RBQ Safety Code: Requirements and guidelines when testing for Legionella

Among the safety code’s requirements, water quality must be periodically monitored with physicochemical/microbiological indicators. Additionally, the concentration of Legionella pneumophila must be measured with the following steps:

• The tower owner must determine the concentration of Legionella pneumophila at every restart after wintering and subsequently every 30 days. This can be done by taking a sample or arranging to have a sample collected.
• If a decontamination procedure has been applied after obtaining a result posing a health risk, a sample should be taken between 2 to 7 days from the procedure to ensure compliance has been restored. It is also recommended to perform another test after a major change in the maintenance program. After adding biocide it is important to wait at least 48 hours before sampling.
• Table 1 suggests different levels of action and control strategies according to the monthly monitoring results for Legionella pneumophila.

Table 1: Control Strategies for Legionella pneumophila

LEVEL OF ACTION	MONITORING RESULT	CONTROL STRATEGY
Normal	< 10 000 CFU/L	Continue with the treatment and the maintenance program.
Intervention Threshold	≥ 10 000 CFU/L < 1000 000 CFU/L	Identify the cause of the increase and take corrective actions. Check efficiency of corrective actions.
Impossible to quantify the concentration of Legionella pneumophila due to an interfering flora	Identify the causes of interfering Flora. Apply corrective actions. Check efficiency of corrective actions.
Health Risk Immediate Action	≥ 1000 000 CFU/L	Promptly engage the decontamination procedure. Identify the causes and modify the maintenance program accordingly. Check efficiency of corrective actions. Perform another analysis by culture for Legionella pneumophila. The laboratory is obliged to release a statement to the RBQ and the Public Health Department.

For more details on the RBQ’s regulation, and for the explanatory guide to cooling tour maintenance, please visit the following websites:

Regulation (French only)

Guide (French only)

Cooling Tower Sampling

Sampling is an essential step for achieving accurate test results. Please abide by the following guidelines when collecting a sample:

• Always take samples safely and use containers sent by the laboratory (250ml sterile container).
• Preservative is present in the container in order to inhibit oxidizing biocidal effect, such as the presence of chlorine.
• Collect the sample from a representative area of the water system.
• Clearly identify the containers.
• Send samples to the laboratory in a cooler on the same day they are collected.
• Cooling the samples is unnecessary and they should be transported at room temperature.
• Temperature fluctuations must be avoided.
• Sample analysis should be performed as soon as possible and within 48 hours after sampling.

For a detailed sampling procedure document, consult the CEAEQ’s document entitled Protocole d’échantillonnage de l’eau du circuit des tours de refroidissement pour la recherche des légionelles DR-09-11 (French only).

Detection of Legionella spp

Bureau Veritas offers an enumeration method for Legionella spp by culture with an identification of Legionella pneumophila, the principal species causing legionellosis.

Bureau Veritas is accredited by the Ministère de l’Environnement et de la Lutte aux changements climatiques (MELCC) for domain 606.

Analytical Method Offered

Bureau Veritas’ analytical method is inspired from recognized methods for Legionella determination, such as ISO 11731 (2017). Quality controls are performed with known Legionella strains for every series of analysis to ensure validity of results obtained. Results are reported in CFU/L (colony-forming unit per water litre).

Since Legionella are slow-growing bacteria, it may take up to 12 working days to obtain analysis results. Also, as other flora is often present with Legionella in a sample, it is important to keep in mind that the detection of Legionella can be impaired. A sample can undergo various treatments to remove the interfering flora, but it can result in an underestimation of the concentration of Legionella.

Other Analyses

Bureau Veritas can also analyze water samples for Legionella outside of RBQ regulation. Examples include water fountains, whirlpools, potable water, water sprinklers and hot water tanks.