Midterm review- Environmental Chem

Question 1

How is Ozone formed?

Answer 1

UV rays from sun break up Oxygen gas into highly reactive Oxygen radicals, radicals tag on to O2 to make O3 (Ozone). O3 then gets another radical to make 2 Oxygen gases.

Question 2

Rate of Ozone Production equals…

Answer 2

rate of Ozone destruction (Steady State)

Question 3

What disrupts Ozone equilibrium?

Answer 3

CFCs and NOx’s in the atmosphere

Question 4

Cause of Acid Rain?

Answer 4

Presence of SOx and NOx in atmosphere

Question 5

pH of pure rain?

Answer 5

5.65

Question 6

pH of acid rain?

Answer 6

<5.6

Question 7

Normal rain

Answer 7

CO2 + H2O ←→ H2CO3

H2CO3 ←→ H+ + HCO3-

Question 8

Acid rain

Answer 8

SO2 + H2O → H2SO3

Question 9

Effects of Acid Rain

Answer 9

• Irritates respiratory tract, eye irritation
• Affects pH of bodies of water and their life
• Corrosion of basic materials (Limestone/CaCO3)

Question 10

Ways to prevent Acid Rain

Answer 10

• Catalytic convertors

* Coal pre-combustion to reduce sulfur

Question 11

Biological Oxygen Demand (BOD)

Answer 11

Amount of dissolved oxygen (in ppm) required to decompose the organic matter in water biologically, measured over 5 days

Question 12

BOD of pure water

Answer 12

<1 ppm

Question 13

BOD of polluted water

Answer 13

> 5 ppm

Question 14

Recovery ability of rivers?

Answer 14

Good, because flow of river mechanically reoxygenates the water

Question 15

Recovery ability of lakes?

Answer 15

Bad, no flow, hard for water to reoxygenate

Question 16

If sufficient oxygen present?

Answer 16

Organic material will decay aerobically into oxides, which is good

Question 17

If insufficient oxygen present?

Answer 17

Organic material will decay anaerobically, products into reduced form, usually foul smelling and toxic

Question 18

Primary Water Treatment

Answer 18

removes 60% of solid material, 1/3 of O2 demanding wastes
• Passes through coarse mechanical filter to remove large objects like sticks, paper, condoms, and rags
• Passes through grit chamber, settles sand and small objects
• Into sedimentation tank, suspended solids settle as sluge
• Flocculation: Aluminum hydroxide precipitates suspended dust particles
• Grease removed by skimming

Question 19

Secondary Water Treatment

Answer 19

removes 90% of oxygen demanding wastes
• Degrade wastes aerobically w/ oxygen and bacteria
• Trickle filters: degrades by bacteria as water trickles through stones
• Activated sludge process: sewage is aerated with pure oxygen, sludge with micro-organisms settle out

Question 20

Tertiary Water Treatment

Answer 20

removes heavy metal ions, phosphates, and nitrates
• Aluminum sulfate or calcium oxide precipitate phosphates
• Calcium hydroxide or sodium carbonate precipitate heavy metal ions
• Anaerobic denitrifying bacteria reduce them to nitrogen
• Water passed through algal ponds, algae utilizes the nitrates as nutrients.