with real-life, horrifying sea creatures on every slide
TRANSCRIPT
Dissolved OxygenThe concentration of oxygen in the water.Known as DOLowest amount needed for fish is 0.003g/dm3
Dissolved OxygenThe highest DO possible is 0.009g/dm3
Oxygen has low solubility because the diatomic molecule is non-polar.
Rivers have higher DO because of the rushing water, and can replace its DO faster.
BOD (IB Assessment)Biochemical Oxygen DemandIt’s the amount of oxygen (in ppm) needed by
bacteria to decompose organic waste in water at a specified time at a specified temperature (usually 5 days at 20⁰C).
A measure of pollution
BOD (IB Assessment)The higher the BOD, the more polluted the water
is, the more oxygen needed to oxidize the water. The more oxygen present in the water, the lower
the BOD should be. Fish (and other organisms) cannot survive in an
environment where the BOD is greater than the DO.
BOD TableBOD Quality of water
<1 Almost pure
5 Doubtful purity
10 Unacceptable purity
100-400 Sewage water
100-10,000 Water from meat-processing plant
Winkler MethodMethod to figure out the BOD.The water is saturated to its maximum amount of
DO.Bacteria is left in the water for five days in a
temperature of 25⁰C.The remaining oxygen is measured using
titration.
Aerobic vs. Anaerobic (IB Assessment)Aerobic Decomposition
Anaerobic Decomposition
Uses oxygen Oxidizes compounds
Does not use oxygenReduces compoundsCreates a bad smell
Decay ProductsElement Aerobic Decay
ProductsAnaerobic Decay Products
Carbon CO2 CH4
Hydrogen H2O CH4, NH3, H2S, H2O
Oxygen H2O H2O
Nitrogen NO3- NH3 and amines
Sulfur SO42- H2S
Phosphorus PO43- PH3
Eutrophication (IB Assessment) Addition of nutrients to the point of excess
(usually from fertilizers or acid rain).Overabundance of plants and algae. Due to overabundance, all the oxygen in the
water is used up, and the plants die. Creates a lot of organic matter to be
decomposed, raising the BOD.
Eutrophication (IB Assessment)Because of the lack of oxygen, anaerobic decomposition
takes place, creating bad smelling gases that poison the water.
Area dies completely from the lack of oxygen and poisonous compounds.
Calcium or aluminum ions can be used to remove the phosphates.
Nitrates are much harder to remove, reverse osmosis and ion exchange techniques are needed.
Thermal Pollution (IB Assessment)Water used for cooling in powerplants are
dumped into rivers, causing thermal pollution.Thermal pollution decreases the concentration of
oxygen.Thermal pollution increases metabolism,
increasing the amount of oxygen needed for respiration, and therefore increasing the BOD.
Thermal Pollution (IB Assessment)With a decrease in oxygen concentration and an increase in
the BOD, the environment cannot be supported, and anaerobic respiration takes place.
Sudden increase in temperature can disrupt life cycles such as reproduction, or just kill organisms (increasing the BOD).
Can be solved by trickling water through a porous material while blowing air in the opposite direction