AS 5059 - Legionella Control Australia

Power Station Cooling Tower Water Systems - Management of Legionnaires’ Disease Health Risk

AS 5059 Management of Legionnaires' Disease - To improve the control of legionella bacteria, Legionnaires’ disease and general microbial control performance requirements at large installations, the Australian Standard AS 5059 entitled “Power station cooling tower water systems - Management of Legionnaires’ disease health risk” was developed, primarily for use by power station designers, constructors, owners, operators, and regulatory authorities.

Advanced Risk Management

This Australian Standard sets out an advanced risk management methodology that includes all procedures set out in AS/NZS 3666 Part 3.

Although AS 5059 is focused on cooling tower systems at power stations, the approach taken to the control of those risks associated with Legionnaires’ disease is useful for systems of any size and has proven to be comprehensive in its application.

Management of Legionniares'Disease

AS 5059 - “Power station cooling tower water systems - Management of Legionnaires’ disease health risks”, identifies control strategies for the management of Legionnaires’ disease arising from power station associated cooling tower water systems that are linked with -

condensing systems of steam-driven turbines; and
auxiliary plant where -
...a chemical water treatment programme is in place to control the presence of Legionella bacteria, and
...shutdown for system treatment and cleaning would require total or partial shutdown of the power station.

This standard sets out an advanced risk management methodology and although focused on systems at power stations, the approach is useful for systems of any size, and has proven to be comprehensive in its application.

Contents of AS 5059 Include:




Section 1 Scope and General

1.1 Scope

1.2 Objective

1.3 Application

1.4 Referenced Documents

1.5 Definitions

1.5.1 Aerosol
1.5.2 Automatically controlled (water treatment)
1.5.3 Biocide
1.5.4 Bio-film
1.5.5 Blow-down (or bleed)
1.5.6 BOD
1.5.7 Chemical treatment
1.5.8 Clean
1.5.9 COD
1.5.10 Commissioning
1.5.11 Continuous
1.5.12 Cooling tower
1.5.13 Cooling (tower) water system
1.5.14 Dead leg
1.5.15 Drift
1.5.16 Generator
1.5.17 Grid
1.5.18 HCC (or total plate count)
1.5.19 Legionnaires' disease
1.5.20 Maintenance
1.5.21 Monitoring
1.5.22 Power station
1.5.23 Regulatory authority
1.5.24 Reporting
1.5.25 Should
1.5.26 TOC

Section 2 Design of Power Station Cooling Tower Water Systems

Section 3 Maintenance of Water Quality and Control of the Prescence of Microorganisms

3.1 Scope

3.2 Water Quality Management

3.2.1 Chemical treatment
3.2.2 Monitoring
3.2.3 Assessment

3.3 Prescence of Legionella

3.3.1 Monitoring
3.3.2 Assessment
3.3.3 Control

3.4 Prescence of Other Heterotrophic Bacteria

3.4.1 Monitoring
3.4.2 Assessment
3.4.3 Control

3.5 Results and Records

3.6 Evidence of Compliance

Section 4 Risk Management

Section 5 Development of Risk Management Plan

Section 6 Implementation of Risk Management Plan

6.1 General

6.2 Treating Risks

6.3 Water Treatment Control Strategies to Address Identified Risks

6.4 Monitoring

6.5 Reporting

6.6 Communication

6.7 Verification

Section 7 Review of Risk Management Plan

Appendix A - Risk Clarification

A1 General
A2 Risk Analysis

Appendix B - Sample Risk Schedules

Appendix C - Inherent Risk Evaluation

Appendix D - Cooling Water Sampling Procedure

D1 Scope
D2 Personnel Carrying Out Sampling
D3 Sample Storage and Transport
D4 Particulars of Sampling Containers
D5 Particulars of Sampling
D6 Technique of Sample Collection

Expert Legionella Assistance

For further information and expert assistance regarding legionella risk management and compliance issues please call +44 (0) 161 877 0586 to speak to one of our specialist advisors or email your questions to This email address is being protected from spambots. You need JavaScript enabled to view it..

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