Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1903-06-08

satisfaction to all concerned. Tests of
the filters which have been made have
shown a bacterial reduction of more
than 80 per cent, and a removal of color
from about SO to 100 per cent.
The use of sulphate of alumina is
regarded as the most successful agent
for removing bacteria and color from
water. This has been demonstrated by
tests of various kinds in many places.
The system is thus described by Mr..
Weston:
ITO the water to be purified is first
added the desired quantity of Sulphate
of alumina in the form of weak solu-
ton. The water then passes slowly
through the subsistence basin where CO.
agulation takes place. Or in other
words, the Sulphate of alumina is de-
composed and a fioculent gelatinous
precipitate of aluminium hydrate is
formed. This floculent precipitate of
aluminium hydrate surrounds, en-
tangles and aggregates the suspended
substance, bacteria and inorganic mat
ter, and slowly carries them down
through the water, and results in the
greater part of them being deposited
upon the bottom of the subsistence
basin. Generally speaking, it may be
said, that the action of the aluminium
hydrate is much the same as the action
of the white of an egg in clearing tur-
bid coffee. From the subsistence basin
the coagulated water flows to, upon
and through the filter-bed, which acts
ing coagulated particles, including bac
A FIJI Of hn
mum hydrate is to unite with the solu-
bic coloring matter in the water, there
by rendering the effluent nearly color
less
THE water, as it enters the subsid-
ence basin, is given a circular motion
around the basin by a DETECTING flange,
in which the supply pipe terminates.
The upright timbers which support the
filter-bed tank and the pipes III the in
terror of the basin all tend to produce
counter currents and edieS. The rotary
movement and counter currents and
eddies bring about a much quicker sub
sidence than would otherwise be the
case in a stationary tank or in a
straight unobstructed current of water,
as they cause the coagulated particles
to meet with and overtake each other
and they are consequently thrown into
juXtaposition, thereby forming much
larger masses of greater specific grav-
ity.
I'm q very few minutes after a filter
is put in operation a thin gelatinous
layer is formed upon the top of the fill
ter-bed which adds materially to the
thorOughncss of the process of filtra-
ton.
when flter-bed has become
clogged, it is thoroughly washed by
forcing up through it a reverse flow of
water under pressure. an agitator or
mechanical rake being operated at the
same time which is of great advantage
for the efficient cleansing of the filter
bed. The wash water after passing
up through the filter-bed flows over in
to the annular trough between the fl
ter-bcd tank and the main tank, and
thence runs to waste. pump Is gen
orally required in washing a filter for
forcing the reverse flow of water up
through the filter-bed. Tho pump can
be driven by steam or water power
Steam or water power is also used for
driving the a9itatOr.
When it is necessary to wash out
the subsistence basin, the wash water,
after it has passed UP through the FL
ter-bed, is made to overflow down
through the central stand-pipe into the
subsistence basin, instead of being al
lowed to flow over into the annular
trough. The water as it enters the sub
sidence basin from the stand-pipe, is
thrown with considera BILE violence by
a curved nozzle against the lower sides
and bottom of the basin. The curved
nozzle, at the bottom of the stand
pipe, is fastened to the same vertical
shaft that carries the agitator and re-
wolves with it. From the subsistence
basin the dirty water flows to waste.