INFECTION PREVENTION AND CONTROL


Tackling knowledge gaps on hospital wastewater systems


In the second in a series of hospital wastewater-related articles running in HEJ this year (the first was published last month), Peter Orendecki, Senior Contracts manager and Water AP at University Hospital Southampton NHS Foundation Trust, highlights the apparent lack of understanding of the risks posed by hazardous bacteria in hospital waste systems among some designers, architects, and even infection control personnel. He asks whether there may here be an opportunity here for the UK to lead in such systems’ design.


The general design of effluent drainage within all buildings broadly relies on gravity to allow waste water from a number of different processes – including, but not limited to, handwashing, dish cleaning, showering, the use of toilets, macerators, bedpan washer-disinfectors, and other clinical uses, to drain away from the point of use into a vertical pipe, known as a stack. An individual stack receives all wastewater sources in its vicinity and all stacks link to the main sewer, effectively linking all drainage within a building. The lack of segregation of wastewater systems is a major factor in allowing microbes to move from one area of a hospital to another via different modes of transport, active growth, movement of air, and aerosols and the wastewater itself. At the proximal end of the drainage


system waste traps of various designs are used to hold water, thereby separating the drainage system air from the air in the local environment. This comes with its own issues. Bacteria dwell in the U-bend and form complex biofilms. Disposing of a carbon source down a sink drain will stimulate the growth of biofilm up the vertical section of the drain at a rate of 1 mm/hour, reaching the sieve at the top of the drain. Water from an outlet directly hitting the sieve can disperse organisms in the biofilm up to 2 m away. (see Figure 1).


Sanitaryware design and placement Sanitaryware designs and placement are of equal importance in reducing risk from wastewater systems. The risk in hospitals and other healthcare facilities is exacerbated by poor practices by staff, who are often unaware that the drainage poses a threat. The materials used within drainage systems tend to be mainly plastic in modern construction, and are often installed poorly, with incorrect fittings used, incorrect camber on pipework to effectively drain away the wastewater, and over-use of sealant, particularly around sanitaryware connections. In general, anything which impedes


Figure 1: Splashing from a basin reaches a distance of 2 metres – a phenomenon shown here using fluorescein dye.


drainage is likely to lead to dispersal of organisms within and outside of drainage systems. This may be due to incorrect sizing of pipework, incorrect camber, not employing swept bends, incorrect disposal of items (builders’ rubble, wipes, paper towels, etc), or inadequate maintenance (no planned preventative maintenance to ensure that drains are cleared, but instead only reactive work undertaken when it is too late). Ironically, the act of reactively unblocking drains can exacerbate problems. This may, for example, occur through the introduction of microorganisms on contaminated equipment, when using a water jet above a blockage, as a result of poor hygienic practices by Estates staff, and through a general lack of emphasis on appropriate procedures for storing, travelling with, and cleaning, drainage equipment.


Drain-dwelling bacteria entering the environment All of the above scenarios are likely to result in drain-dwelling bacteria entering the environment, and as antimicrobial


resistance (AMR) gains momentum, they will increasingly result in negative outcomes for patients. The ongoing operation of a healthcare facility and the building services within present complex and dynamic challenges, and to reduce risks such as the build-up and spread of hazardous bacteria in drainage systems on an ongoing basis requires appropriate training and discipline from staff, and appropriate communication with, and sensible practice from, patients and visitors. All of this also involves improving communication on the key issues to be aware of.


Depending on the size of the estate, the age of the system, and levels of reporting, the number of drain blockages occurring in a healthcare establishment can be in excess of 1000 / year (see Table 1). The criticality of a blocked drain in a healthcare environment isn’t widely understood, leading to both under- and late reporting of slowly draining sinks. Work conducted at UKHSA Porton Down has shown that sinks with a rear drain show minimal risk of transmission on wastewater organisms.


May 2023 Health Estate Journal 41


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