MechChem Africa January-February 2022

Cooling tower water treatment – understanding the options

JP Thyse, technical manager at Allmech, talks about how to protect cooling towers, evaporative condensers and hot and cold water-treatment systems

from scale, corrosion and microbiocides. C ool ing towers requi re water treatment systems to ensure they operate optimally and last for their designed service life. 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. “The key is water treatment optimisation: the ability not only to apply the right chemistries but also to monitor and control water quality constantly and to keep it balanced at all times,” says JP Thyse, technical manager at Allmech. Allmech is a leading South Africanmanu- facturer of boilers and a supplier of water treatment components that offer a range of chemical water treatment programmes designed to target either open circuit or closed circuit cooling systems. “By monitoring pH, water temperature, electrical conductivity, microbiological ac- tivity, corrosion, chemistry levels and other variables, you are able to increase produc- tion, reduce downtime, lower operating and chemical costs and reduce your opera- tion’s impact on the planet,” says Thyse. “To control scale, corrosion, microbiological fouling and foaming, water quality must be maintained at all times, and the correct microbiocides must be applied in the right doses.” He says 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 microbiocides. Allmech offers solutions designed for specific require- ments, across these categories. Scale and corrosion inhibitors “When it comes to scale and corrosion inhibitors for open circuits, we have two products. Allmech CT-200DS is a versatile product as it controls scale and corrosion equally well. It is particularly effective where system control is erratic and where plant operating conditions tend to fluctuate. Awide variety of deposits can be controlled over an extensive pH range,” says 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 Al lmech CT 251, which is designed to control the corrosion of metals in closed water systems and is best for treating pro- cess 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 225 ppm 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,” he says. 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, cop- per alloy corrosion protection and scale inhibition. Microbiocides Thyse says that meeting certain water qual- ity standards requires testing for Legionella bacteria. “SANS 893-1 provides guidelines for the risk management of Legionella bac - teria 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,” he explains. “Experience has shown that cooling tow- ers, evaporative condensers, and hot- and cold-water systems in a wide variety of workplaces present a risk of exposure to Legionella bacteria. Corrosion, scaling, foul- ing and biofouling are all interrelated and, if not treated correctly, can lead to inefficient processes, higher water and energy usage and increased plant maintenance costs.” Al lmech of fers four mi crobioc ide products: • Allmech CT2001 is a broad-spectrum biocide for use in RO, UF and NF sys- tems where bacteria and biofilm are expected to be present. It provides micro-organism 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 ef-

Without water treatment, cooling tower water may be affected by organic growth, fouling, scaling, and corrosion.

32 ¦ MechChem Africa • January-February 2022