Healthcare Built-in water hygiene
Keeping HVAC equipment bacteria free Water hygiene is not just about Legionnaire’s Disease; bacteria in water can cause considerable problems for HVAC equipment, blocking pipework and stopping systems from running efficiently. Preventing this situation requires a considered approach from a building’s conception through to its ongoing running and maintenance. Steven Booth explains the importance of built-in water hygiene
Biocides can lead to corrosion in HVAC equipment
WATER RUNS through the ‘veins’ of all of our buildings, essential for drinking and also instrumental in the operation of HVAC systems, providing heating and cooling. The risk this water poses to human health is well documented, with outbreaks of legionella usually making headline news. Less talked about is its effect on building oper- ations. Unhygienic water in a closed circuit heating system may pose little harm to people, but with bacteria such as Pseudomonas causing contamination, poor water treatment will result in inefficient operations, shortened plant life and breakdowns. Keeping water clean and bacteria free must be consid- ered at the design stage and while there are standards in place to pre- vent bacterial contamination they don’t always go far enough.
Short-term view
What’s important to building designers, specifiers and contrac- tors is that a building is ‘safe’ at handover, with little consideration about how water systems function months or years down the line. The focus is usually on cost and energy savings, but products that seem to meet this remit short term, often fall short over a longer period of time. Whole-life costing is essential. ‘Value engineering’ and its sup- posedly cost-effective ‘fit-and-for- get’ water treatment solutions is a problem we see time and again. One example is magnetic water conditioning, favoured for its low energy and low maintenance cre- dentials. Lime-scale formation is not controlled throughout the entire water system as effectively as with traditional salt-based water soften- ers, however.
Supplementary treatment devices often end up being turned off, or break down due to lack of maintenance. This is also true of rainwater harvesting systems, installed to meet green targets.
Guardian Water Treatment’s Wallenius AOT, a non-chemical water treatment
Cause and effect With water hygiene issues not always being immediately appar- ent, it is essential building design- ers have an understanding of the effect of their choices. For exam- ple, dead legs and capped pipes, which may be installed to allow for system expansion, should be avoided where possible to prevent stagnation. If unavoidable, they must be flushed out regularly. When it comes to positioning water systems within a building, lower use outlets should be installed upstream of frequently used ones – i.e. a seldom used shower installed upstream of a fre- quently used toilet.
Dangerous trends
A current trend is for every tap in a modern building to be fitted with a Thermostatic Mixing Valve (TMV) – this doesn’t match with the HSE guidance on legionella control, and in some case increas- es the risks of bacterial prolifera- tion. TMVs should really only be used where vulnerable people are likely to use the facilities; in hos- pitals and schools, for example. Low flow taps, while great for the environment, allow water to stagnate, creating the right condi-
18 | May 2016 | Healthcare supplement to HVR
tions for legionella to grow. It might seem that good water hygiene is at odds with sustain- ability, this needn’t be the case; rather than do away with water saving, by being aware of poten- tial problems, ongoing water sys- tem maintenance and treatment can be tailored accordingly. Regularly running water through all outlets is important particularly where tenanted properties may lie empty for weeks at a time. Non-chemical water treatments, which harness a specific frequency of light and photocatalytic surfaces to create free radicals that break down harmful micro-organisms, are extremely low energy and allow buildings to cut down their reliance on chemicals, vastly improving water hygiene’s ‘green’ credentials.
The right approach
The best approach to water hygiene is a bespoke one that begins at construction with good water system design, and is com- bined with considered on-going water treatment choices, for example, automated dosing based on actual water conditions, rather than just throwing in chemicals, regardless of the necessity. Non-chemical alternatives to water treatment can work well in
closed-circuit water systems, put- ting paid to the problems encoun- tered with traditional filling and pressure testing of closed systems with biocide treated water. By doing away with chemicals, oper- atives don’t come into contact with harmful substances. Biocides are watered down to reduce their propensity for harm, which can lead to ineffective bacterial con- trol. Air testing, which is some- times used as an alternative, also comes with its own health and safety issues.
Biocides themselves can also cause corrosion; bromine, often used in cooling towers, is one such example. By cutting down their usage, equipment longevity can also be improved.
Easy maintenance
A key part of good water system design is the facilitation of appro- priate maintenance. All parts of the system must be easy to access, with isolation valves included to implement control measures. Remote monitoring will allow water treatment to be based on the real scenario, rather than a ‘one-size-fits-all’ approach which can lead to over use of chemicals. It may lack the glamour of the more visible parts of building, but water’s extremely important – keeping it clean and fit for pur- pose is essential for human health and successful HVAC operation. Guardian Water Treatment pro- vides water system legionella pre- vention services at the construc- tion stage as well as ongoing treat- ment and maintenance. Its non- chemical alternative to water treat- ment, Wallenius Advanced Oxidation Technology (AOT) is a safe and cost-effective option for controlling bacterial growth, min- imising environmental impact by reducing chemical usage. • Steven Booth is an associate director at Guardian Water Treatment
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