Water treatment W21

Added: 2026-05-13

[00:00:01]all right so in today's class we're talking about water treatment um all the different sort of methods that are mechanical and chemical and then our next class will look at sort of more biological we touch on it just briefly but so you definitely need clean water if you're using pond water and also if you're using recirculating water rain water typically is stored in a cistern and as a result can stay fairly clean but it's not uncommon to get uh contaminants in a cistern so there's still going to be some infiltration but 99 of greenhouses recirculate their water so they have to have some form of filtration and one of the reasons well sometimes uh if you're treating well water you can have things like sodium levels that are too high you're definitely dealing with potential pathogens in your water that you need to eliminate you know the ministry of environment has very strict rules around nutrient runoff from farms so that's a real reason for why we don't discharge into the environment to begin with so that means that we're doing a lot of treating of water so and then sometimes it's just simply adjusting the incoming water like your well is really alkaline or if you have rain water uh the ph is depending on where you're at very uh not not quite ideal for your irrigation purposes but so there's there's a bunch of reasons but the main one we're focusing on today is going to be particles which i should really put here is debris right debris stuff peat moss perlite roots biological flakes bits of bran and vermiculite everything that you've seen at the college is at greenhouses as well so from a biological perspective the key um fungal and bacterial infections uh well i'm going to go over them all but this is a fungal one rhizoctinia this is one that tends to rear its ugly head more in the summer when plants are a little more susceptible because of the higher heat but typically you get a black stem around just around the soil level uh and then eventually it will sort of almost damp off and then the plant chokes off its vasculature and the plant wilts and dies very quickly it's often misdiagnosed but rhizoctini is fairly common um in fact rhizoctinia attacks a lot of grass uh out out sore outdoors if it's a particularly challenging summer so anyways rhizoctinia the spores get in the water and they spread and uh infected plants can actually infect a lot of other plants very quickly if that water passes through the root zone and it's recirculated and sent onto other crops so really gotta sterilize the water to prevent that pythium you've all heard this before uh this is you know basically everything from down below the soil level starts to rot and the classic symptom is where you can slide the roots off the steel that tells you you have a pythium uh in infection and uh the roots usually are very weak or you know non-existent almost so pythium is another bad one for recirculating water phytophthora is another one uh this one uh does not have this part here it's not filamentous so you don't see any sort of fuzz uh on the structures you know this is what it looks like in a tomato this is what it looks like when it's infected in apical meristem and it's moved into these petioles um it's not so much in the roots per se it's more in the stems and upper plant structures it does move to the veins and it happily moves through your irrigation water so that's another one that we want to treat and yeah you're looking at standing water is definitely not a good thing so make sure that you keep your you know any leaks in the greenhouse are fixed so there's no constant supply in an area of water because you'll generate phytops or spores fusarium is another one otherwise known as vascular wilt it does not present as a black stem that's how you differentiate fusarium from rhizoctinia and looking at a cross section the pith has sort of an orangey brown color as opposed to a healthy one that's your first indication this is a tomato vine that's been cut with a sharp knife sharp knife lengthwise and you can see the brown uh central cambium and these are the canadia they look like little bananas that float around in the water and they get into irrigation water and they spread big time [Music] a lot of these fungal issues are more of a problem in the hotter weather in the summer but you know you can see them any time of the year but either way we treat the water year-round to make sure that we don't get uh fusarium and fusarium will also uh infect fruits this is it on a tomato obviously uh so it's not just in the vasculature but it will if it's left untreated for a long time it it just it just goes from bad to worse uh bacterial leaf spot otherwise known as xanthomonas [Music] sometimes this is fungal but a lot of the times when you see these sorts of spots it's bacterial and it's mostly to do with overhead irrigation and if you continue to overhead irrigate and water splashes off a spore area under a new leaf it will spread so it's really important to contain it and if you do have it discard the plants that are infected and and or change your irrigation practices a lot of times farms when they see this they spray with a copper based insecticide because that will suppress the bacteria uh it's fairly effective but when you're selling ornamentals this is not nice to look at so it's not popular but we do get in the veggie industry as well with tomatoes and that's what where we see them mostly where we see bacteria leaf spot but it's everywhere even in niagara walking around the summer you'll see it on peach trees and plums and yeah so clean water lastly i believe this is my last one there is erwinia i don't know if you guys have heard of this one uh it often affects succulents this is a picture of an orchid but i've seen it in cacti and in [Music] the aloe plants and stuff like that but any succulents are they seem to be quite prone to erwinia but it can be in other stems it's just maybe a little easier to see in succulents but you get kind of a glassy soft you can see that here this sort of glassy edge between a normal leaf and the bad section and again they move to the vasculature so they'll spread throughout the plant and of course if you get water bouncing off this onto neighboring plants it spreads so uh clean water is absolutely essential so what are the basic stages of water treatment so in a greenhouse typically we have a coarse pre-filter and this is what removes big objects from returning water after irrigation things like soil and perlite and vermiculite and care tags and yeah whatever then we move on to fine filters and then lastly we have a biocidal stage where the water is disinfected so we're going to go through the different types of equipment and their pros and cons so yeah coarse filter removes large debris anything greater than a millimeter uh typically this is a a a larger volume of waste in this area so it you know it's got either a higher throughput or a larger surface area to deal with all the debris when it comes to fine particles less than one millimeter sometimes all the way down to ten or even five microns these are what we call our final filters these are ones that we put in place to make sure that drippers don't plug that kind of thing but they do not stop bacteria and spores and viruses from passing through then there's the biocidal stage which is where we kill bacteria fungi and spores and sometimes viruses but not always okay so the disinfection stage um we're gonna look at a lot of these today and uh there's a lot greenhouses spend a lot of time and energy on clean water because that is critical for safe efficient uh production of crops because if you end up spreading disease through your entire crop your losses can be massive [Music] bacterial canker another good example uh you know clean water is really important so um so there's things like pasteurization that's how our milk is treated at the grocery store uh uv bromine sand filters slow sand filters we're going to go through this whole long long list um but before we do that i want to lift off some things that you should consider so these are important questions i put on quizzes and midterms so how effective is it right are there limitations you should always know you know do you need redundancies uh what is it capable of what's it not capable of uh how long is it active this is this relates to sort of sterilizing procedures uh and how quickly they react so we'll talk a little bit about that but for example uv light can shine through the water and will you know destroy living organisms even viruses as they pass through the water but the flow of the water through the uv light impacts how long the water is exposed to the uv light and so you need to know if your exposure time is long enough to kill everything that you need killed and more often than not that is not the case so you have to be really careful that would be just one example how expensive is it to operate what are the costs is it electricity does it have chemicals is there media that you have to constantly replace what is the maintenance and labor you know what's that gonna cost you to operate the system so those are other important considerations and lastly how adaptable is it to load this sort of relates back to you know the contact time because depending on the time of the year your biological load can be high or low typically in the winter biological load is lower and in the summer it's higher especially if you have an outdoor irrigation pond um and so then we have to make sure that when we have you know flow rates that our system is capable of handling that load so that goes back like i said to longevity longevity of the the sterilizing action so in these cases a chemical you add to the water that stays in the water is going to continue to act on sterilizing the water as it flows through the pipes not one specific locale where it has contact and then it's gone um all right coarse filters let's talk a little bit about that um these are to remove large contaminants so the common ones are sand media filters this is sort of what you see in a pool disk filters cascading screens and cascading screens with paper media uh we'll go through them all and i'll tell you right now that this this one here is probably one of the most common in the ornamental world and i think i've seen it in a number of uh commercial veggie houses as well um note as i go through these slides up here in the top corner is sort of help you to give a clue as to where we are in the different types of filters because some of these filters like uh you know for example they qualify as both a coarse and a fine filter and some are only a fine filter and some are only a coarse filter so just be aware of that nomenclature as i'm going through the slides so um a sand filter this is a typical this is your standard pool filter if you've ever seen one they operate in the same principle in a greenhouse they're typically a little larger and they're made of steel and they look kind of more industrial but the principle is exactly the same the idea is that when you're in the filtering process water comes in and is pushed through the sand it migrates through the sand to the bottom and then goes into collector tubes which you can see over here and then goes back up the center and comes out filtered clean now when you want to uh when the filter starts to plug up from debris and your out your outflow rate starts to diminish you know you're getting very slow output you backwash the filter and what that really means essentially is all you do is reverse the flow so you come down the center out the bottom collectors and through the sand and up and out and divert this to waste to your septic system or whatever and as you reverse the flow the sand all lifts in suspension typically you don't lose much because it's too heavy to fall out of the filter they're designed the vertical height is such that you know the sand uh will agitate but not exit necessarily out the backwash but the debris all the stuff that was filtered out will actually make its way out so you get a flush of dirty water and so typically there's a sight glass and you you backflow the water until the water coming out is clean and then you stop it and reverse it to normal filtration direction there's another on the right this is a commercial greenhouse configuration these are the sand filters and these are the various valves for whether you're back filtering back washing or you're actually filtering so and then here's the pool system showing you how it how it works and normally this is all full of two-thirds full of sand i just made a real mess of it so yeah you fill the thing up to about this this crease here all full of sand and that's your filter media and sand will last for quite a long time um so what are the pros it scales to different flow rates typically sand filters can you know if their size they can go to just about any flow like flow rate you want so that's very helpful um i know for our hydroponic lettuce we used sand filters for our primary filtration and then we used ozone for sterilizing but yeah we use sand filters very successfully [Music] they are fairly low maintenance except for back washing and a lot of back washing is actually automatic there's a switch that senses when the pressure drops and then it automatically closes the valves reverses and sends the water backwards for a pre predetermined amount of time and then it automatically switches back to filtering and it will just maintain itself so you just have to keep an eye on it whoops they usually do not affect the chemistry of the water it's really important to get the right kind of sand uh it should be like a granite based sand if you get a limestone based sand it's going to make the ph really high so you got to be careful not to mention your fertilizer solution will actually dissolve it so within a few weeks your sand is actually gone um as far as you know pros they the sand filters is very effective all the way down to five microns depending on the media you use sand is not usually all the way down to 5 microns sand can go down to 10 or 20.

[00:17:21]um but 5 microns on the next slide i have a picture to show you but diatomaceous earth works really well and that will filter out bacteria but nothing will filter viruses out they're just too small we make it through um negatives yeah maybe they take up a fair amount of space but really it's not that bad um you need to replace the sand every three to five years i mean again not a major big deal it's just sand but the probably the biggest one uh is the backwash now the ministry of the environment knows that these filters backwash and they they want to know what you're doing with that backwash so it has to go into some sort of uh either a truck right truck it away and uh or it goes into a certified treatment facility that could be a septic bed if it's sized accordingly or it could be into a artificial wetland we'll talk about that next class there are some options but just be aware that they're going to be very very interested in what you're doing with your backwash diatomaceous earth is actually these are tiny little algae that are predominant in the ocean they're actually they're in fresh water too but there's a lot of them in the ocean and they show up as sort of chalk deposits because diatomaceous is actually chalk uh you know they press it into a cylinder and that's your chalk they put it as a powder into your toothpaste and that's the abrasive because these shells which are made of silica they're beautiful glass-like structures and they the uh all the different species of algae have different shapes and of course as they deteriorate they break and those glass shards when these are all broken into sharp pieces that's what this whole pile of white stuff is it's basically glass shards now they're so small it's not like they're gonna you know cut your stomach or something but you know diatomaceous earth is uh also used as a organic insecticide because this dust if you dust it on the ground and insects walk over it they get it on their joints and the glass shards actually abrade and scratch the joints to the point where the insects exoskeleton breaks open and then they they dry out and die so it's not a toxic way to kill bugs it's actually very safe if you have pets this is a great way to control insects is by using diatomaceous earth because if they eat it it's not gonna it's not gonna hurt them [Music] diatomaceous earth is used in all kinds of things it's used as thickening agents and paint uh in resins all sorts of stuff it's a big industry um it is it is mined from the ground like ancient seashores that are you know below the surface that's where we get a lot of our diatomaceous earth i believe turkey has some very big deposits but they're all over the place south america's got a bunch of mines but these are beautiful under microscopes what you're looking at here these are scanning electron microscopes of diatoms so anyways i've probably spent more time than i started talking about that um the next type of coarse filter is what's known as a disk filter these filters are more common i would say in large nurseries because they can position them out in the field they don't take a lot of space and they actually automatically backwash now it's very difficult for me to describe verbally how these work um i'll try but you should know this video link works my video file was getting big for this lesson so i decided not to include a video of this because you can go back to your powerpoint click on this and you can watch the video but uh what it is is the water comes in on the outside of these like on the outside it comes in here and goes around the outside and it squeezes through a stack of plastic disks so these are hundreds of plastic discs that are stacked together there's a mild amount of pressure put on them and the discs have kind of a rough surface so you can imagine that the water has to kind of squeeze through each of those plates so here's your your water is coming in it has to squeeze through the plates to get to the center and then exit out the filtered end and of course debris you know will start to get caught in between the discs and plug them up and eventually the water doesn't flow so well through the discs so what the system does is it actually reverses the flow so the water comes in let me get my blue color so the water comes in this way instead and shoots into the center and then shoots out the other way and knocks the debris out and it goes through the egg entrance and then diverted into a waste so there's backwash and of course what's especially cool about this is that the disks actually move apart when you reverse the flow they open up and loosen so the debris comes off very easily and then when you reverse the flow back to normal again everything snaps shut the discs all slam together again and it starts to filter again so it's it's pretty slick uh setup um i did have one of these in my greenhouse for my ornamental greenhouse for filtering stuff so hanging basket drippers wouldn't plug but i see these a lot more in nurseries uh because they have they have fields way out it's not necessarily a greenhouse you're driving on a tractor right out in the field and they run the irrigation pipes underground then they come up to different sections where they have risers and then that's usually where they put these filters so anyways watch the video to help you explain what they do now they're simple to operate they have no media to replace like they basically last a very very long time they can handle quite a high volume of throughput and especially when they're automatically back washing they're very low maintenance one of the cons is of course that it's a backwash right so what are you going to do with it same thing as with the sand filters um these typically go down to 50 microns and the really coarse ones to 200 so you're definitely not catching uh you know all your pathogens but you get you get a lot of debris but you won't get a lot of bacteria and you'll get some spores but i would not consider specter recital i would consider this a a a fine filter for making sure your drippers don't plug but it's definitely needs to be paired with with a biocidal step if you have problems like that uh these you've seen lots of times around the greenhouse these screen filters i'm not going to get in how they work you've seen that before you open up this cartridge and inside is the screen filter uh they're a bit of a pain to clean because they don't automatically backwash you have to take the cartridge out soak it scrub it put it back in again but they don't alter the chemistry but they definitely do not filter pathogens and you should know that the different colors actually mean something so we have a lot of yellow ones at the college but we do have some black ones and look at the dimensions the black ones have much larger pore sizes so they're less likely to plug up but they let more debris through depending on your drippers you might get some plugging but usually we go with yellow uh the yellow ones but uh yeah mostly of yellow and black at the college so they go down to 75 microns but these plug very quickly a lot of the times in greenhouses these small filters are just an added insurance step so for example if you have a uh you've got say your main filtration in the barn and water's going out to the greenhouse to maybe your irrigation boom typically they'll throw a couple of screen filters on the actual irrigation boom just because you don't really want that machine to get plugged because it's hard to work on and it's critical so it's easier to just to clean a little screen filter periodically to make sure your boom is operating properly rather than having to pull nozzles and put new nozzles on and it's just a real pain in the butt um micron filters you know what honestly you don't see these very often because these cartridges are expensive you know you might have one in your house which you have to replace me every you know maybe two three four months um they're definitely effective but they're expensive and you can't reuse them so that's an ongoing cost typically this is like a large capacity these tanks you just unscrew them and slide a new filter in but um honestly i don't think i've ever really seen one being used commercially in the greenhouse uh they definitely are you know they can't backwash you know you have to have a pretty clean source so they plug up instantaneously so really not sure but you know i put it there because i have seen it at cannabis facilities but maybe if you have city water coming in i could say if you're not recirculating then it could work you know your city water is pretty clean um but you know really you should be recirculating your water to prevent loss so i would say it's it's not very common um these are very common and they're pretty cool it's called a cascading screen filter and i've got a video coming up with the a similar filter that will help explain this but essentially what happens is so actually if you look here there's sand filters interesting eh so they're actually after the cascade filter so the main water that comes back from the crops is pumped up to the top of this and the water runs down like a waterfall into this box and then it's collected and pumped through the sand filters and sent out to the greenhouse now the way this works is this you can't see this this angle this slope surface is a stainless steel screen that has hundreds of thousands of holes in it and what actually happens is as the water runs down the water uh falls through the holes and lands on the other side of a box it leaks through the screen and comes out the backside so i kind of misled you there when i first described it and all the debris the perlite and the peat moss and the care tags they slide down the front and they end up in the front bucket this part here and that's how it mechanically separates debris from the water so it's called a cascade filter because the water cascades down over a porous surface and the debris that doesn't fit through the pores ends up in the front skimmed off these are very effective uh you know there's no consumables there's very little maintenance they remove all the stuff to get your water ready to go into your next stage of filtration so you don't overload your sand filters too quickly especially in an ornamental greenhouse there's a lot of perlite and stuff these are very helpful which you know there's a picture of an outdoor water reservoir this has got a cover on it so typically a lot of greenhouses use these and the outdoor water is being pumped up and cascaded down and you can see all the debris that's accumulating and the water falls through the back and then goes back into the tank and this is actually just falling on the ground which is kind of messy but you know whatever so that's a cascade filter now a cascade filter in combination with a media filter is really popular uh in greenhouses and they work really well with recirculating systems they don't alter the chemistry they catch all the coarse stuff they do not felt filter pathogens and they do go through cellulose rolls which are expensive but you don't go through that much so it's worth the expense and the main thing is that they're just really darn effective essentially what it is is a cascade filter like i just described right so there's your slope back and then that what's rolling over top of that filter is a paper media so it comes off a roll slides down the front and comes up and out the other side and that's what you're seeing in this picture you're seeing the the dirty paper that has come from the other side of the cascade and as the water runs down the the into this hollow area it percolates through to the bottom and gets filtered and the debris which collects on the paper is slowly removed as the papers rolled through the filter at a slow pace i've got a video coming up that's going to help explain this but uh so the pros works great doesn't alter chemistry you know and uh it's pretty reliable so here you can see the water is coming in right here this probe when it when the water starts to back up into this valley and gets high it touches the probe and then it triggers these wheels to rotate and they pull fresh paper down into the valley and so the dirty paper comes out the other side and is collected as waste so these are very popular primary filters and you can see here the water is cascading down the waste paper is actually going directly into a bin and when the bin is full they cut it off roll it out to a dumpster and throw it away and it's just biodegradable paper uh it's you know not a big deal and it's very clean and effective at removing large debris here you can see there's another roll ready to go um fine filtration so let's look at some fine these are sort of the finer steps that's 5 to 50 microns um not a lot of farms do super fine filtration it's not really that critical but some uh they do need to maybe propagators where they're using high pressure fog and the nozzles plug easily but so one of the more environmentally uh sustainable ways is what's called a slow sand filter and the other one is a micron cartridge right so we already saw those and we know that those cartridge filters are expensive a slow sand filter is not a pressurized one where you reverse the flow like our other sand filters what it is is a large an emphasis on large a large container in this case is underground right in this particular farm they've got pre-filters settling tanks and then they pump it into the sand filter where it percolates down through and goes into the pond and that's how they're removing [Music] particles the idea is that you have a large surface area so the water slowly percolates through the sand and the sand will you know catch the debris but because you don't backwash it what actually happens is you get biological activity right at the interface where all the particles are and that biological activity will eat it up and break it down and what's really interesting about this is the process of breaking it down also disinfects um so not to the point that you know it's sterile but uh to the point where that there are definitely some pathogens that are eliminated so that's pretty cool um there's actually organizations that sell slow sand filters to third world countries to help treat drinking water uh ecologically pretty cool um so they're low maintenance once they're built they don't have a lot of electrical demand because the water moves through passively for the most part um and if you have your properties on a grade downhill it's even better but you still have to pump your water back up to the top to use it at the farm but you can definitely percolate the water through the entire system very slowly like i said they don't eliminate all pathogens some we're going to talk more about this next class when you get into biological filters cons they can be very big you know large tanks large surface area and a big con for in canada is that they don't necessarily work well in the winter because they freeze right so not many like that other one was below the ground so there's some ground temperature so maybe in niagara there's some times when it might actually work but uh you definitely have reduced biological activity in the winter so something to be mindful of okay so once we've done our coarse filtration and our fine filtration we move on to uh biocidal strategies right so biocidal is any process or substance that is lethal to a living or reproductive biological organism or product like a spore so bacteria spore viruses uh not always viruses but we we hope we can get them but they often get away from us um typically they are oxidizers right so i've got a slide coming up that compares different oxidizing levels but other than heat pasteurization which is one method well we're going to cover them all but they're generally oxidizers and the strength of the oxidizer dictates how fast and complete it is at sterilizing so um chlorine is kind of a benchmark for the industry so there's your bleach it's kind of weird talking about this in light of covet because you know everywhere we go we're surrounded by this kind of stuff i think it's our new reality for a while anyways oxidizers are potent i don't know if you can remember the scene this is from the breaking bad do you remember the bathtub scene anyways oxidizers yeah they they burned through a lot of stuff and this is the symbol this flaming o for oxidizers because they burn and uh they can burn your skin so this is kind of a this is i i guess this is one chart that's used to kind of compare oxidative capabilities i'm going to focus on this one so they compare them to chlorine as the standard so bromine is less oxidative than chlorine then you get into things like hydrogen peroxide which is pretty good ozone very good and then of course fluorine which is you know really really strong oxidizer so uh typically in greenhouses hydrogen peroxide uh if you're adding chemicals or bromine are used chlorine is not so typical um we're going to go down to this list but i don't want to you know you'll just this is just summarizing all the different things that exist let's start with pasteurization before we get into all the oxidizing ones now there are some some big farms that actually still use pasteurization uh pasteurization actually will knock back viruses uh which is you know i guess you can consider pretty helpful but it's expensive because basically you have a dedicated boiler that has to heat all the returning irrigation water up to 80 degrees celsius and it has to stay there for a minimum of 20 to 30 seconds uh typically the they hold it for longer than that commercially milk is all pasteurized they heat it same thing uh they have high temperature heat exchangers with hot water from a boiler and the milk passes through it and the milk is heated up to 80 for a short time and that kills not all the bacteria you know they they have only about five to ten second exposure time but it kills 95 percent of the bacteria which means that your milk will last longer in the fridge because you've got fewer bacteria starting with as they start to grow again slowly in the fridge that buys you time that's why milk has an expiration date because the bacteria will begin to reproduce slowly in your fridge and get to a point where if you drink it you'll get sick so pasteurization is just to make it safe uh you know mainly going after e coli and salmonella but uh so what are the pros what's very very effective against bacteria even nematodes which are fairly large organisms can be difficult to kill with some oxidizing agents because they're big complex organisms uh but here viruses so you can imagine veggie farms there some of them might still do this because of the very fact that viruses are are impacted now uv lights will also kill viruses provided your flow rate is not too fast we'll talk about that later here's a veggie farm this is all the big tanks that store the various irrigations when they come back so you might have different feeds sunny cloudy day or fresh water reserve there's usually about six of these things um they're big you know put in perspective that's a forklift there uh and they're they're very wide anyways they take that water and they'll heat it with a boiler and hold it at uh more than 80 degrees celsius for a while and then they put another tank let it cool for a day and then they take the tank that's cool and that's what they use for irrigation for that day so it's always rotating through the various tanks there is this is an interesting thing it's a single point no residual control that means that the water is only treated where it gets heated to 80 degrees celsius as opposed to adding a chemical that is persistent in the water as it moves through the entire irrigation system it has a lasting residual action um pasteurization does not have that so that's a a downside obviously it uses energy that's not good uh that's going to cost you you know money so um it is considered old school but like i said quite a few farms still use it uh and i think it's primarily for the viruses component looking at uv uv is where basically you've got a waterproof quartz tubes that have uv lamps in them and water is passed around the tubes where they are exposed to the uv light and then they exit now uv light is bacteriocidal because as uv light shines through the water it shines through the bacteria and the viruses uh and the spores right passing through their relatively thin cell wall to the inside of the organism and uv light actually breaks dna and protein and mrna it breaks it apart and it takes too much for the organism to repair those breaks so the organism dies so it's like it's like shooting a shotgun through the bacteria as they shoot through the water going through the irrigation line now the question is if they're shooting really fast there's a possibility that they manage to escape being hit by the uv light or they they don't get enough of a dose maybe it only breaks a small piece of dna and it's able to fix it and survive so the flow rate is really important for the effectiveness of uv sterilizing system another one and this is one that concerns me with greenhouses is that these quartz glass tubes they have to be quartz because glass normal glass absorbs uv right we want the uv to penetrate through the the quartz into the water so we have to use quartz but anyways the the water that's coming back leaves residue on the quartz and it's like say this is my quartz tube over time you get a film of minerals and whatnot that form around the quartz and the uv which used to be you know really strong ends up becoming kind of weak because a lot of it can't penetrate through that film and so you have to take them apart and you have to clean the tubes at least once a year to make sure that they're actually doing anything there's lots of people that have uv filters in their homes and they probably never open them and they have no clue really if the uv is even doing anything just using electricity [Music] there's no chemicals which also means there's no residual right it only you only have contact when the uv light is shining on the water once the water exits that tube there's no no more biocidal activity so all the biocidal action happens while the water's in that short tube so your flow rate is really really critical um so you need sufficient contact time to sterilize right so that that's that's the really important one for uv light uh now i talked about i'll talk about bromination but before i do that we'll talk about chlorine because obviously kind of if you're thinking about pools and hot tubs uh chlorine and bromine are used right we've all swam in a pool and smell like chlorine pool water is not very good for plants and the main reason being is that they cannot control how much they take up and they will reach toxic levels of the plant and kill the plant whereas bromine is a little safer uh the plants don't take it up as readily so you can treat the water and it will stay in the water but you don't want any more than 35 ppm parts per million bromine in your irrigation water so growers that use bromine have to do water tests daily to make sure that there's nothing wrong because if you go above that you could kill all the plants in your greenhouse so that that's just another job for the grower to check on their daily routine um bromine is definitely effective though uh it has a residual activity which is great that means that you add it at a point this is what a bromine doser looks it goes out into the greenhouse and it is continually sterilizing the water as long as there's biological activity until it's all used up uh it does require monitoring right we talked about that testing daily you have to buy bromine pucks constantly uh typically these last anywhere from six months to a year uh depending on how much you're using but and you're looking at maybe three four hundred dollars to fill it with pucks again for the the subsequent year if there's a lot of biological loads so you're pulling from a really scummy pond uh it may not be effective at sterilizing the water completely it's it's too it's not a very strong oxidizer remember from my chart it's 0.7 of chlorine right it's on the bottom end of oxidizers it's you know not that strong at killing stuff so uh moving on to ozone ozone is a very effective sterilizer i use this in our lettuce at our greenhouse this is actually similar to one we had it's a this is a generator in here that produces ozone and it bubbles it through the water so the gas is injected and the water and with the gas injected goes through a contact tank this tank the water slowly moves up through the tank and then moves out to go into your greenhouse for irrigation and the gas that's collected at the top accumulates at little charcoal filter so the bubbles will sort of rise and as it fills it burps out excess gas now that's a really important part because ozone is dangerous for plants and we want to make sure the ozone is dissolved in the water and not released in the greenhouse as a gas so the system has to be working properly so you don't get ozone in your greenhouse but typically it is set set up so that basically you generate ozone using electrolysis and oxygen you bubble air through your water and you apply a high voltage and the oxygen instead of being o2 will recombine to o3 which is ozone right and you do that using adding electrons with these high charge plates and bubbling air through the water in the ozone which is fairly water soluble it actually reacts not just with living organisms but biological material like biofilm and as it reacts it breaks it up into smaller pieces which then flush away and yeah clean and are caught in your filter so ozone is really effective [Music] in cannabis facilities they even use ozone in the air to destroy odor so if you have you know smelly stuff coming out your greenhouse that goes through here they add in ozone by using charged plates with and it takes irregular oxygen makes ozone which breaks up all the terpenes and whatnot that are stinky and uh come out the other end as smaller molecules that don't smell so it's not just for treating water it's also an odor treater it's even used to remediate homes that have mildew problems so if there's mildew in the house they will run an ozone generator obviously you shouldn't be in there because the ozone will damage your lungs but the ozone then penetrates the rugs and sterilizes them and breaks up the mildew spores and everything and sterilizes itself it's cheap to operate all you need is a little bit of electricity not a lot it's very effective at killing bacteria and spores but not viruses too actually but it depends on whether it's a dna virus or an rna virus but the rna ones are a little more susceptible the dna ones sometimes are a bit too robust but it does kill a lot of them um there is only a little bit of residual activity not not as much as bromine for example uh but probably one of the biggest disadvantages with with ozone is it reacts with iron uh in your water so typically you have to add extra you need extra iron in your nutrient solution if you're using ozone because it will react and precipitate it out and then also if it escapes as a gas it can damage your crops if you see a lot of really white specks like this that is actually ozone damage so now typically you would see it closer to the barn where you have the machine not on the far end of the greenhouse then it's maybe something else thrip damage or something but if you don't see evidence of you know bug poop or eggs or nests and you see all these white spots think ozone if you're using ozone to uh treat your crop there's actually some crops like tobacco plants nakodiana they are very sensitive to ozone and sometimes like ornamental tobaccos if you grow them in the city they actually get spots on their leaves because of low level ozone pollution which of course is made by uv light from the sun reacting from our emissions from our vehicles hydrogen peroxide this is a this is a very effective one all you do is inject it into your water and it sterilizes the water and it has some residual activity so relative to chlorine you know it's it's a 1.8 so it's almost double the oxidative value no sorry yeah chlorine down here is 1.4 this is the volts but it's yeah it's about 50 stronger than chlorine proper anyways hydrogen peroxide is a liquid that you inject into the water it is effective against bacteria spores and viruses uh you have to be careful that you don't overdose because it will actually burn roots so that's a that but you know that's just operator maintenance and there's usually what we call the dissolved oxygen meter that you can use that will or do meter that will tell you the oxygen level in the water and the ozone so you check that regularly to make sure your machine's not overdosing your peroxide [Music] so those are those are kits that are available but anyways it has residual activity this is the nice thing so you inject it it goes out not only does it kill the bacteria in the water as it's flowing through irrigation lines but it will also remove biofilm from the pipes and the drippers uh keep them clean like for example if you look at our hydroponic rockwool blocks of the greenhouse they have some algae on the top from nutrient solution being exposed to sunlight at the top of the block and there's maybe some green on the drippers if you run peroxide in a system that actually kills all that algae uh and keeps everything clean so uh you know we don't do it at the college because we don't really have any major problems but our problems maybe actually maybe our problems are more major than that that's that might be more of a case but anyways it's something we probably could do but we don't really bother obviously you have to buy the hydrogen peroxide so that's going to cost you some input money uh it's not super cheap uh i think hydrogen peroxide you probably are looking at about a commercial like an industrial barrel size for a one acre farm every month so figure how many acres multiply that barrel that's quite a bit you know barrel is about 150 dollars so it's that's not cheap to operate uh the other thing is some plants are sensitive that's more in the ornamental world um but i haven't actually seen many plants that are too sensitive some lettuce varieties but generally speaking pretty safe it just like ozone hydrogen peroxide reduces iron because it's an oxidizing agent and a fairly strong one at that so you have to increase your iron content another system that is good at sterilizing water and this is more popular in the ornamental world and this is really only the last five years that people have started installing these but essentially it's it's like a saltwater pool chlorine generator and they're actually called electrochemically activated uh water or eca water and what you do is you put in potassium chloride so in in this tank here is potassium chloride you just dump a bunch in add some water so you have a thick concentrated slurry and then what happens is the the system will suck a small amount of potassium chloride inject it inject it into the water and then pass the water over some electrical plates just like the ozone generator uh system and it reacts with the potassium and the chloride to make oxidizing agents that then flow out into the water and have a residual sterilizing activity so eca is pretty cool um it's actually been used by janitorial janitorial companies for quite a long time they would have an eca machine in the cabinet and they would use it to fill their mop bucket or something like that um and that way they're not always adding chemicals and that mopping water will then sterilize the floor and you know what not but it's effective i can tell at killing bacteria spores and viruses um and the bonus the bonus the real bonus here is that of course you're also adding potassium so not only that but you're also adding a nutrient right you're adding uh potassium to your crop so that's that's a bonus um as far as eca is concerned it's not a very potent oxidizer it's slightly better than chlorine though so not bad not bad really so here there's a video explaining this process again if you go back to your powerpoint slides you can watch that video uh basically i'll review it you take your potassium chloride you expose it to electricity and it takes the chlorine from the chloride so your potassium chloride has chlorine and potassium and the chlorine is converting to chlorine gas so these bubbles then dissolve react with water and form hydrochlorous acid hclo or hypochlorous acid sorry and that hypochlorous acid is what does a lot of the sterilizing in the water killing bacteria and viruses and then you say well what with what about the potassium well the potassium goes through the same electrochemical process and is converted into potassium hydroxide which is a lot like drano right and what do we use drano for for cleaning pipes so the potassium hydroxide actually removes biofilm and cleans irrigation lines so it's a double whammy not only is it sterilizing but it also cleans your irrigation lines so and you get the bonus of the potassium once it's done reacting that is potentially in your soil as a nutrient so it's not wasted this is uh my attempt at uh describing with diagram how this works so you have a plus and a minus like an anode a cathode in order to cathode and the potassium chloride dissociates goes to the respective charged plate and then reacts with the water to form chlorine gas and potassium hydroxide all right so typically it's safe i haven't seen any plants that have been damaged by it there's no dangerous chemicals to store potassium chloride is not toxic sound i melt your arm it's perfectly safe i wouldn't run around drinking it but it's just salt it's what we use to clear snow in the winter because potassium chloride is cheaper than sodium chloride um there's no dangerous chemicals right like i just said there's there is no residual from the process that's really dangerous the hypochlorous acid is it reacts with the water and cleans it and evaporates like the just dissipates it's not a big deal um fairly inexpensive to buy potassium chloride like i said so what are the cons well you need to monitor your chlorine levels if something goes wrong and it has too high of chlorine level then you could maybe start damaging your crops because remember right in the beginning i said chlorine plants can't control how much they take up so if your system goes out of whack you might damage your crops and you might have too high a chlorine level and then then you'll you'll burn your crops so but other than that there's really not a lot of uh problems the eca is pretty popular i know right on the corner me from me is a big orchid grower and they put an eca about six years ago and they love it um a lot of ornamental growers use it copper silver ionization this is an interesting one i only know of one ornamental grower that uses it i think there are more but i don't know where they are uh essentially what happens here is you take a piece of copper and you apply electricity to it you notice that electricity is used in all these things these are all electrochemical reactions and i should explain that the reason being is that when you're dealing with oxidative agents we're dealing about electrons so electricity supplies the electrons that allows us to make these things but essentially with copper and silver what happens is by applying electricity to this the out the atoms come off the plate and go into solution this is kind of how you copper plate something right so you apply a voltage to the copper and then you ground the object that you want to copper plate and the copper ions will move from the copper over onto the sub whatever object you want to copper plate but in the case of the greenhouse there's copper plates inside this device and you apply some electricity and it puts copper ions in the water and copper along with silver is bacteriocidal and virus either now if any of you buy norwex cloths and stuff like that you've probably heard of that especially because of covid norwex has fine silver threads that are woven through the fabric so a small percentage of the fibers are silver and of course as you use the cloth the silver comes out into solution and the silver's bacterial cyto so that's how they help stay clean but yeah copper and silver are bacterial cyto nutrients um very effective as at killing pathogens and they do also clean up irrigation lines this is a commercial greenhouse showing here you got one two three four five maybe more of these uh cells producing copper ions into the water but some downsides uh there are some crops that are definitely phytotoxic uh remember copper or any metal although even iron is a micronutrient now it's not one that is that important to plant so we don't add it to our nutrient solutions but because it's a metal it can substitute for other metals and the plant can take it up to cytotoxic levels where you end up with uh micronutrient toxicity so you've got to be very careful that uh you don't overdo this and damage your crop the other problem is that if water is exiting your farm let's say you're backwashing a filter or you just drain out the the uh the water from your farm copper is considered a pollutant it's a metal pollutant that will contaminate your land that can cause you some serious problems so you've got to be very careful about what you do if you're using copper or silver to sterilize your water now bio filters and using more organic approaches we're going to discuss that in the next class um so i don't know why i just drew that it's just meandering but uh i think that's an interesting topic i want to put into another lesson not cram this one full we've already already got 57 slides so all right i hope you found that interesting uh i can tell you a lot of greenhouse growers you know they love their boilers and they love their water systems they're big uh big parts of their farms so all right i'll see you next time bye