Evening journal., 1898-09-13
WILMINGTON'S FILTER.
[cOntlnued From First Page.l

and when the corners OF the latter were
down the increase in power required to
turn them gave a jerky motion and
caused the boxes to break. The rods
are suspended in a chain belt. They
are Of common iron, about q inches IN
diameter, and there are about 800
pounds of iron in each bundle, or III
short tons in each bed The bundles
Of rods make about revolutions per
minute. The attrition of the rods as
they revolve on each other was design
ed to cause particles of iron to be de-
posted in the water 10 serve as a
coagulant. The Water Department has
no records of the amount Of iron con-
sumed in the process, but Mr.. Bond
states the reds have not been renewed
rcr two years or so. Had the rods
been entirely consumed in two years
| iron would have been used at the rate
Of about OOPS grains per gallon Of
water. In the Anderson process OF
iron treatment OIL and or grains per
gallon are taken up by the water, ac-
cording to the printed matter issued by
the company controlling that process.
She lower Of these two rates, or Oh
grain per gallon, would require 1913
pounds of iron per 1000, 900 gallons of
water filtered, or $1,000 pounds OF iron
for the past two years, against the TO-
900 pounds put in place two years ago,
and still but little wasted. The rub
bling of the rods together as they re-
volve seems to do little more than keep
them somewhat polished, Judging from
the looks Of the outer rods. The scrap
iron, while in use, showed more wear
than the rods, as would he expected.
When the plant is working at its full
capacity Of 100000 gallons in "a
hours, or 100000 gallons per bed the
lime taken for the water to travel from
he last bundle Of rods to the sedimen-
alton chamber is stated to be about
3la minutes, and through the whole
plant about an hour.
The air for aeration was furnished
by a Clayton air compressor with an
1Sx24-inch air end until about two
years ago, when No. Wilbraham-
Baker blower was substituted The
blower is run by the water wheel that
drives the power pumps, thus Iaving
power, besides which the air is always
available now, whereas the compressor
had to step as soon as the steam plant
shut down.
The volume Of air supplied is said to
be about equal to the volume Of water
reated. doubtless meaning air at at
? mospheric pressure.
Originally, one whole filter bed was
washed during each twelve yours, ex-
cept that no washing was done for the
last half Saturday and all Of Sunday.
A little calculation will show that un-
der this plan the periods between
washing each bed would be alternately
r 21s and 4 days. In 1896 each bed was
divided into halves by plank partl-
ions, SO that only one-tenth instead
of one-fifth of the plant need be thrown
] out Of use for washing. In addition,
washing is done each day now, with a
. long wash" on Sunday. The altering
material was also removed and washed
= in 1886, one bed at a time, the grave.
, and sand" to quote from the report OF
! that year, were again separated into
= their various sizes and replaced, thelI
! comparative depths (being) changed
from II inches of gravel and 10 inches
Of sand to 70 inches of gravel and Ii
inches of sand" This is the only timf
= the filtering material has been taken
ut. washed and screened, Mr.. Bond
$ states, but reference is made further on
a to clogging Of the beds in 1894 OF
/, 1895, which nscessitated the remova.
I Of the material.
n The original intention seems to have
been to cleanse the f,tering materia
with water admitted from above under
e head Of / foot, alternated with air ad-
ullLllu ulutI pressure AAeAA hNA~eAt-As a.
- the latter case the water would still
e be passing upward through the bed, az
d when in use hut the water would bi
y wasted. Mr. Bond stated that the al
!. disturbed the bed by pushing the ma
erial upwards and the water carried
the fine material downward. Subse
j. uuent.y perforated pipes we're paced II
u the filter beds. To wash the gravel th'
N beds are now left submerged and waite
n is wasted from below, while TO wasl
t. the sand the sedimentation tanks ar
= left filed with water and waste weir
e are opened above the beds, so that th
Of air or water. as the case may be, i
/ forced upwards through the sand.
- While Uttered water has always bse-
t used for washing, as we understand il
water under pressure has been used 70
only about ~ years, so that previou
A. TO this change the amount OF was
ne water was unknown.
n .oo- - ,..,.,,,,t 90 F1fcr-rd rraf