Midterm review- Environmental Chem Flashcards
How is Ozone formed?
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.
Rate of Ozone Production equals…
rate of Ozone destruction (Steady State)
What disrupts Ozone equilibrium?
CFCs and NOx’s in the atmosphere
Cause of Acid Rain?
Presence of SOx and NOx in atmosphere
pH of pure rain?
5.65
pH of acid rain?
<5.6
Normal rain
CO2 + H2O ←→ H2CO3
H2CO3 ←→ H+ + HCO3-
Acid rain
SO2 + H2O → H2SO3
Effects of Acid Rain
- Irritates respiratory tract, eye irritation
- Affects pH of bodies of water and their life
- Corrosion of basic materials (Limestone/CaCO3)
Ways to prevent Acid Rain
- Catalytic convertors
* Coal pre-combustion to reduce sulfur
Biological Oxygen Demand (BOD)
Amount of dissolved oxygen (in ppm) required to decompose the organic matter in water biologically, measured over 5 days
BOD of pure water
<1 ppm
BOD of polluted water
> 5 ppm
Recovery ability of rivers?
Good, because flow of river mechanically reoxygenates the water
Recovery ability of lakes?
Bad, no flow, hard for water to reoxygenate
If sufficient oxygen present?
Organic material will decay aerobically into oxides, which is good
If insufficient oxygen present?
Organic material will decay anaerobically, products into reduced form, usually foul smelling and toxic
Primary Water Treatment
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
Secondary Water Treatment
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
Tertiary Water Treatment
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.
