The ‘safety’ of a fountain/water feature will ultimately be determined by the risk management process used to protect individuals from waterborne infection and potentially subsequent disease.
This ‘risk management process’ will inevitably differ between water features to help ensure that action taken is ‘proportionate to risk’. HSG 274 (Part 3) identifies the requirement for such water systems to be risk assessed and should the risk assessment identify a risk (or risks…) from exposure to Legionella bacteria then a written scheme should be drafted in respect of mitigating these Legionella risks.
Suitable and sufficient water risk assessments should therefore identify the following:
- The likelihood for aquatic microorganisms (Legionella bacteria) to propagate and proliferate the water system surveyed;
- The potential for an aerosol to be created whereby contaminated water droplets (with Legionella bacteria) may be inhaled;
- The vulnerability/susceptibility of those exposed to the risk.
Furthermore, the ‘likelihood’ for waterborne bacteria to grow and proliferate water systems will be determined by:
- The water source or supply;
- The temperature of the water;
- The presence of nutrients;
- The potential for slow moving or stagnant water.
…and how these risk factors are managed.
The ‘consequence’ of legionella risk will be determined by individual vulnerability/susceptibility – contingent upon immune system robustness of those exposed to water risk.
For water fountains/features; the source water may be fed from a managed mains supply in accordance with Water Regs (Quality and Fittings…) for delivering wholesome potable water. However, other water fountains/features may be situated within conservation areas (lakes/ponds) and subjected to frequent contamination from external sources (environment/wildlife).
Water management precautions may consider:
- The microbiological safety of water for those exposed to aerosolised water from these fountains;
- The microbiological impact to aquatic life.
This often necessitates suitable and sufficient ‘cleaning’ of these systems (and the use of specific chemistries) during recommissioning – to control the microbial load whilst increasing the available oxygen within these waters in support of aquatic life and a safe and sustainable water management approach.
Hydrogen peroxide can be used to disinfect contaminated water systems without posing a risk to aquatic life. This chemistry is indicated for use by the environment agency to increase available oxygen within contaminated waters (following chemical spills etc.) in order to protect/preserve aquatic life and a dry version of the same chemistry (sodium percarbonate) can also be used to deep clean drained fountain surfaces and therefore would be indicated for use offline. The hydrogen peroxide version can be used online (1-3% concentration – dependent upon volume of water treated) to control bacterial growth whilst protecting aquatic life.
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Editor’s Note: The information provided in this blog is correct at date of original publication – September 2021.
© Water Hygiene Centre 2021