Water filtration is an essential function of any cooling tower operation that provides crucial protection. Without effective water filtration, cooling solutions would be unable to remove harmful contaminants that cause corrosion, fouling, and scale.
Because cooling towers are air scrubbers that suck in anything in the vicinity—including construction materials, leaves, environmental debris and litter—it’s important to have a robust filtration system capable of removing larger contaminants. Often, cooling towers also contain areas where stagnant water collects, creating an environment for bacteria to grow and biofilms to form, which results in troublesome fouling issues. Waterborne pathogens, especially Legionella, are a major risk due to their ability to multiply rapidly.
Due to these risk areas, cooling towers face increased maintenance costs, stringent environmental regulations related to deploying adequate water programs, Legionella testing, and bookkeeping, and increased downtime resulting from corrosion, fouling, and scale.
Advanced water filtration is the most effective solution to reduce particulate contamination.
Cooling Tower Water Treatment Process
Impact of Advanced Water Filtration
Cooling towers provide the perfect environment for bacteria to grow. While many programs utilize biocides in addition to scale and corrosion inhibitors to help reduce and control biofilm, a key piece of the puzzle is still missing. Advanced water filtration provides that missing layer of protection to minimize corrosion, fouling, and scale.
A water quality analysis may be performed to learn the size of particles present in the water, this will then provide direction as to where filtration is needed to ease operation and enhance performance downstream.
Problem areas vary but are typically related to dirty makeup and side stream water, along with basin sediment build up. Failure to resolve these problems results in contaminated water reaching the cooling tower and heat exchanger. Closed loop systems can also benefit from filtration as these typically have high oxygen rates which increase corrosion.
Regardless of where in the system you decide to leverage water treatment, advanced water filtration enables efficient operation and extends the lifecycle of cooling tower equipment. Ultimately, improved operational efficiency leads to tangible energy, water, and money savings.
Downstream Benefits Include:
Reduced Energy Use
Controlling and mitigating particulate fouling improves efficiency in heat exchange and results in improved overall system efficiency.
Improved Chemical Performance
Less reliance on chemicals to mitigate particulate buildup results in a reduction of chemical and mechanical cleaning costs, maximizing chemical program effectiveness.
Lower Maintenance Costs
Protecting expensive cooling tower assets will decrease the need for chiller maintenance and repairs or the need for replacement altogether. Advanced water filtration is more efficient compared to traditional methods of cleaning a cooling tower (i.e. draining the tower and shoveling sediment from the sump which has significant costs in downtime, labor, lost water and chemicals).
Less Downtime and Improved Productivity
More effective prevention, reduction, and mitigation will minimize costly downtime and reduce the overall cost of operation.
Advanced Water Filtration Solutions
Evoqua offers a broad selection of filtration solutions to remove suspended solids and control contamination in the recirculating water stream. Microsand media filtration, automatic self-cleaning screen filters, and Hydrocyclone separators all are utilized within a cooling system.
Hydrocyclone Centrifugal Separators:
While not a filter, Hydrocyclone Separators provide automated, robust solids protection as they specialize in separating dense particles to reduce high suspended solids in cooling tower systems. Hydrocyclone separators are effective in removing suspended particles from any flow stream of water where the specific gravity (density) of the particles is heavier than the water it is in. the larger the difference between the particulate and water specific gravity, the better the separation efficiency.
Hydrocyclone separators spin water in a tight column and use the resulting centripetal force to remove high density solids in the water. Solids are collected in a purge chamber which flushes on a timed basis. Evoqua’s hydrocyclone separators don’t contain moving parts which minimize maintenance and downtime*.
Velocity is also an important consideration—be sure to size the pump and flow rate to accurately determine viability and maximize performance. This technology performs well for particles with a specific gravity of 2.6 or higher.
V-Series Automatic Screen Filters:
Filters come in several configurations from 30GPM to 2000 GPM on skidded and non-skid offerings. Leveraging a patented bi-directional screw design, the V-Series technology provides robust, versatile filtration using its own internal water pressures for the filter to clean itself. The simple yet sophisticated operation doesn’t leverage any external electric motors or pistons. Using inlet water pressure to clean itself, a differential pressure builds over time within the filter triggering controlled flus valve across high pressure and low-pressure zones which creates flow throughout main chamber that flushes the equipment. Nozzles clean 100% of the surface area of the screen. The cleaning cycle takes less than 15 seconds and does not interrupt the filtration process. Filtration continues even during a flush cycle.
Because the screen filters don’t contain hydraulic pistons or electric motor and gear boxes, they are considerably easier to maintain. With only ~90 parts compared to piston and electric drives that contain many more, Evoqua’s V-Series™ filter provides the lowest cost operation and maintenance.
Applications perfectly suited for the V-Series V 200 automatic filter include process water, cooling tower filtration, pre-filtration of membrane, pump station protection for irrigation, or wherever suspended solids are removed from 1000 micron down to 10 micron for flow rates 30 to 2000 GPM.
This technology has the lowest flush waste in industry at less than 1% of overall feed flow. The filter’s bi-directional screw and seals should be maintained annually as part of a preventive maintenance program.
Vortisand® Industrial Filtration System:
Evoqua’s Vortisand high efficiency media filter provides the most mission critical asset protection. This is a trusted solution for those monitoring daily approach temperatures, kilowatt/hour draw on cooling tower motors, or chiller runtime requiring the highest level of insight and protection.
In cooling systems, fine particles, particularly those 1-5 micron are the first to cling to surfaces and are very problematic in terms of creating the first layer of biofilm that accumulates and contributes to fouling and corrosion. By using the Vortisand media filter, operators can eliminate fine particles to help reduce fouling and corrosion. Vortisand filters are capable of removing particulates - even atmospheric dust, down to ½ micron utilizing high efficiency microsand media technology
Focused on particulate filtration, Vortisand media filters provides automated self-cleaning unlike bag and cartridge filters. Very different from traditional media filters, Voritsand filters leverage microsand media that measures 0.15mm in diameter resulting in high quality effluent which reduces biofouling growth rates in cooling systems. Unlike other media filters, this technology also utilizes a cross-flow pattern via the VortiJetTM injector across the surface of the media to reduce media surface blinding. The combination of microsand and cross-flow injection yield high performance and high velocity at the same time—a very unique outcome that enables such high performance. Additionally, the Vortisand system’s shallower bed reduces the backwash flow requirements resulting in a 50% reduction in water consumption versus traditional media filters.
The Vortisand system media layer generally needs to be replaced only once every 5 years.
As energy efficiency and resource conservation gain more importance, facility owners and engineers are recognizing the dramatic improvements they can achieve by efficiently removing solids from cooling water.
When considering adding a new filtration component to your cooling tower, you must start by understanding what’s in your water in order to select the right technology. With so many operation parameters and performance capabilities, you first need to determine where filtration makes the most sense based on where solid loadings are arising and the particulate size in your water.
Contact Evoqua if interested in conducting a variety of extensive lab services, including particle size analysis, total suspended solids, turbidity testing: Contact Us
*a pump may be needed to maintain pressure