Is potable always best?

This is a question that I recently addressed as a witness to the NSW Parliamentary Inquiry into A Sustainable Water Supply for Sydney. I was quoted in the final report as saying:

“Indirect potable in some ways might be considered an ideal reuse approach because it means delivering water to one destination and having this one reservoir, or whatever, to retain the water and to treat it and put it back through the entire supply without having to implement a lot of major extra infrastructure. However, I wonder whether it really is the ideal approach in all circumstances. For example, it is a high-energy approach; it requires high treatment. All of that phosphorus and nitrogen that we are talking about discharging out of the outfalls has to be removed for indirect potable reuse. However, if we are looking at agricultural uses, maybe we can make use of some of the nutrients that are already in that water and not need to invest so much energy in upgrading it to a potable standard”.

The remainder of my quote did not make it into the final Inquiry report, but appears in the official transcript:

“Also, realistically speaking, Sydney’s water issues at the moment are urgent and they need to be addressed quickly, but are we going to see the political courage to implement an indirect potable reuse scheme in the short-term? I am not sure that we are. So I think maybe we should be looking at alternative forms of reuse, at least in the meantime, and forms of reuse that can supplement our drinking water supply; replace water that is currently potable water in our drinking water rather than having to put the recycled water directly back into the dams immediately”.

Although I didn't say it very clearly, I think you can get the gist of where I was coming from. I think these are reasonable comments and I stand by them (although I may be proved wrong about the lack of “political courage” in some circumstances!). Nonetheless, what is ultimately the best approach will depend on many local circumstances and exactly what is hoped to be achieved.

In these times of severe drought, it is easy to forget that many current water recycling schemes were never intended as a means of conserving drinking-water supplies. An obvious example is the Rouse Hill (Western Sydney) dual reticulation scheme. This scheme was planned with the sole aim of preventing a sensitive waterway from being polluted by treated effluent discharge. As a result, the current benefits of the scheme for conserving dinking-water are questionable. I don’t have accurate data to report, but it has previously been acknowledged that the use of the recycled water from Rouse Hill has been greater than the equivalent uses of potable water in other comparable areas. In fact, the recycled water use has been so great that the system has, on numerous occasions, had to be topped-up with potable supplies.

The residents serviced by the Rouse Hill scheme are prolific users of recycled water. And why wouldn’t they be? They pay only about one third of the price for water supplied through purple pipes compared to the price for water delivered via the potable supply system. This is regardless of the fact that the real (financial) costs of providing the recycled water to the scheme are significantly greater than the cost of providing potable water.

Indirect potable reuse provides a more direct benefit when it comes to supplementing potable supplies. It is also a considerably more economically viable solution.

But planned indirect potable reuse certainly has its down-sides. For example, I am aware that many people are concerned about potential public health risks. I am confident that such concerns are unfounded, but acknowledge that I will not convince all readers to share my confidence.

Toowoomba councillor, Lyle Shelton, recently commented on this blog that the current debate in that city has “ripped our community apart, it has divided friends”. This is a very significant social cost that must be recognised by all proponents of water recycling, -myself included. While I think open debate is extremely healthy, I sincerely hope to never see a replay of the acrimonious discourse now apparently permeating the Garden City.

During this week, we have heard plans from the Queensland State Government to build a pipeline to take recycled water from Luggage Point and deliver it for industrial uses, primarily electricity production. Some members of the community have expressed suspicion for the fact that the pipeline will pass very close to Wivenhoe Dam. I don’t know anything more than anyone else does, but to me this suggests excellent planning on behalf of the Queensland Government. In the short term, it frees up fresh water supplies for potable use. But it also leaves open the possibility for future potable recycling, should environmental conditions necessitate it and should the community eventually come to accept it as a viable solution to the challenges faced by much of South East Queensland.

I think it is prudent for scientists, public officials and community leaders to enhance efforts to provide accurate information to the community. Indirect potable recycling can offer significant benefits to some areas. But we need to be careful that the benefits we are promoting outweigh the inherent costs. Let’s do this properly and not tear communities apart in the process.

I'd be grateful to know your opinions