13th Mar 2024

How side stream filters improve water filtration performance in buildings

Closed-loop water circuits, deployed as part of a building's environmental control systems, are prone to contamination from suspended solids. This contamination often results in poor temperature control within the building. Side stream filters play a hidden but vital role in maintaining the quality of these systems.

What is a side stream filter?

A side stream filter is used to remove contaminants from a building's closed-loop water system. They’re typically installed inside the plant room. They’re called side stream filters due to their position in the system and the fact that they don’t filter the entire flow at once.

Side stream filters work by filtering 5-15% of full flow so that the complete system volume is filtered 2 or 3 times every 24 hours.

We generally recommend a cartridge side stream filter system, but other technologies such as hydro-cyclones and separators are suitable for filtering out large debris. However, these solutions lack the high efficiency of cartridges. A typical system from Amazon Filters would consist of a Stainless Steel 61 Series filter housing containing disposable Amazon SupaSpun II filter cartridges.

We recommend the use of these absolute filters as, unlike nominal filters, they maintain their removal efficiency for contaminants through the lifetime of the filter, even under varying water quality conditions. It's typical for nominal filters to suffer reduced removal efficiency or to unload previously retained contaminants after a period of use and this will cause unexpected system fouling.

A side stream filtration system can also be used to:

  • Remove suspended solids, reducing wear and tear on critical water circuit components
  • Minimise system biofouling and reduce the use of chemical antifouling treatments
  • Eliminate trapped air
  • Minimise time and labour compared with conventional flushing regimes
  • Achieve cleaner systems
  • Reduce maintenance, equipment downtime, and repair costs

Better water filtration = less downtime, fewer changeouts, and slicker production. Read our guide to start improving your processes.

What do side stream filters remove?

Side stream filters remove suspended solids produced by the corrosion of pipework and other components of the system. Side stream filters also significantly reduce the buildup of biofilms and pseudomonas (bacteria) to prevent biofouling in water-based systems.

However, it's important to note that retrofitting filters into a contaminated system won't remove biofilms entirely. Side stream filters should be installed into clean systems to significantly reduce the development of contaminant biofilms.

Our SupaSpun KilBac filters use KilBac anti-microbial and anti-algal technology to reduce the build-up of biofilms over time. Our filters feature micron-sized zeolite particles that contain active silver, zinc, and copper. These particles suppress the growth of algae and bacteria on the filtration media.

Why do closed-loop systems need side stream filters?

Closed loop water circuits in building heating and cooling systems typically become contaminated during fabrication with materials such as mill scale, jointing compound and building debris. Over time, pipework and biofilm corrosion builds up to form suspended solids that can also cause contamination. If these materials are allowed to remain in the system they’re likely to cause component blockage and damage to control valves and small bore heat exchanges.

Side stream filters have a direct impact on energy efficiency

Many organisations are committed to developing and implementing more efficient energy plans. The main aim of these plans is to balance the key principles of energy efficiency, sustainability, financial validity, environmental enhancement, and social responsibility.

But the drive to install water systems that are more energy efficient has resulted in smaller orifices in control valves and lower flow rates in terminal units. Smaller orifices become blocked faster and more regularly by contamination, which is why optimal filtration systems are essential.

Efforts to increase energy efficiency through new technology and operational strategies are highlighted by references in two BSRIA publications:

To ensure the optimised performance of efficient components, especially in new build, retrofit, and refurbishment projects, side stream filtration should be considered a top priority. This will also offer the benefit of reduced system maintenance and improved energy efficiency.

On applications with high iron content, Rare Earth Ferrostik magnetic assemblies are used to remove iron-based contaminants. System efficiency can also be enhanced by installing automatic vent valves on the filter housing to help eliminate trapped air from the system.

BSRIA: What industry leaders advice

The Building Services, Research & Information Association (BSRIA) issued a second addition to its Water Treatment for Closed Heating & Cooling Systems document (BG 50/2021) in October 2021. 
In this document BSRIA states that filters and separators can reduce energy consumption. 

Specifically, it points to the use of filters separators ‘to permanently maintain a low concentration of suspended solids in the circulating water and reduce the risk of solids deposition, settlement and subsequent under-deposit corrosion in areas of low flow’. 

BSRIA also recommends that the side stream is sized so the total system volume should be able to pass through it in a 24-hour period.

For more details of the BSRIA guidance click here.

6 benefits of installing side stream filtration systems

  1. Protection of automated valving from fouling ensures reliable building temperature control
  2. Removal of suspended solids reduces abrasive wear and tear on process plant
  3. Removal of chemically treated biomass further reduces pipework degradation
  4. Trapped air is kept separate from the system
  5. Time and labour costs are reduced when compared to conventional flushing processes
  6. Maintenance, equipment downtime, and repair costs are all reduced

Our side stream filters in action

Side stream filtration for a climate control water system

Side stream filters for the chilled water (CHW) and condensate systems were specified by a client to ensure reliable and accurate temperature control at a financial institution’s high-profile European headquarters. This is a critical requirement as the building is the home of significant amounts of electronic data.

The system volume was in excess of 250,000 litres of glycol therefore 10 filter housings were located at various points throughout the building, operating at significant pressures of 10-24 bar. Due to the high flow rate involved a 5% side stream flow was specified.

We supplied:

Due to the building's construction, the main plant room was located below ground. As such, several filter housings were required to operate at 24 bar working pressure, much higher than typically found in these systems.

Despite needing special high-pressure filter housings Amazon manufactured and delivered what we needed on time to ensure project deadlines were maintained. They also offered substantial on-site support during installation, flushing and commissioning ensuring a successful conclusion.

– Site Project Manager

Side stream filters are the hidden asset of closed-loop systems

Efforts to modernise heating and cooling systems and improve efficiency have resulted in the use of key components that are more vulnerable to contamination from suspended solids. If this isn’t managed by improved system design, it becomes prone to partial or total failure.

We have an extensive understanding and knowledge of water circuits in the building services sector. This enables us to provide optimum side stream filtration solutions for closed-loop water circuits and cooling tower loops. Get in touch today to see how we can support your estate’s closed-loop systems.

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