Side stream industrial water filtration systems reduce the amount of suspended solids, organics, and silt particles by continuously filtering a percentage of the cooling tower water (5-15%). Left untreated, this will lead to scaling, fouling, and microbiological activity, and eventually the cooling system will suffer from reduced efficiency. The filtered water is then returned to the cooling water system for reuse. Side stream filtration is typically used in high-flow cooling towers.
When to Consider Side Stream Filters
There are some key parameters indicating that a side stream filtration system is needed:
* The source of makeup water contains high levels of suspended solids, iron, biological and/or organic contamination.
* Biological growth is an issue although biocide treatment is used.
* The need to clean chillers and heat exchangers more than every 12-16 months.
* High corrosion rates in the water loop, including its components.
* The cooling tower system shows signs of diminished heat transfer and efficiency.
* The cooling tower sump and/or fill has a high accumulation of solids.
Benefits of Using Side Stream Filters
There are numerous benefits that can yield a high ROI by implementing side stream filtration. It is worth mentioning that not all benefits are applicable for all systems or environments and understanding the water quality and contaminants present is recommended before making a commitment.
* The corrosion inhibitor will be protecting cleaner surfaces given that solids have been filtered out of the system. This reduces corrosion rates and increases equipment lifetime.
* Side stream filtration, when paired with chemical treatment, will maintain a cleaner system, thus reducing the need to mechanically clean sumps and exchangers. This in turn lowers maintenance costs.
* Side stream filters keep the system clean for better heat transfer rates, for longer periods, lowering operational costs.
* Removing suspended solids from circulating water can in some cases deliver higher cycles, reducing the need to replace membranes and lowering maintenance costs.
Applications for Side Stream Filters
A side stream filtration system can improve the water quality and the efficient use of energy in these applications, usually in systems where the flow is more than 60 m3/h:
* When the primary source of makeup water is either surface water or other unclarified source, such as, rivers, streams, lakes, etc., it may contain biological and/or environmental contaminants. These contaminants are too small to be caught by the grate or screen protecting the piping at the inlet, but they will be trapped by a side stream filter.
* When systems have challenging biological issues and biocide programs are implemented, the number of dead organisms increases. A side stream filter will trap and remove them.
* Cooling tower systems are prone to fouling even when an anti-foulant program is implemented. A side stream industrial water filter will reduce the fouling.
* Scaling deposits are a cause of heat transfer loss. By reducing fouling, side stream filtration can help keep the heat transfer surfaces scale-free.
* Cooling tower sumps can contain high levels of airborne particles (dust, debris, etc.) which can lead to high dirt loads. A side stream filter will trap these particles that otherwise would contaminate the cooling supply.
How a Side Stream Filtration System for a Cooling Tower Works?
1- Partial Water Intake: A small portion of the recirculating water is diverted from the main cooling tower loop into the side stream filter system.
2- Filtration: This water passes through one or more filtration technologies, such as:
Sand filters, multimedia filters, cartridge filters, and automatic self-cleaning filters. These systems remove suspended particles, biological matter, and chemical residues.
3- Clean Water Return: The filtered water is then returned to the cooling tower basin or main loop, helping maintain better water quality throughout the system.
System Implementation Considerations
The following factors should be examined carefully when considering installing a side stream filter to verify that the system is suitable for the application. Consulting with an expert to help choose the most suitable side stream filter is essential.
* Particle removal analysis:
Lab and visual tests will indicate how clean the system is. A side stream filtration system that is correctly chosen and sized will effectively reduce fouling and clogging.
* Filtration sizing:
To get the best performance, the side stream filter needs to be sized. The 2 key factors when sizing the system are flow rate and filtration efficiency. The flow rate should reach a percentage of the full recirculation flow rate, depending upon the chosen filtration technology’s ability to eliminate particles from the recirculation water with more efficient technologies requiring less of the recirculation flow due to their ability to remove a greater number of particles.
* Installation:
There are 2 typical ways of installing cooling system side stream filters:
1- On a tap off the water flow line: a percentage of the flow downstream of the pumps is filtered and then returned to the full flow stream by using a booster pump or sent back to the basin (no additional pumps required). The downstream effect on cooling capacity may influence the cooling water flow rate pressure sent to the heat source and this should be taken into consideration.
2- Off basin/sump: the side stream filter takes tower sump suction and then the treated water is returned to the basin. A dedicated pump rated at the necessary flow rate, a control valve and a controller are required for this type of installation. The filtration system’s operating pressure, as recommended by the manufacturer, is also required. This would be the preferred option for process towers.
Conclusion
Side stream filtration effectively removes suspended solids from cooling water, improving heat transfer and reducing fouling. Implementing side stream filters lowers maintenance costs and extends the time between required mechanical cleanings. Side stream filters contribute to longer equipment lifespan by reducing corrosion and scaling. Proper sizing and selection of side stream filtration systems are crucial for optimal performance and cost efficiency. An ROI analysis helps in evaluating the financial benefits and costs associated with installing side stream filters.
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Reference
1-Benefits of Side Stream Filters for Industrial Use
https://amiad.com/blog/benefits-of-side-stream-filters-for-industrial-use/
2- Role of Side Stream Filter in Cooling Tower Care
https://ionexchangeglobal.com/role-of-side-stream-filter-in-cooling-tower-care/
