 Well, welcome everyone to Hydrotera's latest webinar. Today, we've got one of our favorite presenters, Phil Mulvey. Back again, thanks, Phil. And Phil is going to be talking to us about understanding landfill leachate, further developments of the elder end ratio after almost 30 years of use. Before we get into that, I would like to begin by acknowledging that we conduct our work across this great land. And for that privilege, we would like to thank the traditional owners. Hydrotera respectfully acknowledges the Boon Wurrung people of the Kulin Nation, where we are located today. And we pay our respects to their elders, past, present and emerging. So Phil's Founder and Director of Innovation at Environmental and Earth Sciences, or EASY as it's known these days. And Phil's a true expert in landfills. A little bit about Phil. So he's been investigating, managing, designing, closing, building on and auditing landfills since 1981. He designed the first bioreactor landfill in Australia for Wagga Wagga Council in 1992. He has published numerous papers on different aspects of landfill management since 1986. In 1996, at the Third National Waste Conference, together with Stuart Brisbane, he presented a paper introducing the L-to-N ratio, now known as the Mulvey Ratio. In 1997, he revised the ratio at the ISWA Conference. What does ISWA stand for, Phil? International Solar Waste Association. Thank you, in Wellington, New Zealand, to the version now used. Since then, the L-to-N ratio has been adopted widely as a management tool for landfill leachate. Phil has qualifications in soil science and hydrogeology and is an auditor in New South Wales, South Australia and Victoria. All right, before we let Phil charge into things, we love your questions. And in order for you to raise them, please use the Q&A button at the top of your screen. Why does Hydrotera do these webinars? Well, we actually enjoy them. It's a good way to keep in touch with people like Phil. We get to share knowledge, facilitate some education and provide a forum for industry leaders. About that. Before we do that, just a little note about our groundwater sampling course that we've got on at the moment. It's really gathering momentum. We're doing this in conjunction with ALGA. So if you're into landfills, you're probably into groundwater sampling. So we do have this industry accredited groundwater sampling training underway. So feel free to get in touch about that. All right, so without further ado, I'd like to pass over to Phil. Thanks for that fantastic introduction, Richard. And I really want to acknowledge your team for the great work they do in putting these seminars on and ensuring that the industry has a chance to hear from a whole variety of different people in regard to measurement and landscape. So thanks and well done to your team. And thanks for the invite for me. Next slide, Richard. Probably we're just in talking about landfill leachate. We do have to have a bit of a discussion about landfill types. The landfill chemistry, both in our gas and leachate is derived. Why are the elder end ratio was set up? What is the new tools for assisting in the elder end ratio and the enclosure of the session? You've heard my experience. I don't need to talk about that greatly. But just to note the first paper I did in 1986 was with Roger Parker, who many of you will know quite well. And we did one of the first papers of probably the first paper on understanding a bit about landfill leachate in Australia with reference to the Burswood Casino, which is building a landfill. The original stage one, Casino. Next slide, please. Landfill types and impact on waste chemistry. So it's important to understand a little bit about what happens with potraceable matters, it breaks down. And then to understand a little bit about landfill types. So this session will just concentrate a little bit on understanding the different phases of the landfill. So the first stage is the aerobic stage where oxygen is still present and dominates. And there could be a slight drop in pH associated with that. The next stage is the fermentation stage. This is the beer brewing stage where you get a lot of CO2 produced, but no methane, and you get the consumption of nitrate. The next stage is anaerobic, living off sulfate and girthite. So rust within the landfill. That's why landfills are deeply into the methogenic stage, actually have a lot of black covering of iron, which is actually pyrite precipitated where the rust used to be. So they're the basic stages of a landfill. In some degrees, they're also basic stages of organic plume contamination moving through groundwater. Need to understand that organic matter is made up of a certain ratio of carbon, nitrogen, phosphate, sulfate, and potassium. And the cells actually need that. The microbes need that to break down. So there will be plenty of excess carbon. So they'll release that. There's plenty of nitrogen. They'll release that. They keep phosphate cycling round because they need that. So you don't often see elevated phosphate associated with landfill leachate. The sulfur they need, the water gets precipitated as pyrite. So the phosphate and sulfur are held within the landfill, typically. And the potassium and nitrogen species are released mostly, well, particularly in the case of nitrogen, to groundwater and potassium entirely to groundwater. So the really weird thing about it is that potassium because, well, next slide, please, Richard. I suppose I better stop talking and just move along a bit in the slides and talk about the water. So the thing I understand about protressable landfills, and in New South Wales, protressable are defined as municipal waste, whereas elsewhere in Australia, protressable is any organic waste. Is hydrocarbon, is that really not much comes out of them except they're very nutrient rich. So hydrocarbons get broken down within the landfill, particularly aerobic stage, and then into the anaerobic stage. pHs and tars are also broken down. Heavy metals are immobilized by the sulfur in versions of pyrite or sorbed under six-way oxides, which is your rusts, which cover your iron during the aerobic stage. Your PCBs and your pesticides tend to greatly stick pretty much to the organic matter and the clay within landfills. Chlorinateds are a problem, though they degrade in anaerobic or faculty of anaerobic conditions. The types of conditions in landfills can result, and this is why it's highlighted, in vinyl chloride. So that's one of the exceptions to what comes out. And as we'll see later, there will be a discussion on what mirth does PFAS do. So landfill leachate looks pretty nasty, really, but it's, in terms of hazardous compounds, the greatest hazard is nutrification of oxygen. So you can see a lot of bubbling going on there. This is a landfill leachate collection pond. What you've got is lots of blue-green algae and lots of bubbling effects of CO2 and methane coming from it. Next slide, please. So the factors that are affecting landfill types and thereby their leachate is the age of the landfill, the input into the landfill, and the cover. And they're very important to consider because they have different aspects on how the L-to-N ratio may behave. Next slide, please. So if you look at an age of landfill, I've been around long enough to see these phases, so it is important to understand what happened. So pre-1979, the landfills were burnt. And I grew up at Mudgee, a small town in western New South Wales, and I used to love going to the landfill as an eight- to nine-year-old, collect all the old-prime wells to make billy carts out of, and the fires were always going at the landfill. So it was unsightly and located out of town because it was burnt. It didn't have ibis then, but it certainly had rats. So it meant that the pre-1979 landfills have a lot of burnt material, not much potressibles. So lots of metals and pHs are in them. So you get a different style of lead shape. In 1979 to the mid-1990s, landfills were known as sanitary landfills. They used clay liners. They had a lot of potressibles in them. They weren't burnt. They were often galley landfills and would come back to some of the problems associated with those. In the post-mid-1990s, there was a movement to entombment of waste with gas extraction. Still had lots of potressibles, but the circumstance is that they're now contained within HDPE liners, both top and bottom. Lots of redevelopments occurred on the sanitary landfills predating the 1990s and the burnt landfills. Whether we'll have development over the interned landfills is an interesting question. So increasingly around the world now there's an movement away from entombment to controls a leachate interaction with the environment, which we won't get time to discuss today, but part of the problem with interned landfills is not a set and forget as people thought when they were designed originally. Next slide, please. So what's the input material? So defining a number of different landfill types. So a municipal landfill that takes municipal waste, that street-collective rubbish waste, you have a huge amount of potressibles in it, you have plastics, you can have all kinds of things. You can have a lot of PFAS waste streams, not just fire extinguishers, but Teflon, all the food boxes from pizzas, the microwavable popcorn, the disposed carpets with scotch guard on them, et cetera, et cetera. Solid waste with potressible which means you've got tree waste, cardboard, timber coming in together with dirt so they have significant amounts of potressible. Then you've got soil only which has small amounts of potressible but not a lot. And then you have special monocells that might have ash, might have different types of specialised waste. We had a monocell on a landfill area that just had laminated water in MDF and so yes not all monocells don't produce potressibles so you've got to look at what the monocell does contain. Next slide please. It's also important to understand the nature about cover a little bit. The covers if it's permeable, you get gas of water diffusion in and out and if you've got a good grass cover the methane is actually bi-degraded to CO2 except where macropyroste is and then you have impermeable covers to which you pull the gas off. The nature of the cover does to some extent affect the leachate and the water and the level of the water does also affect the leachate as well. Quite a few landfills just before moving on I just want to touch on another issue, sorry Richard please. Part of cover design and landfill construction is often leachate is reticulated the TDS does go up but intriguingly the TDS seems to bottom out somewhere between five and eight thousand. It doesn't go any higher and we think that that's to do with some of the geochemistry and microbial reactions involved. Next slide Richard. Leachate plume chemistry so this is we looked at the slide before Richard said do I want duplication well actual fact I do because it's important to understand that this material will be very reactive and though it comes in different phases it will react with the environment as it moves through it and it is a major problem because it causes eutrophication of our streams though macrophytes love it so you often find on some of the quite older landfills lots of grass growth that is stripping out the nutrients and that's why phyto caps are now much more designed for landfill closure however it doesn't address the PFAS problem. Next slide please. So you can see here is an old paleo channel what you see is that green little oxbow it's a former oxbow lake of probably some 30,000 to 2 million years ago and it comes in under that center fence so it's dipping away underneath the landfill is built over it and you can see the methane has migrated vertically up from that lens and killed the trees so the only thing that's killed it is the absence of oxygen methane is not for trees directly toxic it's the absence of oxygen that's killed it but you can see where the lead shade is expressed to the surface as this lens slopes 90 degrees away and expresses the surface but you've got large amounts of grass to the fence and then in the farmers paddock beyond of a drought you've actually got a green pick there for the animals so the grass can tolerate much more aggressive methane rising because the oxygen's penetrating down the 30 or 40 centimeters and the microbes are converting that methane to CO2 at the level at which oxygen's coming down. Trees having deeper roots and a greater demand aren't able to actually knock get the oxygen penetrate more than 30 to 40 centimeters and so can't knock the impact of that methane so you can see that the lead shade itself is nutrient rich for the plants which as long as they don't get hit by methane they quite like it next slide please so this is from Roger our paper together with the client back in 1986 and it was one of the first look at what happens with landfills so what happens is the dotted line on the left represents a landfill greater than 10 meters deep and of significant age beyond more 10 years so you're already a fair way up the concentration in lead shade of any particular substance you're coming through. The key thing to note is it has what's called lead distribution which means it rises reasonably rapidly to a maximum that has a long tail off. Most of the primary settlement occurs at that point of hitting the maxima associated with the degradation of the organic matter of the landfill and if you're looking at it simply as methane or CO2 or even as lead shade itself typically it hits that maximum between 5 to 20 years if the landfill is less than 10 meters deep if it's more than 10 meters deep you need to push it out more considerably next slide please so let's get into the nuts bolts of what we're talking about here's the phases of a landfill you go through so you have the aerobic phase where you have aerobacteria breaking down what's available they need oxygen to do it they consume the oxygen you move to the next stage which is the start of fermentation so phase 2 is the first part of anaerobic phase which is a fermentative phase which doesn't produce methane it produces CO2 you get some and a little bit of anaerobic bacteria producing hydrogen during this then you move to the transitional phase to the full methogenic phase you hit peak CO2 but you start to have methane coming in and then finally you go into the maximum methane phase which takes a period of time you're moving more into secondary settlement not primary settlement and then you come out the back end where you start to get oxygen penetration again so that's a long time frame that anaerobic phase that phase 4 is in the realms of 30 to 40 years depending on thickness it can be longer and it does vary on cells so cells can go through their own phases of different speeds to other cells or pockets can be faster or slower depending on the amount of clay and soil co-deposited so you can get quite a degree of leachate variation within the landfill itself next slide please so this is sort of how I mean this is for a spill but it's a good slide to show that the redox zones associated within an organic phase moving out but in this case it's the organic reactor itself but you still have those same phases so you've got oxygen dominated zone and a nitrate dominated zone so manganese and iron go into solution sulfate gets taken out of solution for genesis next slide please so just revisiting that again what you've got is you've got different reactions occurring with the meeting through which it travels and the very first part the front of the front is where the native cations are displaced and they go up talk a bit more about native cations later but also at the nitrate attenuation stage you start to see ammonium coming but you start to see bicarbonate come up which is the reaction of the microbes producing CO2 and at pHs 5 to 8 CO2 will express as bicarbonate and then you move into why you end up with manganese in solution and why you get iron in solution and finally sulfate dropping out of solution next slide please you want to just clarify to people why we're moving through these phases so certainly the reason why we move through these phases is this is why the L2N ratio is used and it reflects some of the chemistry because the TDS and pH and EC for some extent become poor indicators as they change to different things so understanding the site conceptual model of the phases of the leachate including how it reacts with the environment so we'll talk a little bit later about absorption and elite and what elite does in terms of the L2N ratio so it's important to understand that a landfill leachate reactor or a landfill reactor is producing leachate that is like a time-dependent plume from a hydrocarbon spill but all the reactions occurring at the one spot and moving out as a plume ahead with a series of phases that you can actually monitor and each of those phases have different issues that might be associated with the environment and do you get different bacterial populations emerging as you move into this sort of oxygen-depleted environment? Most definitely when you're in the aerobic you have the aerobic heterotrophs you'll also have within the landfill itself you'll have your alkane degraders and your naphthalene or pH degraders and their aerobic bacteria so they will work in that sector then you've got your denitrifying bacteria and it changes again to what you've got for instance you move from the oxidative phase the reducing phase on iron you'll have thiobacillus present so not thiobacillus you'll have desulfo-vibrio present and desulfo-vibrio does a reverse reaction it takes sulfate and breaks it down and liberates energy to other bacteria the heterotrophs to able to feed the desulfo-vibrio in the circumstance of you're releasing CO2 and CO2 will be released to the metagenesis which will use the CO2 to strip it and take energy off and produce methane so you've got a series of microbial processes that you go through where you're dealing with complex organisms living together so by the time you get to metagenesis you're actually at what we call swamp gas so you're producing the natural swamp degradation process or the process that makes which you'd be familiar with the black shales so the marine muds have a higher salinity but they also have the same things they have within them desulfo-vibrio and the same interactions with the anaerobic heterotrophs and the metagenic bacteria to create this community that moves energy around for the benefit of all Alright, thanks for the clarification So let's just go back to the biological breakdown of plant materials so Richard was a slide to soon really but so you've got the microbes that want to break down to get energy but also to get the nutrients they need so salinity goes up in some instances it does depend on your background salinity so down here in Melbourne for instance if you have a landfill that's on the Silerian so the Cumevale silt stones or the mud stones you have an issue where the local groundwater is actually quite a bit more salty than what the landfill is producing and same with on estuary sediments or up in Sydney on the one amount of shales or Narambine shales you end up with the circumstance where the surrounding water is actually saltier than the landfill and in those instances it's very hard to pick out whether a front is passing or not and that's why having ratios explains all that biological breakdown of all plant material not just what's in the landfill produces this as does your produce and being colour in leachate it'll be brown to brown green there'll be gas discharges it'll be elevated BOD biological oxygen demand because of the tannins and the fennels that are released by the plants and the terpenes so it's not just landfills that does this it's mulch leachate in the soil it's night soil which used to be used around the edges of old landfills and night soil is the dunnecan collector which phased out in the late 1960s in Melbourne and Sydney but any manure will also produce it and that's why manures go to Adderabbiton digesters from large dairies as well as municipal waste so you need to be aware that what other sources might be around that could cause this the key thing to understand is that Elevide, potassium and nitrogen species are rare in groundwater particularly together as both microbes and plants do what they can to sort them up quickly and there's some exceptions the paleo waters in inland Australia will be rich in nitrate not ammonium because the acacias and the cacherinas during the wetter period of 200,000 years ago actually laid down nitrate so most of our inland waters are nitrate rich but potassium poor so you can still the elder in ratio pick that up next slide please just before we do so under you know things like dairy effluent like in New Zealand you get those big nitrate called nitrogen plumes so if you wanted to get the bacterial side of things up and humming to deal with that you'd be adding more potassium to get that ratio right would you well yes you can pick it because in those systems particularly canary plains the aloe and potassium so you can actually see it you want to get it humming again sometimes you'd not put a bioreactor before the river and use the bioreactor to nitrify what comes through actually you do a denitrifying nitrify process because you've got to convert it to money first and so their problem is a nitrate discharge as is Europe right across Europe they have a major nitrate plume problems so you've got to create set up a bioreactor area and you actually run that nitrate plume through a bit of peat with some appetite or crush rock phosphate so you're not releasing phosphate to the water but you're making phosphate available to the microbes so a combination of peat and phosphate would be a bioreactor to destroy that nitrate or reduce it to nitrogen gas but it's got to go to monium first so there is a process by which you have to do that and it's hard to do it scale because you need a longitudinal bioreactor running all the way beside the river one of these was installed in the Coburn Sound area associated with the fertilizer problems in West Australia alright maybe we're going to slide my fault so exchange under clays clays are charged particles and I won't go into all the aspects of clay chemistry but they have a net negative charge across them sesquioxides are a little bit different to clays but they what's called a pH dependent charge and they also have a net negative charge on some of their surfaces so the charge is actually met from the water through the cations from the weathering of rock and those cations compete for the charge and the preference is decided by the charge density of the cation which is the valency divided by the hydronic iron radius so effectively aluminium is more preferred than calcium magnesium potassium and sodium down that order and ammonium will sit up ahead of calcium depending on a little bit on the colloid chemistry and ammonium is particularly preferable zeolites and in certain biochars and various other things but the thing to note is you do have to understand a little bit about your background geology so the the the Hume silt stones for instance and many of the metasediments going all the way up from Victoria into New South Wales of salarine sediments they have a lot of illite in them or they have an illite smectite which has a preferential for salving potassium but by Titi Granite in the highlands of Australia and northern Victoria and southern New South Wales releases potassium so it's one of the few instances where you'll get slightly elevated potassium in groundwater so understanding your geology is also important next slide please Rich a hydrated ionic radius so what exactly is that for I can't all those slides out Richard but alright what you're dealing with is for instance sodium doesn't have a particularly huge ionic radius but it attaches water so it's able to have a lot of water molecules surrounding it but calcium has less water molecules so sodium's capacity is to keep attaching water molecules to itself so it's got a charge of one and a very large water molecule based ionic radius so next to lithium it's the least preferred both lithium and sodium so many waters on each other they disperse clay magnesium has a small tendency to add a bit of water on to itself calcium not so ion and so calcium's got a two plus valency and so that controls the charge density I'm sorry I've actually got that ratio right so you're appropriate to raise it should be hydrated ionic radius divided by the valency so my apologies Richard so then it goes all the way up to your three charged ions in solution so your three valencies such as aluminium with a three plus charge is quite preferred but when it's ALOH4 it's only a single plus valency and when aluminium is in solution a very high pH but it has much larger hydrating radius so it tends not to be necessarily well preferred on the ion exchange positions so that sort of explains the basis of that I've done it actually time to go chemistry at all quite right we'll move on thanks so this is the original Dunmore D'Arthur came from the paper and unfortunately we actually used something that young people would not know about is overhead projectors back then so this was a shot from a a plastic overhead which you put on to a screen you project it onto the wall so the data is not a very good quality but the thing just to note is you potentially might have one or two breakthrough fronts occurring here but it's into a recent sand mine so it's back filled in a sand mine there's no line as it's sort of a 50 system that occurred and you can see a substantive breakthrough front starting to occur in about 1995 where your BOD goes up the fomentative phase your bicarbonate goes up so you're producing masses of CO2 your sulfate starts to drop in that top image so it displays all the classic bloom behaviour so I'm not actually making this up this is not a load of textbook bull yarn this is actually what happens notice the TDS is bouncing all over the place so it's not particularly a useful indicator here and the pH goes down in the acidic phase as you can see and then comes back up again but it also goes down other times and were they fronts coming through or were they just dilution events due to heavy rainfall or were they due to other factors but just before the front goes up you can see the sort of steady periods you can see the TDS for some reasons dropped and then up it goes and then you've got as the nitrate I'm tracking nitrate there no I'm not I'm just tracking ammonium so you can see that's why we thought oh this useful we had 20 that stage we had 4 or 5 years of monitoring that site we monitored in excess of 20 years so we continued to get pretty good data from that particular site next slide please so out of it came the opportunity to do some bloom behaviour modelling so the first paper talked about ammonium potassium divided by calcium plus magnesium sodium so it was what was in leachate divided what is the common native cations potassium can be native but it's normally sapped up by trees pretty quick so you tend not to get it except in those circumstances we spoke about before the ratio didn't also pick up the aerobic phase that well so we added nitrate in the paper in 1997 why multiply by 100 and I've been asked that question quite a few times the human brain doesn't handle 0.001 through to 0.01 very well so if you multiply by 100 you now have a number that falls between 1 and 100 and the brain handles that much better than 0.001 to 0.01 so that was the reason for multiplying by 100 no other reason except to make it visually comprehensible to the reader next slide please just before you do so what are the units you're using there it's unitless so it's mili it doesn't matter if it's in this instance we use we're using milligrams because we're just lazy and don't want to convert but it wouldn't matter because what you're looking at is relative difference which we'll come to in a sec mostly it's universally adopted in the mass balance not the charge balance okay which is on mass so now go to the bottom line and just look at the L to N ratio which is there shown on the bottom right next to ammonium so you can see that the L to N ratio kicked off before ammonium did it's got it had a little downturn as did ammonium so was that due to our competition by the native cations being released as the ammonium got absorbed well I suspect so then it goes up as you can see the ammonium has a dip as it moves from the fermentation stage to the methygienic stage but the L to N ratio just continues to climb it doesn't reflect that in change in rate the pH goes up the TDS sort of bounces all over the place it's not telling you anything greatly in this environment but the L to N ratio is showing predicting that the front at very low concentrations of breakthrough and is consistent in predicting its behavior as you can see that BOD goes up much the same time then it comes down the sulfate starts to come down from that point of time you can actually see the sulfate recovering again after hitting zero so this is a fast plume breakthrough because it's in sand and poorly capped and poorly lined next slide please so let's talk about my poor spelling with Y-T-E-H but anyway let's talk about some recent developments on it and let's not talk about my poor entity this is a landfill that's been infilled from the bottom upwards borehole 15 which is right where Richard's cursor is we must have practiced this is an indication of where the last lot of filling is and there's two adjoining properties there ones three or four adjoining properties you can see there's a few fruit trees around those scattered trees are fruit trees there's a bit of gardening and there's some chooks which you won't be able to see and there's GB, background bores GB05 GB06 on the two different properties so let's go down to the next slide please now I'm going to have to get rid of Richard's image so I can see this properly Richard so the one property is borehole 5 it's got an older end ratio of 1 it shows low phosphate it shows low ammonium it's an aerated system and low nitrate it's got a little bit of bicarbonate in the water it's got a classic situation of having potassium lower than calcium magnesium surprising enough it's a sodium magnesium dominated so in terms of ideal growth we probably want a bit more calcium in the system but if you look across to it the fluoride's also low so that's a brief run of a quick understanding of the older end ratio how it looks at that and saying it's got a ratio of 1 well next door's gone up to 2 and you go okay there's a problem now let's have a look okay there's quite a bit of ammonium there's a slight increase in nitrate but the phosphates come up bicarbonates come up potassium appears to have come up but because we've got phosphate up and the overall TDS appears to have dropped a little bit based on what we've measured there simply because there's some out competition in bicarbonate we're actually doing the system where they've added fertilizers they're doing a lot to get the garden and lawn to grow they're not putting town supply watering because the fluoride's not up so that ratio doesn't reflect and they may even be using septic tank disposal so that doesn't reflect landfill traveling up gradient it's simply reflecting the site usage now if you go to borehole 15 this shows all the classic indicators it's actually either in the edge of the landfill right in it or on the very very edge of it so what you're seeing is a breakthrough front occurring you're going through the last stages of fermentation where you're producing nitrate your sulfate is still there but being consumed you've got a bit of phosphate bouncing around in the system there's no fluoride to indicate town water ammonium is high and going up sulfate's going down and sure enough the L2N ratio is going up reflecting the fact that we are producing we're still an active metagenesis phase and we're producing a lot it could be a front that's passing on the very edge of the landfill itself and just reading so you have to go back to logs to confirm that it's either reading a front or reading the decay of a cell because over that three-year period you start to see the L2N ratio drop the bicarbonate is still up which indicates the L2 is still quite rich the ammonium is starting to drop and the potassium may have peaked so nice lovely classic data set showing what's happening with the L2N ratio what the ratio means is irrelevant in terms of the number it's its behaviour that counts so does the L2N ratio apply to creek water let's have a look at this example next slide please Richard so here we have quite a bouncy L2N ratio it's it's certainly above one it's above two and it's getting to above five but if you run your eye across there's no ammonium potassium actual factors can be high when it's low comparatively but potassium is just really really low the overall TDS is low sulphate is unusually high so it's in an urban area because it's not in old water it's a young water I should have put fluoride up so we'd have another look of fluoride and TDS but you can see nitrate is periodically very high so the L2N ratio can be used in surface water scenarios but you've got to use it with great caution potassium doesn't normally express to rivers and ammonium is rapidly converted to nitrate in the river system anyway particularly in the aerated system and you'll find lots of plants, macrophytes your your junkers and your bull rushes and so on growing the banks in the area that the discharge occurs so in this instance the L2N ratio is telling you absolutely nothing and that's why you need to look if you're going to use surface water you've got to have a pretty good idea what the water is doing so what your the L2N ratios I'll show you later is a key to look further into the data next slide please so let's talk about some interpretation aids someone I said later I meant the very next slide so here we plot the L2N ratio on semi log paper with time and you're dealing definitely immediately we see a couple of significant things the ratio is variable across the monitoring wells this is monitoring wells associated with a landfill you've clearly got one there's out of leachate of some sort but you've got another one that's bounced along from may or may not be leachate to suddenly going very very high and the first conclusion would be it is leachate so let's go and have a look at it next slide so we're dealing with two bores here borehole 6 which is on the south west next to borehole 4 with a orange notation and you can see that the landfill is the whole area in the middle and borehole 6 is not supposed to be directly in the landfill it is beside a road in a dip in the road so just give you that little indication borehole 10 is also beside the road in the dip of the road and it's either in or potentially in landfill so we'd have to check the logs for that so just going with the data we have it in front of us at the moment and the groundwater appears to be up gradients in this direction moving through the landfill which is all that bit between 10 and 6 and discharging out so if you go to the next slide please so you run your eye let's run our eye along 10 first we can see the monium bounces a bit but it's high and could be falling sulphate comes in and disappears completely and maybe starting to come back bicarbonates is dropping off in the back half of the monitoring period 2018 and phosphate is close to 0 and fluoride is low let's look at 6 so ammonium we run our eye down to ammonium and it's down to 73 38 41 52 14 jumps to 626 475 182 so let's look at nitrate so nitrate is low but then jumps a bit and then jumps even more then drops back to low and then jumps again if you run your eye down to phosphate you'll see that phosphate was low and suddenly went ridiculously high and the fluoride bounces a lot so we asked the landfill a few questions they put a mulch out in the landfill and across the face of the landfill they fertilized the mulch and they sprayed it with town water so in actual facts then we looked closely at the well construction and wasn't one of our wells I have to add it was slotted to just below the surface half a meter from the surface and it was in a culvert and so the water that ran down the culvert runs into the well at certain conditions and so that doesn't actually represent landfill leachate it represents poor well construction and a series of site activities on the surface so it's quite intriguing just seeing what the data tells you you look at it in more detail and the sulfate expresses that that there's aerobic as does the nitrate there's aerobic water occasionally entering the system but there's also some highly reduced water going on as well so sometimes what the data the elder and ratio tells you is go and have a bit of a look before you automatically conclude it is actually landfill leachate it's certainly a bit tressable leachate signature not a doubt about that the loading of phosphate indicates that it's got fertilization as well and the intermittent high fluorides indicative of irrigation by town water all of which was confirmed with the client and the site inspection next slide please when you've got a trend like that and you're liaising with the operator of the site if it's trending down the elder and ratio do you sort of say well we're heading in the right direction do nothing or how do you a lot of these are audit data they're not necessarily I was the consultant giving the advice but it depends if you're directly monitoring leachate or if you're monitoring a plume so if you're monitoring leachate in a cell you can say the cell's aging and that's good it's what we're expecting to see that but you'll start to see a bit more settlement going on and so forth if you're monitoring a plume and the plume front passes and you can say well this is the plume from your oldest cell we may see other just because it's dropping doesn't mean we won't be seeing other plumes passing so it's good it's dropping how close are we to a sensitive receptor a waterway besides whether you do an intervention or not and whether you have within your management system an attenuation zone depends on that as well so the advice depends on the type of landfill obviously your license the type of landfill proximity to the sensitive receptor and let's just look at further interpretation aids for the elder in the show and this is not just plotting semi-long but this is going to help you in multiple interpretations so here's a series of different aged back filled sand mines now back filled with builders rubble which obviously includes potressable matter it's quite an old landfill it's over in WA it's in sands of course the site is as defined so we couldn't get an up gradient well very readily because we couldn't drill off site but we got some pretty and it's so long ago that was our original logo it was back when we had an office in WA but anyway it's very interesting data so next slide please nice logo too yeah I like the old logo times move on so what you've got is a series of whales drilled into different wastes sometimes not fully within the waste so when you're slotting across zones it's always a problem and in an environment like this with sand and back filled with sandy waste it's often hard to work out when you're drilling whether you drilled out or not so it's across the gilford formation so a sandy clay down into a clay to sandy clay zone so it's a fairly low flow area next slide please so we've split it up according to different classes and also done the L2N ratio so you've got background where the ratio is a little bit higher potentially we've got impacted backgrounds is resulting in a drop in the L2N ratio and then we've got a series of different landfills with different behavior in the L2N ratio now we want to split that out a bit further and try and get a better understanding of it so what we came up with next slide please in this case we didn't use it with nitrate which we should have but anyway so we plotted against the L2N ratio against PE plus pH and we've done this a number of times since I'll give you some number of examples so this allows you to split the behavior of the ratio according to the redox conditions so you've got a series of classes and you can see that they cluster and they fall out into quite separate domains I'll now preempt Richard's question and explain what PE is so PE is the negative log of electron activity so effectively it's CH measured by your or probe which I'm sure you can buy from Hydra Terra or rent from Hydra Terra if you don't have one already and you calibrate with quin hindrone and it operates off a platinum electrode so it produces a reading in millivolts that reading whether positive or negative divided by 59.2 is equivalent to the negative log of electron activity so you're adding the negative log of electron activity together with pH the negative log of hydrogen activity so that defines those two terms define the ion pairs and the nature of the redox state of the plume and that's why by plotting L2N to it you split aspects of the plume that might have same L2N ratios but different redox next slide please next slide so this is another example it's a site that is a from a gullyfill site you can see there is two leachate wells LBO2 and LBO3 close together you can see there's the berm across the gully and there's two wells and it's a very very steep gully and there's two wells sort of mid slope down the gully but somewhat between cross gradient and up gradient you can't, I can't see it on my screen you might be able to see it on yours but beneath LBO5 in that region there is horse yards so you've got a source of manure sitting upgrade of KMBO1 and KMBO5 it's on a potential Elyte smectite siltstone next slide please and this is quite interesting when you plot it out LBO3 which is the square boxes is much more clay it has an interface drainage issue so it gets water in it from up above when it's wet going down to lower when it's dry going down to a lower level of man and it's also in quite heavy clay with less buttressables LBO2 the cross is in quite buttressable environment and less clay which you'll get in landfills that sometimes there's a lot more soil that comes in particularly in country landfills and mixed matter and there is in municipal matter the municipal matter might only arrive two or three days a week for the garbage trucks and there might be a constant stream of soil and commercial rubbish the interesting thing is that during the dry years the ratio is lower during the wet years and the reason is that during the dry years the base of the landfill is the base of the gully and it's the one that's wettest the most so therefore it's been subject for the longest period of time and so therefore it's been subject for prolonged degradation so it stands to reason that the lower component will be more degraded than the upper component which also makes sense it also makes sense that the wells with less clay and more buttressable matter would be higher in the url to end ratio note that because they're fairly close in the similar system their approximate position in redox the PE plus pH is much the same but the background water is highly variable in redox and on this scale it's not possible to pick a variation on the url to end ratio so there's something going on with the background water in terms of its redox behaviour next slide please so I just want to talk now a bit about PFAS there's some fantastic work done by Nick Simmons when he was with the big EPA in Victoria that's Victorian data only and then there's work done by Gallon across all of Australia on PFAS in landfill lead shape I've ordered them in ratio according to Nick's works so as you can see PFAS is the dominant species in landfills as a mean across Victoria and also across Australia so they got quite good data matching really the PFOA for those of you who don't know has recently declared a category 1 carcinogen at the international level WHO so how long that becomes before the criteria drops in Australia reflect that will be interesting it's the second most dominant then you've got PFAS which is the one people are most concerned about is the fifth most dominant in Australian data and in the Victorian data so let's look at LBO2 and LBO3 so we've already heard that LBO3 is in a heavy clay environment with some interaction from interface drainage above LBO2 is in much more potrestable environment so LBO2 is not dissimilar it's got a bit more PFAS same concentration really it's got a lot letter PFAS but the rest is comparably the same ratio and this instance PFAS is the third most of the PFAS that occur most commonly in landfills LBO3 PFAS indicates a substantive source from another potential area not associated with typical landfill waste so you need to be aware that the ratios will vary from the means and you just need to have a bit of a look at it so that gives you some idea that that level of PFAS is above criteria the level of PFAS and PFAS together in the means would be above criteria if it was discharged into a waterway and exactly what's going to happen with PFAS criteria it will be interesting to see but at this point okay with criteria except drinking water criteria of course next slide so just looking again at where LBO2 and LBO3 is but then again look at KMBO5 so it's sitting down and slightly cross gradients if all the the hydraulic control here as you can see is controlled by the gully so the water will discharge basically straight into the gully and then along the base of the gully and out of the landfill into the stream the stream sits at a RL of close to 330 so you can see over a very short distance you've got almost a 30 meter 40 meter difference in elevation over a short distance so it is very steep there next slide please now this is from LBO5 and I haven't retitled my apologies I only knocked this in a few minutes ago because it's really in itself very interesting data so what you've got is that this particular data because of the saline background and the landfill leachate being less saline you're seeing responses to landfill leachate and background imposing here so we have a very very low sum of all PFAS to start with those units are milligrams so we're dealing with 0.03 micrograms of some of the PFAS in August 17 the data consistency is not so good on PFAS it's only just more or less started to be measured quite consistently the LDN ratio is 1.44 in September 20 there's a series of data with LDN ratio 1.4 for some reason PFAS wasn't done then so it was done for following around in April 2020 that's after the heavy rains it started so it would be nice to have actually had the back end of so April 2020 was the heavy rains and September so it was before the heavy rains it was the drought by September the drought had broken so it would be nice to have had what the impact of the LDN ratio was by the water pushing through the system the breakage of the drought so the data we have for PFAS is not consistent then with the LDN ratio and the other data so it's this stage showing that it's 0.089 as a total sum of PFAS is starting to come up in November 21 the LDN ratio is 1.6 and the sum of PFAS is 0.000 so it's 0.59 of a part in the billion so it's actually come up the really intriguing thing is this own nitrate is bounced a bit the LDN ratio has come up so now the things have gone down the potassium hasn't greatly moved this is because it is this problem we talked about is the system is sobbing potassium from the landfill I don't have other data to actually see what's going on here it's just an indicator but it's got some strong conclusions forming at the very start of the LDN the very start of breakthrough you will see PFAS so let's sort of the run on the talk let's just go to the conclusions so this factor so all the things I just talked about this site probably has an illiterate stratified mineral ilite smectite preferably sorbs both potassium and ammonium we can only conclude that if the LDN ratio becomes elevated then PFAS will also be elevated and at this point in time we need a lot more data and the PFAS data for LDN is good nice to see from a standard site rather than a site that has huge capacity to sorb both ammonium and potassium next slide please so in summary I want to make the following point very strong there's no single number indicative of leachate breakthrough you use the LDN ratio to go is breakthrough happening and then you look at the greater data so it has to be interpreted in regard to your conceptual site model you can't ignore the fact that you need to run a conceptual site model breakthrough fronts and aging can be done with the LDN ratio good idea what's going on what's happening how it's happening and the age of landfill and landfill leachate can be expressed beautifully on the LDN ratio with the plotted against PE plus PH there's no need to analyse other contaminants beyond the anionic balance that you do and if you want a few other indicators you know iron and manganese and so on until the LDN ratio defines a breakthrough front so all the monitoring associated with pesticides and pHs and DPHs is unnecessary with the one exception and that's PFAS provisionally if the LDN goes up from the landfill you should be immediately analysing PFAS because it's likely you've got a sum to PFAS breakthrough front curing and I haven't seen what the time is Richard but that's why you keep interrupting Richard I mean really I'd be on time if it wasn't for you it's very true Phil so thanks very much for that that was excellent I think we better move straight to the questions I think we've got some excellent early bird questions and then we've got a few in the Q&A as well so question number one have you considered the continuous monitoring of parameters such as pH, EC and temperature etc and their trends may be a more timely and cost-effective way of identifying breakthrough of leachate why did you hear me just discuss that EC is next to useless for monitoring transfer bake through it pH has some value but when you're in a more permeable system it bounces all over the place temperature in the aquifer less so, temperature in terms of leachate, yeah I mean it's got some benefit pH and EH together are very useful and Richard you'll be able to tell me if there is stable EH probes out there at the moment I'm not certain there is but there might be and in which case logging pH and EH is useful but not as useful at this point of doing ionic balance analysis gross breakthrough in a low water aquifer in a sealed system EC would be useful so once again it comes back to knowing your site conceptual model and knowing what is augmented support to assist the the six month or quarterly or annual monitoring that you're doing and in those instances the probes could be used to do that to support and look at what breaks through might have first happened as opposed to just having that annual or quarterly monitoring Thanks for that. Question number two consultants often referred to an L2N value of greater than 10 has been indicative of leachate impacts I can't find a source for that Yeah well nor can I because I happen actually I said that, nor has we ever published that the ratio is a relative ratio certainly over 10 it's really rare to have a groundwater that would show and some of the biotic micas with heavy fertilizer application on paddocks might come up with an L2N ratio greater than 10 so it's a fairly foregone conclusion that if you're over 10 you've got a strong likely impact of potraceable breakdown that's leachate but you can actually read a breakthrough at 1 to 2 or 1 to even 1.4 starting to occur and because we're looking at PFAS itself and PFAS is literally close to a million times more sensitive in detection limit than the L2N ratio then you really need to start considering not just what the ultimate breakthrough is but what's happening early in the L2N itself. Okay I think you might have answered this one in the talk but can the L2N ratios be used to assess for potential leachate impacts in surface waters as well as groundwater? Yeah to a limited aspect yes it can as long as you're interpreting the full data set so you'd use the L2N ratio in surface water as a clue for a massive a more massive event so if you see it moving in terms of that logarithmic temporal based plot then you go gee I need to actually have a look at everything else and it could just be that nitrates come up substantively because upgrading has thrown a lot of fertilizer into potassium nitrate into the river it could be due to a whole variety of other reasons you need to keep an eye on so in this instance it doesn't give you permission to not to consider the full data suite it's just an aid Yeah I would have thought the mixing processes and how dynamic surface water is it to be problematic That's why I said it will it will pick up a massive event so if you're seeing a change you've likely got something serious going on that you need to check it with but just walking along the banks any presence of macrophytes and bulrushes in a concentrated spot and they're not upgraded of that spot would make you think I've got a discharge point coming out from the landfill here Yeah number four if we had a robust liner for the landfill we could minimise leachate would that be easy Oh this is the philosophical discussion that we could waste a lot of time on all landfills should have a robust liner whether the liner is a clay base liner or whether it's a HDPE liner it is a question of different philosophy of approaches by the different EPAs I'm actually a strong believer in allowing the system to interact with the environment around it to allow it to interact slow enough the environment can adjust to address it like we just talked about previously having plants soak up the nutrient or having exchange occur so that the plume moves very slowly and is attenuated a liner the problem with liners is people think that it would be retained within the landfill it's estimated in the installation of landfill that the minimum number of punches you get is 2 per hectare and 2 per hectare into a sand based system can have a huge leakage rate so the problem with thinking that you have a robust liner is you stop monitoring and you think that your landfill is sealed forever unfortunately that's not the case what happens to liners over 50, 60, 100 years we don't know in terms of HDPE liners and that's the landfills of the 50s and 60s we now have houses on they're now being reused will the landfills of the 90s and 2000s that have plastic covers and gas extraction will we be able to build on them in the future or have other uses for them it's a really difficult question that hasn't been resolved and I'm of the opinion that the philosophy of controlled seepage is not a bad thing providing you've got the right environment to do it some EPAs will not accept that so if you said you're in favour of some interaction between I guess the leachate and the environment in terms of irrigation of leachate and reuse of it for that purpose what should be your name Annoying the PFAS problem for the moment that used to be a common scenario was you'd have your golf course on your old landfill and your new landfill was next door and you'd take the ammonium rich water and shined it with a bit of town water to drop the ammonium below 150 ppm and you'd spray it out on your golf course to reduce the use of fertilisers and that was a perfectly adequate use once your ammonium gets up past 150 and certainly 300 you end up with burning and scolding of sensitive plants particularly some certain grasses such as cooch so in that instance you just got to control the level of salinity and the level of ammonium in the water so yeah horses for courses but it is what it mostly produces is the salty fertilizer okay how to minimise PFAS impact on landfill feed stock and surroundings how to measure greenhouse gas emissions from decomposing waste there's a fair bit in this one there's a whole lot of models on that back question there's a whole lot of people who make a very good income out of doing that and so they're probably better people to talk about that so I'll leave that second component alone the first component is that yes we do have to consider carefully of getting PFAS out of our entire supply chain so the phasing out of scotch guards disappeared I don't think anyone will recall seeing scotch guard at the moment I think is no longer using PFAS in their products the use of Teflon I think is reducing they'll still come into landfills but they don't normally have some of the worst PFAS compounds in them the main problem is firefighting foam and there's two sources of those there's three all up there is the firefighting foam cylinders so they're probably best not to get those into landfills so quite a few of those come in from domestic and industrial waste the small one kilo ones up to the five or six kilo ones they come into landfills and they contain the foam the concrete from firefighting areas and other areas will have a wash out of it in a landfill as conditions change so receiving that feedstock into a domestic refuse situation may or may not be a good thing fire solids because of the use of firefighting practice foams throughout the catchment wash often to the the series treatment works and the input of biosolids to certain landfills probably should not be considered so stopping biosolids coming in until the biosolids are deemed as being PFOS PFOS and PFOA and PFOHEX clear would probably be most appropriate but so yeah that's several ways of addressing it Richard I would have thought you better put it in a landfill rather than sitting around in the environment but I think it needs to go to special landfills so it's a matter of discussion with licensing authorities is a particular landfill appropriate for that to go to you're quite right is that maybe there's enough biosolids that have PFAS in it then it might be more appropriate to put it into a model cell or an HDPE leachate collection lines system rather than an online system as PFAS been added to the biosolids reuse card lines not yet interesting okay is a good one has the reduction in food and green waste going into our landfills altered the leachate chemistry compared to 1990s refuse it's not enough I mean the reduction in food and green waste going in is yet to fully come through the FOGO recycling is just gearing up to the great extent now you still got vast amounts of potrestal matter coming in with construction lumber with great stumps and garden waste that may not be suitable for composting and the like so at this point it's too early it might be appropriate to look down the track if we reduce the amount going in and we don't then we can come over and reuse it again more rapidly so we certainly harvest the methane from it and the methane harvesters the guys who run a business in putting it into power stations actually don't like HDPE lighters they much prefer caps they don't like HDPE caps they much prefer clay caps it's much easier for them to handle a clay cap system and more efficiently get the methane out than the HDPE systems so it would be quite interesting to see what happens over the next, well I won't be around to see what happens over the next 40 years with what our landfills do but some in the audience might and I hope it will be interesting I hope they keep using the elder end ratio film next one re-injection of condensate into landfill cell versus treatment alongside leachate look you just heard me talk about it a while ago it's quite common to more so overseas in Australia to re-inject into the face dust control and so on as I said before for some reason it doesn't seem to go up in TDS high than 5 to 8,000 it accelerates the rate of methane breakdown and potential which is good for the methane operators coming in over the top now one other treatment you might do spraying onto the top of a closed landfill is also quite acceptable as long as you're conscious of the TDS TDS and the amount of ammonium in it and then there's many landfills where the closure conditions have allowed them not a lot EPAs are rightly conservative but the data from the 80s is not being actually published or well presented to show that this was successfully done so yeah not a lot but you do have to manage TDS and you have to manage ammonium as I've previously stated but there's the similar restrictions for sewer so you've got to manage the ammonium and TDS levels for going to sewer anyway and some of these treatments could be substantially expensive for the community where natural treatments might be more beneficial I mean wetland treatment as well is to run a longitudinal wetland around the base of the landfill or off-sale elsewhere before discharging through off-site and having a whole series of of of macrophytes to actually polish it so the increasing interest in in phytoclosure and phytocaps and phytotreatment of leachate is occurring at the moment are there any states in Australia where the L to N ratio has made it into the guidelines um I'm um I have no idea Richard I was actually quite surprised that he found out about a year and a half ago or two years ago that a lot of people use it and it's called the mulberry ratio so I knew our company uses it and a lot of our staff use it but I was surprised it's had widespread use um and the EPA seemed quite comfortable with it and its understanding presents landfill leachate chemistry talk to the VIK EPA a few years ago talk for hours so I bored them bored them silly I think um but I I really don't know so I can't comment but it appears it's now accepted practice for groundwater monitoring um are there any situations where particular land for sites where the L to N ratio should not be used um no okay in low salinity um it's useful very useful um but the the TDS variances and EC variances aren't as useful in high salinity it's almost essential so you've got high salinity backgrounds and you want to you want to pick small movements of ammonium nitrate potassium to see when the breakthrough is first occurring it's very hard to see it in a high background and a high background the ratioing of the complex ratio like this shows it up um and current and possible roles of radioactive traces that already exist in landfill leachate yeah this is tritium and cesium um that you mostly deal with we shouldn't have any other radioactive traces in there because they're not supposed to be um low and mid-level radioactive waste not supposed to be disposed into metropolitan landfills but put all that aside um what this question is asking is the atmospheric testing that occurred during the 1950s um resulted in an increase in cesium 127 an increase in the tritium the radioactive water um to occur above backgrounds um so any landfill leachate migration into groundwater that's older than the mid 1950s you would be able to see cesium um when these 7 elevation occur it's more expensive to do than um the uh ionic balance of which the LNM ratio is based on um and it would have limitations into quite a few landfills where you're dealing with um unconfined aquifers where the water is you know of the last 50 or last 70 years so it certainly has a major tool in groundwater monitoring but in terms of landfills it's um a limited application and more expensive than ionic balance test okay so just to clarify to everyone that's atomic testing the exploding of the bombs that led to that oh sorry atmospheric testing of atomic bombs yeah can biochar make leachate that does escape less dangerous yes um we use biochar in bioreactors at different points of time what it can do is hold the nutrients long enough for the the macrophytes so we tend to run a biochar a permorative barrier with a macrophytes on top or slightly of it if the ammonium levels are too high and we need to just hold it back and give plants a bit of a go you've got to choose your char appropriately ammonium some char's are not so good at absorbing ammonium quite a few are so yeah it's certainly a potential solution now we've got done just clicked past two o'clock we've got nine more questions to go are you happy to stick around Phil? maybe just take the highlights Richard there's quite a few participants still there so I really shouldn't go past about quarter past two okay do you have any guidance on how new practices in pre-treading waste and adverse thing and the adverse things we are finding especially through the removal of metals from waste reducing availability of iron and waste regarding different ways to the past with adverse effects e.g. H2S production yeah look if you take the iron you can increase the H2S somebody knows their geochemistry here there's enough iron in the formation and there's enough iron coming in with the clay so when you use you run a landfill and you put day cover over the top or you have interim cover so the H2S would rise into the day cover or the interim cover and it would then reduce the gyrthite that causes the red minerals of the soil colors so the reds orange yellows oxidized iron minerals so a reaction would occur between the H2S and the oxidized iron minerals in most instances H2S is not a problem in landfill gases that questioner clearly knows currently and by removing the iron the question implies could it be a problem in the future as long as day cover is used and the soil co-dispose with it it's unlikely to be a problem as such the landfill of the gas meters themselves that we go and typically the 5 and 1 meters do have H2S on it and good operators should be just keeping an eye on the H2S as well but I've never known H2S to occur from the existing landfills but are there any aspect that the questioner indicated was that there's lots of iron in the landfills alright next question is thanks Phil you mentioned looking at fluoride as an indicator of influence from town water from your experience what is the range in concentration in town water typically it's 0.8 to 1.5 to be effective on against gum disease and all those other problems that I got growing up mudgy without fluoride in it so typically it's 0.8 to 1.2 it can be a little bit lower but don't forget it's been mixed with what you're putting in so it might express somewhere from 0.6 to 1 but normally fluoride in most aquifers is below 0.4 okay now Bobby Wang has got a question can the L2N ratio be applied to contaminant plumes from other sources EGL, NAPL and dissolved phased plumes associated with petroleum sites or nutrient plumes associated with wastewater treatment plants it'll definitely pick up nutrient plumes, patresable material put it elsewhere such as mulch compost the chemistry approach is the same except the fact that petroleum plumes don't produce excess potassium and so typically in those environments just having the site conceptual model and understanding that sulfate will fall away and nitrate will convert to ammonium as the oxygen consumption occurs so the peculiarity of degradation of patresable material is they produce the combined combination of high potassium and high nitrogenous species so it makes a very peculiar leachate plumes that is not the same as hydrocarbon plumes even though it'll produce some of the same redox reactions but it is the same for other organic waste such as mulches and compost the manures will tend to have more phosphate in them so you'll see a slightly higher phosphate associated manures and night soil but night soil dumps just about all pass through the plume stage at this point in time okay James Stewart from Always Carbon a great session thank you Phil and Hydrotera curious if you could comment on what is best practice for treating leachate escapes when it occurs EGFPFAS is detected what is the best practice to do about it this is an evolving science it's an excellent question we don't yet I mean the EPA is across Australia and particularly Victoria to their credit have funded a lot of investigation of PFAS and leachate to try and understand it the current understanding is accepting certain circumstances the risk to the sewerage systems is low because I'll look at putting leachate into sewer individually you then got to consider what is the risk to other receptors apart from pumping it to sewer so that could be via groundwater to surface water or via groundwater to springs or via groundwater to swamps in that case it's a bit more of a solute transport approach and to see what the concentration would be for the receiver if you're using and this is no different to phyto mining if you're using plants to uptake the leachate and you're using I suppose primary treatment would be the macrophytes before you move into secondary treatment and polishing so if you're going to the macrophytes in the first bay and using that as your treatment strategy the PFAS unlike chloride solvents which translocates through the plants and photo decays at the leaf do not photo decay and they do pass into the plant but get stored within the plant tissue so you would potentially if you're concentrating some of the more dangerous PFAS substances would harvest the plant and send it off to a number of thermal desorption disorders which we have throughout Australia and they would be pretty keen to get a certain amount of dried plant matter to mix in with their soil stock to put less energy into the system okay just a few to go about four or five, six in fact two great talk thanks have you tried to compare or compliment the L to N ratio with isotope data I think you might have answered that I haven't directly answered it but yes I mean that's a good research area the problem I have is that I'm a practitioner and I'm fascinated by the research components but I can only do the research of client derived data and the clients are only going to spend what's necessary to spend Theresa Klingelhofer can the L to N ratio be used to demonstrate the end of an aftercare management period and have you used it in that context, good question yes it can you'd obviously derive a threshold on what the ratio is and how it behaves with time or you'd use the temporal based logarithmic scale to show a downward trend so yes it definitely can I haven't heard it used on that basis because modern closures of the mega landfills are yet to, I mean they've occurred, I mean you've got Ptolemarine being a classic mega landfill but they're not at the point where their 30 to 40 years past their billing stage to the point where you can see that the lead shade is decaying to a satisfactory safety point so I'm not aware of any of the mega landfills being at the point where this could be used but there's no doubt it could be hey is there other indicators that can be used for town water in areas where fluoride is not added such as some LGA's Queensland well you can on the basis that usually the water that you're putting on irrigating on will have its own signature and you then look at some of the ratios of other cations to look at what is the mixing if they're putting quite a bit of water on you'll see a signature come through that's different the L2N ratio might be a little bit similar a little bit lower but the other say that the Florida sulphate and calcium to magnesium ratio will be very very different here's a good one for you Phil from Dana Wendell we love the L2N mouldy ratio there you go thanks Dana okay next one Mark Peterson thanks Phil the source of elevated tritium includes the waste itself old exit signs, watches etc typically well above background or old ATM atmospheric levels e.g. Tasioli hey et al tritium has a tracer of leech contamination in groundwater I don't disagree and I apologise for not mentioning that I still default back to cost you can do an ionic balance it varies from lab to lab but anywhere from $35 to $50 to get a tritium analysis done is quite expensive well Phil we're through the Christians thanks very much and thanks very much for everyone who's stayed on still got many people here great to have you on again Phil really appreciate it no it was actually I'm glad you asked me to give this talk Richard because it was a good opportunity to revise and to communicate and I need potentially write in the paper to communicate to fellow professionals about further ways of utilising and interpreting and extending and improving interpretation of the ratio and also just you know if people got pre-fast to the ratio it was going to be very very interesting because the only site we've got it on is a site where it is complicated for lots of reasons that I didn't go into but it makes it very hard to kind of work out what's happening so yeah I really appreciated this Richard because I was on until a couple of years ago not aware of how much industry uses it so to improve the ratio is for the benefit of the industry as a whole so thank you also shows the value of a really long monitoring data set I have to say yes it does Drew Marsh to finish off Phil says that was fantastic and Mark Peterson says thanks for a very interesting presentation so plenty of support there Phil so thanks very much and we'll leave it to the industry alright thanks Richard it's all the viewers 10 days bye bye