… Did you know that Biofilm in any water system is a source of bacterial infection (legionella), a cause of corrosion and a cause of heat loss?
You probably did!
Fig.1 The five stages of biofilm development: (1) Initial attachment. (2) Irreversible attachment. (3) Maturation I. (4) Maturation II. (5) Dispersion. Each stage of development in the diagram is paired with a photomicrograph of a developing P.aeruginosa biofilm.
… But did you know that there is now a low cost way of online monitoring for the growth of biofilm?
You probably didn’t!
Biofilms (slime) can grow in any water system, but are more likely to grow in those systems that are humid, aerated, circulating and with a source of nutrients. When a biofilm grows it can create a very localised environment that may have very different conditions from the ‘bulk’ recirculating water. It is the ability of biofilms to form micro-environments that means that they are often associated with corrosion and scale formation. Biofilms are made up of free floating micro-organisms that weakly adhere (fix) themselves to a surface. If they aren’t immediately separated from the surface, they can bind more strongly to the surface, allowing further species to attach and colonize (grow) into a biofilm. This biofilm layer that develops is commonly referred to as ‘slime’ (Fig. 1).
Fig. 2 A lung infected with legionella. In 2011, there were 235 reported cases of Legionnaires disease in the UK.
Why do we need to monitor for biofilm?
What’s the problem?
Most water systems are very safe with no worrying levels of biofilm, so the actions taken by operators successfully mitigate the risk of developing biofilm, or control it to acceptable levels, so what’s the problem?
The problem is that whilst the vast majority of water systems are safe and well managed, we know that every year people die as a direct result of biofilms growing in managed water systems. Some monitoring regimes measure excess oxidant residual, and assume from a positive residual oxidant that the system is sterile. Biofilms, by producing a micro-environment can effectively protect bacteria from biocides in the water.
Currently there are no reliable, affordable and online real time monitors, that can check the efficacy of the chemical treatment used in preventing a biofilm build up, or to check that conditions haven’t changed since the chemical treatment regime was introduced, such as:
- A change of environmental temperature
- A change in water usage
- An air leak has introduced undesired materials e.g. oxygen and nutrients
What is current and state of the art?
There are various options currently available to measure the build up of biofilm. Probably the most successful is a device with a series of plastic plates. Every day/week/month a plate can be removed and checked for biofilm. Alternatively there are commercially available devices that measure the rate of heat loss from an online sensor, whilst effective false positives can be produced from a reduction in heat loss caused by a build up of sediment or scale.
Fig. 3 A BioSense sensor
What’s the solution?
The solution to the current issues associated with biofilm growth and chemical overdosing is to continually monitor with an easy to use, affordable biofilm monitor. This monitor should be:
The BioSense from Pi meets all these criteria (Fig. 3).