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 Grit chamber Settling tank Bar screen Sludge

4. Secondary sewage treatment: • a biological process in which aerobic bacteria removebiodegradable, 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. Secondary Chlorine disinfection tank Aeration tank Settling tank To river, lake, or ocean (kills bacteria) Activated sludge Air pump Sludge digester Settling tank Sludge drying bed

6. 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) Activated sludge CAKE!!!! Air pump Sludge digester Sludge is combined with anaerobic bacteria Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland Sludge drying bed Fig. 21-16, 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. 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)