search.noResults

search.searching

dataCollection.invalidEmail
note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
INFECTION CONTROL


water providers use disinfection measures to ensure water is potable when departing the treatment plant, but the water will ‘pick up’ impurities from the distribution system piping. By the time gets to your facility, it most likely has impurities in it – including Legionella. This, alone, does not represent a significant risk, usually. However, dirt is ‘food’ for bacteria, and the amount of bacteria and dirt in the water will have a direct influence on how the water will age and how biofilm will develop within the building systems. It is important to note that some municipalities have relatively warm water running in their mains, over 80˚F in some cases. These conditions may increase the bacterial loading of the water service and impact facility decisions regarding supplemental disinfection or point-of- entry filtration. A facility regularly experiencing poor water quality should consider point-of-entry filtration – either by using stages of bag filters, mechanical screen filtration systems, on-site- generated supplemental disinfection, or a combination of these.


Legionella in domestic cold water systems While normally below the temperature range conducive to Legionella growth, domestic cold water systems can harbor and grow Legionella if the piping is uninsulated and routed near hot water piping – be it domestic or hydronic – especially in enclosed riser chases with little or no ventilation. Under these conditions, cold water can be warmed into the temperature range in which Legionella is more likely to grow. Ice machines served with only cold


water can also be a source of Legionella contamination. They often include carbon filters to improve the water taste, but they remove any residual disinfectant that may have been in the city water. These machines have compressors that can warm the water and grow bacteria that can then be inhaled by a patient chewing the ice. The once-dormant bacteria warm up in the lungs and become reactivated. Limit the risk by: limiting the amount of Legionella present in the entire water system, regular filter replacement, and flushing of ice machine supply lines.


Legionella in domestic hot water systems Legionella prefers warm water. Domestic hot water systems that are not uniformly ‘hot’ can provide ideal conditions for waterborne pathogen growth. Hot water systems typically include storage tanks, piped distribution systems, master temperature mixing valves, sensor faucets with point-of-use mixing valves, flow control devices within faucets, and water- hammer arrestors for quick-closing valves – such as some solenoid valves used with


54


Legionella poses a risk to vunerable patients.


sensor faucets. Patient showers include mixing valves, hoses for hand-held wands, and spray heads. These are all places where warm water and biofilm are conducive to Legionella growth – which can then be aerosolised near sick patients via faucets and showers. Water temperatures can widely vary within domestic hot water. Storage tanks are hopefully kept hot enough (140˚F or more) to prevent bacteria growth, but uncirculated storage tanks will allow stratification of temperature layers and can still be a source of a potential risk. Also, depending on local codes and anti- scald measures, hot water may have to leave the main heating equipment at 120˚F. Even with 24/7 circulating pumps, the highly dynamic demand flows and inherent difficulties of balancing complex hot water distribution systems can result in a temperature-variation free-for-all. To further add potential risk, many


fixtures may be infrequently-used and may be located at the end of a long, uncirculated branch pipe run. ‘Hot’ water in piping serving those fixtures will cool off and may spend much of the day in the perfect temperature range for Legionella growth. If the fixture in question is in an ICU patient room, the risk of life- threatening infection is much higher than if the fixture were in a non-patient area. (e.g. staff restroom where it is unlikely to be near sick patients). For a building engineer managing


these issues, checking the temperatures of the return lines and ensuring the system is balanced properly may be necessary. Replacing old balancing valves with new thermostatically-operated balancing valves can help ensure temperatures are being maintained in the supply piping. Providing faucets with programmable flush operation for seldom


used fixtures can aid in preventing stagnation. Also, having supplemental disinfection or copper/silver ionisation treatment for the hot water system can limit biofilm formation in the piping system.


Impact of water


conservation measures Due to increased environmental awareness, some water conservation measures have resulted in lower flows through pipes and faucets. Lower flows can result in increased ‘water age’ i.e. water is sitting in pipes for longer, and it is more likely to grow microorganisms. Also, lower flow rates are more conducive to biofilm growth. In some areas, handwashing fixture


flow rates have been reduced from 2.5 g/m to 0.35 g/m. If that fixture has a hands-free sensor faucet with a mixing valve, only half of that 0.35 g/m (0.18 g/m) would be coming from the hot water system when the faucet is activated. These low flows are fine if the piping system is sized accordingly and the volume of hot water in the pipe to the fixture is minimised. However, that is a very low flow for a


standard code-minimum, one-half inch diameter supply pipe. This can be a serious problem if an older facility is renovated with low-flow fixtures, but the existing distribution piping was designed for much higher flows. Point-of-use mixing valves at sensor


faucets may be weak links in potable water systems because their internal check valves may be fouled and cold water could be flowing into the hot water system – adding to the difficulty of maintaining hot water system temperature above the Legionella growth range. Building engineers need to ensure


IFHE DIGEST 2020


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106