The Minneapolis journal. [volume] (Minneapolis, Minn.) 1888-1939, 1904-09-09
the great lakes, but softer than that Of
most rivers.
Methods of Treatment.

As to methods Of treatment, the com
tration at Little Falls, n. Y; Ithaca
and Albany, N. Y; Philadelphia, Super
ior and Ashland, Wis, and plants under
construction at Washington, Philadel-
phia an0 Yonkers; also works at St.
Louis, Quincy and Cincinnati.
The two principal methods Of fltra-
tion are sand and mechanical filtration.
slowly thru horizontal layer of sand
which removes 80 per cent of bacteria
and also other Objectionable substances.
In mechanical filtration the water is
also passed thru sand layer, but at a
much higher rate, and publication is Sc
cnred as result of a preliminary chemi-
physical character Of Impurities that
they are more easily strained out.
The commission declare in favor of
sulphate of alunina as the best coagu-
liant for the treatment of Mississippi
water at Minneapolis.
Sand filtration produces satisfactory
results. The only question that serious
" troubled the commission was as to
the practicability Of operating sand fl
ters in this climate. They find, how
ever, that it is done successfully at Ash
land and Superior, Wis, where the
filters are covered with masonry. vault:
earth, fully protecting the filters from
the injurious action of the frost.
The most important object to be &C:
cOrplished by filtration is the removal
of disease proc ucing qualities in the
water: In: this, respect the results OBJ
tanned for filters on the two systems
operated slSilfully ~, to give the best re
suits Of which it is CAPABLE
For turbld water mechanical filter!
are best. Coloring matter cannot b.
removed by sand filtration, altho tn
removal Of suspended matter woult
clear up the water approximately 2;
per cent. The chemical treatment i,
connection with mechanical filter act
ing upon the coloring matter practical
ly removes all Of it.
Sand Filtration Cheaper.
Taking into account the cost of con
sstrnction, and of operation, sand filtra
ton is cheaper, The cost of construc
ton of sand filters is greater than o
mechanical filters, but the cost of opera
tion is less.
The commission investigated a treat
mont, Of the water with common lin
for the purpose, Of softeniing it., Thi
but also add greatly to the usefulnes
Of the water for domestic and indus
trial purpose. They do not recommen
such treatment where the water is n
harder than that Of the Mississippi.
Other processes of treating the VIZ
} ter have been considered. Sterilizatio
by. electrical discharges Is attractive
strate practical results. Treatment b
= ozcne is more attractive, and rests upo
carefully ~ made experiments. TIL
} process has not been applied in SUI
cessful commercial way. and will pro1
ably be too expensive for serious col
; sideration. Its. use in, any event wi
not take the place Of filtration 1t
| only used as an added safeguard
} connection with it.
Sites for Filtration Beds.
, The commission then proceeds to
consideration of sites for filters. Fiy
locations are discussed. First, near tt
reservoir and above it. This would r
a head ten feet greater than at presen
The pumps are equal to it. The purife
water would flow up into the reserve
+. and be distributed from it precisely ;
at present. The project has the adva
7 tage that the distribution system is le
{ entirely undisturbed. It has this a.
vantage that it fails to make use of tt
. present reservoirs for sedimentation |
. which they are well adapted, and tn,
! 1t IS necessary to use them for storas
! ! and distribution of the filtered waite
= to which they are not well adapted, b
u cause filtered water. deteriorates whe
Il stored IN open reservoirs.
Other Plans Discussed.
T The mex" plan is to locate the fltra
j ing plant near the reservoir and belo
= it, With this arrangement the wat
+ would be pumped into the present re
n ervoir, and after passing it would
= to the publication plant, and from tn;
a to new distributing reservoir. at
q lower elevation, and covered. The t
z biography Of the land is favorable. Sa1
! filters with a capacity Of 2O,0oO,O(
gallons per day does not represent IL
k full capacity of the site. This arrang
s me mel IS more nS1 satisfactory than to !
$ ervoir. It's disadvantage is that
d would reduce the. elevation at viii,
e the filtered water is available, and co
sequently to maintain the pressure
l. all parts Of the city, it would be ne
essary to provide somewhat larger