Science Unit 8 Lesson 4

Question 1

What are the most common water purification methods?

Answer 1

• distillation
• filtering
• boiling
• adding chlorine
  These small- to medium-scale methods can be used in households, labs, and other facilities.

Question 2

How does distillation purify water?

Answer 2

This purifies water by a process of heating and cooling

Question 3

What does distillation remove from the water?

Answer 3

It removes a broad range of contaminants. As the water boils, most contaminants remain behind in the liquid. The process removes oxygen and minerals from water.

Question 4

What cannot be removed during distillation?

Answer 4

Some contaminants can be carried into the water vapor and can be found in the distilled water. Organics such as herbicides and pesticides cannot be removed.

Question 5

Why is distilled water very acidic?

Answer 5

Distilled water has a lower pH and can also be very
acidic.

Question 6

What is distilled water mainly used for?

Answer 6

Distilled water is mainly used for industrial processes.

Question 7

How costly is distillation?

Answer 7

It requires large amounts of energy and is very costly. Equipment must be carefully maintained to ensure purity.

Question 8

What does deionization remove from the water?

Answer 8

This removes ions and dissolved inorganics through an ion exchange process.

Question 9

What cannot be removed during the deionization process?

Answer 9

It does not remove particles, organics, or microorganisms such as bacteria.

Question 10

How costly is deionization?

Answer 10

Over the long term, deionization has a high operating
cost.

Question 11

How does Carbon adsorportion purify water?

Answer 11

This purifies water by using porous activated carbon (in granular or powder form).

Question 12

What processes does carbon adsorption use?

Answer 12

It involves physical and chemical processes.

Question 13

What does carbon adsorption remove from the water?

Answer 13

It removes organic compounds, most chemicals and gases, and some
microorganisms.

Question 14

What does carbon adsorption not remvoe?

Answer 14

It does not usually remove total dissolved solids, hardness, or heavy
metals such as lead. Some specialized carbon filters do remove things
such as lead or asbestos.

Question 15

What does carbon adsorption help improve?

Answer 15

This helps improve the taste and odor of water

Question 16

How costly is carbon adsorption?

Answer 16

It has a lower cost than other filtration types and is commercially available to anyone. When the adsorption medium reaches its capacity, it has to be replaced. Carbon adsorption can be reversed; compounds can desorb after
capacity is reached.

Question 17

How does reverse osmosis purify water?

Answer 17

The process uses pressure to reverse the flow of water in a natural process of osmosis. Water passes from a more concentrated solution to a more dilute
solution through a semi-permeable membrane filter

Question 18

What is the pore size for a reverse osmosis filter?

Answer 18

The pore size for a reverse osmosis filter is 0.0001
micron.

Question 19

What does reverse osmosis remove?

Answer 19

This removes protozoa, bacteria, viruses, and common chemical contaminants such as sodium, copper, and lead.

Question 20

How costly is reverse osmosis?

Answer 20

It has a low cost and does not require much
maintenance

Question 21

How does reverse osmosis affect the pH?

Answer 21

This removes beneficial minerals and changes then pH of water, making it more acidic.

Question 22

How does Ultraviolet Radiation purify water?

Answer 22

This process uses ultraviolet light to disinfect pre-filtered water or reduce the
amount of bacteria found in the water.

Question 23

What does Ultraviolet Radiation remove from the water?

Answer 23

It is highly effective at removing protozoa
and bacteria

Question 24

Why can’t heavy metal be removed from the water during the Ultaviolet Radiation?

Answer 24

As there is no filter, heavy metals cannot
be removed.

Question 25

What does Ultraviolet Radiation fail to remove?

Answer 25

It is inefficient at removing chemical contaminants and heavy metals cant be removed

Question 26

When can ultraviolet radiation be used to purify water?

Answer 26

This can only be used with pre-filtered water or the particles can block UV light.

Question 27

How does ultrafiltration purify water?

Answer 27

This is a process by which water moves through a physical medium that absorbs liquids, gases, and other matter that adhere to the pores of the medium.

Question 28

What does Ultrafiltration remove from the water?

Answer 28

It effectively removes organics, such as protozoa,
viruses, bacteria.

Question 29

What does Ultrafiltration fail to remvoe from the water?

Answer 29

It does not remove most dissolved organics or common chemicals, such as lead, radium, or asbestos.

Question 30

What is the quality of Ultrafiltration water like?

Answer 30

This process helps filter and produce a higher quality of water using the least amount of energy.

Question 31

What are jobs sewers?

Answer 31

Sewers collect the wastewater from homes, businesses, and many industries, and deliver it to plants for treatment.

Question 32

What are the jobs of treatment plants?

Answer 32

Most treatment plants were

built to clean wastewater for discharge into streams or other receiving waters, or for reuse.

Question 33

How does the natural process of purification begin?

Answer 33

First, the sheer volume of clean water in the stream diluted wastes. Bacteria and other small organisms in the water consumed the sewage and other organic matter, turning it into new bacterial cells; carbon dioxide and other products. Today’s higher populations and greater volume of domestic and industrial wastewater require that communities give nature a helping hand.

Question 34

What is the basic function of wastewater treatment?

Answer 34

To speed up the natural processes by which water is purified.

Question 35

What happens in the primary stage of purification?

Answer 35

In the primary stage, solids are allowed to settle and removed from wastewater.

Question 36

What is the secondary start of purification?

Answer 36

The secondary stage uses biological processes to further purify wastewater.

Question 37

In the primary stage, there is a grit chamber. What does it do?

Answer 37

After sewage has been screened, it passes into a grit chamber, where cinders, sand, and small stones settle to the bottom. A grit chamber is particularly important in commu- nities with combined sewer systems where sand or gravel may wash into sewers along with storm water.

Question 38

What the job of the sedimentation tank?

Answer 38

After screening is completed and grit has been removed, sewage still contains organic and inorganic matter along with other suspended solids. These solids are minute particles that can be removed from sewage in a sedimentation tank.

Question 39

How does the sedimentation tank work?

Answer 39

When the speed of the flow through one of these tanks is reduced, the suspended solids will gradu- ally sink to the bottom, where they form a mass of solids called raw primary biosolids formerly sludge). Biosolids are usually removed from tanks by pumping, after which it may be further treated for use as a fertilizer, or disposed of in a land fill or incinerated.

Question 40

What is the problem with inky using primary treatment?

Answer 40

Over the years, primary treatment alone has been unable to meet many communities’ demands for higher water quality. To meet them, cities and industries normally treat to a secondary treatment level, and in some cases, also use advanced treatment to remove nutrients and other contaminants.

Question 41

How much organic matter in sewage does the secondary stage remove?

Answer 41

85 percent

Question 42

What is a trickling filter? What does it do?

Secondary treatment

Answer 42

A trickling filter is simply a bed of stones from three to six feet deep through which sewage passes. Bacteria gather and multi- ply on these stones until they can consume most of the organic matter. The cleaner water trickles out through pipes for further treatment. From a trickling filter, the partially treated sewage flows to another sedimentation tank to remove excess bacteria.

Question 43

Why is the activated sludge process used instead of the tricking filter?

Answer 43

The activated sludge process speeds up the work of the bacteria by bringing air and sludge heavily laden with bacteria into close contact with sewage.

Question 44

What happens in the aeration tank?

Answer 44

After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank, where it is mixed with air and sludge loaded with bacteria and allowed to remain for several hours. During this time, the bacteria break down the organic matter into harmless by-products.

Question 45

During the end of the secondary treatment they use chlorine. What does chlorine do to the water?

Answer 45

Chlorine is fed into the water to kill pathogenic bacteria, and to reduce odor. Done properly, chlorination will kill more than 99 percent of the harmful bacteria in an effluent. Some municipalities now manufacture chlorine solution on site to avoid transporting and storing large amounts of chlorine, sometimes in a gaseous form. Many states now require the removal of excess chlorine before discharge to surface waters by a process called dechlorination. Alternatives to chlorine disinfection, such as ultraviolet light or ozone, are also being used in situations where chlorine in treated sewage effluents may be harmful to fish and other aquatic life.

Question 46

What is sludge?

Answer 46

Sludge is the mass of solids produced in the primary stage

Question 47

How is activated sludge better than trickling?

Answer 47

The activated sludge process speeds up the work of the bacteria by mixing new sewage with air and sludge filled with bacteria. After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank, where it is mixed with air and sludge loaded with bacteria and allowed to remain for several hours. During this time, the bacteria break down the organic matter into harmless by-products. This sludge can also be reused again and again.

Question 48

Why is chlorine added?

Answer 48

Chlorine is added to disinfect, to kill pathogenic bacteria, and to reduce odor.