A considerable dose of chlorine was present in a sample taken from the bottom. This was the more remarkable as the pipe discharged the well-water at the top of the tank. The denser saline water sank to the bottom, without mixing appreciably with the lighter rain-water. I see no reason, therefore, to anticipate any inconvenience from salt, especially as the water will always be drawn for use from the upper strata by means of suitably arranged valves at different levels.
It is just possible that marine organisms living in the sand may be killed by the fresh water and contaminate it. Such a case occurred in the case of a filter-bed (not a reservoir) in Grenada. The sand for this was coral sand taken from the shore near to low water mark. Apparently it was clean, but it must have contained living coral insects. These were killed by the fresh water and imparted to the filtrate a most offensive taste and smell. The sand was removed and replaced by other coral sand collected from above high-water mark, when the inconvenience ceased.
The conditions in this case were quite different from those which will obtain in the present instance. The water actually passed through the sand, carrying with it the offensive products of decomposition. Here, again, drawing from near the surface will prevent any inconvenience.
It was often found in Malta that the lower strata of water in the house-tanks showed unmistakable signs of sewage-contamination (free and albumenoid ammonia), while surface water was perfectly good. In such cases, however, there was actual infiltration of sewage from some leaky house-sewer. This was so often the case that the use of pumps, though prescribed by law, was abandoned, as they drew
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considerable dose of chlorine was present in a sample taken
from the bottom. This was the more remarkable as the pipe
discharged the well-water at the top of the tank. The
denser saline water sank to the bottom, without mixing, ap-
preciably, with the lighter rain-water. I see no reason
therefore, to anticipate any inconvenience from salt, e8-
pecially as the water will always be drawn for use, from the
upper strata, by means of suitably arranged valves at dif-
ferent levels.
it.
It is just possible that marine organisms living
in the sand may be killed by the fresh water; and contaminate
Such a case occurred in the case of a filter-bed, (not
a reservoir) in Grenada. The sand for this was coral sand
taken from the shore near to low water mark. Apparently it
was clean, but it must have contained living coral insects.
These were killed by the fresh water; and imparted to the
filtrate, a most offensive taste and smell. The sand was re-
moved and replaced by other coral sand, collected from above
high-water mark, when the inconvenience cessed.
The conditiona in this case were quite different
to those which will obtain in the present instance. The
water actually passed through the sand, carrying with it
the offensive products of decomposition.
Here, again, drawing from near the surface will
prevent any inconvenience.
It was often found in Malts that the lower strata
of water in the house-tanks shewed unmistakable signs of
sewage-contamination, (free and albumenoid ammonia); whilst surface water was perfectly good. In such cases, however, there was actual infiltration of sewage, from some leaky house-sever .
This was so often the case, that the use of
pumps, though prescribed by law, was abandoned, as they drew
2
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