Tuesday, January 23, 2007

Potable Recycling in Colorado

I don’t usually re-post articles straight from newspapers here. However, I thought some readers might find this one from the Denver Post interesting.

Notable is the fact that the city planners, the water authorities and the Colorado Department of Public Health and Environment are all keen to promote what we would call an ‘unplanned’ or ‘incidental’ potable water recycling scheme. In Australia, some State Governments would play it down or pretend not to notice. Some community members call it ‘bad practice’ and would have you believe that US agencies are opposed to it.

Tapping used water
By Jeremy P. Meyer
Denver Post, 23 January 2007.

The city of Aurora is working on a $754 million project to extract water from the South Platte River, treat it and pipe it to customers - a process that will increase Aurora's water supply by 20 percent.

Snowmelt running down mountainsides and into reservoirs has been Aurora's main source of drinking water - as it has been for other Front Range cities.

In three years, residents of the Denver metro area's second-largest municipality will get recycled water out of their taps.

The city's $754 million Prairie Waters Project will draw South Platte River water downstream from the Denver Metro Wastewater Reclamation District's plant.

The river water will be sent through sand and charcoal filters, treated with chemicals and zapped with ultraviolet light.

"This is the wave of the future," said Glenn Bodnar, drinking-water specialist for the Colorado Department of Public Health and Environment.

"The way Colorado is growing and the finite amount of pure water we have, water systems are going to be looking for additional sources of drinking water," Bodnar said. "Aurora is leading the charge."

The water will be pulled from the river near Brighton, sent 34 miles south to Aurora, treated in the 40-day, six-step process, and ultimately blended with the mountain water.

Prairie Waters was created when the city faced the risk of running out of water in 2003 after a persistent drought.

Lack of snowfall and rain in the mountains left Aurora's reservoirs with only a couple of months' supply as the summer season approached.

Aurora Water director Peter Binney, who had been in the job for a year, said he never wanted to go through that kind of a crisis again.

"You don't want to be running a large water system with that kind of vulnerability," Binney said.

(Click to enlarge)

Deals with farmers were arranged for their water rights, and the city looked at 54 plans to get more water to the city.

Prairie Waters - the first large-scale water-reuse project in Colorado and the state's first big water project in 40 years - became the No. 1 choice.

"It's really setting up a water machine that is as close to a perpetual-motion machine as you can get," Binney said.

While the system of diverting mountain water to the Front Range has allowed eastern Colorado to prosper, it also has pitted the Western Slope against the Front Range, farmers against city dwellers, and water managers against environmentalists.

The reuse approach of Prairie Waters, some say, is one way to broker peace in the water wars.

"It's an approach no one has taken in Colorado," said Aurora Mayor Ed Tauer. "We've spent in this state decades fighting about water."

Environmental groups are still scrutinizing Prairie Waters but have given their initial approval.

"This is a progressive way to meet new water needs," said Bart Miller, water program manager for Western Resource Advocates. "We're very encouraged because of what it's not doing - another transmountain diversion."

The project is slated to be completed in 2010, boosting the city's water supply by 20 percent.

The city's 300,000 customers are already picking up the tab, paying an average of 12 percent more on their bills this year and an additional 12 percent next year.

Tap fees have risen from $6,711 per home to $16,641. Aurora also plans to sell bonds later this year for the project.

"The one downside is the project will be expensive," Tauer said. "But it will be cheaper to do it now than in 20 years."

In drought years, junior water users downstream - particularly farmers and others with wells - may be forced to leave fields fallow if Aurora uses all of its 10,000 acre-feet in the Prairie Waters system, Binney said. An acre-foot, which is the amount of water that would cover one acre to a depth of one foot, is generally believed to be enough to serve the needs of two families of four for a year.

The quality of the drinking water will also remain a challenge.

"The water that they will begin with will be of lesser quality than what we divert or what Aurora diverts," said Chips Barry, manager of Denver Water, the state's largest water company. "Now, it hasn't been through someone else's kidneys. They will have to do more advanced treatment than if it were pure snowmelt."

That is the reason Aurora is using a six-step process, when only two steps are needed to meet state and federal drinking- water standards, city officials say.

The goal is to make the reused water indistinguishable from the current supply.

Aurora's water currently has a total dissolved-solids concentration of 200 parts per million.

Officials want Prairie Waters to produce water with a maximum of 400 parts per million TDS concentration - which they say cannot be detected.

"They are setting a precedent," said Bodnar. "If cities want to continue to grow, and people are still looking for water to serve those additional folks, we're going to have to be creative. This sets the bar."

13 comments:

Greg said...

That has to be rock bottom doesn't it!. Lets fail to build significant water infrastructure to cater for population growth, wait for a drought to come along and then take full advantage of it by creating a scheme that will permanently mix recycled water with snowmelt and then up the cost of providing consumers with the water by around 300%. Disgusting!

Greg said...

I guess some people will not be drinking that water.

desal boy said...

Stuart, are politics taking over up north with the deputy premier saying she will put up to 100% recycled water into homes. That can't be the best way to convince people to accept recycled water. Where's the consultation and education?

Stuart Khan said...

Hi Desal Boy,

Maybe I’m the silly one, but it seems to me that three quarters off Queensland has misread or misheard what was said by Ms Bligh. From today’s Courier Mail:

Admitting the region faced a water crisis, Acting Premier Anna Bligh yesterday revealed there would be no percentage cap to recycled water if the March 17 plebiscite was passed.

"The advice we have is this water, purified and treated to the appropriate level, is 100 per cent safe," she said.

Ms Bligh's comments are in stark contrast to the plebiscite's announcement in December when Premier Peter Beattie mooted a 10 per cent cap.


Interpret this as you will, but to me she simply seems to be saying that they will not set a cap on the ultimate percentage and that the justification for this is because any proportion can be treated to a level that is safe.

Although it is not explicitly stated in the LGAQ report, I think this is a reasonable interpretation since most of the studies quoted involved the analysis of 100% recycled water (prior to delivering it to aquifers or surface waters).

Interestingly comments on the Water Futures blog and the 4350 Water blog seem to mistake the use of 100% recycled water with ‘direct potable reuse’. The difference between ‘direct’ and ‘indirect’ potable reuse has nothing to do with the percentage. ‘Indirect’ is defined by the fact that the water is returned to a surface or groundwater system and then further treated in a drinking water treatment plant.

The only direct potable water recycling plant in the world is at Windhoek, Namibia. The proportion of recycled water supplied at that plant is not 100% (I think it’s a bit more than 30%).

In fact, trying to use 100% at a ‘direct’ recycling plant would be extremely difficult. There are a number of reasons for this, but an obvious one is that you would need to produce (at least) the same amount of recycled water as there is demand for potable water. However, only about half the potable water that most cities use is returned to the sewage system and the remainder used outdoors. The deficit would have to come from somewhere or you would soon run out (unless the catchment was at least twice the size of the service area). In practice, this limits the ultimate percentage to little more than 50%.

I think the suggestion that 100% is an acceptable ‘upper cap’ is a perfectly reasonable way of saying ‘there is no upper cap’.

Anonymous said...

You are just too smart by half.
Anna Bligh made the statement on TV channel 10 News and she said that they would put 100% of recycled water back into the dam!
It's on tape if you need to review it. There is no mistaking in her government's intent.

All the Beattie camp has achieved is that the community is certain that they do not want 100% treated sewage water into their dam.

It is incredible that you would make these statements now, when during the Toowoomba campaign experts claimed that 25-29% was considered high by world standards.

Please show us your examples.
Lets not use a third world country example as we deserve better than that.
You and your ilk forget that we have made a study of this subject and can not be so easily be conned.

desal boy said...

Didn't see the ABC News but people I spoke to up north said Bligh did say she would be happy putting 40%, 80% in the drinking water supply.

friend of the blogger said...

Surely a indirect potable use scheme at 100% is effectively a direct potable use scheme.

Stuart Khan said...

Hello Anonymous,

Since I didn’t see the news story that you refer to, I’ll have to take your word for what was said. However, I’m fairly confident that what was meant was that the QLD Government will not be setting a cap on the maximum ratio of recycled water that may be in the dam at any particular time. To achieve anything approaching 100%, there would have to be no run-off from any other sources for a sustained period of time. It would be practically impossible in a dam the size of Wivenhoe. I can assure you that it is not my intention to ‘con’ anybody.

Desal Boy,

Yes…that is what was written in the AAP press release that most of the news stories used. I found a copy on an online database, but can’t seem to locate one that is freely available on the web. The quote (complete with the trailing dots) is: “The advice we have ... this water is 100 per cent safe, so it doesn't matter whether (the level) is one per cent, or 40 per cent or 80 per cent.”. I accept that this must be a different quote to the one referred to by Anonymous, above.

Hello ‘Friend of the Blogger’,

No. The percentage does not define whether a scheme is ‘direct’, ‘indirect’ or even ‘effectively direct’. This is an important point and I am not just playing with semantics. The term ‘indirect potable reuse’ has been used in the USA since the 1970s and has a fairly definite meaning with a number of implications. An important component is the ‘multiple barrier’ principle and two of the important barriers include detention in an environmental system and subsequent treatment in a drinking water treatment plant. When people say that they support indirect potable reuse but do not support direct potable reuse, it is the maintenance of these multiple barriers that they are referring to. They are not referring to the percentage of what that they consider to be safe or unsafe.

friend of the blogger said...

Even Senator Bartlett thinks Bligh said that:

He says the plebiscite on March 17 is no longer necessary, because of Anna Bligh's statement that the government will pump up to 100 percent recycled water into our dams in an emergency.

friend of the blogger said...

But if the dam is empty, where is the detention in an environmental system?

Anonymous said...

we are still waiting for the examples.
We need a Mayor and an engineer from a city who deliberately put recycled sewage water straight into their main drinking supply which is a still body of water i.e. a dam.

Stuart Khan said...

Hello FOTB,

Yes, as I mentioned, three quarters of Queensland seems to have heard/read it that way. However, I do find it slightly strange that Ms Bligh could make a statement that they plan to provide 100% recycled water and no print media has considered it significant enough or sensational enough to quote her directly. But Bartlett’s statement is even stranger…of course they would pump 100% recycled water INTO the dam…surely the question is what proportion they pump OUT of the dam…

The dam would not be empty if they are pumping recycled water into it. That is the detention point, then it comes out again and is treated at a drinking water treatment plant. That is simply not direct water recycling.

Furthermore, it would be extremely difficult to reach 100% recycled water in the dam. There would have to be no run-off for months and the city would be perilously close running out of water. It would never be achieved even if Anna Bligh wanted it to. SEQ’s problem is not so much that there is no run-off into dams (there is)…the problem has much more to do with population growth causing demand to outpace supply.

However, I do believe all of this is rather irrelevant, because it is still my opinion that the message that Anna Bligh was (clearly?) trying to get across was that the QLD Government would not set a maximum limit because any proportion is safe.

Stuart Khan said...

Hello Anonymous,

I’m afraid I can’t name any mayors or engineers as you have requested. I apologise if this is important to you. However, a good example of reservoir that is a key drinking water source (to the City of Washington DC) is the Occoquan Reservoir (Virginia, USA). This is deliberately charged with recycled water from an advanced water treatment plant operated by the Upper Occoquan Sewage Authority.

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