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This paper represents an alternative non-chemical means of
managing the aquatic environment of cooling towers, in a way that appears to
preclude the proliferation of bacteriological contaminants.
A water conditioner was sized to the cooling tower circulation
rate and reservoir capacity, and installed as a by-pass circuit
that would
circulate the cooling tower water through the conditioner for 12 hours every
day.
Prior to commencement of the experiment, a number of parameters
were decided which are as follows:
(a) an adjacent cooling tower
which did not have a water conditioner fitted, would be subject to the same
schedule of tests as the cooling tower which did have the water conditioner
device fitted.
(b) both cooling towers would
be thoroughly cleaned.
(c) one cooling tower would
continue to use biocide and algaecide chemicals and the cooling tower which had
the water conditioner
device fitted would not use any chemicals.
(d) a program of tests and
inspections was scheduled.
(e) TBC dip slide tests were
taken and recorded.
The test schedules were:
Total Bacteria Count, Legionella Count, Total Dissolved Solids,
Alkalinity, and pH.
What was of major significance, and is possibly the most
important point of this paper, is that during the two year experiment, no
algaecide or biocide chemicals were used in the cooling tower with the water
conditioner device fitted.
Throughout this time, the test results as provided by a NATA
certified testing agency have identified the lowest detectable levels of all
legionellas which is <10 CFU/ml, and the TBC has consistently remained at
less than 10³.
This is an excellent result for cooling towers which are using
chemicals, but is an exceptional result from cooling towers which are using
no biocide or algaecide chemicals.
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(a) The device appears to be
able to consistently maintain a TBC of below 1 x 10³ CFU/ml and a Legionella
bacteria count of <10 CFU/ml.
(b) The cooling tower is
visually clean.
(c) The condenser tubes on the
water side of the refrigeration unit condenser allied to this cooling tower,
were not cleaned at the commencement of the experiment. However when the
condenser end covers were removed for their seasonal inspections and tube
cleaning, every tube was observed to be completely clean and shining like
a gun barrel.
What benefits has the project identified
thus far?
(a) The cooling tower is
dispersing neither Legionella or biocide aerosols.
(b) The cooling tower no
longer requires cleaning except for the requirement to desludge the water
pan.
(c) The shell and tube
condensers attached to the refrigeration machinery no longer require cleaning or
brushing.
(d) An additional benefit of
item (b) is that the compressor efficiency is
not impaired or reduced because of dirty or scaled condenser tubes.
(e) The use of cooling tower
chemicals has been eliminated subject to the Total Bacterial and Legionella
counts remaining below a specified limit.
The two year field test experiment had thus far substantiated
that the aquatic environment of a cooling tower and an evaporative
cooler
can be controlled using what has traditionally been known as a proprietary
device.
The evidence supporting this is the visual results of the
experiment and the certified NATA laboratory test results of the water
samples. |