Cooling towers
Cooling towers have the ability to spread Legionella over a wide area and consequently are often regarded as one of the most dangerous and hence most regulated of sectors in water treatment and Legionella control. The UK L8 regulations are discussed at some length elsewhere.
The UK regulations recommend culture testing on a quarterly basis as a minimum. However, these regulations also stipulate that owners are ultimately responsible and must take an active role in managing and monitorring the control of Legionella within the system. From a legal, and indeed from a corporate governance position, it is not sufficient to hire a water management company and then rely on their best efforts. The facility owner has to be sure that all reasonable practical control measures are being taken, not just that the minimum requirements are being fulfilled. The hydrosense test has a role in providing system owners and managers with timely relevant information about immediate Legionella risk.
In practice even the best managed water systems can be subject to failures and cannot guarantee Legionella control simply by chemical dosing and testing. The operating characteristics of wet cooling systems is such that nutrient ingress, appropriate temperatures for bacterial growth, large surface areas which can support biofilm and low flow areas or periodic poor circulation are almost inevitable.
Control
Controlling Legionella is the most important objective, but be very wary of advice that your system is always controlled. As we explain monitoring is essential to demonstrate how well your control is performing and as such is an important part of the overall control system. When loss of control starts to develop, e.g. inadequate biocide dosing, general microbial buildup (e.g. high dipslide or ATP result) – Legionella can grow rapidly, potentially amplifying thousands of times every day. Such events are entirely forseable, and your Legionella management plan should identify the steps to be taken in the event of initial loss of control. We suggest daily testing of operational cooling towers with a rapid Legionella test until control is restored, followed by weekly testing until the next laboratory result also reports a negative result. Monthly testing would then be advised until all systems have been operating effectively for some time. Your plan should identify the action to take in the event that any of these results are positive. We would recommend immediate remedial action, with consideration given to closing down colonized systems. In all cases you should review your risk assessments and testing frequency; you should also consider neighbouring systems under your control which may become cross contaminated.
Monitoring
The Hydrosense test provides an excellent way to monitor the effectiveness of a control system. Hydrosense provides fast results on site, without expert assistance, so it is simple to check between regulatory quarterly checks. If there is a problem, it is immediately identified and remedial action can be taken – protecting clients, staff and the public. This protects your business from public liability claims and your reputation.
Cooling tower pack
Cooling towers have a specific problem with the cooling tower packs. Bio-film builds up on the cooling surfaces. These are great places for Legionella to grow.
Under normal working procedures these packs have to be removed and disinfected biannually. The Hydrosense bio-film kit is a useful tool required to monitor the state of the cooling tower packs in situ, both before and after treatment, thus saving considerable amounts on money in unnecessary down time. Where pack removal is not possible, regular Hydrosense testing can provide an additional measure to monitor and manage Legionella risk as recommended by the L8 Guidance.
Responding to problems
Further once a problem has been identified and dealt with, it is possible to check the efficacy of the remedial action quickly. This provides the confidence and the data on which to restart operations. Why wait 10-14 days for lab results?
Specific advice
We can’t provide specific advice or risk assessment for your specific system but are happy to discuss how rapid Legionella testing could enhance your risk management programme.