Download Human Waste Disposal

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)
