The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1885-1921, 1900-02-28

FILTRATION of large quantities of wa
ter-mlllions of gallons--is a much
simpler process than most persons
imagine, nor is it attended with such
vast expenditure as some people would
nave us believe. 1t has been comput-
cd that 1t costs at Hamburg about S5
per million gallons of water filtered,
though this figure includes repairs to
pump and machinery, somewhat reduc-
Ing the cost OF actual filtration.
A typical English filtering plant is
to be seen at the works of the East
London Waterworks Company, at WAL
| thamstow, Eng and.
There are thirty-one filter beds at
the Walthamstow works, each bed be-
ing about one acre in extent. When q
I.site for a filter bed has been selected
| excavations covering about an acre in
extent are made, embankments of clay
concrete or masonry being raised to a
hight of about seven feet. The bottom
| of the bed is prepared with two
courses of brick, laid dry, the neither
most bricks being laid end to end in
lines at right angles to a large Gu vert
placed under the bed. The bricks form
a apeeies OF network, allowing the wa
ter to drip into the culvert. On top Of
these bricks layer of coarse gravel
nine inches in thickness is then placed.
this being Surmounted by nine inches
of fine gravel. Coarse sand to a depth
of one foot Is placed on the fine gravel,
and above all this, 36 inches of fine
sand is carefully laid down. and
smoothed over with boards by pro-
cess called '9ooting."
| The bed is now ready for filtration
L Fn hO fa,.o !.
into the bed until depth of three and
one-haIf or four feet has been reached
Gradually the water drips through the
layers of gravel and sand, falling into
| q gravity cuivert, which conveys 1t to
a pure water reservoir, about twenty
| feet in diameter, whence it is pu1nued
by powerful engines and sent out over
the delivery district.
Each acre filters about 100000 gall
Ions Of water per day, or four vertical
inches per hour. The German Health
Board limits the filtration of each bed
to four inches per hour, or eight feet
per day, in order that all water shall
be properly filtered, bed not being al
lowed to do more than a certain
amount of work in a given time.
In few weeks the bottoms of the
filter beds become covered with various
/ deposits, such as mud, vegetable
| growths and slime. 1t is then neces-
sary to wash the filtering sand. The
bed is drained, about one-half inch of
sand being carefully scraped off the
surface of the bed, and conveyed by
means of wheelbarrows to mechani-
cal churning device, which washes 1t
free from impurities. At some works
the washing is done by hand, but the
mechanical process is considered more
efficient. 1t costs to clean filter in
London about S114 per million gal
Ions of water filtered; i. e., every time
a million gallons of dirty water pass
/ through the filter it leaves $1.14 worth
| of work to be done by way OF cleaning.
| The cost of each acre of London filter
| ing bed ranges from $4,000 to $4,000,
according to the value and nature of
/ the ground. All the London filter
beds are open, or uncovered, as the cli-
mate is too mild to cause much forma-
| tiOn of ice on the bed in winter.
Where water is likely to freeze the
f1lter-beds have to. be covered. FreeZ-
ing of flter-bed stops the process OF
filtration and prevents the bed from
being c-eaned. Covered filter beds
cost, naturally, great deal more than
open ones. The covered beds of Eur
ich cost SOS, 1000 per acre; Berlin, $780,
600 per acre. There are two filter
beds at Poughkeepsie, n. Y, costing
$112,641 per acre. The East London
Works supply 51,495,O 900 gallons of I'd
ter daily, which is filtered, with the
exception of about 10000 gallons COM
ing from springs 200 feet below the
surface.
The total daily supply of the eight
London water companies is 226,145,000
gallons Of water, every drop of which
is fl tered. Statistics prove that Lon
don is one of the healthiest cities in
the world, and scientists and physi-
clans account for this by the fact that
rigorous measures are taken to assure
the filtration of all the drinking water
supplied to its inhabitants.
An Imperial edict has been issued at
Pekin offering reward of 100 900 taels
for the capture of Kang Yu Wei and