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Cooling tower water treatment – understanding the options

Home Engineering HVAC Cooling tower water treatment – understanding the options

WITHOUT water treatment, cooling tower water may be affected by organic growth, fouling, scaling, and corrosion. This can reduce plant productivity, cause downtime, and increase maintenance and repair costs significantly.

That’s according to P Thyse, Technical Manager at Allmech, who said, “The key is water treatment optimisation: the ability to not only apply the right chemistries but also to constantly monitor and control water quality and to keep it balanced at all times”.

Allmech is a South African manufacturer of boilers and supplier of water treatment components that offers a range of chemical water treatment programmes designed to specifically target either open circuit or close circuit cooling systems.

“By monitoring pH, water temperature, electrical conductivity, microbiological activity, corrosion, chemistry levels and other variables you are able to, increase production, reduce downtime, lower operating and chemical costs and reduce your operation’s impact on the planet,” said Thyse.

“To control scale, corrosion, microbiological fouling, and foaming. Water quality must be maintained at all times, and the right microbicides must be applied in the right doses.”

He said water treatment products can generally be divided into three groups: scale and corrosion inhibitors for open circuits, scale and corrosion inhibitors for closed circuits, and micro biocides. Allmech offers solutions across these categories, designed for specific requirements.

“When it comes to scale and corrosion inhibitors for open circuits, we have two products. Allmech CT-200DS is a very versatile product as it controls scale and corrosion equally well. It is particularly effective where system control is erratic and when plant operating conditions tend to fluctuate. A wide variety of deposits can be controlled over an extensive pH range,” said Thyse.

“Allmech CT 202 is a specially formulated solution designed to reduce corrosion and scale formation in cooling and boiler water systems. It is also useful in other systems where calcium carbonate scale and mild steel corrosion need to be prevented.”

For closed circuits, he recommends Allmech CT 251, which is designed to control the corrosion of metals in closed water systems and is best for treating process cooling, hot water and chilled water systems, as well as glycol water systems.

“It contains steel and copper corrosion inhibitors to provide multi-metal corrosion control, plus pH buffering to minimise the effects of acidic conditions from ethylene glycol breakdown or acidic process leaks. Hardness salts are controlled to a maximum level of 225ppm by means of a formulated dispersant and antiscalants. It can be used with ethylene glycol in winterised systems, thereby eliminating the incompatibility problems of chromates.”

Another option is Allmech A104, a liquid corrosion inhibitor programme designed for medium- to high-heat flux systems. It is a multi-component inhibitor that provides ferrous metal corrosion protection, copper alloy corrosion protection and scale inhibition.

Micro biocides

Thyse said that meeting certain water quality standards requires testing for Legionella bacteria. “SANS 893‐1 provides guidelines for the risk management of Legionella bacteria in any undertaking, while SANS 893‐2 focuses on requirements for designing and managing hot- and cold-water systems that could create and transmit water droplets (and thus Legionella bacteria).

“Experience has shown us that cooling towers, evaporative condensers, hot- and cold-water systems in a wide variety of workplaces present a risk of exposure to Legionella bacteria. Corrosion, scaling, fouling and biofouling are all inter-related and if not treated correctly can lead to inefficient processes, higher water and energy usage and increased plant maintenance costs.”

Allmech offers four micro biocide products:
• Allmech CT2001 is a broad-spectrum biocide for use in RO, UF and NF systems where bacteria and biofilm are expected to be present. It provides microorganism control (including Legionella) and clean systems. It can be used alone or with other biocides on a rotation basis.
• Allmech CT–2007 is a broad-spectrum algaecide and biocide especially effective for the control of algae and slime in industrial water systems, air evaporative condensers and air conditioning units.
• Allmech CT-2008 is a broad-spectrum biocide for closed circuits.
• Allmech CT-SBL is a low-cost algaecide and biocide when combined with CT-HPW.
• Allmech CT-HPW is a low-cost algaecide and biocide when combined with CT-SBL.

Thyse said businesses with cooling towers should also consider additional water filtration to remove suspended solids, organics, and silt particles in their cooling systems. “Reducing fouling and biological growth in the cooling systems helps to control other issues in the system, such as scaling and corrosion.”

Side stream filtration is an effective tool for the control of deposition and fouling in a cooling water system, he added.

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