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Addressing the problem of biological growth, de Jager advocates for the use of biocides over chlorine or chlorine derivatives.
but also provides valuable insights into water consumption patterns. A sudden increase in water usage can signal problems such as a malfunctioning ball valve causing overflow leading to wasted water, increased chemical consumption, and a drop in conductivity within the cooling tower. In such cases, the water in the tower might even have the same conductivity as the tap water, indicating a continuous loss and replacement.
Chemical consumption is calculated based on evaporation rates, which fluctuate seasonally. The service reports provided to customers detail chemical usage and other relevant parameters, allowing for transparency and early detection of potential issues.
DIVERSE APPLICATIONS AND THE IMPORTANCE OF QUALITY MAKE-UP WATER METERS
De Jager extends the discussion beyond cooling towers to highlight other industrial applications where precise dosing and chemical management are crucial. De Jager illustrates the adaptability of their dosing systems in industries such as fruit packing and processing. Here, similar principles of probe-based chemical level monitoring and automated dosing pumps are employed to ensure the wash water meets stringent quality standards, particularly for export purposes. He showcases custom-built control panels, often featuring digital pumps and protective windows to allow monitoring without compromising the enclosed environment.
Another application highlighted was pH control in agricultural settings, specifically for water used in cooling towers. De Jager describes instances where the raw water source, such as borehole water, has a problematic pH that needs adjustment to optimise the effectiveness of the water treatment chemicals. He also touches upon the challenges associated with using borehole water in general. When borehole water, often containing higher levels of iron, is exposed to air in open dams, the iron oxidises and precipitates out, potentially causing fouling and other issues in the downstream systems.
Returning to cooling systems, de Jager points out variations in dosing system configurations based on specific needs. For systems with multiple towers sharing common lines and isolation valves, they implement dosing on the common line
A key challenge in implementing effective water treatment in closed-loop systems is accurately determining the system volume.
to ensure continuous chemical treatment regardless of which tower is operational. He presents an example of a control panel with two diaphragm pumps, catering to such scenarios, sometimes alongside a peristaltic pump for specific dosing requirements. The discussion then turns to the connectivity controller in more detail. De Jager emphasises the added benefit of these controllers displaying the water temperature, providing an immediate indication of potential system anomalies. Furthermore, he explains the integration capabilities with BMS systems via a 4-20 milliamp signal, allowing for remote monitoring of conductivity levels. The controllers also feature dual relay outputs. The primary output typically controls the bleed-down valve, while the secondary output can be programmed to trigger alarms( visual or within the BMS) if the conductivity deviates from the set parameters, either going too high or, unexpectedly, too low. This low conductivity alarm can indicate issues like excessive bleed-off or a significant influx of dilution water.
Addressing a question about the pink colourant, phenolphthalein, de Jager confirms its use in closed-loop systems as a visual indicator of both pH and potential leaks. He also clarifies that while some nitrite-based products are pre-coloured pink, Procontrol uses a powdered nitrite and adds the colourant separately. This choice is primarily logistical, as a single 25kg bag of their powder is equivalent to multiple bulky liquid containers.
De Jager stresses that the continuous evaporation in cooling towers leads to a concentration of dissolved salts and minerals. Even with relatively clean makeup water( e. g. 80 μS in Cape Town), the conductivity can escalate significantly over time. He recounts instances where conductivity levels were so high that the water exhibited a slight yellowish tinge, a clear indicator of severe scaling potential. In such cases, diluting the sample is necessary to even measure the conductivity.
Responding to a question about alternative biocides like chlorine dioxide, de Jager firmly advises against their use in cooling towers. He emphasises that chiller manufacturers would likely void warranties if chloride levels are elevated. Chlorine, being a potent oxidiser, is corrosive to the metallic components of cooling systems, leading to paint degradation and eventual rusting.
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