Groundwater Pollution (Chapter of Groundwater, Mc Connel site, last portion from CH. 16, Montgomery)

GROUNDWATER POLLUTION
Can groundwater be naturally polluted?
 
 

Pollution from Human developments
 
 

Point sources: Identifiable places from where pollutants are released
Non point sources: diffuse sources
             Combination of pollutants =>  treatment more difficult
 
 

Groundwater Pollution: passage source to aquifer is slow
    Well water testing needed.
         pollution from non point sources =         widespread
                                                                      $$$ to clean

Examples

•   landfills
•   septic systems
•   underground storage tanks
•   oil and gas wells
•   mines (coal and metals) => acid drainage
•   animal wastes
•   agricultural pollutants

Effects:      unknown for new products
                 cumulative
                 carcinogenic
                 make water unpalatable

Inorganic Pollutants
     Heavy metals:             Hg, Pb, Pu, Cd....
                        accumulate in organisms

(This from Montgomery, chapter 16)
Organic Matter         leaves, algae
                               animal (+ human) wastes

•   spreading of disease
•   Aerobic breakdown =>  uses O2
•   Anaerobic breakdown  => H2S, CH4, no O2 =>  no fish

•   Amount of O2 needed to breakdown org. matter contained in a body of water, aerobically.

 
•   Oxygen sag curve:  graph = Dissolved oxygen vs. distance from an org. waste source - Depletion =>  Recovery

 Eutrophication:  algal bloom caused by excessive amount of nutrients resulting from decay of organic matter (phosphates and nitrates)

•   Detergents add PO43-  =>    Not completely eliminated after

                                               treatment

Reversal of Damage - Groundwater
1) Stop / reduce input of pollutant
2) Let system recover naturally, monitoring
     Usually polluted G Water treated after extraction

In Situ Decontamination: specific for pollutant & site
Inorganic = heavy metals   Immobilization by precipitation
Organic:   biological decomposition by microorganisms
               (oxygen + nutrients can stimulate)
                Does not eliminate all organic comp. - Residue, taste, odor
Decontamination after extraction
 

WATER POLLUTION
REVIEW QUESTIONS
1)  Distinction between point sources and non point sources of pollution. Examples.
2)  Difficulties when dealing with groundwater pollution.
3)  Industrial pollution: scope of the problem.
4)  Inorganic pollutants: examples. Indicate the hazards the represent.
5)  Examples of organic pollutants.
6)  Organic matter as a pollutant: sources, problems. Define B.O.D. (biochemical oxygen demand). Oxygen Sag Curve.
7) What is the cause of eutrophication?.
8) Agricultural pollution
9) Methods to treat groundwater pollution.