Treat and protect for life

James Townley, water treatment, ENWA Water Technology, side stream filtration
James Townley

James Townley explains that effective water treatment is more than simply cleaning; it also protects pipework for better performance and life-time costs.

Effective water treatment can best be defined as a preventative approach. It protects water-side components from physical, chemical and biological processes that would otherwise impair their function, and reduce their life.

The impact of water treatment on piped services is important, because operators of commercial buildings deliver a service. This includes good heating and cooling as well as domestic water services. If these fail, there is a direct impact on business. Tenants of commercial building space don’t want to be inconvenienced by failing air conditioning or heating systems. Or have to live through the re-fit of pipework that has been damaged.

Even if heating and cooling continue to operate for some time with damaged pipework systems, they will inevitably do so at a reduced efficiency and effectiveness.

Sites where this sort of poor performance can have major impacts include data centres. These buildings employ critical chilled water systems to cool server racks and ensure continuous operation. Failures in the financial sector would run into millions of pounds per day, and cause business continuity problems for web-based businesses.

District heating is another, increasingly widespread, technology that relies on effective pipework operation. Fine strainers on heating interface unit (HIU) inlets can become blocked with corrosion by-products. Heat meter function can be impaired, making it impossible to meter for heat delivery.

Why it matters

With any form of preventative maintenance, the consequence of not following an effective strategy is expensive remedial action. Permanent damage can be sustained.

Re-cleaning and flushing a closed system could costs tens of thousands of pounds – a bill that would make the preventative strategy seem pretty good value. And as a system deteriorates over time, building owners can be faced with spiralling, and un-budgeted, costs for maintenance call-outs and replacement parts. What’s more, it is not simply the pipework that could be damaged.

Lack of effective water treatment will almost inevitably reduce the operating life of key components, including boilers, chillers, fan coil units and heat exchangers. There are also safety implications including loss of structural integrity of high pressure/temperature pipework.

Preventative treatment

Where water treatment is employed, the traditional approach is by manual dosing of chemical-based corrosion inhibitors. This can work well, provided the system is protected from the first moment that fresh water meets new pipework, and that effective concentrations are maintained throughout the life of the system.

On new build projects, the challenge is to passivate internal surfaces as quickly as possible, then to maintain adequate protection through complex flushing, pressure testing, commissioning and hand-over stages. Large constructions with multiple systems continue to present challenges where compliance to industry standards (as recommended by BSRIA) are a requirement for successful completion.

On existing systems, failure to recognise the extent of water exchange can often lead to dilution of inhibitors, significantly reducing their effectiveness. There is an ongoing requirement to monitor and redose closed system, which often falls by the wayside. Options for automated dosing should be investigated to reduce risk from non-performance, whilst reducing H&S, COSHH and handling concerns.

Other water treatment processes would include scale inhibitors, biocides for bacterial control, air removal and water softening for fill water.

In most cases, it is the particles generated by a failing water treatment regime that cause more problems that the process itself. For this reason, many systems have included separation/filtration devices, which can have a big impact on the reliability and efficiency of closed systems.

Settlement type devices have been used for many years, and would include the familiar in-line dirt separators and enhanced settlement devices such as hydrocyclones. These systems provide a simple solution to process large volumes – but are constrained to the denser materials, such as Magnetite in heating systems

A trend towards side stream filtration, where only a proportion of a closed system is processed, has allowed a more precise approach to filtration, using filter cartridges, bags and media systems.

Processing a smaller proportion of flow allows smaller connections to be used, simplifies retro-fit and significantly reduces energy input.

Effective filtration means that debris will be collected, so attention should be paid to how this will be managed. Fine cartridge systems can block quickly, and can lead to an intensive regime of inspection and replacement relying on site personnel.

Filter media systems allow a simple backwash process to clean and reuse the filter media. The process is readily automated and is a cost-effective alternative to a reliance on manual maintenance.

Select the best approach

The customer must consider whole life costs and risk minimisation. There are important questions to ask: Who will be carrying out the inspections, testing and re-dosing? How much of a limited maintenance resource can be diverted to this function? Would a contract with a water treatment specialist be a better option? Each option presents a long-term cost that will quickly outweigh any initial savings on minimal/basic dosing and filtration equipment.

A modern alternative is fully automated, self regulating technology requiring minimal on-site attention and with a low annual maintenance cost. Incorporation of modern BMS technology can alert the operator where attention is required, but otherwise can be left to manage itself.

James Townley is technical sales manager at ENWA Water Technology.

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