Podcast: Ray Field Discusses How to Prevent or Mitigate Legionella Outbreaks

Goodway_Ray_FieldRecently we discussed the unusual Legionella outbreaks hitting New York City. In this post, we dive deeper into Legionella Outbreaks to discuss preventative maintenance practices and chemical solutions that minimize risk.

Ray Field, the Director of Goodway Liquid Solutions, talks about Legionnaires’ disease and legionella bacteria, as it relates to cooling towers. He begins by stating that 40% to 60% of cooling towers, through different studies, have shown that they’re positive for legionella.


Benjamin: Hi Everyone, I’m Benjamin Hunting and I’m here today with Ray Field, the Director of Goodway Liquid Solutions. Today we’re talking about Legionnaires’ disease and legionella bacteria, as it relates to cooling towers. This is something that’s actually been in the news quite a lot lately because of the outbreak that happened in the South Bronx in New York City. Legionnaires’ is a serious disease caused by legionella bacteria, and legionella bacteria are typically found in stagnant, warm water. That’s part of the reason why we’re discussing cooling towers, because a majority of cases are directly linked to this type of technology. Ray, I was wondering if you could tell us why cooling towers, in particular, are so closely linked to Legionnaire’s disease outbreaks.

Ray: Sure, and I think that’s a good question. It’s not limited to cooling towers. There are other areas, evaporative condensers, even so much as showers or faucets. But in this particular situation, with the South Bronx, with the heat wave that came in, a lot of cooling systems are going to be operating at a very high load to maintain a cool environment in residential areas, hotels, and that type of thing. But anyhow, the legionella organism will hide out in slime layers in cooling towers. With those towers operating at that high load, you’re going to get mists and aerosolization of the tower water, and that’s going to contain the bacteria, and when it’s inhaled it can or will lead to legionellosis, which is a pretty serious disease.

The scary part of it is that 40% to 60% of cooling towers, through different studies, have shown that they’re positive for legionella. I think the conditions that happened in the South Bronx are conducive because of the high temperature, and the demand in cooling towers, that you had this localized aerosolization of water mist, and it carrying high levels of bacteria.

Benjamin: So, it’s the water mist itself – it’s not necessarily the water that’s in the cooling towers, but it’s when it aerosolizes and spreads in the general area of the tower that puts the population at risk?

Ray: Well, I would say that first, the organism hides out under slime. Actually, it will use other bacteria as a host and it is, as such, because it’s under biofilm layers, it’s somewhat resistant, we’ll say, to chlorine because it’s under the biofilm layer. It can’t be attacked by chlorine. When a tower is under a lot of load, you can get disruption of the slime layers with high continuous flow and water turbulence, and in that recirculating water, what happens is that the legionella basically gets released into the bulk water, and if you look at a tower, it’s like a controlled hurricane that’s happening on the inside of it, you get aerosolization. That type of mist, the fan is working very hard and yes, you get mist and droplets, if you will, that are sprayed. If there is insufficient disinfectant (for instance chlorine) in the tower water, the Legionella bacteria will remain alive there. Typically, towers are located on top of buildings, so the organism along with the misting will go to adjoining areas, and this can be as far as a mile.

Benjamin: So if you’re a building owner or a management company that is responsible for keeping a cooling tower clean, or just maintaining a cooling tower in general, what are some of the steps that you can take to minimize or eliminate the possibility of legionella bacteria causing a Legionnaires’ disease outbreak?

Ray: This is a topic that’s been addressed in a recent paper by ASHRAE, that’s the American Society of Heating, Refrigeration and Air Conditioning. But there are also prominent guidelines with the CDC, OSHA, EPA and other regulatory agencies. What it comes down to is good industrial hygienic practices, and if you look at cooling towers, in my estimation, they can be neglected in terms of care or maintenance up front when they’re started, in terms of washing them down, getting rid of scale accumulation in the tower fill that causes the air/water intimate contact in conjunction with the action of the cooling tower fan. Keeping the tower clean, and keeping the right biocide levels in the tower is crucial.

It seems that building management and others are under stress with respect to their maintenance budgets. Maintenance budgets are becoming reduced, which would lead to situations where you really don’t have the best equipment to clean towers up front, or water treatment contracts being reduced so it doesn’t enable to water treaters to do their job effectively. And that result is-, well, the Bronx kind of speaks for itself.

A major problem is that it is not going to go away. It’s not ‘if’ the next one is going to happen, it’s ‘when’ it’s going to happen. If you take a look at-, historically, go back to 2000, you’ll see cooling towers being implicated. Melbourne Australia, there was an outbreak of 125 people got sick. The fatality rate was only 4.2% in that case, but they’ve been a lot higher. It can be as high as 30%. In Spain, in 2001, that was the world’s largest outbreak. There were 800 people that were sickened, with 6 fatalities, with cooling towers suspected there as well. I could go through a lot of other case histories.

Believe it or not, in 2015, in the Bronx, in Co-op City, there were 12 people sickened in January 2015. I don’t know if it got that much notoriety, because we just had some sicknesses but no fatalities. But here, in the South Bronx, you’ve got greater than 100 people sickened, with 12 deaths, with several areas. Out of the 17 buildings with cooling towers, 5 tested positive for the disease. Including towers-, one of particular focus was the Old Opera House Hotel in the South Bronx, and considered the source of the outbreak, other facilities studied were Lincoln Hospital, and also the Concourse Plaza Hotel. It turned out that DNA of the Legionella bacteria in the Old Opera House Hotel matched DNA of Legionella in the lungs of victims, confirming the particular Legionella bacteria strain did come from The Old Opera House’s cooling tower.

Benjamin: Let’s talk about a worst case scenario like we had in the South Bronx. Let’s say that you are a building manager, building owner, what steps can you take once a legionella outbreak has occurred on your property? What do you have to do to contain that, and prevent people from getting sick?

Ray: At that point, you’re looking at an emergency disinfection procedure. You’re going to have to shut down cooling systems, fans. You’ve got to shut off water going to the tower. Building air intake vents in the vicinity of the tower must be closed. The cooling tower water is dosed with either chlorine or bromine, in very high concentrations and held up for 24 hours at very high concentration levels. You’re going to have maintenance personnel going in there, with the appropriate personal protection equipment so they don’t contract the disease while they’re doing an emergency disinfection. So, it can get pretty complicated.

What’s scary about it, again, is that the number is high as a 40%-60% prevalence of legionella found in cooling towers. There are certain OSHA guidelines for Legionella counts in cooling water. At or above a certain level, remedial action must be taken to address the levels. Note: It doesn’t mean there isn’t a risk of infection if the organism is found below an OSHA defined limit; it just means it is much less likely.

Benjamin: So, what you’re saying is you have to strictly monitor the level of legionella bacteria in your facility, just to ensure that you don’t reach a situation like we saw in the Bronx.

Ray: Typically what’s done – and there’s a correlation between the total bacteria count that’s in the tower, that you can do by a dip slide, if you have a microbial auger, you can tell the amount of –(of what is referred to as heterotrophic aerobic bacteria) – the higher that number, the higher the correlation is to the level of legionella that’s going to be existing under biofilm layers in that particular system. So that has to be kept under control. In most cases, Legionella is not tested for specifically, because that test will typically take several weeks to incubate to ascertain what the counts of legionella look like. The New York situation is different. With the new law that was just put in, it looks like you would probably be looking at total plate counts and specifically testing for legionella itself in cooling systems.

Benjamin: Well, Ray, I want to thank you for taking the time to speak with us today and helping people understand the link between cooling tower maintenance and preventing an outbreak of Legionnaires’ disease.

Ray: I just want to re-emphasize that it’s preventative maintenance, up front. Anything you can bring to bear, in terms of cleaning the cooling tower system up front with vacuums, pressure washers, getting the scale out of the fill. Both chemical and mechanical solutions are really the best way to approach it at first, followed by a well-maintained water treatment program.

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