The Providence news. (Providence [R.I.]) 1891-1906, 1893-02-24
What Effect II Has in Freeing
Water From Impurities.
A PLAN UNLIKE Mr.. SHEDD'S.
Places Where Alumina II Being Used,
and the Filtered Water shows no
Trace OF It = Analysis Of Pawtuxet
Water Filtered Through AIumina-

The plans which the NEWS gave of City
Engineer Shedd have caused considerable
comment and criticism among those who
have given the subject attention. All
shades OF opinion are current from that
which favors the plan to that which con-
siders it worthless.
Those who oppose the plan OF course
are among the advocates Of the use OF
mechanical filters aud alumina as the
best method OF combining CELEBRITY cheap
ness and efficiency. The alumina advo-
Gates have the floor today and the NEWS
herewith presents ,me OF their views.
Tue opposition TO the idea OF slow
filter dependent upon only slight pres
sure like this used abroad comes from
tie fact that To obtain the same results
rs the foreign filter beds the same per-
fectly constructed filter beds must be
made. These REQUIRE years. OF time and
and expense IL is said to be impossible to
obtain satisfactory results unless alum
ina Is used as there Is no medium be-
tween natural filter bed acres in extent
aud one that uses artificial means u col
lect the impurities.
Sulphate of Alumlna is Of course sub
iecs to accidents and misuse, but no
harmful result can come from its use IL
proper care is used. Aud no moro care
is necessary in the use OF alumina than
in the case of an ordinary gravity filter
without alumina, and By no means 81
much care as Is required In maintaining
a natural filter Dea.
The amount Of alumina Is so small,
say the advocates of its use, that IL Is
practically impossible for it TO get
through the filter. Experiments at Law
renee show that one-half OF a grain TO a
gallon OF water will do nearly as perfect
work as one grain to gallon. In other
words when the filtration is once started
and gelatinous coating is formed over
the sand there is little need of any
great quantity OF alumina.
The question Of neither alumina will
get through filter into the filtered
water depends entirely upon the pres
sure used to force the water through.
he opponents of its use point to Long
Branch as an iilustration OF its dangers
But at Long Brancn the filters are air
tIght, aud the pressure of water is $50
pounds per square inch. Here. however
the plan proposed contemplates head OF
water, not exceeding eight or nine feet,
or less than five pounds per SOU re inch.
One OF the best known commercial tests
for the presence OF alumina is used con
tinuously In dying establishments. Dye
works need to have only the purest
water, aud most or them seek sources OF
soft water supply. The slightest presence
OF alumina would spoil the colors AMI
render them useless. Many, howeves,
are today using uttered water and
aumina as a coagulent. Their test con-
slsts in taking a little logwood coloring
solution and pouring 1t into the water
to be tested. If IL cont aims alumina, even
In a slight degree. the colors will become
set.
Another place where alumina is con-
stautly used In filtering water is sugar
refineries. In these the slightest trace
of alumina would set the color in the
brown sugars and it would be impossible
TO bleach them. No refinery tnat uses
water containing alumina can produce
white sugar
In Philadelphia, however, the franklin
sugar retineries have been using alumina
filters for three years. Their water is
taken directly from the Delaware aud is
muddy with filth and sewage in suspen-
pension. Their sugars are. however,
among the best produced in the country.
Their filters have about 6-feet head of
water and the tlteriug sand has not been
renewed or added to since they were put
in.
Mr.. Claus Spreckels has just placed n
jntract with the manufacturers of an
alumina filter to put their filters in his
California refineries which will filter
1000, 600 gallons per day. IL is also said
that the same firm have contracts to put
the Sugar Trust.
In he Franklin refinerles the amount
OF alumina used is one grain per gallon
and the filtered water shows no trace of
its presence. This filter has two other
advantages. II can be cleensed perfectly
in three minutes, and very little time is
lost iu its use. IL has also mechanic Il
AIRY steam can be injected and the whole
filter bed subjected TO a sterilizing pro-
cess by heating the water To u boiling
point before IL is washed out.
Another illustration of the growing
favor Of the alu nina filter is To be found
In the public WORKS of the city of Phila-
delphia as long ago as 1888 Prof Leeds
of Stevens Institute was asked by the
city to present some plan for purifying
water Tor the city. AT that time he
recommended an alumina litter, and
after ten years OF consideration the city
has just passed through its lower branch
a resolution to erect a filter plant capt
BILE of filtering $1,000. 900 gallons OF water
daily.
what Pswtuxet Shows.
AS to the effect of this system Of filtra,
tion on Pawtuxet water there is good
testimony at hand. Experts have tested
the water, both before aud after filtering.
Oncrest made by "A chemist showed S3s
bacteria of various Kinds In cubic cen
timeter about one teaspoonfu) and after
filtration there were only tnirty-three
bacteria left.
H. X. Dunham, the specialist OF the
Carnegie Laboratory, tested some Paw.
tuxet water that had been subjected 10
the nj INN system OF tiltration. In all
cases he made duplicate tests. The re.
suits that ne obtained from four dupli-
cate tests before aud after filtering are as
follows:
Sample No. contained 1854 bacteria
per cubic centimeter before filtration
Alter filtration there were left only -
bacteria.
sample No 9 contained 1.053 bacteria
before filtration and l05 aiterward.
Sample No. contained 740 bacteria be-
fore filtration aud % afterwarh.
Sample No. contained $3.50 bacteria
before filtration and only 80 after Icing
put through the 6lter.
The average uQNoval OF bacteria was
about 95 to "a pei cent.
In his report Prof Dunham laid special
stress on the fact that all OF the impuri.
ties upon which bacteria subsist had beer
removed, and those left i'm the water
would die before they left the reservoir
in which the water might be stored
The filtered water showed no trace o.
alumina