Groundwater contamination can occur from various point and nonpoint sources. Point sources include storage tanks, landfills, and pipeline releases. Nonpoint sources include agricultural activities. Principal sources of groundwater pollution include municipal sources like sewer leakage and liquid wastes; industrial sources like liquid wastes, tank and pipeline leakage, and mining activities; agricultural sources like irrigation return flows, animal wastes, fertilizers and pesticides; and miscellaneous sources like urbanization, spills, stockpiles, septic tanks, and roadway de-icing. Pollutants can enter groundwater and persist for decades due to the difficulty of detecting and controlling subsurface pollution compared to surface water pollution.

1. GROUNDWATER
CONTAMINATION

2. GROUP MEMBERS
NAMITHA M.R. 2011-02-028
NIDHIN J.K. 2011-02-029
SAHLA N. 2011-02-030

3. POLLUTION
vs.
CONTAMINATION
 Pollution signifies any degradation of natural
ground water quality while contamination is
reserved for pollution that constitutes a hazard
to human health

4. POLLUTION OF GROUND WATER
 Defined as the artificially induced degradation
of natural groundwater quality
 Pollution can impair the use of water and can
create hazards to public health through toxicity
or the spread of disease

5.  In contrast with surface water pollution,
subsurface pollution is difficult to detect
and control, and may persists for
decades.
 Efforts are increasing to prevent, reduce
and eliminate water pollution

6. Pollution in relation to
water use
 The possible pollutants in groundwater are
virtually limitless
 The sources and causes of ground water
pollution are closely associated with human use
of water

7.  Ground water contamination scenarios :-
a. Point sources : Storage tanks, landfills,
pipeline releases etc.
b. Nonpoint sources: Agricultural activities
 Contamination originates from the disposal of
groundwater following its use for a wide variety of
purposes

9. SOURCES AND CAUSES OF
POLLUTION
 All sources and causes of pollution can be classified
as to their geometry
a. Point sources : Originates from a single location
b. Line sources : Predominantly linear arrangement
c. Diffuse sources : Occupies an extensive area

10.  Principal sources and causes of pollution with
regard to their occurrence:-
a. Municipal sources and causes
b. Industrial sources and causes
c. Agricultural sources and causes
d. Miscellaneous sources and causes

11. 1. Municipal sources and causes
a) Sewer leakage
 Sources: Poor workmanship, defective sewer
pipe, breakage by tree roots, ruptures from
heavy loads, earthquakes, loss of foundation
support etc.
 Results: Introduce high concentrations of
BOD,COD, nitrate, organic chemicals, bacteria
and heavy metals into groundwater

12. b) Liquid wastes
 Sources: Domestic wastes, Disposal wells
industries, storm, runoff etc.
 Results: Introduce bacteria, viruses, trace
elements and heavy metals, inorganic and
organic chemicals etc.

13. c) Solid wastes
 Sources: Landfills
 Results:
 Leachate from landfills can pollute groundwater
 Leachate include iron manganese, nitrate, trace
elements etc.

14. 2. Industrial sources and causes
a) Liquid wastes
 Sources: Industrial waste water discharged into
pits, ponds, lagoons etc.
 Results: Introduction of hazardous and toxic
industrial wastes into the groundwater

15. b) Tank and pipeline leakage
 Sources: Gasoline stations, fuel oil tanks,
petroleum and petroleum products from
industrial pipelines and tanks
 Results: Immiscible liquids like oil and petroleum,
liquid radioactive wastes etc. reaches the water
table and pollutes the groundwater

16. c) Mining activities
 Sources:-
 Coal, phosphate and uranium mines
 Stone, sand and gravel quarries
 Results: Low pH, increase in iron, aluminium
and sulphate content in the soil

17. d) Oil-field brines
 Sources:-
 Substantial discharges of wastewater in the
form of brine
 Constituents of brine include sodium, calcium,
ammonia, boron, chloride, trace metals and
high total dissolved solids
 Results: Groundwater become saline

18. 3. Agricultural sources and causes
a) Irrigation Return Flows
 Sources: Irrigation return flow drains to surface
channels or joins the underlying water
 Results:-
 Increases salinity of groundwater
 Increases the amount of bicarbonate, sulphate,
chlorides, nitrates etc. in the groundwater

19. b) Animal wastes
 Sources: Wastes from slaughter houses
 Results:-
 The natural assimilative capacity of the soil
become overtaxed
 Salts, organic loads and bacteria are transported
into the soil
 Nitrate-nitrogen is the most important persistent
pollutant that may reach the water table

20. c) Fertilizers and Soil Amendments
 Sources:
 Leachate of phosphate and potassium
fertilizers
 Leachate of soil amendments like lime,
gypsum and sulphur
 Results: Increases salinity of soil

21. d) Pesticides, insecticides and herbicides
 Sources: Leachate of pesticides, insecticides and
herbicides used in agricultural fields
 Results: Causes serious consequences in relation
to the portability of water

22. 4. Miscellaneous sources and causes
a) Urbanisation
 Groundwater pollution can occur both in rural
as well as urban areas and is affected by
differences in chemical composition, biological
and chemical reactions, density and distance
from discharge areas

23. b) Spills and Surface Discharges
 Causal activities includes leaks from pipes and
valves, uncontrolled waste disposal, intermittent
dumping of fluids on ground, flushing hazardous
and flammable liquids into water etc.
 Washing aircraft with solvents and spills of fuel at
airports can form a layer of hydrocarbons floating
on the water table.

24. c) Stockpiles
 Solid materials are frequently stockpiled
near industrial plants, construction site etc.
 Precipitation falling on unsheltered stockpiles
causes leaching of heavy metals, salts and other
pollutants into the groundwater

25. d) Septic tanks and Cesspools
 Septic tank: A watertight basin intended
to decompose the domestic sewage and to
discharge this into the biologically active zone
of the soil mantle through a subsurface
percolation system
 Cesspools: large buried chamber with porous walls
designed to receive and percolate raw sewage

26. e) Roadway de-icing
 Results from the application of de-icing salts to
streets and highways in winter
 Sodium chloride and calcium chloride are
generally used
 Salt reaches the groundwater in solution after
spreading on roadways and also from stockpiles

27. g) Interchange through wells
 Because wells form highly permeable vertical
connections between aquifers, they can serve as
avenues for groundwater pollution where
inadequate attention is given to the proper
construction, sealing or abandonment of wells

28. f) Saline water intrusion
 Salt water may invade freshwater aquifers to
create point or diffuse pollution sources
 Polluted surface water bodies that contribute to
groundwater recharge become sources of
groundwater pollution
g) Surface water

29. Attenuation of pollution
 Pollutants in groundwater tend to be
removed or reduced in concentration with
time and with distance travelled
 The rate of pollution attenuation depends on
the type of pollutant and on the local hydro
geologic situation

30.  Mechanisms involved include:-
 Filtration
 Sorption
 Chemical processes
 Microbiological decomposition
 Dilution

31. conclusion
 The principal sources and causes of groundwater
pollution can be categorized- municipal, industrial,
agricultural and miscellaneous
 With the growing recognition of the importance of
underground water resources, efforts are increasing
to prevent, reduce and eliminate groundwater
pollution.

32. THANK YOU 