Point source pollution
Pollution that can be traced to a specific spot because it is DISCHARGED into the environment via pipes, sewers, etc.
Examples : Factory , waste water treatment plant
Non-source point pollution
Comes from many sources
- can be caused by rainfall or snow melt moving through or over ground
Examples : Agriculture fertilizer, run off, sediments from construction
-Urban streets, rural homes, suburban development, crop land, animal feeding lots
BOD
Biochemical oxygen demand
- Measures O2 Consumed
- indirect measurement of amount of organic pollutants in water
- bacteria act as organic matter in sewage water
- large amounts DO (dissolved oxygen) are used up rapidly
- LOW BOD = GOOD H20 QUALITY !
- To test BOD : 300 ml of H20 , standard bacteria, stoppered bottle, 5 days at 20 degrees C in the dark .
- DO is to be measured BEFORE AND AFTER.
What is LOW BOD a good thing?
It is good h20 quality because
- little oxygen demand from bacteria
- Bacteria demand oxygen when hey breakdown organic matter
- LOW CONTAMINATION in water
COD
Chemical oxygen demand
- amount of oxygen required to oxidize an organic compound to CO2 to H20
- Organic compound + H20 —> H20 + CO2 + Ammonia
- In order to reduce the organic compound, oxygen is REQUIRED.
- Measuring oxygen used for chemical reduction will INDICATE the AMOUNT of organic material
- Measurement in terms of TOTAL QUANTITY OF OXYGEN required for OXIDATION
- HIGHER value than BOD (Bacteria needs less oxygen to break down organic material than chemicals need to break down organic material)
- To TEST: 300 mL, heat reflux with dichromate (K2Cr2O7); Reduction of Cr+6 to Cr+3 (6 TO 3, basically remember REDUCING)
- indirect indicator of ORGANICS.
Aerobic bacteria
Requires FREE DO for growth
Oxidatively produces CO2 + H20 (respiration)
Mineralization of other elements (NO3- , PO43-, SO4-2)
Anoxic Bacteria
REQUIRES
Free DO and N for GROWTH!
Anaerobic bacteria
Grows in ABSENCE of free DO (Because its anaerobic)
Energy from breaking down complex organic substances
Reduce organic materials to CH4, NH3, H2S
Why are we concerned with BOD and/or COD in receiving water bodies?
Potential depletion of DO (dissolved oxygen) due to organic materials
What are the zones for urban runoff?
Clean zone Decomposition zone Septic zone Recovery zone Clean zone
Aka (CDSRC - crazy dinosaur singing romance choir - made this band up,but it works)
Clean zone
NO pollution
Normal organisms : trout, perch, bass, mayfly, stonefly
Decomposition zone
Polluted water ENTERS the stream
Trash fish : car, gar, leaches (hate leaches)
Septic Zone
Anaerobic ZONEEEEEEEE
Fish absent : fungi, sludge worms (google it, look how gross they are) , bacteria
Recovery zone
Less contamination present , INCREASE in DO and DECREASE in BOD (trash fish present)
BOD declines because most of organic material has settled as sludge
DO INCREASES
Second CLEAN ZONE
Normal water and organisms
After recovery zone
DO 8 ppm
Factors contributing to urban run off
Increase percent of impervious surfaces (concrete)
Decrease amount of percolation in soil
Increased amount of runoff from construction sites
Runoff rates depend on rainfall
Remediation solutions
Settling basins Recharge basins Interception of run off Porous materials Grassy channels
Settling basins
Pros : SS and BOD (some nutrients and toxins are absorbed)
Cons : system may be overwhelmed by storms and have short resistance time of 2-3 hours
Smaller particles will not be absorbed in that time
Recharge basins
Pros : slow percolation of water into the ground
Removes SS by SOIL
Cons: dissolved contaminates will percolate into groundwater
Interception of runoff
Pros : collect rainwater, clarifier, recharge ground water
Eutrophication
Enrichment of an ecosystem with chemical nutrients, typically compounds containing N, P or both in the form of nitrates and phosphates
Can occur naturally OVER TIME
stages of eutrophication
- Excess nutrients accumulate due to Natural N/ P cycling or unnatural wastewater discharge
- No longer constrained by limited nutrient availability , plants flourish
- Algae blooms due to excess nutrients, blocks sunlight penetrating the water
- Loss of light disallows plants below algae to conduction p/s resulting in drop in DO
- Plant life below algal blooms dies without sunlight and are decomposed by bacteria further lowering DO
- DO is so low that life is no longer possible in ecosystem
Sources of eutrophication
- Discharge of untreated municipal sewage (nitrates and phosphates)
- nitrogen compounds produced by cars and factories
- discharge of detergents (phosphates)
- inorganic fertilizer runoff (nitrates and phosphates)
- dishcharge of treated municipal sewage (primary and secondary treatment : nitrate and phosphates
- manure runoff from feedlots (nitrates, phosphates, ammonia)
- runoff from streets, lawns, and construction lots (nitrates and phosphates)
- dissolving of nitrogen oxides (from internal combustion engines and furnaces)
- runoff and erosion from cultivation, mining, construction and land use
