History
of the Huddersfield Water Supplies
By T. W. Woodhead
CHAPTER X - TESTING AND INSPECTION OF FITTINGS, PIPES
AND MAINS INCRUSTATION
FRESHWATER BIOLOGICAL RESEARCH
At Wray Castle, Lake Windermere, the research station of
the Freshwater Biological Association of the British Empire,
intensive investigations are in progress relating to these
problems, and the Hon. Director, Professor W.H. Pearsall,
has kindly supplied me with the following brief account
of work in progress relating especially to waters from the
peat-clad moorlands of the Pennines. In this Professor Pearsall
gives evidence of a different origin of "limpets"
in iron pipes, to the usual one given above, and that these
incrustations are not due to the action of water on the
metal. It is often stated that after scraping encusted pipes,
the mains show no sign of deterioration. Prof. Pearsall
writes as follows:-
The problems which affect the users and suppliers of Pennine
waters are very numerous and it may be safe to say that
they are usually connected with the presence of dissolved
peaty materials in the water or with the associated scarcity
of lime. In this, they are to be classed with the waters
of large areas in northern Britain. In the Pennines, however,
three problems seem to be particularly common. In some cases
there are difficulties in filtering the water supply in
summer, owing to the growth of algae either in the reservoirs
or on the filter beds. These difficulties result in excessive
cost or seasonal demands for labour. In other cases the
reservoir waters may become excessively acid, resulting
in such secondary effects as high plumbo-solvent power and
in the necessity for acid-neutralising treatment. Enquiry
into some of these cases has shown that the reservoir "water"
may become really a weak solution of sulphuric acid. A third
and especially common case, is the blocking of the iron
pipes and even valves by the production in them of incrustations
or "limpets." These structures consist mainly
of iron hydroxide and their presence in the pipe system
not only causes low rates of supply of water, but also usually
leads to the water becoming unpleasant in taste and appearance.
It is not generally realized that all these problems and
many more like them are biological and are due to reaction
brought about by living organisms. Thus the dissolved substances
which lead both to the excessive growth of algae and to
the production of sulphuric acid are in both cases products
of the decay of organic matter and both these effects are
due to the special activities of certain groups of moulds
and bacteria in the water. At the same time, their presence
also depend upon the conditions (also due to micro-organisms)
which cause peaty matter to appear in solution in the water.
There is therefore, a very wide field for biological research
on the problems leading to the solution of many waterworks
problems undoubtedly lies in quite unsuspected directions.
A good example of this is the third problem mentioned above,
the incrustation of iron pipes, on which some recent research
has thrown a new light.
The actual cause of the incrustation is a bacterium which
lives upon iron carbonate dissolved in the water, converting
it to ferric hydroxide which is insoluble and which is deposited
on the surface of the bacterial cells and on the walls of
the pipe. An incrustation is thus gradually formed. These
bacteria are, however, very widely distributed and they
occur even where incrustations must be sought in the factors
which cause the presence of iron carbonate in the water,
and which thus permit the growth of the incrusting bacteria.
Until recently, these factors were practically unknown,
but much light has been thrown upon them as a result of
research upon two separate and apparently quite unrelated
problems, namely, the properties of lake muds in relation
to the vegetation growing on them and the conditions controlling
the breakdown of nitrogenous organic matter in mud by moulds
and bacteria leads to the formation of ammonia, which under
certain defined conditions leads to the replacement of iron
from the mud. This iron goes into the solution as iron carbonate
and, under conditions which exist in some lakes and reservoirs,
and not in others, it may remain in solution and get carried
down into the pipe system. Such waters invariably contain
the incrusting bacteria, and hence incrustations in the
pipes will follow. In actual fact every condition which
leads to the formation of these incrustations appears to
be controlled by living organisms and it is possible to
say that the production or otherwise of these incrustations
depends wholly upon the biological condition of the reservoir
and its drainage area. Many other examples might, if space
permitted, be given of this close relationship between waterworks
problems and biological investigation.
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