 Well, welcome everyone to another one of Hydra Terror's webinar series. It's great to have so many people here today. It's fantastic. Today, our topic is around landfill leachate collection, treatment and monitoring. I'll just run through a bit of an outline of that. So, our guest speaker today is Tyson Klingon, and he's technical director and principal from Mackenzie Environmental. Tyson's a true landfill specialist, and he's also a chartered environmental and civil engineer. He's got approximately 14 years experience working on landfills, and we're really lucky to have him here today to tell us about all his learnings dealing with the design of landfills and the leachate management side of things. We've got to know Tyson over the years working with him as a subcontractor on various projects, and he's a great person to work with. So thanks very much for joining us today, Tyson. Really appreciate it. The second part of the presentation will be from myself talking about leachate monitoring, which is something that Hydrotera has done a lot of work in as well. So, a pretty full day of information coming your way today. Before we charge into things, we love your questions, and just a note, thank you so much for all those early bird questions. We've had 10 questions already, so we'll try and leave enough time in Q&A to address those. Some of those questions will be addressed as part of the presentation itself, and others will be addressed at the end. But please log your questions as you go, and we'll do our best to answer those. Any questions we can't get to during the session, we'll get back in touch with you by email to confuse some answers on those. So to raise a question, use the Q&A button and type your questions in there. And at the end, I'll read them out, and both I will do our best to answer them. Why does Hydrotera run these webinars series? Well, we like to share knowledge, and they seem to be getting more and more popular, so we're really enjoying running them. We also seem to have a lot of people passionate about sharing their knowledge, which is fantastic in our industry, so really enjoying being involved in this process. We're also trying to facilitate education. It's an area where there's probably a lack of good applied training in some aspects of the sort of real world, and all the people in consulting know how difficult it is to get time to pass on their knowledge, so I think we're helping to facilitate passing on some of this knowledge. And finally, we like to see ourselves as a bit of an industry leader in helping with linking up technologies and people's knowledge. So they're the real drivers behind why we're here today. All right, so the topic of the day. So Tyson's going to talk to us about leachate collection at modern best practice landfills, leachate collection at historical closed landfills, leachate treatment and disposal, including evaporation, ratification, disposal to sewer, and most importantly is going to give us some case studies of how this knowledge has been applied. I'm going to talk to you about leachate monitoring technologies, best practice application, and monitoring case studies of landfills as well. Finally, we'll do our Q&A session. So without further ado, I'd like to pass over to you, Tyson. Thanks, Richard. And thanks for joining us today. So as Richard said, I'll be talking about land called leachate collection and treatment. And the collection side of things, I've broken that down into more modern best practice landlandfills, where you have a leachate collection system. And then also looking at older landfills, online landfills, where you don't have a proper leachate collection system and there's the need to retrofit and install valves, that type of thing. Now we're looking at leachate treatment. A few common treatment methods that I've been involved in. And finally, a few case studies. So firstly, I thought I'd talk a little bit about why do we extract and treat leachate? Well, obviously it's to protect the environment, mainly the groundwater and service water environment. And I've got a few dot points up there on, I guess, more the technical side of it, how it's achieved. So in a line landfill, the reason we need to extract leachate is to minimise the head on the liner. So even the best liners leak, there's no such thing as an impermeable liner. So you need to minimise that depth of leachate above the liner to reduce that leachate seepage rate through the liner. We're looking at online landfills above groundwater. Similarly, it's about reducing the leachate head to again minimise any seepage through the base of the landfill to groundwater. And the third point I've got there is online landfills below groundwater. Obviously you can never completely load leachate there, but the idea is we're creating inward hydraulic gradient to minimise the flow of contaminants offsite. There's a few other reasons, obviously, why we extract leachate as well. For example, to manage landfill gas, because we can't extract landfill gas if the landfill is flooded with leachate. Next slide. Thanks, Richard. Okay. Leachate collection of online landfills. So this aspect of leachate collection is, I guess, very mature in the industry. Very well understood. We've got a lot of regulation around this. And most in the industry are pretty familiar with what's required. So I've got a little cross-section up there on my slide from the Victorian landfill best practice guidelines, otherwise known as the Beppen. I won't go into the lining system there, but above the lining system, we have the leachate collection system, which typically comprises a 300 mil thick layer of leachate drainage aggregate. So that's a free draining aggregate with minimal fines. Network of leachate collection pipes, typically polyethylene pipes that are drilled or slotted to collect the leachate. And that's covered by a separation geotextile. So those are the three main components in the leachate collection system to collect the leachate and take it off through a leachate sump. The other aspect of leachate collection system design is the gradients of the liner. Sorry to say on the previous slide there, Richard. So typically the minimum grades are 3% grade to the leachate collection pipes and then the pipes grading at minimum 1% to the sump. So there are the minimum specified in the Beppen and it's pretty similar in most states across the country. Anything flatter than that and you risk the leachate head building up because the flow to the sump will be slight. So once the leachate enters the leachate collection system, the liner grades to a low point where there is a leachate collection sump. So I've got a little cross section of design on this slide and a photo of one in construction there. So the leachate sump, sorry about the dog barking in the background there. The leachate sump is typically about a metre deep, low point of the liner with a large diameter riser pipe extending up the side liner of the landfill. There's a leachate pump installed down that riser pipe to extract leachate. There's a couple of different arrangements you can have with leachate sumps. The one we're looking at there is inclined or installed on the side liner. And the alternative to that is a vertical riser pipe which extends just straight up through the waste. So there's pros and cons to each of these types of riser pipes Personally, my preference is inclined riser pipe that we're looking at there in this slide up the side liner. The advantages of those are it's installed all in one piece through construction. So there's no need to extend that throughout the life of the landfill. It's out of the way of the landfilling operations so you don't have a planche and equipment running into it. Trucks running over it, that sort of thing. And the pump gets installed once and it can remain there for the life of the landfill apart from obviously making it inside of things. It's installed once and it's there. Also all the pipe work for the pumps so that's compressed air to power the pump, leachate conveyance pipes. That's all installed at the top of the riser pipe and it's outside of your landfill area so it's less likely to be damaged and doesn't need to be moved during landfilling. So the alternative being the vertical riser pipe which sticks directly up through the waste. Sometimes they're unavoidable but they do have a few more issues in my point of view. So that is they can obviously be hit and knocked around by landfilling equipment during waste placements as the busy sites these landfills with many, many trucks, landfill compactors, heavy equipment working around them. There's a need to extend the riser pipe with every lift of waste. So you come back very regularly adding another couple of metres of pipe onto the riser pipe to extend it up as the waste is filled in the sail and then there's a need to install and remove the leachate pump and associated pipe work each time that riser is being raised. So it's a bit more fiddly during landfilling. Next slide, thanks Richard. So that's a summary of leachate collection at Best Practised Landfills. As I said, it's pretty standard across most sites as well as still well regulated minimum requirements there. Once we enter leachate extraction at online landfills and old closed landfills, things get a bit more interesting and a bit trickier for all sorts of different complications we need to overcome and there's no real set guidelines or methods for this. So the typical method of extracting leachate from an online landfill without a leachate collection system is installation of leachate extraction wells. So their wells typically drilled vertically into the waste until the leachate is intercepted. There are examples of horizontal wells but by far vertical wells are the most common. Often these wells are combined landfill gas and leachate extraction wells. So in that case, the casing of the wells are perforated and I guess the bottom part of the well that is below the leachate level is used to extract leachate and there's a pump installed down the well to extract that leachate and then the top half of the well or top part where there's no leachate is where the landfill gas can be extracted. So drill wells, they're very useful. So as I mentioned, these wells are fitted with pumps similar to the best practice landfill and these wells are typically pneumatic or air powered pumps. Next slide, thanks Richard. So leachate extraction online landfills lots of challenges as I said and there's no, it's different at every site and we've listed a few of the different challenges there that I've run into over the years. Small radius of influence due to low hydraulic conductivity waste is a common issue. So typically waste isn't very permeable and that depends on the type of waste and the type of cover material that was used during landfilling but typically the waste and the cover is compacted in to maximise the amount of waste you get into the landfill and daily cover is applied over the waste each day so there's a lot of soil and if that soil is low hydraulic conductivity it can be difficult to extract the leachate. So the small radius of influence means we need lots and lots of wells and lots of pumps and that means lots of pipe work all across the site high installation costs and lots of maintenance required. The other thing there with the low hydraulic conductivity of the waste means it can take many years to lower leachate levels. So once I'm involved in the minute they've been extracting leachate for more than five years and they're still working towards their target levels so it's not a short-term fix. Next slide, thanks Richard. So a few of the issues I've come across I'm trying to extract leachate from online landfills. The first one I've got there is waste settlement. So the depth of waste in landfills varies greatly but some recent landfills I've been working in where we've been extracting leachate from an online landfill I've got depths of waste up to around 50 metres and particularly where that waste has been recently placed you can get a lot of settlement in the first few years after that tends to slow down but settlement will continue for decades. So the settlement can cause wells the casing of wells to bend or kink because the casing of this is sort of fixed while the waste is settling down and the forces on that can cause bends. The issue we get there is pumps become stuck or the casing itself completely kinks and that well becomes redundant. Other issues I've come across is silting of wells. This is a particular issue I've come across at one site which was a former sand quarry and the fine sands that were left at the site were used for cover material on the waste and so that material migrates into the wells as leachates being extracted and can settle in the base of the well above the pump causing pumps to become stuck. Third dot point I've got there is waste settlement again this time damaged through the compressed air and leachate conveyance pipes that go to each pump. So these pipes are typically installed in the capping layers of the landfill and there's a compressed air pipe to each pump to power the pump and a leachate conveyance pipe from each pump to convey the leachate to wherever you're pumping it to typically a leachate pond. So where you get a lot of waste settlement the cap settles as well and if there's differential settlement that can cause damage to those pipes and breaks or kinking in those pipes. Fourth issue I've got there is then silting again but this time again a leachate conveyance pipes. So the pumps that we use for extracting leachate many of these pumps tend to handle the silt very well but they do pump the silt along with the leachate. So there's a need to have infrastructure on those pipelines to collect the silt so it doesn't block the pipes. And the last one I've noted there is when you have lots of penetrations through lots of wells there's lots of penetrations through the landfill cap and every penetration through your cap is another potential point for landfill gas emissions that needs to be managed. That's Richard. Next one I've got here is a case study of an unlined landfill, leachate extraction. So this is the Clayton Regional Landfill in the south-eastern suburbs of Melbourne. This area of Melbourne was a sand mining area and most of those sandmines subsequently became landfills. So there's at least 10 or more old landfills in this area. This site is a former sand quarry. It extends to more than 20 metres below the natural groundwater level. Most of the northern half of this site was unlined. They lined it with what they called a slimes liner. Slimes being the silty, fine clay material that's left over from the sand washing operations when these sites were sand quarries. So that slimes material is placed down on the base and sides of this landfill in the older sails to form a quasi liner that effectively it's unlined in connection with groundwater. The southern part of this site had landfill sails, two sails lined to best practice standards. However, those sails, the leachate collection systems failed and the sails essentially were allowed to fill with leachate due to failure of the leachate collection system and a bit of poor management. So when we got involved in this site, essentially both the north and the southern parts of the site had similar leachate levels. The levels are similar to surrounding groundwater. So this site, when we got involved, had some leachate extraction but it was clear it needed some more. So the first step was a hydrogeological assessment which included some leachate pumping trials. The objectives of the assessment were to assess the hydraulic conductivity of the waste, assess the radius of influence of leachate extraction wells and that information was used to undertake some modelling to look at how many wells would be needed to draw down leachate in this landfill and how long that might take. The outcome of that was some upgrades to the leachate extraction system included drilling of additional wells, installation of additional leachate pumps and upgrading a lot of the other infrastructure across the site which include replacing compressed air pipe networks, leachate conveyance pipes and replacing air compressor infrastructure. So this site now is working towards achieving target leachate levels. They're being achieved across about half of the site but we found that it's very variable due to varying hydrocomactivity of the waste and the interconnectedness varying across the landfill. So we found in some areas the leachate levels responded quite quickly to pumping. In other areas it's taking a lot longer and it may take several years for the target leachate levels to be achieved. Some of the other things to note in a site like this with 77 leachate extraction pumps, that's a lot of pumps to maintain and operate. On this site we monitor the pumps on a weekly basis and that's to check that the pumps are operating as they should be, check there's no issues, no leachate leaks, compressed air leaks or landfill gas leaks at the wells. And then this is a site where we've had a lot of issues with smoothing of the wells and leachate pumps becoming stuck. So to try and overcome that the pumps are raised a couple of minutes in the well and we do that every three months. So it's just lifting the pump up to try and dislodge any silt before the pump becomes stuck and irretrievable. So next we'll move on to talking about leachate treatment. So once we've extracted the leachate from landfill it needs to go somewhere. The three common methods of leachate treatment disposal that I'll cover are evaporation, leachate treatment plants that's on-site treatment plants at landfills and disposal to sewer. So evaporation is common at small landfills where there's not large volumes of leachate generated. Once you get to larger landfills and or wetter climates that's when on-site leachate treatment plants are typically needed and they're typically in conjunction with disposing to sewer. So there'll be some treatment only needed before the leachate can be pumped off to sewer. So firstly evaporation, as I mentioned most common form of treatment at smaller landfills on Victorian-based and pretty well every rural landfill in Victoria would have a leachate pond where leachate is evaporated and I'm sure it's similar across much of the country. Obviously it only works in dry climates. So I've got a couple of maps on the slide here from the Bureau of Meteorology one of average rainfall and another of average evaporation. So in any climates where you don't have a significantly higher evaporation than rainfall clearly evaporation from a pond just isn't going to work. Brings me on to the third point there that can require very large ponds. So if you're only getting a few hundred millimetres of evaporation in addition to the rainfall a year then large ponds are needed and there comes a point where larger and larger ponds are just not feasible. Other options are enhanced evaporation that's one that I don't have a lot of experience with and don't run into it a lot. I have seen it used here and there at some sites but as far as I've seen it hasn't taken off. Enhanced evaporation include various things different types of sprayers to try and increase evaporation as other methods of heating or burning off the leachate. As I said I haven't come across too many of those. Another common form of evaporation at some of these sites is dust suppression in the active landfill cell. So at some landfills they'll fill up leachate in a water cart and spray that around your active landfill cell in the dry months and that's one way of really enhancing the amount of evaporation that you can get. And then the last thing I'll touch on with evaporation is lack of capacity during wet periods. So as I mentioned most of the sites I'm involved in all have leachate evaporation ponds which were working great during dry periods. Over my career when I started we were in drought for several years everything was going along quite fine and then in 2010-11 to rain in Victoria and suddenly everyone had a leachate problem. Since that time there's been a lot of upgrades most sites to increase leachate storage and treatment capacity. And then the last thing I'll touch on there is once you run out of capacity a site often the only contingency is trucking off site and that's something that you want to avoid at all costs because it is extremely expensive. Next one I'll talk about is onsite leachate treatment plants. So leachate treatment plants are common at larger landfills so larger municipal landfills and particularly in wetter climates. So leachate treatment plants are typically used to treat ammonia via nitrification and also reduce the BOD load prior to discharge of sewer. Obviously there's a range of different contaminants and chemicals in leachate. However the ammonia and BOD are the key chemicals that were treating prior to being disposed. So I've listed there some of the key requirements for nitrification at one of these treatment plants. So the first thing we need is the nitrifying bacteria. So there are the bacteria that convert ammonia into nitrite and nitrate. These bacteria are naturally occurring everywhere. However typically the landfill leachate treatment plant the plant will be seeded with bacteria from a municipal wastewater treatment plant in the form of a sludge to seed the plant to get the nitrification process kickstarted more rapidly. The second thing we need is a source of dissolved oxygen for those bacteria. Now that's typically supplied using aerators. The most common I've come across are mechanical floating aerators and they provide a source of oxygen. Thirdly there is temperature. So being a biological process it's temperature dependent. The temperatures quoted for nitrification the optimum temperatures are out somewhere around 30 degrees. In my part of the world the water temperature is a lot lower than that most of the year. In summer water temperatures are in the 20s which is fine for nitrification. Winter once you start to get down below 10 degrees nitrification slows down significantly. So we find during winter months we have more storage capacity due to the decreasing treatment rate. And the fourth thing I've got there is alkalinity. The bacteria consume alkalinity in the treatment process so there needs to be a source of alkalinity for nitrification to occur. Luckily landfill leachate is typically high in alkalinity. So at some sites there's sufficient alkalinity to not require any dosing chemicals. The straight chemical equations would say you need seven parts alkalinity to treat one part ammonia. So if you've got landfill leachate with 1,000 milligrams per litre ammonia and 7,000 milligrams per litre alkalinity it should be fine. If it's less than seven parts there may be a need to dose some alkalinity. That's typically dosed in the form of sodium hydroxide or magnesium hydroxide which is the same type of chemicals that are used at municipal wasteful treatment plants. So that's a bit of a summary of the nitrification process itself that we typically undertake before leachates dispose of sewer. So the second step, disposing of sewer, that's done under a trade waste agreement with the local water authority. The water authorities will have a range of acceptance criteria. It's a very long list of criteria but the key for landfills are typically ammonia, inhibition, TDS load, and then potentially some other chemicals like PFAS. So firstly, pH, easy to manage. Typically there'll be criteria of something like 6 to 10 or pH 8 to 10. That's easy to manage before discharging by dosing with either an acid or adding alkalinity leachate within that range. Treatment of the ammonia, we've just gone through that in a bit more detail so I'll just skip over that. Inhibition is the next one that needs to be considered that we run into as being sometimes an issue on some sides. Now inhibition is a measure of the impact that the landfill leachate has on the wastewater treatment plant. So the municipal wastewater treatment plant that is receiving the leachate. So the laboratory actually takes a sample of water or sludge from that treatment plant and they run a test to see how much the leachate inhibits the treatment process. The tricky thing with inhibition, it's not chemical or property that's easily measured in the leachate. So if you do get high inhibition, it can be tricky to understand what's actually causing that. The next one is TDS load. Again, it's one that's typically not treated at the level of the zombie involved in. I'm sure there are some out there that might have, say, a reverse osmosis or something like that. But generally this is managed by a limit on the TDS load that can be discharged per day. So the wastewater authority will stipulate in the trade waste agreement. You can discharge no more than X kilograms or tons of TDS per day. And then the discharge rate is limited to achieve that. And then there's other chemicals that can be an issue such as PFAS. So here in Victoria at least, the waste for authorities are including PFAS limits in the trade waste agreements. So we need to monitor and ensure we're under those limits. It hasn't been too much of an issue at the sites I've been involved in. So I'm not aware of any sites yet that have specific PFAS treatment plants. The other thing I mentioned there is the discharge process. So there's two common types of process, a continuous discharge or a batch discharge. So some sites the water authority will be approved for a continuous discharge which is, as the name implies, essentially turn your pump on and discharge whatever you like, assuming the leak charge is within the discharge criteria. The second option, the batch discharge, is the one we come across the most. And with that method, the water authority requires every treated batch of leak shape to be tested in the laboratory and approved by the authority before it's discharged. Typically that requires locking of the pond. So all valves in and out of the pond will be locked and they can't be unlocked and the pump turned on until the water authority is given approval. And then there's a sampling and approval process to allow that batch discharge to occur. So typically that involves sampling of the treated leak shape under the supervision of a representative from the water authority and then assessment of the results, sending them off to the water authority for approval. So that's the summary of the process of disposing to sewer. I'll move on now to a case study of a site I've only evolved in. So this is the Clayton Regional Anvil again. So in the southeast suburbs of Melbourne. So this is a site with of those 77 leachate extraction pumps. And the picture I've got there on the slide is one of the ponds where all that leachate is pumped to. So this treatment plant is a pretty root of entry treatment plant, but it works. When the site started off as a sand quarry, they were quarrying deeper than the groundwater level. They had some ponds with our extracting groundwater too. Over the years as it became a landfill, they lined the ponds and slowly it was upgrading, upgraded until it became its current form where it's essentially a leachate treatment plant. So it was never an initial design as such. It's just evolved over the years. So this is a three pond treatment system. The untreated leachate that comes into the ponds has an ammonia concentration around 2,000 milligrams per litre. So it's at the upper end of the concentration that we see in untreated landfill leachate. The ammonia discharge criteria for this site is less than 200 milligrams per litre. So this site needs to treat it from 2,000 down to less than 200. At the moment this site is treating around 15 mega litres per year. So that's about 10 of those ponds that we're looking at there. So the method of treatment at this site is nitrification. So the process that I've just talked through, the way that is achieved is the ponds have been seeded with a biomass from a municipal waste water treatment plant. The ponds are fitted with aerators and they're mechanical floating aerators that you can see there in the photo. There's regular monitoring of the water properties. So things like pH and testing for ammonia concentrations, et cetera. So you monitor the process. That's all done manually at this site. None of that's automated. We do find at this site we need to add alkalinity to achieve the ammonia discharge criteria. And that's added in the form of magnesium hydroxide. And then the treat of leachate from this site is discharged to sewer and heads off to the southeast treatment plant in Melbourne. So the next slide is just an aerial photo of this treatment plant. So three ponds. At the southern end of the site, leachate comes into the pond, first pond on the right. And the treatment begins into the middle pond. And then the third pond on the left is the batch discharge pond. And that's the pond where we lock the pond, lock the inlets and outlets to the pond. Representative from southeast water comes along. We sample that pond. And then once that's approved, it gets discharged to sewer. Next case study is work landfill. I won't go into too much detail on this one. It's similar to the Clayton site. However, it's a more modern treatment plant being properly designed, proper controls, that type of thing. This is a four pond treatment system. It was constructed in 2017. Again, airways in each pond seeded with biomass from a municipal treatment plant. And discharged to sewer under a tray waste agreement with Yara Valley Water. Interesting, this site, as far as I'm aware, there's no dosing of alkalinity just due to the differing leachate chemistry. And thanks to Daniel Fyfe and Evan Karukopoulos from Hanson for letting me share this example. The next slide is just an aerial photo of this site again. We might just skip over that one, Richard. I'm trying to, Tyson. I don't have a slight problem. This slide was dark. So the last case study I'll just mention is at the leachate treatment plant of a Kim Brickie landfill in Sydney. This one is a sequencing batch reactor. So, type of treatment plant that you get more in wastewater treatment industry. Works on the same principles as the previous plant. So it's nitrification. But being a batch reactor, it can be controlled far more closely which means it can treat a greater volume of leachate. So this was constructed in 2018 and it treats an average of 335 kL per day. So that's a couple of megalitres a week or 100 megalitres a year. I understand this site, the untreated leachate ammonia concentration is a bit lower. It's around 300 mg per litre and they're treating it to Western 100 mg. However, I understand they generally get down to about 1 mg per litre. So that's just another example of a type of treatment plant that's out there. And thanks to Stuart Devere at Kim Brickie for sharing that one. That's it for me, Richard. It's awesome, that was fantastic. Thank you very much. Over to monitoring. So it's really two sorts of monitoring that go hand in hand and there's a bit of an overlap between them. So you've got your compliance monitoring side of things and that's really driven by the regulator and you've, in Victoria in particular, got an approved monitoring plan that's tied in with an audit process and that's got a frequency of monitoring and it's got the parameters laid down that you need to measure and it's certainly got plenty of clarity in what's required in it. The second side of things, the operational monitoring is, it's been more ad hoc, varies completely between sites and it's really tied in with Will Hatter's management. So they're going to manage their leachate and what information do they need for that. My perspective on the world is that both those types of monitoring really need to be brought together. You get a lot of good intelligence from the operational monitoring on potential causes of things that you see in your compliance monitoring. Probably with compliance monitoring is it sort of typically looked at at the end of the year and whereas your operational monitoring is sometimes collected daily, often weekly and so you've got a much better chance of managing your site and reducing environmental impacts with a good operational monitoring regime. So what do we actually measure? In the world of leachate there's a few different parts of the site and you've heard a lot from Tyson and seen a lot of them, some great case studies. Where Hydrotera gets involved is measuring how much leachate is moving around those various systems and where is it stored and is there too much in one area or another. So just looking at this landfill, for example, there's a leachate pond, Tyson showed us some good pictures of those. Things we need to measure there are things like the amount of freeboard which is the amount of space left in the dam before it over tops and there's a regulated amount of freeboard that one needs to manage to allow for problems where there might have been an accident and you need to have a bit of a buffer so you don't have leachate flowing down the side of a hill. Certainly they've been involved in sites where leachate has flowed down the side of hills so these things do happen and there's good reasons why these compliance criteria are in place. Monitoring leachate within the cell itself and the elevation of that is often a source of some woe for people. Why? Well, often it hasn't been thought about back in the old days and there's sometimes a bit hard to get the infrastructure down there to really monitor them and drilling through waste is a pretty challenging thing to do. You can get mattress springs and things curled around traditional augers so it becomes an expensive exercise to grill holes in the waste. So it's challenging. What you heard from Tyson was he likes incline sumps and we do work installing sensors in incline sumps. I've got a couple of pictures of some installs in those. You need to do a little bit of trigonometry when you're deploying pressure transducers to work out how to tie that elevation back to a common datum of 5m Australian height datum for example. Vertical sumps in a way are a bit easier for monitoring because you don't have to do the trigonometry but they tend to have all sorts of grief associated with the fact that they're not straight up and down. Like a lot of these have got concrete rises and that sort of thing Tyson mentioned as the waste consolidates you can get some pretty weird angles on what's sort of vertical sumps. Interesting challenges associated with that. Stormwater ponds is an important one and they're managed on site so you've got to keep really trying to keep stormwater away from leachate on these sites so if the stormwater ponds overflow you can create an even bigger headache for yourself so we like to monitor stormwater levels as well. So that's a few examples of how we monitor leachate on site. I just thought it would be worth touching on how many people are involved in sort of getting to a point of a monitoring system on a site. I've been doing quite a few monitoring system designs for landfills recently and the number of stakeholders who are sort of involved in that process is large, right? So I thought it would be worth just discussing that so these are all stakeholders. So you've got the site owner who's actually desperately trying to maintain their license to operate and that's very important to them and they typically engage people to help. So sometimes they'll engage another sector or another business to actually run the landfill for them and those two parties, the site operator and the site owner are very much joined at the hip. They need to keep this place running and they need to keep it compliant. So they need to bring in a bunch of people to help and you've heard from one today in Tyson, you know, these are these engineering consultants who actually design the systems, they design systems. Sometimes I wish they'd remember to design some access tubes for us to put our various monitoring equipment in but it's certainly they do a lot of good documentation and put that together. Then you have people like Hydra Terra who really design monitoring systems and we need to work closely with those engineering consultants to make sure that actually we need to deploy sensors that's going to be safe in the application like some things to think about that come up in some sites requiring intrinsic safety around pressure transducers that are being used for leachate it needs to be talked around between the various engineers to decide if that's actually required as an example. Then we have the auditors and their role is to sort of keep an eye on everyone and make sure that monitoring plans in the like of progressively reviewed sometimes it's an annual review sometimes it's a bit less than annual really that depends on the site and depends on the auditor but they play an important role in making sure we're collecting the right data and I would stress to the auditors out there that they should start thinking more about the operational data and how they can be tied into their monitoring plans better. Then we get down to really what's probably the one that determines whether or not the whole thing works and these are the planned operators on the site so these are the people who run the pumps and things and you heard from Tyson about you know a site with 70 pumps and that they're out there every week keeping an eye on them it takes a lot of time and effort to keep some of these sites working and it's often an area that's by site owners and operators so this is where I see most woe in landfills and we provide monitoring systems to keep an eye on whether or not those pumping systems etc are actually working and we can do that remotely. Then we have organisations like Hydrotera who actually operate the monitoring systems and this typically is around having continuous monitors to keep an eye on those various aspects of leachate and what's happening on those sites. More and more there's capability with the telemetry and data hosting to have that real time data and to have alarms associated with that. So the world is there's a lot more opportunity to get better at it for stakeholders who need to be consulted in that process of improvement. Finally we've got I guess what we call monitoring contractors everyone thinks they can do this they really do and consultants will send out juniors doing a lot of manual measurements and sampling that sort of thing and dip measurements and then you'll have the laboratories going out they've been contracted and they'll be doing similar things and you'll have people like Hydrotera going out and doing this. So it drives a need for a common system to bring that data together and that's something that Hydrotera spends a lot of time doing is just getting a framework together to bring together these disparate data sets to allow more efficient monitoring of these sites. I'm going to run a little bit short time so I'm just going to skip over some slides. So when you're looking at when you're looking to choose various measurement devices for your landfills there's a few things you need to keep in mind you've got to keep in mind what you really need to measure and its frequency. Sometimes people get obsessed with measuring stuff that actually never gets used and monitoring data just never gets applied. So try and work against that human instinct to get how are you actually going to use a parameter. Then we need to decide what level of functionality we need and if it's only once a week or once a month or once a year well you don't really need to stick an automated system in. So you need to make that decision or is it automated or do you just want a data logger when would you use telemetry. We use telemetry when you need an alarm. Use telemetry when it's a remote site. Use telemetry when you need rapid reporting. So there's a number of reasons why you choose one or the other. So just on the right there I've got some examples of how you can measure depth so you can measure depth down a sump or down a ground water well. You can use a water level meter there with just a tape and a dipper on it and it goes beep when it hits the depth and you read the depth off the tape that's on it. Then the one below that they're data logging pressure transducers you set up and program them to measure at a frequency of level measurement and you come and manually download those or if you want to hook those same things up you can hook them up to telemetry and have that data beamed back to your office. Some of the things that get in the way of an easy time for leachate monitoring are listed on the left here these leachate characteristics. Leachate does get hot right and it can be hot within the waste because of microbial activity and the wet of the waste typically the hotter it gets but the second one which I've discovered on the recent project is leachate can get hot in the leachate lines because quite often they run across the surface of the caps and they get hot those pipes absorb the heat and you can see a sort of diurnal fluctuation in the temperature and that affects things like the pressure in the lines because it's not just leachate in the lines there's also gas and gas is expandable so it's quite interesting to see that as a potential impact on how we measure such things. As we heard from Tyson we use these microbes to treat leachate but they're also a problem they clog up instrumentation so you've got to be a bit careful what sort of instrumentation you choose it's very easy to have them working very well at the start at the end and not able to work so sometimes it's good to find a contactless way to measure. You have multiple contaminants of concern we had one question, one of the questions was what to do about PFAS to the best of my knowledge there isn't a real time PFAS monitor so I think we're sort of tied to laboratory analysis around that dissolved and fugitive gases so they get in the way sometimes of good measurement some of these will bubble and other leachate will have a really high level of dissolved gases in it that can affect the accuracy of instrumentation particularly around the measurement of water quality finally the actual solution is pretty corrosive soup and you want to be thinking about the materials that you're selecting that you're going to be putting in contact with it okay so couple of golden rules for you if you can avoid measurement instrument contact with leachate then do so okay there are quite a few non-contact ways of measuring some of the parameters we need have a look at them so flow is a classic where you can use electromagnetic flow meters to measure flow without having to have them in contact with the leachate going down the lines that's very useful leachate levels you can use bubblers or you can use ultrasonics to measure or even sonics to measure level without actually contacting the leachate with any electronics and similarly with leachate pond level I've got visual there sometimes all you need to do is have a gauging and manually write down a level sometimes that's enough other times it needs to be automated second opon is if we do have to contact with a leachate let's just choose some smart materials so we often use ceramic type sensors or titanium sensors to avoid corrosion particularly around sort of pressure transducers some things about what goes wrong in sumps so pumps are buzzing away and mechanically disturbing the environment that we're trying to monitor in and some of the devices that we have down there are holes are sensitive to that so you can have vibration and you can have basically like electromagnetic influence from some electrical pumps which I've seen destroy whole sensor networks so need to be a little bit conscious of that a lot of sites have got pneumatic pumps these days so that's less of a concern but it's a good idea to keep your monitoring device separate from your pump and that means often it's good to run a casing like well casing down the side of these vertical sumps or even down the inclined sumps just to protect the sensors and it allows you to be able to remove them and replace them as you require rather than pulling a whole pump up to get this answer so some thought needs to go into that bubbling in sumps can cause the water level or the leachate level to be disturbed so in those sorts of instances it's quite good if you've got a device that's actually submerged so that's one of those things where there's a wind in having it submerged but there's a problem with corrosion and that sort of thing so it's worth thinking about Bubblers which allow you to measure the level from the surface and you have a tube down in the sumps they're good because you can just strap the tube to the actual riser pipe of the pump so deployment can be done in conjunction with the with the pump deployment and typically you don't need to remove your bubbler line to clog up every now and again but there's various bubbler units with fairly large compresses attached to them that help keep those tubes clear a couple of things around flow measuring flow I'd stay away from impellers early on we did a project using impellers for leachate and that didn't work forever so I'd be steering you towards avoiding the temptation of saving money and putting in em flow meters sometimes you've got to measure very low flows right so sometimes we monitor lysimeters and those flows it's really a seepage through the land for caps so technically it's not leachate because it hasn't come in contact with the waste yet but it is stuff moving towards becoming leachate so I've rolled it into this they're very low flows so you can actually use a little tipping bucket arrangement that the flow that comes out of the lysimeter goes through and it tips tips and we count the tips and that tells us the flow rate something to be aware of electromagnetic flow meters are expensive but do a very good job however on some sites we've found that you need to reduce your leachate diameter of your pipes to achieve the accuracies of flow measurement that you want basically the wider the diameter of the pipe the less accurate the flow measurements are so sometimes there's a bit of a trade-off and you heard Tyson talking about pumping leachate it's great but it brings silt with it and if you change the diameter of pipe it is often a good spot for that silt and stuff to get clogged so be aware of that little trap you can measure inline pressure and that can be good you just need to be careful that some of those sensors do get affected by leachate and clogged up and necessarily all that reliable on one recent project I did find this temperature effect which I just sort of put in for you which was this diurnal effect of temperature during the day on the pressure readings that we're seeing within the pipes and this was confirmed with two different sorts of technology measuring the pressure so it is real and it raises some thoughts about okay when does one read a measurement and how does that tie into compliance but we're thinking about alright running at a time so we're already out of time I do apologise I think we better just skip over the next couple other than to say there's some good technologies for monitoring stormwater and leachate ponds this one on the right here is a limited unit with a pressure transducer and it's just boy mounted so it's really easy to deploy in a pond so that's pretty good as I said before you can use gauge boards or you can use ultrasonics but they need to be mounted out over the top of the pond so there's a bit more cost associated with getting them set up if you've already got a structure coming out over the pond then happy days for the way to go some pictures various types of deployments the one on the left is a bubbler unit and you'll see the tube coming out the bottom of that which is going down into that leachate sump the one in the middle there it's more about monitoring the operation of pumps and that's a SCADA controlled system so SCADA systems can also be hooked up to your monitoring data to keep track of things like pump operation etc I'm not sure what that one on the right is might just be pressure transducers there's a case study we did have a question about are there solar powered leachate systems this is one that we installed for Macedon Rangers and we're monitoring this in real time and it's got solar pumps extracting that leachate on that site here's an incline sump this is up at Horsham and connected up to telemetry and I think that's got it's got a bubbler deployed down that sump that's a lysimeter remember I mentioned a tipping bucket rain gauge being used to measure flow that central picture there with a PVC pipe there it discharges down into that little tipping bucket rain gauge and we measure the number of tips there to give us a flow here's an example of an EM flow meter on the left and an incline PVC casing used for stormwater pond level measurement in the middle I'll skip over these so on to Q&A thanks so many people for sticking around and apologies that we've gone a little bit over time today in conclusion there's a lot to land for leachate management with many stakeholders engineering design needs to be practical and meet regulatory requirements land for leachate management needs a diverse range of knowledge to cover design leachate reticulation and treatment I think we've found in Tyson someone who has got their head around all of those aspects which is really impressive leachate monitoring considerations need to be assessed against the operational and compliance need leachate and electronics don't always get along the deployment methods and technology selection are important and that's where HydroTerror is here to help now just to see if Tyson and myself have addressed the early bird questions how is leachate best assessed and treated for emerging contaminants including PFAS I would have said it's best assessed by grabbing samples for laboratory analysis it's not going to be sort of continuous sensors in the short term Tyson do you agree with that or yeah I agree with that the only real option is land testing and then on the treatment side I'm not aware of any sites that have treatment for PFAS or such but it is possible there may be sites out there in terms of the next one we're talking about solar can you think of other standalone options that you've seen where they don't have mains power and they're needing to extract leachate solar zone I can think of the only other option is some sites are designed particularly older valley style landfills so leachate drains via gravity from the landfill into a pond common on older landfills I've been impressed with some sites where they do achieve effectively leachate transfer with no pumps just using that drainage best practice in management of leachate construction well collapsed due to waste settlement okay so that's a problem you raised what do you think you should do to fix that one there's no way of getting around it a few things you can do making sure your wells are made of suitable class of pipe so it's generally a pretty thick walled pipe make sure that it's a good installation nice straight wells these sort of things so if they're not straight to start with you're only going to make things worse another one I'll mention is avoid stockpiling lards amounts of soil on your cap because it preloads it and makes it several more and makes these things worse I think you covered the next one oh sorry skip one any tips on recording accurate standing leachate levels in wide sumps look yeah I think I mentioned them though putting a casing down the side of a sump is a good idea so that's one way of dealing with that common issues encountered with leachate collection systems and rises I think Tyson's presentation covered that one as did one of our best practice liners is a good one when can environmental monitoring be stopped for legacy landfills that's an interesting question in Victoria it's sort of tied in with an auditors program of review but Tyson I'd be interested in further if you've got further take on that how long is a piece of string the best practice guidelines in Victoria refer to a period of about 30 years but really we don't know I think what we do know is that over time the amount of monitoring the number of balls frequency of monitoring can be reduced as the risk profile of the site reduces but when you completely stop it's going to vary side by side that's a good answer so the next one what have you found to be the most beneficial drilling method to access and collect leachate yep the most common method there is called a bucket drill rig this is a type of drill rig that I think is also common in things like piling but essentially it's got a large diamond organ it's a rotary of a drill rig and essentially the organ forms like a bucket so it collects the waste or drill cuttings in this bucket that bucket is pulled out and emptied back down the bore hole on that process it's just repeated that's the most common one the other drilling method that's commonly used more for monitoring bores is sonic so sonic drilling has a really depth drill through a big range of materials in terms of that sort of things do you see many people retrofitting bore wells to extract leachate retrofitting retrofitting putting them in definitely there's a lot of drilling advice happening particularly over the last 10 years or so as EPA started to have more focus on these older landfill sites at least here in Victoria where you guys go on around and put pollution abatement notices on sites and require them to essentially go and extract leachate so there's been a lot of this happening so I think touching on that same leachate monitoring for closed landfills well obviously there's a lot of that going on I think we've sort of touched on when that might come to an end in many ways it's not too similar to what's operating to ground water leachate monitoring to continue as well do you have anything to add to that? No I think we've covered it Lastly on this set how does leachate treatment and disposal embrace the principles of a circular economy are there valuable resources in leachate? I like the question every waste is potentially a resource isn't it so yes there would be valuable resources in leachate I guess the issue is it's full of all different contaminants and how do you separate that out so leachate is a lot of it's essentially fertilizer lots of nitrogen in there but that comes along with the salt and the metals and the PFAS so I'm not aware of any process that can separate that all out but the best suppression is one ok quickly on to Q&A I think we'll give it five more minutes and then we'll need to round it up we've given you an extra 15 apologies for those questions we don't get to given the heterogeneous nature of landfills how can one obtain a representative sample for risk assessment and design purposes? Can I answer that one Richard? Yeah definitely I don't have a question in relation to leachate levels or chemistry in terms of chemistry in my opinion I don't think it really matters too much we can take a few samples from different locations on the site and get an idea of what's in the leachate but generally before we test it we already know what we're going to find there's going to be high TDS levels these things they're the things we're looking for in groundwater downgrade into the site to look for contamination leachate levels a bit trickier you need lots of wells across the site landfills are quite compartmentalised so your leachate level isn't consistent across the site it can be very variable lots of wells it's a good question in terms of your levels varying as you drill lots of what do you take as your compliance level their tyson like and how do you deal with perching that's above the liner for example So a line landfill I guess as long as you've got in my opinion less than 300mm above the liner at the sub which is the EPA compliance requirement then it actually doesn't matter if there's perching in the landfill because that's not a head on the liner so it's not increasing the CP drape through the liner online landfills it's a bit tricky you just need several wells and on weather sites there's different compliance levels you know upgrading to the site you might have a higher level where groundwell levels are lower you might have a lower compliance level Makes sense Next question Regarding leachate is there any kind of rule of thumb about the proportion of leachate which is generated by waste breaking down versus infiltration of stormwater I'm wondering if leachate management can include upgrading landfill caps to reduce infiltration e.g. increasing evapotranspiration planting of phytocap etc or perhaps infiltration isn't a significant part of leachate I can talk to that one So phytocaps are a great invention that were very popular sort of nearly 18 years ago and we used to do a lot of modelling of theoretical evapotranspiration that could be achieved and we would design the thickness of the landfill caps to sort of act as a sponge to accommodate infiltration and it was based on daily sort of time step modelling unsaturated zone modelling So in theory they work well but in practice what we've found is that maintaining vegetation has been the challenge and it's the vegetation that's the key to success of phytocaps and really it probably comes down to some of Tyson's pictures there of the rainfall distribution in Australia and how easy is it to actually maintain that vegetation layer So the second part of this is what contribution does stormwater make well it's very variable and it depends on how the caps being designed in the first place but on quite a few sites I've seen there's a real correlation between infiltration being generated and people can spend a fortune on disposing of leachate because they haven't spent enough on their capping at the beginning so really important that one Very well Richard ET caps good in theory in practice as I said very hard to get right managing the vegetation if you want to minimise your leachate generation German brain cap German brain German brain Next one Do they ever link the burning off of landfill gas to use that heat to assist with leachate evaporation That's a good question Yes there are systems out there but I haven't been involved with one but they definitely do exist Okay we'll keep going I'm enjoying this What is the endgame of leachate monitoring if there's not downstream receptor Are there any landfills where monitoring is no longer required I'm not aware of many where they've closed it off and said that's the end It's a really good question There's a lot of those lists of landfills which are unlicensed across the state which there's very little monitoring activity going on but they are still on the books of the various councils and things as liabilities So I'm not sure Tyson do you have a bit more of a taste I like this question too often we just monitor because that's what you do we're not thinking where is the receptor is there any need to monitor this In my experience a lot of these particularly small landfills very worse landfills the groundwater impacts actually don't go that far and particularly for a lot of the contaminants like your Nitrogens, Ramonias they do naturally attenuate So I agree I think there can be more thought in does this need to be monitored is there an impact rather than just monitoring the life out of everything The thing is I suppose Tyson is it's a fair bit of effort to prove up that natural attenuation and then you've got to monitor that So it might be a bit of a circular argument Next question I think we'll make this the last one Has anyone had experience with WAIV units especially in colder climates Do you know what that is? What was it WAIV I think I think we'll skip over that question then, we've got time for one more Any example of site using leachate re-injection system Yes, been involved with one that's been recirculating leachate for many years I'm not sure how popular it is any more of the recirculation of leachate though It must be I'm thinking of what recirculation Yeah, that's a key one in the chore at least that's done on a more formal basis There's plenty of other sites that have done it sort of less formally But yeah, what we call that when leachate's injected is a bioreactor landfill And really the theory of a bioreactor is to speed up the breakdown of waste So you actually speed up your base breakdown your generation of gas is sped up So in theory you're getting to that endpoint when you can stop managing and monitoring this landfill fast up That's the theory behind it There are lots of considerations for a bioreactor such as you've got higher temperatures which reduces the life of the GMM rain in your liner things like that And we found at these sites like well you can't just keep pumping around in circles, you will need to extract some leachate Alright, look I think we better call it a day Tyson will email the answers through to the remaining questions Many thanks to everyone for attending and great to see so many people still online now So it's tremendous to have such a good audience And a big thank you to you Tyson That was really informative and really impressive knowledge there So thanks very much No problem, thanks for the opportunity