This post will review the basics of chemical water treatment for cooling towers and other cooling applications. It will also consider how to increase efficiency in cooling towers by using chemical water treatment. For more information on chemical water treatment, visit our Education Center.
Overview
Treating water chemically is a required process in a variety of cooling applications. Cooling applications include comfort and process cooling. Comfort cooling is the air conditioning found in large buildings, hospitals, nursing homes, schools and universities. Process cooling is also found in manufacturing which is used to cool compressors and/or equipment down such as a plastic injection molds.
In these processes, water is treated to maintain specific levels of purity, oxygen, PH, and other factors. Because water has naturally occurring impurities, treatment for corrosive components is critical for use in any cooling application. The reason water is treated for corrosion is to utilize all of the beneficial characteristics of water, while counterbalancing the negative effects of the impurities in the water. Corrosion-causing impurities can lead to early failures of capital equipment and piping, loss of cooling efficiency and negative impacts to asset production.
Impacts of Scale Forming Deposits
Naturally occurring impurities in water may lead to scale or sludge deposits in cooling applications. As pure water is evaporated from cooling and steam boiler systems, impurities remain and become concentrated which increase the potential for scale and sludge deposits. As scale and sludge deposits form, they begin to obstruct heat transfer which leads to higher energy costs, which can lead to loss of equipment operation and early failure. Treating the water helps to control the negative effects it can have on the cooling tower or steam boiler.
Importance of Preventing Legionella in Cooling Towers
Recirculating water in a cooling tower is an excellent environment for biological growth such as algae, bacteria, slime, and water-borne pathogens such as Legionella. These are micro-organisms in the cooling system. These bacteria usually form a biofilm on the surfaces that have contact with the circulating water. The biofilm can act as a thermos insulator which can also decrease heat transfer efficiencies.
If water-borne pathogens are present in the water, such as Legionella, this can cause serious health and safety problems for operators. Legionella can travel in droplets during normal use of a cooling tower. When caught into an airstream, these droplets can travel in the wind, becoming a source of severely infectious disease.
Improving Efficiency: Cooling Tower Blowdown & Cycling
Using chemical water treatment solutions is important for public safety and directly results in a variety of measurable benefits to operators. Functionally, cooling towers extract heat from a stream of water by releasing it to the atmosphere through evaporation. This is done either by direct contact with the air as it flows over a fill or by heat transfer through recirculation coils. As previously mentioned, suspended solids in the water can cause corrosion, mineral scaling, and bacterial growth, which causes damage to the equipment. Chemicals are introduced to the system to control these problems. This also allows for the same cycle of water to be useful for longer periods of time, which saves costs for the operator.
Even with a well calibrated chemical water treatment plan, cycles of concentration (COC) will eventually outpace the effects of the chemicals. Blowdown, or periodic release of some of the system water to be replenished by freshwater, is required to manage the rate at which the issues occur. Allowing scale to accumulate not only reduces the flow through a pipe or chamber for some applications, but also decreases any thermal transfer through the metal that is supposed to occur. Any increase in scale buildup or excessive particle presence in the water means cooling becomes far less efficient. This leads to a need for more blowdown and fewer cycles of use before water needs to be replenished.
Chemical Water Treatment Plan Optimization
Typically, when a chemical water treatment plan is newly optimized, operators will see improvements quickly. COC will increase, and this increase in cycling will result in lower water costs. As an optimized chemical plan clears existing buildup, units will begin to perform optimally and cooling will be achieved more efficiently. These benefits will save operational expenses and improve asset performance.
Conversely, if left untreated or under-treated, continual build-up will result in equipment failure. This will not only be costly, but also poses a direct safety hazard to workers. Bicarbonates are generally the culprits in scale formation, and chemicals must be applied to inhibit scale and corrosion by forming a metal oxide film on the surfaces. Bacteria, algae, mold, and fungi can also contaminate a cooling tower system’s warm, moist environment, and require the use of biocides, such as chlorine compounds, before the organisms form colonies on surfaces. Microbes can form a slime that allows sediment to stick to it, as well as producing acids that can damage metal.
There are multiple ways to apply chemical to a cooling application. Historically, chemical was often delivered to a treatment room pre-mixed in large 55 gallon drums. However, this created great risk of chemical exposure to technicians, high logistics costs in transporting full drums, required excessive floor space for storage, and necessitates drum cleaning and careful removal when chemicals need restocking.
Today, water treatment is now more safe and efficient thanks to ultra concentrated liquid chemical water treatment options. Similarly to the revolution that the laundry detergent industry faced, ultra concentrated options allow for smaller containers, less water wasted in pre-mixing, and more efficient use of chemical.
To learn more about the benefits of ultra concentrated liquid water treatment, see the About page.