Evening star. [volume] (Washington, D.C.) 1854-1972, 1886-04-30

MANY cities anu
towns on the upper Potomac which are rapid,
increasing in size, mostly finds its way in som,
form or other TO the river. The use of fertilizer
| must increase with time, while the cuttins
away of the forests brings about climatic
| changes, which allow injurious organic mattel
scattered about the land to be much NOR,
TO hnd Its way TO the source OF our water sup
ply. The floods also gather larger amount.
than formerly of the inorganic matter of the
soils through which the waters flow. AS
source OF water supply the Potomac must, from
the very nature OF things, deteriorate with the
advance of years and civilization. We there
fore, sooner or later, must come to the necessity
OF adopting some means for rendering the
water purer and more wholesome, and guard
ing 1T against epidemicai pollution. Many o.
the large cities OF Europe are now provided with
1lterlng works of great magnitude and cost
and medical And sanitary history record the
marked benent derived by the people.
THREE METHODS OF FILrERINa.
There are three methods which, either singly
or in combination with each other, have been
adopted subsidence in large reservoirs; natural
infitration into galleries built along the margin
or In or under the river, and straining through
artificially-prepared filter beds.
Our two reservoirs have a marked influence
on the quality of the water, but they are by nc
means efficient. The upper or receiving reser
r voie was aesigned principally as s9bsiding
scarcely any use in this direction. Qualification
by subsistence requires the water to remain in
quiescent state for many weeks, and this
under our southern sun, would generate and
stimulate the growth of various forms OF
aquatic lite. The unpleasant odor of the water
was due to this cause,
Qualification by filtration consists in taking
advantage of a natural deposit of sand or gravel
and using it as a filter. This system is not
applicable to our own case, since the upper
Potomac is a stream with rocky bed and banks
and any bottom land along its borders is gen.
orally of a compact, clayey nature.
The third system OF artificially prepared filter
beds has met with very general adoption.
with masony walls and bottoms OF concrete or
puddled clay. Upon the bottoms of these
basins are placed drains, radiating to ali points.
Around and above these drains is q layer OF
about two teet of broken stone, through which
the water readily flows TO the collecting drains
over this is layer of coarse gravel, then one
OF fine gravel, and then the true filter or layer
OF from one to four feet of fine sand. The until
tered water flows over the sand surface, and is
in its passage downward to the porous layers
and arterial drains below. BY means of these
and other drains the clarified wateris conveyed
to d clearwater basin.
The area OF the filter-beds which would be re-
CURED tor the city OF Washington would be
about twelve acres.
1t Is a very costly system for first construc-
ton and subsequent maintenance. Filter beds
for Washington to filter daily forty million
gallons would cost fully a million dollars, and
the yearly cost OF maintainance would be
about $40, 900.
1t is impossible to thoroughly cleanse the FL
teI-bed, and, besides, the cleansing can only
take place at quite long intervals
The amount OF water now used in Washing
ton is from twenty-five to thirty million Of gal
the water supply are completed the amount
will probably be from thirty to thirty-five mil
lion. The growth of the city will soon bring the
consumption up 10 forty million daily, and in
the plans proposed by Capt. Symons this is the
amount for which provision is made. Provision
is also made for ready expansion whenever
more water is needed.
CAPT. sYMoNs' PLAN.
ia tn fnn
thirty feet in diameter and seventeen feet high,
built OF STEEL Each filter is divided by q steel
diaphragm into two parts, the lower one g 10"
high, being entirely enclosed, and capable OF
sustaining all the hydrostatic pressure which is
required in the operation OF fitering. The
upper compartment is q 2" high and is open
to The air at top. In the lower Compartment is
the nltering material, and here the operation
ment is used Tor washing and cleansing the III
tering material which is all transferred to it in
a state OF violent agitation by hydraulic cur
upper part of the lower compartment by pipes
which distribute it at various points
OF the area. The pressure then forces
ing material to the outlet system at the bottom
where it is collected in pipes, which gradually
enlarge and join until the main outlet pipe is
reached. The operation OF filtering is carried
on uninterruptedly until it is desired to wash
the filters. This is accomplished by opening
and closing certain valves, aud thus changing
the direction of the current and forcing the
water into the filter through the outlet system
at the bottom. While this pressure is on
valves are opened at the upper end OF the ver-
teal pipes which extend from the top OF the
upper compartment through the diaphragm to
near the bottom of the lower compartment
The pressure creates Strong currents in these
vertical pipes, carrying the fltering material
up and discharging it into the upper compart-
ment in combination with water and in a state
OF violent agitation. Into this upper COM
partnent the heavy fltering materials, sand
and coke. settle, and the water bearing the
OFT in the waste pipe provided for the purpose.
When all the nltering material is thus pun ped
out from the lower to the upper compartment
and washed 1t Is replaced in its proper position
by stopping the inflow OF water and opening
valves in the diaphragm. Gravity and an
rangement Of nushing valves then force the
a state OF agitation, thus washing il again. The
first water passed through Is not completely
filtered and Is conveyed TO the upper cOmpart-
ment to be used In the next washing. When
the upper tank is filled the operation of litter
ing is resumed. Everything Ii OF the most sub
operated by hydraulic pressure. The filters
will all be independent Of each other, SO
that one or more can be withdrawn for repairs
or cleaning without interfering with the others.
The material used for altering is a mixture of
sand and powdered coke and the water is
forced through about eight feet of this mix
ture.
HOW THE WATER Is no BE TREATED.
In connection with this filtration process, the
water Is to be subjected to two other treat
ments. Previous to entering the filters the
water is to be intimately mixed with violent
agitation with about one-dfth its bulk OF atnos-
pheric air. by which q large part Of the albu-
menous gelatinous, and ammonical matter In
solution, as well as inorganic matters, will be
oxidiZed and brought to q condition In which
they can be filtered out
Chemical substances are to act upon the sOlu-
BILE impurities In the water rendering them In.
soluble, and thus capable Of removal by f1ltra-
ton or precipitation.
One OF the beat known Of these substances is
alum.
The devices adopted for the use of these sub
stances will be capable of the most perfect regu-
latiOn, SO that the amount used can be exactly
TO produce the desired effect and
can never be In excess. They will be entirely
independent, and can be used or disused 1t
pleasure.
THE PRIMARY OBJECT.
The primary object Of the system proposed IL
the removal OF the suspended impurities and
the delivery OF bright clear water; the removal
of the soluble organic matter and germ-life r.,
in the case OF our Potomac water, secondary In
Importance, but highly desirable accompAni-
ment OF the flrst.
system of filtration, aeratiOn, DC, 20 our water
supply is rs follows: The distributing reservoir,
situated Just west Of Georgetown, is divided by
q wall Into Two basins, with pa1sAge way for
Tree communication. The storage OspAcfty Of