WATER SOURCES &

POLLUTION
ECE 3105
SURFACE WATER SOURCES
GROUND WATER
WATER POLLUTION: CAUSES, EFFECTS AND CONTROL MEASURES
• Water pollution is defined as the presence of foreign substances or impurities
(organic, inorganic, biological or radiological) in water, thus degrading its quality
and rendering it toxic to humans or the environment.
• Contamination of water or such alteration of the physical, chemical or biological
properties of water or such discharge of any sewage or trade effluent or of any
other liquid, gaseous or solid substance into water (whether directly or indirectly)
as may, or is likely to, create a nuisance or render such water harmful or injurious
to public health or safety, or to domestic, commercial, industrial, agricultural or
other legitimate uses, or to the life and health of animals or plants or of aquatic
organisms.
• Water is polluted by both natural (volcanic eruptions, earthquakes, tsunamis,
underground rocks and soils etc.) as well as man-made activities (sewage,
industrial effluents, fertilizers etc.).
• They are known to alter water and contaminate it.
Water pollution can occur due to pollutants which can be classified into following
categories:-
1) Biological pollutants:-It includes pathogens like bacteria, viruses, worms,
protozoans etc.
2) Chemical pollutants:-It includes Organic waste (dyes, pesticides etc.), heavy
metals (Mercury, cadmium, chromium etc.), nutrients (nitrogen, phosphorus,
chlorides, fluorides etc.)
3) Physical pollutants:- Physical pollution is change in physical properties of water
e.g. temperature, colour, turbidity, suspended solids etc. It is caused due to waste
heat, construction, eroded stream banks, mining sites etc.
Sources of Water Pollution
• Point source: When contamination originates from a single source such as a pipe,
such as a discharge pipe attached to a factory.
• Nonpoint source: When contamination is derived from diffuse sources. This type
of pollution is often the cumulative effect of small amounts of contaminants
gathered from a large area. These may include agricultural runoff or debris from
land into waterways.
• Transboundary: When contaminated water from one country enters into waters
of another country
Causes of water pollution:
1) Waste water:- With billions of people on the planet, disposing of waste water is a
major problem. According to a new report released by the World Health Organisation
(2017), more than two billion people lack access to clean and safe drinking water. Used
water is wastewater. It comes from our sinks, showers, and toilets (sewage) and from
commercial, industrial, and agricultural activities (metals, solvents, and toxic sludge). It
also includes storm water runoff, which occurs when rainfall carries road salts, oil, grease,
chemicals, and debris from impermeable surfaces into our waterways. Over 30 billion
tons of urban sewage discharged into lakes, rivers and oceans each year. Wastewater also
harbors pathogenic organisms.
2) Nutrients: Nitrogen and phosphorus are the most valuable nutrients in sewage sludge.
Chemical fertilizers used by farmers also add nutrients to the soil, which drain into rivers
and seas. Rain washes fertilizers, pesticides, and animal waste from farms and pathogens
into our waterways. Together, sewage and fertilizers can cause a massive increase in the
growth of algae or plankton.
3) Industrial waste: Industrial waste contains pollutants like asbestos, heavy metals (lead,
mercury, cadmium etc.) and petrochemicals which are extremely toxic to both people
and environment. Leather and chemical industries are major contributors of water
pollution. Around 70% of the industrial waste is dumped into the water bodies.
4) Radioactive waste:- Radioactive substances are used in nuclear power plants,
industrial, medical and other scientific processes. They can be found in watches,
luminous clocks, television sets and x-ray machinery. There are also naturally occurring
radioisotopes from organisms and within the environment. If not properly disposed of,
radioactive waste can result in serious water pollution incidents.
5) Oil Pollution: Oil Pollution is contamination of environment due to the
introduction/presence of oil in excessive quantity. Marine water is especially affected by
this form of pollution. Oil spill occurs due to the release of a liquid petroleum
hydrocarbon into the aquatic environment. They are caused by breakage of oil tankers, oil
pipe leakage, human transport or recreational activities cleaning of tanks, refineries,
drilling rigs and storage facilities.
6) Solid Waste: Dumping of solid wastes and litters in water bodies’ cause huge
problems. Litters include glass, plastic, aluminum, Styrofoam etc. Every day, humans are
generating millions of tons of solid waste, some of it ends up in landfills, and some enters
the waterways by accident or through illegal dumping. Most of that litter (approximately
70%) is plastics, with metal and glass contributing to the remainder. About 80% of the
water pollution is caused due to domestic sewage like throwing garbage on open ground
and water bodies.
Effects of Water Pollution
1) Water related Diseases:-On an average 250 million people worldwide succumb
to diseases related to water pollution.
Pathogens are responsible for causing following diseases:
Waterborne diseases: including cholera, typhoid, and dysentery etc. are caused by
drinking water containing infectious viruses or bacteria, which often come from
human or animal waste.
Water-washed diseases: such as trachoma and scabies, are caused by lack of clean
water.
Water-based diseases: such as schistosomiasis, dracunculiasis etc. spread by
organisms that develop in water and then become human parasites.
Water-related: insect vectors, such as mosquitoes, black fly breed in or near water
and spread diseases, including dengue, malaria, filariasis etc.
Besides pathogens contaminated water also contains toxic heavy metals

READ AND MAKE NOTES ON TOXIC HEAVY METALS FOUND IN WATER

Control Measures
Following are some of the measures to control water pollution:
1) Recycling and Reuse of water: Re-cycling and re-use are other ways to prevent water
pollution which can improve the availability of fresh water. The use of low quality
water, such as treated wastewater in the industries water can be used for washing
vehicles and we should use only good quality water for drinking purposes.
The reclaimed polluted water can be used in making fertilizers as it is rich in
phosphorous, potassium and nitrogen. It can also be used for the irrigation and factories
purposes.
2) Preventing soil erosion: To prevent water from getting polluted, we should prevent soil
erosion. We have to plant more trees to stop soil erosion. We must adopt soil
conservation techniques and manage catchment areas.
3) Cleaning of water ways and the beaches: Cleaning is required on a regular basis.
Travel through sea, residence near sea shores and tourism has resulted into pollution of
water bodies.
4) Adopting organic farming: Overuse of fertilizers and pesticides should be avoided. In
fact, organic manure should be used as it will control runoff of harmful chemicals into
water bodies. States like Sikkim and Kerala are totally doing organic farming.
5) Industries should behave more responsibly: Most of industries throw their wastes into the
rivers which are toxic to living organisms. To prevent water pollution from industrial wastes,
these wastes should be disposed of properly. Industries are also required to modify their
methods of manufacturing or develop techniques to prevent water pollution. . For example,
Roorkee-based Central Building Research Institute has successfully tried to transform the ash
from the thermal power stations into bricks.
6) Avoiding hazardous material: It is also extremely important to adopt the correct methods of
the disposal of toxic wastes. Oil leak from the automobiles, ships and other machines poses
bigger threat and have become major contributors for water pollution. Safe disposal and
clearance of the oil should be done. At the international level, there should be ban on nuclear
tests in the ocean. Plants like water hyacinth, salvinia etc. can be used to treat the polluted water.
7) Cooling towers, cooling ponds and spray towers can be used to control thermal pollution.
8) Compliance with all the laws regarding water pollution: Effective implementation of
established laws could reduce water pollution effectively.
9) Sewage treatment plans: We should set more and more sewage treatment plans as they
convert pollutants into non-toxic substances. The presence of radioactive wastes in the water can
also be removed by oxidation ponds.
10) Educating people and Media involvement: People should be educated on the harmful
effects of water through environmental communication. Like immersion of idols during religious
ceremonies to be done at appointed places only. Garbage in the cities and towns should be
classified and thrown into the designated dustbins only. Dead bodies should not be thrown in the
river.
Biological Water Quality refers to the condition of water based on the presence,
diversity, and abundance of aquatic organisms and the water's capability to
support them, in relation to organic and chemical pollutants. It is often assessed
using parameters like:
• Biochemical Oxygen Demand (BOD)
• Chemical Oxygen Demand (COD)
• Dissolved Oxygen (DO)
• Coliform count
• Macroinvertebrate diversity
Biochemical Oxygen Demand (BOD)
BOD is the amount of oxygen (in mg/L) consumed by aerobic microorganisms to
decompose organic matter in water over a specific period, usually 5 days at 20°C
(BOD₅).
BODt​=D0​−D t
Where:
• D0 = DO at the start (Day 0)
• D t​ = DO after incubation (usually 5 days)
EXAMPLE 1
Calculate BOD5 of water sample,
Chemical oxygen demand, COD
EXAMPLE 2
Determine COD of a water sample