1. Heavy Metal Pollution

2. Introduction Release of toxic metal ions into water
Lead Pb2+, mercury Hg2+, cadmium Cd2+
Ions
Called Heavy Metals due to high RAM
Cumulative poisons
Concentrations build up in body on continuous exposure [over time]

3. Sources (i) Industrial effluent
(ii) Potential pollution from batteries of various kinds if not recycled
(iii) Pb2+ from the water pipes of old houses - especially if water is acid

4. Case Study Mercury metal Poisonous inhaled into lungs
Not poisonous if swallowed
Passes out in a few days
Inorganic mercury salts dangerous at high concentrations. E.g. HgCl2, Hg(NO3)2 etc.
Organic at low levels
Damage kidneys and intestine
Makes one “poco loco”. “Mad as a Hatter”

5. Minimata Bay Japan
Late 1950’s
Industrial waste discharged into bay
Hg salts got into food chain
High concentrations built up in fish
People ate a lot of fish
Caused birth defects and death
Called Minimata Disease

6. Removal Usually removed before discharge (i) Removed by precipitation
Pb Cl- = PbCl2(s)
(ii) Ion exchange

7. E U Limits
For levels of nitrate, phosphate and specific metal ions [2 examples]
Substance
Maximum admissible Concentration
Nitrates
50 mg / L
Phosphates
2.2 mg / L
Lead
Mercury
1 µg / L