Human Waste Disposal

More than 500 pathogenic bacteria, viruses, and parasites can travel from human or animal excrement through water.

Natural ProcessesIn 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 wastewaterWater is passed through a screen to remove

debrisA floccing agent, such as alum, is added in the

water○ Flocculation process that combines small particles

into larger particles that become sedimentSuspended particles clump and settle outPathogenic organisms are killed by chlorination,

UV or ozone

Municipal Sewage Treatment

Primary Treatment - physical (mechanical) separation of large solids from the waste streamUses sticks, grit (stones), screens & filters =

sludge settles outRemoves 60% suspended solids & 30% organic

waste (ex. Bacteria)Does NOT remove phosphaste, nitrate,

pesticides, salts, radioisotopesAre 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 wasteChlorine disinfection tank kills

bacteria & removes discoloration

Ozone is an effective alternative to chlorine

Sludge – is either Sludge – is either incinerated, put in land incinerated, put in land fills, or used as fills, or used as fertilizersfertilizers

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 ContentionDraining 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)