Drinking Water Treatment

coriandercultureMécanique

22 févr. 2014 (il y a 3 années et 4 mois)

68 vue(s)

Drinking Water
Treatment

The Safe Drinking Water Act
(SDWA)


Originally passed in 1974


Federal law that ensures
the quality of Americans’
drinking water


EPA sets standards for
drinking water quality


MCLG


MCL



How do we treat our water in
order to make it safe to drink??


After aeration, the water treatment process
can be divided into 4 main steps:



Coagulation & Flocculation



Sedimentation



Filtration



Disinfection


Now, let’s look at
each step more in
-
depth!

Aeration


This is considered to be the very 1
st

step in
the treatment process.



Aeration refers to the addition of air to the
water.



This allows gases trapped in the water to escape
& adds oxygen to the water.

Coagulation

& Flocculation


Coagulation removes dirt and other particles
suspended in water.


Alum (aluminum potassium sulfate) and
other chemicals are added to water to form
tiny sticky particles called "floc" which
attract the dirt particles.


The combined weight of the dirt and the
alum (floc) become heavy enough to sink to
the bottom during sedimentation.


http://techalive.mtu.edu/meec/demo/Flocculation.html


Sedimentation


The heavy particles (floc) settle to the
bottom.



Water must remain in the tank for a long period
to allow the floc to settle out.



Then, the clear water moves to filtration.


http://techalive.mtu.edu/meec/demo/Sedimentation.html


Filtration


The water passes through filters, some made
of layers of sand, gravel, and charcoal that
help remove even smaller particles.

http://techalive.mtu.edu/meec/demo/Filtration.html


Disinfection


A small amount of chlorine is added or some
other disinfection method is used to kill any
bacteria or microorganisims that may be in
the water.


http://techalive.mtu.edu/meec/demo/Disinfection.html


Overview…


Animation on EPA Website


Go to
http://www.epa.gov/OGWDW/kids/teachers_
9
-
12.html


Click on “Interactive Water Filtration
Instructions”


When prompted, click on the bottom of the
screen to start


Then, click on 3 “How to Complete the Lesson”
and watch the animation.


As you watch, please write down each step in the
treatment process.

SDWA (continued)


Maximum Contaminant Level Goal
(MCLG)


A level for substances found in drinking
water set by the EPA and based on health
effects


Maximum Contaminant Level (MCL)



Legal limit (max) of a pollutant that’s
allowed in drinking water


Often MCLG & MCL are same


SDWA (continued)


The EPA regulates over 80 inorganic (ex:
lead, mercury, & fluoride) and organic
chemicals (ex: pesticides) found in drinking
water.



Requires water suppliers to test water for
regulated substances.



If they exceed legal limits, they must
make adjustments.