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?


Anonymous said...

Stuart, have you gone off drinking sewage?

Anonymous said...

hey stuart. havent posted here in months how have ya been?? I think it would be a good idea for watering of local parks, golf courses etc. these are the ideas that councils should of been looking at too free up drinking water. things like this would save huge amounts of drinking water and also help reduce pollution to our enviroment.

Anonymous said...

Dear Stuart,
I have enjoyed reading your blog, and it is very interesting. I am doing a senior year, high school project about water recycling. I need information about "indirect potable re-use", that is about the current recycled water that already enters the Wivenhoe dam from Esk and Lowood.

I have heard that Brisbane is already drinking recycled water. I have been unable to find much information on it. I would like to know all about the quality of this "indirect potable re-use" and about the treatment plants it comes from. I would also like the process it takes to get into the Wivenhoe.

If you know some information about this, and some answers feel free to email me! Or if you know of any reports or websites which have thsi information, that would be great too!

Thanks Blucat

Stuart Khan said...

G’day Mick,

It has been months indeed and I’m very pleased to hear from you! Of course, I completely agree with your comments regarding sewer mining to save potable water while reducing pollution. In theory it can be done practically anywhere. However in smaller cities it is often more practical to take the water after it has been through the conventional sewage treatment plant, then it is simpler to upgrade (if needed), and transport it back to where it is to be reused. I’m not familiar enough with Toowoomba to know whether there are obvious uses that are far enough away from the sewage treatment plant to make it worthwhile pulling raw sewage straight out of the sewer. I’d be interested to know what you think…

Stuart Khan said...

Hello Blucat,

I’m very glad to read that you have found this blog worthwhile reading. I appreciate the feedback. I do indeed have some of the information that you are after. I have a fairly nice Excel spreadsheet that shows in some detail where various effluents are discharged and ‘who drinks from who’ in South East Queensland. I’ll send it to you by email.

I don’t have detailed information regarding the treatment quality of each individual sewage treatment plant. However, due to EPA regulations introduced in the 1990’s, almost all (if not all) inland STPs in SEQ discharge water of tertiary treatment quality. This does not refer to specific quality criteria in terms of maximum concentrations of specific chemicals and pathogens, but refers more to the treatment processes to which the water has been subjected. Unfortunately, its difficult to generalise much more than that. If you would like to email me back, I’ll be happy to send you some fairly generic information about tertiary treatment water quality.

Stuart Khan said...

Hello Anonymous (way back up the top),

I’m not sure what you mean by “gone off drinking sewage”. Do you mean “am I out drinking sewage with the boys tonight” or “am I over the whole idea of drinking sewage”?

Stuart Khan said...

Here's an article sourced from the Inner West Courier today...

Recycled water to feed Concord golf courses
Scott Warren, Tue 6 March 2007.

Parks and golf courses around Concord are set to be freed from the clutches of the drought.

A $1.7 million initiative to recycle sewer water for irrigation purposes will benefit Concord Oval and six other parks, as well as Massey Park and Barnwell Park golf courses.

It's just the second facility of its type to be built in Sydney, following the successful introduction of a recycling plant at Kogarah.

The funding was announced by NSW Utilities Minister David Campbell last Tuesday. The State Government is contributing $1.2 million of the funds, with Canada Bay Council providing the other $500,000.

Petrina Harcourt, who compiled Canada Bay Council's application for the funding, said the arrangement had been 18 months in the making.

"We looked at many different water-saving opportunities," she said. "By tapping into the sewer, there is a constant supply of water, so there's no need for a large storage capacity, which is one of the issues with stormwater harvesting."

Another benefit is the speed of the process.

"Within one or two hours of the water being pumped in, it can be treated and pumped out for irrigation," Ms Harcourt said.

Where water sourced from Sydney Water costs $1.26 per kilolitre (1000 litres), water processed by the recycling plant will cost the council just 30 cents per kilolitre, with a maximum yearly output of 170 million litres.

"There's so much potential with the plan," Canada Bay Council's technical services director Mark Bunch said.

"We could sell the water on to a third party, if there is any left over. I know many schools would be interested in using the water.

"We have more open space than any other council in Sydney, so this water will be a great boost for our recreational facilities."

Canada Bay mayor Angelo Tsirekas was excited by the environmental benefits of the plan.

"The plan will enable council to maintain its top-class sporting fields, but not at the expense of the environment," he said. "The initiative will be rolled out over a number of years to make sure infrastructure, such as pipes and water tanks are installed effectively and the resources are put to the best possible use."

Massey Park Golf Club secretary manager Tony Rosillo said his course was in the best condition ever, but would improve even more when the recycled water was made available.

"We have had a lot of problems with social players and members not being happy with the condition of the course," he said.

"We have no fairway watering systems, so our greens and tees are fine, but the fairways are a bit dry. It's a massive boost for us."

Anonymous said...

In a city the size of toowoomba it may be better too collect the water after treatment. especally if the sewage treatment plant isnt all that far away. the treatment plant is actually pretty close to toowoomba. although having said that toowoomba does have alot of parks. so maybe collecting it before hand might be the better way?? I think it would all come down too the cost of both and what is the more viable method etc

Stuart Khan said...

Thanks Mick,

I was glancing through the Toowoomba Water Supply Task Force interim report last night. They did, in fact, consider sewer mining and came to much the same conclusion as you. The major limitation seemed to be that there are actually not all that many non-household customers for the potable water supply in Toowoomba and that the volume they use is relatively small. I think most of the parks rely on local groundwater rather than compete for the potable water supply, -is that right? The Task Force Interim Report says:

Across Toowoomba there are 54 non-residential (industrial/commercial) users who take water from the reticulated supply. The total consumption of these users for the 2005/06 year was 1,560 megalitres, which represents about 10 to 12 percent of total potable consumption.

Of the non-residential users, 14 have been identified as being able to use recycled water in lieu of potable water, with a total use estimated to be about 250 megalitres per annum. This represents about one to two percent of total potable consumption. These users are spread across the city, and are some distance from the Wetalla Water Reclamation Plant.

Anonymous said...

Thankyou, once again for all the resources, you have sent me.

Anonymous said...

I'm not 100% sure on that stuart but i have heard that some of toowoombas parks do get watered by underground supplies. though its good now when i drive past laurel bank park in the morning on the way too work i dont see lots of water going down the drain unlike 3 yrs ago

Unknown said...

Hello Stuart,

Do you have quality & quantity data about sewer mining operation? I am very interested on the data of how much the sewage is abstracted from sewer network as well as the quality & quantity of the remaining solids which is dicharged back to sewer network. I do really thank you if you could give me any info regarding those data, because i tried to search in any literature but i could not find it. Thanks a lot.

the eco architect said...

Hi this is Barbara
Im in my final year in Architecture and as part of the course work we have to conduct research within the field. My interests lie in toilet and waste, and my progress have led me down the path of sewer mining.
I am struggling to find a gap in the research and therefore struggling to form some sort of argument.??
Could you please possibly give me some direction?

Stuart Khan said...

HI Barbara,

Of course it depends entirely on where your interests are focused, but I would think some obvious research questions might include:

- How reliable is the flow capacity of the sewer?
- How well are specific contaminants of concern removed?
- How can the energy efficiency be improved?
- How can the solid wastes be best managed?

...just a few ideas! Good luck with your research!

the eco architect said...
This comment has been removed by the author.
the eco architect said...

Hi stuart, thanks heaps for your great help.
I have focused my research on an analysis of 3-4 best practice commercial buildings. I have chosen 3 melbourne examples. can you think of any best in practice commercial buildings that are exemplars in sewer mining. i will compare the analysis of each to help formulate a frame work using the questions you have provided as a useful guide.

Anonymous said...


mines qld said...

Water shortage is everywhere,so this is a good thing that Queensland Australia uses water recycling in mining process. And in my view every mining place should use the water recycling so that water can't be waste and got proper utilization.

coal mines queensland said...

That's really good that there is reusing and saving of water.As today there is big need of water.Queensland Australia take a good step here.

Post a Comment