effluent (or gray water) - peelschools.org

croatiandestructiveBiotechnology

Dec 9, 2012 (4 years and 8 months ago)

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Wastewater Management



Wastewater


Wastewater (or sewage) refers to any
water that has been used by people in
some way


Includes water from showers, sinks,
washing machines and dishwashers
(anything with a drain!)


All drains converge to a single pipe
underground leading to the outside of the
building



Septic Systems
(20% of Canadians)


Rural areas (usually)


Wastewater runs to an underground septic
tank


Inside the tank, solids and oils separate from
the water (solids sink / oils and fats float)

Lighter than water (oils/fats
)

Heavier than water (solids)

Septic Systems (continued)


Water called
effluent
(or gray water)

runs downhill
to a
drain field
of perforated pipes which are laid in
gravel
-
filled trenches.


Bacteria decompose organics in the wastewater


The purified water percolates (seeps) downwards
into the soil


Above the drain field


grass is
often the greenest!


Septic Systems (continued)


Periodically


usually every 1
-
3 years, the
septic tank needs to be pumped out.


The material pumped out is called
septage
.


Septage

is disposed of in

a) landfills

b) incinerators

c) fields

d) large lakes / oceans


Sewer Systems
(80% of Canadians)


All wastewater (and sometimes storm
water entering storm sewers) goes to a
central treatment facility


Sewage Treatment Process


Primary Treatment


-

screens and settling tanks (or clarifiers)


-

physical trapping of or sinking of solids

Secondary Treatment


-

biotechnology


-

bacterial populations


decompose organic matter


-

mixing of air with the water


-

stirring



Production of sewage
sludge

Activated Sludge = bacterial action
(decomposers)


The water that has been flowing through the
system


effluent



is treated with
chlorine

and
sometimes
UV light
or
ozone
to kill any remaining
bacteria



Tertiary Treatment
(sometimes)


-

removal of nutrients
-

such as phosphorus


-

done by reacting nutrient with a metal


-

precipitate (solid powder) forms




Effluent is then piped into rivers, lakes or the ocean

What can be done with the sludge
(also called
biosolids
)?

1.
Dump it in lakes / oceans

2.
Dump it into landfills

3.
Incinerate it
(possibly produce electricity)

4.
Spread it on fields (
cheap fertilizer)


Advantages / Disadvantages of each?


Advantages Disadvantages


Can treat large
amounts of sewage
quickly


Uses a fairly small
area of land


The facility is
expensive to build
and maintain


Effluent may still
contain pathogens
and some chemicals
(e.g. pharmaceuticals
and medicines)


Requires water!

Large
-
Scale

Sewage Treatment

Peel Region (Mississauga, Brampton
and Caledon)


Two wastewater facilities on the shores of
Lake Ontario (Lakeview and Clarkson)


Other small ones (e.g. Inglewood
discharges effluent into the Credit River)


http://www.peelregion.ca/pw/water/sewag
e
-
trtmt/