The importance of risk prevention

Global warming means microbiological contamination is an increasing problem in water supply systems. A Portuguese report, abridged and reproduced here, highlights how water safety plans can reduce risk. This article is derived from a CIB paper
by Armando Silva-Afonso and Isabel Lanca.

The case of the Portuguese spa resort and hospital Termas das Caldas da Rainha shows that countries need to institute basic procedures and safeguards to guarantee water safety through national water safety plans (WSPs).

Regular water analyses at Termas das Caldas da Rainha revealed the presence of Legionella in the spa water – and prevented human infection.

A WSP involves identifying risks to supply systems to prevent biofilm formation and cross-contamination due to lack of maintenance.

In the international context of the Bonn Charter Framework, which considers the best available scientific knowledge and the circumstances of the individual country, a safe water supply should be based on management control systems included in a WSP.

Water safety management in various national systems generally implies drawing up safety schemes for drinking water quality to assess system risks and mitigate them, and to measure water quality by monitoring relevant Standards.

In the face of climate change predictions it is especially important to monitor microbiological parameters. These predictions envisage changes that are likely to cause micro­organism proliferation as a function of the ambient temperature.

Climate change could have repercussions for water distribution system fixtures and fittings in buildings, heightening the risk of bacterial colonies and putting the quality of drinking water at risk.

Some bacteria that naturally occur in lakes, rivers, wells, springs and streams can develop opportunistically in artificial environments such as urban water supply systems, where there are favorable conditions for them to multiply and spread.

Natural conditions conducive to the occurrence of such bacteria are linked with water temperatures of 20-45ºC (68-113ºF), high concentrations of algae and protozoa (such as amoebae) and the presence of certain nutrients, like iron and nitrogen.

In artificial systems the main factors encouraging their development are the presence of nutrients, formation of biofilms, dead points or water stagnation in plumbing, temperatures of 20-50ºC (68-122ºF) and the byproducts of corrosion.

Legionella, a respiratory infection borne by air and water, is of particular concern. It is spread by inhaling bacteria-contaminated water droplets (aerosols or sprays), not by personal contact or contaminated food. However, cases have been reported of inhalation followed by ingestion of contaminated water.

The bacterium is associated with Legionnaire’s Disease (or Legionellosis)

and Pontiac fever. The first is more common and it develops as an acute pneumonia that can be fatal.

Policies for preventing Legionella are relatively new to Portugal, and control of the disease is not a parameter usually considered in monitoring schemes. As there is no specific legislation, prevention measures have tended to be implemented by public health services. Such measures include risk assessment and intervention in systems where pools of Legionella may be easily spread.

Interventions have taken place in health-care facilities, catering establishments and municipal amenities. The measures include public information campaigns, and handbooks on control and disinfection procedures, risk assessment and management.

The importance of training public health officers, doctors, nurses, and service and maintenance technicians in their respective fields cannot be overstated.

As in other countries, the Portuguese public health authorities are compiling databases of public facilities at risk of contamination, such as health-care units and spa resorts. Routines for the prevention of Legionella are beginning to be established in private and public establishments.

The case of the Hospital Termal das Caldas da Rainha may be regarded as a typical example of risk management associated with Legionella Pneumophila. It took several interventions between August 2004 and January 2006 to correct the situation. Ultimately the intervention was successful, and no human infection was recorded.

The sulfurous waters of Caldas da Rainha have been famed for their health-giving properties since Roman times. Founded in 1485, the Hospital Termal das Caldas da Rainha is the oldest of its kind in the world.

The spa waters are used for treating a variety of bronchial and other ailments. Treatments include simple immersion baths and air-bubble baths, and a variety of douches, inhalations and spraying techniques during which water enters the body.
The Caldas da Rainha spa water is rich in mineral salts, warm (about 34ºC, or 93ºF), almost pH neutral and bacteriologically fit for spa purposes.

The spa water plumbing system has been overhauled over the years, but there are still old sections, dead points and old fixtures. Some fixtures are classified as having historic value and to be preserved. All of these factors increase the risks arising from consolidated bacterial colonization.

There are new two mains pipes that are used alternately so that each can be disinfected with ozone. These pipes bring the spa water to a substation where it is distributed to baths and the other facilities. The substation is disinfected with steam at 120ºC (248ºF), and all downstream pipes are of stainless steel.

Before the inhalations, there is a further disinfection with water vapor at 80ºC (176ºF). Neutral disinfectant, phosphated with cationic surfactants, is applied.

Despite the various regular disinfecting procedures, the hospital was closed for four years in 1997 when contamination with Pseudomonas aeruginosa was found during routine analysis.

When it was re-opened in 2001, a safety plan was put in place. This included a physical-chemical and microbiological monitoring plan and a maintenance scheme, under which specific disinfecting procedures were implemented in the piping to remove bacterial colonies.

Legionella was one of the parameters looked for, and it was not found until 23 July 2004, when there were several positive analyses. Once these results were known, and considering the kind of contact with aerosols that all the amenities undergo, the public health department ordered immediate suspension of hospital activities, and a disinfection program with sodium hypochlorite was started.

The hospital remained closed until safe analytical results were obtained six months later.

After the closure, the entire facility and its procedures were examined and it was decided to carry out ‘shock treatments’ to disinfect the whole system, particularly water tanks and sections where stagnation might occur. The disinfection system was reviewed (including ozonization) and corrective measures implemented in terms of construction to sterilize the facilities with protective equipment and systems.

The disinfection procedures implemented after the review were strengthened, but the next analytical results were not very encouraging – Pseudomonas aeruginosa, mesophils and Legionella Pneumophila were found, indicating the presence of persistent contamination.

New structural measures were undertaken and in November 2004 several additional interventions were concluded: replacing steam pipes, iron plumbing, metal tanks and filters, ventilation and cleaning, fixing leaks and discharge drainage.

But analytical control still showed the presence of Legionella. Another assessment was carried out, plus the emergency strengthening of measures – notably replacement of the mains pipes. This had been delayed for reasons of cost.

Once the mains pipes were replaced with stainless steel pipes, the disinfection (ozonization) process was restructured.

After analytical control with three negative analyses in a row, the contamination was finally deemed to have been beaten.

The establishment was granted leave to re-open in February 2006, and the system has remained suitable for use as a spa. Even though it involved a highly complicated intervention, the fight against the Legionella contamination in the Hospital Termal das Caldas da Rainha succeeded, and no contamination has been found since then.

This outcome was undoubtedly the result of safety procedures that were introduced over a long period, in particular the microbiological monitoring of water quality, a procedure that permitted prompt detection of the problem.

It shows that water safety in various parts of the amenity was ensured through a policy similar to a WSP, a fundamental part of which is the identification and conservation of the network, compliance with maintenance methodologies and a proper monitoring program (with parameters appropriate for water quality and its use characteristics).

There was no WSP in place to provide guidance on the technical measures required, but the necessary risk prevention was implemented through analytical controls and epidemiological research. The processes undertaken in this case provide a good model for strategies to contain future outbreaks.

Condensed and reproduced with the permission of University of Aveiro professor of hydraulics Armando Silva-Afonso and Center Region Health Authority advisor on environmental issues Isabel Lanca.

Related Posts