Human Waste Disposal More than 500 pathogenic bacteria, viruses, and parasites can travel from...
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Transcript of Human Waste Disposal More than 500 pathogenic bacteria, viruses, and parasites can travel from...
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
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.