Water Pollution Flashcards
Factors affecting stream velocity:
gradient, discharge, and channel shape
Stream load is carried in three major ways:
Solution, Suspension, and Saltation
Solution (stream load)
dissolved particles (salts, ions)
Suspension (stream load)
particles are too small to settle quickly, so they ‘hang’ in the water (clay, silt, sand)
Saltation (stream load)
larger sediments that are too big to be lifted, so they bounce, roll, or are pushed along (pebbles, cobbles, boulders)
Watershed definition
The land area that delivers runoff sediment, and dissolved substances to a stream
point source pollutant definition and example
discharge pollutants from a single point. EX: industrial spill
non-point source pollution definition and example
scattered, diffuse sources. EX: crop land runoff
Cultural Eutrophication definition
Human induced input of inorganic plant nutrients into a body of water
Ecological sequence of cultural eutrophication
- inorganic plant nutrient overload
- during hot weather, phytoplankton populations explode and then die
- B.O.D. decreases as aerobic bacteria break down detritus
- Hypoxic conditions (low oxygen)
- fish kills
- anaerobic conditions
Sources of cultural eutrophication
- Discharge of untreated/treated municipal sewage (nitrates and phosphates)
- nitrogen compounds produced by cars and factories
- discharge of detergents (phosphates)
- dissolving of nitrogen oxides from internal combustion engines and furnaces
- natural runoff (nitrates and phosphates)
- inorganic fertilizer runoff (nitrates and phosphates)
- manure runoff from feedlots (nitrates, phosphates, ammonia)
- runoff from streets, lawns, and construction lots (nitrates and phosphates)
- runoff and erosion from cultivation, mining, construction, and poor land use
E. Coli is an indicator of what type of waste
human/animal waste
Safe Drinking Water Act (1974)
EPA determined levels that cause significant harm. MCL’s (maximum containment levels)
Clean Water Act (1972)
- set water quality standards
- established enforcement mechanisms
- established ongoing monitoring
- regulate discharge of pollutants (TMDL’s)
- reduced polluted runoffs from urban areas and animal feeding operations (section 319)
- Prevent wetland habitat destruction
- funding fro municipal waste water treatment
Components of raw sewage
- Debris and grit
- Particulate organic matter
- dissolved organic material
- dissolved inorganic material
Three steps of waste water treatment process
Primary, Secondary, and Advanced or Tertiary
Primary treatment - physical process:
- removal of debris and grit
- screening out of debris (through a bar screen)
- settling out of grit (in grit chamber - slow enough to allow grit to settle out as sludge)
- Fats and oils float to the top and can be skimmed off
Effectiveness of primary treatment
removes 60% of suspended soils, removes 30-40% of organic wastes, removes NO pesticides, 34 east coast cities only screen out large floatables
Secondary treatment trickling filter:
water filters through a bed of rocks, which hosts a community of decomposers and detritus feeders
secondary treatment activated sludge
water enters a large tank with an aerator and an inoculation of detritivores (activated sludge)
secondary treatment sedimentation tank
allows organisms to settle out of the water. Floc removal
secondary treatment removal effectiveness
95-97% of suspended solids and oxygen demanding organic wastes, 70% of most toxic metals, 70% of phosphorous, 50% of nitrogen
what does chlorination do?
- removes coloration
- kills disease carrying bacteria (e coli and cholera and giardia)
- may be hazardous to human/wildlife health
alternatives to chlorination:
UV light and ozone, but they’re costly
Advanced or Tertiary Sewage Treatment
- treats 5% of the wastewater in the U.S.
- chemical/physical processes
- specialized filters
- targets remaining pollutants - nitrates and phosphates
anaerobic digestion
produces a mixture of gases that is 2/3 methane - can be used for power. then the biosolids are converted to sludge cakes, 45% of which are fertilizer and 55% is dumped in landfills or incinerated
Combined Sewage Overflows (CSO’s)
- storm water combined with sewage
- 1200 US cities have combined sewage systems
- 40,000 overflows per year
Solutions to CSO’s
separate systems - expensive, 10 billion a year for a decade
smart growth - restoring riparian habitats and wetlands, rooftop gardens, and reducing hardscapes
