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A: The problems
of dissolved iron in water not only causes staining to buildings
it comes into contact with, but also promotes the growth of iron
bacteria in ground water bores. While most groundwater contains
some iron, iron bacteria does not affect all bores. When iron bacteria
infects a bore, the resulting growth may be suspended in water or
deposited onto the bore hole equipment. Iron oxide (due to bacteria)
suspended in the bore water is usually exhibited as bio-fouling
in the irrigation pipes. Growth deposits impact on the bore hole
equipment as well as the irrigation plumbing. Iron bacteria causes
iron to be a greater problem than it would otherwise be. Iron and
sulphate reducing bacteria contribute to clogging, corrosion and
bio-fouling of the bore hole. It can contribute to unsightly staining
on buildings, equipment, plants, footpaths and road verges.
Where do bacteria come from?
In many situations bacteria (Micro-organisms) are not native
to the aquifers they are found within. These additional micro-organisms
have in part entered the ground water bores through maintenance
activities and other accidental ways through the top of the bore
hole. It is now more common to find the bacteria already present
in the aquifer before any excavation or drilling is done. In recent
times we have found evidence that deep underground aquifers are
not devoid of bacteria but harbour vast colonies of micro-organisms,
even at great depths.
Bacteria in the ground water .
Bacteria have many ways of getting into the ground water. For
example they can hitch a lift on water or mud going into the bore
hole. Alternately we know from mining rocks that contained no microbes
to begin with, were contaminated with a wide range of potential
colonists when excavation of underground structures took place.
With plenty of time and a pathway bacteria will migrate and set-up
house in any aquifer. In fact so long as they have water, micro-organism
will adapt to almost any environment on Earth. Bacteria have been
found around volcanic vents at temperatures of up to 200oC. They
were also found in the coolant off the Three Mile Island nuclear
reactor, after narrowly escaping melt down in 1979.
Bacterial Iron Build-Up.
What causes bacterial iron build-up? The basic cause is the
presence of the bacteria themselves, dissolved or complex iron,
manganese or sulphur species and an environment suited to survival
and growth of these bacteria. Other factors which may cause iron
to be a greater problem than it might otherwise be include: inappropriate
bore plumbing design or material choice, or construction and poor
choice of water treatment. Flaws in construction may for example
cause extra chemical oxidation or restriction in screens, pipes
and valves. Periods of little or no use allows the fouling growth
to build-up. Overuse can encourage sand or mineral clogging and
extra oxidation. In either event, Iron bacteria exacerbates the
problems.
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