Recycled water and cooling tower systems

There are many legislative requirements relating to cooling towers operating in Victoria. There are requirements that relate to registration, maintenance, testing and the development and auditing of risk management plans.

Many businesses with cooling towers are now considering ways to help reduce drinking water consumption, by either:

• using alternative water supplies in cooling tower systems
• recycling cooling tower bleed or waste water (also known as 'industrial water') for other purposes.

These alternative supplies include roof-collected rainwater, stormwater, recycled water that has been derived from greywater or sewage, and industrial waste water.

Alternative water supplies in cooling towers

With appropriate management controls, alternative water sources can be used to supply or supplement cooling tower systems. The controls required will depend on the source of water used, and will need to address 2 key risk areas:

1. The alternative water supply enhancing the growth of Legionella in the cooling tower system.
2. Contaminants such as pathogens in the alternative water supply causing harm in individuals who are exposed to the water (either directly or via aerosols).

Responsibilities and risk management planning for Legionella

Owners and managers of cooling tower systems have responsibilities under the Public Health and Wellbeing Act 2008 and the Public Health and Wellbeing Regulations 2019. Of particular importance is the requirement to develop a risk management plan (RMP) that addresses nutrient growth and poor water quality.

We have developed a Guide to developing cooling tower risk management plans to assist industry in managing potential Legionella risks in cooling tower systems.

The RMP should include a specific assessment of the alternative water supply. It should be noted that using water from an alternative supply may result in an increased risk classification and subsequently change the operational program that is required.

The following tools and tips may also be useful:

• The Template for cooling tower system risk management plan can assist with evaluating the critical risks and how this translates to a risk classification.
• Table 4 in Section 8 treating the critical risks in cooling towers provides indicative water quality target ranges for cooling tower systems, which may assist in designing an appropriate water treatment program.
• The water treatment service provider for the cooling tower should be able to assist in ensuring the water treatment program addresses the water quality for the system.

Rainwater and stormwater

The use of roof-collected rainwater in cooling tower systems is addressed in the guideline Rainwater use in urban communities.

The National Water Quality Management Strategy provides a best practice framework for assessing and managing stormwater quality for recycling.

There are no specific regulatory or approval requirements for the use of rainwater or stormwater in cooling tower systems (aside from the general regulatory requirements relating to all cooling tower systems described above).

If stormwater is being considered for a specific cooling tower system, it is recommended that a suitable consultant or other appropriately-trained individual is engaged to undertake a specific assessment in accordance with these guidelines.

Recycled water from sewage or greywater

Recycled sewage that meets the water quality standards described in the Environment Protection Authority’s (EPA) Victorian guideline for water recycling is considered to be of a suitable quality for use in cooling tower systems. More information about these 2021 guidelines can be found on the EPA’s Guidance for water recycling in Victoria website page.

Proposals to recycle greywater for cooling tower system use may need a specific risk assessment to identify appropriate water quality standards. This can be undertaken using the principles in the National Water Quality Management Strategy. Email the department via legionella@health.vic.gov.au.

In some cases an approval for the treatment and use of recycled sewage and greywater is required. You should contact the EPA to discuss any approval requirements.

Use of cooling tower waste water

Bleed or waste water from cooling towers can sometimes be used for other purposes, such as toilet flushing, garden watering or other industrial processes. In some cases an approval is required for these types of industrial water recycling projects - contact the EPA for further information.

A risk assessment should always be undertaken to determine if any contaminants in the water (such as microorganisms or chemicals) will pose a risk to human health or the environment.

There is currently no guidance that is specific to cooling tower systems to assist in undertaking this type of risk assessment. However, the principles in the National Water Quality Management Strategy can be used.

It is recommended that a suitable consultant or other appropriately-trained individual is engaged to undertake a specific risk assessment if the use of cooling tower waste water is being considered.