Evening star., 1901-02-19
FILTRATION REPORT
Presented to the Senate by Mr.,
Mcmillan.
SLOW SAND PROCESS ADVISED
Result of the Inquiry by the Com
mission of Experts.
GU ESTION OF THE COST

4
| Columbia today reported in favor of the
| adoption for this city of the slow sand
| system of water filtration, modified by the
| use of coagulants whenever the waters OF
| the Potomac are so turbid and turbid for
| SO long a period as to make the use Of a
| coagulant desirable. The committee does
! not specify what site is to be used for the
| filtration beds, as several sites are said to
| be available, each with its advantages.
| The beds might be located along the line
| of the conduit the committee says,
| where land is cheap; or, if a site near the
| Howard University reservoir should be Sc
| lected, the result would be a considerable
! and highly desirable addition to the park
| system. At the same time the pumping re-
| quired to deliver the water to the filter beds
| would give a very considerable additional
| head to the gravity supply, thus diminish
| ing the amount of so-called high service re-
| quired. This additional head for the grav-
| ity system Is particularly desirable, for
| the reason that even the completion of the
Howard University reservoir will not give
an entirely satisfactory head of water on
capitol Hill and in certain other parts of
| the city that depend on the gravity ser
| vice"
Recommendations of the Experts.
The report of the committee Is based
| largely on recommends tions by the COM
mission Of experts, consisting Of Rudolph
Herring, George W. Fuller and Allen Hazen,
which has lately made thorough investi-
cation Of conditions in the District relating
TO the problem of filtering Potomac water.
In making a report to the Senate in
Sponse to q resolution of December 20, 1900,
calling upon the District committee TO re-
port upon the relative advantages of the
called mechanical system and of the slow
sand system of water filtration for cities,
-i..U-G hn INV titrr,f ffp,-
made by the corps of engineers, United
States army, and rectes that $2Oo,G1D was
appropriated last yea> to be expended on
those portions of filter plant which would
be necessary in either case whether the
mechanical system the slow sand system
of filtration should be adopted.
The appropriation was made in this way
because more time was desired to decide
upon the system to be adopted by the Dis
trict than could properly 1e given within
the limited time then at the disposal of
Congress. Col. Miller reported that the
suspended clay in fine particles in Potomac
water made It practically impossible to use
the slow sand system of filtration, and he
therefore recommended the adoption OF the
rapid or mechanical system of filtration.
The Medical Society of the District of
Columbia, the Board of Trade and the Bust
ness Mems Association attacked this re-
port, arguing that the use of alum as a
cOaSulant was in itself objectionable, and
that the mechanical process was inferior
to the slow sand system as a means of re-
moving those forms of pollution that are
the cause Of typhoid fever.
The New York Inquiry.
AN inquiry conducted by this committee
in New York city on January 4, 1901 the
report says, was attended by men who
have made for themselves the highest rep
utation in the matter of the construction
and operation Of filters for public water
supplies. No large filter plant, either In
existence projected. nnrpnrpSpptp6
at that meeting.
The result of this discussion established
the fact that the slow sand filter wherever
1t had been put into operation, had produced
uniformly good results both in clearing the
water from turbidity and also in removing
bacteria. The theory was main tanned, how
ever, that different types of water require
different treatment, and that for waters
that are simply polluted the slow sand filter
Is to be preferred; whereas for very turbid
waters, containing fine particles of clay, the
use Ct q coagulant is necessary.
From this theory but one expert dis
sented, Mr.. John w. Hill, who has had ex-
perience In the study of the water supply
at Cincinnati, Philadelphia and other cities
Mr.. Hill maintained that he had never
found a water for which he would not rec
ommend the slow sand filter, Cincinnati be-
Ing no exception. With the exception of
Mr.. Hill, the experts were of the opinion
that the mechanical system, when properly
operated, was capable Of producing su-
perior results to the clearness of the
water and equally good results with the
sand filter to bacterial efficiency 1t was
admitted that such results had not been
uniformly attained; and this was held to be
due to a variety of causes which had pre-
vented the mechanical systems from being
managed with a view to obtaining the high
est efficiency of which they were capable.
The Use of the Two Systems.
There are today no cities of the size of
Washington using the mechanical system
of filtration, but, the contrary, Law
renee. Mass, and Albany, N. Y, are sue
cessfully operating slow sand filters, and
Pittsburg Is putting in slow sand system
Philadelphia is about to install slow
sand filter plant for three-fourths of her
water supply, and is to construct a me-
chanical plant for the other fourth merely
for temporary use, the expectation being
that the water supply at that particular
point Will be exhausted within a definite
time. At Cincinnati a mechanical system
has been recommended; at Louisville, Ky,
and Paterson, n. j., also the mechanical
system is to be used. The specifications,
however. call for a type of filters differing
radically from any plant now in operation.
The fact that slow sand filters have been
doing highly efficient work for three-quar
ters of century, under widely diverse con-
ditfons of operation, in the largest cities of
the world would make the argument from
experience conclusive in favor of the slow
sand system, provided the Potomac river
water were Of the type that can be treated
without tne use OF q cOdSulant at all times.
The further fact was developed that the
cost of the two systems during q series OF
years is about equal, the first cost Of the
lands necessary for the slow sand filter be-
ing offset by the annual cost of the alum
used a coagulant."
The report of the experts, Messrs Her.
ing, Fuller and Hazen, reviews briefly but
thoroughly the cha ristics of Potomac
water and their reasons for recommending
the slow sand system of filtration.
A Controlling Element.
1.-THE character of the raw water is often
an element of controlling Importance in de-
Gliding a question of this kind" the ex-
perts say. Generally speaking, sand fill
ters are best adapted to purifying waters
that are not extremely turbid, and me-
chanical filters have marked advantages in
the publication and Qualification of waters
which for considerable periods are very
turbid 1t was, therefore. necessary for us
to examine all the available evidence re-.
garding the character of the Potomac wa
te-.
cat those places In this country where
observations have been taken on the
amount and character of turbidity of diff
ferent river waters the methods used have
not everywhere been the same To com
pare the Washington data, which cover a