For companies using cooling towers to remove heat from an industrial process or for cooling large buildings, there are several issues that can surface during the cooling tower water treatment process that we see on a regular basis. Because these issues occur often, it’s important to know what to look out for in advance, perhaps saving you some time and resources down the line.
Keep in mind that these issues will vary depending on whether your cooling tower is an open recirculating system, once-through, or closed recirculating. We’ve broken out some of the most common problems with cooling tower water treatment and how to solve them below:
High amount of blowdown
Since cooling towers remove heat by the process of evaporation, it’s no surprise that they, in turn, can use lots of water to make up the difference. Depending on the quality of makeup water being added to the cooling tower and the operation efficiency of the unit, large amounts of solids can remain after evaporation occurs, causing an increased need to “blow down” or remove solid waste and dissolved solids buildup from the circulation water before it has a chance to scale or corrode equipment.
When blowdown occurs, circulation water and treatment chemicals are also lost along with the solid waste, so it’s important to monitor this closely. If your cooling tower requires too much blowdown, it could be an indication that the water treatment system isn’t running as efficiently as it could be or feeding the cooling tower water pure enough for the process. An effective cooling tower water treatment system will provide the right quality of water to your cooling tower, the correct circulation chemistry , allowing it to run efficiently, avoiding problematic deposition, and maintaining a manageable amount of blowdown. This, in turn, helps conserve the amount of any makeup water or chemicals needed and results in a higher-solid waste.
If you require higher-than-normal amount of blowdown, consult your cooling tower water treatment expert. Depending on what’s causing the issue, some solutions to decreasing the amount of cooling tower blowdown might include:
- Improved feed water filtration
- Higher-quality side-stream filtration
- Increased cycle of concentration (depending on quality of makeup and circulation water—not always the right solution)
- Maintaining better makeup water chemistry by removing scale forming and corrosion causing impurities.
- Change or closely manage the cooling tower feed chemistry program.
Low cycle of concentration
In cooling towers, cycle of concentration is a ratio that measures how concentrated solids are in the cooling tower process water compared to the makeup water by measuring conductivity in the blowdown. A facility should see at least three to three to six cycles of concentration (which is three to six times the concentration of solids in the circulation water than the original makeup water). Over five is ideal. The higher your cycle of concentration, the lower your need for makeup water and blowdown, thus saving water, chemicals, and cost.
For systems operating at a low cycle of concentration, water consumption and chemical usage can greatly increase, causing excess costs to add up. Some cooling tower operators will run their cooling tower at a low cycle of concentration intentionally (for example, if the cooling water is used for ash disposal), but most aim for a higher cycle of concentration.
As the case with many water treatment solutions, it’s best to consult your cooling tower water treatment specialist, as the quality of the source water, chemistry of the makeup water, and type of cooling tower being used will dictate what treatments are necessary to achieve the best cycle of concentration for your facility. In general, however, some solutions to increasing your cycles of concentration can include:
- Better cooling tower control by Minimizing blowdown monitoring conductivity
- pH/alkalinity control to minimize scale formation
- decreasing feed hardness, iron, and silica
- manage microbial growth
Not accounting for treatment of secondary waste
Any discharge that your system creates needs to meet all local regulatory requirements. Contaminants from the feed water impact the volume and processing requirements in secondary waste. Also, sometimes these secondary wastes need to be treated and discharged, yet many times they are discharged to a publicly owned treatment works or wastewater facility and they must meet the requirements of that facility.
It’s best to get a copy of the permit requirements, carefully analyze them, and design your secondary treatment processes and blowdown handling to meet the effluent discharge accordingly. Sometimes this includes releasing to the environment under a SPEDES permit. These permissions need to be negotiated in advance to be sure that the plant will achieve the effluent goals or discharge.
Water is becoming more and more scare, and where facilities are already seeing these water shortages, local regulations about how much water you can draw from your source and discharge will grow more stringent. If your facility draws your water from or discharges to a municipal source, you might already be experiencing higher sewer connection fees.
When a cooling tower is running inefficiently, it can require too much makeup water and cause excess blowdown. Also, the discharge of your cooling tower bleed must meet local municipal discharge regulations if your effluent is being returned to the environment or a publicly owned treatment works (POTW), so it’s important to address these issues head-on to avoid being fined.
For blowdown, post treatment in the form of reverse osmosis or ion exchange can prove extremely beneficial. This allows liquid and solid waste to be concentrated and removed while treated water can be returned to the tower and reused. These systems depend on the plant location and specific environmental factors.
For example, if a plant is looking to treat the blowdown and about 75% of the water is desired to be recovered and reused, a simple recovery system can be used. If regulatory requirements demand complete zero liquid discharge (ZLD), systems at this level might include evaporation and crystallization.
Demineralization systems can be a cost-effective solution here, as they can help minimize the cost to connect to water and sewer lines.
Being aware of potential cooling tower water treatment issues and knowing how to solve them is essential to the success and efficiency of your process. High amounts of blowdown, low cycles of concentration, local regulations, and water scarcity are all issues that can challenge plant productivity and, if not managed properly, require costly equipment replacements down the road.
When it comes to deciding the right solutions for your cooling tower water treatment, it is extremely important to consult a water treatment specialist. The proper maintenance of your system will depend on your plant’s individual needs.
SAMCO has over 40 years’ experience custom-designing and manufacturing cooling tower water treatment systems. With extensive knowledge about cooling tower chemistry and flow dynamic—in addition to several combinations of technologies that can help you treat your individual makeup water, side-stream filtration, and cooling tower blowdown needs—chances are we have a solution for you, so please feel free to reach out to us with your questions.
For more pricing information or to get in touch, contact us here to set up a consultation with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for your cooling tower water treatment system needs.
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