SANITARY SAFETY | PATHOGENS MANAGEMENT TRAIN SANITARY CHECK The pathogens management train has been developed to help identify the risk associated with pathogens in plumbing systems. The seven-stage concept is also designed to ensure sanitary safety in new public health designs, says Buro Happolds Ashveen Jeetun FCIBSE formation of bioaerosol from the water supply or sanitary drainage systems. Healthcare sector studies have shown that water inside drainage traps can become contaminated and released into the building through bioaerosol. The PMT identifies seven stages where considerations should be given: source; storage; distribution; use; traps; drainage; and recycling or outfall (see Figure 1). Stage one source Increasing sanitary safety is the aim of the PMT T he risks of disease transmission exist at all stages of the plumbing cycle, from connection to the water supply company (WSC) network to the final discharge or recycling. The pathogens management train (PMT) is an innovative, seven-stage concept that can be used to identify the risks associated with pathogens and to increase sanitary safety through careful design. It can also be used to evaluate existing systems to improve sanitary safety. The transmission of pathogens into the plumbing system can occur by ingress into the system from a contaminated environment, while cross-connection can also be a cause of contamination. Aerosol from odour traps, viral shedding in faecal matter, and/or backflow into the system are other ways that pathogens can be transmitted. Common transmission routes are inhalation, incidental ingestion, dermal contact, ocular, oral mucus membrane contact and faecal-oral. These can occur through direct or indirect contact with contaminated water from the sanitary drainage and/or water supply. Direct contact can happen when bathing, washing, or drinking contaminated water, while indirect contact occurs mainly through the Chlorine disinfection is the most common disinfection system. However, the chlorine is consumed in reaction with ammonia, and organic compounds may be deposited as a result of corrosion and biofilm on pipes inner walls. Water temperature is another factor that affects chlorine decay, so the free chlorine level in water supplied by WSC varies depending on geographical location. The suitability of the water quality from the WSC can only be assessed after approved chemical and microbiological testing. Water storage tanks are sized from half a days capacity to several days, depending on local codes, and the storage period affects bacterial growth in the tanks. The level and method of treatment upstream of the tank relies on the quality of water from the WSC, the period of storage, and temperature. CIBSE Guide G gives a comparison of appropriate disinfection technologies. Stage two storage Water tank storage size is typically based on number of days demand. In the UK, most tanks are sized at half-day consumption; however, the demand is not the same every day. A schools water storage tank will have more than half a day of reduced consumption over the weekend before normal consumption resumes. Formation of biofilm can occur during these periods. Planktonic cells can develop into sessile cells to attach to the surface of the tank. As colonies mature, detachment of planktonic cells occurs, to contaminate the installation downstream of the tank. The dimension of a storage tank is usually based on normal demand, but the storage volume of water can be adjusted to actual demand to prevent stagnation. The level can be controlled so that volume stored is based on actual consumption. Level sensors and controllers can be used with the BMS to automatically adjust the level of water based on consumption (see Figure 2). Stage three distribution Source Storage Distribution Use Traps Drainage Figure 1: Seven stages of the Pathogens Management Train (PMT) Outfall or recycling Aerosolisation occurs when the water in which the bacteria are growing is broken into microscopic water droplets. The emission strength of bioaerosol in high-pressure conditions is statistically greater than that in lower pressure conditions. Research on operation shows that pump sets operate at peak capacity for only 4.5% of the 62 October 2021 www.cibsejournal.com CIBSE Oct21 pp62-64 PMT.indd 62 24/09/2021 17:43