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The table shows that the number of B. coli in the crude sewage (24 samples), the effluent
from the 4-foot coke-bed (14 samples), the effluent from the G-foot primary coke-bed (8 samples),
and the effluent from the G-foot secondary coke-bed (2 samples) averaged 600,000, 400,000, 600,000
and 100,000 per c.c. respectively. The percentage reduction in the effluents as compared with the
crude sewage being 33, no reduction, and 83. The average number of B. coli in the 13 samples of
crude sewage corresponding to the 4-foot coke-bed effluent was 538,000; in the 8 samples corresponding
to the 6-foot primary coke-bed effluents 762,000; and in the 2 samples corresponding to
the 6-foot secondary coke-bed effluents the average was 500,000. Based on these figures the
percentage reduction in the number of B. coli was 25 as regards the 4-foot coke-bed effluents,
21 as regards the 6-foot primary coke-bed effluents, and 80 in respect of the 6-foot secondary
coke-bed effluents.
Usually a rise or fall above or below the mean in the number of B. coli in the crude sewage
was associated with a similar increase or decrease in the number in the corresponding effluents.
Thus as regards the crude sewage and 4-foot coke-bed effluents there was in this respect a correspondence
between the two in 10 out of 12 samples; and the raw sewage and 6-foot primary cokebed
effluents showed a similar relation in 6 out of the 7 comparative samples. The records as
regards the 6-foot secondary coke-bed effluents are too few in number to warrant a comparison
being made.
So far as may be judged from a rise or fall above or below the mean the figures show a
certain parallelism between the number of B. coli and the total number of bacteria both in the
crude sewage and in the effluents from the 4-foot and 6-foot primary coke-beds. The records as
regards the 6-foot secondary coke-bed are too few to allow of useful conclusions being drawn.
It is to be noted that the average number of B. coli in the 6-foot primary coke-bed effluent