Maintenance and Equipment:
Cooling towers are inherently dirty systems due to their operation and being open to the environment. As explained in a previous entry, cooling towers harbor a constantly increasing amount of contaminants and impurities. Traditionally, this build up would require the cooling tower to be shut down, drained, and the layers of sediment and other deposits to be manually removed. It is not uncommon for a properly maintained cooling tower to undergo this cleaning twice a year, costing extra in downtime, labor, lost water from draining and refilling the system, and additional cleaning chemicals (PNNL 2012). Side stream filtration, by constantly “cleaning” the water within the cooling tower, provides for considerably longer periods of operation between shutdowns for required maintenance actions, drastically reducing the annual cooling tower maintenance costs. In a study at the Oak Ridge National Laboratory, annual maintenance requirements for a 400-ton cooling tower with a side stream filter were 80% less than a comparable tower not using side stream filtration. In this example, the cooling tower with a side stream filter took half a day to be cleaned out by a vacuum truck, while the non-filtered tower took two and a half days to clean (US DOE FEMP 2014).  In addition, keeping the system cleaner extends the life of the equipment, meaning cooling towers and their components can be used longer before needing replacement or maintenance.

Summary of Study:
Beginning in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration installed an Aqua-Stream™ side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building. The goal of this study was to analyze the effects of the Aqua-StreamTM and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.

Neglecting to perform preventative maintenance can degrade cooling tower performance and increase the water and energy required to cool effectively. It can also shorten the life of cooling system equipment. Side stream filtration can help reduce required maintenance and lengthen the amount of time in between maintenance actions. Pathex® further enhances the effects of side stream filtration by killing waterborne bacteria and improving overall water quality within the cooling system.

Contact us today for more information and to learn how to use Pathex® at your facility!

Summary of Study:
Beginning in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration installed an Aqua-Stream™ side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building (Image 1). The goal of this study was to analyze the effects of the Aqua-Stream™ and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.

Water:
Water is a fundamental component of any cooling tower system, as it is the medium through which heat exchange is achieved.  Cooling tower operation, with side stream filter placement options, is depicted in Figure 1, below. The Aqua-Stream™ filter at the Chattanooga site is located between the pump and heat exchanger (Option 2, below).  As water passes through the heat exchanger, waste process heat is transferred to the cooler water, allowing equipment to operate without overheating. A portion of this hot water is then evaporated in the cooling tower, with the remaining water being cooled for reuse through the heat exchanger.
Cooling towers consume water in two ways: evaporation and blowdown. Evaporation, as seen above, occurs as part of normal cooling tower operation. Because of this, the remaining water retains a constantly growing concentration of dissolved solids. Blowdown manages this issue by purging the water with high concentrations of solids or minerals, often to the sewer system, and refilling the system with clean (usually municipal) water. The longer water can recirculate through the system before blowdown is required, the less water the cooling tower consumes. Side stream filtration helps manage water usage by constantly filtering and removing the suspended and dissolved particles that lead to blowdown. Logically, this translates into water savings, as less make up water is required to operate the cooling tower.

The next entry will examine the maintenance requirements and equipment costs associated with cooling systems and their operation.

Summary of Study:
Beginning in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration installed an Aqua-Stream™ side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building. The goal of this study was to analyze the effects of the Aqua-Stream™ and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.

Energy:
Cooling towers and HVAC systems in general can be massive consumers of energy, simply due to their size and operation. As discussed in a previous entry, insulating concerns such as scaling, fouling, and microbiological activity can greatly increase the energy required for effective cooling. It has been documented that a fouling layer of just 0.001 inches can increase the required power to achieve cooling by 10% (ASHRAE 1998). Since side stream filtration continuously filters the circulating cooling water, contaminants such as suspended solids, organic particles, silt, and others are constantly being removed from the system. Effectively removing waterborne particulates lowers the probability that fouling, scaling, and microbiological growth will occur, improving efficiency and lowering energy consumption (PNNL 2012). A DoE study conducted at the Oak Ridge National Laboratory (ORNL) found that their side stream filtration system reduced suspended particles in the cooling water by greater than 99% (US DoE FEMP 2014). In the case of the Chattanooga study, potential energy savings are further increased with the use of Pathex® in an Aqua-Stream™ side stream filter by continuously killing a high percentage of waterborne bacteria, further lowering the likelihood of insulating activity within the cooling system.

A 2013 evaluation conducted at a ten-story hotel in Washington, D.C. documented the effects of side stream filtration using Pathex® on cooling system operating efficiency. Performance was measured by the change in water temperature (ΔT) between the inlet and outlet flows in the cooling tower system, with gains in heat transfer (increasing ΔT values) showing improved system performance. Data was collected over the first eleven weeks after installation. As shown in Figure 1, the heat transfer was initially calculated at 2.5°F and improved to 10.1°F over the course of the evaluation.









 
The increase in the ΔT variable is significant in that a cooling system’s efficiency is directly related to its ability to extract heat. The antimicrobial action of Pathex® in a side stream filter helps improve and maintain effective operation in cooling systems, ultimately resulting in savings on energy and operating costs.

In the next post, we will look at the relationship between cooling system efficiency and water consumption.

Summary of Study:
Beginning in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration™ installed an Aqua-Stream™ side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building. The goal of this study was to analyze the effects of the Aqua-Stream™ and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.

Bacteria:
As described in the previous entry, controlling bacterial and microbiological presence can help a cooling system operate more efficiently and limit other undesirable issues. A cooling system with bacterial concerns can also be a health issue, harboring pathogenic bacteria such as E. coli and Legionella. These particular bacteria have been known to cause sickness in humans, with Legionella (responsible for Legionnaires’ disease) having caused dozens of fatal infections in the US alone.

Frequently, oxidizing biocide chemicals such as chlorine, chlorine dioxide, and bromine are used to control biological activity. While typically effective, the chemicals are often hazardous to handle, must be constantly replenished, are harmful to the environment, and can accelerate corrosion within the system (GE 2013). The extensive corrosion seen in Images 1 and 2 occurred over only 8 years, the length of time that the cooling tower has been in service. Prior to the installation of the Aqua-Stream™, chlorine was being used to treat the cooling water at the Chattanooga study site. During the year-long study using the Aqua-Stream™ with Pathex® all chemical treatment was suspended. All water samples were taken and analyzed by an independent laboratory. As shown in Image 3, the concentration of waterborne bacteria increased dramatically once the chemical treatment was stopped in mid-October of 2016, quickly approaching the allowable threshold before the effects of filtration were seen.

The combination of the Aqua-Stream™ filter and Pathex® media maintained a reduced bacterial presence via biological control for the remainder of the study. It is worth noting that during the warmer spring and summer months (when the cooling system is being used the most and bacteria thrive) the Aqua-Stream™ with Pathex® consistently maintained cooling system bacteria levels considerably lower than industry standards. Filtration through Pathex® frequently achieved bacteria counts lower than 100 colonies per milliliter (col/mL), and achieved counts as low as 10 col/mL, one one-thousandth of the industry standards set by the Cooling Technology Institute (CTI 2008).

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 188 recommends water treatment plans for a building’s HVAC and water systems to address these issues. Though the standard itself does not have regulatory authority for pathogen control, it is frequently incorporated into building codes. These results demonstrate the suitability of the Aqua-Stream™ filter with Pathex® media as a critical component of a water management plan to meet or exceed the criteria set forth in ASHRAE Standard 188.

The next entry will focus on energy consumption and how it relates to cooling systems and side stream filtration. If you would like to know more or discuss using the AquaStream™ and/or Pathex® at your facility, please contact us!

Summary of Study:
Starting in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration installed an Aqua-StreamTM side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building (Image 1). The goal of this study was to analyze the effects of the Aqua-StreamTM and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.

Overview:
Cooling towers are an important part of many large-scale cooling systems. They typically use evaporation to cool process water, so that the water can be reused to extract heat from the system. Given the purpose of cooling towers, they operate much more efficiently when their heat exchange surfaces are clean.

Cooling towers face four primary water treatment issues that can reduce operational efficiency: corrosion, scaling, fouling, and microbiological activity (PNNL 2012).

• Corrosion – can cause premature structural failures; exacerbated by high oxygen levels  and oxidizing biocide chemicals
• Scaling – precipitation of dissolved minerals; has insulating properties that reduce the efficiency of the heat exchange surfaces; requires more work from the system to achieve desired cooling
• Fouling – insulating film formation on heat exchange surfaces affecting performance and energy requirements of the cooling system; causes include process oils, suspended particles, and biologic growth
• Microbiological activity – can be either suspended or formed on system components; strongly insulating, increasing energy requirements; byproducts encourage further microbiological activity/growth     

All of these can negatively affect operational efficiency and are inter-related, such that an increase or decrease in the severity of one can cause a comparable, parallel change in the others (PNNL 2012). These water treatment issues arise for a number of reasons, including water chemistry, suspended and dissolved solids, dust, and bird and insect activity from the open system.

Multiple reputable studies, including several from the Department of Energy (DoE), have shown that side stream filtration can reduce the prevalence of the concerns described above. These studies also examined the benefits of side stream filtration on water usage, energy consumption, maintenance requirements/downtime, and biological control. Side stream filtration using the Aqua-StreamTM and Pathex® antimicrobial filter media allows for all of these benefits of filtration, with the addition of killing and controlling bacteria and biological activity. The Aqua-StreamTM selected for the cooling tower in this study measures 24 inches in diameter and roughly 80 inches in height, with a total footprint of 36 inches by 48 inches (12 ft2), and utilizes approximately 650 lbs (6.5 ft3) of Pathex® media. The filter operates with its own control system, virtually eliminating the need for any maintenance actions. Pathex® antimicrobial filter media does not degrade and is rejuvenated daily by the filter’s control system through a programmed backwash cycle.
 
The next entry will examine waterborne bacteria in cooling systems and the effect of Pathex® on these issues.

Recently, PathShield™ Antimicrobial Filter Media was approved, registered, and licensed by the California Department of Pesticide Regulation for the reduction and control of coliform bacteria. More information to follow!

Now that cooler weather is upon us, it’s time to perform HVAC system maintenance and lay up cooling towers for winter. If your system struggles to keep up with the summer’s heat and humidity, now is the perfect time to evaluate your cooling water treatment program and consider making a switch.
 
Take, for example, a hotel in Washington, D.C. that traded biocide chemicals for Pathex filter media and hasn’t looked back:

The Problem
Biofilm, scaling and corrosion were winning the battle in the cooling tower of a Washington, D.C.’s 10-story hotel. Resulting operational inefficiencies in the 200-ton cooling tower led to guests complaining about hot, muggy rooms.

The Solution
An Aqua-Stream high-efficiency side-stream filter, fitted with Pathex antibacterial filter media, was installed. The Aqua-Stream efficiently filters suspended solids, and Pathex replaced the oxidizing chemical biocides that weren’t adequately killing bacteria in the cooling water.
 
Together, the products improved heat transfer efficiency, reduced water and energy consumption and decreased maintenance needs for the hotel – ultimately resulting in cooler, more comfortable rooms for hotel guests.
 
The Outcomes
Cleaner air, cooler water and significant savings.
 
Read the case study for additional outcomes or contact us to discuss your cooling tower filtration needs.

Already have a side-stream filter? Consider switching to Pathex filter media to boost the power of your filter. It’s a drop-in replacement for most sand and multi-media filter beds. Pathex kills bacteria on contact without using or leaching chemicals.

Whether your goals are to cut costs, reduce maintenance pressure on your staff, or do good for the planet, AS Filtration’s sustainable water treatment solutions are up to the task.
 
Here are 6 reasons why sustainable water treatment makes sense: 
 
1. Reduce chemical use
The leading water treatment solutions include chemicals for controlling bacteria, but those same chemicals also speed corrosion and scaling in pipes and tubes, shortening the lifespan of HVAC equipment, and, ironically, spurring the need for additional chemical treatments. 

2. Say good-bye to harmful byproducts
Water treatment chemicals, such as chlorine, can create hazardous disinfection byproducts that are considered harmful to humans and animals.  
 
3. Worker and facility safety
Some chemicals used in water treatment programs are explosive in high concentrations, and most are dangerous to handle and store requiring compliance with  special worker training as well as added material record keeping.

4. Decrease pressure on limited resources
Severe drought conditions over the last year underscored the need for clean water. Using sustainable water treatment products stretch the useful life of process equipment while reducing water and energy consumption.  

5. Financial savings
Saving water and energy translates directly into bottom-line savings. But the savings don’t stop there – decreased reliance on chemicals means less money spent buying, storing, and handling chemicals. And, choosing products that effectively clean and filter water without contributing to scaling and corrosion means your equipment will last longer and need less labor and downtime for maintenance. (Read more in our blog: 4 Ways to Save Big on Cooling Tower Costs). 

6. Get noticed
Local and national programs reward and recognize facilities that reduce their environmental impact through sustainable practices and products. AS Filtration’s products can help you earn LEED certification points and / or achieve ENERGY STAR certification. (Read more in our blog: Become an Energy Star). 

​Ready to go green with clean, blue water? Contact us today to find out how our sustainable water treatment solutions can solve your water woes and meet your budget goals.

The Federal Energy Management Program (FEMP) offers guidance for reducing water usage and improving water efficiency, and their Best Management Practices publication includes a section on cooling tower management. Although the FEMP resources are designed specifically for federal businesses and campuses, they’re best practices that can help all building owners and managers save money on cooling tower operations.
 
The FEMP’s best practice #10 offers water efficiency opportunities for cooling towers, and we’ll focus on three of those tips:

1. Maximize cycles of concentration
2. Install side-stream filtration
3. Consider alternative water treatment options

 
Cycles of concentration
Maximizing cycles of concentration reduces water lost through blowdown, thereby minimizing the amount of water needed as make-up water. Significant water savings can be achieved by running lengthier cycles, but using the same water for a longer period allows dissolved solids to accumulate between blowdown flushes, causing scaling and corrosion problems.  The extent of those problems is highly dependent on environmental factors and the quality of your makeup water.
 
The next two water efficiency recommendations, however, provide solutions for increasing cycles of concentration in new and retrofit configurations.
 
Side-stream filtration
Side-stream filters run continuously, filtering sediment from a portion of cooling water and returning clean water back into the system. This process prevents the buildup of scaling and biofilm and requires fewer maintenance interruptions. High-efficiency side-stream filtration also improves operational efficiency, saves water, and reduces the need for water treatment chemicals.

Learn more about high-efficiency side-stream filtration in “2-in-1 Solution for Industrial and Commercial Cooling Tower Water Treatment.”
 
Alternative water treatment options
The FEMP guideline here is a bit vague but refers to the fact that new treatment options can be effective tools in your arsenal for cutting chemical use and saving water. AS Filtration’s antimicrobial filter media, Pathex, is one such solution. Pathex is EPA-registered as a pesticide and is a proven tool for destroying waterborne bacteria on contact. The filter media enhances the efficacy of side-stream filters by removing not only suspended solids, but also by controlling bacteria as water is filtered. Pathex is a drop-in replacement for most sand and multi-media filters.
 
Our blog, How Clean is Your Water Filter?, compares water disinfection technologies and shows how Pathex filter media stacks up against traditional treatment options.
 
For more best practices in cooling tower management, read the FEMP’s full Best Management Practice #10.
 
To talk with an experienced engineer about your water efficiency needs, contact us.