The hot water loop contains charged membrane filtration cartridges for microbial retention.
Issues & Benefits
This 280,000-sq-ft office building is estimated to use 5.32 million gal of water per year. The particulate and charged membrane filtration microbial retention filtration cartridges each have an estimated life of six to 12 months. The source water for hot water and cooling tower has a capital cost of $9,000. With an annual operating cost of $7,500, the cost per gallon is $0.003. The hot water has a capital cost of $3,000. With an annual operating cost of $3,750, the cost per gallon is $0.0023. The hot water is estimated to comprise 30% of the building’s total water usage.
While this article is intended to focus on the solution and not the cause of microbial issues, it is important to review the internal and external factors affecting every home and business regarding the health of their premise plumbing. For more information on conditions that promote bacterial growth, consult the Occupational Safety and Health Administration’s (OSHA) Technical Manual Section III.
While domestic cold water typically is not associated with Legionella growth, it has been detected in cold water in icemakers and dental lines. This sometimes can be contributed to water temperature in the lines exceeding 68°F due to ambient temperatures in the premise plumbing and stagnant water or low-use distal sites. One cannot rule out cross-connection as well, which can quickly contaminate downstream plumbing.
While many end users, such as hospitals, nursing homes and other high-risk population facilities install 0.2-µ point-of-use (POU) filters for showers and sink taps, the problem is not always eliminated. Because these filters have lives of 30 to 70 days, the operating cost can exceed $1,200 per distal site per year. Also, chemical systems such as chlorine dioxide, mono-chloramine, chlorine, ozone and copper silver ionization typically only treat the hot water and tend to have high operating costs. They require specialized treatment firms to maintain the system, as well as state approval of the installation.
Until the conditions in the incoming cold water supply described in the OSHA manual discussed earlier are reduced, the hot water premise plumbing will continue to be exposed to microbial and sediment issues. There is a seemingly constant barrage of public water boil order advisory notices that are never issued before the problem is present. Protection before, during and after these advisories is a crucial proactive approach many will need to implement to protect their potable premise plumbing.
Construction projects and infrastructure issues can cause disruption to source water. Dirt, sediment and scale can break off piping due to construction and break biofilm loose. Infrastructure issues can go undetected for long periods of time before boil order alerts are issued. Proactive treatment can reduce the risk of Legionella and other opportunistic organisms.
This non-electric, non-chemical POE solution, which is capable of greater than 6 log removal value (LRV) of Legionella and other opportunistic organisms, greater than 4 LRV of viruses and greater than 5 LRV of protozoans, coupled with POU treatment for distal sites that continue to test positive, can provide the risk reduction that the public water systems cannot supply. It will reduce risk of Legionnaires’ disease and other respiratory illness to employees and customers, and protect their brand and image in the market.
