Application of the INWATROL L.nella+ for fully automated legionella determination (Part 2)

Our INWATROL L.Nella+ has been on the market for several years now and has already helped many of our customers to ensure hygienically correct operation.

Measuring method of the INWATROL L.Nella+

The INWATROL L.Nella+ is based on a patented method that reliably measures the metabolic activity of living cells with the parameter Legionella spp. from a water sample within a few hours. This method has a high correlation with the ISO 11731-2017 cultivation method. However, a fundamental difference is the time required for the different measurements. While the measurement with the cultivation method takes between seven and twelve days, the INWATROL L.Nella+ can provide a reliable measurement of the legionella concentration within a few hours. The measurement can either take water samples automatically when connected directly to the cooling system or a water sample can be added manually, in which the concentration of legionella is then also measured automatically. This offers operators of evaporative cooling systems, cooling towers and wet separators a decisive advantage: a continuous overview of the legionella concentration and its trend in almost real time. In the event of an increased legionella concentration, the operator can take immediate action to reduce the concentration of legionella or alternatively use the automated control functions without having to intervene (e.g. automatically adjusting the biocide dosage and/or increasing the water exchange).

Further development of the device
Over the many years of use, the INWATEC team has worked on the further development of the INWATROL L.Nella+. The INWATROL L.Nella+ now offers even more advantages in use. It is now also able to monitor defined cooling water parameters. These include the chlorine content, the redox potential, the conductivity and the pH value. All these parameters can also be actively controlled (control function similar to cooling water controllers) and, like the results of the legionella measurements, can be visualized 24/7 in the “INWAnet” online portal. If required, the device can now also dose the biocide used automatically and as required when connected to a chemical supply. With the help of the close-meshed measurement of the legionella concentration several times a day, a moving average of the concentration is formed, which is used as the basis for biocide dosing or further manual and/or automated measures.

Depending on the operating conditions, the concentration of legionella in the individual measurements sometimes fluctuates greatly, as bacteria are inhomogeneously distributed particles in technical circulation water systems. This is often also a weak point in the evaluation of the few (monthly, quarterly) laboratory tests using the cultivation method according to UBA. With INWATROL L.nella+, the frequency of measurement means that findings that deviate significantly upwards or downwards are smoothed by calculating a moving average (e.g. over 10 measurements in succession) in order to react reliably to trends and avoid starting process chains based on individual, conspicuous findings.

It is important to always dose as little as possible, but as much as necessary. On the one hand, this corresponds to needs-based dosing and, on the other hand, ensures the minimization requirement for the use of biocides. Based on the trend in the concentration of legionella, additionally installed sensors (e.g. redox and/or chlorine sensors) can be used to control not only the general triggering of biocide dosing but also the concentration of active substances and the exposure time as required. The INWATROL L.Nella+ is therefore even simpler and more practical to use and to control legionella in cooling water and also performs the additional functions of a cooling water controller: 2 in 1!

Application examples
The INWATROL L.nella+ is used in various practical applications. Examples include operation in the following systems:

Monitoring the drinking water network at a beverage manufacturer

Challenge for the measuring operation:

• Reliable detection of low and increasing concentrations of legionella with changing drinking water temperatures in the pipe network
• Suppression of the influence of VBNC cells on the measurement results, especially at low water temperatures

With this characteristically nutrient-poor and solids-free water, fluctuating loads of Legionella could be reliably detected over several months, depending on the sampling structure and temperatures in the pipe network.

Hygienic monitoring of various cooling systems of a food manufacturer using a laboratory device

A challenge for measuring operations:

• Manual sample feeding of qualitatively different cooling water
• Disinfection of the feed funnel before sample preparation
• Ensuring a low workload for manual samples including evaluation of results

Reliable, automated setting of the parameters for pre-treatment in the device was ensured over several months, even with differently buffered and pre-contaminated water samples. Both drinking water samples (monitoring of the make-up water for the cooling systems) and the cooling water samples showed a good correlation to the cultivation method according to UBA with significantly different results.

The INWATROL L.Nella+ is offered for hire by INWATEC. For an offer or questions about our measuring device for fully automated legionella determination, please contact us via our contact form.