The provision of water on board vessels has changed little over the years. Fresh or potable water can be taken on board whilst a vessel is in port and stored or potable water can be made on board using desalination techniques. Single distillation equipment has been documented since the 1700’s however today high/low pressure evaporation, distillation, filtration or reverse osmosis techniques are used. A combination of desalination and the storage of water may be employed.

 

 

 

Water Quality

Factors affecting water quality include:

  • The quality of water supplied to the vessel
  • Contamination of the water supply

It is a requirement of the International Health Regulations 2005 that every port is ‘provided with a supply of pure drinking water’. Where desalination techniques are employed it is recommended that the equipment is not used within 20 miles of any land or other pollution source. In both respects the water on board the vessel should be wholesome and comply with the International standards for drinking water.

Water quality standards specifically relating to water on board vessels are given in the HPA guidance on water quality on board vessels. If a microbiological examination of water reveals levels in excess of the standards shown in Table 3 then the water should be treated – the tank should be emptied, cleaned and refilled with fresh chlorinated water.

The UK generally accepts chlorine as a disinfectant which requires around 20 minutes contact time to react. It can be the case that shore mains water only contains low concentrations of free chlorine which may be further decreased within the ship environment. Although there is no requirement to do so and control measures will be influenced by the quality of the source water, it is considered good practice to add chlorine as a routine when loading fresh water to a level that produces a 0.2 mg/L (ppm) residual free chlorine or 1.0 mg/L (ppm) chloramine when chlorinated water is supplied. Some other treatments available include: Silver Coated Filter Candles, Electro-Silver Ionisation, Ultra Violet Sterilisation and Thermal Disinfection.

PARAMETER ACCEPTABLE LEVEL ACTION LEVEL
E.coli 0 >1 per 100ml
Enterococci 0 >1 per 100ml
Coliforms 0 >100 per 100ml
Aerobic Colony Count <100 >1000 per 100ml
Pseudomonas aeruginosa (spa pools) 0 >1 per 100ml
Pseudomonas aeruginosa (swimming pools) <50 >50 per 100ml

Contamination

Contamination may occur during tank filling operations, during tank inspection or by distribution through an infected system. Hoses used for filling operations must be exclusively used for this purpose and must be fitted with effective anti-backflow valves. They should be durable with a smooth impervious lining and have suitable adapters and caps. Ideally they should be blue in colour and be clearly marked at both ends ‘Potable Water Only’. Contamination of the hose by dragging the ends on the ground, pier or deck or by dropping in to the harbour water must be avoided.

Hoses and hydrants must be flushed through before connection to the tank filling point. Hoses should always be drained, cleaned, capped and suitably stored between uses and should be disinfected every 6 months using super chlorinated water at 100 ppm with a contact time of 1 hour.

Tanks and distribution systems should be designed to prevent contamination and facilitate cleaning and disinfection. Fresh water tanks should be emptied, flushed and refilled every 6 months and opened, emptied, ventilated, inspected and recoated annually. During inspection and maintenance of the tanks care must be taken to avoid the introduction of contaminants. Before refilling the tanks, the distribution system should be super chlorinated to 50 ppm with a contact time of 24 hours. In exceptional cases the concentration can be increased to 100 ppm with a contact time of 1 hour, however the system must be completely drained and thoroughly flushed before filling with potable water.

Further information is contained in the Merchant Shipping (Provisions and Water) regulations 1989, and Merchant Shipping Notices; M1214(1986), M1401(1989) and MGN61(1998).

All Masters are advised to keep a ‘Fresh Water System Maintenance Log’ which should include details of: tank capacities, distribution system, filters, construction materials, maintenance schedules, disinfection schedules, sample frequency, sample results and remedial actions taken.

Disinfection

The most commonly used compounds for disinfecting drinking water are:

  • Powders – Chlorinated Lime and High Test Hypochlorite
  • Liquids – Commercially prepared Sodium Hypochlorite solutions

These chemicals are potentially hazardous and should always be stored, handled and prepared in accordance with manufacturer’s instructions.

The chemicals are mixed to produce a chlorine releasing solution of known concentration. This solution is added to the ship’s almost empty water tank. The tanks are then refilled with clean fresh water and all taps and outlets on the distribution system opened until they discharge chlorine smelling water. The system is then topped up with fresh chlorine solution to replace the water lost when draining off. The system is then left to allow a contact period of between 1 and 24 hours depending on the concentration of the chlorine used.

Following treatment the system should be drained of super chlorinated water and refilled with fresh potable water from a known clean source. The replacement water should have a residual free chlorine level of not less than 0.2ppm.

Amount of Chlorine Compound Required
Capacity of System (including tanks and piping) Chlorinated lime 25% High-test calcium hypochlorite 70% Sodium Hypochlorite Solution
5% 10%
For each Kg Kg Ltrs Ltrs
1000 litres 0.2 0.08 1 0.5
10 tonnes 2 0.8 10 5

Note: Check that the strength of the chlorine compounds are as in the table. If not, adjust the quantity accordingly. To obtain a concentration of 0.2ppm multiply the quantity in the table by four. The result will be in grams not kilograms.

Why should vessels be concerned about Legionella?

Legionnaires’ disease is a potentially fatal form of pneumonia. If infected between 10-30% of people die unless treated early and quickly.

There are approximately 200-250 cases of Legionella infection annually in the UK and around 12% of these prove fatal. Half are associated with foreign travel and the rest with cooling towers and hot & cold water systems in hotels, hospitals, factories, residential homes, ships, spa baths etc.

What are the signs & symptoms?

The symptoms include a flu-like illness, followed by a dry cough which frequently progresses to pneumonia. Approximately 30% of people infected may have diarrhoea and vomiting and 50% may show signs of mental confusion. The incubation period is from 2-10 days.

Who is at higher risk?

Men more than women, people over 50, smokers, alcoholics, diabetics, people with a chronic underlying disease and/or a weakened immune system.

Where is Legionella found?

Legionella bacteria are widespread in natural sources of water including rivers, streams and ponds and may even be found in soil. It has never been isolated in salt water so vessels that make all their potable water by evaporation or reverse osmosis have a lower risk of the bacteria being present. They are significant when found in man made recirculating and hot and cold water systems

How can Legionella be contracted?

Only when water contaminated with Legionella bacteria becomes aerosolised so that it can be inhaled does it pose a risk to health.

For example:

  • When having a shower
  • When running sink taps when using a hot spa tub
  • Warm moist air circulated by air conditioning, heating units & humidifiers
  • When using fire hoses (if fresh water is used)
  • Washing down the hold super structure (if freshwater is used)

To drink water contaminated with Legionella bacteria will NOT cause you to be infected and there has been no evidence of person-to-person transmission.

What do we need to do?

Assess the water systems of the vessel and identify any risk areas. Remove or reduce possible sources of contamination through risk assessment, routine maintenance and regular cleaning, to reduce the chance of infection.

YOU REDUCE THE CHANCE OF INFECTION

Questions to ask yourself

  • Is the hot water boiler temperature hot enough to ensure temperatures of above 50°C or below 20°C are achieved at all outlets ?
  • Have I ensured hot cold pipes are insulated and do not affect one another?
  • Have I identified any other risk factors and corrected them?
  • Have I identified all ‘dead ends’ within the hot cold water system and removed them?
  • Have I reduced the risk on board the vessel?

If you have answered ‘YES’ to all the questions above you should have successfully reduced the risk of Legionella being present on board the vessel.

What practical measures should be taken?

Assess the water systems of the vessel and identify all risk areas.

  1. Study the hot & cold water system plans and identify all water outlet points and in particular those that are rarely used ‘dead legs’, any potential ‘blind ends’ (blanked off pipes where the water cannot circulate) or long pipe runs.
  2. Check the water temperature of ALL hot & cold water points, i.e taps, showers, hoses.
  • hot water should reach >50°C within 1 min. and cold water 20°C or less within 2 mins
  • the boiler output temperature must be above 60°C and the return not less than 5°C lower than the output temperature
  • the hot supply must be greater than 50°C at the outlets
  • the cold supply must be less than 20°C at the outlets
  1. Check what actual cleaning, maintenance and disinfection routines are in place on the vessel at present.
  2. Assess and identify ALL points where water could be made into an aerosol and breathed in by the crew, passengers & visitors.
  3. Document your findings so that the information can be included in the planned maintenance or ISM procedures which can be referred to by any Master or responsible officer.

An ideal vessel at least risk is one where the temperature readings are satisfactory, you have no ‘dead ends’, the ‘dead legs’ are used frequently, the vessel makes all its potable water by evaporation or reverse osmosis, and cleaning & disinfection procedures are in place.

The condensed water from the air conditioning should flow to waste and not to a tank for reuse.

Any pressure washers used should be regularly drained and disinfected.

Any water features (Fountains) and hot spa baths must be regularly cleaned and disinfected.

What cleaning and maintenance procedures should be implemented?

The minimum recommended requirements are as follows:

  1. The hot water boiler outlet temperature must be greater than 60°C
  2. Dismantle, inspect, clean and soak the shower heads and pipework for a few hours at least once every 3 months in a disinfectant/chlorine solution. Remove any sediment, algae or calcified deposits found.
  3. Locate and eliminate all ‘blind ends’ and ‘dead legs’.
  4. Super chlorinate the fresh water tanks twice a year and flush the water through all outlet points ‘dead legs’.
  5. Any crew or passenger cabin that has been out of use for 2-4 weeks must have tall outlets flushed and have the shower head and hose cleaned and soaked in a chlorine solution prior to the cabin being used.
  6. Have the water bacteriologically tested if you find hot & cold water temperatures are outside those recommended.

What are the signs & symptoms?

The symptoms include a flu-like illness, followed by a dry cough which frequently progresses to pneumonia. Approximately 30% of people infected may have diarrhoea and vomiting and 50% may show signs of mental confusion. The incubation period is from 2-10 days.

Who is at higher risk?

Men more than women, people over 50, smokers, alcoholics, diabetics, people with a chronic underlying disease and/or a weakened immune system.

Where is Legionella found?

Legionella bacteria are widespread in natural sources of water including rivers, streams and ponds and may even be found in soil. It has never been isolated in salt water so vessels that make all their potable water by evaporation or reverse osmosis have a lower risk of the bacteria being present. They are significant when found in man made recirculating and hot and cold water systems

How can Legionella be contracted?

Only when water contaminated with Legionella bacteria becomes aerosolised so that it can be inhaled does it pose a risk to health.

For example:

  • When having a shower
  • When running sink taps when using a hot spa tub
  • Warm moist air circulated by air conditioning, heating units & humidifiers
  • When using fire hoses (if fresh water is used)
  • Washing down the hold super structure (if freshwater is used)

To drink water contaminated with Legionella bacteria will NOT cause you to be infected and there has been no evidence of person-to-person transmission.

What do we need to do?

Assess the water systems of the vessel and identify any risk areas. Remove or reduce possible sources of contamination through risk assessment, routine maintenance and regular cleaning, to reduce the chance of infection.

YOU REDUCE THE CHANCE OF INFECTION

Questions to ask yourself

  • Is the hot water boiler temperature hot enough to ensure temperatures of above 50°C or below 20°C are achieved at all outlets ?
  • Have I ensured hot cold pipes are insulated and do not affect one another?
  • Have I identified any other risk factors and corrected them?
  • Have I identified all ‘dead ends’ within the hot cold water system and removed them?
  • Have I reduced the risk on board the vessel?

If you have answered ‘YES’ to all the questions above you should have successfully reduced the risk of Legionella being present on board the vessel.

What practical measures should be taken?

Assess the water systems of the vessel and identify all risk areas.

  1. Study the hot & cold water system plans and identify all water outlet points and in particular those that are rarely used ‘dead legs’, any potential ‘blind ends’ (blanked off pipes where the water cannot circulate) or long pipe runs.
  2. Check the water temperature of ALL hot & cold water points, i.e taps, showers, hoses.
  • hot water should reach >50°C within 1 min. and cold water 20°C or less within 2 mins
  • the boiler output temperature must be above 60°C and the return not less than 5°C lower than the output temperature
  • the hot supply must be greater than 50°C at the outlets
  • the cold supply must be less than 20°C at the outlets
  1. Check what actual cleaning, maintenance and disinfection routines are in place on the vessel at present.
  2. Assess and identify ALL points where water could be made into an aerosol and breathed in by the crew, passengers & visitors.
  3. Document your findings so that the information can be included in the planned maintenance or ISM procedures which can be referred to by any Master or responsible officer.

An ideal vessel at least risk is one where the temperature readings are satisfactory, you have no ‘dead ends’, the ‘dead legs’ are used frequently, the vessel makes all its potable water by evaporation or reverse osmosis, and cleaning & disinfection procedures are in place.

The condensed water from the air conditioning should flow to waste and not to a tank for reuse.

Any pressure washers used should be regularly drained and disinfected.

Any water features (Fountains) and hot spa baths must be regularly cleaned and disinfected.

What cleaning and maintenance procedures should be implemented?

The minimum recommended requirements are as follows:

  1. The hot water boiler outlet temperature must be greater than 60°C
  2. Dismantle, inspect, clean and soak the shower heads and pipework for a few hours at least once every 3 months in a disinfectant/chlorine solution. Remove any sediment, algae or calcified deposits found.
  3. Locate and eliminate all ‘blind ends’ and ‘dead legs’.
  4. Super chlorinate the fresh water tanks twice a year and flush the water through all outlet points ‘dead legs’.
  5. Any crew or passenger cabin that has been out of use for 2-4 weeks must have tall outlets flushed and have the shower head and hose cleaned and soaked in a chlorine solution prior to the cabin being used.
  6. Have the water bacteriologically tested if you find hot & cold water temperatures are outside those recommended.

More Information

28 people died and 242 were infected in Holland at the Bouenkarspel Flower Festival because of a poorly maintained spa pool that had been connected to a fire hose water supply