Getting Technical
CHARLES NICOLSON
Charles Nicolson has a physics and chemistry degree from Natal University which he subsequently put to
good use by applying speciality chemicals in mining and industrial processes where water is a major factor.
This created an enduring interest in water technology, a passion that expanded to the HVAC industry
in 1984 when he joined BHT Water Treatment. Since then, water technology in HVAC water circuits has
continued to be an abiding interest.
MY TAKE ON COOLING WATER TREATMENT
OVER THE PAST FIFTY YEARS
By Charles Nicolson
Water treatment programmes, particularly for cooling water circuits, have
now reached a stage of development where it is unlikely that further
significant advances will occur from a purely technical point of view
unless new technology is introduced and applied.
R
efinements introduced into current cooling water
treatment are almost entirely focused on minimising
costs while ensuring that the qualities of both circulating
and bleed-off water remain compliant with the ever-
increasing numbers and complexity of toxicity and
environmental regulations.
Going back fifty years to 1970, cooling water treatment
was simple. Supply water to cooling circuits was softened
to eliminate any scaling potential and small concentrations
of soluble chromate chemicals were dosed which not only
prevented corrosion by ‘chrome plating’ wetted surfaces
but were also highly effective broad-spectrum biocides. This
straightforward and easy treatment covered not only closed
water circuits but also the whole diverse range of applications
of closed and evaporative cooling water circuits found in HVAC
installations as well as other water-based machinery such as
humidifiers and misting/fogging systems.
If there were restrictions on availability of municipal or potable
quality water from a local authority which was sometimes the
case, then water sources were usually boreholes or other types
of underground aquifers. Regardless of the sources, however,
little thought was generally given to ensuring that supply water
pressure at points of entry into evaporative cooling units and
other equipment such as backwash facilities for filters was
enough. Cooling towers and other equipment needing supply
water were often located on top of office and other commercial
buildings along with concrete or ‘Braithwaite type’ galvanised
steel water holding tanks fed by municipal or alternative supply
water. These relatively large holding tanks ensured that enough
water was always available in the event of disruptions in normal
supply lasting for several hours or even for a few days at a time.
The tanks also distributed fresh water for drinking, domestic
toiletry, sewage and cleaning purposes. More often than not,
water for these purposes distributed by the tanks flowed purely by
LABELS
The general layout of a rooftop system as described.
www.hvacronline.co.za
W: Supply water holding tank
T: Top up water tank for closed chilled water system
CT: Cooling tower
B1: Initial location of bleed-off valve
C1: Chiller No 1
C2: Chiller No 2
CWS: Chilled water system
x: Items added to improve water treatment
X: Automatic supply water pressure booster station
WM: Water meter with pulse output facility
B2: nstallation of conductivity-controlled bleed-off system
RACA Journal I April 2020
55