Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-07-10
THE MUDDY WATER
It is Not Necessarily Dangerous to
Heath
COL. ELLIOT TALKS OF FILTRATION
He Says it Would Cost Too Much
for Washington.
NOR rs TT ECC EMIT
NOR is 1T ESSENTIAL

N ~ Is IL Il > . II N L A Il
Several times each year the Potomac
brings down to the Great Falls, and thence
to the reservoirs. millions of gallons of
water. so turbid and yellow that there Is a
general outcry against the unwholesome
supply, and there is q fear abroad lest. in
these days of intimate acquaintance
with minute animal life some one might
discover hordes of harmful bacteria in the
water that Is 50 freely used. Old in
habtants know better. They know that
they have imbibed yellow water from the
Potomac year after year. and have felt no
Ill effects. although, of course, the ochre-
colored fluid is not so nice to contemplate
or to battle in as purer grade. Col. Geo.
II. Elliot, u. 8. A, retired, until recently
the officer in charge Of the Washington
aqueduct is as competent authority on
the subject Of water supplies as there is to
be found in this country. and his opinion is
most valuable. It should therefore set at
rest many fears for the people to know
that Col. Elliot is never perturbed when
the water is roly and off-color. He believes.
of course, that 1t would be pleasanter all
around to have the water always clear, al
perfectly transparent water. as clear as
crystal. and so he is completing for Uncle
Sam the improvement Of the old receiving
reservoir at Dalecaria, which will be used
as great settling basin whenever the
rains bring tons of upper Maryland and
Virginia soil floating down the Pocomac's
broad tide.
WashlngtOn's Pure Supply.
1.-The Potomac water" said Col Elliott
tod
unwholesome. 1t is as good a supply as Is
drawn from any American river This is
the fact that 1t is often so
offensive to the eye as to make it appear
to be unfit even for bathing purposes. Dr.
Btsey, president Of the Medical Society of
the District. in an address before the ap-
committee of the House of last
year. urging an appropriation for improv-
ing the sewerage Of the city, stated that no
dreaded Of all disease germs have been
found in Potomac river water; and DR..
Wales, recently director of the museum of
hygiene of the Navy Department, at which
daily analyses of the water have been
made for some years. in a communication
to this office giving the results of chem
ical examination Of Potomac water when IT
was in turbid condition, stated that. al
though there are found in Potomac water
five forms Of micro-organisms. they are all
irpocuous and are generally present in all
river waters and added that he regarded
this water, after careful study for three
years bacteriologically, as good as any river
water in the world.
Good Conditions Above.
THAT the Potomac water should COM
pare favorably with the best river waters
might be inferred from the character OF
that part of its watershed that Is above
Great Falls. From the source Of its north
in Nor oh
miles above Great Falls, following the
course of the stream; from the source of
the south branch in West Virginia, about
the same distance, and from the source of
its principal tributary. the Shenandoah.
about 175 miles above the falls. the country
are but few large. towns on these streams.
ard I understand that none of them are
severed.
These towns range from forty-four to
this fact when considered in connection
with the well-established phenomena that
rivers. especially those that flow over rocks
and dams and those that have wide sur
purify themselves, gives assurance that
under ordinary conditions we have little to
fear from our Potomac water.
The Talk About Filters.
"But, of course, these periodical treat
ments of yellow water keep agitated in the
public mind the subject of filtration Of the
supply. which is more or less discussed all
the time in all the large cities of the coun-
try. There are two principal methods of
filtration on a large scale, the one being
known as mechanical or rapid filtration
and the other as natural or slow filtration.
The former Is somewhat broad term used
to denote those systems of water purifica-
ton in which an exceedingly rapid rate of
filtration is made possible by means of
mechanical devices for frequent, quick.
and thorough washings of the filtering ma
terials without removing them from the
filter.
1.-The filters CT this system, which is
called the American system, are cylinders
of iron or steel, containing flltering ma
terial, which is generally sand. and are
extensively used by papermakers. bottlers,
brewers, icemakers, laundrymen and in
other similar occupations. They are used
also for The filtration of the public water
supplies Of several American cities, but so
far none of the larger cities of this coun-
try have established filtration works for
their entire water supplies. The cylinders
are made vertical. in sizes up to 1211 feet
in diameter and 16 feet high, and hori-
zontal, in sizes up to ~ feet in diameter
end IS feet long The numbers of filters
are regulated by the quantity of water to
be filtered. The cleansing of the sand is
ordinarily done by means of a reverse cur
rent of water during the stirring up of the
sand by rake with long vertical teeth,
winch is reVOlVeQ horizontally by ma
through the sand The cleansing
is done daily or oftener. depending on the
turbidity of the water.
Rapid Rate.
I'm the American system there is a yield
of filtered water of 5000 to 1000 gallons
per square foot of filter surface per diem
THIS rapid rate is produced either by a
great pressure or head of water on the
sand. by which the water Is forced at a
rapid rate through it. or by frequent
cleansing Of the sand for the purpose of
removing distractions to a rapid passage
of the water. or by both.
1.-THE objection to the first is that ifs
sures or channels are liable to be forced
through the sand through which the water
may pass without any modification, and
the objection to the second is that clean
sand alone does not make an effective filter
against bacteria contained in the water.
This latter objection, 1t is claimed. has
been overcome by the use Of alum, which
Nicotine MeunfraHized