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Biofilms And Their Impact On Water Plant Management This issue, Robbie Phillips and Richard Lamburn, STA’s Technical Pool Plant Team look at Biofilms – what they are, how they occur and how to prevent and control them


iofilms are organic ecosystems that play a very important role in the provision of hygienic conditions for all water-based systems. Simply put, if they are not prevented from infecting these systems they can rapidly develop into high-risk unhygienic colonies, resulting in huge numbers of bacteria growing inside the system. The risk, if left uncontrolled, is the potential to infect exposed bathers in our leisure provisions i.e. swimming pools, spas and interactive play features.

SO WHAT’S NEEDED TO START A BIOFILM? Generally, all you need is a suitable surface submerged in water (or some other aqueous solution) microorganisms and favourable conditions. However, it’s not quite that simple though. Not all biofilms grow at the same rate or even require similar conditions to survive – each type of microbe has its own needs. Still, there are some factors that can affect biofilm attachment and growth regardless of species: • The availability of nutrients in the water sample, body fats, skin particles, phosphates (from pool and spa chemicals) and general organic contamination. • The physical and chemical characteristics of the surface(s) e.g. pipe material, sand grains, balance tank and overflow channel surfaces, filters and stagnant water in these items. • Incorrect pH levels. • Temperature. • The rate of water flow, in the sample i.e. poor hydraulics in the pool, spa etc. • Incorrect levels of disinfectants in the water at any time – chlorine, ozone, bromine, UV etc.

Biofilm formation on dehumidifier fins

• The number of species of organisms in the water. • If the microorganisms can move on their own. • Hidden areas, where often due to lack of maintenance and/or lack of effective cleansing the biofilm establishes. Sand filters are perfect and it is one of the main reasons why they should be inspected and tested regularly. Ultimately, it’s essential to understand that microorganisms don’t necessarily ‘think’ while forming a biofilm; it just happens if the conditions are favourable. If a microbe is pushed by water flow or accidentally bumps into a surface, it may or may not attach the first time or even at all for that matter. It’s unclear what causes a cell to attach to a surface and some researchers say it’s a combination of factors – flows (including shear rates), electrostatic forces, conditioning layers (debris already on the surface) and nutrients available to the microorganism. The establishment of biofilms in the wet leisure sector is relatively easy to identify with a number of indicators and signs of biofilm growth:

It’s unclear what causes a cell to attach to a surface and some researchers say it’s a combination of factors – flows (including shear rates), electrostatic forces, conditioning layers (debris already on the surface) and nutrients available to the microorganism” 47_SPN_Apr_16_STA.indd 47

Dirty spa balance tank with ideal surfaces for growth

• Combined chlorine odours during water agitation – e.g. swim squad activity. • Cloudy water. • Areas of filter surface inactivity identified as ‘dead spots/areas’ during recommended filter inspection. • Musty smells around the system plant and balance tanks. • Little control and low free chlorine (also disinfectant) levels. • Slimy gel like deposits on surfaces or detection of the same in water samples. The prevention and control of biofilms within the wet leisure sector is essential and should consist of: • Regular inspections of balance tanks, filters, surface draw off components and grids. • Regular maintenance of these areas. • For intensely bathed facilities, e.g. unit spas, interactive play feature systems (with their own dedicated purification systems) consider super chlorination with scrubbing. • Regular chemical and bacterial testing and prescribed interpretations with reactions. • Addressing identified infections by indicator organisms, Pseudomonas aeruginosa for example. STA 01922 645097 The cause of Legionella infections is primarily initiated from a biofilm where infective microorganisms are developed in a biofilm then released as a parasite within a host bacterium which in turn is killed only to release the harmful agent.

SPN April 2016 47 21/03/2016 16:49

SPN (Swimming Pool News) April 2016  

Informing the pool and spa industry since 1959. Covering the UK's wet leisure market, SPN (Swimming Pool News) is the UK's longest running a...

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