Using Recycled Water for Drinking

The Australian Government’s National Water Commission (NWC) released a report titled ‘Using Recycled Water for Drinking’ this week. It is publicly available from the NWC website.

The report was prepared by GHD and released as the second Occasional Paper from the NWC’s Waterlines series. It is preceded with a short section describing the NWC’s position on the topic of indirect potable recycling (IPR). This states that the NWC believes that IPR is an important option to improve Australia's long-term water security. It says “The Commission strongly encourages objective and even-handed consideration of IPR as one option for communities to augment their water supplies and to enhance their water security and urges leadership by water decision-makers throughout Australia to enable recycled water for drinking to be considered and implemented.”

On the key issue of risk, The NWC states that it “recognises the risks associated with recycled water for drinking but considers that these risks can be satisfactorily and safely managed. It also emphasises the importance of sound, consultative community decision-making processes, well informed by science and evidence.”

As has become the habit of this blog, the executive summary is pasted below. However the full report is written in very accessible language and well worth reading.

I’d be interested in discussing the details further.



Executive Summary

This discussion paper explores the use of recycled water to supplement drinking water supplies in Australian towns and cities.

This concept involves introducing highly treated recycled water to blend with the source water of an existing water supply. This option may compare favorably with other options to supplement water supplies, but it has only recently formed part of long-term water supply plans in Australia.

Because most of Australia’s towns and cities are sewered, this option is available to most communities. Recycling water for other purposes is happening but is restricted to lower volumes unless new dual pipe systems are added to existing suburbs and houses. Using recycled water to supplement drinking water supplies offers a substantial future water resource for most of our towns and cities. This concept has generated considerable community and industry interest, most notably with the referendum in Toowoomba (July 2006) and the larger scheme for Brisbane which is due to come on line in 2008 to 2009.

The following observations are intended to provide a brief summary of the concepts and ideas in this paper. Each of these observations is explored in more detail in the paper.

This paper is intended for those who are interested in the use of recycled water to supplement drinking water supplies and is not intended to provide a definitive position on this option. The question of water quality and risk to public health is addressed briefly in this primer as it is often raised in relation to this option.

The Environment Protection and Heritage Council (EPHC) and Natural Resource Management Ministerial Council (NRMMC) initiated the development of National Guidelines for Water Recycling (Phase 1, 2006). A second phase of the Guidelines is currently under development and will include the use of recycled water for drinking. More information about these Guidelines are at www.ephc.gov.au/ephc/water_recycling.html.

Background

Introducing recycled water of drinking water standard into the drinking supply source is sometimes referred to as ‘indirect potable re-use’ (IPR). ‘Potable’ is a term used to describe water suitable for drinking. It is ‘indirect’ because it is sent back to mix in with the source water as opposed to introducing the recycled water directly into the drinking water system.

There are many existing water supply systems in Australia and around the world where recycled water enters the source water supply upstream of the off-take for a drinking water supply. This is sometimes referred to as ‘unplanned’ indirect potable re-use. Many towns and cities are already using water sources that contain recycled water. Usually, this is recycled water from some other town or city upstream.

This paper discusses ‘planned’ recycling, where recycled water from a town is sent back to the source for that town. There are around 10 operating or proposed ‘planned’ schemes around the world. Some often-quoted schemes are located in Singapore, Namibia and California.

Queensland and ACT Governments have announced their intention to pursue large scale water recycling to augment drinking water supplies (24 April 2007). The Western Corridor project will be the largest ‘IPR’ scheme in the southern hemisphere and will involve the construction of pipelines to enable the transfer of purifed recycled water from advanced wastewater treatment plants in Brisbane and Ipswich to end users throughout south-east Queensland.

How does the use of recycled water compare to other water supply options?

Until recently, the use of recycled water for drinking water purposes has not been considered in detail in the majority of long-term water supply plans in Australia. However, the degree of interest is increasing rapidly due to current concerns over the future supply of water to our cities. For example, in 2006, the Water Services Association of Australia (WSAA), the peak body of the larger urban water authorities, released a paper that discusses recycling to supplement drinking water, and includes 10 points for consideration (WSAA Position Paper No 2 2006).

Analysis of potential economic and environmental factors shows that there will be cities and towns where the use of recycled water to supplement drinking water supplies compares favorably with other options. This is most likely to occur when the existing wastewater treatment plants are producing high quality water, and are located relatively close to the current sources of water compared to other options.

Using recycled water to supplement drinking water supplies may also have environmental benefits such as reduced energy use and reductions in volumes of waste discharged to the environment compared to other water supply options. Note that depending on circumstances, the remaining waste stream may be more concentrated and contain the same total load of contaminants.

So in some circumstances, using recycled water can have benefits compared to other options. However, understanding whether these potential benefits actually apply to any particular town or city requires a detailed analysis because the costs and environmental impact are unique for each location and water supply system.

What are the risks and how are they managed?

It is reasonable to be concerned about the introduction of recycled water into water supplies. Untreated recycled water can contain contaminants that pose a risk to human health. These risks are proposed to be managed using advanced treatment technologies such as reverse osmosis (which is also used to desalinate sea water) to provide highly treated water, and also by careful operation and management of the entire system.

Schemes typically involve some detention time in either a reservoir or underground aquifer, which is sometimes called the environmental buffer. Processes in reservoirs and aquifers such as detention time and microbial action assist in managing the risks.

Managing risk from a technical point of view involves more than just advanced water treatment. Risk management when introducing treated recycled water into the water supply system extends from the water source (discharges to the sewers) to the customers’ taps. This will include management of risks at the water source, operation of treatment plants, appropriate institutional arrangements, and research and development to keep up to date with best practice. This approach to risk management is outlined in the Australian Drinking Water Guidelines (ADWG) framework for managing drinking water supplies (NRMMC, EPHC and the Australian Health Ministers Conference (AHMC), 2006).

Some specific areas of risk management such as understanding and controlling discharges to sewers, and the extent and nature of the environmental buffer required, can be as important as the treatment process in managing the risk, and in the implications they have for scheme costs and viability.

In Australia, guidelines for using recycled water to supplement drinking water supplies are currently under development. A risk-based approach is being used which has been successful at managing risks in existing drinking water supplies. The guidelines will be crucial in providing an authoritative and balanced view of how to manage the risks associated with adding recycled water to drinking water systems.

Community views

Despite the potential economic and environmental benefits, the use of recycled water to supplement drinking water supplies is sometimes excluded from water supply options analysis based on the perception of community concerns. Social research indicates that a majority of people like the idea of using recycled water in general, however a smaller proportion of people support or accept the idea of use in their drinking water supplies. People are more comfortable with recycled water use outside their homes, rather than in their drinking water.

Research on risk communication has developed lists of factors that often lead to community concern. These concerns are not necessarily ‘technical’, but may be more intuitive and reactive.

There appear to be at least two key psychological factors. First, some people have a reaction of disgust at the idea of using water from this source.

Technical discussions about risk and purity after treatment may not be of interest to people with this reaction. Secondly, some people are more comfortable if they believe the water is more ‘natural’, i.e. has spent some time in a river, lake or groundwater basin.

Communication with the community and scheme design needs to take these factors into account.

Conclusions

In conclusion, the use of recycled water to supplement drinking water supplies appears to offer a potentially appropriate option for some cities to access a significant new source of water that is independent of rainfall. This option may compare favourably with other options on an economic or environmental basis, but this can only be determined by a detailed analysis for each specific case.

Advanced water treatment technologies and new risk assessment techniques should allow water managers achieve the comprehensive risk management that is required to protect public health.

There will be community concerns, and these will need to be addressed through careful planning and a wide ranging approach. Technical education alone is unlikely to satisfy the community. Scheme design may also need to take community concerns into account.