Drinking Water Drinking Water TreatmentTreatment

The Safe Drinking The Safe Drinking Water Act (SDWA)Water Act (SDWA)

Originally passed in Originally passed in 19741974

Federal law that Federal law that ensures the quality of ensures the quality of Americans’ drinking Americans’ drinking waterwater

EPA sets standards EPA sets standards for drinking water for drinking water qualityquality MCLGMCLG MCLMCL

How do we treat our How do we treat our water in order to make water in order to make

it safe to drink??it safe to drink?? After aeration, the water treatment After aeration, the water treatment process can be divided into 4 main process can be divided into 4 main steps:steps:

Coagulation & FlocculationCoagulation & Flocculation

SedimentationSedimentation

FiltrationFiltration

DisinfectionDisinfection

Now, let’s look at each step

more in-depth!

AeratioAerationn

This is considered to be the very This is considered to be the very 11stst step in the treatment process. step in the treatment process.

Aeration refers to the addition of Aeration refers to the addition of air to the water.air to the water.

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

Coagulation Coagulation & Flocculation& Flocculation

Coagulation removes dirt and other Coagulation removes dirt and other particles suspended in water. particles suspended in water.

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

The combined weight of the dirt and The combined weight of the dirt and the alum (floc) become heavy enough the alum (floc) become heavy enough to sink to the bottom during to sink to the bottom during sedimentation.sedimentation. http://techalive.mtu.edu/meec/demo/Flocculation.html

SedimentationSedimentation The heavy particles (floc) settle The heavy particles (floc) settle

to the bottom.to the bottom.

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

Then, the clear water moves to Then, the clear water moves to filtration.filtration. http://techalive.mtu.edu/meec/demo/Sedimentation.html

FiltrationFiltration The water passes through filters, The water passes through filters,

some made of layers of sand, some made of layers of sand, gravel, and charcoal that help gravel, and charcoal that help remove even smaller particles. remove even smaller particles.

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

DisinfectionDisinfection A small amount of chlorine is A small amount of chlorine is

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

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

Overview…Overview…

Animation on EPA Animation on EPA WebsiteWebsite Go to Go to

http://www.epa.gov/OGWDW/kids/tehttp://www.epa.gov/OGWDW/kids/teachers_9-12.htmlachers_9-12.html

Click on “Interactive Water Click on “Interactive Water Filtration Instructions”Filtration Instructions”

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

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

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

SDWA (continued)SDWA (continued) Maximum Contaminant Level Maximum Contaminant Level

Goal (MCLG) Goal (MCLG) A level for substances found in A level for substances found in

drinking water set by the EPA and drinking water set by the EPA and based on health effectsbased on health effects

Maximum Contaminant Level Maximum Contaminant Level (MCL)(MCL) Legal limit (max) of a pollutant Legal limit (max) of a pollutant

that’s allowed in drinking waterthat’s allowed in drinking water Often MCLG & MCL are sameOften MCLG & MCL are same

SDWA (continued)SDWA (continued) The EPA regulates over 80 The EPA regulates over 80

inorganic (ex: lead, mercury, & inorganic (ex: lead, mercury, & fluoride) and organic chemicals fluoride) and organic chemicals (ex: pesticides) found in drinking (ex: pesticides) found in drinking water.water.

Requires water suppliers to test Requires water suppliers to test water for regulated substances.water for regulated substances.

If they exceed legal limits, they If they exceed legal limits, they must make adjustments.must make adjustments.