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.

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.

Begin updating your water management program today 

In our previous entries, we touched on the basics of the ASHRAE Standard 188-2015, why it’s important, and what buildings and facilities are impacted. Now, we’ll take a look at what you should do to follow the published guideline. 

Establishing a water treatment program
Most cases of Legionellosis are the result of exposure to Legionella bacteria associated with building water systems, so the standard requires use of a water management program to reduce the risk of Legionellosis associated with those systems. 

The water treatment framework within the standard includes these components: 

• Program team identification
  Indicate who is responsible for implementing and monitoring the water management program. 
  

• Description and analysis of building water systems
  Indicate the location and flow of water systems, then identify those that pose the most significant risk for Legionellosis and note where water treatment can be applied. 
  

• Control measures
  This is the heart of the standard. Choose and install water treatment measures to effectively reduce the risk of Legionella. Document all treatment measures taken, their implementation schedules and processes, measurement parameters, and corrective actions for each control measure. 

 

• Verification and validation
  Outline specific, scheduled reviews of water treatment program documentation and processes to ensure the program is being implemented. Then, perform periodic water sampling of building water systems to validate the efficacy of your treatment measures. Routine testing specifically for Legionellosis is the most direct method for confirming the effectiveness of your program. 
  

What should I do with the written plan and program compliance information?
Simply keep the documentation and make it available for review as needed by the party or parties responsible for enforcing the requirements of ASHRAE Standard 188-2015. 

AS Filtration’s Legionella Risk Management Solutions
Your water management program must include disinfectant to kill or inactivate pathogens, as well as water treatment products to control microbiological activity, scale, and corrosion.  

The Aqua-Stream filtration system has been proven to kill and control waterborne bacteria while removing suspended particles as small as 0.5 micrometers (microns).  

Pathex® antimicrobial filter media removes particles and controls waterborne bacteria. It’s included in our Aqua-Stream filtration system and is also a drop-in replacement for most sand and multi-media filters. Unlike plain sand filters that often harbor bacteria, Pathex kills waterborne bacteria on contact. Pathex is EPA registered as a pesticide under FIFRA sec 3(c)(7)(A) and is certified by NSF International to NSF/ANSI Standard 61 for drinking water system components.  

For more information, please visit our Legionella Risk Management Solutions page or contact us for a free consultation.

Your cooling tower is home to hidden savings opportunities that significantly reduce energy and water consumption in your facility. Over time, patchwork repairs, general neglect, or changes in facility needs mean your cooling tower may not be operating in top form. Performing these 4 steps can keep your cooling tower working in tip-top shape, improving its reliability and extending its operating lifespan:

1. Catch problems early by tracking key parameters
A log is an early warning system for any developing problems with your equipment. By regularly checking and tracking the key components of your cooling tower, filters and treatment system, you’ll be able to quickly spot and address trends and outliers that may signal a looming problem. Catching those deviations early can help avoid costly maintenance and repairs down the road.

Cooling tower water treatment measures to track may include: water hardness, alkalinity, suspended solids, total dissolved solids (TDS), pH balance, chlorides, sulfates, silica, iron, manganese and ammonia.

2. Perform regular maintenance, like inspections and cleanings
In the case of your cooling tower, half an ounce of prevention may be worth a lot more than a pound of cure. Dirt, dust, pollen, algae, scale, fluctuating temperatures, process variations – any of these can add up to a quickly escalating problem if a cooling tower is left unchecked for too long.  Keep things humming along and avoid costly problems by regularly inspecting and tuning your equipment in accordance with its service plan.

Regular maintenance can help your facility reduce bleed-off, extend equipment lifespan, and keep operational and maintenance costs in check. It’s much cheaper to perform routine maintenance than to let a problem with your equipment or cooling water spiral out of control.

3. Use a filter to keep the system clean
The cleaner your system, the more efficiently it will operate. Although running higher cycles of concentration may save money on blowdown in the short term, that choice could be an expensive one in the long run if your water isn’t being filtered properly. Those higher cycles allow more suspended solids to accumulate in the water, leading to scaling, bio-fouling, corrosion, decreased heat efficiency transfer and higher energy costs.

Side-stream filtration devices, such as the Aqua-Stream, can remove even small (< 30 microns) suspended solids to permit high cycles of concentration without the build up of waterborne deposits. These systems continuously cycle a portion of your cooling water, reducing the need for system downtime, water treatment chemicals and maintenance hours. The Aqua-Stream requires 50% less backwash than other filters, further compounding savings.

By simply making the most use of the water in the system with adequate filtration and treatment, your facility can save money on makeup water, blowdown and associated sewer expenses.

4. Control biological growth
Cooling towers present the perfect conditions for biological activity thanks to their warm, moist environments. Biofilms are particularly problematic, as they have strong insulating properties, contribute to fouling and corrosion, and produce byproducts that further micro-biological growth.

Keeping biological activity in check has the added benefit of also minimizing the likelihood of scaling and corrosion. One method for controlling this growth is adding Pathex antibacterial filter media to your cooling tower water treatment plan. The silica media kills bacteria on contact without chemicals or harmful byproducts and provides protection for years. It’s a drop-in replacement for sand and multi-media filters that can deliver significant savings over the life of your cooling tower by reducing water, energy, maintenance and chemicals.

To save money on your HVAC system, look no further than your cooling tower. With these 4 steps, you can uncover significant savings on energy, water, maintenance and chemicals.

Learn more

To find out more about AS Filtration’s solutions for finding savings in your cooling tower with filtration and treatment, visit our cooling water solutions page. There, you’ll find a case study demonstrating 375% improvement in heat transfer efficiency in a project using Aqua-Stream and Pathex cooling tower water filtration solutions.

If you would like to discuss how our filtration and treatment solutions can be applied to your specific situation, please call 423.602.9520 to speak to one of our engineers, or complete the Contact Us form.