Grand Forks herald. [volume] (Grand Forks, N.D.) 1916-1955, 1922-07-17

thAn before: III this coaSulation pro-
cess bacteria which are fort the
most part attached to such particles
are also scondensed. After mixing,
the whole mass passes into the sedi-
mentation basin. AT Grand Forks We
have two such.basins holding $4,000
gallons each. They may besused
water passes through q long series Of
chambers separated by battles, the
rate of now being; about rs feet an
hour This allows the sediment to
drope.out Tor nearly "a Hours even
when Grand Forks ID. using 100000
gallons q day as it isijust now. This
process lowers the amount. OF sedi-
percent sof the bacteria. .Thes.addf-
ton Of the chemicals to the raw wa
ter Is q scientifically. controlled mat
ter and Is 90 adjusted that no free
lime nor alum remains in the water
leaving the basin; It's all used In the
reaction described. The water. now
flows In, over the surfaces Of four iil>
ter beds ihaYing q capacity OF 2,000,,--
900 gallons a. day. Z
\, New. Methods Used. i
The present filter plant is what Is
calleds"rapid ,mechanical',' as, contrast.
ed with. the slow f1lter', which we
had formerly. It consists OF four
concrete chambers about SIX feet
deep In the bottom are embedded
a series OF cast iron pipes leading
into "A large, central one On the up-
p~erFsurface Of each pipe are rows
which will not allow sand grains to
60 through. butswater passes freely.
Over this is a layer OF very large
gravel two inches or. more, In size,
and above this more gravel of smaller
sizes, making a total OF 8 to 10 inch.
es:4 b vital, part of the filter bed
isS5a body Of finely graded sand 80
inches thick. The water passing
through this sand is filtered free Of
out. perfectly clear. 1T loses the re-
mainder OF it's bacteria up to 90 per
cent. A,large part of the organic ma
terial present is oxidized and appears
as nitrAtes. Everything considered,
It would be hard to beat that wa
ter any place in the, country. The
hardness of the raw water, which
runs from 40 to 200 parts per mil-
lion, ~is&reduced to about IS and the
per million is unchanged.
Filtered water Pure.
We are not yet satisfied, however,
and we kill of the last two per cent
Of the bacteria by the addition Of
about. 2 parts per million of liquid
chlorine. This minute quantity prac-
tically sterilizes the, water as it flows
into the clear water basin. This basin
had on hand an adequate reserve for
any emergency. The further ad-
vantage of this basin is the fact that
the filters may be run slowly and
uniformly for the whole "a hours in
stead of being pushed very hard.
They are therefore maintained at
their highest efficiency all the time.
The filters are cleaned regularly
with,a stream Of air and water oper-
ating from the bottom. -
The use of water in Grand Forks is
day on the average. This includes
all purposes and is somewhat higher
than that for a good many eastern
cities OF this size, but much less than
h quota for Chicago or New York,
where a tremendous lot of wastage
occurs. 1t is the experience of most
cities that the per capita use Of wa
ter is reduced to about As gallons
where all taps are metered. There
here. -
Laboratory OF Filter. =.
The filter plant has as a part Of its
equipment a meteorological and
chemical laboratory. Samples Of tap
water are tested for their bacterial
content daily. Samples are :, drawn
from different parts of the process
periodically and tested both for bac-
terra and alkalinity, color, turbidity
hardness, ETC.. These tests determine
the amount Of the. chemicals added.
This laboratory is also called upon
to carry out the bacterial and other
tests on the city's milk samples as
they are brought in by the inspector.
The work is in charge OF Mr.. Gjerstat.