DEPARTMENT OF DEFENCE

DEFENCE ESTATE QUALITY MANAGEMENT SYSTEM

MECHANICAL ENGINEERING

MICROBIAL CONTROL IN AIR HANDLING AND WATER SYSTEMS OF DEFENCE BUILDINGS

August 2012

DOCUMENT STATUS

Version No. / Issue Date / Amendment Details / Amended by
1 / May 2012 / Draft for review and comment / TML
2 / July 2012 / Review comments incorporated / TML
3 / Aug 2012 / DEMP review comments incorporated / TML
4 / Aug 2012 / Version issued for publish / TML

CONTENTS

1.0INTRODUCTION

1.1Aim

1.2Sponsor

2.0POLICY OBJECTIVES AND PRINCIPLES

2.1Policy Objectives

2.2Policy Principles

3.0APPLICATION

4.0STANDARDS GUIDELINES AND CODES OF PRACTICE

4.1Standards Codes Regulations and Legislation

4.2Guidelines and Application Manuals

5.0DEFINITIONS

6.0LEGIONELLA BACTERIA

7.0MICROORGANISM MANAGEMENT AND CONTROL

8.0COOLING WATER SYSTEMS

8.1Approach to Maintenance

8.2Prescriptive Maintenance Requirements

8.3Performance-Based Maintenance Requirements

8.4Existing Equipment Upgrade

8.5Intermittent and Seasonal Equipment Use

8.6Start-Up and Shut-Down Instructions

8.7Retention of Records

9.0WATER SYSTEMS

9.1General

9.2Water Treatment Products

9.3Proprietary Water Treatment Devices

10.0AIR HANDLING SYSTEMS

10.1General

10.2Prescriptive Maintenance Requirements

10.3Performance-Based Maintenance Requirements of Air Handling Systems

11.0CERTIFICATION

12.0REPORTING OUTBREAKS AND HIGH RISK EVENTS

13.0DECONTAMINATION CLEANING AND DISINFECTION

14.0GUIDANCE

1.0INTRODUCTION

Microorganisms are present in almost every environment found on earth including within buildings. Microorganisms are normally present in relatively low concentrations within buildings and are found on surfaces and on airborne dust and aerosol particles.

The primary purpose of this Defence policyis to:

  • Assist in the control of microorganisms in systems provided for Defence buildings which are associated with health hazards such as the bacterial genus Legionella.This bacterial genus can cause infections which lead to Legionnaires' disease, hypersensitivity pneumonitis, humidifier fever and Pontiac fever.
  • Assist in the control of other heterotrophicmicroorganism sources which can lead to health hazards, such as Pseudomonas(e.g. causing skin rashes or ear infections), amoebic meningitis, herpes, Chlamydia and gastro-intestinal infections.
  • Reinforce and support Defence’s commitment to compliance with its obligations under Work Health and Safety (WHS) legislation.

1.1Aim

This policy aims to assist achieving Defence’s objectives and principles by providing general and specific guidance on microbial control in air-handling and water systems of Defence buildings.

1.2Sponsor

This document is sponsored by Directorate of Estate Engineering Policy (DEEP) on behalf of the Technical Authority Assistant Secretary Environment and Engineering (ASEE). Enquiries may be directed to:

Director Estate Engineering Policy

BrindabellaPark (BP-2-B049),

Canberra ACT 2600

Tel: (02) 6266 8178 Fax: (02) 6266 8211 Email: DSG - ID Engineering

2.0POLICY OBJECTIVES AND PRINCIPLES

2.1Policy Objectives

This policy provides general and specific guidance on matters which shall be considered by Service Providers in relation to microbial control in air-handling and water systems provided for Defence buildings, to assist Defence achieve its compliance objectives.

2.2Policy Principles

The principles described in this document shall be used in implementing the policy objectives.

3.0APPLICATION

The policy described in this document shall apply to Defence buildings which include:

  • Cooling water systems as described in SAA/SNZ HB32 and defined in AS/NZS 3666.1:2011.
  • Air-handling systems in buildings excluding refrigerated room airconditioners.
  • Condensate drainage equipment and air filters for non-ducted split system airconditioners.
  • Air conditioning plant.
  • Evaporative cooling, evaporative condenser and closed-circuit cooling systems.
  • Humidifying systems.
  • Water storage systems associated with potable water, fire sprinkler systems, and irrigation.
  • Hot, warm and cold water supply systems.
  • Heated pools, spa pools and hydrotherapy pools.
  • Cooling water systems for refrigeration equipment and air compressors, industrial heat exchangers, spray irrigation systems, industrial type fluid cooling systems.

The sources of legionellae which have generally been implicated in worldwide outbreaks of Legionnaires’ disease have been identified with air conditioning systems and cooling water systems which have been incorrectly commissioned or inadequately maintained. Consequently, Defence Estate Management, Defence personnel and Defence Service Providers shall be aware of their responsibilities and duty of care obligations associated with design, supply, installation, commissioning, operation, cleaning and maintenanceof air-handling and water systems in order to eliminate the health risk associated with microorganism infections.

This policy and related standards apply to all existing, new and replacement Defence plant. The policy shall be read in conjunction with:

  • DEQMS Work Health and Safety.
  • Commonwealth legislation.
  • RelevantState and Territory legislation.
  • Regulatory authority requirements.

The term ‘buildings’ as used in this policy in phrases such as ‘air-handling and water systems of buildings’ shall be read as also applying to Defence facilities and installations other than buildings where air-handling and water systems are installed independently of buildings. Such applications may be part of Defence industrial, process, testing or similar applications.

For the purpose of this Defence policy:

  • ‘Shall’ indicates a mandatory policy statement.
  • ‘Should’ indicates a policy recommendation.
  • ‘May’ indicates a course of action that is permissible; and the existence of an option.

4.0STANDARDS GUIDELINES AND CODES OF PRACTICE

4.1Standards Codes Regulations and Legislation

Microbial management and control for Defence buildings shall comply with all applicable standards, codes,regulations and legislation including but not limited to the following.

  • The Work Health and Safety (WHS) Act 2011.
  • WHS Regulations and WHS Safety Codes of Practice.
  • National Construction Code (NCC) Volume One – Building Code of Australia (BCA).
  • AS 1657:1992 Fixed platforms, walkways, stairways and ladders – Design, construction and installation.
  • AS 1668.2-1991 The use of mechanical ventilation and air-conditioning in buildings. Mechanical ventilation for acceptable indoor-air quality.
  • AS/NZS 1715:2009 Selection, use and maintenance of respiratory protective devices.
  • AS/NZS 1716:2012Respiratory protective devices.
  • AS 2610.1-2007 Spa pools – Public spas.
  • AS/NZS 2865:2009 Confined spaces.
  • AS 3498 - 2009 Authorization requirements for plumbing products - Water heaters and hot-water storage tanks.
  • AS/NZS 3666:2011 Air-handling and water systems of buildings - Microbial control.

Part 1: Design, installation and commissioning.

Part 2: Operation and maintenance.

Part 3: Performance-based maintenance of cooling water systems.

Part 4: Performance-based maintenance of air-handling systems (ducts and components).

  • AS/NZS 3500 Plumbing and drainage.

Part 1: Water services.

Part 4: Heated water services.

  • AS/NZS 3896:2008. Waters—Examination for Legionella spp. including Legionella pneumophila.
  • AS 3979-2006 Hydrotherapy pools.
  • AS/NZS 4276 Water microbiology.
  • State and Territory statutory laws and related codes of practice and guidelines.

4.2Guidelines and Application Manuals

The following documents provide relevant guidance.

  • Defence Safety Manual (SAFETYMAN).
  • Defence Incident Report Form AC 563. To be used in the event of an incident or accident and available through DEQMS Support, OH&S, Forms.
  • SAA HB9 - 1994, Handbook – Occupational personal protection.
  • SAA/SNZ HB32:1995 Control of microbial growth in air-handling and water systems in buildings.
  • National Environmental Health Forum Monographs. Water Series No. 1. Guidance for the control of Legionella. 1996.
  • AIRAH Application Manuals. DA17 – Cooling Towers.DA18 – Water Treatment.DA 19 HVAC&R Maintenance, DA26 – Indoor Air Quality.
  • ASHRAE Handbook – HVAC Applications. Chapter: Water Treatment.
  • AIRAH Best Practice Guidelines – HVAC Hygiene.
  • Guidance material provided by Comcare.
  • Guidance and mandatory requirements of safety data sheets provided for water treatment chemicals and biocides.
  • ASHRAE Guideline 12-2000. Minimizing the Risk of Legionellosis Associated with Building Water Systems.
  • ANSI/ASHRAE Standard 188P: Prevention of legionellosis associated with building water systems.

5.0DEFINITIONS

For the purpose of this policy the following definitions apply.

Automatic Bleed-Off Equipment

Equipment which removes water from a system to limit the concentration of total dissolved solid and suspended solids.

Automatic Dosing Equipment

Equipment which automatically doses cooling water systems with biocides and water treatment chemicals to control microbial growth, corrosion, scaling, fouling and the build-up of solids.

Biofilm

A layer of microorganisms formed as a thin slime on surfaces in contact with water.

Cooling Water System

A heat exchange system comprising heat-generating plant, water-based heat rejection plant and interconnecting recirculating pipework and associated pumps, valves and controls.

Cycles of Concentration

The degree of concentration of the dissolved solids of the cooling system make-up water as a result of the evaporation that takes place in the cooling tower.

Dead-leg

A section of a water-based system that does not permit the circulation of water.

Drift

Water lost from a cooling tower, evaporative condenser or similar equipment as liquid droplets entrained in the discharge air. This excludes condensation.

Drift Eliminators

Inertial moisture droplet stripping devices fitted to cooling towers and evaporative condensers to remove moisture droplets entrained in the discharge air.

Evaporative Air-Cooling Equipment

A device that effects a reduction of the dry bulb temperature of air by evaporating water into air.

Evaporative Condenser

A heat exchanger in which refrigerant is cooled by a combination of air movement and water spraying.

Heterotrophic Microorganisms

Microorganisms thatobtain nourishment by digesting plant or animal matter, as opposed to photosynthesizing food, as plants do.

High Risk Event

An event that could reasonably be expected to significantly or adversely affect public health.

Humidifier Fever

A form of allergic reaction caused by inhalation of allergens of microbial origin arising from the wetted surface of equipment, such as humidifiers.

Hypersensitivity Pneumonitis

Respiratory illness usually caused by inhalation of the spores or antigens of various different types of microorganisms.

Key Performance Indicator

A risk factor that is identified as testable, assessable and controllable for the performance, monitoring and verification of the system.

Legionnaires’ Disease

A potentially fatal illness characterised by pneumonia and cause by infection with Legionella bacteria species, commonly L.pneumophila. All infections caused by Legionella species are covered by the general term ‘legionellosis.’ (Legionnaires disease is a notifiable disease in each State and Territory).

Pontiac Fever

A self-limiting, short-duration, non-fatal fever caused by Legionella bacteria.

Regulatory Authority

Any authority that is authorised by statute to exercise jurisdiction over matters such as the design, materials, installation, commissioning, operation or maintenance of any part of an air-handling or water system, plant, equipment or systems covered by this policy.

Significant Modification

A modification to a warm water or air handling system falling within the meaning of AS/NZS 3666 that directly affects the hazard potential of the equipment.

6.0LEGIONELLA BACTERIA

Legionella bacteria are widespread in nature and can be found in a variety of environments including most fresh water, natural and constructed water sources, fresh or brackish water, coastal waters, mud and soil, in potting mixes and in compost. Consequently, it is to be expected thatLegionella bacteria will be present in building air-handling and water systems.

Legionella thrives in particularenvironments, which are outlined below:

  • In warm water Legionella bacteria:

Remain dormant at lowtemperatureand growth below 25ºC is rare.

Multiply in the temperature range of 20ºC to 45ºC with the optimum range being 35ºC to 37ºC.

Growth ceases above 45ºC and the bacteria dies with increasing rapidity as temperature rises above 45ºC.

Are killed by longexposure at 50ºC temperature and by shorter exposure at higher temperatures.

Are killed almost instantly at 70ºC.

  • The presence of sediment, sludge, scale and organic materialact as nutrient sources and provide a surface forattachment.
  • Some materials, such as natural rubber used for tap washers, are a known nutrient source. Care is required in their use and application.
  • Presence of waterborne microorganisms, such as algae, amoebae and other bacteria can provide nutrient sources.
  • Algal slimes provide a stable environment for growth.
  • The bulk of the microbial population in any water system is present in the biofilms which cover all wetted surfaces. On these surfaces, traces of nutrient are absorbed and aggregate and thereby sustain those passing microbes which settle and adhere to them. A biofilm is built up comprising a mixed population of interdependent microbial species embedded in a matrix which supports and protects them. Legionella hasbeen shown to be a biofilm organism andthrives in biofilm. Consequently,biofilm formationcan protect legionellae from concentrations of biocide that would otherwise kill or inhibit growth.
  • Dead legs in piping systems (i.e. sections of the system that do not allow water circulation) provide niches for growth.
  • Temperature stratification in calorifiers can provide locations suited to legionellae growth.
  • The growth of the bacteria is very responsive to the presence of iron and zinc such as occurs in unprotected, rusting galvanised iron construction material in wet cooling tower environments.
  • The presence of oxygen and carbon dioxide.

In their natural environments legionellae obtain theirrequirements for growth and proliferation (i.e. cell division) through interactions with other microorganisms such as algae, protozoa and other bacteria, and by the utilisation of organic and inorganic material.

Legionellae are parasitic and can infect freshwater amoebae and multiply within them. The persistence of legionellae within amoebae provides a means for dispersal and survival in ambient air conditions which would normally kill them. Amoebae can also protect parasitic legionellae from disinfection.

Legionellae also proliferate within biofilms,within other microorganisms and their by-productsand within matter entrained in water systems.

Design, installation, operation and maintenance of air-handling and water systems for Defence buildings shall consider the above matters when establishing appropriate control measures against microbial growth including Legionella bacteria.

New and replacement equipment and systems shall be selected, designed, manufactured, installed and operated on the basis of eliminating environments which aresusceptible to the uncontrolled growth and proliferation of Legionella bacteria. Consideration shall be given to associated factors such as the location of the equipment and systems, construction materials, and maintenance requirements including provisions for cleaning and water quality monitoring.

7.0MICROORGANISM MANAGEMENT AND CONTROL

Defence Manager Estate and Facilities Services (MEFS) shall ensure that Service Providers responsible for the maintenance of air-handling and warm water systems develop and keep current,compliant plans for the management and control of microorganisms in the maintained systems. Plans shall include appropriate maintenanceand operation instructions that are to be recorded in the Garrison and Estate Management System (GEMS).

Maintenance Service Providers shall ensure management and control of microbial growth arein full compliance with the requirements of regulatory authorities, State and Territory Health Departments, and local municipal authorities.

Maintenance and operatinginstructions shall as a minimum comply with the requirements of:

  • The above authorities.
  • The applicable requirements of the Standards and documents covered under clause 4.0.

Maintenance instructions shall include mandatory procedures for the use of personal protective equipment, for handling ofchemicals and for working in confined spaces.

Microorganism management and control shall allow for the possible development of microbial resistance to specific biocides and biocide formulations. Service Providers shall regularly alternate biocides to reduce the risk of resistantstrains of microorganismsbeing developed.

Care shall be taken in the use of biocides, cleaning agents and any other chemicals in air-handling equipment such as humidifiers, spray coils and evaporative air cooling equipment. Chemicals may be hazardous to health when entrained in the airstream. Suppliers’ recommendations, including safety data sheets and other information shall be followed to ensure the proper use of chemicals.

8.0COOLING WATER SYSTEMS

8.1Approach to Maintenance

The biological process of rapid growth of Legionella bacteriain water systems to high concentrationsis essential before the water systems are considered potentially hazardous and capable ofcausing the serious and potentially fatal illness legionellosis. Consequently, effective control of the growth process is fundamental to addressing the potential hazard and this is achieved by effective maintenance and compliance with applicable legislation, codes, standards and regulatory authority requirements.

The design of water systems shall facilitate maintenance, cleaning, control of microbial growth, and minimising drift from the heat rejection plant. This shall be achieved by compliance with the applicable requirements of Clause 4 Standards, Guidelines and Codes of Practice.

Parts 2, 3 and 4 of AS/NZS 3666:2011 include prescriptive and performance-based approaches to maintenance of air-handling and water systems of buildings. Defence presently requires a prescriptive-based approach to maintenance of cooling water systems where the maintenance actions are prescribed and in accordance with AS/NZS 3666.2:2011. However, in some situations a performance-based approach may be necessary for reasons described under 8.3 below. Where a performance-based approach is required for a specific Defence system AS/NZS 3666.3:2011 shall apply and associated water quality management and testing regimes shall be in place and strictly followed. Under the performance-based approach Defence relies upon the expertise of Service Providers to assess and recommend the most appropriate approach to maintenance for a particular application based on their professional experience and technical competence.

Irrespective of the prescriptive or performance-based approach to maintenance, in the event of an outbreak of Legionnaires’ Disease or water sampling results that identifyactionable microorganism quantities (for legionellae or heterotrophic microorganisms as determined byAS/NZS 3666.3:2011 Tables 3.1, 3.2)immediate notification to Defence is required together with special action as determined by the Standard and as advised by the local health authorities.

8.2Prescriptive Maintenance Requirements

Section 2 of AS/NZS 3666.2:2011 covers a prescriptive approach to operation and maintenance of air-handling and water systems of buildings. Clause 2.5 describes a prescriptive approach to maintenance of cooling water systems.Typically, Service Providers should follow this approach where systems can be shut down without adversely affecting Defence capability, continuity of service or process, or the Defence facility being served.

The prescriptive maintenance requirements of AS/NZS 3666.2:2011 Section 2 includes minimum inspection and cleaning periodswhich in the case of cooling water systems is inspection at least monthly and cleaning as necessary with intervals not exceeding six months.