Dubai Municipality Department of Public Health& safety

Guidelines for the control of legionella in:

air conditioning units & water systems

Contents Page Objectives of guidelines Scope of application A.Introduction 1. What is Legionella? 2. Conditions favoring the growth of legionella: 3. Legionnaires' disease. 4. How can I get rid of legionella? B. Legionella Control in Air conditioning Units & Water Systems 1. Where can legionella contamination occur? 2. Water Quality Guideline. 3. Monitoring and treating microbial levels in water systems 4. Appropriate treatment for Total Bacteria Counts: 5. Inspecting and cleaning a cooling water system of an air

conditioning unit or cooling tower 6. Providing and inspecting a water treatment system of an air

conditioning unit or cooling tower C. Definitions:

Objectives of guidelines Dubai Municipality, as part of it’s mandate, is striving to attain the highest level of health conditions within the public establishments to achieve it’s goals in protecting and promoting public heath through disease control measures. These guidelines are intended to ensure the use of quality water in public establishments, such as hotels, where hot and cold water is used for showers. This guidance is issued by Dubai Municipality to serve as a tool to enable concerned establishments to comply with proposed quality guidelines.

Scope of application

These guidelines are applicable to waters used in hotels and furnished apartments.

LEGIONELLA CONTROL

A. Introduction

1. What is Legionella?

Microorganisms are present almost every where. Most require water at an appropriate temperature and nutrients to survive. Some can cause serious infections to humans. The main groups of microorganisms are viruses, bacteria, fungi, algae, and protozoa. An example of a microorganism that can cause serious infection in humans is a bacterium of the Legionella genus, Legionella pneumophela. The infection is called Legionellosis. 2. Conditions favoring the growth of legionella:

temperature range from 20-45 C high nutrient level accumulation of organic material, sediments, and other organisms

3. Legionnaires' disease is a type of pneumonia that is caused by Legionella, a bacterium found primarily in warm water environments. Both the disease and the bacterium were discovered following an outbreak traced to a 1976 American Legion convention in Philadelphia. Pontiac fever, a flu-like illness, is also caused by Legionella organisms (legionellae), but is not as serious as Legionnaires' disease. Most people who get Pontiac fever recover within five days, without having to be hospitalized. Legionnaires' disease develops within 2 to 10 days after exposure to legionellae. Initial symptoms may include loss of energy, headache, nausea, aching muscles, high fever (often exceeding 104°F), and chest pains. Later, many bodily systems as well as the mind may be affected. The disease eventually will cause death if the body’s high fever and antibodies cannot defeat it. Victims who survive may suffer permanent physical or mental impairment.

4. How can I get rid of legionella?

Temperature It is recommended that hot water should be stored at 60˚ C and distributed so that, after one minute of running, a temperature of at least 50˚ C is attainable at outlets. Cold water storage and distribution should be at 20˚ C or below.

Ionization Ionization is the term given to the electrolytic generation of copper and silver ions for use as water treatment. The results of recent research have shown that where copper and silver ion concentrations can be maintained at 400ug/l and 40 ug/l respectively, the technique can, if properly managed, be effective against planktonic legionella in both hot and cold water systems.

Chlorination Chlorination is the process of applying any of the chlorine containing compounds such as sodium hypochlorite (bleach solution) to the water to achieve necessary destruction of all bacteria

Chlorine Dioxide Chlorine dioxide is an oxidizing biocide capable of reacting with a wide range of organic substances. There are commercial systems available that release chlorine dioxide from a stabilized precursor solution into water systems. The maximum value of Chlorine dioxide in water should not exceed 0.5 mg/l as Chlorine dioxide. Chlorine dioxide level of 0.5 mg/l can, if properly managed, be effective against planktonic legionella in both hot and cold water systems.

Ultraviolet light UV, and Ozone O3 The previous treatment systems are effective throughout the water system downstream to the point of application. UV & O3 can be used to treat water at or very close to the point of application.

B. Legionella Control in Air conditioning Units & Water Systems

1. Where can legionella contamination occur? Following is information about the main potential sources of legionella contamination in air conditioning units and cooling towers.

Fresh Air Intake Contaminated air from a cooling tower can be entrained into the air intake if positioned near a cooling tower that has become contaminated.

Cooling Towers and Evaporative Condensers In cooling towers, the warm water from the process (e.g. refrigerant gas compression) is cooled in the cooling tower and recirculated to conserve water. Air currents pass over large wetted surfaces (fill) to maximize evaporative cooling of the falling water. The air is either blown through the fill (forced draft type) or drawn through it (induced draft type).Evaporative condensers are similar in principle and in operation to cooling towers, except that the refrigerant itself is cooled. The water system comprises a pump which draws cooled water from the basin and recirculates it directly back to the top of the unit from where it is distributed over a bank of heat exchange pipes. There is no heat exchanger fill as in a cooling tower and system water volume is much less than for most systems incorporating a cooling tower. Large quantities of organic material and other debris may accumulate in the water of cooling towers and evaporative condensers as a result of the air being scrubbed as it passes through the equipment. With elevated temperatures and plenty of nutrients from organic material, the conditions are favorable for microbial growth. Many microorganisms may be dispersed in the water of the system. They may attach to pipe work, heat exchangers and to other surfaces forming biofilms incorporating various microorganisms. Biofilms provide an appropriate environment for the growth of Legionella bacteria within the system. These biofilms normally make up the bulk of the microbial population.

Drift Cooling system water is lost by carry over of droplets as drift in the exhaust air stream. This drift contains visible droplets, as well as aerosol that can be inhaled. Health problems may arise when the cooling tower from which the drift originates, is highly contaminated.

Evaporative Coolers In evaporative coolers, water is trickled over a medium through which the air is drawn. The evaporation of water cools the air as it passes through. The water normally collects in a sump and is recirculated. There is potential for microbial growth in such a system. Evaporative coolers should be kept dry when not in use

2. Water Quality Guideline. A detectable population of legionella bacteria in the water indicates that there will be a larger population in sediments and biofilm within the system. Undetectable legionella bacteria in the water sample may not necessarily indicate that the system is free of these organisms, as they may still be attached to surfaces. The primary tool for the control of legionella bacteria is good hygiene practice. It has been found to be very difficult to manage the microbial characteristics of a cooling water system based only on legionella bacteria-specific data. Monitoring the overall bacterial level is far more effective.

Ideally, the Total Bacteria Count (TBC) should be below 100 000 cfu/ml of water sample. However, this may not be practical in all circumstances. Concentrations above 100 000 cfu/ml indicate that conditions in the system are favoring bacterial multiplication. The table below details recommended action to be undertaken for a range of TBC’s.

A legionella bacteria count should not exceed 10 cfu/ml.

3. Monitoring and treating microbial levels in water systems Test for Total Bacteria Count (TBC) in system water regularly (at least monthly) and for Legionella sp (at least every three monthly), to assess efficacy of the water treatment system and general system cleanliness. Water samples should be tested in a certified microbiology lab, and saved as documents. Regular examination of water for the presence of legionella bacteria is not usually warranted, because:

the chances of this organism being present are very high; interpretation of results is largely subjective; false negative results are possible; a negative result may lead to a false sense of security; any cooling water system can quickly become heavily colonised if it

suffers neglect; presence of the organism does not necessarily mean that infections will

occur; and frequency of testing is problematic with recolonisation occurring rapidly.

4. Appropriate treatment for Total Bacteria Counts: Total Bacteria Count: Appropriate treatment: < 100 000 cfu/ml: ! continue with routine maintenance and inspection >100 000cfu/ml, < 500 000cfu/ml: ! retest ! review dosing ! monitor trend > 500 000cfu/ml, < 1 000 000cfu/ml: ! add alternative biocide ! retest ! review dosing ! monitor trend >1 000 000cfu/ml: ! drain tower ! add alternative biocide ! review dosing equipment, quantities and frequency ! retest ! monitor trend

5. Inspecting and cleaning a cooling water system of an air conditioning unit or cooling tower An owner of an airconditioning unit or cooling tower should ensure the cooling water system of the unit or tower -

is inspected and tested for total bacteria count (TBC) at least once every month by a competent person to identify if the system contains acceptable levels of microbial contaminants; and

if the system contains unacceptable levels of microbial contaminants - is treated to bring the TBC to acceptable levels; and

if the system is shut down for more than four (4) days – is cleaned before it is restarted; and

is cleaned no more than 6 months after the last cleaning. 6. Providing and inspecting a water treatment system of an air conditioning unit or cooling tower An owner of an air conditioning unit or cooling tower should ensure -

the cooling water systems are provided with suitable automatically controlled, water treatment systems for effective management of corrosion, scaling, fouling and microbial growth; and

the water treatment systems are inspected at least once every month by a competent person to ensure the systems are operating in the ways for which they were designed.

REDUCING THE RISK OF LEGIONNAIRES DISEASE

THE 14 POINT CHECKLIST

The risk of legionnaire's disease can be minimized. Any hotel that does not have an active programme to control the growth of legionella bacteria is negligent in

ensuring the safety of their guests. This programme should include the following:

Have one named person responsible for legionella control. Ensure the named person is trained in control of legionella and other staffs

are trained to be aware of the importance of their role in controlling legionella.

Keep hot water hot and circulating at all time: 50oC – 60oC (too hot to put hands into for more than a few seconds).

Keep cold water cold at all times. It should be maintained at temperatures below 25C.

Run all laps and showers in guest rooms for several minutes al least once a week if they are unoccupled and always prior to occupation.

Keep shower heads and taps clean and free from scale. Clean and disinfect cooling tower and associated pipes used in air

conditioning systems regularly – at least twice a year. Clean and disinfect water heaters (calorifiers) once a year. Disinfect the hot water system with high level (50mg/l) chlorine for 2-4

hours after work on water heaters and before the beginning of every season.

Clean and disinfect all water filters regularly – every one to three months. Inspect water storage tanks, cooling towers and visible pipe work monthly.

Ensure that all coverings are intact and firmly in place. Inspect the inside of cold water tanks at least once a year and disinfect

with 50mg/l chlorine and clean if containing a deposit or otherwise dirty. Ensure that system modification or new installations do not create

pipework with intermittent or on water flow. If there is a spa pool (also known as whirlpool spas," Jacuzzis", spa baths)

ensure that:

• It is continuously treated with 2-3mg/kl chlorine or bromine and the levels are monitored at least three times a day.

• At least half of the water is replaced each day. • Sand filtars are backwashed daily. • The whole system is cleaned and disinfected once a week. • Daily records of all water treatment readings such as

temperature and chlorine concentration are kept and ensure they are checked regularly by the manager.

Along with any disinfection methods of treatment used, the following are recommendations and sound practices to help manage and reduce the incidence of Legionella contamination within domestic plumbing (hot and cold) water systems:

Reduce deadlegs (stagnant lines and stubs) in the system, Clean and inspect hot water tanks regularly – annually as a minimum, Continually run hot water circulation pumps – avoid recycling to mixing

valves only, Store hot water at a minimum temperature of 60oC (140oF) and deliver to

the taps at a minimum temperature of 50oC (122oF), Store and distribute the cold domestic water below 20oC (68oF) – if not

possible, then consider monitoring for Legionella and using a disinfection system if Legionella are not under control,

Flush the entire water system on a regular basis, Consider routine potable water treatments – including the use of approved

biocides.

-- The following is an abbreviation of the emergency cooling tower disinfection method:-

Shut off the cooling tower fans; Keep makeup water valves open and the circulation pumps operating; Close outdoor air intake vents located within 30 meters of the cooling

tower; Achieve an initial free residual chlorine (FRC) of at least 50 mg/L; Add a dispersant to tower water within 15 minutes of chlorine addition,

then maintain 10 mg/L FRC for 24 hours; Drain and refill the system, then repeat steps 4 and 5 at least once to

remove all visible algae-like film; Using a brush and water hose, thoroughly clean all water-contact areas,

including the basin, sump, fill, spray nozzles, and fittings; Circulate 10 mg/L FRC for one hour, then flush the system until free of all

sediment; Refill the system with clean water and return to service.

C. Definitions:

‘aerosol’ means airborne water particles less than 10∝m in diameter. “air conditioning unit” means a unit of plant that provides air conditioning and that either - (a) incorporates a cooling tower; or (b) consists of 1 or more compressors and the power rating required for operation of the air conditioning unit is 50 kW or more. ‘biofilm’ means a layer of microorganisms contained in a matrix which may form a thin slime on surfaces in contact with water. Legionella bacteria has been shown to be a biofilm organism. ‘clean’ means free from visible sludge, foam, slime (including algae and fungi), rust, scale, dirt, dust and any deposit or accumulation of impurities, or any other foreign material. ‘cleaning’ means physical scrubbing or water blasting. Cleaning may also involve disinfection (chemical cleaning), draining, dispersing and removing solids and flushing. “competent person” means -

for a cooling water system – a person who has acquired, through training, qualifications, experience or a combination of these, the knowledge and skill enabling the person to inspect and test the cooling water system of an air conditioning unit or cooling tower to identify the presence of microbial contaminants; and

for a water treatment system – a person who has acquired, through training, qualifications, experience or a combination of these, the knowledge and skill enabling the person to inspect the water treatment system of an air conditioning unit or cooling tower to ensure the system is operating in the way for which it was designed.

“cooling tower” means a device for lowering the temperature of water by evaporative cooling in which atmospheric air passes through spray water exchanging heat, and includes a device incorporating a refrigerant or water heat exchanger. “cooling water system” means an open reticulated water system serving equipment such as evaporative condensers or cooling towers. “water treatment system” means an automatic method of treating water, by chemical application or other method, introduced to control corrosion, scale and microbiological growth.