View report page

It will be seen that the sewage arrived at the works containing an average amount of
0.1602 grains per gallon of nitric nitrogen, which shows that it was fairly fresh. It contained, as
a rule, no nitrous nitrogen.
Comparing the amounts of oxidation of nitrogen produced in the various bed, the amount of nitrous
oxidation effected in the primary beds was reduced by 17.7 per cent. in the secondary coarse bed
and by 36.6 per cent. in the secondary fine bed. On the other hand the amount of nitric oxidation
effected in the primary beds was increased by 107.4 per cent, in the secondary coarse bed and by
345.3 per cent. in the secondary fine bed.
3.—THE BACTERIAL TREATMENT OF THE SEDIMENTED CHEMICAL
EFFLUENT IN THE ONE ACRE SIX-FEET COKE-BED.
The one-acre coke-bed, as it was originally laid down, consisted of three feet of unsifted
pan breeze obtained from the adjacent Beckton Gas Works. In 1898 the depth was increased
to 6 feet by placing on the top of the old bed 3 feet of coke, in pieces from half-an-inch to one inch
in diameter and sifted free from dust. Its area was really 5,067 square yards instead of 4,840 square
yards.
The bed was first filled on 29th April, 1898, in order to test the pipes for leakage, and it
was observed that the surface of the bed settled down considerably in the central portion. The
bed was re-levelled and work was re-commenced on the 12th May, 1898. On the following day
the effluent from the bed showed a purification of 81'2 per cent. as compared with the chemical
effluent, which was allowed to flow upon this bed. The bed was filled once a day until 2nd July,
1898, from after that date one filling per tide was dealt with: this amounted practically to two
fillings a day. The bed had to be worked according to the tide, because high-water mark in the
river, into which the effluent was discharged, was above the level of the outfall for the effluent.
Quantities of chemical effluent dealt with and capacity of the bed.
The bed was filled once a day between 12th May, 1898, and 2nd July, 1898, with the
exception of Sundays, when the bed rested empty. During this period the bed was filled 43 times,
and dealt with a total volume of 29,986,048 gallons, or an average of 697,350 gallons at each
filling. As the total capacity of the space occupied by the bed is 273,618 cubic feet, or 1,710,112
gallons, the bed showed a liquid capacity of 40.8 per cent. of its whole volume. During the
period under notice the capacity of the bed, as calculated from the averages of the first and last
complete week's work, fell 71,045 gallons, this being equal to a decrease of 4.15 per cent. during the
the whole period, or to 0.59 per cent. per week.
During the week ending July 9th, 1898, the bed was dealing with sewage at the rate of
1,255,918 gallons a clay for six days in the week, and resting on the seventh. This quantity is
approximately equal to that dealt with by the old 3-foot bed when it was at its maximum working
capacity and being filled three times a day.
As the effluent appeared to drain off very slowly from the bed, the engineer obtained the
sanction of the Committee to construct a second outlet in order to hasten the process of emptying
this bed. For this purpose the bed was thrown out of work on Friday, 29th July. 1898. The
capacity of the bed at this time was 508,250 gallons, or 29.7 per cent. This is a fall of 12.2 per cent.
from the average capacity during the week ending May 21st, 1898. The average capacity during
this week was 717,503 gallons, and the last filling on the 29th July had shown 508,250 gallons.
The purification effected during the period from May 12th to 29th July, 1898, as shown by
the oxygen consumed, averaged 79.7 per cent.
The regular filling of the bed was commenced again on 8th November, 1898. During the
first two weeks after starting, the bed was filled once a day, but the work done was so efficient that
tidal fillings were resumed on 21st November, and continued until 11th March, 1899, when the
bed became foul and was thrown out of work. During this period (November 8th, 1898, to March
11th. 1899) the bed dealt with 98,743,447 gallons and effected an average purification of 84'3
per cent.
At the commencement of this period the capacity of the bed was 39.7 per cent.; at the end
of the period it was 29.1 per cent. This is equal to a drop of 10.6 per cent. in seventeen weeks, or
06 per cent. per week.
The bed rested empty for eight weeks and was started again on 8th May, 1899. It was
filled once a day during the first three days of this week, and rested empty until the Monday
following in order to enable the engineer to carry out some experiments relative to the cost of