Awareness of potential sources of contamination from drainage systems within the field of 'Public Health Engineering

Les Wilson

If Public Health is defined as “the art and science of preventing disease, prolonging life and promoting health through the organised efforts of society” (Acheson, 1988; WHO), then 'Public Health Engineering/Hydraulics' plays an important role within building services in achieving this. Our discipline is primarily concerned with providing wholesome water to draw-off points and ensuring the safe passage of waste products, through habitable and non-habitable spaces away and from the building envelope to the boundary connection.

Research and simulation has proved that drainage flows through a building are in a state of flux, flipping between the states of steady flow (where fluid properties at a point in the system, do not change over time) and unsteady state flow transients (time dependent). The two states are intricately linked to flow discharge and the design dynamics of the pipework system. Hydraulic disturbances within drainage systems create turbulence leading to rapid negative and positive pressure transients within branches and stacks.

Right up to the beginning of the 1900's, there was as sector of the population who still held on to the 'Miasma theory', believing that epidemic diseases were spread by poisonous vapours in the air. In May 1894, Dr. Abraham Jacobi, addressed fellow physicians and scientists with the words “There is a general vague impression among the public [regarding sewer gas], but I never saw a case or could prove one”... and there he began to question the veracity of the sewer gas theory. The following year at the ‘Congress of American Physicians and Surgeons’ he brought to his audience, the world of microorganisms and the science of bacteriology that sat outside sensory smell or sight.

Dr. F.W. Andrewes was the Medical Officer of Health of the Local Government Board in England between 1906 and 1908. He submitted a paper on 'micro-organisms in sewer air' based on his own research and observations. In

one of his experiments, b. prodigiosus (a red microbial growth formation found on starchy foods) was poured down a water closet 60 feet above ground level and repeatedly flushed. At the same time all the available sink taps were opened to induce as much splashing as possible at the foot of the stack, which in turn discharged into an inspection chamber. No fewer than 1500 colonies of b. prodigiosus were counted on the suspended plate located within the inspection chamber.

Andrewes in a later experiment acquired the use of a private house and selected a water closet on the ground floor from where he introduced the bacteria B. prodigiosus. Although the splashing effect was considerably less, he was still able to collect via a plate placed in an inspection chamber 15 feet beyond the foot of the stack, 92 colonies of B. prodigiosus.

Professor C-E. A. Winslow was a bacteriologist serving on the faculty of the Massachusetts Institute of Technology (MIT). In 1907, he received a request from the National Association of Master Plumbers to investigate the perceived discrepancies around the sewer gas and report his findings. The result of Winslow's understanding of bacteriology lent credence to his opinion that it was individuals infected with pathogenic microbes that were the source for spreading diseases and not sewer gases.

Major William Heaton Horrocks served as sanitary officer at the British colony of Gibraltar and undertook a series of drainage experiments and in 1907 and published his findings in the proceedings of the Royal Society in London. His report contained his explanations relating to the release of bio aerosols due to turbulence and splashing.

The great minds of Jacobi, Andrewes, Winslow, Horrocks, Delepine and others through experimentation in Europe and America were able to show the correlation between splashing and foaming and the release of airborne bacteria via aerosols. Their experiments also demonstrated how bacteria from one drain could be transferred to another on air currents via the drainage system.

Trap water seals provide a barrier and are designed to withstand pressure variations of ±375 N/m2 (37mm water gauge). Should Excessive pressure transients due to poor design, poor installation, poor maintenance or simply overloading of the drainage system occur, there is an inherent risk of breaking through and destroying protective water seals leading to crosscontamination.

The development of network simulation model AIRNET under the guidance of the late Professor John Swaffield and his team at Heriot Watt University used advanced mathematical computations to simulate 'unsteady state' water and entrained airflows within drainage systems built upon pressure surge analysis.

AIRNET has also been used as a diagnostic tool for the investigation of suspected cross-contamination resulting from the failure of water seal conditions, including system surcharge and trap depletion. It played a part in the forensic investigation in the 2003 SARS outbreak at the Amoy Gardens housing complex in Hong Kong.

One of the earliest and most effective methods of containing communicable diseases was and still is - isolation. Poorly designed, maintained and overloaded drainage systems, contribute to the potential breaching of this isolation. Drainage systems are reliant on water seals that unfortunately, are vulnerable for a number of reasons - including wind shear, evaporation, capillary action, back pressure, induced and self-siphonage. Amoy Gardens in Hong Kong has become synonymous following the 2003 SARS outbreak when the release of microbial aerosols escaped via a dry trap resulting in 42 fatalities.

The photo below shows a WC seal affected by wind shear. The WC pan is close to losing it seal and was one of three connected to a drainage stack system. It was closest to the stack and therefore the most reactive to the negative pressure caused by wind driven oscillations.

This phenomenon is mitigated by placing the vent terminal away from direct exposure of known wind directions. The inclusion of the vent cowl further acts as a deflective buffer.

The environment in which a drainage system serves influences the design process. Healthcare facilities, airports and other busy travel hubs have the potential to significantly increase health risks with the latter supporting a transient population. This calls for comprehensive assessments to identify options in which to meet the defined service levels. Codes and

Figure 1

standards do not provide guidance for all situations and environments.

Protecting the health of building occupants is the ultimate goal of any sanitation system. Primary paths leading to contamination within the built environment include ingestion or direct exposure. Secondary routes may include physical contact with contaminated surfaces or inhalation of aerosols.

PVC, polyethylene and polybutylene materials represent the greater part of all materials used in drainage systems. They can be susceptible to the physicochemical phenomenon of permeation and leaching processes. For example, mould and fungus contaminants may be removed from the internal surface, but thereafter the material will retain its status of a permeable medium.

Mould is a fungus and can be classified as either being a) allergenic, b) pathogenic or c) toxigenic. They come in many forms and can be responsible for asthma like respiratory diseases to severe chronic conditions. Exposure to mycotoxins in extreme cases can lead to liver and kidney conditions, pulmonary bleeding and pulmonary fibrosis (scarring of the lungs). People suffering with existing lung diseases are more at risk. Moulds thrive in wet, humid or damp conditions

Materials utilised at the lower end of the plumbing market such as the PVC basin waste grating in the photos below, are less hardy and are more prone to damage opposed to chrome metal waste gratings. Striations formed by gritty particles adhering to the plug inside the mouth of the grating have provided a suitable host for moulds and mildew to multiply.

The photos in figure 1 were taken over a four-week period and show how given the right conditions, the mould slowly forms in the striations and around the waste seating. Normal cleaning using commercial bathroom products on a weekly basis have little effect on the mold.

The moulds in appearance, are consistent with 'Ulocladium' and 'Alternaria', both are common to wet areas associated with bathrooms and kitchens. People suffering from allergies such as hayfever or asthma -like symptoms will be more susceptible to the mold ulocladium, whereas alternaria primarily causes asthma -like symptoms in the upper respiratory tract, nose and mouth.

Whilst other forms of fungi can support a diverse spectrum of toxigenic microorganisms, microbiologists studying the prevalence of the fungal related biofilms within plumbing systems have identified 'fusarium' from sink traps as one source. The widespread distribution of certain fusarium species in drains suggests that they are particularly well adapted to this environmental niche. Fusarium biofilm growth may also facilitate infection of humans and have been identified with mycotic keratitis, which causes 'inflammation of the eye's cornea'.

Access inspection openings are required to gain entry into drainage pipes to either remove blockages, allow for scouring or simply to facilitate a CCTV condition assessment when needed. Like a compromised trap seal, access points can provide a path of contamination by allowing the release of microbial aerosols into habitable areas.

Healthcare facility drainage systems can present problems in terms of access. Hospital drainage systems are notoriously prone to blockages from the foreign objects. To add to this problem, sanitary fixtures outlet points are often needed in isolation leading to

extended branch runs. Patients who may be carriers of infectious diseases pose an additional health risk. Therefore, where and how a drain is accessed in terms of keeping the facility operating has to be evaluated against infection control processes, whilst an effort should made to limit drainage pipes routes to within dedicated service areas.

Hydraulic disturbances caused by the flows from flushing of toilets, urinals and sink hoppers, wastewater from baths, basins, sinks and showers and other fixtures generate splashing, which in turn creates turbulence. This leads to rapid exchanges negative and positive pressure transients within branches and stacks. Pressure transients developed in stack flows in excess of 2.0 L/s have the potential to generate 50 mm water gauge.

When one considers the depth of a WC trap that is protected by a 50mm water seal, this rather explains the vulnerability of traps and how they can be compromised.

In worse case scenerios, building occupants can be exposed to human waste pathogens due to a number of causes a) poorly designed drainage system, b) poorly installed drainage system c) poorly maintained drainage system and d) overloading of a drainage system.

Raw sewage contains disease-causing pathogens, including viruses, bacteria, worms, and protozoa. Healthy human waste contains nitrogen, oxygen, carbon dioxide, hydrogen, methane ammonia, and hydrogen sulphide. Whilst the first five are odourless, hydrogen sulphide is a toxic gas produced by sulphate-reducing bacteria in the human gut and smells like rotten eggs. A by-product of urea (itself a by-product of urine) is ammonia, which has a pungent smell - add to this the chemical cocktail mix of soaps, shampoos and cleaning agents and it's not surprising that a dysfunctional drainage system emanates foul odours.

Bacteria: A bacterium is a single, but complex, cell. It can survive on its own, inside or outside the body.

Viruses are smaller than bacteria and are not cells. Unlike bacteria, they need a human or animal host to multiply. They cause infections by entering and multiplying inside the host’s healthy cell. Viruses are parasitical organisms and are often the cause of respiratory illnesses, from the common cold to Covid 19. Rotavirus, another viral infection and is the common cause of severe diarrhoea among children. Pathogens can be bacterium, virus, or other microorganism based. Pathogens typically found in sewage include Salmonella, Shigella, E. coli, Streptococcus, Pseudomonas aeroginosa, mycobacterium and Giardia Lamblia (Source Water Quality and Health Council website). People suffering from dysentery, cholera, typhoid fever and other diseases of the intestines host parasitic bacteria which are passed in their stools. Pathogens can be inhaled as microbial aerosols.

Physical routes of transmission can include person-toperson contamination via contact with fomites (objects or materials which are likely to carry infection). Fomite-to-finger transfers from taps and door handles contaminated by feces or urine can serve as routes of transmission for enteric (relating to or occurring in the intestine) pathogens.

Travel hubs significantly increase the spread of infectious diseases. Drainage systems serving airports and other major travel hubs need to meet defined service levels that are commonly of high peak and short duration. Modern toilet layouts serving high usage public areas minimise contact surfaces where possible. This is achieved by avoiding doors (accepting those required for privacy), installing sensor activated taps and installation of hand dryers.

Table 1 (Source: DR IIOP KULMALA VTT 'Trackling the spread of pathogens in airports)

Influenza A virus 24 - 48h 8 - 12 h 100 to 1000 viral particles

Respiratory syncytial virus (RSV) 6 h 30 - 45 min 160 to 640 viral particles

Ebola virus 11 days 1 to 10 viral particles

Norovirus 56 days more than 40 days 10 viral particles

Yersinia pestis 3 days up to 5 days 100 to 500 organisms

Bacillus anthracis (spores) more than 10 years 8,000 to 50,000 spores

Salmonella 4 days 1 - 4 h at least 100,000 organisms

Campylobacteria 4 h 1 - 4 h less than 500 organisms

Staphylococcus aureus (MRSA) at least 4 days to weeks less than non-porous surfaces at least 100,000 organisms

As drainage systems can be the source of human infections and diseases, design elements need to take cognaissance of the following: -

a) Pipes sizes to meet calculated peak and continuous flows (where applicable) and graded to achieve minimum self-cleansing velocities.

b) Avoidance of steep gradients leading to separation of solids.

c) A voidance of tight sudden changes of direction resulting in increased flow turbulence.

d) Use of localised mechanical devices to control pressure transients.

e) Adequate venting.

f) Stacks to be kept in alignment where possible avoiding the need for short offsets.

g) M aterial selection to take into consideration building environment, damage to exposed pipes. Material selection in terms of proprietary systems with relation to wall thicknesses and reduced bore. Appropriate material selection for trade waste processes.

h) S pecialised pipework support and pipefittings, where seismic activity is a consideration.

i) Expansion coefficients of materials.

j) Accessibility to clear potential blockages.

k) Priming and preservation of trap seals.

As states and countries enter lockdown, the avoidance of cross contamination is being heralded from government and health ministries across the globe. It is equally important that as building service engineers within the disciplines of Public Health / Hydraulics ....'we practice what we preach'.

The author's experience spans four decades through eight countries. He experienced first hand, the perils of cross contamination and associated disease following a project in Al Asnam (Algeria) in the aftermath of the October 1980 earthquake. Like most young men commencing their careers in the early 80's risks weren't always carefully thought through and a spell in Iraq out the outbreak of the Iraq / Iran war proved how just how situations can change at the drop of a hat. A lengthy trek across the Eastern desert on a 45 seater bus with 57 people and 3 dogs to the safety of Amman proved to be a sobering experience.

Sharing project notes with a trainee architect in the classroom one evening at the Hertfordshire College of Building led indirectly to the authors first project outside of the UK in the Negev desert in Israel in 1979 where he worked alongside the American Core of Engineers on a military airbase. By now the travel bug had well and truely taken a hold and the UK no longer held much interest. Twenty years later of which two were spent in Saudi Arabia's Eastern Province (1998 - 2000) heading up the Public Health team on a 500 bed state of art private hospital for Aramco with the balance spent in South Africa, where invaluable project experience was gained on wineries, a brewery, hospitality, healthcare, commercial, defence and laboratories.

Returning to the UK in 2001-2004 he joined Mott MacDonald consulting engineers in Cambridge as their senior PH engineer and contributed to the public health design on Wembley stadium and a several education projects. Immigration to New Zealand followed in 2004 where he joined one of the countries biggest engineering consultancies on a series of healthcare, airport and multi-rise projects in Jakarta. The downturn of the NZ economy in 2012, provided yet another opportunity to travel and this time it was to Perth WA where he joined one of Australia's major engineering consultancies. Projects over a six year period included heavy plant workshops on two iron ore mines, Exmouth harbour infrastructure, several projects at Perth zoo, a ship building facility, a train maintenance depot, the FAL rail link and a project in Dubai's Marina which facilitated three trips over an 18 month period. A year on Australia East cost rounded up the Australian experience

Returning to NZ in May 2019, the author joined Mott MacDonald as their principal hydraulic engineer, where he is currently working on a series of challenging and interesting projects out at Auckland's international and domestic terminals. Les has been an active member of SoPHE and CIBSE since 2002 having represented the former on committees in Auckland and Perth WA, More recently he has rejoined the CIBSE Auckland chapter committee to continue fostering the interests of SoPHE (Society of Public Health Engineers).

The research of tradie-related businesses including builders, carpenters, electricians and plumbers found 50 per cent of the business owners had employed one of more family members. The survey also found that only one in 10 business owners consulted with their spouse on all or most business decisions.

Barry Magliarditi, Founder and CEO of The Game Changers, said the survey – which aimed to uncover the inner workings and challenges of these industries – provided some surprising insights into how these types of businesses are being run.

“The statistics show that family-run businesses are still very prevalent in Australia. While the percentage is only small, it’s interesting that 2% of respondents had at least four family members working for them, which is quite unique,” he said.

“In stark contrast, it seems this trust in the business isn’t being extended to spouses, with only a small percentage consulting their spouse on business decisions.”

The survey also revealed the biggest pain points for Australian trade businesses, with 60% struggling with cashflow and achieving a healthy profit margin.

However, despite these challenges and the fact that 2019 saw the sector suffer serious deterioration in trading conditions and profitability, small trade-based business

An encouraging 63% expected to be in better financial shape in the next 12 months, and a further 24% anticipated performance would remain the same. Only 13% forecast the business would be in worse shape.

Other findings of the survey include:

43% of tradies are primarily focused on business growth, with a further 29% saying they aimed to increase profitability . 80% said the cost of compliance was of concern, with almost 30% saying it was very concerning. 78% were concerned about a slump in demand for their services, a third of whom were very concerned. • The top five ways owners felt they could improve their businesses were: 1. Working on the business, not in it (72%); 2. Having a strong client pipeline (64%); 3. Having a written business plan with measurable targets (62%); 4. Attracting good people (51%); and, 5. Enhancing their leadership skills (51%).

Mr Magliarditi said the survey revealed some important insights into where these business owners needed support.

“Interestingly, 31% of respondents said they established the business because they were good at what they do, but struggled with the business side. A further 49% said that while the business was in good shape, there was more to be done to improve,” he said.

“Surprisingly, only one respondent described themselves as a strong leader of a business in great shape with no need for any changes.

“This research highlights that as is often the case with businesses, particularly trade-related businesses, the owner is good at their trade, but not very good at running a business. They haven’t actually been given the tools to run a profitable business that ultimately works without them, which should be a goal to aim for.

“Instead they stick on the tools and work huge hours to keep the wheels turning, as they also try to fit in the estimating, quoting, staff management, project owners were optimistic about their businesses future.

management and all the other tasks needed to manage operations while creating a viable pipeline. Often they simply don’t have these abilities in their core skill sets.

“That is why we work with our tradie clients to assess their businesses and how they can best deliver growth, while also having balance in their lives. A key part of achieving that is to not only work on their business, what we call the ‘outer game’, but also to support the ‘inner game’.

“This has been a core part of The Game Changers offering. It’s fundamental to how we help business owners achieve some amazing tangible results, including an average 3-4x growth in revenue and profits, while also watching their personal lives flourish.”

Media Contact: Ali Hiddlestone Lighthouse Communications Group 0467 541 542