The Providence news. (Providence [R.I.]) 1891-1906, 1893-02-21

The Common Council met last evening
In regular session. 1t was very I'm
portant meeting as the Council voted to
appropriate $50. 900 for the filtration OF
the Pawtuxet water. The resolution 10
hire 100000 for Davis park was con-
Cured in after protracted debate ana
considerable routine business transacted.
The special order, the report OF the
ioint special committee on the causes OF
pollution of the Pawtuxet river and the
hest method OF filtrarion and the resolu-
tion carving into effect the report OF the
committee. came up at the opening OF
the meeting.
Mr.. Barney said that the COMMITTEES
had gone into the matter ms thoroughly
as it was possible and had found that the
water which the citv Is using at the
present time is no worse than the water
when IL first became the city water
in 1869 The water. however, was
darker at present and the pos
sbility of pollution i somewhat
dangerous Science teaches that yell
low water is not necessarily. dan
cerous, but it must not be too dark. The
danger of contamination by sewage still
exists, however. though the efforts made
have caused a great decrease in the
amount of sewag that is now let into
the river. The case of Hamburg was
cited and the fact recalled that there was
no doubt that the cholera had come TO
that city last summer through the sew
age that had been dumped into
the EIbe. At the same time
the city of Altoona on the opposite 81 d. of
the Elbe had filtered the water and had
had practically no cholera. The question
of filtration had been carefully consld-
cred, and the cost of a new plant above
the sources of pollution. IL was found
that the expense Of engineering aud dam
ages to lhe manufacturers along the
stream would amount to high up in the
millions. The work Of the commissioner
of public works and his assistants had
done much to improve the water. Dut the
working in of impurities at the time OF
heavy rains IL was impossible to prevent
Thus il was found that the only way to
protect the city was to filter the water.
just Been Converted.
Mr.. Barney said that he had only since
being appointed on this commit &c been
converted to filtration as he hld found
what had been done in this matter and
how much the death rate of cities that
had filtered their city water, had been
lowered. IL would be practically certain
TO keep out all contagious disease
from this source by the use
of filtration partly because the
health were the easiest TO destroy. thas
been found that 1t is possible TO remove
all the germs of typhoid aud cholera by
the proper kind of filtration. He took up
and discussed the merits OF natural
filter, stating that though the work had
been done well the cost had been
to other cities, especially In Europe,
very great. The mechanical or COM
mercial filters were perhaps no more
thorough, but the gravity filter could
be cleaned much more easily. The
pressure filth becomes clogged and the
very matter which IL is desired to check,
is forced through and passes out in the
water. The committee had come TO the
conclusion that the gravity filter is the
best. This is "a basin made of masonry i'm
which is laid first layer of coarse stone,
i then layer of finer stone. then coarse
gravel, then finer gravel, then coarse
sand, and on top of all a heavy layer of
finer sand. 1t has been found that it is
necessary 10 have something pres
ent in the beds to assist in filtra-
tion. 1t has been supposed that
colonies of antagonistic bacteria,
which would destroy the dangerous
bacteria was necessary but IL is found by
experiment that the most eflicacious
assistant is chemical solution which
will coagulate the water. The best
solution is a substance called sulphate OF
alumina which clarifies the water by
The advantage Of the mechanical filters
is the speei with which the water eau be
run through aud the consequent great
amount that can be filtered in given
time.
The Mechanical Filter.
The mechanical filter. with the assist
ance of sulphate of alumina does
better work than the natural NIL
ter as well as doing 1t quicker. The
expense of the me chanIcal filter is SO
small in comparison To that OF the
natural filter that IL forms another argu-
meut In its favor. OF the different filters
the committee does not recommend any
as the principle is very much the same
aud the question comes down to which
company can give the best guarantee and
will construct the plant most reasonably,
regarding expense, aud this company Is
the one this committee is in favor OF
having the contract The gas cannot be
taken out or the ater by filtration, but
aeration must be resorted 20, which is
provided for IN many of the systems.
The use OF an air lift instead Of n plunge
pump was recommended. as this would
provide means Of aerstion. The cost
Of slSO,OOO ought to cover the plant with
the air lift and pumping station.
Mr.. Parkhurst asked how it could be
ascertained what percentage OF removal
plished, and also how great a PERCENTAGE
OF the sulpbate OF alumina was To be
used.
Mr.. Barney replied that proofs show
that with very small rate OF filtration
an average removal Of 97lf per cent OF the
impurities was obtained. The No. 5
filter, n natural flter in use Ia Lawrence
and aid TO be the most perfect natural
filter in the world, after a series Of ex
periments was shown also TO remove 05ls
per cent OF the matter ia suspension but
that during two OF the months Of the ex-
periuents the removal was only 90 aud
p5 per ceut. Repeated experiments by
chemists add by our own city physician
showed that the results were v ~ excel
lent In tne case OF mechanical filters.
As 20 the amount OF alumen Co be used
that would depend on the condition OF
The water. Experiments with Pawtuxet
showed that TO "A grain 10 the gallon
was all that was necessary TO remove all
matter and yet leave NJ chance for the