4.0 DRINKING WATER TREATMENT PROCESS
4.0 DRINKING WATER TREATMENT PROCESS
4.1 Aeration of water quality
4.2 Setting and precipitation of colloidal particles
4.3 Hardness removal
INTRODUCTION
Water treatment describes those processes used to make water
more acceptable for desired end-use. These can include used as
drinking water industrial process, medical, and many other
uses.
The goal of all water treatment is removed existing contaminants
in the water and reduce the concentration of contaminants so the
water becomes fit for its desired end-use. One of such use in
returning water that has been used into natural environment without
adverse ecological part.
What is existing contaminants?
The Safe Drinking Water Act defines the term "contaminant" as
meaning any physical, chemical, biological, or radiological
substance or other matter in water.
Some drinking water contaminants may be harmful if consumed at
certain levels in drinking water while others may be harmless.
contaminants
RADIOLOGICAL
radiological contaminants include
cesium, plutonium and uranium
BIOLOGICAL
biological or microbial contaminants include bacteria, viruses,
protozoan, and parasites.
PHYSICAL
sediment or organic material suspended in the water of lakes,
rivers and streams from soil erosion
CHEMICAL
contaminaninitrogen, bleach, salts, pesticides, metals, toxins
produced by bacteria, and human or animal drugs.
Drinking water quality
Drinking water quality refers to the chemical, physical,
biological, and radiological characteristics of water. It is a
measure of the condition of water relative to the requirements of
one or more biotic species and or to any human need or purpose.
Example:
Our drinking water comes from two sources
Surface water which are rivers, lake and reservoirs
Groundwater which is stored below water surface.
4.1Aeration of water quality
Aeration is used to remove tastes and odors and
To remove minerals such as iron and manganese from water and
To remove carbon dioxide from the water
How aeration occurred?
In water treatment the aeration process brings water and air
into close contact by exposing drops or thin sheets of water to the
air or by introducing small bubbles of air and letting them rise
through the water. For both procedures the processes by which the
aeration accomplishes the desired results are the same:
Scrubbing action
Oxidation
Scrubbing action
Undesirable gases (e.g. hydrogen sulfide) enter the water either
from the air above the water or as a by-product of some chemical or
biological reaction in the water.
The scrubbing action caused by the turbulence of aeration
physically removes these gases from solution and allows them to
escape into the surrounding air.
Oxidation
Aeration can help remove certain dissolved gases and minerals
through oxidation, the chemical combination of oxygen from the air
with certain undesirable metals (iron and manganese) in the
water.
Once oxidized, these chemicals fall out of solution and become
suspended material in the water. The suspended material can then be
removed by filtration.
Type of aeration method
Water into air
Air into water
Water into air
. The water-to-air method is designed to produce small drops of
water that fall through the air.
Example of aerator of water into air
Cascade aerator
Cone aerator
Slat and coke aerator
Spray aerator
The aerator of water into air
Spray aerator
Cascade aerator
Cone aerator
Slat and coke aerator
Air into water
The air-to-water method creates small bubbles of air that are
injected into the water stream
Example of aerator of air into water
Pressure aerator
4.2 ) Settling and precipitation of colloidal particle
SUSPENSION
SOLUTION
COLLOID
Suspension
Suspension is a mixture containing large , dispersed particle
that can settle out or be separated by filtration.
Source:
http://www.search.ask.com/search?&apn_dtid=%5EBND533+%5EYY%5EMY&d=533-257&atb=sysid%3D533%3Aappid%3D257%3Auid%3De29141436635d9fe%3Auc2%3D518%3Atypekbn%3D1.1%3Asrc%3Dds%3Ao%3DAPN10644&shad=s_0017&p2=%5EAG5%5EBND533+%5EYY%5EMY&apn_ptnrs=%5EAG5&o=APN10644&gct=ds&q=example+of+suspension&tpr=10&ctype=pictures&imgsize=all&safeSearch=on&imgDetail=true
Colloid
Colloid is a mixture containing solid particles small enough to
remain suspended and not settle out
Source :
http://www.search.ask.com/search?&apn_dtid=%5EBND533+%5EYY%5EMY&d=533-257&atb=sysid%3D533%3Aappid%3D257%3Auid%3D1dd1ff7bede14ac0%3Auc2%3D518%3Atypekbn%3D1.1%3Asrc%3Dds%3Ao%3DAPN10644&shad=s_0017&p2=%5EAG5%5EBND533+%5EYY%5EMY&apn_ptnrs=%5EAG5&o=APN10644&gct=ds&q=colloid&tpr=10&ctype=pictures&imgsize=all&safeSearch=on&imgDetail=true
Solution
Is a homogenous mixture of two or more substance always
transparent and Particles of true solution cannot be filtered
through filter paper and are not visible to naked eye.
Source:
http://upload.wikimedia.org/wikipedia/commons/thumb/8/89/SaltInWaterSolutionLiquid.jpg/220px-SaltInWaterSolutionLiquid.jpg
Coagulation
Coagulation removes dirt and other particles suspended in
water.
Alum and other chemicals are added to water to form tiny sticky
particles called floc" which attract the dirt particles.
Flocculation
The combined weight of the dirt and the alum (floc) become heavy
enough to sink to the bottom during sedimentation.
Sedimentation
Surface water containing high turbidity ( e.g , from a muddy
river). A sedimentation process used to remove gravel, sand, and
other gritty material from raw water before it enters the
filtration. This is usually done without the use of coagulating
chemicals
Filtration
The water passes through filters, some made of layers of sand,
gravel, and charcoal that help remove even smaller particles
Disinfection
A small amount of chlorine is added or some other disinfection
method is used to kill any bacteria or microorganisms that may be
in the water.
Storage
Water is placed in a closed tank or reservoir in order for
disinfection to take place. The water then flows through pipes to
homes and businesses in the community.
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