L/N Ratio Advances: 30 Years of Landfill Leachate Monitoring

[00:00:01]well welcome everyone to hydro's latest webinar today we've got one of our favorite presenters Phil mie back again thanks Phil and Phil is going to be talking to us about understanding landfill leap further developments of the L to n ratio after almost 30 years of use before we get into this 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 hydroa respectfully acknowledges the boang people of the kin 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 Earth Sciences or easy as it's known these days um 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 wager waga Council in 1992 here's published numerous papers on different aspects of landfall 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 mvy ratio in 1997 he revised the ratio at the ISA conference what does Isa stand for Phil International solar waste Association thank you in Wellington New Zealand to the version now used since then the Eldin ratio has been adopted widely as a manage management tool for landfill leee 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 uh in order for you to raise them please use the Q&A button at the top of your screen why does Hydra do these webinars well we actually enjoy them it's a good way to keep in touch with people like Phil um we get to share knowledge facilitate some education and provide a forum for industry leaders about that um 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 um Richard and I really want to acknowledge your team for the great work they do in in putting these seminars on and ensuring that the industry has a chance to hear from a whole variety of different people um in regard to measurement and Landscape so um thanks and well done to your team and thanks for the invite for me next slide Richard briefly we're just in talking about landfill leech eight we do have to have a bit of a discussion about landfill types the landfill chemistry both in how gas and leachate is is derived um why the l to n ratio was set up um what is the new tools for assisting in the Elder in ratio and um then closure of the S um you've heard my experience I don't need to talk about that greatly um but just of note the first paper I did in 1986 was with Roger Parker um who many many of you will know quite well and we did one of the first papers of probably the first paper on understanding bit about Landfield leachate uh in Australia with reference to the bwood casino which is built on a landfill um um the original stage one good Cena next slide please landfill types and impact on waste chemistry so it's important to understand a little bit about um what happens with pressible matter as a breaks down and then to understand a little bit about landfill types so this session we'll just concentrate a little bit on understanding the different phases of the land pill so the first stage is the aerobic stage where o is still present and dominates um and there could be a slight drop in PH associated with that um the next stage is the fermentation stage this is the beer brewing stage where you get a lot of CO2 um produced but no methane and you get the consumption of nitrate the next stage um is anerobic living off sulfate and um Gite so rust within the landfill that's why landfills that are deeply into the methen stage actually have a lot of black covering of iron which is actually pyite precipitated where the rust used to be so they're the basic stages of a of a landfill in some degrees they're also basic stages of of organic plume contamination moving through groundwater need to understand that organic matter is made up of a certain ratio um of carbon nitrogen phosphate sulfate and potassium um and the cells actually need that um the microbes need that to break down so they will plenty of excess carbon so they'll release that there's plenty of nitrogen they'll release that they keep phosphate cycling around because they need that so you don't often see elevated phosphate associated with landfill leap the sulfur they need um or it gets precipitated pyate so the phosphate and sulfur are held within the landfill typically and the potassium and nitrogen species are released um mostly uh well particularly in the case of nitrogen um to groundwater and potassium entirely to groundw so the really weird thing about it is that pottassium because well next slide please Richard suppose better stop talking and just move along a bit in the slides and stay in order um so the thing you understand about pressible landfills and um in New South Wales pressible are defined as municipal waste whereas elsewhere in Australia pable is any organic waste um is hydrocar is that really not much comes out of them in except they very nutrient rits so hydrocarbons get broken down within the landfill particularly the aerobic stage and then into the anerobic stage PHS and tars are also broken down heavy metals are immobilized by The sulfur in in versions of of pyite or sorbed on six oxides which is your rusts which cover your your iron during the aerobic stage your pcbs and your p and your pesticides um tend to greatly um stick pretty much to the organic matter and the clay within landfills um chlorinated are a problem um though they degrade in anerobic or faculty aerobic conditions the types of conditions in landfills can result and this is why it's highlighted um in vinyl chloride so that's one of the exceptions to what comes out and as we'll see later there'll be bit of a discussion on what Earth does pasas do so landfill leeche looks pretty nasty really but it's in terms of hazardous compounds the greatest Hazard is nutrification and absence of oxygen so you can see a lot of bubbling going on there is um this is a landfill leech a collection Pond and 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 leech a is the age of the landfill um the input into the landfill and the cover and they very important to consider because they have different aspects on how the Elder end ratio May behave next slide please so you look at an AG 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 mji small town in Western New South Wales and I used to love going to to the landfill as an 8 to n year old collect all the all the old pram Wheels to make Billy carts out of off and the fires were always going at the landfill so it was unsightly and located out of town because it was burnt um it didn't have Ibis then but it certainly had rats um so it meant that the pre-1979 landfills have a lot of burnt material not much petables so lots of metals and PS are in them so you get a different style of leap from 1979 to the mid1 1990s landfills were known as sanitary landfills they used clay liners um they had a lot of pesses in them they weren't burnt um they were often Gully landfills and will'll come back some of the problems associated with those um in the postn mid1 1990s there was a movement to inment of waste with gas extraction still had lots of pesses um but the circumstance is that they're now contained within hdp liners um both top and bottom um lots of redevelopments occurred on the same sanitary landfills uh predating the 1990s and the burnt landfills whether we'll have development over the interm landfills is an interesting question so increasingly around the world now there's a movement away from in tement to to controlled um a leachate interaction with the environment which we won't get time to discuss today but part of the problem with intern landfills is not a set and forget as as people thought when they were designed originally next slide please so what's the input material um so defining a number of different landfill types so you've got a municipal landfill that takes municipal waste that street collected rubbish waste you have a huge amount of addressables in it you have Plastics you can have all kinds of things you can have a lot of past W streams um not just fire extinguishers but Teflon um all the food boxes from pizzas um the microwavable popcorn the disposed carpets with with Scotch Guard on them etc etc um solid waste with pressible which which means you've got um tree waste cardboard Timber um coming in together with dirt so they have significant amounts of pressible then you got soil only which has small amounts of pressible but not a lot and then you have special monels um that might have Ash might have different types of specialized wastes um we had a monocell on a landfill area that just had um laminated wood and MDF um and so yes not all mono cells don't produce pesses you got to look at what the monocell does contain next slide please um it's also important to understand the nature about cover a little bit the covers if it's permeable you get gas and water diffusion in and out and if you got a good grass cover um the methane is actually bigraded to CO2 except where macroporosity is and then you have impermeable covers to which you pull um 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 affect does also affect the leachate as well quite a few landfills just before moving on I just want to touch on another issue sorry just another few seconds please um part of um cover design and and landfill construction is often leachate is reticulated um the TDS does go up but intriguingly the TDS seems to bottom out somewhere between five and 8,000 doesn't go any higher and we think that that's to do with some of the geochemistry and microbial reactions involved now next slide thanks Richard um Lee plume chemistry so this is we've looked at this slide before Richard said do I do I want duplication well act fact I do because it's important to understand that this material um will be very reactive um 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 urif of our our streams though um mccrites love it so you often find on some of the quite older landfills lots of grass growth that is stripping out the nutrients in it and that's why phyto caps are now much more designed for landfill closure however it doesn't address the past problem next slide please so you can see here is an old um paleo Channel and it what you see is that that green little Oxbow it's a former Oxbow um Lake of probably some 30,000 to two million years ago um and it it comes in under that Center fence so it's dipping away underneath um the landfill's built over it and you can see the methane has migrated vertically up from that lens and killed the trees so it's the only killed it is the absence of oxygen not methane is not for trees direct directly toxic it's the absence of oxygen that's killed it but you can see where the leeat expressed to the surface as this lens um slopes sort of 90 degrees away and expresses the surface that you've got large amounts of grass to the fence and then in the farmer's padic Beyond even though it's the middle of a of a drought you've actually got a green pck there uh for the animals so the grass can tolerate um much um more aggressive methane Rising because the Oxygen's penetrating down the 30 or 40 cmers and the microbes are converting um that methane to CO2 at the level of which Oxygen's coming down trees having deeper roots and a greater demand demand aren't able to actually knock um uh get the oxygen penetrated more than 30 to 40 C me do and so can't knock the impact of that methane so you can see that the the neut that the leachate 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 um from Roger and and our paper um together with the client um back in 1986 and it was one of the first Lookout 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 fairway up the concentration in leachate of any particular substance coming through the key thing to not is it has what's called a chai square distribution which means it rises reasonably rapidly to a maximum and then 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 with the landfill um and if you're looking at as simply as methane or CO2 or even as leate itself typically it hits um that maximum between five to 20 years if the landfill is less than 10 meters deep if it's more than 10 meters deep you need 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 aerobic bacteria breaking breaking down what's available um they need oxygen to do it they consume the oxygen you move to the next stage which is the start of fermentation so phase two is the first part of anerobic phase which is a fermentative phase which doesn't produce methane it produces CO2 um you get some some Arch and a little bit of um anerobic bacteria producing hydrogen during this um then you move to the transitional um phase to to the full methen phase and that stage you you hit Peak CO2 but you start to have methane coming in and then finally um you go into the maximum um methane phase which takes a per period of time you're moving more into 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 that anerobic phase at phase four 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 at different different speeds to other cells or Pockets can be faster or slower depending on the amount of of clay and soil Co codeposited so you can get quite a degree of leap variation within the Le landfill itself next slide please so this is sort of how and this is um for a spill but it's a good slide to show that the redo zones Associated within um an organic phase moving out but in this case it's it's um the organic reactor itself but you still have those so same phases so you've got oxygen dominated Zone a nitrate dominated Zone manganese so manganese and ion go into solution sulfate gets taken out of solution and finally meth Genesis next slide please so just revisiting that again what you've got is you've got different reactions occurring um with the medium through which it travels and the very first part the the front of the front is where the native cads are displaced and they go up talk a bit more about Native CS later but also at at the nitrate attenuation stage there you start to see ammonium coming in but you start to see bicarbonate come up which is the reaction of the micros producing CO2 and at pH is 5 to8 CO2 will Express as bicarbonate and then you move move into why you end up with manganese in solution and why you get ion in solution and finally sulfate dropping out of solution next slide pleas you want to just clarify to people why we're moving through these phases so um certainly um the reason why we move through these phases is this is why the l2n ratio is used and it and it reflects some of the chemistry because the TDS and pH and EC to some extent become poor indicators as they change to different things um so understanding the site conceptual model of the phases of the leachate including how it reacts with the environment so we'll talk little bit later about absorption and Elite and what Elite does in terms of the ELO n ratier so it's important to understand that um 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 um ahead uh 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 you get different bacterial populations emerging As you move into this sort of oxygen depleted environment most definitely um when you're in the aerobic you have the aerobic heterotrofos you'll also have your um within the landfill itself you'll have your alkane degraders and your napthalene or pH degraders and they're aerobic bacteria um so they will work in that sector um then you've got your denitrifying bacteria um and it changes again to so if you've got for instance um you move from the oxidative phase to reducing phase on iron you'll have thiobacillus present um so not thil you have Dulfer vibrio present and Dulfer vibrio um does the reverse reaction it takes sulfate and breaks it down and liberates energy um to other bacteria het tropes to able to feed the s of vibrio so you end up with a circumstance of um you're releasing um CO2 and CO2 release to the to the meth Genesis um which will use the CO2 to strip it and take energy off and produce methan so you've got a series of microbial um processes that that you go through where you're dealing with complex organisms living together so by the time you get to Method Genesis you're actually at what's we call swamp gas so you're producing the natural swamp degradation process or the process that makes what You' be familiar with um the black shales so the the Marine muds um tolerate a higher solinity but they also have the same things they have have within them um Dulfer vibrio um and the same interactions with the anerobic hetes and the and the the methen bacteria um to create this community that that moves energy around for the benefit of all all right thanks for the clarification so let's just go back to the biological breakdown of plant material so Richard was a slide too soon really but um so you've got the microbes that that um want to break down to get energy but also to get the nutrients they need so so salinity goes up in some instances it does depend on your background solidity so down here in Melbourne for instance um if you have a landfill that's on the silan so the the hum Veil siltstones or um the mudstones um you have an issue where the local groundwater is actually quite a bit more salty than what the landfill's producing um and same with on estery sediments or up in Sydney on the one of matter of shaes or laram Bean shaes you you end up with a circumstance where the surrounding water is is actually saltier than the landfill and in those instances very hard to pick out when whether a front is passing or not and that's why um having ratios explains all that um biological breakdown of all plant material not just what's in the landfill produces this as does you'll produce and be in color in leacha it'll be Brown to um brown green there'll be gas discharges it'll be elevated B biological oxygen demand because of the tannin and the the fennels that are released by the plants and the Turpin um so it's not just landfills that does this it's mulch leache it's decaying litter on the soil it's night soil which used to be used around the edges of old landfills and night soil is the D can collector which phased out in the late 1960s in Melbourne and Sydney um but any um manure um will also produce it and that's why manures go to anerobic to digest us from large daies as well as municipal waste so you need to be aware that what other sources might be around that could cause this but the key thing to understand is that elide pottassium and nitrogen species are rare in groundwater particularly together as both micro and plants do what they can to sorb them up quickly now there's some exceptions the Paleo Waters in Inland Australia will be rich in nitrate not ammonium because the acaas and a cash Arenas During the weter period of 200,000 years ago actually um laid down nitrate so most of our Inland waters are nitrate rich but potassium poor um so you can still the Elder end ratio will pick that up um next slide please but just before we do so under you know things like Dairy affluent like in New Zealand you get those big nitrate or 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 so well yes you can pick it because in those systems particular in the can caner Plains um they're low in potassium so you can actually see it you want to get it Hummy again you sometimes um you'd want put a bioreactor before the river and use the bioreactor to um nitrify what comes through or you actually do a denitrify nitrify process because you got to convert it to ammonium first um and so their problem is a nitrate discharge as is Europe um right across Europe they have a major nitrate plume problems um so you've got to create set up a bioreactor area and you actually run that nitrate plume through a through a bit of Peete with um some appetite uh or or crushed rock phosphat so you're not releasing phosphate to the water but you're making phosphate available to the microbes so a combination of Pete and phosphate would be your bioreactor um to destroy that nitrate or reduce it to nitrogen gas but it's got to go to ammonium first so um there is a process by which you have to do that um and it's hard to do at scale because you need a longitudinal bioreactor running all the way beside the river um one of these was installed in the Coburn Sound area associated with the fertilizer problems in West Australia um all right maybe we go SL getting slightly off topic my fault okay um so exchange on Clays so Clays are charged particles and I won't go into all the aspect of clay chemistry but they have a net negative charge across them um CES oxides 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 cats from the weathering of rock um and those catons 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 um and ammonium is is particularly po preferred with zeolites um and and certain biochars and various other things um but the thing to note is you do have to understand a little bit about your background's geology um so the um um this the the Hume Sil stones for instance and and many of the Meta Meta sediments going all the way up um from Victoria into New South Wales the silarian sediments they have a lot of ilite in them or they have a elite smectite which has a preferential for sorbing potassium um but biotitic granite in the highlands of um Australia Northern Victoria and Southern EF Wales um releases potassium so it's one of the few instances where you'll get slightly elevated potassium groundwater so understanding your geology is also important next slide please Richard the hydrated ionic radius so what what exactly is that I cut all those slides out Richard but uh all right um what you're dealing with is for instance sodium doesn't have a particularly huge um ionic radius but it 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 stat so many waters on each other they disperse clay they push clay apart um magnesium has a small tendy to add a bit of water onto itself um calcium not so iron and so calcium's got a two plus valency uh and so that controls um the the charge density I'm sorry I've actually got that ratio right so you're appropriate to raise it should be hydronic radius divided by the valency so my apologies so well spotted Richard um so then it goes all the way up to your your three charged ions in solution so your three valencies such as aluminium um with a three plus charge is quite preferred but when it's al4 it's only a single plus violenc and it's and when Al is in solution a very high pH um but it has much larger hydrated ionic radius so it tends not to be necessarily um well preferred on IR exchange positions so that sort of explains the basis of the I don't have actually time to go into chemistry at all quite right quite right we'll move on thanks um so this is the original dun more data came from the paper and unfortunately we actually used um something that young people would not know about is overhead projectors back then so this was a shot from a uh a plastic overhead which you put onto a screen that projected onto the wall so the that 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 but it's into a recent sand um mine so it's backfield in the sand mine there's no liners it's sort of a a 50 system that occurred um and you can see a substantive breakthrough front starting to occur in about 1995 um where you you bod goes up the fermentative phase your your bicarbonate goes up so you're producing masses of CO2 um your sulfate starts to drop in that that top um image so it displays all the classic Flom Behavior so I'm not actually making this up this is not a load of of textbook bullar this is actually what happens um 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 or they just dilution events due to heavy rainfall and evaporative events or were they um due to other factors um but just before the front goes up um you can see the sort of steady period um you can see the TD for some reason dropped and then up it goes uh and then you've you've got um 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 you know we had 20 well that stage we had you know four or five years of monitoring that site we monitored for in excess of 20 years so we contined to get very good data from that particular side next slide please so out of it came opportunity to do some plume Behavior modeling so the first paper talked about ammonium plus potassium divided by calcium plus magnesium plus sodium so it was what was in leate divided what what is the common native cats potassium can be native but it's normally sapped up by trees pretty quick so you tend not to get them 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 01 through to um 0.01 very well so if you multiply by 100 you now have a number that falls between one and 100 and the Brain handles that much better than 01 to 0.01 um 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 on those it's it's unitless so it's Milli what do they call it it doesn't matter if it's if it's in this instance we use we're using milligrams because we're just lazy don't want to convert um but it wouldn't matter because what you're looking at is relative difference which will come to an a sec mostly it's universally adopted um in the mass balance not the charge balance okay and we which 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 um next to ammonium so you can see that the Elan ratio kicked off before ammonium did um it's got it it had a little downturn as did amonium so was that due to out competition by the native cat IR being released as the modium got absorbed well I suspect so um then it goes up um and as you can see the amonium has a dip as it moves from the fermentation um stage to the mythen stage but the Elin ratio just continues to De climb it doesn't reflect that um in change in rate um the pH goes up um the TDs is sort of come as you know bounces all over the place it's not telling you anything greatly in this environment um but the Ln ratio is showing it's predicting that the front at very low concentrations of breakthrough and is consistent in you're predicting Its Behavior um as you can see that the bod goes up much the same time then it comes down the sulfate starts to come down from that point of time um you can actually see the sulfate recovering again after hitting zero so this is a fast plume breakthrough because it's in sand and it's poorly capped and poorly lined next slide please so let's talk about um my poor spelling with YT but anyway um let's talk about some U recent developments on it and um let's not talk about my poor editing um this is a landfill uh that's been INF fields from the bottom upwards um bore hole 15 which is right where Richard's cursor is we must have practiced this um is an indication of um um when where the last lot of filling is and there's two adjoining properties there um one's oh three or four adjoining properties um you can see there's a few fruit trees around those scattered trees are fruit trees um there's a bit of gardening um and there's some chalks which you won't be able to see and there there's GB background BS of gb5 gbo six and or three six and seven on the two different properties so let's go down to the next slide please I'm going to have to get rid of Richard's image so I can see this properly no offense me Richard um so the one property is ball 5 um it's got an elder n ratio of one um it shows low phosphate it shows um low ammonium it's an a rated system and low nitrate it's got a little bit of bicarbonate in the water it's got classic situation of having pottassium lower than calcium magnesium surprising enough it's magnes it's a sodium magnesium dominated so in terms of Ideal growth we'd probably want a bit more calcium in the system um but if you look across to it um you the fluides also low so that's a brief run of quick understanding of the in ratio how it looks at that it's saying it's got a ratio of one well next door's gone up to two you go okay there's a problem there 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 um bicarbonates come up um potassium appears to have come up um but because we got phosphate up um and the overall TDS appears to have dropped a little bit based on what we we've measured there simply because there's some out competition and bicarbonate we're actually dealing with a system where they've added fertilizers they're doing a lot to get their garden and Lawn to grow um they're not putting Town Supply watering because the fluid's not up um so that ratio doesn't reflect and they may even be using sep seed tank disposal um so that doesn't reflect landfill traveling up gradient um it's simply reflecting the site Usage Now if you go to ble 15 this shows all the classic indicators it's actually either in the edge of the landfill um right in it or on the very very edge of it so what you're seeing is a breakthrough flood 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 balancing round in the system there's no fluoride to indicate Town water um ammonium is high and going up sulfates going down and sure enough the Elin ratio is going up uh reflecting the fact that we are producing we're still in active methen phades and we're producing a lot it could be a front that's passing or the very edge of the landfill itself and just reading so you'd 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 oldn ratio drop um the bicarbonate is still up which indicates CO2 is still quite Rich um the ammonium is starting to drop and the potassium may have peaked um so nice lovely classic data set showing what's happening with the older n ratio what the ratio means is irrelevant in terms of the number it's Its Behavior that counts so does the elen ratio apply to creekwater let's have a look at this example next slide please Richard so here we have quite a bouncy Ln ratio it's um it's certainly above one it's above two and it's getting to you know getting above five but if you run your eye across there's no ammonium potassium actual fact is can be high when it's low comparatively but potassium is just really really low the overall TDs is low um sulfate is unusually high so it's in a urban area um because it's not an old water it's it's it's a young water I should should have put fluoride up so we could have another look of fluoride and TDS um but you can see nitrate is periodically very high so the elen ratio can be used in ground in surface water scenarios but you've got to use it with great caution and you potassium doesn't not normally Express to rivers and ammonium is rapidly converted to nitrate in the river system anyway um particularly an a rated system uh and you'll find lots of plants mccrites your um your junus and your um um um bull rushes and so on growing on the banks in the area that the discharge occurs so in this instance the Elder and ratio is telling you absolutely nothing um and that's why you need to look at if you're going to use the surface water um you've got to have a pretty good idea what the water is doing so what your the Ln ratio 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 some what I said later I at the very next slide um so here we plot the Ln ratio on semi log paper with time and you're dealing definitely immediately we we see a couple of significant things um the ratio is variable across the monitoring Wells this is monitoring Wells associated with a landfill um you've clearly got one is undoubtedly leachate of some sort but you've got another one that's bounced along from may or may not be Lee to suddenly going very very high and the first conclusion would be it is Le so let's go and have a look at it next slide Richard so we're dealing with two BS here ball six which is um on the Southwest next to bohle 4 with a um orange notation and you can see that the landfill is the whole area in the middle and Bol 6 is not supposed to be directly in the landfill it is beside a roads in a dipp in the roads so I just give you that little indication B is also beside the road and dip of the road and it's either in or potentially in um landfill so we'd have to check the logs for that so I'm just going with the data we have it in front of us at the moment um and the groundwater appears to be um up gradient in this Direction moving through the landfill which is all that bit between 10 and six 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 ammonium bounces a bit but it's high and could be falling sulfate comes in and disappears completely and then maybe St need to come back bicarbonates um is dropping off in the in the back half of the monitoring period 2018 um and phosphate is close to zero and and fluoride is low let's look at six so ammonium we run our eye down ammonium and it's you 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 um and then jumps even more then drops back to low and it jumps again if you run your eye down at phosphate you'll see that phosphate was low and suddenly went ridiculously high and the fluide bounces a lot so we asked the landfill a few questions they put a mulch out in the landfill and across the the face of the landfill they'd fertilized The Mulch and they' sprayed it with Town water so in actual fact then we looked closely at the well construction and wasn't one of our wells I have to add it was oted to the just below the surface half a meter from the surface and it was in a CV and so the water that ran down the cul 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 sight activities on the surface um so it's quite intriguing just seeing what you know what the data tells you when 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 Eldin ratio tells you is go and have a bit of a look before you automatically conclude it is actually landu leate it's certainly pressible leate signature not a doubt about that the loading of phosphate indicates that it's got fertilization as well and the intermitted high fluides uh 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 and leasing with the operator of the site if it's trending down the old win ratio do you sort of say well we're heading in the right direction do nothing or how do you cont a lot a lot of these are audit data they're not necessarily I was the consultant giv me the advice but um 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 um and that's good it's we're expecting to see that but you'll start to see more a bit more settlement going on and so forth if you manage 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 plums passing so it's good it's dropping um how close are we to a sensitive um receptor a Waterway um decides whether you do an intervention or not um and whether you have within your management system and attenuation Zone depends on that as well so the advice depends on the type of landfill obviously your license the type of landfill and the proximity to the sensitive receptor and let's just look at further interpretation AIDS the other the show and this is not just plotting semi log but this can help you in multiple interpretations so here's a series of different aged sand uh backfilled sand mines so back filled with Builder Rubble which obviously includes pressible matter um it's quite an old landfill it's it's over in wa it's in Sans of course um the site is as defined so we couldn't get an upgradient well very readily because we couldn't drill off site um but we got some pretty and it's so long ago that that 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 but anyway 's mov on um so what you've got is a series of um whales drilled into different wastes um sometimes not fully within the waist so when you slotty across zones it's always a problem um and in an environment like this with sand and back fill with Sandy waste it's often hard to work out when you're drilling whether You' drilled out or not um so that it's across the Guilford formation so a Sandy clay down into into a clay to Sandy clay zone so it's it's a fairly low low flow area next slide please so we've split it up according to different classes and also done the L to end ratio so you got background where the ratio is a little bit higher potentially we've got impacted backgrounds that um is resulting in a drop in the eloin ratio and then we've got a series of different landfills with different behavior in the oldin 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 eloin ratio against PE Plus pH and we've done this a number of times since I'll give you some number of other examples so this um allows you to split the behavior of the ratio according to the Redux conditions um so you've got a series of classes and you can see that they they cluster and they fall out into quite separate um domains I'll now preempt Richard's question and explain what PE is next slide please so PE is the negative log of electron activity so effectively it's eh should be lowercase H um measured by your or um probe which I'm sure you can buy from hydr Tera or rent from hydr Tera if you don't have one already um and you calibrate with Quin hind drone on a and it operates off a platinum electrode so it produces a reading in molts that reading whether positive or negative if 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 Redux state of the plume and that's why by plotting L2 to it you you split aspects of the plume that might have same L to n ratios but different Redux next slide please next sline so this is another example um it's a site that is a former Gully fill site you can see there is two lee8 Wells lbo2 and lb3 close together you can see there's the burm across um the Gully and there's two Wells that uh and it's a very very steep Gully and there's two Wells sort of midslope Down The Galley bit sort of somewhat between cross gradient up gradient um you can't I can't see it on my screen you might be able to see it on yours but beneath sg5 in region there is horse yards so you you've got a source of manure sitting upgrade of K mb1 and K mb5 it's on um a potential Elite or Elite smectite um Sil Stone next slide so this is quite interesting when you plot it out um lb3 which is the square boxes um is much more clay um 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 uh going down to a lower level I me um and it's also in quite heavy clay with with less pesses lbo2 the the cross is in quite pressible environment and less clay which you'll get in in landfills that sometimes there's a lot more soil that comes in particularly in country landfills and mixed matter than there is in Municipal matter the municipal matter might only arrive two or three days a week um for the garbage trucks and there might be a constant stream of uh of soil and and um commercial rubbish the interesting thing is that during the dry years the ratio is lower than during the wet years and the reason is that during the dry years the base of the landfill is the base of the galy and it's the one that's wetest 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 um less clay and more pressible manner matter would be um higher in the AL to n ratio note that because they're fairly close in the similar system their approximate position in Redux the p plus pH is much the same but the background water is highly varable in Redux and on this scale is it's not possible to pick a variation on the L to n ratio so there's something going on with the background water in terms of its redo Behavior next slide please so I just want to talk now a bit about vas there's some fantastic work done by Nick Simmons when he was with the vi PA in Victoria so that's Victorian data only and then there's work done by gallon across all of Australia on pasas in landfill lead shape I've ordered them in ratio according to Nicks works so as you can see p hexa um is the dominant species in in landfills as a mean across um Victoria and and also across Australia so they got quite good data matching really um the PFA for those of you who don't know has been recently declared a category 1 carcinogen um at the international level um wh so um how long that um becomes before the criteria drops in Australia to reflect that will be interesting uh it's the second most dominant um then you've got P fos which is the one people are most concerned about is is the fifth most dominant in um Australian data and in the Victorian data so let's look at lbo2 and lb3 so we've already heard that lb3 is in a heavy clay environment with some interaction from interface drainage above lbo2 is a much more pressible environment so lbo2 is not dis similar it's got a bit more posos same concentration really it's got a lot lot letter of P for hexa but the the rest is comparably the same um ratio in this instance posos is the third most common of of the PES that occur most commonly in landfills lb3 posos 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 have a bit of a look at it um so that gives you some idea that um you know that level of posos is above criteria um the level of P for hexa and posos together in the means would be above criteria for discharge into a Waterway and exactly what's going to happen with P criteria it'll be interesting to see but at this point they're okay with criteria um except drinking water criteria of course uh next slide please so just looking again um at where lbo2 and lb3 is but then again look at K mb5 so it's sitting um down on slightly cross gradients if all the you the hydraulic control here is you can see is controlled by the Gully so the water will discharge basically into the galy and then along the base of the C and out of the landfill into the to the stream the stream sits at a RL close to 330 so you can see over a very short distance you've got um almost a 30 meter to um 40 meter difference in elevation over a short distance so it is very steep there next slide CLS now this is from ble 5 M mb5 on site and I haven't retitled my apologies I knock this in a few minutes ago um because it's really in itself very interesting data um so what you've got is that this particular data because of the saline background and the Lan lee8 being less saline um you're seeing responses to landfill leachate and background imposing here um so we have a very very low sum sum of all P fast to start with those units are milligrams so we're dealing with 0.003 um micrograms of sum to P in August 17 um the the data consistency is not so good on P it's only just more recently started to being measured quite consistently the Elder end ratio is 1.44 in September 20 there's a series of data with Eldin ratio 1.4 for some reason pfast wasn't done then so it was done the following round in April 2020 that's after the heavy rains had started so it would be nice to have actually had the back end of um soorry April 2020 was the heavy rains and September so was before the heavy rains it was the drought by September the drought had broken so it' be nice to have had what the impact of the altern ratio was by the water pushing through the system and the breakage of the drought so the data we have for p is not consistent then with the Eldin ratio and the other data so it's this stage showing that it's it's 089 is a total sum of past and starting to come up in November 21 the Lin ratio is 1.6 and the sum to pasas Isle o so it's 0.59 of a part per billion so it's actually come up the really intriguing thing is as though nitrate has bounced a bit the Yello in ratio has come up some other things have gone down but pottassium hasn't greatly moved this is because it is this problem we talked about is the system is sorbing um potassium from the landfill I don't have other data actually see what's going on here it's just an indicator but it's got some strong conclusions forming that at the very start of the El to end the very start of breakthrough you will see p so let's that's sort of the Run of my talk let's just go to the conclusions oh so this Factor um so all the things I just talked about this site probably has an ili or stratified mineral Al light smectite Elite preferen abbs both potassium and ammonium um we can only conclude that that that if the Elder en ratio becomes elevated then fast will also be elevated and at this point in time we need a lot more data and the past data for elderen is would nice to see from a standard site rather than a site that that has huge capacity to sorb um 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 leade breakthrough um you use the Eldin ratio to go is breakthrough happening and then you look at the greater data so it has to be inter 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 eln ratio gives you a good idea what's going on what's Happening how it's happening um and the age of landfills and and landfill leap can be expressed beautifully on the Elder end ratio with the plotted against PE plus pH there's no need to analyze other contaminant beyond the anionic balance that you do um and if you want a few other indicators you know Iron and manganese and so on until the l2n ratio defines a breakthrough front so all the monitoring associated with pesticides and PHS and tphs is unnecessary with the one exception um and that's P provisionally if the alter end goes up from the landfill you should be immediately analyzing P um because it's likely you've got a a summed past breakthrough front occurring and haven't seen what the time is Richard but um you're a little over fil well you keep interrupting Richard I mean really I'd be on time if it wasn't for you it's very true Phil um 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 birth questions and then we've got a few in the Q&A as well so uh question number one have you considered that continuous monitoring of parameters such as pH EC and temperature Etc and their Trends may be a more timely and costeffective way of identifying breakthrough of Lee well as you heard me just discuss is that um EC is next to useless um for monitoring transfer breakthrough pH has some value but but it when you're in a more permal system it bounces all over the place um temperature in the acfa less so temperature in terms of bleach a yeah I mean it's got some benefit pH and eh together are very useful um and Richard you'll be able to tell me if there if there is stable eh probes out there at the moment um I'm not certain there is but there might be and in which case logging pH and eh is is useful but not as useful at this point of doing ionic balance analysis um gross breakthrough in a low water aquafer in a sealed system um EC would be useful yes so once again it comes back to knowing your site conceptual model and knowing what is or 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 when the Breakthrough might have first happened um as opposed to just having that that annual or quarterly monitoring thanks for that question number two Consultants often refer to an L when value of greater than 10 as being indicative of leead impacts I can't find a source for that yeah well nor can I because I haven't actually said that nor has we ever published that um the ratio is a relative ratio certainly over 10 it's very rare to have a groundwater that would show and some of the bi biotic micers with heavy fertilizer application on panics might come up with an L to n ratio greater than 10 um so it's you know it's a fairly forone conclusion that if you're over 10 you got you've got a strong likely impact of pressible breakdown you can't justly say it's leate but you can actually read a breakthrough at at one to two or one to even 1.4 starting to occur and because we're looking at vast itself and P is literally um close to a million times more sensitive in in um detection limit than the L to n ratio um then you really need to start considering not just what the ultimate breakthrough is but but what's happening early in the ENT itself okay I think you might have answered this one in the talk but can the l2n ratios be used to assess the potential lead shate impacts in surface waters as well as ground water in yeah to a limited aspect yes it can um as long as you're interpreting the full you know data set so you'd use the eldrin ratio in surface water as as a clue for a massive a more massive event so if you see it moving in terms of that l rmic um 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 um upgradient has thrown a lot of fer um fertilizer into you know potassium nitrate into into the river um it could be due to um a whole variety of other reasons that you need to look keep an eye on so in this instance it does doesn't um uh 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 you know how Dynamic of 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 bank any presence of maites and bull rushes 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 he number four if we had a robust liner for the landfill would we could minimize lead chap would that be easy all this is the philosophical discussion that um we could waste a lot of time on um all landfills should have a robust liner um whether the liner is um a clay based liner or a composite or whether it's um uh hdp liner is a question of different philosophy of approaches by the different epas um I'm actually a strong believer in allowing the system to interact with environment around it but allow it to interact at at a rate slow enough the environment can adjust to address it like we just talked about previously having plants soak up the nutrient um or having exchange occur so that the the plume moves very slowly and is attenuated um Aigner the problem with liners is people think that it would be um retained within the land fill it's estimated in the installation of landfill that the minimum number of punches you get is two per hectare um and two per hectare into a sand based system can have a huge leakage rate um so the problem with thinking that you have a robust liner is you stop monitoring and you think that your landfill is sealed forever um unfortunately that's not the case what happens to lers over 50 60 100 years we don't know in terms of hdp liners uh 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 um and 2000s that that have plastic covers and gas extraction um 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 Is Not a Bad Thing providing you've got the right environment to do it some epas will not accept that so Phil you said you're in favor of some interaction between I guess the Le shade and the environment yes terms of irrigation of leap and reuse of it for that purpose what's your view on that ignoring the P problem for the moment um 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 Shand it with a bit of town water to drop the ammonium below 150 PPM and you'd spray it out onto your golf course to reduce the use of the fertilizers um and that was a perfectly adequate use once your ammonium gets up past 150 and certainly 300 but um you end up with with burning and scolding of sensitive plants particularly some certain grasses such as cooch um so in that instance you know you just got to control the level of salinity and the level of ammonium in the water um so yeah horses for courses um but it is what it mostly produces is a salty fertilizer okay how to minimize P impact on landfill feed stock and surroundings how to measure greenhouse gas emissions from decomposing waste it'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 a very good income out of doing that and so they're better people to talk about that so I'll leave that second component alone the first component um is that yes we do have to consider carefully of getting PS out of our um entire supply chain um so the phasing out oh Scotch guards disappeared I don't think anyone will recall seeing Scotch Guard at the moment um gortex no I think is no longer using p um in their products um the use of Teflon I think is reducing they'll still come into landfills but they don't normally have some of the the worst prast compounds in them the main problem is firefighting foam and there's two sources of those there's um or three all up there is the um firefighting foam cylinders so um they're probably best not to get those into landfill so quite a few of those you know um com in from domestic and Industrial Waste the small one kilo ones up to the B6 kilo ones um they come into landfill and they contain the foam um the concrete from firefighting areas and other areas will have foam impr pregnant on it they'll wash out of it and the land fil um as conditions change so receiving that feed stock into a domestic refu situation may or may not be a good thing um bio solids because of the fire the use of firefighting practice Pham throughout the catchment um wash often to the the series treatment works and the input of B solids to certain landfills probably should not be considered so stopping B solids coming in until the B solids are deemed as being posos posos and or P high and P hex uh clear would probably be most appropriate um so yeah that's several ways of addressing it Richard okay I would have thought you better off to put it in the landfill rather than have it sitting around in the environment but um I think it needs to go to special landfill so it's a matter of dis that's a matter of discussion with the landfill licensing authorities is you know is a particular landfill appropriate for that to go to um you're quite right is that maybe there's enough biosolids that have pasas in it then it might be more appropriate to put it into a monocell um or an hdp leech collection Lin system rather than an unline system has PS been added to the bar solids reuse guidelines G not yet interesting okay um there's a good one has the reduction in food and green waste going into our landfills altered the leachate chemistry compared to 1990s refu um there not enough redu I mean the reduction in food and green waste going in um is yet to fully come through um the Fogo recycling is just gearing up to the great extent now um you still got vast amounts of pressible matter coming in with construction Lumber with you know great stumps and and garden waste um 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 um if we reduce the amount going in and we don't inum them um then we can come over and reuse it again more rapidly so we certainly harvest the methane from it and um the methane Harvesters the guys who run a business in putting it into P into Power stations um actually don't like hdp liners they much prefer CS I don't like hdp caps they much prefer clay caps um it's much it's much easier for them to handle a clay cap system and more efficiently get the methane out than the HDPE systems um so it' be quite interesed to see where this what happens over the next well I won't be around to see what happens over the next 40 years um with what our landfills do but um some in the audience might and I I hope it'll be interesting hopefully they keep using the old wi ratio fil um next one reinjection of condensate into landfill cell versus treatment alongside leea L you just heard me talk about that a while ago it's quite common to um more so overseas and Australia to to re-inject into the face for dust control and and so on um 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 um which is good for the methane operators are coming in over the top um now what other treatments you might do uh 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 minute um and then many land where the closure conditions have allowed that not a lot um 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 um so yeah not a lot but you do have to manage TDS and you have to manage ammonium as a 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 um could be substantively expensive for the community where natural treatments might be more beneficial I mean Wetland treatment as well is to run longitudinal Wetlands um around the base of the landfill if landfill cell or um or off cell elsewhere um before discharging through um offsite and having a whole series of um of mccrites to actually polish it so the the increasing interest in um in in phyto closure and phyto caps and phyto treatment of leate 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 um I was actually quite surprised I he found out about a year and a half ago or two years ago that that a lot of people use it and and it's called the mby ratio so I knew you know our company uses it and a lot of our ex staff use it but I was surprised it's had widespread use um and the EPA seem quite comfortable with with it and its understanding I did present Landfield Lee chemistry talk to the vipa a few years ago that talk I think four hours so i b i b them bored them silly I think um but I uh I really don't know um so I I can't comment but but it is it appears it's now accepted practice for for groundwater monitoring are there any situations where particular landf for sites where the l2n ratio should not be used um no um okay in low solidity um it's useful very useful um but the the TDS variances and EC variances aren't as useful as people think in high solinity it's almost essential so we got High solinity background and you want to you want to pick small movements of ammonium nitrate pottassium to see when the Breakthrough is first first occurring um it's very hard to see it in in a High background and a High background the ratioing off the complex ratio like this shows it up um question 10 current and possible roles of radioactive traces that already exists in landf Le yeah this is tridium and cesium um that you're mostly dealing with we shouldn't have any other radioactive traces in there because they're not supposed to be um um low and mid-level radioactive wte and 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 and increase in the tridium the radioactive water um to occur above backgrounds um so any landfill leachate migration into groundwater that's older than n the mid1 1950s you would be able to see cesium um 127 elevation occur it's it's more expensive to do than um the uh ionic balance of which the l n ratio is based on um and it would have limitations into quite a few landfills where you're dealing with um unconfined aquaus where the water is you know of the last 50 or last 70 years so it certainly has a has it's 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 the exploding of the bombs that led to that sorry atmospheric testing of of atomic bombs yeah number 11 can biochar make Le that does escape less dangerous yes um we use biochar in bioreactors at different at different points in time what it can do is hold the nutrients long enough for the the macrofit so we tend to run a bi permo reactive barrier um with a um mccrites on top or slightly down gradient of it um if the ammonium levels are too high um and we need to just hold it back and give the plants a bit of a go you've got to choose your Char appropriately um ammonium some some chars are not so good at absorbing ammonium quite a few are um so yeah it's um certainly a potential solution now we've got um we've just clicked past two o'l uh we've got nine more questions to go are you happy to stick around Phil look um maybe just take the highlights Richard there's quite participants still there um so I really shouldn't go past about quarter past two okay do you have any guidance on how new practices in pre-trading 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 in different ways to the past with adverse effects EG H2S production yeah look um surprise yeah if you take the iron out you can increase the H2S somebody knows they G chemistry here um 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 inum cover so the H2S would rise into the day cover or the inum cover and it would then um reduce the girthy that causes the the red minerals of the soil colors so the Reds orange yellows are all due to oxidized ion minerals so a reaction would occur between the H2S and the oxidized ion minerals in most instances um H2S is not a problem um in landfill gas as that 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 there soil C disposed with it um it's unlikely to be a problem as such um the landfill of the gas meters themselves that we go and typically the five in one meters do have H2S on it um and you good operators should be just keeping an eye on the h2f as well but I've never known H2S to occur from the existing landfills for the very aspect that the the question uh indicator was it this there's lots of iron in the landfills all right um next question is thanks Phil you mentioned looking at fluide as an indicator of influence from town water from your experience what is the range in concentration in town water typically it's it's 08 to 1.5 um to be effective on um against um gum disease and um all those other problems that I got throwing up mudgy without fluide in it um so yeah typically it's 08 to 1.2 it can be a little bit bit lower but don't forget it's being mixed with what you're putting in so it might Express as somewhere from 6 to one but normally you know fluide in most aquias is below 04 okay now Bobby Wang's got a question can the L to n ratio be applied to contaminant plumes from other sources egl napple and dissolved phase plumes associated with petroleum sites or nutrient plumes associated with wastewater treatment plans it'll definitely pick up Nutri plumes pressible um material put elsewhere such as mulch and compost um the chemistry approach is the same except the fact that um petroleum plumes don't produce excess potassium um and so typically in those environments just having the site conceptual model and understand that you know sulfate will fall away and nitrate will convert to ammonium as as the oxygen consumption occurs so the peculiarity of um degradation of pet pressible material is they produce the combined combination of high pottassium and high nitrogenous um species um so it it makes a very peculiar uh leate Plum that is is not the same as as um hydrocarbon plums um even though it'll produce some of the same Redux reactions um but it is the same for uh other organic wastes such as mules and compost the manures will tend to have more phosphate in them so you'll see a slightly higher phosphate associ of manures and night soil but night soil dumps just about all passed through the plume stage at this point in time okay James Stewart from always carbon bit of a plug there James a great session thank you Phil and hydr Tera curious if you could comment on what is best practice for treating lead shap escapes when it occurs egfp fast is detected what is the best practice to do about it um this is an involving science it's an excellent question we don't yet I mean the EPA across Australia and particularly Victoria to their credit have funded um a lot of Investigation of um p and Lee to try and understand it um the current understanding is except in C circumstances the risk to the sewage systems is low because I looking at putting leachate into sewer um individually you then got to access um consider what is the um risk to um other receptors apart from pumping it the sewer so that could be um via groundwater to surface water or via groundwater to Springs or via groundwater to to swamps um 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 are using plants um to uptake the leee um and you're using um I suppose primary treatment would be the the the mccrites before you move into secondary treatment and polishing so if you're going to the mccrites in in the first Bay and using that as your treatment strategy um the pasas 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 past substances would Harvest um the plant and send it off to um a number of of thermal desorption disorb 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 Hong Vu great talk thanks have you tried to compare or complement the Elder n ratio with isotope data I think you might have answered that I haven't directly answered it but um yes I mean that's a good research area the problem I have is that I'm a practitioner and uh um I'm I'm fascinated by research components but I can only do the research components off client derived data um and the clients are only going to spend what's necessary to spend Tera cling H can the eldwin ratio be used to demonstrate the end of an after Care 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 the temporal based logarithmic scale to show a downward trend um so yes it definitely can um I haven't heard it used on that basis um because modern closures of the mega landfills are yet to I mean they've occurred I mean you've you've got to Marine being a classic Mega landfill um but they're not at the the point where they're 30 to 40 years past their billing stage to the point where you can see that the the Le shade is is decaying to a satisfactory safety point so um I I'm not aware of any of the 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 fluide is not added such as some lgas in Queensland are well you can on the basis that um 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 catons to look at what is the mixing of if they're putting quite a bit of water on you'll see a signature come through that's different the Elder n ratio might be a little bit similar a little bit lower but the other say that the um florid to sulfate and calcium to magnesium ratio will be very very different here's a good one for you Phil from Donna Windle we love the L to end mvy ratio there you go um thanks Donna 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 eg tasol a ATL tritium as a tracer of leeche contamination in groundwater I don't disagree and I apologize for not mentioning that um I still default back to cost um you can do an ionic balance it varies from Lab to lab but anywhere from $35 to $50 to get a tridium analysis done is quite expensive well Phil we're through the questions thanks very much and thanks very much for everyone who's stayed on still got many people here um 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 I need potenti to write into the paper to communicate to fellow professionals um about further ways of utilizing and interpreting and extending and improving the interpretation of the ratio um and also um just you know if people got past 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 um that I didn't go into but that makes it very very hard to kind of work out what's happening um so yeah I really appreciated this Richard because it's um I I was up until a couple of years ago not aware of how much industry uses it so to to improve the ratio is 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 Fant fantastic and Mark Pon says thanks for a very interesting presentation so plenty of support there Phil so thanks very much and we'll thanks to the industry all right thanks Richard thanks all the viewers cies bye bye