EE-I, Lecture 5, Water Pollution and Source Protection.pdf

2024-04-15 Lecture-5: Water Pollution and Source Protection 1
Environmental Engineering-I
Engr. Arian Khan
Lecture-5: Water Pollution and
Source Protection

• In the last few decades, there has been a tremendous increase in the demand for
freshwater due to rapid growth of population and the accelerated pace of
industrialization.
• Human health is threatened by most of the agricultural development activities
particularly in relation to excessive application of fertilizers and unsanitary
conditions.
• Anthropogenic activities related to extensive urbanization, agricultural practices,
industrialization, and population expansion have led to water quality
deterioration in many parts of the world.
• In addition, deficient water resources have increasingly restrained water pollution
control and water quality improvement.

• Water pollution has been a research focus for government and scientists.
Therefore, protecting river water quality is extremely urgent because of serious
water pollution and global scarcity of
water resources
Water Contamination Vs Water Pollution
• Contamination is the presence of a substance that should not be present
naturally. Pollution is when the contaminant causes harm to organisms or
infrastructure. Therefore, you can have a contaminated environment without it
being polluted but you cannot have a polluted environment without it being
contaminated

Sources of water pollution
Water pollution can occur from two sources:
 Point source and
 Non-point source
• Point sources of pollution are those which have direct identifiable
source.
• Example includes pipe attached to a factory, oil spill from a tanker,
effluents coming out from industries. Point sources of pollution
include wastewater effluent (both municipal and industrial) and
storm sewer discharge and affect mostly the area near it.

• Whereas non-point sources of pollution are those which arrive from
different sources of origin and number of ways by which
contaminants enter into groundwater or surface water and arrive in
the environment from different non identifiable sources.
• Examples are runoff from agricultural fields, urban waste etc.
Sometimes pollution that enters the environment in one place has an
effect hundreds or even thousands of miles away. This is known as
transboundary pollution. One example is the radioactive waste that
travels through the oceans from nuclear reprocessing plants to
nearby countries.

Point Sources Nonpoint Sources
Wastewater effluent (municipal and industrial) Runoff from agriculture (including return flow
from irrigated agriculture)
Runoff and infiltration from animal feedlots Runoff from pasture and range
Runoff from mines, oil fields, unsewered
industrial sites
Urban runoff unsewered and sewered areas with
a population <100,000
Storm sewer outfalls from cities with a
population >100,000
Septic tank leachate and runoff from failed
septic systems
Runoff from construction sites >2 ha Runoff from construction sites
Runoff and leachate from waste disposal sites Runoff from abandoned mines
Overflows of combined storm and sanitary
sewers
Atmospheric deposition over a water surface
Activities on land that generate contaminants,
such as logging, wetland conversion,
construction, and development of land or
waterways

Water pollutants may be Organic and Inorganic water pollutant.
Organic water pollutants
• They comprise of insecticides and herbicides, organohalides and other forms of
chemicals; bacteria from sewage and livestock farming; food processing wastes;
pathogens; volatile organic compounds etc.
Inorganic water pollutants:
• They may arise from heavy metals from acid mine drainage;
silt from surface run-off, logging, slash and burning practices and land filling;
fertilizers from agricultural run-off which include nitrates and phosphates etc. and
chemical waste from industrial effluents.

Some important sources of water pollution
Urbanization
• Urbanization generally leads to higher phosphorus concentrations in urban
catchments. Increasing imperviousness, increased runoff from urbanized
surfaces, and increased municipal and industrial discharges all result in increased
loadings of nutrients to urban streams. This makes urbanization second only to
agriculture as the major cause of stream impairment.

Sewage and other Oxygen Demanding Wastes:
• Management of solid waste is not successful due to huge volumes of organic and
non-biodegradable wastes generated daily.
• As a consequence, garbage in most parts of developing countries is
unscientifically disposed and ultimately leads to increase in the pollutant load of
surface and groundwater courses.
• Chemical fertilizers used by farmers also add nutrients to the soil,
which drain into rivers and seas and add to the fertilizing effect of the
sewage. Together, sewage and fertilizers can cause a massive increase in
the growth of algae or plankton that facilitate huge areas of oceans, lakes,
or rivers creating a condition known as algal bloom thereby reducing the
dissolved oxygen content of water and killing other forms of life like fish.

Industrial Wastes
• Many of the industries are situated along the banks of river such as steel and paper
industries for their requirement of huge amounts of water in manufacturing processes
and finally their wastes containing acids, alkalies, dyes and other chemicals are dumped
and poured down into rivers as effluents.
• Chemical industries concerning with manufacture of Aluminium release large amount of
fluoride through their emissions to air and effluents to water bodies.
• Fertilizer industries generate huge amount of ammonia whereas steel plants generate
cyanide.
• Chromium salts are used in industrial process for the production of sodium dichromate
and other compounds containing chromium. All such discharges finally arrive at water
bodies in the form of effluents affecting human health and the organism living there.

Agro-chemical Wastes
• Agro-chemical wastes include fertilizers, pesticides which may be herbicides and
insecticides widely used in crop fields to enhance productivity.
• Improper disposal of pesticides from field farms and agricultural
activities contributes a lot of pollutants to water bodies and soils. Some of the
pesticides are: DDT, Aldrin, Dieldrin, Malathion, Hexachloro Benzene etc.
• Pesticides reach water bodies through surface runoff from agricultural fields,
drifting from spraying, washing down of precipitation and direct dusting and
spraying of pesticides in low lying areas polluting the water
quality.
• Most of them are non-biodegradable and persistent in the environment for long
period of time. These chemicals may reach human through food chain leading to
biomagnification.

Nutrient enrichment
• The sources of nutrients in surface water can be divided broadly into
natural and anthropogenic types.
• Contribution to pollution by natural source is low due to balance established by
the natural system between the production and consumption of nutrients over
the course of time. Anthropogenic sources of contaminants are contributed from
agriculture, domestic and industrial wastes.
• Nutrient concentrations in streams and rivers have been strongly correlated with
human land use and disturbance gradients.
• In contrast to point sources of nutrients that are relatively easy to monitor and
regulate, nonpoint sources such as livestock, crop fertilizers, and urban runoff
exhibit more spatial and temporal variability. Nutrients from nonpoint sources are
now the major source of water pollution in the United States.

Thermal pollution:
• Changes in water temperature adversely affect water quality and aquatic biota.
Majority of the thermal pollution in water is caused due to human activities.
• Some of the important sources of thermal pollution are nuclear power and
electric power plants, petroleum refineries, steel melting factories, coal fire
power plant, boiler from industries which release large amount of heat to the
water bodies leading to change in the physical, chemical and biological
characteristics of the receiving water bodies.
• High temperature declines the oxygen content of water; disturbs the
reproductive cycles, respiratory and digestive rates and other physiological
changes causing difficulties for the aquatic life.

Oil spillage
• Oil discharge into the surface of sea by way of accident or leakage from cargo
tankers carrying petrol, diesel and their derivatives pollute sea water to a great
extent.
• Exploration of oil from offshore also lead to oil pollution in water. The residual oil
spreads over the water surface forming a thin layer of water-in-oil emulsion.

The disruption of sediments
• Construction of dams for hydroelectric power or water reservoirs can reduce the
sediment flow affecting adversely the formation of beaches, increases coastal
erosion and reduces the flow of nutrients from rivers into seas (potentially
reducing coastal fish stocks).
• Increased sediment flow can also create a problem. During construction work,
soil, rock, and other fine powders sometimes enter nearby rivers in large
quantities, causing water to become turbid (muddy or silted). The extra sediment
can block the gills of fish, causing them suffocation.

Acid rain pollution:
• Water pollution that alters a plant’s surrounding pH level, such as due to acid
rain, can harm or kill the plant.
• Atmospheric Sulfur dioxide and nitrogen dioxide emitted from natural and
human-made sources like volcanic activity and burning fossil fuelsinteract with
atmospheric chemicals, including hydrogen and oxygen, to form sulfuric and nitric
acids in the air.
• These acids fall down to earth through precipitation in the form of rain or snow.
Once acid rain reaches the ground, it flows into waterways that carry its acidic
compounds into water bodies. Acid rain that collects in aquatic environments
lowers water pH levels and affects the aquatic biota.

• Radioactive waste
• Radioactive pollution is caused by the presence of radioactive materials in water.
They are classified as small doses which temporary stimulate the metabolism and
large doses which gradually damage the organism causing genetic mutation.
• Source may be from radioactive sediment, waters used in nuclear atomic plants,
radioactive minerals exploitation, nuclear power plants and use of radioisotopes
in medical and research purposes.

Introduction of Alien species
• In some parts of the world, alien species also known as invasive species are a
major problem of water pollution.
• Outside their normal environment, they have no natural predators, so they
rapidly spread and dominate the animals or plants that thrive there.
• Common examples of alien species include zebra mussels in the Great Lakes of
the USA, which were carried there from Europe by ballast water (wastewater
flushed from ships).

• The Mediterranean Sea has
been invaded by a kind of alien
algae called Caulerpa taxifolia.
• In the Black Sea, an alien
jellyfish called Mnemiopsis
leidyi reduced fish stocks by 90
percent after arriving in ballast
water.
• In San Francisco Bay, Asian
clams called Potamocorbula
amurensis, also introduced by
ballast water, have dramatically
altered the ecosystem

Climate Change
• Global warming has also an impact on water resources through enhanced
evaporation, geographical changes in precipitation intensity, duration and
frequency (together affecting the average runoff), soil moisture, and the
frequency and severity of droughts and floods.
• Future projections using climate models pointed out that there will be an
increase in the monsoon rainfalls, with increasing greenhouse gases and sulphate
aerosols.
• Relatively small climatic changes can have huge impact on water resources,
particularly in arid and semi-arid region. during the wet season, Increase in
temperatures can lead to increased eutrophication in wetlands and fresh water
supplies.

Effects of water pollution
Polluted water has effects on both human and aquatic life.
1. Effect of water pollution on human health
• Some of the chemicals affecting human health are the presence of heavy metals
such as Fluoride, Arsenic, Lead, Cadmium, Mercury, petrochemicals, chlorinated
solvents, pesticides and nitrates.
• Fluoride in water is essential for protection against dental carries and weakening
of the bones. Concentration below 0.5 mg/l causes dental carries and mottling of
teeth but exposure to higher levels above 0.5 mg/l for 5-6 years may lead to
adverse effect on human health leading to a condition called fluorosis.

• Arsenic is a very toxic chemical that reaches the water naturally or from
wastewater of tanneries, ceramic industry, chemical factories and from
insecticides such as lead arsenate, effluents from fertilizers factories and from
fumes coming out from burning of coal and petroleum. Arsenic is highly
dangerous for human health. Long exposure can lead to respiratory concern, skin
lesion, bladder and lungs cancer.
• Lead is contaminated in the drinking water source from pipes, fitting, solder,
household plumbing systems. In the human beings, it affects the blood, central
nervous system and the kidneys. Child and pregnant women are mostly prone to
lead exposure.

• Mercury is used in industries such as smelters, manufactures of batteries,
thermometers, pesticides, fungicides etc. The best-known example of Mercury
pollution in the oceans took place in 1938 when a Japanese factory discharged a
significant amount of mercury into Minamata Bay, by contaminating the fish
stocks there.
• It took several years to show its effects. By that time, many local people had
eaten the fish and around 2000 were poisoned, hundreds of people were left
dead and disabled and the cause for death was named as “Minamata disease”
due to consumption of fish containing methyl mercury.
• It causes chromosomal aberrations and neurological damages to human. Mercury
shows biological magnification in aquatic ecosystems.

• Cadmium reaches human body through food crop from soil irrigated by affected
effluents. Friberg et al. (1974) noted that long term consumption of rice from
affected fields by the people living in areas contaminated by cadmium in regions
of Japan, resulted into many renal diseases like “itai-itai disease”, nephritis and
nephrosis.
Microorganisms
• Microorganisms play a major role in water quality and the microorganisms that
are concerned with water borne diseases are Salmonella sp., Shigella sp.,
Escherichia coli and Vibrio cholera. All these cause typhoid fever, diarrhoea,
dysentery, gastroenteritis and cholera.

• The most dangerous form of water pollution occurs when faeces enter the water
supply. Many diseases are perpetuated by the faecal-oral route of transmission in
which the pathogens are shed only in human faeces. Presence of faecal coliforms
of E.coli is used as an indicator for the presence of any of these water borne
pathogens.
• Ground water contamination is the leading worldwide cause of deaths and
diseases, and that it accounts for the deaths of more than 14,000 people daily,
and the majority of them being children under 5 years old.
• In recent years, the widespread reports of pollutants in groundwater
have increased public concern about the quality of groundwater. Children are
generally more vulnerable to intestinal pathogens, and it has been reported that
about 1.1 million children die every year due to diarrhoeal diseases.

2. Effect of water pollution on plants
The following are the effects of water pollution on plants:
Effects of acid deposition
• Many of the gases from acid, aerosols and other acidic substances released into
the atmosphere from industrial or domestic sources of combustion from fossil
fuels finally fall down to ground and reach the water bodies along with run-off
rainwater from polluted soil surfaces thereby causing acidification of water
bodies by lowering its pH.
• In many countries chemical substances like sulphates, nitrates and chloride have
been reported to make water bodies such as lakes, river and ponds acidic.

• Population of decomposing microorganisms like bacteria and fungi decline in
acidified water which in turn reduces the rate of decomposition of organic matter
affecting the nutrient cycling.
• The critical pH for most of the aquatic species is 6.0. The diversity of species
decline below this pH whereas the number and abundance of acid tolerant
species increases.
• It is observed that plants with deep roots and rhizomes are less affected while
plants with short root systems are severely affected in acidic water.

Effects of organic matter deposition
• Organic matter from dead and decaying materials of plants and animals is
deposited directly from sewage discharges and washed along with rainwater into
water bodies causing increase in decomposers/microbes such as aerobic and
anaerobic bacteria.
• Rapid decomposition of organic matter increase nutrient availability in water
favoring the luxuriant growth of planktonic green and blue-green algal bloom. In
addition many of the macrophytes like Salvinia, Azolla, Eicchhornia etc. grow
rapidly causing reduced penetration of light into deeper layer of water body with
gradual decline of the submerged flora .
• This condition results in reducing the dissolved oxygen and increase in the
biological oxygen demand (B.O.D). The B.O.D of unpolluted fresh water is usually
below 1mg/l while that of organic matter polluted water is more than 400 mg/l.

Effects of detergent deposition:
• Detergents from domestic and industrial uses wash down into water bodies causing
serious effects on plants. Detergents contain high phosphates which results in
phosphate-enrichment of water.
• Phosphates enter the plants through roots or surface absorption causing retarded
growth of plants, elongation of roots, carbon dioxide fixation, photosynthesis, cation
uptake, pollen germination and growth of pollen tubes, destruction of chlorophylls and
cell membranes and denaturation of proteins causing enzyme inhibition in various
metabolic processes.

Effects of agricultural chemicals:
• Chemicals from fertilizers, pesticides, insecticides, herbicides etc. applied to crops
in excess are washed away with rainwater as runoff, then enter soil and finally
arrive at the water bodies. Chemicals from fertilizers result in eutrophication by
enrichments of nutrients.
• Ammonium from fertilizers is acidic in nature causing acidification of water.
• Similarly, pesticides, herbicides, and insecticides also cause change in pH of the
water bodies. Most common effect of these substances is the reduction in
photosynthetic rate.

Effects of industrial wastes
• Effluents from industries contain various organic and inorganic waste products.
Fly ash form thick floating cover over the water thereby reducing the penetration
of light into deeper layers of water bodies.
• Fly ash increases the alkalinity of water and cause reduced uptake of essential
bases leading to death of aquatic plants.
• Liquid organic effluents change the pH of water and the specific toxicity effects on
the aquatic plants vary depending on their chemical composition.
• There may be synergistic, additive or antagonistic interactions between metals
with respect to their effects on plants however these effects are reduced in hard
and buffered freshwater bodies.

Effects of silt deposition
• Deposition of silt in water bodies occurs as a result of erosion carrying silt laden
water and due to flood. It increases the turbidity of water and reduces light
penetration in deep water causing decline in abundance of submerged plants.
• Siltation inhibits the growth of aquatic plants. Abundance of phytoplankton is
affected due to reduction in surface exchange of gases and nutrients. Plants that
are tolerant to turbidity are abundant followed by those that are intermediate
and the least tolerant species.
• Plants such as Polygonum, Sagittaria etc. are found to grow in dominance.

Effects of thermal pollution
• The release of heated water into water bodies from the thermal power plants has
an adverse effect on the aquatic life.
• It reduces the activity of aerobic decomposers due to oxygen depletion because
of high temperature. With decreased organic matter decomposition , the
availability of nutrients in the water bodies is jeopardized.
• Aquatic plants show reduced photosynthesis rate due to inhibition of enzyme
activity with increased temperature.
• Primary productivity and diversity of aquatic plant species decline because of
increased temperature of water bodies as a result of thermal pollution.

Effects of oil spillage
• Oil pollution due to spillage of oil tankers and storage containers
prevents oxygenation of water and depletes the oxygen content of the water
body by reducing light transmission inhibiting the growth of planktons and
photosynthesis in macrophytes.
Effect of nutrient enrichment
• Nutrient enrichment in aquatic water bodies leads to eutrophication which is a
process whereby water bodies receive excess inorganic nutrients, especially N
and P, stimulating excessive growth of plants and algae.
• Eutrophication can happen naturally in the course of normal succession of some
freshwater ecosystems. However, when the nutrient enrichment is due to the
activities of humans, it is referred to as “cultural eutrophication”, where the rate
of nutrient enrichment is greatly intensified.

• Eutrophication was recognized as a pollution problem in North American lakes
and reservoirs in the mid 20th century. Plants must take in nutrients from the
surrounding environment in order to grow. Nitrogen and phosphorous, in
particular, encourage growth because they stimulate photosynthesis.
• This is why they are common ingredients in plant fertilizers. When agricultural
runoff pollutes waterways with nitrogen and phosphorous rich fertilizers, the
nutrient-enriched waters often paves way to algal bloom leading to
eutrophication. The result is oxygen depletion and dying of fishes due to
suffocation.

Phytotoxicity effects on plants
• When chemical pollutants build up in aquatic or terrestrial
environments, plants can absorb these chemicals through
their roots. Phytotoxicity occurs
when toxic chemicals poison plants.
• The symptoms of phytotoxicity on plants include
poor growth, dying seedlings and dead spots on leaves.
• For example, mercury poisoning which many people
associate with fish can also affect aquatic plants, as
mercury compounds build up in plant roots and bodies
result in bioaccumulation. As animals feed on polluted
food the increasing levels of mercury is built up through
food chain.

Controlling Water Pollution
• The key challenges to better management of the water quality in Pakistan
comprise of temporal and spatial variation of rainfall, uneven geographic
distribution of surface water resources, persistent droughts, overuse of ground
water and contamination, drainage and salinisation and water quality problems
due to treated, partially treated and untreated wastewater from urban
settlements, industrial establishments and runoff from irrigation sector besides
poor management of municipal solid waste and animal dung in rural areas.
• Some of the control measures are given below:
 Rainwater harvesting should be practiced to prevent the depletion of water
table.

 In most parts of the country, wastewater from domestic sources is hardly
treated, due to inadequate sanitation facilities. This wastewater, containing highly
organic pollutant load, finds its way into surface and groundwater courses near
the vicinity of human habitation from where further water is drawn for use.
Considerable investments should be done to install the treatment systems.
 For the agricultural sector, water and electricity for irrigation are subsidized for
political reasons. This leads to wasteful flood irrigation rather than adoption of
more optimal practices such as sprinkler and drip irrigation. Optimized irrigation,
cropping patterns and farming practices should be encouraged for judicious use
of water.

 With rapid industrialization and urbanization, the water requirement for energy
and industrial use is estimated to rise. Poor environmental management systems,
especially in industries such as thermal power stations, chemicals, metals and
minerals, leather processing and sugar mills, have led to discharge of highly toxic
and organic wastewater.
 This has resulted in pollution of the surface and groundwater sources from
which water is also drawn for irrigation and domestic purpose. The enforcement
of regulations regarding discharge of industrial wastewater and limits to
extraction of groundwater needs to be considerably strengthened, while more
incentives are required for promoting wastewater reuse and recycling.

 For the agricultural sector, water and electricity for irrigation are subsidized for
political reasons. This leads to wasteful flood irrigation rather than adoption of
more optimal practices such as sprinkler and drip irrigation. Optimized irrigation,
cropping patterns and farming practices should be encouraged for judicious use
of water.
 Water quality monitoring is an imperative prerequisite in order to assess the
extent of maintenance and restoration of water bodies.
 Making people aware of the problem is the first step to prevent water pollution.
Hence, importance of water and pollution prevention measures should be a part
of awareness and education programe.

 Industries should install Effluent Treatment Plant to control the pollution at
source.
 All towns and cities must have Sewage Treatment Plants that clean up the
sewage effluents.
 Improper use of fertilizers, herbicides and pesticides in farming should be
stopped and organic methods of farming should be adopted.
 Rainwater harvesting should be practiced to prevent the depletion of water
table.

EE-I, Lecture 5, Water Pollution and Source Protection.pdf

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