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