potable water and waste water treatment

• is potable water safe to drink?

  yes
• Is potable water often pure?

  No
• What does potable waters pH have to be inbetween?

  6.5 and 8.5
• Potable water can contain dissolved substances
• What is surface water?

  Water from lakes, rivers and reservoirs
• What happens in filtration?

  a wire mesh screens out large twigs etc, and then gravel and sand beds filter out solids
• What happens in sterilisation?

  Water is sterilised to kill any microbes or bacteria.
• What chemicals are used in sterlisation?

  ozone, chlorine and UV light
• Distillation can be used to desalinate sea water
• Agricultural systems produce waste water from nutrient run-off from fields and slurry from animal farms
• Name the stages of sewage treatment in order.

  1. Screening
  2. sedimentation
  3. aerobic or anaerobic digestion
  4. released back into environment OR used as fertiliser or natural gas
• What happens in screening?

  large bits of material are filtered/removed
• What is sedimentation?

  Waste water stands in a tank and heavier solids (sludge) sink whilst lighter effluent floats to top
• What undergoes biological aerobic respiration?

  effluent
• What is biological aerobic respiration?

  air is pumped through water to encourage aerobic bacteria to break down organic matter
• Sludge is broken down by what?

  anaerobic respiration carried out by bacteria
• Anaerobic respiration that breaks down sludge produces what?

  methane gas
• Waste water containing toxic substances undergoes further treatment using chemicals, UV radiation or using membranes.
• The Haber process is used to make ammonia from hydrogen and nitrogen.
• Ammonia is used to make fertilisers