Transcript Municipal Systems - My Teacher Pages

Wastewater Treatment
Municipal Systems…
• ~75% of Canadians are on these
waste water systems
• Waste leaves your home  enters a
service line  enters sewer main 
downhill  hits a low point and is
pumped up flows to a central
station and treated
The Two Types of Sewers
Sanitary
• Storm
• Waste water from
houses, businesses
• Sent to treatment
facility
• Rain, snow melt,
runoff
• Usually untreated
and released
directly to
environment
• Storm water is
often combined
with sanitary
sewage and
overflow is
released directly
to environment
Sewage Treatment
Stage 1  Pretreatment: screening out
large
debris
Stage 2
1) Primary Treatment
 heavy organic
solids, sand, gravel
settle to bottom of
tanks, scum and
grease is released
• Primary effluent
may be released
directly to the
environment
or
Secondary Treatment
“Activated sludge
treament”
Anerobic and
areobic bacterial
digestion of sludge
Effluent is
released
or
Tertiary Treatment
• Physcial, chemical and/or biological
process
• Removes suspended or dissolved
pollutants, heavy metals, organic
chemicals and nutrients (P, N)
• Remaining sludge is transferred to
landfill, incinerated, composted or
used as fertilizer
Also…
• Most waste water in Canada also undergoes
a disinfectant process to remove diseasecausing micro-organisms
• Usually use chlorine or Ultra Violet
radiation
• Water that is released after this is
cleaner than the natural water it enters
New types of sewage
treatment
• Bioremediation  uses live organisms
(bacteria, fungi, plants)
• Phytoremediation  plants used to
improve contaminated soil or
groundwater by absorbing
contaminants or changing them into
non-toxic forms
Phytoremediation Advantages
• used to treat organic and
inorganic contaminants
• used by creating artificial
wetlands or piping effluent to
wetlands
• easy to initiate and maintain
• economical (do not need $
equipment or training)
• low environmental impact
• decreased waste to landfills
Disadvantages
• slow
• affected by climate
• will not work on contamination
below the root zone
• Plants may absorb toxic amounts
of contaminants
• toxic chemicals may build up in
plant tissue
• contaminants may move up the
food chain