4.13.2 Rigs B The temperatures in rigs B were maintained below 45ºC, simulating a typical hot water circulating system in which mixing valves are used to blend water to a temperature below 45ºC to avoid scalding. This was effectively the rig in this ‘control’ set of experiments. The temperatures of the polyethylene rig tank recorded daily for 83 days ranged from 36ºC to 49ºC. The most common temperature recorded was 45ºC. The average temperature in the polyethylene rig tank recorded over the 83 days was 43ºC (± 0.4ºC). Graph 4.39 shows the results of samples taken ones a week from the Legionella polyethylene rig draw off point. 160000 140000 B 120000 rig 100000 80000 polyethylene - 60000 CFU/l 40000 Legionella 20000 0 0 13 20 27 34 41 48 55 62 69 76 83 Days in rig Graph 4.39 results of polyethylene rig B. Legionella At day 0 a colony forming unit count of 49500CFU/l was found in the Legionella sample taken from the draw off point of the polyethylene rig. The Legionella contamination was variable but increased to a colony forming unit count of Legionella 60800CFU/l found in the sample taken on day 83 (~ 23% increase).The average count of samples taken from day 13 to day 83 was 64309CFU/l (± Legionella 10421CFU/l). Page 175 of 229
4.13.2 Rigs B The temperatures in rigs B were maintained below 45ºC, simulating a typical hot water circulating system in which mixing valves are used to blend water to a temperature below 45ºC to avoid scalding. This was effectively the ‘control’ rig in this set of experiments. The temperatures of the polyethylene rig tank recorded daily for 83 days ranged from 36ºC to 49ºC. The most common temperature recorded was 45ºC. The average temperature in the polyethylene rig tank recorded over the 83 days was 43ºC (± 0.4ºC). Graph 4.39 shows the Legionella results of samples taken ones a week from the polyethylene rig draw off point. 160000 rig B 140000 120000 polyethylene 100000 80000 CFU/l - 60000 Legionella 40000 20000 0 0 13 20 27 34 41 48 55 62 69 76 83 Days in rig Graph 4.39 Legionella results of polyethylene rig B. At day 0 a Legionella colony forming unit count of 49500CFU/l was found in the sample taken from the draw off point of the polyethylene rig. The Legionella contamination was variable but increased to a Legionella colony forming unit count of 60800CFU/l found in the sample taken on day 83 (~ 23% increase).The average Legionella count of samples taken from day 13 to day 83 was 64309CFU/l (± 10421CFU/l). Page 175 of 229
Birgitta-Bedford-Thesis-2012.docx