The St. Louis Republic. [volume] (St. Louis, Mo.) 1888-1919, 1903-02-15
SAND FILTRATION MAY
DRIVE TYPHOID FROM CITIES,
Experiments of Scientists in Phia delphia and New York Prove That
This Disease disappears When the Public Is Provided With
Pure .Water-Practical Filtration Plants Now
+s@ H# .f t@g7f Prop Osed.

I enough to permit water to flow freely
through it. Upon this gravel are placed
finer toward the top.
Above the gravel is sprinkled coarse sand
to a depth of about two inches. Then is
applied fine sand in three layers. each
twelve inches thick.
There is 4 very good reason for putting
the sand on in three layers instead of in d
single layer three feet thick.
A single defect forming a channe through
the sand the size of u lead pencil would de-
feat the attainment of the desired results.
BY placing the sand in layers the chances
OF a defect are reduced to a minimum.
1t Is told of a man of very great wealth
That he once determined to obtain for his
country place a supply of water as pure as
filters would give. He studied the subject
and caused to be. constructed a filter that
wa a marvel Of perfection. Then he turned
the water upon the sand and awaited re-
suits. He was surprised when he found that
not a drop Of water was percolating through
the sand and gravel. Finally he called upon
ne had constructed his filter properly, but
that he had made a mistake In turning the
water upon the sand. which he had left
filled with air. which had held the water
suspended above It..
To avoid this mistake after the reservoir
pas been completed. water is first turned In
from the out-take pipe; that is. from below.
Inc water Is permitted to rise slowly
through the sand and gravel. driving the air
accumulations before it.
Then. when the surface has been reached,
water is turned in from above. and the first
process is reversed. Then filtration pro-
ceeds properly and naturally. But in order
TO obtain best results and speed an earlier
process is established.
THROUGH TWO FILTERS.
Water drawn from the Delaware and
Schuylkiu rivers Is much like that taken
from the Hudson-turbid and filled with
bacteria. of disease. AT Lowe Roxborough,
where the filters are now in successful OPP
GRAFTON, water Is. taken from the Schuyl-
Kill to a reservoir, In which it remains long
enough 10 hermit q nrncQOS nf SoffIorpapf r.
go on From that reservoir 1t passes to
what is known as a rough filter, which Is
nothing more than a crude copy of the real
The water in the rough filter seeps
through a bed of very coarse gravel and
sand, in which it leaves much Of its turbid-
Passing then to the real filter. the process
or puriflcation is carried on at twice the
when the water finally enters the storage
reservoir; where IT remains until drawn into
the supply pipe of the city, it is practically
as pure as can be accomplished.
OF half an acre, but at the other stations
In Philadelphia ,three-quarter-acre filters
the larger surfaced filters are Just as safe
as the smaller ones, and their speed is
greater in proportion to the size.
After one of the filters has been used
about thirty days workmen with sharp
shovels of a special make cut from the sur
face about half an inch of the sand. That
.NSS a"oy oi tndt HAS SdtlIeTeu any OIL the
impurities from the water. and as soon as
thls process has been completed the filter is
again ready for service.
This work continues for perhaps three
years. by. which time the sand on the gravel
of the filter has been reduced to a thick
ness of about Is inches the minimum thick
ness which can be allowed with safety.
Then another layer OF sand is spread is
inches thick. The time during which the
filter is out. OF service that these repairs
may be made amounts to no. more than a
few days at a time.
AMOUNT IS INCREASED.
When absolutely new, the filter is permit
ted to furnish only half a million gallons of
water per acre of surface per day. h
amount Is increased to a million gallons
per day, then to two millions, and finally
by degrees the maximum limit of six mil
lion gallons per acre Of surface per day is
reached.
Valves regulating and measuring the
amount of water passing through the filter
are in place. and by means of an automatic
bit of mechanism the amount Of water adj
mitted to the filter is regulated according to
the amount taken away.
By another bit of mechanism the pres
sure of water as 1t passes through the filter
Is registered. and In this manner the condi-
tons of the filter are always apparent to
those in charge and 1t nay be determined
to a nicely when the filter should be tenn
porarily abandoned that the impregnated
sand may be removed.
In the meantime the sand that Is skinned