The effectiveness of disinfection and flushing procedures to prevent coliform persistence in aircraft water systems.

A full-scale reproduction of an aircraft drinking water system was conditioned using municipal tap water with a mixture of free chlorine and chloramines, and subsequently contaminated with coliforms. Disinfection was undertaken using chlorine dioxide, ozone and a mixed oxidant solution followed by flushing until no disinfectant residual remained. Results showed that coliforms were not persistent on the aircraft plumbing surfaces, and coliforms were not detected after disinfection and flushing with any disinfectant. The one exception was the aerator installed in the lavatory faucet, which was coliform positive after disinfection with ozone and mixed oxidants. These data suggest that the faucet aerators could be a source of coliform contamination that may result in coliform positive samples. Further experiments conducted on disinfection of aerators with glycolic acid and quaternary ammonia (both commonly used by the airlines) showed no detectable coliforms on coliform contaminated aerators after 30 minutes of soaking in the disinfectants.