This week, the ACT Government launched a three-month period of community consultation to consider the merits -or otherwise- of developing a planned indirect potable water recycling scheme to supplement Canberra's drinking water.
The “Water2WATER” project would involve upgrading effluents from the Lower Molonglo Water Quality Control Centre to potable quality so that they may be then be placed back up into the catchment of the Cotter reservoir. The ACT water authority, ACTEW is currently investigating which combination of technological barriers would be the best option but the decision has not yet been announced. From the Cotter reservoir, the water would be treated again at the Mt Stromlo drinking water treatment plant before being distributed to customers.
The proposal has received tri-partisan in-principle support from the governing ACT Labor Party, ACT Liberals and ACT Greens. However, like all planned indirect potable recycling schemes, it is sure to have its sceptics and detractors.
The most high profile ACT opponent to voice concerns so far is Professor Peter Collignon. Prof. Collignon is the director of infectious diseases and microbiology at the Canberra Hospital, and a Professor at the School of Clinical Medicine, Australian National University. As an eminent and highly respected expert in his field, Prof. Collignon’s concerns must be taken extremely seriously.
I expect that Prof. Collignon has or will formally present his position as a submission to the community consultation process. However, in a commendable effort to raise awareness and stimulate community debate, Prof. Collignon this week detailed his views in an accessible format as an opinion piece titled ‘Recycled Water Not Worth Risks’ in the Canberra Times.
Prof. Collignon’s concerns are numerous. He states that the proposal does not appear to make sense in environmental or economic terms. However, given his position and expertise, I assume that his primary concerns regard risks to public health. He wrote:
“A number of methods are [proposed] to make this recycled sewage "safe" but how many systems work perfectly all the time? If membrane technology is used, how can we be sure that these membranes will be able to accommodate the planned 24 million litres of recycled water that they need to filter each day? How will we know when there are small tears in parts of the membranes? Bacteria are very small and unless the pore size of these membranes is 0.2 microns it is unlikely that all bacteria will be removed.”
The first question, regarding system reliability, is –I acknowledge- the most difficult to answer. I concur that no engineered system should be assumed to work perfectly all the time. However, there are well established means for ensuring that we anticipate ‘unexpected’ malfunctions and design water management schemes such that malfunctions do not present elevated risks to public health. We do this by implementing a high degree of ‘redundancy’ in the system. This means that we have multiple barriers to contaminants that we are concerned about and that the barriers operate independently of each other. Even if a number of the independent barriers malfunctioned completely, the water would still be fully protective of human health. If an indirect potable recycling scheme does not provide this degree of surety, it simply has not been designed according to world’s best practice and should never be built in this country.
The question regarding the ability of water treatment membranes to accommodate 24 million litres of water each day is similarly a question of treatment plant design. A Californian indirect potable reuse scheme reliably treated more than 100 million litres per day by reverse osmosis and is currently being upgraded to a capacity of 266 million litres per day. A real advantage of membrane treatment systems is that they are modular and can be expanded relatively easily to accommodate any necessary capacity. Spare capacity can be built into a system relatively easily.
The ability to detect “small tears in parts of the membranes” is extremely important. Numerous approaches are used at different plants. The integrity of membrane treatment processes is monitored and checked by a number of direct and indirect measurements. In most advanced water recycling schemes, water quality is monitored by ‘Supervisory Control and Data Acquisition’ (SCADA) systems with sensors placed at strategic locations within the treatment process and at the final point of dispatch from the plant. The most useful online parameters are typically conductivity, turbidity and total organic carbon (TOC). These may be used to indicate the quality of water leaving the plant as well as for closer monitoring of individual treatment modules or ‘sections’ of plants to identify maintenance requirements. Significant ruptures of reverse osmosis membranes (which are exceedingly rare) can be observed by sudden drops of pressure across the membrane. These can also be continuously monitored by pressure sensors.
Prof. Collignon notes that bacteria are very small and that they would not be effectively removed unless the pore size of these membranes is 0.2 microns. He will be relieved to know that most commercially available microfiltration membranes do a fine job or removing organisms of this size. Ultrafiltration membranes typically have pore sizes between 0.1 – 0.01 microns. Nanofiltration membranes have pore sizes 0.01 – 0.001 microns. Reverse osmosis membranes remove contaminants of 0.001 – 0.0001 microns which is numerous orders of magnitude smaller than any known bacteria or other living organism. Removal of both bacteria and viruses is assured and membrane processes are only one or two of the multiple barriers that a full treatment system would incorporate.
Prof. Collignon wrote:
“However, if the pore size is so small, I find it difficult to see how these membranes can satisfactorily work without being frequently blocked by larger waste material. Even if such small pore sizes are used, this will still not remove viruses, which are much smaller. Membranes will also not remove drugs passed in urine and faeces that are not broken down (such as oestrogens)”.
Prevention of membranes being ‘blocked’ (or ‘fouled’, as we tend to say) is indeed a key challenge for the operation of advanced water treatment plants. However, it is achieved in Australia and overseas by careful pre-treatment. This typically involves placing a microfiltration or ultrafiltration process in front of the reverse osmosis process. Nonetheless, membranes do have a lifespan which is typically dictated by gradual fouling and thus need to be periodically replaced. This is part of the anticipated cost of operating a membrane treatment process.
I am a little bit shy about telling an eminent professor that he is wrong about the inability of membranes to remove species as small viruses, drugs or oestrogen hormones. But frankly, on this point he simply is uninformed. More than a decade of peer reviewed literature has demonstrated the ability of membranes to remove these contaminants. I suggest he check some of the references that I have previously listed here and here. Another peer-reviewed paper that demonstrates this is:
Drewes, J. E., Bellona, C., Oedekoven, M., Xu, P., Kim, T. U. and Amy, G. (2005) “Rejection of wastewater-derived micropollutants in high-pressure membrane applications leading to indirect potable reuse”. Environmental Progress, Vol 24, No. 4, 400-409.
Prof Collignon wrote:
“Ultraviolet light will also be used as an additional sterilising agent. However, this is far from an ideal disinfectant. There are many issues such as time of exposure, susceptibly of different microbes, and so on, for it to work. How can we be sure that this can handle 24 million litres of waste-water per day?”
Indeed, UV disinfection must be operated at sufficient doses, but assuming that the system is designed appropriately, there is no reason to assume that it wont be operated appropriately. Given pre-treatment by membrane filtration, UV disinfection is extremely effective, -more so than chlorine for many microbes. We can be sure that it can handle 24 million litres of water per day by designing the system for such a capacity. Much larger capacity plants are successfully operated in many places such as California and Singapore.
A point with which I strongly concur with Prof Collignon is the following:
“Safety monitoring is planned, presumably by culturing the water and looking at coliform counts. If coliforms (eg E. coli) are present in the treated water this implies faecal contamination (and thus a failure of the system). However, this type of monitoring has problems. Around the world numerous outbreaks with water contaminated with viruses and Cryptosporidiosis have occurred despite low or zero coliform counts. In addition these indicator bacteria take one or two days to grow and identify.”
I absolutely agree that coliform monitoring is not sufficient for ensuring the absence of pathogens such as viruses and Cryptosporidium. Numerous studies have demonstrated a very poor correlation between the presence of coliforms and these pathogens. Accordingly, coliform monitoring alone is not an acceptable means of monitoring pathogens in indirect potable water recycling schemes. Furthermore, no method of monitoring any pathogens just at the end of the treatment process is really sufficient. Instead, modern methods of quantitative microbial risk assessment (QMRA) are essential to ensure that a scheme is designed for reliable removal of pathogens as advocated by the Word Health Organization. One of my more senior colleagues, Prof. Nicholas Ashbolt, has been instrumental in introducing such approaches in Australia. This is a topic worthy of much more detailed discussion than is appropriate for this post, but one that I do want to devote some serious discussion to in a subsequent posting.
Prof. Collignon’s comments regarding the sensibleness of recycling water that already has a value as environmental flows are, in my opinion, perfectly reasonable. His preference for retaining water for Canberra that would otherwise be used by downstream communities and irrigators is also worthy of national debate.
I would suggest that Prof. Collignon’s comments are among the most valuable contributions that we have had to the ongoing debate about potable water recycling in Australia during the last couple of years. His expertise and experience are far too valuable to ignore. I was pleased to hear the ACT chief health officer Paul Dugdale acknowledge Collignon’s concerns. His response was appropriate:
“There are always risks in any complex system but they can be managed...That's where my role really comes in, is making sure that the management systems and the design is such so that if those risks of failure of one part of a system actually happens, that you pick it up and it doesn't cause health problems.”
The debate is exceedingly healthy and will ensure that all schemes and proposals are rigorously scrutinised in Australia. I’m sure many regular readers (and maybe some new ones) will want to discuss some of Prof. Collignon’s comments in further detail. I, too, am keen to do so, so please let me know what you reckon.
Saturday, March 31, 2007
Thursday, March 22, 2007
NSW Election
Four years have slipped by since we last trudged off to the NSW polls to wrangle over the question of a lesser evil. Its always painful, but I can’t actually recall a NSW State election in which we didn’t know the outcome well in advance.
I’m not sure when a Liberal, National or Coalition Government last won a State or Territory election in Australia. However, I’m fairly confident that it has not happened this century (its nice to be able to make such wild and sweeping statements in the first decade!).
The 2003 NSW election was a landslide victory to Labor with 55 of the 93 lower house seats. The Liberal/National Coalition won 32 seats with the remaining six going to independents.
The NSW Labor Government have faced a number of crisis moments and much lingering dissatisfaction during the last 12 months. The Cross City Tunnel debacle was arguably Iemma’s first crisis, closely followed by the outcry against the unpopular seawater desalination plant that his Government is so determined to build, -rain or no rain.
Against this background, Debnam must have felt that he was at least in the race. However, his first problem was getting noticed. For months, he seemed to be jumping up and down on the sideline screaming ‘look at me! look at me!’. When nobody did, he took the matter into his own hands to make some press for himself any way he could.
Soon after the Cronulla riot, Debnam found a TV camera to glare into and promise that on “Day 1” of his Government he would arrange for the NSW Police to round up “200 Middle Eastern thugs” and “charge them with anything”. It certainly worked in terms of attracting media attention. However, I suspect that Debnam overestimated the degree of reactionary xenophobia in NSW and probably lost more votes than he gained.
Once the election campaign began in earnest, Debnam played what was clearly his strongest card in the first hand. He read the opinion polls and saw that a strong water recycling policy would trump Labor’s contentious desalination plant. He played it reasonably safely, but promised that under extreme conditions, he would “flick the switch” to divert a miniscule amount of highly purified recycled water into Prospect Reservoir. As planned, the very suggestion of potable water recycling generated headlines in all the major papers.
The opinion polls responded in earnest. Consider this article from the Sydney Morning Herald last month:
Recycled water still the way to a voter's heart
Anne Davies State Political Reporter
February 28, 2007
THE Coalition's plan to recycle sewage and other waste water to boost Sydney's drinking water supplies is still more popular than Labor's desalination plant, according to a Herald/ACNielsen poll.
The poll, taken last weekend, found that 64 per cent supported desalination, while 75 per cent supported recycling.
Respondents to the NSW-wide poll were specifically told that recycled water would include recycled sewage.
The questioners asked: "Thinking about increasing NSW water supplies, one option is to treat sewage and other waste water. This recycled water would be safe for drinking and other household purposes. Do you support or oppose the introduction of recycled water to supplement the NSW water supply?"
Yet despite Labor's contention that voters will not accept having to drink recycled water, about 48 per cent said they preferred recycling over desalination. Another 40 per cent said they preferred desalination over recycling.
"Both major options for supplementing our water supply are popular with voters, but when asked for a preference, recycling is picked by more voters than desalination," said the research director of ACNielsen, John Stirton.
Support for recycling was higher among Coalition and Green voters (81 per cent in both groups) and lower among Labor voters (70 per cent).
More men than women supported recycling, and it was more popular among older voters. Support for desalination was higher among Labor voters (75 per cent) than Coalition voters (55 per cent) or Green voters (49 per cent). Younger voters were more supportive of desalination.
The results will give the Coalition some comfort that its water plan was not behind its decline in the Herald's broader poll revealed yesterday. The Coalition trails Labor 43 to 57 on a two-party preferred basis.
But Labor strategists are adamant the electorate is vulnerable to a scare campaign on recycling, and once they understand that they will be drinking recycled effluent under the Coalition plan, they will not support it.
All politicians need stunts for election campaigns. Of course Debnam had the wholly unoriginal idea of a taste test. Just like Labor had done with desalinated seawater a year or so earlier, Debnam visited shopping centres and busy thoroughfares challenging people to guess which cup contained recycled water. When it was revealed that Debnam had sourced his recycled water from the North Richmond Water Filtration Plant, a few people cried foul. Debnam was kind enough to respond by saying “Dr Stuart Khan from UNSW says its recycled water so therefore it is”. If only more people would see the world that way.
While the ACNielsen poll revealed Debnam’s water policy to be more popular than Labor’s, it is clearly not sufficient to win an election for him. Every single other policy announcement since February has been a dud. I suspect that Debnam recognised that he played his best card too early and tried to play it again this week. However, the media has clearly lost interest and moved on. Debnam’s preference for skimpy swimming attire and his apparent early concession speech have been the main media focus throughout March.
The only seat for which water policy can reasonably be assumed to be a sustained election issue is the new seat of Goulburn. Star Liberal Party recruit Pru Goward would have to be considered a serious contender and the seat is currently notionally Liberal with a margin of around 4.5 per cent.
Goward has been criticised in the media this week for her apparently contradictory position that potable water recycling is viable in Sydney, but not in her own electorate. I know that politics is politics and you simply say what you gotta.
Let’s just let Saturday happen.
I’m not sure when a Liberal, National or Coalition Government last won a State or Territory election in Australia. However, I’m fairly confident that it has not happened this century (its nice to be able to make such wild and sweeping statements in the first decade!).
The 2003 NSW election was a landslide victory to Labor with 55 of the 93 lower house seats. The Liberal/National Coalition won 32 seats with the remaining six going to independents.
The NSW Labor Government have faced a number of crisis moments and much lingering dissatisfaction during the last 12 months. The Cross City Tunnel debacle was arguably Iemma’s first crisis, closely followed by the outcry against the unpopular seawater desalination plant that his Government is so determined to build, -rain or no rain.
Against this background, Debnam must have felt that he was at least in the race. However, his first problem was getting noticed. For months, he seemed to be jumping up and down on the sideline screaming ‘look at me! look at me!’. When nobody did, he took the matter into his own hands to make some press for himself any way he could.
Soon after the Cronulla riot, Debnam found a TV camera to glare into and promise that on “Day 1” of his Government he would arrange for the NSW Police to round up “200 Middle Eastern thugs” and “charge them with anything”. It certainly worked in terms of attracting media attention. However, I suspect that Debnam overestimated the degree of reactionary xenophobia in NSW and probably lost more votes than he gained.
Once the election campaign began in earnest, Debnam played what was clearly his strongest card in the first hand. He read the opinion polls and saw that a strong water recycling policy would trump Labor’s contentious desalination plant. He played it reasonably safely, but promised that under extreme conditions, he would “flick the switch” to divert a miniscule amount of highly purified recycled water into Prospect Reservoir. As planned, the very suggestion of potable water recycling generated headlines in all the major papers.
The opinion polls responded in earnest. Consider this article from the Sydney Morning Herald last month:
Recycled water still the way to a voter's heart
Anne Davies State Political Reporter
February 28, 2007
THE Coalition's plan to recycle sewage and other waste water to boost Sydney's drinking water supplies is still more popular than Labor's desalination plant, according to a Herald/ACNielsen poll.
The poll, taken last weekend, found that 64 per cent supported desalination, while 75 per cent supported recycling.
Respondents to the NSW-wide poll were specifically told that recycled water would include recycled sewage.
The questioners asked: "Thinking about increasing NSW water supplies, one option is to treat sewage and other waste water. This recycled water would be safe for drinking and other household purposes. Do you support or oppose the introduction of recycled water to supplement the NSW water supply?"
Yet despite Labor's contention that voters will not accept having to drink recycled water, about 48 per cent said they preferred recycling over desalination. Another 40 per cent said they preferred desalination over recycling.
"Both major options for supplementing our water supply are popular with voters, but when asked for a preference, recycling is picked by more voters than desalination," said the research director of ACNielsen, John Stirton.
Support for recycling was higher among Coalition and Green voters (81 per cent in both groups) and lower among Labor voters (70 per cent).
More men than women supported recycling, and it was more popular among older voters. Support for desalination was higher among Labor voters (75 per cent) than Coalition voters (55 per cent) or Green voters (49 per cent). Younger voters were more supportive of desalination.
The results will give the Coalition some comfort that its water plan was not behind its decline in the Herald's broader poll revealed yesterday. The Coalition trails Labor 43 to 57 on a two-party preferred basis.
But Labor strategists are adamant the electorate is vulnerable to a scare campaign on recycling, and once they understand that they will be drinking recycled effluent under the Coalition plan, they will not support it.
All politicians need stunts for election campaigns. Of course Debnam had the wholly unoriginal idea of a taste test. Just like Labor had done with desalinated seawater a year or so earlier, Debnam visited shopping centres and busy thoroughfares challenging people to guess which cup contained recycled water. When it was revealed that Debnam had sourced his recycled water from the North Richmond Water Filtration Plant, a few people cried foul. Debnam was kind enough to respond by saying “Dr Stuart Khan from UNSW says its recycled water so therefore it is”. If only more people would see the world that way.
While the ACNielsen poll revealed Debnam’s water policy to be more popular than Labor’s, it is clearly not sufficient to win an election for him. Every single other policy announcement since February has been a dud. I suspect that Debnam recognised that he played his best card too early and tried to play it again this week. However, the media has clearly lost interest and moved on. Debnam’s preference for skimpy swimming attire and his apparent early concession speech have been the main media focus throughout March.
The only seat for which water policy can reasonably be assumed to be a sustained election issue is the new seat of Goulburn. Star Liberal Party recruit Pru Goward would have to be considered a serious contender and the seat is currently notionally Liberal with a margin of around 4.5 per cent.
Goward has been criticised in the media this week for her apparently contradictory position that potable water recycling is viable in Sydney, but not in her own electorate. I know that politics is politics and you simply say what you gotta.
Let’s just let Saturday happen.
Sunday, March 18, 2007
TBYATD – Brisbane version
‘Think Before you Agree to Drink – Is Sewage a Source of Drinking Water’ is a booklet produced by Snow Manners and John Dowson of Toowoomba. I have previously written a fairly extensive review of TBYATD, which is available from here.
Ten days ago, it was announced on the anonymous Toowoomba-based Water Futures blog site that ‘there is a strong rumour that the "Think before you agree to drink" book has re-invented itself for distribution to Brisbane households. The rewrite is expected to shake the Government and the Water Industry to the core and fully engage the Brisbane community in the debate’.
The word ‘rewrite’ had me expecting that there might be some substantial new information. -Perhaps an analysis of the economics of competing water delivery options; -Possibly a critique of the role of the private sector; -Potentially a discussion of societal impacts of potable water recycling. I was looking forward to reading it and providing a further detailed review.
The Brisbane version of TBYATD was released on the Water Futures blog site this weekend and I can only say that it is most disappointing. Not only is there no new information to ‘shake the Government and the Water Industry to the core’, even basic factual errors have not been corrected.
For example, if Manners and Dowson are going to quote the book 'Our Stolen Future' they should at least cite the correct authors (Theo Colborn, Dianne Dumanoski, and John Peterson Myers). Sheldon Krimsky wrote a completely unrelated book called 'Hormonal Chaos'. Manners and Dowson may not have actually read either of these books, but since I have previously pointed out this error of fact, it is a mystery why it has not been corrected in the ‘rewrite’.
Similarly, the significant confusion between the impacts of conventionally treated discharged effluent in the environment and advanced treated recycled water continues to permeate TBYATD from front cover to back. I can only conclude that the misunderstanding and confusion that this is likely to impart to readers is not considered by the authors to be a failing that is worthy of revision.
From what I can tell, the only thing new in the Brisbane version of TBYATD is a ballot paper on page 20. This invites people to answer ‘yes’ or ‘no’ to the question ‘do you want water sourced from sewage treatment plants and then treated, to be returned to the drinking water supply of South-East Queensland?’.
The Water Futures blog site states that ‘at a cost of hundreds of thousands of dollars this is probably the largest privately organised public vote in Australian history’. I suspect that any Big Brother eviction night would be considerably larger, but more importantly, the opportunities for multiple voting seem to be similarly encouraged as they are on BB. Names and contact details are ‘optional’ and responses can be posted, faxed and/or emailed to Manners and Dowson. In the 21st Century, it is unclear why some of the vastly more secure and verifiable means of voting, which are available on the internet, were not adopted. I think this is unfortunate since it misses a fine opportunity for more accurately gauging community sentiment.
I thought the Toowoomba-edition of TBYATD was a worthy effort to stimulate discussion about some important issues relating to water recycling and to environmental chemicals. However, given the feedback that I have now provided, I think it is quite disappointing that the ‘rewrite’ would apparently make no effort whatsoever for improvement. Surely another lost opportunity.
I encourage you to read my earlier review.
____________________________
Update: The Courier Mail is also running a blog on the same topic, which you might like to check out.
Ten days ago, it was announced on the anonymous Toowoomba-based Water Futures blog site that ‘there is a strong rumour that the "Think before you agree to drink" book has re-invented itself for distribution to Brisbane households. The rewrite is expected to shake the Government and the Water Industry to the core and fully engage the Brisbane community in the debate’.
The word ‘rewrite’ had me expecting that there might be some substantial new information. -Perhaps an analysis of the economics of competing water delivery options; -Possibly a critique of the role of the private sector; -Potentially a discussion of societal impacts of potable water recycling. I was looking forward to reading it and providing a further detailed review.
The Brisbane version of TBYATD was released on the Water Futures blog site this weekend and I can only say that it is most disappointing. Not only is there no new information to ‘shake the Government and the Water Industry to the core’, even basic factual errors have not been corrected.
For example, if Manners and Dowson are going to quote the book 'Our Stolen Future' they should at least cite the correct authors (Theo Colborn, Dianne Dumanoski, and John Peterson Myers). Sheldon Krimsky wrote a completely unrelated book called 'Hormonal Chaos'. Manners and Dowson may not have actually read either of these books, but since I have previously pointed out this error of fact, it is a mystery why it has not been corrected in the ‘rewrite’.
Similarly, the significant confusion between the impacts of conventionally treated discharged effluent in the environment and advanced treated recycled water continues to permeate TBYATD from front cover to back. I can only conclude that the misunderstanding and confusion that this is likely to impart to readers is not considered by the authors to be a failing that is worthy of revision.
From what I can tell, the only thing new in the Brisbane version of TBYATD is a ballot paper on page 20. This invites people to answer ‘yes’ or ‘no’ to the question ‘do you want water sourced from sewage treatment plants and then treated, to be returned to the drinking water supply of South-East Queensland?’.
The Water Futures blog site states that ‘at a cost of hundreds of thousands of dollars this is probably the largest privately organised public vote in Australian history’. I suspect that any Big Brother eviction night would be considerably larger, but more importantly, the opportunities for multiple voting seem to be similarly encouraged as they are on BB. Names and contact details are ‘optional’ and responses can be posted, faxed and/or emailed to Manners and Dowson. In the 21st Century, it is unclear why some of the vastly more secure and verifiable means of voting, which are available on the internet, were not adopted. I think this is unfortunate since it misses a fine opportunity for more accurately gauging community sentiment.
I thought the Toowoomba-edition of TBYATD was a worthy effort to stimulate discussion about some important issues relating to water recycling and to environmental chemicals. However, given the feedback that I have now provided, I think it is quite disappointing that the ‘rewrite’ would apparently make no effort whatsoever for improvement. Surely another lost opportunity.
I encourage you to read my earlier review.
____________________________
Update: The Courier Mail is also running a blog on the same topic, which you might like to check out.
Monday, March 12, 2007
Virginia Pipeline Project
Of all Australian capital cities, Adelaide is the stand-alone champion when it comes to the overall proportion of municipal effluent that is treated and reused for a beneficial purpose. The current largest and most important water reuse scheme in Adelaide is known as the Virginia Pipeline Project.
During the 1990s, there was growing concern about the environmental effects of the large volumes of secondary-treated sewage effluent discharged into the sensitive Gulf St Vincent. The considerable quantities of the nutrients nitrogen and phosphorous were leading to the destruction of seagrasses and mangrove forests, as well as annual blooms of toxic algal species. The initial response was a plan to upgrade the sewage treatment process by the construction of a biological nutrient removal (BNR) plant.
However, at the same time it was recognised that horticultural farmers on the Northern Adelaide Plains were withdrawing unsustainable volumes of groundwater from local aquifers for irrigation. The cone of depression thus caused was resulting in salt water being drawn in from the Gulf St Vincent and the aquifers were becoming saline. The reduced availability and quality of groundwater was expected to cause reduced future horticultural production and, subsequently, reduced employment in an area which was already economically depressed.
It was realised that with suitable treatment, the effluent from a sewage treatment plant (STP) could be used as an alternative irrigation resource on the Northern Adelaide Plains.
Adelaide has four metropolitan STPs. The largest of these is Bolivar STP, just to the north of the city. Bolivar STP was converted from a trickling filter plant to an activated sludge plant, and then further upgraded by the addition of a Dissolved Air Flotation Filtration (DAFF) process. DAFF involves injecting the effluent with billions of very fine air bubbles that carry small particles and suspended matter to the surface for skimming off. Further multi-media filtering and chlorination then take place in preparation for reuse of the water.
A large proportion of reclaimed water from Bolivar is transported via an 18 kilometre pipeline to Virginia, which is an important agricultural area on the Northern Adelaide Plains. Currently, this is around 15,000 megalitres per year, which is about 15% of the total of Adelaide’s wastewater from its four STPs.
The reclaimed water is then distributed via 120 kilometres of pipeline network to horticultural irrigators. It serves more than 240 irrigators who produce root and salad crops, brassicas (cauliflower, broccoli, cabbage, etc), wine grapes and olives. No special labelling or marketing restrictions are required for the produce. No health problems have been reported and export of Adelaide Plains produce such as wine does not appear to have suffered in any way.
The water is metered as it is delivered to dams on individual grower's properties. The growers then pump out the water through their own irrigation systems. The dams are required to hold three days supply in case maintenance is required for the supply system.
For the development of the scheme, the South Australian Government negotiated a public-private partnership in the form of a build, own, operate and transfer (BOOT) arrangement. The funds for the $22 million pipeline network came partially from the successful private tenderer Euratech (subsequently acquired by EarthTech), SA Water, and the Commonwealth Government. EarthTech will transfer ownership of the pipeline network to SA Water in 2018.
The Virginia Pipeline has been operational since 2000 and in October 2005, the South Australian Government and the Commonwealth Government agreed to co-fund an extension of the scheme via the National Water Commission. The extension project involves an additional 18 km of pipelines to be laid, extending into neighbouring Angle Vale. This will allow up to a further 3000 megalitres of treated water to be supplied to the region every year.
However, a major limitation to the quantities of water that can be beneficially reused is the highly seasonal nature of the demand for irrigation water. On average, the Bolivar DAFF plant produces about 110 megalitres a day of effluent. During summer, most of this is used by growers at Virginia. However, in winter, when most growers do not need the water, the effluent is discharged to the sea.
If the effluent that is not required during winter could be efficiently stored, the scheme could be significantly expanded to other areas. A research program- funded by a consortium of government and private bodies including SA Water, CSIRO and United Water – is now underway to examine the possibility of storing water in an underground aquifer for seasonal use.
This research has involved the winter injection of recycled water diverted from the Virginia Pipeline scheme into a brackish limestone aquifer for subsequent reuse during the summer irrigation season. I hope to have a closer look at this aspect of the project when some results become available.
Adelaide may bask in the glory of being home to Australia’s largest water reuse scheme...at least until the end of 2008!
During the 1990s, there was growing concern about the environmental effects of the large volumes of secondary-treated sewage effluent discharged into the sensitive Gulf St Vincent. The considerable quantities of the nutrients nitrogen and phosphorous were leading to the destruction of seagrasses and mangrove forests, as well as annual blooms of toxic algal species. The initial response was a plan to upgrade the sewage treatment process by the construction of a biological nutrient removal (BNR) plant.
However, at the same time it was recognised that horticultural farmers on the Northern Adelaide Plains were withdrawing unsustainable volumes of groundwater from local aquifers for irrigation. The cone of depression thus caused was resulting in salt water being drawn in from the Gulf St Vincent and the aquifers were becoming saline. The reduced availability and quality of groundwater was expected to cause reduced future horticultural production and, subsequently, reduced employment in an area which was already economically depressed.
It was realised that with suitable treatment, the effluent from a sewage treatment plant (STP) could be used as an alternative irrigation resource on the Northern Adelaide Plains.
Adelaide has four metropolitan STPs. The largest of these is Bolivar STP, just to the north of the city. Bolivar STP was converted from a trickling filter plant to an activated sludge plant, and then further upgraded by the addition of a Dissolved Air Flotation Filtration (DAFF) process. DAFF involves injecting the effluent with billions of very fine air bubbles that carry small particles and suspended matter to the surface for skimming off. Further multi-media filtering and chlorination then take place in preparation for reuse of the water.
A large proportion of reclaimed water from Bolivar is transported via an 18 kilometre pipeline to Virginia, which is an important agricultural area on the Northern Adelaide Plains. Currently, this is around 15,000 megalitres per year, which is about 15% of the total of Adelaide’s wastewater from its four STPs.
The reclaimed water is then distributed via 120 kilometres of pipeline network to horticultural irrigators. It serves more than 240 irrigators who produce root and salad crops, brassicas (cauliflower, broccoli, cabbage, etc), wine grapes and olives. No special labelling or marketing restrictions are required for the produce. No health problems have been reported and export of Adelaide Plains produce such as wine does not appear to have suffered in any way.
The water is metered as it is delivered to dams on individual grower's properties. The growers then pump out the water through their own irrigation systems. The dams are required to hold three days supply in case maintenance is required for the supply system.
For the development of the scheme, the South Australian Government negotiated a public-private partnership in the form of a build, own, operate and transfer (BOOT) arrangement. The funds for the $22 million pipeline network came partially from the successful private tenderer Euratech (subsequently acquired by EarthTech), SA Water, and the Commonwealth Government. EarthTech will transfer ownership of the pipeline network to SA Water in 2018.
The Virginia Pipeline has been operational since 2000 and in October 2005, the South Australian Government and the Commonwealth Government agreed to co-fund an extension of the scheme via the National Water Commission. The extension project involves an additional 18 km of pipelines to be laid, extending into neighbouring Angle Vale. This will allow up to a further 3000 megalitres of treated water to be supplied to the region every year.
However, a major limitation to the quantities of water that can be beneficially reused is the highly seasonal nature of the demand for irrigation water. On average, the Bolivar DAFF plant produces about 110 megalitres a day of effluent. During summer, most of this is used by growers at Virginia. However, in winter, when most growers do not need the water, the effluent is discharged to the sea.
If the effluent that is not required during winter could be efficiently stored, the scheme could be significantly expanded to other areas. A research program- funded by a consortium of government and private bodies including SA Water, CSIRO and United Water – is now underway to examine the possibility of storing water in an underground aquifer for seasonal use.
This research has involved the winter injection of recycled water diverted from the Virginia Pipeline scheme into a brackish limestone aquifer for subsequent reuse during the summer irrigation season. I hope to have a closer look at this aspect of the project when some results become available.
Adelaide may bask in the glory of being home to Australia’s largest water reuse scheme...at least until the end of 2008!
Sunday, March 04, 2007
Sewer Mining
As we have discussed, one of the major difficulties with water recycling is often the need to transport water from treatment plants to where it is needed. One approach that largely avoids this problem has become known as ‘sewer mining’.
Sewer mining involves taking water directly from a sewer -practically anywhere- and treating it onsite in preparation for an intended use. The water is not treated by a conventional sewage treatment plant, but typically by a compact, sometimes portable treatment station. Often, the solids and other waste streams may be simply dropped straight back into the sewer.
A number of private companies have trialled sewer mines in Australian cities. One such trial was undertaken by a company called Earth Tech and involved the portable sewer mine shown below in Melbourne’s Albert Park. This system uses a biological membrane reactor, which is a treatment process analogous to secondary sewage treatment, but on a much smaller and more compact scale. The biological treatment is followed by reverse osmosis membrane filtration. The plant was designed as a self-contained unit which can be loaded onto the back of a truck and easily relocated.
In Sydney, Kogarah Council ran a 6-month trial of a sewer mining pilot plant at the Beverly Park Golf Course, with the somewhat less compact pilot-plant shown below. In this system, the water first passes through gross and fine solids separators. A submerged aerated filter then provides the biological treatment process. A dual media filtration process follows, providing additional removal of some dissolved organic chemicals. Finally, disinfection is undertaken by both UV radiation and chlorine dosing.
The product water produced at the Kogarah pilot plant was thoroughly tested, leading to the NSW Government giving approval to use of recycled water from this system for irrigation.
At the time of the trial, Sydney Water did not have a specific procedure and approval process in place for this type of sewer mining project. Kogarah's pilot plant helped Sydney Water to develop a standard sewer mining agreement as well as a brochure describing how to establish a sewer mining operation in Sydney.
Kogarah Council now have plans to install a larger-scale plant using the same technology. The water from this plant will be used directly for irrigation of the golf course and nearby Jubilee Oval, as well as piped or transported to various Council parks. This is water that would otherwise have been discharged to the ocean at Malabar
This new water source will eliminate the potable water consumption that Kogarah Council uses to irrigate these areas and allow the Beverly Park Golf Course to comply with more stringent water restrictions. The plant will have a capacity to produce up to 750 kilolitres of irrigation water per day and it is forecast that the project will reduce potable water use in Kogarah by over 160 megalitres every year.
This $3.2 million project will be partially funded by the NSW Government via its Water Savings Fund for Sydney. A new sewer mining agreement for the full-scale plant is currently being negotiated for approval by Sydney Water.
The concept of sewer mining has many benefits for large cities with complex sewer systems. Catching and reusing water as it flows down-gradient towards coastal sewage treatment plants offers us the opportunity to significantly reduce the volume of water that reaches the ocean outfall plants. This will reduce the volumes of water that we need to pump back to inland elevated areas for reuse. Distributing water to dispersed customers is also facilitated by the opportunity to produce the water at locations close to where it is needed.
The approach also has the potential to relieve pressure on existing sewers in growth areas of the city. But most importantly, reusing this water for applications that would otherwise rely on drinking water can deliver considerable potable water savings, to the benefit of the entire community
In my opinion, every local government should have one…or two…or three. What do you reckon?
Sewer mining involves taking water directly from a sewer -practically anywhere- and treating it onsite in preparation for an intended use. The water is not treated by a conventional sewage treatment plant, but typically by a compact, sometimes portable treatment station. Often, the solids and other waste streams may be simply dropped straight back into the sewer.
A number of private companies have trialled sewer mines in Australian cities. One such trial was undertaken by a company called Earth Tech and involved the portable sewer mine shown below in Melbourne’s Albert Park. This system uses a biological membrane reactor, which is a treatment process analogous to secondary sewage treatment, but on a much smaller and more compact scale. The biological treatment is followed by reverse osmosis membrane filtration. The plant was designed as a self-contained unit which can be loaded onto the back of a truck and easily relocated.
In Sydney, Kogarah Council ran a 6-month trial of a sewer mining pilot plant at the Beverly Park Golf Course, with the somewhat less compact pilot-plant shown below. In this system, the water first passes through gross and fine solids separators. A submerged aerated filter then provides the biological treatment process. A dual media filtration process follows, providing additional removal of some dissolved organic chemicals. Finally, disinfection is undertaken by both UV radiation and chlorine dosing.
The product water produced at the Kogarah pilot plant was thoroughly tested, leading to the NSW Government giving approval to use of recycled water from this system for irrigation.
At the time of the trial, Sydney Water did not have a specific procedure and approval process in place for this type of sewer mining project. Kogarah's pilot plant helped Sydney Water to develop a standard sewer mining agreement as well as a brochure describing how to establish a sewer mining operation in Sydney.
Kogarah Council now have plans to install a larger-scale plant using the same technology. The water from this plant will be used directly for irrigation of the golf course and nearby Jubilee Oval, as well as piped or transported to various Council parks. This is water that would otherwise have been discharged to the ocean at Malabar
This new water source will eliminate the potable water consumption that Kogarah Council uses to irrigate these areas and allow the Beverly Park Golf Course to comply with more stringent water restrictions. The plant will have a capacity to produce up to 750 kilolitres of irrigation water per day and it is forecast that the project will reduce potable water use in Kogarah by over 160 megalitres every year.
This $3.2 million project will be partially funded by the NSW Government via its Water Savings Fund for Sydney. A new sewer mining agreement for the full-scale plant is currently being negotiated for approval by Sydney Water.
The concept of sewer mining has many benefits for large cities with complex sewer systems. Catching and reusing water as it flows down-gradient towards coastal sewage treatment plants offers us the opportunity to significantly reduce the volume of water that reaches the ocean outfall plants. This will reduce the volumes of water that we need to pump back to inland elevated areas for reuse. Distributing water to dispersed customers is also facilitated by the opportunity to produce the water at locations close to where it is needed.
The approach also has the potential to relieve pressure on existing sewers in growth areas of the city. But most importantly, reusing this water for applications that would otherwise rely on drinking water can deliver considerable potable water savings, to the benefit of the entire community
In my opinion, every local government should have one…or two…or three. What do you reckon?
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