unit 2 water and its importance

8/16/2019 Unit 2 Water and Its Importance

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Water & Its importance page 1 of 4a) describe the importance of the water cycle

b) discuss the methods of water purification (include desalination via

reverse osmosis)

c) discuss the importance of dissolved oxygen to aquatic lifed) discuss the sources of water pollution (include nitrates phosphates heavy

metals (lead and mercury) cyanides trace metals pesticides herbicides

petroleum reside suspended particles)

e) assess the impact of the pollutants in part d) above on the aquatic

environment

Module 3 Water & its importance

Water Cycle

Water cycle is essential for the continued supply of water on the earth!s

surface" #ur bodies are made of about $% water and thus all metabolic

activities require water to be present" We cannot easily ma'e #* water

so we must depend on the water cycle for our present supply of it"

Water Purification

In many cases the water obtained from nature is not pure enough for ourneeds whether it is drin'ing or bathing or even for industrial processes"+ence a series of purification steps must be conducted in order for the water

to be used for our various purposes"

,lease note that desalination can also be considered a process of water

purification via the use of reverse osmosis


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Water & Its importance page - of 4

Sedimentation

.he water after coagulation is left in settling basin further for sufficient period to

allow sedimentation of remaining materials" /edimentation however considerably

reduces microbial population of the water aside from removing most of the

suspended particles"

Filtration

0fter sedimentation water is subected to sand filters to remove floc's of livingorganisms" .he process of filtration is highly critical and important as it can remove

proto2oan cysts and also about 3533 of bacteria from water" .he water may also

be filtered through activated charcoal to remove potentially toxic organic

compounds and organic compounds that impart undesirable colour and6or taste to

the water"

Disinfection

7isinfection is the final step is municipal water purification and it ensures that no pathogenic microorganisms are carried through water" 8or water supplies of small

towns and localities sodium or calcium hypochlorite (9a#:l or :a#:l-

respectively) may be used to disinfect water but for larger cities however

chloroamine (as opposed to chlorine) is now the method for disinfection"

Flocculation

Water from raw water reservoirs (natural

sources) is collected in large tan's6basins

for a sufficient time period to permit large

particulate matter to settle down at the

bottom" .his material is removed and thenthe water is treated with flocculants such

aluminium sulphate which form a floc that

precipitates and carriers with it

microorganisms on the surface"

/uspended organic matter settle onto the

bottom of the tan's6basins" In this ways

most substances that impart turbidity to

water get coagulated"


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Water & Its importance page ; of 4Importance of Dissolved Oxyen

0ll aquatic life depend on the amount of dissolved oxygen (7#) present" .his

allows all aquatic life to conduct their metabolic processes essential to life" +igh

levels of 7# (above 3 water bodies" 7# can also be related

indirectly to !ioloical oxyen demand "#OD$ the higher the 7# the lower the

?#7" #nce 7# levels begin to drop this usually indicates some form of pollution

is present in the water body"

Sources of %ater pollution

P

ollutant Source ffect on environment

9itrates anmade fertilisers 7rin'ing water that getscontaminated with nitrates can

prove fatal especially to infants

that drin' formula mil' as it

restricts the amount of oxygen

that reaches the brain causing

the @blue baby! syndrome as

well as eutrophication"

,hosphates anmade fertilisers anddetergents *utrophication

+eavy metals (e"g"

lead and mercury)

Ase of lead pipes causes

dissolved lead ions to form

in the water improper

disposal of mercury from

industrial processes

Bead affects the nervous

system and can ultimately lead

to death" ercury stunts

physical development of

organisms

:yanides Improper disposal after

used in ma'ing fabrics

0cts as a poison

.race metals mining waste and tailingslandfills or ha2ardous

waste dumps"

+a2ardous effects on nervoussystems and physical

development

,esticides and

herbicides

un off from bac'yards

farms and golf courses

0ccumulate up the food chain

and cause impairment of

physical development of

aquatic life

,etroleum residues 8rom underground storage

tan's

/imilar to pesticides

/uspended particles Industrial processes e"g"

cement manufacture

espiratory problems covers

wide area in fine dust


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Water & Its importance page 4 of 4Practice 'uestions

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unit 2 water and its importance

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