seawater - contains 97.2% of world's water, aka saline water  

• salinity - grams of salts per 1 kg of seawater
• salt, bromine, magnesium commercially extracted from seas
• desalination - removing salts from seawater
  • distillation - makes the salts precipitate out
  • reverse osmosis - extra pressure >> solvent goes towards more dilute side

freshwater - amount of oxygen = quality of water  

• 9 ppm of oxygen in fully saturated water
• aerobic bacteria uses oxygen to oxidize biodegradable materials
  • excess biodegradable materials >> bacteria uses up more oxygen for oxidation
  • not enough oxygen >> aerobic bacteria dies >> anaerobic bacteria take over
• eutrophication - increasing amount of dead/decaying plant matter

green chemistry - using chemical products that preserve the environment  

• preventing waste > cleaning up waste
• industries need as little waste as possible, waste shouldn't be toxic
• chemical processes need to be energy-efficient
• raw materials should be renewable
• no auxiliary substances used (or at the very least, harmless auxiliary substances)
  • solvents not consumed in reaction but released into atmosphere

water purification - water chlorination produces trihalomethanes (THM)  

• several THMs are carcinogens