The cooling market is growing, and industry managers are under pressure to increase efficiency and reduce costs. Clean water is an integral part of the process. Improved technologies continue to evolve to ensure optimum system performance. Evoqua is a global leader in water treatment. The team are experts in water filtration. Water Online interviewed Keith Karl,Vortisand® Cooling & Process Water Filtration Expert at Evoqua, to learn about trends in the cooling industry and the need for high-quality water.
A number of factors are creating a demand for high-efficiency filtration for HVAC systems and cooling towers:
Total suspended solids (TSS) under 5.0 microns in size are key contributors to biofilm formation. Biofilm buildup increases energy costs to operate chillers and heat exchangers. There has also been an increase in health-related incidents, such as Legionella, related to cooling towers. Keeping the condenser water as clean as possible plays a vital role in providing a safer environment, while enhancing a biocide chemical treatment program. Our findings from laser particle distribution analysis show 85 percent of the particles in cooling tower water samples measure under 5 microns.
Water reuse is a growing business market. Municipal water authorities have put more restrictions on potable water use for industrial/commercial cooling water. The basic concerns about water reuse involve capital costs versus operating costs to provide a trouble-free cooling water system. Depending on the level of treatment, reuse water may contain high volumes of fine suspended and dissolved solids. This can create problems with clogging, scaling, or biofouling of system components. These issues result in unscheduled shutdowns, additional maintenance costs, and heat exchanger inefficiency. As noted above, health effects from bacteriological contamination may also occur.
The water sources used for cooling tower makeup water, whether potable, well, surface, or tertiary treated wastewater, each bring different challenges and solutions.
Data centers come in many different designs and sizes with various types of cooling configurations. There has been a push to use lower water demand equipment, such as air-cooled economizers and evaporative coolers. This equipment reduces the amount of open cooling loops while increasing the closed cooling water loops. Semiconductor manufacturers, on the other hand, require the cleanest water possible for final production purposes. Treating/filtering the bath tank water is critical in all bath tank phases, not only for the process, but for any heat exchange systems that might be installed using that water. We are seeing a trend where customers are utilizing both ultraviolet disinfection technology and high efficiency filtration to improve the quality of cooling tower water.
Providing the cleanest filtered water can reduce or maintain overall system efficiency. Removing fine solids can result in energy savings, chemistry enhancement and savings, improved equipment lifecycle, and reduced labor and downtime by optimizing water quality and efficiency.
Providing submicron quality water reduces the risk of biofilm fouling on heat exchangers, chiller/condenser tubes, and cooling tower fill. Reducing such risks can result in reduced energy costs, allowing the heat exchangers to work at their designed efficiencies. Cleaner water results in more effective chemical treatment and reduced usage. A cleaner system requires less manual cleaning costs. In a controlled test, submicron filtration was able to reduce cleaning frequency from every 6 months to every 16 months. High-efficiency filtration helps extend the life of your total system, including piping (reducing the potential for corrosion). If used in pretreatment, it will protect the downstream systems, including the manufacturing process and the end product. Finally, the entire system will operate as intended, which can achieve higher efficiency levels.
This depends on the type of end user. Companies often rely on their chemical treatment provider or energy management system provider to develop a risk assessment program. A risk assessment program will require input from the staff along with outside resources. Many companies outsource this service, requiring a third party to fill in the documentation during each visit. The data available to the end user is extremely valuable and helps identify a concern before it impacts your business. The program should include a review of the filtration and disinfection process. Using high efficiency submicron can also enhance the effectiveness of disinfectants and thereby reduce potential health effects.
High efficiency media filtration reduces TSS, the nutrient food source for bacteria, by greater than 80 percent. This reduction enhances the chemical treatment program. Suspended solids(TSS) can both adsorb water impurities that are nutrient sources for bacteria and also shield attached bacteria from contact with disinfectants. High efficiency media filtration reduces TSS and thus is capable of both reducing bacteria growth and improving disinfectant efficiency.
Not all high efficiency submicron sand filters are created equally. Vortex type versus cross-flow microsand filters operate under different principles. A cross-flow microsand filtration system is designed to scour TSS across the microsand. These filters allow fine suspended solids to agglomerate at the surface while water is flowing downward. On a nominal basis, the Cross-flow technology is capable of removing particles under one micron. Particles that pass through will be filtered on subsequent passes, as the filter cycles water volume multiple times per day. The removal rate depends on the nature of the water, its clarity and cleanliness. Based on laser particle distribution analyses, these filters have achieved 98 percent removal of particles less than 1 micron, and 99 percent removal of particles greater than 1 micron, over a 60-day period.
The most important advantage of high efficiency submicron filtration is the reduction of TSS down to the 0.5 submicron range. VortiJet™ injectors allow for cross-flow sweeping across the media surface, resulting in increased filtration performance and efficiency. Cross-flow technology provides even distribution of TSS and water across the entire media surface. This eliminates media channeling and carryover. Efficient backwash cycles and low backwash water demand are additional advantages. Cross-flow microsand filters are resistant to entrapped air that can channel media like many other traditional sand filter designs. A heavy-duty media configuration can be more resistant to damage caused by channeling. Vortisand® systems operates between 15 – 24 gpm/sq. ft. of media surface versus 3 – 7 gpm/sq. ft. for conventional sand filters. Smart control packages are also offered. Cross-flow microsand filters provide filtration of a higher flow within a smaller footprint. The cross-flow and microsand technology allows for construction of a stacked vessel, doubling the capacity within a similar footprint as one horizontal vessel, compared to multiple vertical vessel filters of equal flow capacity.
