Human Waste Disposal  More than 500 pathogenic bacteria, viruses, and parasites can travel from human or animal excrement through water.  Natural Processes In many areas, outdoor urination and defecation is the norm. ○ When population densities are low, natural processes can quickly eliminate waste.

 Process for purification of and treatment of municipal wastewater Water is passed through a screen to remove debris A floccing agent, such as alum, is added in the water ○ Flocculation process that combines small particles into larger particles that become sediment Suspended particles clump and settle out Pathogenic organisms are killed by chlorination, UV or ozone

Municipal Sewage Treatment  Primary Treatment - physical (mechanical) separation of large solids from the waste stream Uses sticks, grit (stones), screens & filters = sludge settles out Removes 60% suspended solids & 30% organic waste (ex. Bacteria) Does NOT remove phosphaste, nitrate, pesticides, salts, radioisotopes Are not designed to remove pharmaceutical chemicals from wastewater

 Secondary Treatment - biological degradation of dissolved organic compounds Effluent from primary treatment transferred into trickling bed, or aeration tank or to activated sludge treatment ○ Aerobic bacteria filter out 90% of biodegradable organic waste Chlorine disinfection tank kills bacteria & removes discoloration Ozone is an effective alternative to chlorine Sludge – is either incinerated, put in land fills, or used as fertilizers

Cost  The cost per unit of pollutants removed increases as the concentration of the pollutant decreases  Removing smaller and smaller pollutants require more processing and more sophisticated removal techniques

 Tertiary Treatment (advanced treatment) – special chemical and physical treatment that remove specific pollutants after primary & secondary treatment. Chemicals, or natural wetlands. Growing interest in membrane technology – reverse osmosis, ultrafiltration (too $$$) Wastewater Gardens – artificial wetland system used to treat small amounts of sewage

Municipal Sewage Treatment

Areas of Progress  In 1998, EPA switched regulatory approaches. Rather than issue standards on a site by site approach, the focus is now on watershed-level monitoring and protection. States are required to identify waters not meeting water quality goals and develop total maximum daily loads for each pollutant and each listed water body.

WATER LEGISLATION  Clean Water Act (1972) Goal was to return all US surface waters to “fishable and swimmable” conditions. ○ For Point Sources, Discharge Permits and Best Practicable Control Technology are required. Set zero discharge for 126 priority toxic pollutants.

Clean Water Act (1972/1977)  Addressed regulations for point source pollutants, non-point pollutants, & municipal waste treatment plants  Areas of Contention Draining or Filling of Wetlands ○ Many consider this taking of private land. Un-funded Mandates ○ State or local governments must spend monies not repaid by Congress.

Other Water Legislation  Safe Drinking Water Act (1974) – established max. containment levels for pollutants  Great Lakes Water Quality Agreement (1972)  London Dumping Convention (1990)