Ground Water Pollution

Characteristics of ground water

• Definition:
– Groundwater is water that exists in the pore spaces
and fractures in rock and sediment beneath the
Earth's surface.
– It originates as rainfall or snow, and then moves
through the soil into the Groundwater system, where
it eventually makes its way back to surface streams,
lakes, or oceans.
– Groundwater is a long-term reservoir of the natural
water cycle, as opposed to short-term water
reservoirs like the atmosphere and fresh surface
water.
Characteristics of ground water
• Definition:
– Groundwater is often contained in aquifers: an
underground water saturated stratum of formation that
can yield usable amounts of water to a well.
– There are two different types of aquifers based on physical
characteristics:
• if the saturated zone is sandwiched between layers of
impermeable material and the Groundwater is unfed pressure, it is
called a confined aquifer;
• if there is no impermeable layer immediately above the saturated
zone, it is called an unconfined aquifer. In an unconfined aquifer
the top of the saturated zone is the water table as defined above.
Usually an aquifer can produce an economically feasible quantity
of water to a well or spring. A saturated region that, due to lower
hydraulic conductivity, does not yield a sustainable amount of
water in an economic fashion is called aquitard.
Characteristics of ground water
– Typically, groundwaters have a steady flow
pattern.
– Some of the most typical characteristics of
groundwater are weak turbidity, a constant
temperature and chemical composition and
almost overall absence of oxygen.
– Furthermore, groundwater is often very pure
microbiologically.
Characteristics of ground water
• Quantity of groundwater on the earth
– On the earth, approximately 3% of the total water is
fresh water. Of this groundwater comprises 95%,
surface water 3.5% and soil moisture 1.5%.
• Out of all the fresh water on the earth, only 0.36% is readily
available to use (Leopold, 1974).
• Groundwater is an important source of water
supply. 53% of the population of US receives its
water supply from groundwater sources.
• Groundwater is also a major source of industrial
and agricultural uses.
A map of groundwater distribution on the earth
Characteristics of ground water
Characteristic Surface Water Ground Water
Temperature varies with season relatively constants
Turbidity, SS Level variable, sometimes high Low or nil (except in karst soil)
Due mainly to SS (clays, algae) except
Colour in very soft or acidic waters (humic Due above all to dissolved solids
acids)

Largely constant, generally

Mineral content Varies with soil, rainfall, effluents, etc. appreciably higher than in
surface water from the same area

Divalent Fe and Usually none, except at the bottom of

lakes and ponds in the process of Usually present
Mn in solution eutrophication
Aggressive CO2 Usually none Often present
Often near saturation level, absent in
Dissolved O2 Usually none
very polluted water
Characteristics of ground water
Characteristic Surface Water Ground Water
H2S Usually none Often present
NH4 Found only in polluted water Often found
Nitrates Level generally low Level sometimes high
Silica Usually moderate proportions Level often high
Mineral and
Can be present but liable to disappear Usually none but any accidental
organic
rapidly once the source is removed pollutionlasts a very long time
micro-pollutants
Living organisms Bacteria, viruses, plankton Iron bacteria frequently found
Chlorinated
Rarely present Often present
solvents
Eutrophic nature Often. Increased by high temperatures None
Ground water pollution
• Groundwater, under most conditions, is safer and more
reliable for use than surface water.
– Part of the reason for this is that surface water is more
readily exposed to pollutants from factories, for example,
than groundwater is.
• This by no means says that groundwater is invulnerable
to contamination. Although it is not as vulnerable as
surface water, contaminates can still reach wells and
therefore households then. Any chemicals that are
easily soluble and penetrate the soil are prime
candidates for groundwater pollutants.
Ground water pollution
• Groundwater is also affected by water
engineering: for decades and centuries,
through improper disposal of wastes to the
environment and subsurface areas many
groundwater have become contaminated.
• Efforts to protect the quality and quantity of
groundwater have been made by cooperation
between all government agencies, industrial
parties and researchers
Ground water pollution
• A potential pollution problem can still reach a
well miles away through underground water
currents.
– For example, a chemical that spills at an industrial
plant miles away, could infiltrate the ground and
eventually enter the aquifer system that an entire
community uses for their private wells. This
situation could have devastating effects: once
groundwater is contaminated, it is an extremely
costly operation to remove the contaminate.
Ground water pollution
Sources of groundwater contamination
• Groundwater contamination occurs when man-made
products such as gasoline, oil, road salts and chemicals
get into the groundwater and cause it to become
unsafe and unfit for human use.
• Materials from the land's surface can move through
the soil and end up in the groundwater.
– For example, pesticides and fertilizers can find their way
into groundwater supplies over time.
• Road salt, toxic substances from mining sites,
• Used motor oil also may seep into groundwater.
• In addition, it is possible for untreated waste from
septic tanks and toxic chemicals from underground
storage tanks and leaky landfills to contaminate
groundwater.
Sources of groundwater contamination

(rate of breakdown is extremely slow in ground

water)
• Industrial waste into aquifer recharge zone
• Surface runoff into abandoned wells—
Industry, agriculture, household
• Leaking underground storage tanks of gas
stations
• Leaking septic tank into recharge area.
• Injection wells for secondary recovery.
Sources of groundwater contamination
Causes of GW contamination

 Storage tank
 May contain gasoline, oil, chemicals, or other types
of liquids and they can either be above or below
ground.
• There are estimated to be over 10 million storage tanks
buried in the US and over time the tanks can corrode,
crack and develop leaks.
If the contaminants leak out and get into the
groundwater, serious contamination can occur.
Causes of GW contamination

Storage tank
TRANSPORT AND TRANSFER SPILLS
Causes:
- Accidents.
- Inadequate maintenance.
- Lack of proper training.
- Inadequate provisions for spill
containment.
Causes of GW contamination
UNDERGROUND STORAGE TANKS

• Contamination Evidence:
- Petroleum odor in wells or
basements.
- Tank inventory losses.
- Spills.
- Detection of leaks.

• Causes:
- Corroded tanks.
- Poor installation and/or
maintenance.
- No testing for tank leaks.
- Poor inventory control.
- No leak backup containment.
- Deterioration of abandoned tanks.
Causes of GW contamination
 Septic tank
 Onsite wastewater disposal systems used by homes, offices
or other buildings that are not connected to a city sewer
system.
 Septic systems are designed to slowly drain away human
waste underground at a slow, harmless rate.
 An improperly designed,
located, constructed, or
maintained septic system can
leak bacteria, viruses,
household chemicals, and
other contaminants into the
groundwater causing serious
problems.
Causes of GW contamination
• Small disposal pits
– Used for dumping or burning wastes by businesses and
households…
– Petroleum odor in well water.
– Improper disposal of chemicals, oil, pesticides, other wastes and
used containers.
– Lack of disposal facilities for small amounts of hazardous wastes.
Causes of GW contamination
• Small disposal pits
– Improper use of storage.
– Improper disposal in backyard, ditches, low ground, septic
systems, and overgrown ditches
Causes of GW contamination

Uncontrolled Hazardous Waste

– Hazardous waste sites can lead to groundwater
contamination if there are barrels or other
containers laying around that are full of hazardous
materials.
• In the U.S. today, there are thought to be over 20,000
known abandoned and uncontrolled hazardous waste
sites and the numbers grow every year.
– If there is a leak, these contaminants can
eventually make their way down through the soil
and into the groundwater.
 Uncontrolled Hazardous Waste

Contamination Evidence
- Spills.
- Detection of chemical solvents,
metals, nitrates, or other chemicals
in well water tests.

Causes:
- Improper storage, handling, use,
and disposal.
- Spills.
- Leaks.
Causes of GW contamination
 Landfills (the places that
our garbage is taken to be
buried)
• Landfills are supposed to
have a protective bottom
layer to prevent
contaminants from
getting into the water.
• However, if there is no
layer or it is cracked,
contaminants from the
landfill (car battery acid,
paint, household
cleaners, etc.) can make
their way down into the
groundwater.
Causes of GW contamination

 Landfills
• Causes:
- Lack of control over
leachate.
- Permeable soil.
- Leaky landfill cover.
- No liner or liner
failure.
- Poor Management.
- Lack of control over
hazardous wastes
disposal.
Causes of GW contamination

Chemicals and Road Salts

– The widespread use of chemicals and road salts is another
source of potential groundwater contamination.

– Chemicals include
products used on
lawns and farm
fields to kill weeds
and insects and to
fertilize plants, and
other products
used in homes and
businesses.
Causes of GW contamination
 Chemicals and Road Salts
– When it rains, these chemicals can seep into the ground and
eventually into the water.

– Road salts are used in

the wintertime to put
melt ice on roads to
keep cars from sliding
around. When the ice
melts, the salt gets
washed off the roads
and eventually ends up
in the water.
Causes of GW contamination

FERTILIZERS
Contamination Evidence:
- High nitrate level in well water tests.

Causes:
- Over fertilization.
- Ill-timed application.

LAND APPLICATION OF SLUDGES

AND WASTE WATER
Contamination Evidence:
- High bacteria, nitrate levels in well
water tests.

Causes:
- Improper application methods.
- Inappropriate soils for application.
Causes of GW contamination
INACTIVE MINING SITES
Contamination Evidence:
- (Potential) Dumping of wastes in inactive
mining pits.

Causes:
- Rapid infiltration of contaminants due to loss
of topsoil filtering capacity.
Causes of GW contamination
WELL: potential pathways for contaminants to enter groundwater...
Contamination Evidence:
- Detection of high bacteria levels in well water tests.
- Well water turbidity.
- Detection of other contaminants in well water tests.

Causes:
- No well casing or leaky casing.
- Well cover not watertight.
- Open abandoned wells.
- Groundwater movement from
contaminated to uncontaminated wells.
Causes of GW contamination

Atmospheric Contaminants
– Since groundwater is part of the hydrologic cycle,
contaminants in other parts of the cycle, such as
the atmosphere or bodies of surface water, can
eventually be transferred into our groundwater
supplies.
Pathway GW pollution
• How does groundwater become contaminated?
– Depending on its physical, chemical, and biological
properties, a contaminant that has been released
into the environment may move within an aquifer in
the same manner that ground water moves.
Pathway GW pollution
• The major contaminant transport mechanisms in
groundwater are advection, diffusion, dispersion,
adsorption, chemical reaction, and
biodegradation.
– Advection is the movement of contaminant(s) with
the flowing groundwater at the seepage velocity in
the pore space and is expressed as Darcy's law.
– Diffusion is a molecular-scale mass transport process
that moves solutes from an area of higher
concentration to an area of lower concentration.
Diffusion is expressed by Pick's law.
– Dispersion is a mixing process caused by velocity
variations in porous media. Mass transport due to
dispersion can occur parallel and normal to the
direction of flow with two dimensional spreading
Pathway GW pollution
• Sorption is the interaction of a contaminant with
a solid. It can be divided into adsorption and
absorption. An excess concentration of
contaminant sat the surfaces of solids is called
adsorption. Adsorption refers to the penetration
of the contaminants into the solids.
• Biodegradation is a biochemical process that
transforms contaminants (certain organics) into
simple carbon dioxide and water by
microorganisms. It can occur in aerobic and
anaerobic conditions. Anaerobic biodegradation
may include fermentation, denitrification, iron
reduction, sulfate reduction, and methane
production.
Pathway GW pollution

Schematic diagram of highlighting Causes and pathways for groundwater pollution

by EOCs

-To date the vast majority of published studies have focussed on groundwater
contamination by EOCs from point sources
-The data are divided on the basis of major sources; agricultural waste (from waste
lagoons and biosolids), landfill, septic tanks, waste water (industrial and municipal).
Seawater intrusions in groundwater
– Seawater intrusion is the movement of seawater into fresh
water aquifers due to natural processes or human activities.
– Seawater intrusion is caused by decreases in groundwater
levels or by rises in seawater levels.
– When you pump out fresh water rapidly, you lower the
height of the freshwater in the aquifer forming a cone of
depression.
– Use of salt for highways de-icing is another source of
contamination
– The salt water rises 40 feet for every 1 foot of freshwater
depression and forms a cone of ascension.
– Intrusion can affect the quality of water not only at the
pumping well sites, but also at other well sites, and
undeveloped portions of the aquifer.
Seawater intrusions in groundwater
Seawater intrusions in groundwater

• High concentrations of chloride can make water unfit

for human consumption and for many industrial uses,
but the human health-related problems have not been
carefully observed yet.
• High concentration of chlorine has bad effects on the
environment as well:
– it can produce leaf burn and even defoliation in sensitive
crops;
– in lakes can increase the presence of metals in waters and
prevent the distribution of oxygen and nutrients and thus
harm aquatic life.
• High concentrations of sodium ion can contribute to
certain heart disease or high blood pressure,
particularly in susceptible individuals.
Nitrates pollution in groundwater
– Natural nitrate levels in groundwater are generally
very low (typically less than 10 mg/l NO3),
• Nitrate concentrations grow due to human
activities: agriculture, industry, domestic effluents
and emissions from combustion engines
• Runoff from fertilizers is the most common
source of nitrates, but they may also come from
improperly disposed sewage, leaking septic
systems, industrial waste, food processing waste,
and erosion of natural deposits.
Nitrates pollution in groundwater
• The sources of nitrates pollution in groundwater are:
– cultivation in areas where the soil layer is relatively thin, or
has poor nutrient buffering capacity, or where there are
changes in land use;
– over fertilization of crop for intensification of agricultural
activity;
– spread cultivation of crops which require high fertilizes
doses and which leave the soil bare over long periods
(maize, tobacco and vegetables);
– drainage systems which lead to drainage of fertilizers;
– intensive agricultural rotation cycles involving frequent
ploughing and extensive areas of bare soils during winters;
– organic fertilizers form animal husbandry;
– increased urbanization.
Arsenic in groundwater
• The Arsenic limit in drinking water advised by EU
and WHO and quoted in standards is 0.01 mg/l.
• Arsenic can occur in the environment in several
forms but in natural waters, and thus in drinking-
water, it is mostly found as trivalent arsenate
(As(III)) or pentavalent arsenate (As (V)).
• Environmental sources of arsenic stem from the
continuing use of its compounds and pesticides,
from its unintended release during the mining of
gold and lead and from the combustion of coal,
of which it is a contaminant.
• Industrial effluents also contribute arsenic to
water in some areas
Iron in groundwater
• Iron in rural groundwater supplies is a common
problem:
– its concentration level ranges from 0 to 50 mg/l, while
WHO recommended level is < 0.3 mg/l.
• Iron levels in groundwater can be increased by
dissolution of ferrous borehole and handpump
components
• Iron-bearing groundwater is often noticeably:
orange in colour, causing discoloration of laundry,
and has an unpleasant taste, which is apparent in
drinking and food preparation.
CASE STUDY
ARSENIC CONTAMINATION IN
GROUNDWATER OF VIETNAM
Arsenic pollution in GW
• Arsenic contamination has been recognised in
the Red River delta in 1998
Arsenic concentrations in GW
of Hanoi area varied from 1 to
3050 μg/L (average 159 μg/L)
in the upper aquifer
Arsenic pollution in GW
Arsenic pollution in GW

The results imply that some

three million people are
currently using groundwater
burdened with As
concentrations >10 μg/L and
one million people use
groundwaters containing >50
μg/L, with both rural and
urban populations being
affected by toxic levels of As.

Arsenic concentrations in groundwater

collected in the period from 2005 to 2007.
Arsenic pollution in GW

Arsenic conc. are lowered in

the plants of Hanoi through
the iron removal process, but
partly remain at critical levels:
- 50% above the Vietnamese
standard of 50 μg/L
- 100% above the WHO
guideline of 10 μg/L.
Arsenic pollution in GW

Depths between 0 and 50 m

Arsenic pollution in GW

Risk of As pollution plotted in three dimensions and at

10 m depth intervals
Arsenic pollution in GW

As concentrations in Pleistocene aquifers of the Red River Delta at depths >50 m. (A),
Highest As concentrations (up to 330 μgL−1) in the Pleistocene aquifer are found in the
same area where high As concentrations are present in shallower
Arsenic pollution in GW

The real arsenic contamination in

tubewells’ water in Van Phuc
village
High variations of arsenic levels are
observed over short distances
Pathway of arsenic to GW

Simplified illustration of the widely accepted theory on the origin of arsenic in

groundwater of river deltas
Affected by arsenic poisoning
• Arsenic concentrations of 50 μg per litre of water
were shown to cause chronic health problems if
such water is consumed over a period of 5–10
years (SMITH et al. 2000).
• Development of the disease is strongly
dependent on exposure time and arsenic
accumulation in the body, whereas age,
nutritional habits and lifestyle of the exposed
person may also have an influence on the
occurrence of health problems (HUGHES 2002;
YOSHIDA et al. 2004).
Affected by arsenic poisoning

• More serious health problems such as skin

cancer or cardiovascular and nervous
affections are known to appear with a latency
of 10 or more years.
• After 15–30 years of exposure, victims often
suffer from lung, kidney or bladder cancer
(MAZUMDER 2003).
Affected by arsenic poisoning
In Bangladesh (Berg 2007)

Hyperpigmentation

Melanoma

Black foot disease

Thresholds for arsenic

Thresholds for arsenic in drinking water.

WHO guideline 10 g/L
EU 10 g/L
USA (since 2006) 10 g/L
Australia 7 g/L
Bangladesh / India 50 g/L
Cambodia 50 g/L
Vietnam (since 2002) 10 g/L
Arsenic in GW, Hanoi

(Dan and Dzung, 2002)

CASE STUDY

GROUNDWATER POLLUTION CAUSED

BY NITROGEN COMPOUNDS
Nitrogen pollution in GW
Nitrogen pollution in GW

• Pollution of groundwater by nitrogen

compounds in the southern part of Hanoi, has
been studied by the Northern Hydrogeological
Engineering Geological Division since the early
1990s.
• Water samples were taken twice per year
once each in the dry and rainy seasons.
• The studied nitrogen components are NH4+,
NO2- and NO3-.
Patway of nitrogen in GW

Simplified cartoon of pathways by which nitrogen enters the soil and groundwater by and
possible reactions that occurs in the soil
Nitrogen pollution in GW
Nitrogen pollution in GW
Nitrogen pollution in GW
Nitrogen pollution in GW

Location of the study area and

sample points.
- 17 wells with red dot are in
agricultural areas
- 12 wells with blue dot are in
residential areas.
Nitrogen pollution in GW
Nitrogen pollution in GW

Seasonal changes in different types of nitrogen in the groundwater of

agricultural areas of Xinchang village
Nitrogen pollution in GW

Seasonal changes in different types of nitrogen in the groundwater of residential

areas of Xinchang village
Nitrogen pollution in GW

Noncarcinogenic dermal risk values for different types of nitrogen in the

groundwater. (a, b, c) agricultural areas; (d, e, f) residential areas.
Nitrogen pollution in GW

Noncarcinogenic oral risk values for different types of nitrogen in the groundwater.
(a, b, c) agricultural areas; (d, e, f) residential areas.
CASE STUDY

MICROBIAL CONTAMINATION OF
GROUND WATER
Health effects of microbes in GW
• The groundwater in a drinking-water well may
contain a wide variety of microbes without
presenting a public health risk.
• However, groundwater in some areas becomes
contaminated by the fecal material of humans
and other animals which may contain pathogenic
(disease-causing) microbes that can infect the
intestinal tract of humans.
• Fecal pathogens may be bacterial, viral, or
protozoan.
Sources of microbes in GW
• Water containing fecal material may seep into the groundwater
from the land surface or from underground sources of
contamination. Major surface sources include:
– Wastewater and biosolids from sewage treatment facilities that have
been applied to land as a soil conditioner;
– Seepage from shallow artificial ponds (lagoons) used for processing
sewage;
– Seepage from contaminated lakes and other surface-water bodies;
– Urban runoff;
– Feces from cattle and other livestock operations; and
– Improperly constructed sanitary landfills where trash and garbage are
disposed.
• Fecal contamination also can reach the groundwater from
underground sources, such as improperly functioning septic tank
systems, underground reservoirs for liquid household sewage
(cesspools), or leaking underground sewer lines.
Microbes pollution in GW
Microbes pollution in GW

- The small rural Estero San José

(ESJ) watershed (10.8 km2) is
located in the Bío-Bío Region,
Chile.

- The catchment area is sparsely

inhabited by families dedicated to
traditional agriculture.

- The ESJ watershed: characterized

by a Mediterranean climate with a
long dry season leading to water
shortages and a short wet season.
Microbes pollution in GW

The existence of both FC and FS provided strong evidence of fecal contamination

The presence of indicators in all four sampling seasons denoted frequent, if not
continuous, fecal contamination in the ESJ watershed. There seemed to be a permanent
source of fecal bacteria regularly entering the wells.
Microbes pollution in GW

Median concentrations of indicator bacteria.

Microbes pollution in GW

Logistic distribution of TC (Total Coliforms).

Microbes pollution in GW

Logistic distribution of FC (Fecal Coliforms).

Microbes pollution in GW

Logistic distribution of FS (Fecal Streptococci).

Microbes pollution in GW

Correlation analyses revealed a strong, significant, and positive correlation between

TC and FC in June
Microbes pollution in GW

Rainfall and seasonal variability of indicator bacteria concentrations

Microbes pollution in GW
Factors with significant differences between the means of indicator bacteria concentrations
Microbes pollution in GW

• CONCLUSION
– There is widespread groundwater contamination
in the ESJ watershed. The microbiological quality
of the sampled wells was impaired with regard to
Chilean standards.
– A seasonal trend was identified. Concentrations of
FC and FS varied over time and showed a pattern
similar to rainfall which appeared to exert a local
influence on the indicator concentrations. FS were
more affected by rainfall than FC.
Dangers of contaminated GW
• Drinking contaminated groundwater can have
serious health effects.
• Diseases such as hepatitis and dysentery may be
caused by contamination from septic tank waste.
• Poisoning may be caused by toxins that have
leached into well water supplies.
• Wildlife can also be harmed by contaminated
groundwater.
• Other long term effects such as certain types of
cancer may also result from exposure to polluted
water.