文档介绍：Chapter 5 Water Pollution
Classification of Water Pollutants
Thermal Pollution
Soil Erosion and Sediment Control
Stream Pollution
Lake Pollution
Groundwater Pollution
Ocean Pollution
Water Quality Standard
Clean Water Action Plan
Classification of Water Pollutants
Classified according to the nature of its origin:
Point source (点源):effluents from a pipe, channel, or any other confined and localized source
Dispersed (nonpoint) source (面源):broad, unconfined area from which pollutants enter a body of water/not at only one particular point
Surface runoff from agricultural areas
Acidic runoff from mining areas is a dispersed pollutant
Stormwater drainage systems in towns and cities
Distinction between point sources and dispersed sources of pollutants
Point source pollutants: easier to deal with than are dispersed source pollutants---collected and conveyed to a single point where they can be removed from the water in a treatment plant
Dispersed pollutants: much more difficult to control---the most effective way is to set appropriate restrictions on land use
Classified on their environmental or health effects
Domestic sewage: anism, oxygen-demanding substances, plant nutrients---conventional sewage treatment processes+advanced sewage treatment
Agriculture pesticide, industrial activity: anic and anic chemicals--- proper management of toxic and other hazardous wastes
Sediment: smothers benthic and disrupts the reproductive cycles of fish and other life forms---sedimentation
Oil
Heat
Radioactive substances
Thermal Pollution
Thermal pollution
Thermal enrichment
Cause: mainly from cooling water in power plants---increase by up to 15℃
Control: cooling pond or cooling tower (Figure )
Heat: dissipated into the air
Water: discharged to the water or reuse as cooling water
Natural draft hyperbolic cooling tower
Process: evaporation accounts for most of the heat transfer--Figure
Warm water: flows downward through the fill (vertical sheets or baffles)
Cool