Friday, June 16, 2006

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


Anonymous said...

Well, using recycled effluent for industry or agriculture would be a good step forward. People drinking water from dams do the least amount of usage. So potable use is really a waste of time, money and enrgey, considering it relies on an already stable supply of waste water.

The amount of waste water would benefit farmers more then it would a city. The less farmers and industry draw from dams and catchments, the longer it will take for the supply to run low, even in harsh droughts.

IF the federal government vote to ues recycled sewerage as potable use, then they are signing thier death cetificates. It has already been blown up and the people of Australia are just not going trust the technology without decades of study.

Water is vital for survival, recycling it would need a BIG impact study on humans and environment before people accept it as drinking supply.

I for one do not, but for industry, farming, and a dual pipe system, YES. The cost of setting up such a system should not be an issue when the safety and integrity of a city or community is at stake.

When people start looking at the right sensible approach to recycling, only then will it be accpeted. As it is now, poeple won't even if it means running dry.

ADAM said...

Stuart, I agree that there are many ways that we can recycle water and each will come with specific advantages and disadvantages when compared to each other.

You are correct in stating that the best solutions will depend on a number of local factors and exactly what is intended to be achieved. For this reason, it is not possible to make sweeping generalisations about what is the best way to recycle water in all circumstances. It's horses for courses.

Anonymous said...

I'm all for recycled water, but not for filling up dams and drinking supply. Farmers would benefit much more then city drinkers will, and industry as well. It's time for people to STOP thinking about using recycled water for DAM supply and DRINKING.
It would not magiacally refil dams or stop them from dropping levels with no rain.

Stuart Khan said...

Hello Anonymous and Anonymous,

Thanks for your comments about alternative uses for recycled water. Your suggestions are perfectly valid. However, as I stated in the blog, we need to carefully consider what it is that we are trying to achieve in each specific circumstance.

Take, for example, the cities of Toowoomba and Goulburn. Is the goal to find more water for farmers and/or industry? If it is, then the municipal dams are probably not the best place to be looking. But in fact, the goal is to find water to sustain a growing population of humans. So finding new sources for agriculture and industry would only be of value if this could free-up other water to be redirected from these users back to the city dam. (I am aware of suggestions to do just that with groundwater in Toowoomba, but am not familiar enough with the specific circumstances to comment on the true viability).

It is true (as suggested above), that the amount of water that is actually consumed by people is a minor fraction of total water use. But we must remember that for a municipal water supply, the vast majority is used by households. Unless we are prepared to dig up all of our streets and lawns, existing areas are stuck with the plumbing that they already have. This means that regardless of what fraction of the water delivered to houses is actually consumed, all of it will need to be delivered at the same potable standard. Therefore, it is this potable supply that we will need to focus on if we wish to continue to sustain these rural Australian populations.

Snow Manners said...

Hi Stuart. Of course what you say makes sense. Although water is abundant on the planet municpal water is quite scarce and expensive to produce and as such is a valuable commodity.

Leaving aside all the emotive arguments I have heard to substantiate planned potable reuse the huge majority of people are aware of the need to make good use of water resources.

'Political courage' should not be the driving force behind water reforms because it will inevitably lead to some form of 'water war' (eg Toowoomba).

Planned potable reuse is an ideal to strive for but it can only ever be achieved through a multidisciplinary approach. The water scientists play a valuable role, obviously, because they have the engine.

If R&D hadn't been ploughed into membrane technology there wouldn't even be a debate. So simply because one of the disciplines involved feels thay now have the technological capacity to safely (and perhaps cost effectively) reclaim drinking water from used water doesn't logically lead to implementation tomorrow.

It is now time for the other disciplines to engage, research and play catch up.

The water industry has new technology and can't understand why the rest of the community isn't embracing it.

My advice is to be patient.

Encourage sponsors to invest time and money in other logically associated disciplines.

Stuart Khan said...

Thanks for this contribution Snow. I agree that a lack of technical ability is not the major impediment to increased practice of water reuse (although there is always room for improvement). I’d be very interested to know your thoughts on which ‘associated disciplines’ require the most urgent investment.

Greg said...

Sewage sludge treatment and disposal! Desalination! Dam catchment area protection! Groundwater replenishment! Waste stream disposal! and you could just make it rain cats and dogs because I am tired of seeing this and this and being told it's climate change!

Stuart Khan said...

Thanks Greg. I agree that these are all areas where improvements are needed (especially the rainfall!). I’d be interested to know more what you mean about groundwater replenishment; –Are you suggesting that as a form of potable reuse that might be more acceptable to communities (as occurs in California)? Or simply as a means to its own end?

Peter Jones said...

Hi Stuart

I hope what Greg means when he says 'groundwater replenishment' is to replenish existing surface water supplies with groundwater. Such as one of the alternatives that Toowoomba City Council have struck off the list as being 'not innovative enough.' Toowoomba is a bit unique being located smack on top of a mountain range which means getting any water in to the city involves pumping uphill. Just to the west of the city is a plentiful supply of near potable quality (I have actually drunk it myself as it comes out of the ground) ground water. It defies logic why TCC regard the offer from the Norwin farmers to exchange their groundwater allocations in return for Toowoomba's nutrient rich wastewater so they can water their cotton as 'not innovative.'

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