HEALTH AND SANITATION
23
Legionella : point-of-use filtration
Photo by www . yourhealthdefenders . com
Point-of-use ( POU ) filtration is defined as the use of a device applied to a single tap for the purpose of reducing contaminants in drinking water at that one tap .
By Environmental Protection Agency , document EPA 810-R-16-001
POU filtration can be used at specific taps and shower heads as a temporary measure to provide a physical barrier against legionella . Hospitals have used this technology to try to reduce disease transmission .
POTENTIAL WATER QUALITY ISSUES POU filters have the potential to concentrate bacteria and foster growth of pathogens , especially if devices are not properly maintained . Failure of filters could lead to the release of high levels of pathogens . Membranes may foul or be degraded by microorganisms .
OPERATIONAL CONDITIONS In general , most POU devices include pre-filtration ( usually granular activated carbon ) to treat inlet water and prevent clogging of the central membrane , the central filtration membrane and post-filtration , in a module configuration . Design guidance for POU filtration devices can be found in EPA ’ s Membrane Filtration Guidance Manual ( USEPA , 2005c ).
Facility owners and operators are advised to follow the manufacturer ’ s operational guidance for the POU system being employed . There is a variety of commercially available systems with unique design features and operational conditions . Additional guidance on operation and maintenance for POU treatment devices , including examples of maintenance logs , can be found in EPA ’ s Point-of-Use or Pointof-Entry Treatment Options for Small Drinking Water Systems ( USEPA , 2006d ). A detailed maintenance log should be kept for each system , based on the state ’ s requirements , if any . Maintenance typically includes the following :
• Tracking flows : Flow meters are used to measure the total flow treated , as flow values may be used to determine filter membrane or other component replacement parameters .
• Replacement parts : Components should be replaced as required by the manufacturer or monitoring data , to ensure water free of microbial contaminants . Minimal components needing regular replacement include exhausted membranes and pre- and post-filters . A 30-day replacement rate was reported in the studies using POU filters for legionella control in hospitals .
• Visual check of mechanical conditions : All components , including the mechanical warning device , should be inspected visually on a regular basis and parts replaced / repaired if necessary , in addition to being replaced as specified by the routine replacement schedule . PA
Failure in maintenance of device filters could lead to the release of high levels of pathogens .
www . plumbingafrica . co . za May 2018 Volume 24 I Number 3