Vern. Lecture 2 Flashcards
What are the key problems with coal mines?
- Large surface area of rock exposed from adits, shafts, fractures etc
- Minerals are water reactive
- Nature of pollutant generated will depend on whether mine is working or abandoned
What are the 5 main pollution sources in current mines?
Mines, washing plants, spoil heaps, coal stockpiles and all can discharge into groundwater
What are the four sources of pollution when mines are abandoned?
- Groundwater rebound
- Flushing of pollutants
- Activation of old discharge systems
- Old spoil heaps
What kind of pollutants are flushed out during groundwater rebound?
Products of pyrite decay caused by aerobic conditions
In what kind of environments are pyritic and non-pyritic coals formed?
Pyritic - coals from deltas and marginal peats
Non-pyritic coals - formed in river plains
What environmental problems are created by acidity?
Deposition of precipitates of iron hydroxide:
- Depletion of benthic flora
- Degradation of invertebrate and fish habitat.
- Low pH and elevated concentrations of metals (aluminium) toxic to fish and impact drinking water. E.g. coalfields in Durham
What elements does AMD remediation look to remove?
Iron, manganese, aluminium and sulphate.
What conditions does AMD remediation try to achieve?
Alkaline to raise pH
What methods of active remediation are there?
- Bactericides: Good for spoil heaps and in open cast coal quarries
- Pumping: fully effective but very expensive, e.g. Durham (cost 1 million/year)
- Engineered wastewater treatment technology
Describe the process of engineered wastewater treatment technology
Utilising oxidation (precipitates metals as hydroxides which then settle out of the water), settlement lagoons, then needs alkali dosing (addition of lime to neutralize generated acidity
List the advantages and disadvantages of 5 different methods of chemical treatments
Describe how an aerobic wetland can be used to treat pollutants
Describe how an anaerobic wetland can be used to treat pollutants
