Wednesday, April 02, 2008

Solid waste or resource?

This week some of my workmates and I paid a quick visit to Toowoomba in South East Queensland. The primary purpose of our visit had very little to do with recycled water (we do occasionally work on other things, you know!).

We were visiting for a project which involves investigating the fate of contaminants in waste products from beef cattle feedlots. We’re working with the meat and livestock industry to help them better understand how different management practices affect the degradation of chemical contaminants and the inactivation of pathogens.

If you’ve ever visited a large feedlot (something that all carnivores should do at some time), then you may have an idea of the scale of the challenges associated with managing the waste products from 20,000 head of cattle. If not, then maybe the photos below might give some indication..

On Monday we visited three different feedlots and the management practices employed by them were noticeably quite different. However, a common theme was the need to remove manure from the feedlot pens and store it in a way that allowed it to be sufficiently stabilised for it to then be utilised as valuable by-product of the feedlotting process.

One of the three feedlots managed the manure by mounding it within the pens. Another focused on stockpiling it outside the pens for up to 12 months and then sieving it into two grades for various types of land application. The third feedlot went one step further by employing carefully managed composting processes in order to convert what was previously a waste product into a significantly more valuable fertiliser. All three feedlots typically sell their processed manure to local farmers for the production of crops such as sorghum.

Since we were going to be too late to fly back to Sydney on Monday night, we decided to stay over in Toowoomba. This gave us the opportunity to pay a quick visit to the Wetalla Water Reclamation Facility on Tuesday morning. I was particularly interested to visit this plant to find out more about the 43-year contract that had recently been achieved to sell 3000 ML/year recycled water (treated effluent) to New Acland Coal Mine by March 2009. This agreement involves selling the effluent from the plant to the coal mine, which is then responsible for pumping the water about 40 kilometres to wash coal at the mine. The price that the coal mine have agreed to pay is $1.30 per kilolitre, which is roughly equivalent to the average consumer price for drinking water here in Sydney. This gives some indication of the value of water security for a thirsty industry in a dry region.

Of course, not everybody is happy. The effluent from the Wetalla plant is currently discharged to Gowrie Creek and subsequently used by irrigators downstream. The irrigators had previously rejected the opportunity to secure this water for $0.15 per kilolitre in 2000. However, they are now unsurprisingly unhappy about losing this free resource. I think there are lots of interesting (and potentially quite heated) discussions to be had on this topic, -covering such issues as water rights and property, environmental justice, public good, etc. But I’m not going to get into any of them now..

One feature of the Wetalla plant that I was completely unaware of is the new (not quite completed) solar sludge drying facility. Sludge is a byproduct of sewage treatment, which contains a significant amount of solid material, primarily as a result of biological growth during secondary treatment.

Depending on how the sludge is treated and further processed, it can still contain around 90% water. Its composition and sheer volume produced can render sludge disposal one of the major challenges (and costs!) associated with wastewater treatment. Sydney Water, for example, transports most of its sludge on tanker trucks to western NSW towns such as Parkes for land application. The sludge from Wetalla is also trucked to local destinations for disposal and this is a significant cost to the plant (and thus to Toowoomba City Council and the local community).

As a means of reducing the trucking costs, Toowoomba City Council have commissioned the development of an innovative solar-powered sludge drying facility. This is observable as the long rectangular shed in the bottom right-hand corner of the below aerial photograph.

After mechanical dewatering, the sludge is dispersed along the floor of the facility, where it is turned and aerated to facilitate drying. After some period of time (which is variable, depending on the weather), a completely dry hard product is produced with a small fraction of the wet sludge mass. While we learnt about the process from the folks at Wetalla, they seemed quite impressed with the significant reductions in disposal costs which they would achieve; and fair enough -they are significant. However, personally, I couldn’t help thinking about the cattle feedlots that we had visited the previous day and the success that they had had with converting a waste product into a valuable resource. I wanted to bring some of the dried sludge pellets home to try them out as plant fertiliser. If I find some spare time this year (yeah, right!), I’d be interested to do some analyses for contaminants such as pesticides and heavy metals. Something tells me that the City of Toowoomba has a valuable product to sell, which should be making –not just saving- money to dispose of.

Sometimes it can be difficult to distinguish a valuable recourse from a troublesome waste product. Factors such as drought, population growth, climate change, fossil fuel availability and nutrient exhaustion may cause us to seriously reassess our perspective sometime very soon.


People's Republic of Ramara said...

Very interesting. Here in Canada similar attempts have been tried.

Communities are starting to divert organic household wastes to companies for composting.

These companies have would like to try using this process (with some significant modifications) to compost both human and farm wastes.

Given this is something new, there is plenty of government regulation that is stiffling innovation.

What usually happens in Canada, finally these innovators and will get feed up, and are lured offshore (ie to Germany by $$$ grants and government support), they develop these technologies, and we end up buying it back at 10 times the initial investment.

When will we ever learn! When will we ever learn!

Stuart Khan said...

Thanks for the comment PRR,

Yes, it’s a familiar problem and we can certainly relate to it in Australia. I can think of a number of water treatment technologies that were originally developed in Australia and that we are now purchasing back the commercialised versions from overseas. And its not just the technologies themselves, -we are also buying in the plant construction and operation skills from overseas!

I’m not certain, but I think the solar sludge drying technology above is either Italian or German.

Anonymous said...

So Stuart, you just happen to drop into Wetalla sewerage farm and TCC Chief Engineer Kevie Flanagan just happens to be there to show you around (as seen in the last photo), and you expect us to believe that you haven't been on the TCC payrole the whole time!!

You're wasting your time in science, you really should be in public relations or business development. Next you'll be telling us that sewerage sludge is a great safe product that we should all sprinkle on our lawns and gardens.

Stuart Khan said...

Thanks for the feedback Anonymous,

I had thought that these types of comments had dried up, but I see that there remains a significant level of residual bitterness in Toowoomba.

Just so you know: I have never received a cent of payment from TCC for anything. That's not to suggest that I have some philosophical objection, since I would certainly be interested in future opportunities for research funding. A significant part of my job involves chasing research funds.

I knew that I would be in Toowoomba for the feedlot project and took the opportunity to contact Kevin Flanagan (who I knew from the REUSE07 conference) to ask whether it would be possible to visit the plant while I was in town. That’s not unusual, -I have visited many sewage treatment plants in Australia and all over the world. Kevin and Wetalla staff were kind enough to spend two hours showing our group the plant. Afterwards we enjoyed a cup of instant coffee and were on our way.

Anonymous said...

Stuart, you try but for some, they will always be ignorant of the facts.

one who knows said...

It not the facts - it's just that noone trusts Kevin!!!

Anonymous said...

Damn, what did he do, to make you not trust him?

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