With real-life, horrifying sea creatures on every slide.

Dissolved Oxygen The concentration of oxygen in the water. Known as DO Lowest amount needed for fish is 0.003g/dm 3

Dissolved Oxygen The highest DO possible is 0.009g/dm 3 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 Demand It’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 Table BODQuality of water <1Almost pure 5Doubtful purity 10Unacceptable purity Sewage water ,000Water from meat-processing plant

Winkler Method Method 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 oxygen Reduces compounds Creates a bad smell

Decay Products ElementAerobic Decay ProductsAnaerobic Decay Products CarbonCO 2 CH 4 HydrogenH2OH2OCH 4, NH 3, H 2 S, H 2 O OxygenH2OH2OH2OH2O NitrogenNO 3 - NH 3 and amines SulfurSO 4 2- H2SH2S PhosphorusPO 4 3- PH 3

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

The End