Water Pollution1

8/12/2019 Water Pollution1

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Any physical, biological, or chemical change in water quality that adversely

affects living organisms or makes water unsuitable for desired uses can be

considered pollution.

a major global problem , leading worldwide cause of deaths and diseases,accounting for deaths of more than 14,000 people daily.

Changing climate patterns are threatening lakes and rivers, and key sources

that we tap for drinking water are being overdrawn or tainted with pollution

When water from rain and melting snow runs off roofs and roads into our

rivers, it picks up toxic chemicals, dirt, trash and disease-carrying organismsalong the way.

Surface water and groundwater have often been managed as separate

resources, although they are interrelated. Surface water seeps through the

soil and becomes groundwater. Conversely, groundwater can also feed

surface water sources.
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Water is typically referred to as polluted:

when it is impaired by anthropogeniccontaminants

does not support a human use, such as drinking water, a marked shift in its ability to support its constituent biotic

communities, such as fish.

Cause of pollution : Natural and artificial

Natural phenomena such as volcanoes, storms, and earthquakes

also cause major changes in water quality and the ecological

status of water.
http://en.wikipedia.org/wiki/Human_impact_on_the_environmenthttp://en.wikipedia.org/wiki/Drinking_waterhttp://en.wikipedia.org/wiki/Volcanohttp://en.wikipedia.org/wiki/Volcanohttp://en.wikipedia.org/wiki/Drinking_waterhttp://en.wikipedia.org/wiki/Human_impact_on_the_environment


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Artificial sources of pollution

generally grouped into two categories based on their origin.

Point source water pollution Refers to contaminants that enter a waterway from a single, identifiable source,

such as a pipeor ditch.

Examples of sources in this category include discharges from a sewagetreatmentplant, a factory, or a city storm drain.

Nonpoint source pollution

Refers to diffuse contamination that does not originate from a single discretesource

often the cumulative effect of small amounts of contaminants gathered from alarge area.

example : leaching out of nitrogen compounds from fertilized agriculturallands

Contaminated storm water washed off of parking lots, roads and highways(

urban runoff)
http://en.wikipedia.org/wiki/Water_pipehttp://en.wikipedia.org/wiki/Ditchhttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Parking_lothttp://en.wikipedia.org/wiki/Urban_runoffhttp://en.wikipedia.org/wiki/Urban_runoffhttp://en.wikipedia.org/wiki/Urban_runoffhttp://en.wikipedia.org/wiki/Urban_runoffhttp://en.wikipedia.org/wiki/Parking_lothttp://en.wikipedia.org/wiki/Parking_lothttp://en.wikipedia.org/wiki/Parking_lothttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/wiki/Ditchhttp://en.wikipedia.org/wiki/Water_pipe


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Effects in the environment

Specific contaminants leading to pollution andchanges such as elevated temperature

High concentrations of naturally occurringsubstances can have negative impacts on aquaticflora and fauna.

Other natural and anthropogenic substances maycause turbidity(cloudiness) which blockslight anddisrupts plant growth, and clogs the gillsof some

fish species. Many of the chemical substances are toxic.

Pathogens can produce waterborne diseasesineither human or animal hosts.

Alteration of water's physical chemistry includes(change in pH), electrical conductivity,

temperature, and eutrophication( increase in theconcentration of chemical nutrients in an resultingnegative environmental effects suchas anoxia(oxygen depletion) and severereductions in water quality may occur, affectingfish and other animal populations.
http://en.wikipedia.org/wiki/Turbidityhttp://en.wikipedia.org/wiki/Turbidityhttp://en.wikipedia.org/wiki/Gillhttp://en.wikipedia.org/wiki/Gillhttp://en.wikipedia.org/wiki/Waterborne_diseaseshttp://en.wikipedia.org/wiki/Waterborne_diseaseshttp://en.wikipedia.org/wiki/Waterborne_diseaseshttp://en.wikipedia.org/wiki/Waterborne_diseaseshttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/Anoxic_watershttp://en.wikipedia.org/wiki/Anoxic_watershttp://en.wikipedia.org/wiki/Anoxic_watershttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Waterborne_diseaseshttp://en.wikipedia.org/wiki/Toxichttp://en.wikipedia.org/wiki/Gillhttp://en.wikipedia.org/wiki/Turbidity


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The water that is fit for drinking safe and agreeable is

called potable water.

1. It should be free from bacteria2. It should be colourless and sparkling

3. It should be tasty, odour free and cool

4. It should be free from objectionable matter

5. It should not corrode pipes

6. It should have dissolved oxygen and free from carbonic acid

so that it may remain fresh


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PATHOGENS Pathogens is the common name for disease-causing micro-organisms.

The first link in the chain of infection is the pathogen. A pathogen is anythingthat causes a disease. Pathogens include:

Bacterium(example: bacterial meningitis or strep throat)

Virus(example: hepatitis A, hepatitis B, and hepatitis C)

Fungus (example: athletes foot)

Waterborne pathogens are disease-causing bacteria, viruses, and protozoans thatare transmitted to people when they consume untreated or inadequately treated

water.

Although the vast majority of bacteria are harmless or beneficial, a fewpathogenic bacteria can cause infectious diseases.

Coliform bacteriaare a commonlyused bacterial indicatorof water pollution,

although not an actual cause of disease.It is an organic pollution (biological hazard)and occurs from fecal contaminations. Fecalcontaminations of water can introduce a

variety of pathogens into waterways, includingbacteria, viruses, protozoa and parasitic

worms.
http://en.wikipedia.org/wiki/Coliform_bacteriahttp://en.wikipedia.org/wiki/Indicator_bacteriahttp://en.wikipedia.org/wiki/Indicator_bacteriahttp://en.wikipedia.org/wiki/Coliform_bacteriahttp://en.wikipedia.org/wiki/Coliform_bacteriahttp://en.wikipedia.org/wiki/Coliform_bacteria


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High levels of pathogens may result from inadequately

treated sewagedischarges,this can be caused by a sewage plant designed

with less than secondary treatment(more typical in less-developed

countries).

In developed countries, older cities with aging infrastructure may have

leaky sewage collection systems (pipes, pumps, valves), which can

cause sanitary sewer overflows. Some cities also have combined sewers,

which may discharge untreated sewage during rain storms.

Pathogen discharges may also be caused by poorly managed livestock

operations.
http://en.wikipedia.org/wiki/Sewagehttp://en.wikipedia.org/wiki/Secondary_treatmenthttp://en.wikipedia.org/wiki/Sanitary_sewer_overflowhttp://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Sanitary_sewer_overflowhttp://en.wikipedia.org/wiki/Secondary_treatmenthttp://en.wikipedia.org/wiki/Sewage


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Fecaloral route

Route of transmissionof a disease,

when pathogensin fecalparticles pass

from one hostand introduced into

the oral cavityof another host

Some examples of routes of fecal-oral

transmission include:

water that has come in contact with

feces and is then

inadequately treatedbefore drinking;

food that has been prepared in the

presence of fecal matter;

disease vectors, like houseflies,

spreading contamination frominadequate fecal disposal;

poor or absent cleaning after handling

feces or anything that has been in

contact with it;
http://en.wikipedia.org/wiki/Transmission_(medicine)http://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Feceshttp://en.wikipedia.org/wiki/Host_(biology)http://en.wikipedia.org/wiki/Oral_cavityhttp://en.wikipedia.org/wiki/Water_treatmenthttp://en.wikipedia.org/wiki/Houseflyhttp://en.wikipedia.org/wiki/Houseflyhttp://en.wikipedia.org/wiki/Water_treatmenthttp://en.wikipedia.org/wiki/Oral_cavityhttp://en.wikipedia.org/wiki/Host_(biology)http://en.wikipedia.org/wiki/Feceshttp://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Transmission_(medicine)http://en.wikipedia.org/wiki/Transmission_(medicine)


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Summary

Any physical, biological, or chemical change in water quality that adversely affectsliving organisms or makes water unsuitable for desired uses can be considered

pollution. Worldwide, the most serious water pollutants, in terms of human health, are

pathogenic organisms from human and animal wastes.

In industrialized nations, toxic chemical wastes have become an increasing problem.

Agricultural and industrial chemicals have been released or spilled into surfacewaters and are seeping into groundwater supplies.

Major causes of ocean pollution are oil spills from tanker bilge pumping or accidentsand oil well blowouts.

Surface runoff and sewage outfalls discharge fertilizers, pesticides, organic nutrients,and toxic chemicals that have a variety of deleterious effects on marine ecosystems.

Addition of salts and metals from industrial activities also damage water quality.

In some areas, drainage from mines deliver toxic materials to rivers and lakes. Water pollution is a major source of human health problems.

Appropriate land-use practices and careful disposal of industrial, domestic, andagricultural wastes are essential for control of water pollution.

Natural processes and living organisms have a high capacity to remove or destroywater pollutants, but these systems become overloaded and ineffective when

pollution levels are too high.


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Water treatment

Raw water Primarysedimentation

Screening

Secondarysedimentation

Coagulation/Floculation

FiltrationDisinfection

Supply


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Aeration can be achieved through the infusion of air into the bottom of

the lakeor pondor by surface agitation from a fountain or spray-like device to

allow for oxygen exchange at the surface and the release of noxious gasses such

as carbon dioxide, methaneor hydrogen sulfide.

Dissolved oxygen(DO) is a major contributor to water quality. Not only do fish

and other aquatic animals need it, but oxygen breathing aerobic

bacteriadecompose organic matter. When oxygen concentrations become low,

anoxic conditions may develop which can decrease the ability of the water body

to support life.

Any procedure by which oxygen is added to water can be considered a type of

water aeration.

Aeration removes odour and tastes

Aeration also oxidise iron and manganese

increases dissolved oxygen content in water,

removes CO2

reduces corrosion

removes methane and other flammable gases.

Types of Aerators

Gravity aerators

Fountain aerators

Diffused aerators

Mechanical aerators.
http://en.wikipedia.org/wiki/Lakehttp://en.wikipedia.org/wiki/Pondhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Hydrogen_sulfidehttp://en.wikipedia.org/wiki/Dissolved_oxygenhttp://en.wikipedia.org/wiki/Aerobic_bacteriahttp://en.wikipedia.org/wiki/Aerobic_bacteriahttp://en.wikipedia.org/wiki/Aerobic_bacteriahttp://en.wikipedia.org/wiki/Aerobic_bacteriahttp://en.wikipedia.org/wiki/Dissolved_oxygenhttp://en.wikipedia.org/wiki/Hydrogen_sulfidehttp://en.wikipedia.org/wiki/Hydrogen_sulfidehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Pondhttp://en.wikipedia.org/wiki/Lake


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Gravity Aerators (Cascades):

In gravity aerators, water is allowed to fall by gravity such that a large area of

water is exposed to atmosphere, sometimes aided by turbulence


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Fountain Aerators :

These are also known as spray aerators with

special nozzles to produce a fine spray.

Injection or Diffused Aerators :

It consists of a tank with perforated pipes, tubes or

diffuser plates, fixed at the bottom to release fine

air bubbles from compressor unit.

Mechanical Aerators :

Mixing paddles as in flocculation are used. Paddles may

be either submerged or at the surface.


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SEDIMENTATION

It is the process in which the suspended solids are made to settle by gravity under

still water conditions .

Principle of Settling

Suspended solids present in water having specific gravity greater than that of

water tend to settle down by gravity as soon as the turbulence is retarded by

offering storage. Examples are settling of sand in filtration and the settling of

grits, and sandy and silty particles in pre-sedimentationtreatment.-plainsedimentation

Basin in which the flow is retarded is called settling tank.

Theoretical average time for which the water is detained in the settling tank is

called the detention period.

Settling basins may be eitherlong rectangular or circular in plan.

Long narrow rectangular tanks with horizontal flow are generally preferred to the

circular tanks with radial or spiral flow.


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Coagulation and Flocculation

Colloidal particles are difficult to separate from water because they do not settle by

gravity and are so small that they pass through the pores of filtration media. To be removed, the individual colloids must aggregate and grow in size.

Certain chemicals are added to the water so as to remove such impurities which are

not removed by plain sedimentation.

The chemical form insoluble, gelatinous, flocculent precipitate absorbs and entaglevery fine suspended matter and colloidal impurities during its formation and

descent through water.

Coagulation in Water Treatment

Salts of Al(III) and Fe(III) are commonly used as coagulants in water and

wastewater treatment.


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Filtration

The resultant water after sedimentation will not be pure, and may contain some

very fine suspended particles and bacteria in it.

To remove or to reduce the remaining impurities still further, the water isfiltered through the beds of fine granular material, such as sand, etc.

The process of passing the water through the beds of such granular materials is

known as Filtration.

In filtration, a multilayer lattice retains those particles that are unable to

follow the tortuous channels of the filte.Oversize particles may form a cake

layer on top of the filter and may also block the filter lattice, preventing the

fluid phase from crossing the filter (blinding). Commercially, the term filter is

applied to membraneswhere the separation lattice is so thin that the surface

becomes the main zone of particle separation,

Types of Filter
http://en.wikipedia.org/wiki/Membranehttp://en.wikipedia.org/wiki/Membrane


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Rapid-sand filter:

consist of larger sand grains supported by

gravel and capture particles throughout

the bed.

They are cleaned by backwashing water

through the bed to 'lift out' the particles.

Types of Filter

Slow sand filter:

consist of fine sand, supported by

gravel.

capture particles near the surface of

the bed and are usually cleaned by

scraping away the top layer of sand

that contains the particles.

Disinfection


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Treatment with Excess Lime:

Lime is used in water treatment plant for softening. But if excess lime is added to

the water, it can in addition, kill the bacteria also.

Lime when added raises the pH value of water making it extremely alkaline. This

extreme alkalinity has been found detrimental to the survival of bacteria.

This method needs the removal of excess lime from the water before it can be

supplied to the general public.

Chlorination: The germicidal action of chlorine is explained by the recent theory of

Enzymatic hypothesis, according to which the chlorine enters the cell walls of bacteria

and kill the enzymes which are essential for the metabolic processes of livingorganisms

Boiling:

The bacteria present in water can be destroyed by boiling it for a long time.

However it is not practically possible to boil huge amounts of water. Moreover it

cannot take care of future possible contaminations.

Disinfection

The filtered water may normally contain some harmful disease producing bacteria

in it.

These bacteria must be killed in order to make the water safe for drinking. The

process of killing these bacteria is known as Disinfection or Sterilization.

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