Interviewer: G’day, and welcome to CSIROPod. I’m Glen Paul. An algal bloom is a term used to describe a rapid increase in the population of algae in an aquatic system, to a point where it can seriously reduce the water quality. Blooms can discolour water, form surface scums, produce unpleasant tastes and odours, and create problems for aquatic life.
High nutrient concentrations, particularly phosphorus and nitrogen, can allow a species of blue green algae to grow quickly in water where there is little turbulence and the weather pattern remains stable for a long period.
In an effort to combat these blooms, CSIRO is researching whether common mining in mineral by-products could be used to remove nutrients from ground water, reducing the potential for algal blooms.
In a joint project with the Western Australian Department of Water, CSIRO is investigating whether these mining industry by-products, which are currently unused, could instead be used to filter nutrients from natural waters, or to treat waste water that would otherwise be discarded.
Dr Grant Douglas from CSIRO’s Water for a Healthy Country Flagship is leading the project, and joins me on the phone. Now Grant, where did the idea come from for taking mining by-products and using them to control algal blooms?
Dr Douglas: Well, a few years ago we looked at Western Australia (WA) and decided well, WA is a large mining State, and we’re producing many millions of tonnes of by-products. Now, few of these by-products had ever really been looked at very closely, and certainly not with a view to possible reuses in environmental amendments, so the project came out of that.
What we really began with was an effort to just firstly classify and characterise those materials, and from that we identified a range of materials that we believed had properties that might actually make them useful in an environmental setting.
Interviewer: OK, so what are these materials, and just how do they absorb the nutrients?
Dr Douglas: OK, well there’s a range of materials that are produced from the mining and mineral processing industries in WA, or not only WA for that matter, but nationally and internationally, and that’s another context of this project that some of these materials could be used overseas.
The materials that we’ve looked at are made up of a range of elements, but the most, I guess, interesting materials are ones of those that are rich in iron oxides, aluminium oxides, calcium and magnesium. Now, with an abundance of those elements, that confers a number of favourable properties that includes the absorption of nutrients, potentially absorption of some trace elements, and in certain by-products an ability to attenuate or neutralise acidity.
So there’s really a wide range of by-products that can be applied to a range of environmental challenges.
Interviewer: I see. So, how do you then introduce the by-products to the waterways? Is it just a matter of getting a dump truck and pouring them in, or is there a specialised technique?
Dr Douglas: Oh no, look we take a very conservative and ordered approach to this. We identify materials, as I said, that are fit for purpose, and then we look at the best ways to actually implement these in the environment.
Now one of those materials that we’ve looked at, NUA, we’ve actually used as a soil amendment.
So we introduced about five per cent of that by weight into the top 15 centimetres of the soil, and what we were able to demonstrate – and this is at a turf farm by the way, which is a really heavily fertilized environment – that over about four years we were able to remove about 97 per cent of the phosphorus, and about 82 per cent of the nitrogen. But on top of that a lot of other benefits, potential then to reduce fertilizer use, increase in regrowth rates. And also when the turf was transferred off site, what we actually saw was an increase in vigour of turn grown on these amended soils, relative to the controlled soils. So that’s one context that we’ve introduced it into the environment.
A second one is that we might actually put together either what’s known as constructed wetlands, or filter treatments where we want to treat waters that are for instance rich in nutrients. So we’d flow these waters through wetlands, or through filter systems. And previously where, for instance, these wetlands had no real abilities to remove nutrients, now we’ve augmented them with these materials, and so they’re highly absorptive.
So, for the first time it actually gives us a large volume, low cost material, with the right characteristics to remove a range of nutrients, and also potentially trace elements from waters and waste waters.
Interviewer: Right. So what happens then to these by-products once they’ve absorbed the excessive nutrients? They can’t then potentially become environmental hazards themselves?
Dr Douglas: No. We’ve undertaken extensive characterisation of these by-products. That involves things like looking at the major and trace element geochemistry, we also looked at the mineralogy, we also looked at the radioactivity, we also looked at the leachability of elements from it, both prior to and after use. And so what we were very careful about was not trying to perhaps use a by-product to solve one problem, but to create another.
So what we end up with, what we like to think is effectively a benign product at the end then can be for instance taken to landfill, or otherwise disposed of once it’s done its job.
Interviewer: Righteo. So this then potentially opens up a new market for the mining industry, but do you think it’s viable? Do you think it will be worth their while going into this market? Or do you feel another player would have to come onboard?
Dr Douglas: Well, it will be on a company by company basis as to whether these materials may be released for use. And also on the other side of that, that there will have to be regulatory approval in certain instances to determine whether that product will be used, and under what circumstances.
But at the end of the day mining companies are looking to reduce their environmental footprint, and this is certainly one of the ways they can do it. Where they previously would have had to stockpile materials, this is a way of perhaps reducing that stockpile, and doing something useful for the environment at the same time.
Interviewer: Right. Well it certainly does sound like it has the potential to do that. But how far reaching, or successful, do you think this could be into the future?
Dr Douglas: Well, at this stage we’ve only just conducted trials in Western Australia, but the technology and the understanding that we’ve gained over the last few years of this project is by no means restricted to WA. There are certainly similar materials produced nationally and internationally.
And in fact we’ve just begun a collaborative project with China. China also has a fairly large and active mining and mineral processing industry, and so we’re also looking to characterise materials produced by them. And these will be particularly useful in the Chinese context where there’s a lack of infrastructure, perhaps a lack of sewerage and so forth in rural areas, and perhaps we can use these high volume, low cost materials in productive environmental applications in rural China.
Interviewer: OK. Well, look that’s really encouraging, and it’s great to hear that we are taking the technology international. So thank you very much for talking to me, Grant. It sounds like a really useful initiative, and I wish you the best of luck with it.
Dr Douglas: Thank you very much. A pleasure.
Interviewer: Dr Grant Douglas from CSIRO’s Water for a Health Country Flagship. For more information go to www.csiro.au.