1. PREVENTING AND REDUCING SURFACE WATER POLLUTION
The U.S. Clean Water Act sets standards for allowed levels of key water pollutants polluters to get permits.
Goal: maintain physical, chemical, biological integrity of water.
Good for point source pollution but needs to improve regulations for nonpoint.

2. Reducing Water Pollution through Sewage Treatment
Septic tanks and various levels of sewage treatment can reduce point-source water pollution.
septic tank, a distribution box, and a leach field

3. Reducing Water Pollution through Sewage Treatment
Raw sewage undergoes:
Primary sewage treatment:
a physical process that uses screens and a grit tank to remove large floating objects by settling. Ex. Condoms, tampons, corn, guns, body parts
Primary
Bar screen
Grit chamber
Settling tank
Sludge

4. Secondary sewage treatment:
a biological process in which aerobic bacteria remove biodegradable, oxygen demanding organic wastes. Ex. Human waste, soaps, detergents, food waste, e. coli, phosphates, nitrates
Aeration tank: removes organic materials and nutrients using bacteria. Bacteria need lots of oxygen because they are aerobic decomposers

5. Settling tank Secondary Chlorine disinfection tank Aeration tank
To river, lake,
or ocean
Activated sludge
(kills bacteria)
Air pump
Sludge digester
Settling tank
Sludge drying bed

6. Ex. E. coli, coliform, giardia, cholera, viruses
Water is chlorinated to remove coloration and to kill disease-carrying bacteria and some viruses (disinfect).
Ex. E. coli, coliform, giardia, cholera, viruses
Water is given time to react with chlorine in the chlorine chamber

7. Plant effluent: water that leaves the plant.

8. Activated sludge in here!
Primary
Secondary
Chlorine
disinfection tank
Bar screen
Grit chamber
Settling tank
Aeration tank
Settling tank
To river, lake,
or ocean
Sludge
Raw sewage
from sewers
(kills bacteria)
CAKE!!!!
Activated sludge
Air pump
Sludge digester
Sludge is combined with anaerobic bacteria
Disposed of
in landfill or ocean or applied to cropland,
pasture, or rangeland
Figure 21.16
Solutions: primary and secondary sewage treatment.
Sludge drying bed
Fig , p. 511

9. Reducing Water Pollution through Sewage Treatment
Advanced or tertiary sewage treatment:
chemical and physical processes to remove nitrates and phosphates
Sand for extra filtration UV

10. Other ways to filter…
Charcoal, cloth, nano filters

11. Not so good to burn it, put it in the ocean, put it in a landfill
Most ecologically responsible way to deal with cake is to treat it with heat to kill harmful bacteria, removal of toxic metals, and using as fertilizer.
Not so good to burn it, put it in the ocean, put it in a landfill
What problems arise from putting it in a landfill?
Takes up space
Contaminate groundwater with heavy metals
Methane released during decomposition
You have to drive the waste to the landfill

12. Sewage sludge can be used as a soil conditioner but this can cause health problems if it contains infectious bacteria and toxic chemicals.
Problems:
Contaminate ground water
Bacteria can contaminate crops
Heavy metals enter food chain
Runoff can contaminate surface water

13. Using Laws to Protect Drinking Water
U.S Safe Drinking Water Act:
requires the EPA to establish national drinking water standards
(maximum contaminant levels) for any pollutant that may have adverse effects on human health.
Ex. protect drinking water and its sources: rivers, lakes, reservoirs, springs, and ground water wells
Doesn’t apply to bottled water. (that is regulated by FDA)