of specialized chemical and
physical processes that remove
specific pollutants left in the water after
the previous treatments
Use of water resources Since 1950, the global rate of water use has increased almost 5 fold, to meet the need of growing population. Averaged globally, about 69% of the fresh water resource is used to irrigate 18% of the world's cropland. However, much irrigation is wasted; 70-80% of the water either evaporates or seeps into the ground before reaching crops. Another main use of water is energy production and industrial processing, making up about 23% of the total. Let see use of water in different countries, U.S. and China: http://www.ust.hk/~webpepa/pepa/ways_of_protection/water_general.html
comes from many diffuse sources. caused by rainfall or snowmelt moving over and through the ground As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. These pollutants include: Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas; Oil, grease, and toxic chemicals from urban runoff and energy production; Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks; Salt from irrigation practices and acid drainage from abandoned mines; Bacteria and nutrients from livestock, pet wastes, and faulty septicsystems; Atmospheric deposition and hydromodification are also sources of nonpoint source pollution http://www.epa.gov/owow/nps/qa.html http://www.protectingwater.com/
biological process in which aerobic bacteria are used to remove up to 90% of biodegradable wastes. Air are added to the tank to facilitate degradation of wastes by micro-organisms. The water then goes to a sedimentation tank where most of the suspended solids and micro-organisms settle out as sludge. http://www.ust.hk/~webpepa/pepa/ways_of_protection/water_general.html
