Unit 1 – Section D

Water Purification and Treatment

HW – 1

Read and take notes on Unit 1 sections D.1 & D.2. The section starts on pg 86

D.3 write out and answer questions.

D.1 Natural Water Purification(aka Purifying through the hydrological cycle)

Bacterial actions convert organic contaminants into a few simple compounds

Filtration through sand & gravel remove suspended materials

Evaporation, followed by condensation removes nearly all dissolved substances

D.1 Natural Water Purification(continued)

Pure rainwater is the best natural supply of clean water

D.2 Municipal Water Purification1. Screening2. Coagulent added

(alum)3. Flocculation removing

suspended particles4. Settling5. Sand filtration6. Chlorination

Optional depending on water quality:

• Aeration• pH adjustment• Fluoridation

D.3 Water Purification

Natural Water Cycle

Municipal Water

Treatment

Similarities Sand filtration

Differences Bacterial action Chlorination

D.3 Water Purification(continued)

Remember the natural cycle can be overwhelmed by over demand

HW - 2

Read and take notes D.4 & D.5

D.4 Chlorination of Water

Chlorination greatly helps reduce the risk of many diseases and illnesses.

D.4 Chlorination of Water(continued)

How do we chlorinate water?

1.Cl2 is bubbled through H2O

2.A water solution of NaOCl - sodium hypochlorite, (household bleach) is added to water

3.Ca(OCl)2 - Calcium hypochlorite is dissolved in water (commonly used in swimming pools)

D.4 Chlorination of Water(continued)

Some chlorine is good, too much presents new chemical risks.

Cl reacts with organics to produce THMc

(trihalomenthanes)

A common THM is chloroform

D.5 Chlorination and THMs

How to deal with THMs?

1) Pass treatment-water plant through charcoal filter.

Disadvantages: expensive to install and operate

D.5 Chlorination and THMs(continued)

2 ) Eliminate chlorine and use ozone (O3) or ultraviolet light to disinfect.

Disadvantages: does not protect water once it leaves treatment plant

D.5 Chlorination and THMs(continued)

3 ) Eliminate prechlorination add only once after filtering.

Disadvantages: still promotes THMs (lesser extent) and decreased chlorination can allow bacterial growth

HW – 3

Pre-read D.6 Bottled Water vs. Tap Water we will be doing this in class.

Working with a partner answer the questions on pg. 92

D.6 Bottled Water vs. Tap Water

Tap water is•More consistent in taste

•More convenient

•stringently regulated

•Readily available

•costs less

Bottled water is

In class

Working with a partner answer the questions on pg. 92

HW – 4

Pre-read and take notes on D.7 AND just like it looks on pg 94, create a data table as shown. This should be done in a word document.

D.7 Water Softening

Water hardness is not addressed at municipal treatment plants.

Water containing an excess of dissolved calcium (Ca2+), magnesium (Mg2+) or iron (III) (Fe3+) ions is known as hard water.

D.7 Water Softening(continued)

River water usually contains low levels of calcium (Ca2+), magnesium (Mg2+) or iron (III) (Fe3+) ions , however as it flows over limestone, chalk and other minerals that contain them it gains higher concentrations.

D.7 Water Softening(continued)

One method of water softening is ion exchange , passing the water through tiny insoluble, porous beads capable of attracting and building cations.

HW – 5

Read and take notes on D.8 Water & Water Softening

D.8 Water & Water Softening

Hard water causes common household problems:

• Interferes with actions of soap

• Scale may form as a result of heating

D.8 Water & Water Softening(continued)

Most cleaning products today contain detergent rather than soap.

D.8 Water & Water Softening(continued)

If you live in a hard-water region, your home plumbing may include a water-softener on you home plumbing.

Hardness Magnitude

Grains Per Gallon (GPG)

Soft Water 0.0 - 1.0 gpg

Moderately Hard Water

1.0 - 3.5 gpg

Hard Water 3.5 - 7.0 gpg

Very Hard Water 7.0 - 10.5 gpg

Extremely Hard Water

> 10.5 gpg

Connecting the Concepts

Due by end of class

Q.s 20, 22 & 23* on pg. 103

* Reference pg. 628 assume adult, age 50-70