The times. [volume] (Richmond, Va.) 1890-1903, 1900-01-28
SAND FILTRATIONS

LlOn anu uGCGSSlldlluS 1TGQucul ESCIlp-
lngs.
SAND sFILTRATIONS.
The first of the above difficulties would
make it necessary in applying this method
to James river water to have filter bed>
covering many acres The normal rate
of filtration by this method should be
from 100000 to S00,o00,0G0 gallons per
day, whereas the experimental filter,
V tJdh was constructed III one of the
three-mile locks for the purpose Of max
ing definite determinations in this exami-
.tion gave flow at the rate of less
tnan one-half a million. gallons per day
per acre. This alone would be an insu-
perable objection to natural sand Ultra
ton aside from several others, to Whlcn
attention was directed in this report.
Tho most interesting series OF expert
ments conducted during this investiga-
ton was in connection with the results
OF sedimentation. The western division
OF the new reservoir was filled with mud
DIV water on the 18th of last August. and
systematic tests Of the water thus stored
were made by Drs. Levy and 41allet. The
results Of these tests We're most salts
factory, although. as is we'll known, mud
DIV James river water will not become en-
, tirely clear, even after weeks of sedimen-
ation yet very considerable improve
Elent is secured.
FOB DRINKING PURPOSES.
The chief point of interest in connec-
ton with these tests was the demonstra-
ton Of the fact that the number OF
bacteria in the water thus stored stead
ily decreased. At the end Of ten days on
" 70 Le- cent of the original rum
Der remained, thus refutins the opinion
advanced several years ago that storage
of James river water would render 1t un-
ii. c,t dr. mixing purposes on account or
prolferation of basterla.
A third system was tested in the course
of these investigations, namely: Mechan-
icrl fiji alton This name, which Is the,
one in universal use, is decidedly mis-,
leading, since the word mechanical, as
u ed fIr, refers not to 'tiltratio 1, but
to the method employed for cleansing the
iI.er beu Mechanical filtration involves
TIC use az some coagulent, usually Hlt11n J.
The effect Of this coagulent is to gather
up the fine suspended matter into coarser
clumps, the removal of which may then
be accomplished by a filter of far coarser,
f--xtnr.. an is demanded where a oco-
agulent IS used.
No TRACE OF ALUM.
This method is entirely applicable to
Jlnc. river water, as the rate Of flow
is at least one hundred times as great
as in natural sand filtration. Owing to
recent improvements In filters OF this
type the water furnished contains no
trace OF alum. It was shown that pre-
liminary sedimentation is essential in or
der to secure desired efficiency aid
economy with this system.
@8 The final recomme ndation Of DIR. Levy,
which agreed in every respect with that
of Or. Mallet and Superintendent OF the
Water Works, advocated the CONSTRUCTION
of a large settling basin. holding 200,-
0Oo,0 gallons, or twenty days supply
for our city, at the present rate OF con-
sumption. It was shown by consideration.
Of the condition Of the river for 1899 that
such basin used simply as storage:
reservoir would have furnished fairly.
clear water for nearly three-fourths OF
the year. while during the remaining
f1urth. water wonderfully tmp.ovcl by
standardization would Rave been secured.
- ADVANTAGE OF BASIN.
Another advantage of this settling ba
sin would be that the canal. which serves
at present for both the supply of the new
reservoir and as motive power for the
pumps, would be used only for the latter
purp Since the streams entering
this canal are to be considered the most
important source Of possible pollution
this feature of the proposed plan Is of
the L tmos importance.
m addition to She above mem
b tened merits OF settling basin; It
would furthermore form an essential
part OF the equipment required for any
method OF filtration, the adoption OF
which may later on be thought desirab bic 1
Or. NIallei,s Report.
Following IS a brief review Of the res res
rcrt Il submitted TO the COMMITTEES ssans
Water by DR.. J x W. ia1let, Of the
School of Chemistry at the University
EofssVirginia: 80
From the chemical and bacteriolo-s
sgical examinatio made-the latter bys
sbe any ground for uneasiness as to the
present Wholesomenessof the James rW-s
FER water supply of n edmond The chief
Occasion for apprehension IN regard to
the future Is the possibility Of local con-
termination from sources within the city
Itself or in the: outlying district sim-l
4 nediately above Il. ANY, danger from
esuch: sources would SbeE ohyiated by taking
In sthesrfverswatera @ g point further up
stream.
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Is sla1gs stosa hastAs ScaDahlssoff