Isabella Ramos Jan AguasHannah Vergara

Agatha YusonJames Chua

Group Four

5.10 Covalent CompoundsAnd Their Solutions

5.11 Protecting Our Drinking Water:

Federal Legislation

5.12 Treatment of Municipal Drinking Water

COVALENT COMPOUNDSANDTHEIR SOLUTIONS

What exactly is a covalent compound?

A covalent compound is a compound in which the atoms

that are bonded share electrons

rather than transfer electrons from one to the other.

What are the properties of

covalent compounds?

1) Covalent compounds generally have much lower

melting and boiling points than ionic compounds.

2) Covalent compounds are

soft and squishy (compared to

ionic compounds, anyway).

3) Covalent compounds tend to be more flammable than ionic

compounds.

4) Covalent compounds don't conduct electricity in water.

5) Covalent compounds aren't usually very soluble

in water.

Like

dissolveslike

We know for a fact that water and oil don’t mix and the reason for that is they are very different structurally. Water molecules are highly polar while oil consists of

nonpolar hydrocarbon molecules. These molecules stick with their own when they come in contact.

Three Examples of a covalent compound

sucrose (table sugar), ethylene glycol (the main ingredient of

antifreeze),

ethanol (which is usually found in

alcoholic beverages)

The ethanol (C2H5OH) molecule’s –OH group can form hydrogen bonds

with H2O molecules and it’s the reason why water and ethanol have

great affinity for each other.

Another alcohol is the ethylene glycol which has two –OH

groups for hydrogen bonding with H2O which makes

ethylene glycol highly water-soluble.

And then we have sucrose which contains eight –OH

groups and three additional oxygen atoms that can participate in hydrogen

bonding. This explains the high solubility of sugar in

water.

Protecting Our Drinking Water:Federal Legislation

We all need clean drinking water to survive. Keeping our water supplies safe has long been recognized as an

important public health issue.

The Safe Drinking Water Act (SDWA) was passed To provide public health protection to all

Americans who get their water from community water

supplies (over 250 million people).

Contaminants that may be health risks are regulated by EPA that sets legal limits for

such contaminants according to their levels of adverse risk

as required by SDWA.

For each contaminant, the EPA has established a maximum contaminant level goal or the MCLG, which is the maximum level of contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would

occur.Each MCLG includes built-in safety factors accounting for uncertainties in collection data and for how different people might

react to each contaminant.

The concentration of an impurity must exceed the maximum contaminant level or the MCL, which sets the legal limit for the concentration of a contaminant, before any regulatory action is taken against a water utility.

POLLUTANT MCLG MCL

Cadmium 0.005 0.005

Chromium 0.1 0.1

Lead 0 0.015

Mercury 0.002 0.002

Nitrate 10 10

Benzene 0 0.005

Trihalomethanes 0 0.080

For each contaminant, the EPA has established a maximum contaminant level goal (MLCG).

Lower limits for MCL values have been established as more accurate risk information, improved detection and quantitative analytical

methods has become available.

As of now, more than 80 contaminants are regulated which fall into several major categories:

a. Metals (cadmium, chromium, copper, mercury, and lead)b. A few nonmetallic elements (fluorine, and arsenic)c. Pesticidesd. Industrial solventse. Compounds associated with plastics manufacturing, and radioactive materials

These contaminants pose chronic health problems even when consumed in tiny doses.

Other laws have also been passed like the Clean Water Act or the CWA to provide the foundation for dramatic progress in reducing surface water pollution over the past three decades. This act establishes limits on the amounts of pollutants that industries can discharge into surface waters.

Improvements in surface water quality have at least two major beneficial effects:

They reduce the amount of clean-up needed for public drinking water supplies, andThey result in a more healthful natural environment for aquatic organizations.

In turn, a more healthful aquatic ecosystem

has many indirect benefits for humans.

Treatment of Municipal Drinking Water

How is water treated to make it fit for human consumption?

STEPS IN TREATING WATER

STEPS IN TREATING WATER

STEP 1. Water is passed through a screen that separates it from

other objects. (Ex. Sticks, fishes, tires, and beverage cans)

STEP 2. Two chemicals are added to the water : Aluminium Sulphate

(Al2(SO4)3+) and Calcium Hydroxide (Ca(OH)2). These chemicals are known

as flocculating agents. When mixed together, they react to form

Aluminum Hydroxide (Al(OH)3+)

which is a gel that collects suspended clay and dirt

particles. The gel settles with all the collected particles in a

separate settling tank.

STEP 3. Remaining particles are removed as water is filtered

through coal or gravel and then sand.

STEP 4. Chlorine is then added to the water. This is

the most crucial step as chlorine kills disease carrying organisms, making the water

safe for drinking.

STEP 5. An optional step, Sodium Fluoride (NaF) is

added to the water to help protect against tooth decay.

Forms of Chlorine

Forms of Chlorine

The chlorine added to the water usually comes in one of three forms :

1. Chlorine gas (Cl2)2. Sodium Hypochlorite (NaClO)3. Calcium Hypochlorite (Ca(ClO)2)

These generate an antibacterial agent called Hypochlorous Acid (HClO). Only

a very low concentration of this solution is added to the water

(between 0.075ppm and 0.600ppm) to protect it against further

contamination as it travels through the pipes to the user.

REASONS WHY CHLORINE IS ADDED TO THE WATER

CASE 1. In a classic study, John Snow was able to

trace a mid-1800s cholera epidemic in London to

water contaminated with the excretions of victims of

the disease.

CASE 2. In 1991, a cholera epidemic in Peru was traced to bacteria in shellfish growing in estuaries with untreated fecal matter. The bacteria found its

way into the water supply where they continued to multiply because of the absence of

chlorination.

DRAWBACKS OF CHLORINATION1. The taste and odor of residual chlorine is objectionable. This is often the reason why people prefer to drink bottled water or use filters to remove residual chlorine at the tap.

2. Residual chlorine reacts with other substances in the water forming by-products with potentially toxic levels. (Ex. Trihalomethanes (THMs) such as Chloroform (ChCl3-))

ALTERNATIVE CHEMICALS USED IN WATER TREATMENT

1.Ozone (O3)Used in many European and a few US cities, the toxic property of ozone is used for a beneficial purpose. Ozone is more effective than chlorine against water borne viruses, and disinfection can be achieved with a smaller concentration. However, ozonation is more expensive and it decomposes quickly, thus leaving it unable to protect water from contamination after it leaves the treatment plant.

2. Ultraviolet (UV) RadiationUV disinfection is very fast, leaves no residual by-products, and is economical for small installations. However, like ozone, UV disinfection does not protect the water from contamination after it leaves the treatment plant.

ADDITIONAL PURIFICATION STEPS

Depending on local conditions, one or more additional purification steps may be carried

out at the water treatment facility after disinfection.

1. Water is sprayed into the air to remove volatile chemicals that create objectional

odors and tastes.

2. Calcium oxide (lime) is added to water to neutralize its acidity should it cause problems such as corrosion of pipes.