View report page

11
The decrease in the capacity of the beds was as follows—
Periods of working each bed.
Total loss
in capacity
in gallons.
Decrease in capacity per week
Stated in
gallons.
Stated in percentage
of original
capacity.
Coarse bed A (primary) —
September 20 to October 27, 1899 (5 weeks)
84
16.8
1.92
October 27 to December 6, 1899 (6 weeks)
20
3.3
0.17
December 6 to January 4, 1900 (4 weeks)
44
11.0
1.12
January 4 to February 7, 1900 (5 weeks)
48
9.6
1.00
Average loss per week*
9.8
1.00
Coarse bed B (primary)—
September 20 to October 27, 1899
5
1.0
0.12
October 27 to December 6, 1899
49
8.2
0.85
December 6 to January 4, 1900
38
9.5
0.72
January 4 to February 7, 1900
33
6.6
0.70
Average loss per week*
6.3
0.60
Coarse bed A 1 (secondary) —
September 20 to October 27, 1899
18
3.6
0.38
October 27 to December 6, 1899
19
3.2
0.30
December 6 to January 4, 1900
24
6.0
0.62
January 4 to February 7, 1900
nil
nil
nil
Average loss per week*
3.2
0.31
Fine bed B 1 (secondary)—
September 20 to October 27, 1899
12
2.4
0.24
October 27 to December 6, 1899
12
(Increase in
capacity)
20
(Increase)
0.20
(Increase)
December 6 to January 4, 1900
11
2.7
0.27
January 4 to February 7, 1900
26
5.2
0.52
Average loss per week*
1.9
0.19
Although the apparent average loss of capacity was much greater in coarse bed A than in coarse
bed B (both primary), the actual capacity of B was slightly smaller than that of A, being 21 2 per cent.,
as against 21.8 per cent. in A. This is accounted for by the fact that a much greater decrease in
capacity occurred in bed B before the 20th September than in bed A after the 20th September.
Work was commenced on Tuesday, 4th July, 1899, the beds receiving one filling per day
up to 15th July, when it was thought advisable to fill the beds only three times in the week.
From 21st September the beds received one filling a day, and from 11th December onward
two fillings a day.
The purification as measured by the amount of oxygen absorbed from permanganate,
effected up to the end of the year 1899 is stated in the following table, in which the numbers in
the first column represent the average percentage purification effected during the period when +he
beds were filled three times a week, the second column the period of one filling a day, the third
column the period of two fillings a day, and the last column the average percentage purification
effected by each bed from the commencement of the experiment until 31st December, 1899.
Description of bed.
Three fillings
a week.
Six fillings
a week.
Twelve fillings
a week.
Average.
Primary coarse bed A 43.9 45.3 45.0 43.9
Secondary coarse bed A 1 62.3 63.6 61.1 62.5
Primary coarse bed B 43.5 45.3 43.9 43.8
Secondary fine bed B 1 79.l 76.1 67.6 76.2
A further improvement is observable in the efficiency of the beds since December 31st
last up to the date of writing (10th February, 1900), the average percentage purification effected
during that period having been as follows—
Primary coarse bed A 46.4
Secondary coarse bed A 1 64.2
Primary coarse bed B 47.3
Secondary fine bed B 1 71.0
* This average is calculated from the total loss of capacity which took place during the 20 weeks of experiment.