The Birmingham age-herald. [volume] (Birmingham, Ala.) 1902-1950, 1903-03-29
sssecOns of fit tub

cross-sectional view of iron fit
When the f1ltering plants now being
Installed by the Birmingham Water
Works company at North Birmingham
and Cahaba are completed, there will be
only one other mechanical filter plant In
the United States larger than Birmlng
ham will have The plants being con-
structed by the local con pany art. ac-
cording to what is known as the Ameri-
can system.
The mechanical filtration of water for
public use has never been successful untn
within the last ten or fifteen years, aud
Its success now is due largely to the use
of sedimentation basins. That is, water
which is to be filtered must stand for a
time in order to deposit in the form of
sediment any solid substances it may
hold in suspension. The filtration of
water which has been in a constant state
Of agitation up to the time of entering
the filter is never successful.
Most Modern.
The two plants being installed by the
Birmingham company are the most mod
ern and up-to-date designs 1t is possible
to obtain. The one at North Birmingham
is smaller than the one at the reservoirs
on Shades Mountain and will therefore
be completed first 1t is expected that
filtered water will be furnished by it as
early as August Of this year.
a detailed inspection of the work at
North Birmingham shows that very sat
isfactory progress is being made, and
a better idea of how the water is filtered
can be had at the present time than later
when the parts will all be under cover.
The filter plant proper consists of
large clear water basin to hold the filter
ed product, and ten immense iron tubs,
each of which contains a filtering appar-
atus separate and distinct from all the
others.
Each filter tub is nine feet deep and
fifteen feet in diameter, and contains a
false bottom, below which the filtered
water collects in tn false bottom are
about $50 one-ineh holes into which are
screwed little brass strainers shaped
something like a tea-strainer.
On top of the false bottom is a 6-inch
layer of fine gravel sieved through a
A-inch mesh. Above the gravel is A
foot layer of sand This sand has to be
shipped in from Wisconsin because an
oval-shaped grain with no sharp points
is necessary so 1t will not pack too tight
in the filter.
Water is then run in on top of the sand
by specially adapted trough devise
which feeds 1t evenly to the different
parts of the surface Of the sand.
Percolates Through Sand.
1t then percolates through the sand and
gravel becoming thoroughly purified.
then runs through the little strainers
into the space below the false bottom of
the tub From here 1t runs by gravita-
ton into the clear water basin below,
and from this basin 1t is pumped out
into the mains Of the city at the rate
of 5000 600 gallons every "a hours.
This process thoroughly clarifies the
water. The mud originally contained in
1t settles on top of the layer of sand and
the thin gelatinous scum which forms
even assists in the filtration. 1t will be
necessary about every "A hours to clean
the filters, but not because muddy water
begins to run through. 1t is impossible
for water which gets through the filter
to be muddy.
The filters are cleaned solely in order
to maintain their capacity The more
mud that collects on top of the sand the
more plowly the water will run
The cleaning process itself is rather
unique. Water is turned into the space
of the tub below the false bottom and is
forced through the filter backwards, col
lectng the mud that has gathered on the
sand, carrying it back into the trough
inside the tub and then off through pipes
TO the sewtr
The North Birmingham plant when
completed will have a capacity of about
100000 gallons per day.
The clear water basin, located undec
the tubs, is ten feet deep is cemented on
all sides and has a capacity of 100000 gal
Ions.
Source of Supply.
The source Of the water supply for the
North Birmingham station will be Five
Mile creek as in the past. From the creek
an artificial canal six miles long was cut
several years ago. Water runs from this
canal through screens into 4S-inch iron
pipe which carries 1t by gravitation to the
open reservoir which has a capacity of
between 100000 and 12,0oOO0O gallons.
The reservoir is equipped with several
baffle walls with openings on alternate
ends so that the water to travel from one
end to the other must move in a cir
cuitous route. which aids sedmentaton.
When the filters are completed two CEN
trifugal pumps will lift the water from
the reservoir to the filter tubs and when
It finally gets to the clear water basin
the gigantic Deane and Wood pumps will
force it into the mains.
The Cahaba plant. located on top os
Shades mountain, will be similar in con-
struction to the one at North Birming-
ham except that it will have a much
greater capacity. There will be thirty