Unit 2:
Water pollution and pollutants (Natural and Anthropogenic)
What is water pollution?
The World Health Organisation (WHO) says that polluted water is water whose
composition has been changed to the extent that it is unusable. In other words,
it is toxic water that cannot be drunk or used for essential purposes like agriculture,
and which also causes diseases like diarrhea, cholera, dysentery, typhoid, and
poliomyelitis that kill more than 500,000 people worldwide every year.
The main water pollutants include bacteria, viruses, parasites, fertilizers,
pesticides, pharmaceutical products, nitrates, phosphates, plastics, fecal
waste, and even radioactive substances. These substances do not always
change the colour of the water, meaning that they are often invisible pollutants.
That's why small amounts of water and aquatic organisms are tested to determine
water quality.
What are the types of underground water sources?
Infiltration galleries, infiltration wells, springs, and wells are the different types
of underground water sources
What are the qualities of groundwater?
Groundwater is the water present beneath the Earth's surface in rock and soil pore
spaces and the fractures of rock formations. About 30 percent of all readily available
freshwater in the world is groundwater. A unit of rock or an unconsolidated deposit is
called an aquifer when it can yield a usable quantity of water.
Temperature, turbidity, color, taste, and odor make up the list of physical water
quality parameters. Since most groundwater is colorless, odorless, and without
specific taste, we are typically most concerned with its chemical and biological
qualities.
GROUNDWATER QUALITY PARAMETERS
The following Groundwater quality parameters were tested for the samples collected
from the site selected.
A. pH
pH is the degree of how acidic/basic water is. The range goes from 0 – 14, with 7
being neutral. pH of less than 7 denotes acidity, whereas a pH of greater than 7
denotes a base. pH is really a measure of the relative amount of free hydrogen and
hydroxyl ions in the water. As pH can be affected by chemicals in the water, pH is an
important indicator of water that is changing chemically.
B . Hardness
Hardness is induced by compounds of calcium and magnesium and by a variety of
other metals. Hard water is formed when water oozes through deposits of limestone
and chalk which are largely made up of calcium and magnesium carbonates.
General instructions for categorizing water are 0 to 60 mg/L (milligrams per liter) as
calcium carbonate is classified as soft; 61 to 120 mg/L as reasonably hard; 121 to
180 mg/L as hard; and more than 180 mg/L as very hard.
C.Turbidity
Turbidity is the measure of the relative transparency of a liquid. It is an optical
characteristic of water and is an expression of the amount of light that is diffused by
material in the water when a light is shined through the water sample. The higher the
magnitude of scattered light, the higher the turbidity. Material that causes water to be
turbid includes clay, silt, lightly divided inorganic and organic matter, algae, soluble
colored organic compounds, and plankton and other atomic organisms.
Excessive turbidity, or cloudiness, in drinking water is aesthetically unappealing, and
may also represent a health concern. Therefore it is essential to determine the
turbidity of water.
D. Acidity
The acidity of water is its quantitative capacity to neutralize a strong base to a
designated pH.
Acidity contributes to the corrosiveness of water and influences certain chemical and
biological processes. Acidity due to carbon dioxide is practically important in the field
of public water supplies. It can be measured by titrating the sample with a standard
solution of alkaline reagents. Results are reported in terms of phenolphthalein acidity
or total acidity expressed as CaCO3.
E. Alkalinity
It is a measure of the capacity to neutralize acids. It is primarily due to the salts of
weak acids although weak or strong bases may also contribute. Alkalinity is an
important parameter involved in corrosion control and in determining the soda ash
requirements in softening water by precipitation method. Alkalinity is measured
volumetrically by titration with 0.02N H2SO4 or HCl. It is expressed in terms of total
alkalinity as CaCO3.
F.Chloride
In potable water, the salty taste is produced by chlorides. High chloride content is
harmful to metallic pipes and agriculture crops. It is an important consideration in the
selection of supplies for human use, where brackish water must be used for
domestic purposes to determine the type of desalting apparatus to be used. Chloride
is measured volumetrically by titration with silver nitrate solution. It is expressed in
mg/L.
G . Iron
Iron is one of the most important parameters of groundwater quality. Excessive
concentration of iron in water leads to bitter and astringent taste of water. It also
causes scaling of boilers and bacterial promotion in service mains. According to the
Bureau of Indian Standards, the desirable limit of iron in drinking water is 0.3mg/liter.
H . Total coliform
Coliforms are harmful bacteria whose presence in water can lead to serious health
issues. It should not be present in water used for consumption purposes.
I.TDS
TDS stands for Total Dissolved Solids and refers to the total concentration of
dissolved substances in drinking water. TDS comprises inorganic salts and a small
amount of organic matter as well
RESULTS AND DISCUSSIONS
The test results for the analyzed samples are shown in Table II. On comparing the
obtained results with the IS 10500-2012, it was seen that the iron, turbidity, and
hardness values of most of the samples are greater than their desirable limits. Many
of the samples also show the presence of coliforms in the bacteriological
examination thus making it unfit for drinking.
TABLE I. DESIRABLE LIMITS AS PER 10500:2012
CHARACTERISTICS DESIRABLE LIMITS
pH 6.5-8.5
Total Hardness as CaCO3(mg/l) 200
Turbidity(NTU) 1
Alkalinity (mg/l) 200
Acidity (mg/l) –
Chloride (mg/l) 250
Iron (mg/l) 0.3
TDS Level in parts per million(ppm) Palatability Quotient
Between 50-150 Excellent for drinking
150-250 Good
250-300 Fair
300-500 Poor
Above1200 Unacceptable
What are the 3 types of water analysis?
Physical tests indicate properties detectable by the senses. Chemical tests
determine the amounts of mineral and organic substances that affect water quality.
Bacteriological tests show the presence of bacteria, characteristic of faecal pollution.
What are surface water sources?
Surface water is any body of water above ground, including streams, rivers, lakes,
wetlands, reservoirs, and creeks. The ocean, despite being saltwater, is also
considered surface water.
Surface Water Quality Assessment
The samples are collected at regular intervals and analyzed for various parameters,
including temperature, pH, dissolved oxygen, turbidity, and nutrients. Monitoring
these parameters can help identify changes in water quality and detect potential
environmental issues.
What are the qualities of surface water?
There are many important properties of surface water, including temperature,
saltiness (also called salinity), turbidity, and levels of dissolved nutrients, such as
oxygen and carbon dioxide. These factors all affect climate and the biodiversity in
and around a body of water.
Below are the water quality standards based on the class of water.
S.
No Water quality parameter A* B* C*
Dissolved Oxygen (DO)
1 mg/l (minimum) 6 5 4
Biochemical Oxygen
Demand (BOD), mg/l
2 (max) 2 3 3
Total Coliform
organisms **
3 MPN/100ml (max) 50 ** 500 500
4 Total Dissolved Solids 500 – 1500
(TDS) mg/l (max)
Chlorides (as Cl–) mg/l
5 (max) 250 – 600
6 Colour, Hazen units (max) – 10 300
Sodium Absorption Ratio
7 (max) – – –
8 Boron (as B), mg/l (max) – – –
Sulfates (as SO4 -2), mg/l
9 (max) 400 – 400
–
Nitrates (as NO3 ) mg/l
10 (max) 20 – 50
Free Ammonia (as NH3)
11 mg/l (max) – – –
o
Conductivity at 25 C
12 micromhos/cm (max) – – –
13 pH value 6.5-8.5 6.5-8.5 6.5-8.5
14 Arsenic (as As), mg/l (max) 0.05 0.2 0.2
15 Iron (as Fe), mg/l (max) 0.3 – –
16 Fluoride (as F), mg/l (max) 1.5 1.5 1.5
17 Lead (as Pb), mg/l (max) 0.1 – 0.1
Note: * Classes of water use:
A Drinking water source without conventional treatment but after disinfection
B Outdoor bathing (organised)
C Drinking water source with conventional treatment followed by disinfection.
** If the coliform is found to be more than the prescribed tolerance limits, the criteria f
or
coliforms shall be satisfied if not more than 20 percent of samples show more than th
e tolerance limits specified and not more than 5 percent of samples show values
more than 4 times the tolerance limits. There should be no visible discharge of
domestic and industrial waste into class “A” waters. In the case of classes “B” and
“C,” the discharge shall be so regulated/ treated to ensure maintenance of the
stream standards.
Three Main Types of Water Quality Parameters Explained
1. Physical Water Quality Parameters. 1.1 Turbidity. 1.2 Temperature. 1.3 Color. 1.4
Taste and Odor. 1.5 Solids. 1.6 Electrical Conductivity.
2. Chemical Parameters of Water Quality. 2.1 PH. 2.2 Acidity. 2.3 Alkalinity. 2.4
Chlorine. 2.5 Hardness. ...
3. Biological Parameters of Water.
Physical Water Quality Parameters :
Turbidity
Though less used than some of the other water quality parameters on this list,
turbidity refers to how cloudy water is. When you use Turbidity sensors, these
devices are designed to measure the ability that light has to pass through
water. High levels of turbidity can occur as a result of higher concentrations of silt,
clay, and organic materials. The main issue with turbidity in water is that the water
will look bad. No one wants to drink cloudy water. Several additional problems that
are caused by high turbidity include:
-Water treatment costs will be higher
-High levels of particulates can act as a shield for harmful microorganisms, which
makes it more difficult to get rid of these contaminants
-Suspended materials may damage fish gills, reduce growth rates, and decrease
resistance to diseases
-Various suspended particles can act as adsorption media for mercury, cadmium,
lead, and other heavy metals
-Dissolved oxygen concentration will likely decrease
Turbidity starts to become visible in water when sensors provide you with readings of
over five NTU. As for muddy water, it can have turbidity readings of more than 100
NTU.
Temperature
Some of the aspects of water quality that are influenced by the water’s temperature
include odors, chemical reactions, solubility, palatability, and viscosity. As such,
biological oxygen demand, sedimentation, and chlorination all depend on the
water’s temperature. The ideal water temperatures range from 50-60 degrees
Fahrenheit.
Color
It’s possible for the color of the water to be altered by materials that decay from
organic matter, the primary of which include vegetation. Such inorganic matter as
rocks, soil, and stones may also affect the color of the water. Even though these
changes to a water’s color may create aesthetic issues with the water, they don’t
change how the water tastes. You can effectively measure color by comparing a
water sample to color glass disks or standard color solutions.
When you’re attempting to identify the color of water, it’s important to understand the
difference between the water’s apparent color and its true color. The apparent color
is made up of suspended material and dissolved solid colors. The true color of water
can be identified after all suspended materials have been filtered out of the water.
Keep in mind that color can be graded on a scale that ranges from 0-70 color units.
Pure water contains no color units because it is essentially colorless.
Taste and Odor
It’s possible for the taste of water to change and for odors to develop as a result of
foreign matter being introduced to the water. This matter can include organic
materials, dissolved gases, and inorganic compounds. Most of this matter is
derived from agricultural, natural, and domestic sources.
Solids
Solids can be in suspension or solution when they get into the water. If you put a
water sample through a glass fiber filter, suspended solids will remain at the top of
this filter. On the other hand, any dissolved solids will pass through and remain
in the water. When measuring the number of solids in water, it’s common for total
dissolved solids to be measured. You can identify how much organic matter is
present in the water by measuring for total dissolved solids. The three different water
classifications for total dissolved solids include:
-Freshwater – Less than 1,500 mg/L TDS
-Brackish water – 1,500-5,000 mg/L TDS
-Saline water – More than 5,000 mg/L TDS
Electrical Conductivity
Another core physical parameter that you should be aware of involves electrical
conductivity, which measures how well a sample of water or similar solution
can carry or conduct electrical currents. Conductivity levels will increase as the
amount of ions in the water increases.
This is one of the main parameters when measuring water quality because of how
easy it is to detect water contamination levels when measuring the conductivity of
water. High conductivity means that the water contains a high amount of
contaminants. On the other hand, potable water and ultra-pure water are practically
unable to conduct an electrical current. The main units of measurement for electrical
conductivity include micromhos/cm and milliSiemens/m, the latter of which is
abbreviated into mS/m.
Chemical Parameters of Water Quality :
PH
When measuring the quality of water, pH is one of the first measurements that you
should take. The pH of water is measured with a simple pH sensor or test kit,
which will tell you how acidic or basic the water is. Acidic water will invariably be
comprised of more hydrogen ions. On the other hand, basic water contains more
hydroxyl ions.
It’s possible for pH levels to range from 0-14. If you receive a reading of 7.0, this
means that the water is neutral. Any readings below 7.0 are acidic, while any
readings above 7.0 are alkaline. Pure water has a neutral pH. However, rainfall is
somewhat more acidic and typically has a 5.6 pH. Water is considered to be safe to
drink if it has a pH of 6.5-8.5. The many effects that changing pH levels can have on
plants and animals include:
-The majority of aquatic plants and animals can live in water with a specific pH,
which means that slight changes could worsen the quality of life
-Slightly acidic water can irritate fish gills, damage membranes, and reduce the
number of hatched fish eggs
-Water with extremely high or extremely low pH is fatal to aquatic plants and animals
-Low pH can kill amphibians because their skin is sensitive to contaminants
Acidity
This refers to the measure of how much acids are in a specific solution. The
water’s acidity is the quantitative capacity that it has to neutralize a base at a certain
pH level. Acidity is commonly caused by the presence of mineral acids, hydrolyzed
salts, and carbon dioxide. When acids are introduced to water, they can influence
many different processes, which include everything from biological activities and
chemical reactions to corrosion. The acidity of water is measured with a pH sensor.
Alkalinity
Alkalinity indicates the water’s acid-neutralizing capacity. Likely the most common
reason to measure the alkalinity of a sample of water is to identify how much
soda and lime must be added to the water for water softening purposes. The
water softening process is particularly beneficial for mitigating corrosion in boilers. If
water is alkaline, this means that it has a pH that’s at least higher than 7.0. The
presence of bicarbonate ions, carbonate ions, and hydroxide ions increases the
alkalinity of water. If you find that your water samples have high alkalinity or acidity,
this indicates that the water is contaminated in some way.
Chlorine
While chlorine doesn’t occur naturally in water, it’s commonly added to wastewater
for disinfection purposes. Even though base chlorine is a toxic gas, the aqueous
solution is completely harmless to humans. If a small amount of chlorine is found
in water, this indicates that the water is clean and essentially free from
contaminants. You can measure chlorine residual with a spectrophotometer or color
comparator test kit.
Hardness occurs when water contains high mineral levels. If left untended, the
dissolved minerals in your water could create scale deposits on hot water pipes. If
you take a shower with water that has high mineral content, you may find it difficult to
produce a lather with the soap you’re using. Hardness in water is mainly caused
by the presence of magnesium and calcium ions, which can enter water from
rock and soil. In most cases, groundwater has more hardness to it than surface
water. You can measure water hardness with a colorimeter or test strip.
Dissolved Oxygen
This is a critical water quality parameter that can help you determine how polluted
rivers, lakes, and streams are. When water has a high concentration of dissolved
oxygen, you can be confident that the water quality is high. Dissolved oxygen
occurs because of the solubility of oxygen. The amount of DO that you can find
in water depends on numerous factors, the primary of which include the water’s
salinity, pressure, and temperature. It’s possible to measure dissolved oxygen levels
with a colorimeter or with the electrometric method.
Biological Oxygen Demand
Microorganisms like bacteria use organic matter as a source of food. When this
material is metabolized, oxygen is consumed. If this process takes place in water,
the dissolved oxygen in a sample of the water will be consumed. If there is a
substantial amount of organic matter in the water, high amounts of dissolved oxygen
will be consumed to make sure that the organic matter decomposes. However, this
creates problems since aquatic plants and animals require DO to survive. You can
measure biological oxygen demand with the dilution method. if the BOD levels are
high, the water is contaminated.
Biological Parameters of Water :
Bacteria
Bacteria are single-celled plants that can ingest food and reproduce at rapid
rates if the water’s pH, food supply, and temperature are ideal. Because
bacteria can grow rapidly, it’s almost impossible to count the number of bacteria in a
sample of water. In most cases, bacteria will reproduce at a slow rate in colder
water. Many harmful waterborne diseases can be caused by high amounts of
bacteria in water, which include cholera, tularemia, and typhoid.
Algae
Algae are tiny, microscopic plants that consist of photosynthetic pigments. These
plants can support themselves by effectively converting inorganic matter into
organic matter, which is done with energy from the sun. While this process is
ongoing, the algae consume carbon dioxide and release oxygen.
Algae are also essential in wastewater treatment processes that use stabilization
ponds. The main issues caused by algae include strange odors and poor taste
problems. Keep in mind that some species of algae can pose serious public health
risks. For instance, blue-green algae can kill cattle.
Viruses
Viruses are tiny biological structures that can be harmful to a person’s health. Only
strong electronic microscopes can view viruses. All viruses require parasites to live.
Because of how small viruses are, they can pass through the majority of filters.
Certain waterborne viruses can cause hepatitis and similar health problems. Despite
the difficulty in treating viruses, most water treatment facilities should be able
to eliminate viruses during the disinfection process.
Understanding the three primary types of water quality parameters may prove useful
when you want to treat water and remove the many contaminants that can be found
in water. Whether your water has high turbidity, a low pH, or ample bacteria, there is
an array of solutions that you can use to eradicate these issues for good.
What are the processes of potable water?
Public drinking water systems use different water treatment methods to provide safe
drinking water for their communities. Public water systems often use a series of
water treatment steps that include coagulation, flocculation, sedimentation, filtration,
and disinfection.
Water is purified by various processes, some of which are by reverse osmosis or by
using UV-filtered water purifiers, etc. The water that is not potable or fit for drinking is
called raw water and is mostly from sources like groundwater, rivers, and lakes.
What are the 6 steps of processing water?
These are the common steps on which all treatment plants base their
practices.
Step 1: Screening. ...
Step 2: Aeration. ...
Step 3: Coagulation and Flocculation. ...
Step 4: Sedimentation. ...
Step 5: Filtration. ...
Step 6: Disinfection. ...
Step 7: Storage/Distribution.
Water pollution: Surface and groundwater pollution, types of pollutants :
What is surface and groundwater pollution?
Surface waters are polluted by point sources, such as agricultural or industrial
installations, or via overland flow from rain or snowmelt. Subsequently, by transport
through the soil profile, pollutants can reach groundwater and, according to their
character, can have very serious consequences.
What are the types of surface water pollution?
Surface water pollution comes from agricultural runoff, sewage and wastewater, oil
pollution, and radioactive substances. As surface water is important in providing
drinking water and supporting all life on Earth, reducing the number of contaminants
and pollutants that enter these environments is crucial.
What causes groundwater pollution?
Industrial discharges, urban activities, agriculture, groundwater pumpage, and
disposal of waste all can affect groundwater quality. Contaminants can be human-
induced, such as from leaking fuel tanks or toxic chemical spills.
What is surface water pollution in detail?
Surface water pollution is generally caused by pathogens, nutrients, plastics,
chemicals such as heavy metals, pesticides, antibiotics, industrial waste discharges,
and individuals dumping into waterways.
Mode of water pollution
Sources Of Water Pollution Industrial effluents. Social and Religious Practices. Use
of Detergents and Fertilizers. Agricultural run-offs- Use of insecticides and
pesticides.
Describing industrial water treatment system flow chart?
Water is a crucial component in production. Water is essential in industry, and it
must adapt to the various needs of various operations. Industrial water includes
everything from cooling and boiler feed water in power plants to process water for a
variety of industrial applications, as well as ultrapure water for the electronics and
pharmaceutical industries. Raw water treatment systems are used to pre-treat and
optimize source water, to increase production efficiency and process performance
for a specific application. Pre-treating cooling tower/boiler feed water,
process/production water, and/or drinking water are examples.
Raw water treatment is frequently focused on protecting downstream equipment
against pollutants in the source water that cause scaling, fouling, corrosion, and
other types of damage or premature wear. Suspended/colloidal particles,
silica/colloidal silica, iron, bacteria, and hardness are commonly removed by raw
water treatment systems.
Below is a flowchart with described steps, representing several processes included
to make water perfect for industrial use:
Intake: Gravity and/or pumps are used to bring raw water into a plant. To keep
heavy things out of the system, the water is frequently routed through a metal grate
or mesh screen.
Clarification: The water then goes through a multistep clarifying procedure to
remove suspended particles from a solution. Coagulation, in which chemical and/or
pH modifications lead particles to clump together, is followed by flocculation, in which
physical movement encourages the production of bigger particles. The stream next
runs to a gravity settler, where sediments settle to the bottom in what is known as a
sludge blanket. Finally, a gravity sand filter is used to catch any minute particles in
the stream.
Disinfection: If biological pollution and/or water potability are issues, the water can
be disinfected to eliminate microorganisms. Chemical disinfectants (such as
chlorine), physical disinfectants (such as UV or heat), and some types of membrane
filtration can all be used to disinfect water.
Lime softening: It is a term used to describe the process of lime in streams with
significant mineral or sulfate concentration, a lime softening step may be added to
minimize hardness. The procedure involves adding lime or lime soda to the stream
to elevate the pH, which causes mineral components to precipitate out of the
solution.
Ion Exchange: An IX unit for hardness removal or other particular treatment needs
may be included in the raw water treatment system in some situations. A stream is
channeled through a strong acid cation resin that has been "charged" with sodium;
as the water passes through, the resin collects the hardness-causing calcium or
magnesium ions while releasing sodium ions into the stream.
Distribution: The water is pumped or otherwise directed for use elsewhere in the
facility after treatment.
DRINKING WATER TREATMENT (SOURCE: SCIENCE DIRECT.COM)
WASTEWATER TREATMENT
What is water pollution
The World Health Organisation (WHO) says that polluted water is water
whose composition has been changed to the extent that it is
unusable. In other words, it is toxic water that cannot be drunk or used for
essential purposes like agriculture, and it also causes diseases like diarrhea,
cholera, dysentery, typhoid, and poliomyelitis that kill more than 500,000
people worldwide every year.
The main water pollutants include bacteria, viruses, parasites, fertilisers,
pesticides, pharmaceutical products, nitrates, phosphates, plastics,
faecal waste, and even radioactive substances. These substances do not
always change the colour of the water, meaning that they are often invisible
pollutants. That's why small amounts of water and aquatic organisms are
tested to determine water quality.
Point sources
A point source is a single, identifiable source of pollution, such as a pipe or a drain.
Industrial wastes are commonly discharged into rivers and the sea in this way.
EPA regulates high-risk point source waste discharges through the works approval
and licensing system, and associated compliance and enforcement activities.
Non-point sources
Non-point sources of pollution are often termed ‘diffuse’ pollution. They refer to
inputs and impacts that occur over a wide area and are not easily attributed to a
single source. They are often associated with particular land uses, as opposed to
individual point source discharges.
