Onderzoek naar aanwezigheid van legionella in biologische luchtwassers bij stallen

In an earlier study it was concluded, based on literature and interviews, that biotrickling filters might be responsible for airborne transmission of Legionella bacteria. Risk factors in this type of systems are recirculating of trickling water with a pH close to neutral and the use of spray nozzles and fans. Under the right conditions, temperatures supportive for Legionella growth might be found in the scrubbing water. In order to investigate this risk, measurements were done at 36 animal houses where biotrickling filters were operated for exhaust air treatment. The investigation was performed in August and September because in several years the number of reports of Legionnaires’ disease significantly increased during this period in the Netherlands; during summer warming up of the water by ambient temperature is likely. In none of the samples Legionella was found. In only a few biotrickling filters the measured temperature was at such a level that growth of Legionella would be possible. It is concluded that it is unlikely that biotrickling filters at animal houses are a source of Legionella transmission to the air.