I was reading the Daily Mail on Saturday morning having got my cup of tea and streamed Brian Mathew’s Sounds of the 60s through the stereo system. I was expecting the usual Daily Mail shock horror drama stuff about disgruntled colonels upset about high speed train routes and Weston Super Mare warmer than Rome this weekend when Tuscany caught my eye. That’s in Italy I thought ( well it was early ) and I started to read the article about this poor lady :
Alethea Parker 51 (why do all newspaper do that ?) had a few days at a Tuscan countryside villa and took a shower . The villa like most in the countryside in Italy will have had a rainwater harvesting tank ( cisterna) and the water was contaminated with Legionella the bacteria that causes Legionnaires disease.
She returned home breathless and was soon in hospital fighting for her life. She lost both legs, one hand and three fingers on the other hand as doctors battled for 2 years to save her.
Hang on I thought didn’t I read that Legionnaires disease was caused by air conditioning units and cooling towers in large hospitals, hotels etc. Well it seems most of those theories have been debunked over the last couple of years and research now points towards stagnant water that is warmed to between 20C to 50C though the lower figure can be less.
Focus is now on rainwater harvested from roofs and then kept in storage tanks for longer than 20 days as one cause of the disease . This is especially true if there is no filter system that prevents leaves, debris, bird droppings etc entering the tank where the bacteria can then breed.
I am clearly out of date about this and had happily been thinking that my tank cleaned once a year was clearly no cooling tower nor an airconditioning system . So I did a little more research . How prevalent was the disease and found this from The U.S. National Institute of Health :
“A total of 214 rainwater samples from 82 tanks were collected in urban Southeast Queensland (SEQ) in Australia and analyzed for the presence and numbers of zoonotic bacterial and protozoal pathogens using binary PCR and quantitative PCR (qPCR). Quantitative microbial risk assessment (QMRA) analysis was used to quantify the risk of infection associated with the exposure to potential pathogens from roof-harvested rainwater used as potable or nonpotable water. Of the 214 samples tested, 10.7%, 9.8%, 5.6%, and 0.4% were positive for the Salmonella invA, Giardia lamblia β-giardin, Legionella pneumophila mip, and Campylobacter jejuni mapA genes, respectively. Cryptosporidium parvum oocyst wall protein (COWP) could not be detected. The estimated numbers of Salmonella, G. lamblia, and L. pneumophila organisms ranged from 6.5 × 101 to 3.8 × 102 cells, 0.6 × 10° to 3.6 × 10° cysts, and 6.0 × 101 to 1.7 × 102 cells per 1,000 ml of water, respectively.”
A little more research highlighted the fact that tanks must not be above ground and that many of the Australian ones are. This is because they heat up more than below ground tanks. However the other key factor is how long the water is held in the tank as well.
The UK has been busy while I have been in ignorant bliss on this as rainwater harvesting has over the past few years become big business there as water bills have soared. They have introduced BS standards on tanks and the requirement to have pre and post tank filters fitted. There is a regulation that governs the size of the tank that can be installed based on a formulae :
The BS 8515 2009 states that the capacity of the rain water harvesting storage tank must be the LEAST of either:
5% of the Annual Rainwater Yield (ARY)
5% of the Annual Rainwater Demand (ARD)
Demand is governed by the number of people living in the house and the size of the garden needed to be watered and an ongoing basis.
The formulae ensures that the tank is of a size that it will never have the same water in it for more than 20 days.
Rainfall (mm) x Building Footprint Area (m2) x 0.9 0r 0.8 (Tile Roof or Slate/Stone Roof) = ARY
ARY x 0.05 = 5% ARY
To calculate the Annual Rainwater Demand (ARD) use the following calculation:
No. of Residents x 16,000 = (1) Area of Garden (m2) to be watered (if any) x 60 = (2)
(1) +(2) = (3)
(3) x 0.05 = ARD
You are not allowed to instal a rain harvesting tank that is larger than the smaller of these two figures as the water will become stagnant and a breeding ground for bacteria, including Legionnaires Disease.
By now I was on a roll doing the research and had now discovered my 50,000 litre tank was way too big for me but also being a hypochondriac as well meant I was beginning to feel breathless though I had yet to have a shower nor check the temperature of the water in the tank. However my wife was now up and said “but we use bleach in our tank to kill bacteria”. Ah I thought and started to feel better.
However I then started to research bleach as an agent to kill Legionella. Bleach I found must be the sort that contains at least 4% chlorine so you must check the label to see that it does. There is a handy table on line that shows you how much bleach to use : 30,000 litre tank 3.75 litres of bleach for example. However chlorine is not a great killer of legionella according to research in Queensland again. Indeed it is considered fairly ineffective and the chlorine level in say drinking water will not do it hence the problems for hotels, factories, hospitals and the like .
The way to do it it is preventive with the filters already mentioned combined with a UV filter as the water leaves the storage tank rather than as it enters the house as it is the breathing in of the droplets that causes humans to contract the disease and you can do that outside the home when cleaning the car, spraying the patio or watering the flowers.
So I am off to buy a thermometer to test the water temperature. A swimming pool testing kit to test the water for chlorine levels ( there is another handy table on line) and a UV filter and a diver’s helmet with a pipe out of the window for me to breath while having a shower until the filter is fitted. Mind you I haven’t figured out how to wash my hair with it on yet though that hole in the top looks promising.
My final piece of research was to see how many cases were there in Italy and according to EuroSurveillance there were 3.4 cases per million inhabitants in 2000 and 16.6 per million by 2011 . 80% of these cases were contracted in the community where the people lived. Not a lot unless you’re one of the 16.6 .
Enough research though. I then squeezed some orange juice which reminded me of a nice piece of music I heard the other day by Delius who as a young man had a job picking oranges in Florida
Calms you down after all the scary stuff.