Transcript for:
Wastewater Treatment and Reuse Project

my name is david william graber regional advisor and consultant to the crew and i will be introducing this session and our facilitator before we begin please note that this session will be recorded and uploaded to our academy website later today if you do not wish to be recorded or be part of the recording i kindly request that you leave the session now today's training session is session number two of our blog two today we are moving into more technical material and we'll learn about how to conceptualize the wastewater treatment and reuse project with a broad review of technological options and performance criteria we want to remind you that those who attend at least five of these six sessions will be eligible for a certificate of participation as we mentioned last week and for those who could not attend this training is offered by the crew plus academy a free platform that brings together in one place all training initiatives led by the crew plus project its purpose is to provide the space for knowledge sharing of water and sanitation solutions in the wider caribbean region crew plus is a collaborative project funded by the global environment facility and co-implemented by the inter-american development bank the idb and the united nations environment program unep in 18 countries of the wider caribbean region our crew plus is being executed on behalf of the idb by the giz id and the organization of american states and on behalf of the unep by the secretariat of the cartagena convention the project offers innovative nature-based solution to mitigate the effects of untreated wastewater on the environment and public health as we did last week we asked you to participate in two surveys the first one right now at the beginning of the beginning of the session which you can now see in the screen and in the chat is used for registration it's basically to confirm your attendance it's like signing up a sheet when you enter conference hall or a classroom the second survey is an evaluation survey close to the end of the session this survey will be used to register your full participation today and will be counted towards the certificate of participation where attendance remind you your attendance to five of the six sessions is required so please do not miss this survey very much at the end now we will allow you two minutes for you to fill out the the first survey before we start so please fill it out and then we'll proceed so we are all set now let me introduce you again to our program facilitator gustavo and eddie aditers gustavo is a water and sanitation specialist with a background in engineering he has more than 15 years of experience in basic services in developing countries in several regions he led for more than 15 years aguatuja an ngo dedicated to the promotion of innovative water and sanitation solutions in partnership with municipal governments community organizations and the private sector he's currently a consultant for the world bank in sanitation projects in various regions countries such as peru bolivia south africa ethiopia and kenya so without further ado i want to introduce you again to gustavo gustavo the floor is yours thank you david good morning everyone happy to be here for session two of the course let me start the presentation here well for today i prepared a presentation that is divided in three parts uh it follows the first presentation we had last week last week we mentioned uh climate crisis and we we mentioned that climate crisis is also a water crisis and we discussed several very good reasons why we should treat wastewater before we end up with a very bad eutrophication problem in our rivers in the oceans today's presentation is about the how how do we go about treating wastewater and starting up a reuse project so in the first part of today's presentation we will talk about different ways of treating wastewater different strategies we can adopt then we will receive a very a series of treatment trains and specific technology for wastewater treatment and we will end up with some key aspects for a reuse project that we have to take into account so let's start with this um let's talk about strategies for treating wastewater the main goal is that everyone should have access to sanitation and the wastewater generated in sanitation services should be treated all of it right so that's the main goal that's uh what we're trying to do with the global agenda with the sustainable development goals right in the screen you can see a city we which has different conditions uh we have a business district in the center then we have very urban areas maybe low-income house households then we have also rural areas but this is like a continuum right and our objective is to provide sanitation services to all there are different ways of doing this here we can see on the left side a centralized system for example a sewer system in the city with one waste water treatment plant or sewer treatment plant for the entire city in the center we can see a smaller decentralized sewer treatment plant and on the right we can see um on-site system on a within the household right so this is also a continuum of solutions so the idea is that we we can mix and match these solutions we can combine them in order to provide good wastewater treatment coverage so there's no silver bullet there's no one solution that can do all the treatment we need to combine different strategy strategies and different solutions so we can reach everyone so regardless of the type of solution we choose we we should be able to provide a good treatment service good sanitation service so this is this person sitting here in the toilet he could be in a small house in a skyscraper on a plane or an institution anywhere right the the toilet experience should be the same for everyone a very high quality service and behind the scenes we can have different sanitation alternatives different treatment technologies different strategies so as i said before we can have a centralized system like one plant for the entire city we can have two plants three plants many plants or we can go fully decentralized with online on-site solutions so the best approach is to use different strategies that complement each other as long as we get as long as we improve the treatment coverage and we create opportunities for use when we work with offsite wastewater treatment we have interfaces at home like toilets for example and or or tanks that collect the the wastewater at home but then the wastewater gets collected by sewers for example which is where it gets taken to a treatment plant it gets treated and in the best case it can be reused instead of being just disposed on the river so this is offside treatment this can be done for conventional flushing toilets with sewer pipelines or the same approach can be done for septic tanks in in that case instead of having a sewer system to collect the wastewater we have a uh several trucks that go around the city picking up the sludge on a monthly yearly basis or every couple of years to take the sludge from the septic tanks towards a specific treatment plant and then we can also dispose or reuse the the final sludge so this is the logic behind providing wastewater treatment services as a off-site right outside of the household but we can also do the same process within the household and this is called on-site wastewater treatment so the process are the processes are the same except that we're not collecting the wastewater we're not taking it somewhere else but we're trading and reusing the wastewater within the premises this is on-site wastewater treatment so those are basically the different management models or strategies in order to treat wastewater it can be more centralized more decentralized it can be off-site it can be on-site but then we have to look for technological alternatives and we have to choose to select a profit technologies for for each case and the idea behind the technologies is that they follow a certain logic and in this flow we we have some recommendations on how to uh conceptualize a wastewater treatment system so it's a very good idea to start at the end to to learn where do we need to discharge the water or how we can go about reusing the the wastewater once it's distributed so depending on on where is our point of discharge or the application for for reuse water then we will define some treatment requirements for example if we will discharge wastewater to a pristine lake then the treatment requirements will be very high because we want to prevent eutrophication of the lake so for example the concentration of nutrients has to be very low in that effluent and that will require a higher level of treatment once we define the level of treatment and the the parameters for all the um contents in the wastewater in the effluent then we can evaluate different technological alternatives that we can that will comply with those standards for each of the technological alternatives we consider we have to determine a footprint area and then we will evaluate if that footprint there if we have enough room for building that that plant if there's not enough room then or enough space enough square meters in in the place where we want to implement the plant then we need to look for different alternatives or maybe we can centralize more and take that wastewater pump it somewhere else to a more centralized plant or to wherever we have space for implementing the plant if we do have space if we do have enough space then we have to calculate how much all the cost will be for for this plan the investment costs and the operation and maintenance cost this is called the annual equivalent costs and in session five of this course uh i mean i'm sorry session four of this course uh we will learn a methodology in order to calculate the annual equivalent cost that takes into account investment costs and also operational maintenance once we have different we have the cost for each viable alternative then we can choose the alternative with the lowest cost then once we have the we have chosen a technology and we know how much it will cost to for that technology to to provide a service we need to compare those costs with the income we can generate or somebody has to pay for for the wastewater treatment costs and we call this the 3t this is taxes transfers or trade so um in tariff tar actually could be for foreign it's tariff taxes transfers and trade so all these options for generating some income that will cover the cost for sanitation so if we if our income does not cover this cost then we have to look for different alternatives if we have found if we have found a proper business plan and we know how we will cover all the costs then we can go ahead and build the system build the plans build the project so basically that's the broad the strategy options for starting a project for conceptualizing a project for waste water treatment and reuse but now in the next session we will look into some specific technologies that we can put together in order to treat wastewater as we have seen in the perception a session in the previous session our domestic industrial activities pollute water we introduce pollutants into the water and what we try to do with a wastewater treatment plant is to separate pure water from all these other contaminants or pollutants but this is very hard to do because separating solids from from water in the wastewater is like finding a needle in a in a haystack because it sewer is very diluted silver is 99 water 99.9 water and only 0.1 solids so what the treatment plant has to do is pick up those very very diluted small concentrations of solids that we have to separate from water even if we see wastewater as very dark and black is mostly pure water and a very small portion of solids but all but the soil is present in water this may be in organics or organics all of the solids present constitute only 0.1 percent of the volume of wastewater inorganic solids are mainly represented by sand metals salts organic solids are basically carbohydrates proteins and and fat all the viruses bacteria pathogens all those are also organics and present in in wastewater so we need to use different technologies in order to separate all these solids regardless of them being organic or inorganic there are specific treatment processes and specific technologies that we use for for each type of pollutant for example for inorganic solids to generate turbidity and silting in the water bodies after the treatment plant we use basically a mechanic process based on bar screens sieves grid chambers we will look at in the following slides we will see examples of each of these technologies so you can understand how they work and how they look like also suspended solids are usually organic they this organic matter demand oxygen from water and we deal with them in the primary treatment via an anaerobic digestion process some of the technologies used for this are anaerobic bonds anaerobic reactors settlers all this is a primary treatment that we will look into more detail in the next slides also organic solids can be soluble they can be totally dissolved in water and we will need aerobic processes in order to put these uh organic compounds into contact with air so bacteria will oxidize organic matter and that way treat treat the water we use stabilization bonds average lagoons activated sludge inflicting trickling filters as aerobic processes that digest organic matter using oxygen then we have the nutrients in water which produce eutrophication problems as we have seen in the previous session these components are ammonium nitrate and phosphorus we want to prevent all these nutrients from reaching water bodies these nutrients in the soil become food for plants and nutrients but in the water they create eutrophication so we use technologies such as activated sludge chemical precipitation for reducing the concentration of nitrates in phosphorus then the pathogens pathogens create diseases and we need to follow a process of disinfect this infection and basically there are three different ways of doing this the most common way of disinfecting is using chlorine but it has some problems with wastewater because in in a wastewater effluent we still have some concentrations of organic matter and if we have chlorine in direct contact with organic matter then we can create some dangerous compounds that can also create a disease so for wastewater especially for wastewater it's better to use either ozone or uv radiation which doesn't have those problems and finally there could be also present in the water some other toxic elements such as heavy metals and in that case we have to use a more advanced treatment technology such as membrane filtration or activated carbon so on the rightmost column we can see three different colors um the first two lines in green those are more passive natural technologies basically we need time for nature to do its its work on on highlighted in yellow we have semi mechanized processes for example aerated lagoons we need the blowers to to put more air on the lagoon or in um aerated filter we need to pump air into the water right and uh finally the highlighted in red are more advanced processes that usually need chemicals or some more advanced equipment to really to do the work so we set up these technologies in a series of steps from the inlet of the plant where water comes in towards the outer of the plant so we have all these different steps the first step is pre-treatment this this is placed at the beginning of the plant at the entrance of the plant of the inflow and basically um what we do in pre-treatment is to separate all the solids that come with wastewater so the solids can be coarse or can be fine large objects small objects they will be separated in the pre-treatment then we have a primary treatment a primary treatment is basically a sedimentation process and also anaerobic digestion so what you have in a septic tank for example is usually primary treatment you need a certain retention time for water to to sit there and um wait for for heavier particles to to settle down then a secondary treatment is meant to reduce organic load so for a secondary treatment is not enough to just wait but we need to add some oxygen or we need some kind of microorganisms some bacteria to do the the digestion of the organic matter in the in the water then the the sherry tertiary treatment um mostly nitrification and the denitrification uh process and also phosphorus removal is required required when we want to reach a high level of treatment especially when we have to comply with uh standards environmental standards that are meant to protect water bodies from eutrophication in that case we include a tertiary treatment if we're going to irrigate or reuse the treated water for for crops or for forests or for a park then it's not necessary to remove all the nitrogen and phosphorus and in that case we don't need to include this step that makes reuse standard less stringent on from the nutrients perspective as compared to uh discharge standards for for legs and vapors and finally the last step uh this infection or elimination of pathogens before we discharge the water the idea is to eliminate the pathogens and we have also to do that in certain types of reuse certain type of uh crop irrigation for example if we are going to if we plan to irrigate tomatoes or lettuces then we need to include that disinfection step each of these steps of the treatment train also generate other flows uh side pro byproducts uh for example in the at the entrance of the plant where we separate the solids we will get all this uh the sand and also the objects plastics whichever and we have to dispose that separately right this is all the things we're separating from water in the primary treatment we generate sludge that has to be dehydrated if we're talking about an anaerobic treatment then sludge is mostly digested and we can just dehydrate it but the sludge that comes out from secondary interior sherry treatment it needs still further treatment such as anaerobic digestion before we dehydrate before we dry the sludge so on one side we have treated water on another side we have on all the solids we have separated from from wastewater and we will also have sludge that has to be treated and disposed of so basically that's that's the generic treatment train this can take place at very very large plants centralized plants but also add very small plants or on-site the plants as well most of these steps will be included regardless of the size of the plant now in the following slides we will look at the all these steps we've talked about um so you can uh see how the heat look and uh and and have a clear idea of what each step is doing this is a a green chamber or a also a bar screen at the same time so in this part of the canal all the sand and heavier particles will settle to the bottom and then we have the bars to separate all objects in this case larger than three centimeters but then we have this other type of sieves in order to separate smaller objects so this is for sine fine solid separation in this case this is a static parabolic parabolic sieve water comes from the top we have a screen here water goes through the screen and all the objects get rejected and take and taken to a bin for further disposal this is a rotary sieve the water goes on on top here goes through the sieve into the drum and out the drum from the bottom and then you have water free of small solids here and the solids will go over the the the drum and here we will have a bin catching all the all the separated solids this is usually used in smaller plants and also in industry wastewater treatment this is a very common revolving screen for separating solids these screens can be coarse or fine we can separate large objects or small objects and this is the type of screen you see in in large plants so all that was pre-treatment and the last part of pre-treatment is separating the fats oils and grease in in the grid so this is basically a trap that we use in order to sediment all the sand and have the fat soil ingredients float on top and then we have a siphon outlet here so only the the water with no fat will come out this way to the right and the the fat and the grease will get trapped there in the small plants you can remove this fat manually all the scrum on top and in large plants you'll have a mechanized system to remove all the floating fat also the the grate and the sand at the bottom can be removed either by pumps or manually in smaller plants so that's pre-treatment now primary treatment is basically settling as we mentioned before you need a certain retention time in order to catch a sludge here in the bottom on the right side you see a picture of a classic primary settler so this is the main settler before we move to uh to the next steps also you can have a reactor that is a combined like like this one this is an abr and aerobic baffle reactor very robust simple and nice technology for smaller decentralized plants uh it's being widely used the the first part in the first larger chamber we have the sedimentation zone and then we have a series of baffles uh to force water to go into each baffle from the top down and then go up again and down again and up again and then in in each next compartment we get clearer and better water quality so again here we we have our retention time and this is similar to a septic tank but a normal septic tank is basically two chambers right in this case we have more chambers in order to gain efficiency and have a better quality effluent at the outlet another very very interesting technology widely used in tropical areas this is huge in brazil for example is the uasb reactor upload an aerobic sludge blanket reactor this is a six meter high tank in which we force the water to go from the bottom to the top and we have uh granules of sludge floating inside in the middle they create a blanket of microorganisms in the sludge and we have the water go through the sludge and the microorganisms we will anaerobically digest all the organic matter or most of the organic matter present in in water in the top of this system we have a device to separate the water from the biogas that has been created by methane here in the in the tank so methane goes up methane can be captured and burned or reused the sludge has to stay in the tank and then we have a clarified effluent going out of the of the tank on the right you have a picture of a plant like this this is the uasb reactor which can perform uh the organic load reduction with an efficient efficiency up to about uh 60 or 70 percent with without any use of energy so that's the that's the big advantage of this system very little use of energy and very small footprint as well but you need high temp temperatures that's why it's very big in brazil also in in some projects in colombia in mexico uh not so much in the in the in the north where you have a colder climate and then these reactors become less inefficient in europe and the us this type of reactor is mostly used for industrial processes but in the south is being wisely widely used for for solar treatment then we go to secondary treatment so after the primary treatment treatment we go to secondary treatment which usually blow involves some aeration process in a tank similar to the one you have seen before we can have the first chamber with the sedimentation process and then a second chamber with the aeration process we have uh blowers that inject air into the the water and these diffusers that you see on the right side on the picture on the right these diffusers create very small bubbles that go up through the water increasing the oxygen concentration in water providing oxygen for microorganisms to digest the organic matter another example of secondary treatment are constructed wetlands constructed wetlands can be a horizontal flow or vertical flow when you have vertical flow water goes from top to bottom and in that case you have an even more aerobic process as compared to horizontal flow in the picture you can see a constructed wetland in in the middle of the city you can build this in in condominiums hotels it creates a green space doesn't reduce any any smells very good technology for uh small scale decentralized plants this is probably the most uh used technology in latin america and central america in all our countries the the stabilization ponds it's just a a series of ponds that go from from deep ponds at the beginning to shallower pawns at the at the end of the process the deeper pawns are more anaerobic at the inlet and the the the shallower the pond the more aerobic it is at the end you have very very shallow ponds in order to ensure uv radiation goes through it for a disinfection so very good technology low cost but you need of course a lot of space several square meters per capita in order to build this type of ponds and finally the trickling filter a trickling filter is a cylindrical tank which is not full of water is full of plastic media or stones and you have a rotating pipe that delivers water on top of the media and the water percolates all the way down it can be two three or four meters high depending on the of the depending on the level of treatment we want to achieve as water goes down it um wets the plastic material or the or the gravel or the stones and biofilm is is developed on the on the media and the biofilm is is the filter itself the the microorganisms present in the biofilm are digesting the matter the organic matter present in water as it percolates down the trickling filter so that was another example of secondary treatment and here so you get an idea we can quickly compare some of the typical efficiencies of these different technological components for example the septic tank is very simple it's just a passive it's just passive technology mostly anaerobic if we come into the septic tank with a concentration of organic load that's a vod levels of between 200 and 600 milligrams per liter we will exit the septic tank with about 120 milligrams per liter so the efficiency is about 30 or 40 percent on of body removal on using stabilization pumps we have we get higher efficiencies maybe 80 percent of efficiency also if we use anaerobic reactors followed by constructed wetlands so instead of coming out of the system with 120 milligrams we can improve that effluent and leave the system with around 60 milligrams per liter then if we have a aerated processes such as activated sludge then we can achieve efficiencies of 90 or or higher and we can leave the the system with [Music] bld concentrations under uh 20 milligrams which is usually the the standard for discharging to a clear water to a pristine lake for example for tertiary treatment when we want to remove phosphorus from wastewater we usually use chemical precipitation this can be done at different points of the treatment process it can be done at the beginning and the middle or the end depending on the chemicals you use and how you do it usually you use aluminum in order to precipitate uh the phosphorus and then you can also use the phosphorus for something else right but uh this is the type of of tanks and system you need in order to chemically precipitate uh phosphorus in order to prevent eutrophication from of water bodies then for this infection we mentioned uv radiation before this is being used more frequently now what uv radiation does is to it breaks the dna of microorganisms and pathogens so they are not able to repeat reproduce themselves and they they die a very short wave a very intense radiation the water has to be very clear because if if the water is not clear enough then microorganisms may hide behind the turbidity and maybe they will not be they will not receive enough radiation and they can survive so in order to use this type of the same disinfection technology we need to achieve a very very uh clear effluent so as i mentioned we enter the treatment plant with high loads of body build is the blue line here we can enter the plant a small system in a small system maybe we will enter the plan with 400 or 600 milligrams of pod per liter very high concentration of organic load in larger [Music] systems such as the sewer of a large city this is more diluted in that case the concentration of body will be lower maybe 250 or 300 milligrams per liter and anyways we enter the treatment plant with a high load of organics a high load of suspended solids and when as we go from point one to point two in the graphic we're reducing this uh contaminants we're reducing the concentrations of organic lows and suspending suspended solids as we go through the primary treatment and then as we go through the secondary treatment from point two to point then we reduce the concentration further on the right you can see the total efficiency of different plants we i have built in the past with very basic technology like the one we have seen in the previous slides we can achieve efficiencies of 87 96 95 that generate wastewater that is good for reuse for example you can also see on the last two columns on the right the efficiency removal of nitrogen and phosphorus is not very high it's actually low because if we don't remove these nutrients then they will stay in the water and then we can apply them to the to the ground to the crops in order to to feed the the soil and and the crops right if we were to discharge the treated effluent to a water body then we need to reduce nitrogen and phosphorus further so that's that's a very good opportunity and an advantage of of a reuse project we if we dispose the water over land if we dispose the treated water to the ground for irrigation they our limit our standards for the factor for this nutrients will be less stringent will be lower than if we discharge directly to the water body so i will now i will share with you a short video in which you will see these treatment steps step by step i will change my screen to the video i think this animation is in spanish so i will lower the volume and there will be [Music] guiding you through the animation approaching the treatment plant this can be gravity separating all the solids that also separates and catches any object that can be presented then here we're separating fats and settling the sand in the bottom all the fats go up and the sun goes down then in this case the plant divides itself in two modules then we have the anaerobic reactors in this case three chambers the first main settling chamber then the water goes into the second chamber and into the third chamber as i mentioned before in the chamber you get a better quality one then the sludge deposited at the at the bottom of the anaerobic reactors gets pumped to the drying sludge the dry beds then in this this is the secondary treatment we have constructed wetlands unplanted in this case so basically gravel filters we did that the first part was horizontal flow and this is vertical flow so the water goes from up to bottom and gets in contact with the gravel with the stones and biofilm is is developed around each stone and the biofilm microorganisms digest the organic matter present in the in the water finally the disinfection process in this case chlorine this is a contact tank for chlorine and finally the effluent the clarified effluent living leaving in order to protect the environment and the water box [Music] stop this that video is available on youtube and also many more videos i'm pasting the link on the on the chat and i will go back to the percentage okay so those were the the technologies the most common technologies we can mix and match these technologies in order to [Music] customize our treatment plan depending on on what we need to achieve what we want to do so here are some guiding principles principles for wastewater treatment for reuse if if we want to use this reuse approach it's very important important to keep in mind these these five principles number one reduce reuse and recycle number two treat the industrial effort separately basic treatment is better than no treatment at all natural treatment wherever as possible and finally consider all costs and appropriate management models we will look into each of these principles in the next slides this is some uh examples on uh reuse and and reduce of water at home on the left uh separate urine separating toilet these toilets don't use water so you can reduce your water consumption at home in the center the second toilet you have the sink on top of the toilet so the water you use for washing your hands will then fill the the tank of the flushing toilet in that case you are reusing the water two times and on the right side of the screen is a print trading treatment system for grey water you have to take into account that about 70 to 80 percent of the wastewater generated at home is grey water this means water with no toilet water black black water is coming from the toilet everything else showers things dishwashers everything else is uh grey water and grey water can be easily treated and recycled for gardening or for parks or for crops so waters source water separation is also very important it creates an opportunity for easy reuse um on the second principle i mentioned separating industrial effluents and this is very important because when we have different types of wastewater all mixed into the same collection system then it's much harder to treat so if we have industrial effluents mixed with domestic effluent then a a simple treatment plant for sewer will not be able to treat that industrial effort and also when we talk about industrial effluent coming from chicken pigs or cows we have to take into account that each individual or these animals generate much more vod load than humans people uh generate on an average 50 grams per day of body of organic load 50 grams but one chicken generates three times as much a pig generates about four times as much and a cow generates almost five times as much so for example the farm having two thousand chickens will be equivalent to a town of people with around 6 000 people so we have to be very careful with this usually all this organic load produced by animal farms is not taken of course to treatment plants and sometimes it end up ends up in polluting waterways natural whenever possible because passive technologies such as stabilization ponds wetlands and upper land flow are simpler they don't require energy they are easier to maintain right and when we go to the other extreme and we need a lot of energy for example for reverse osmosis or for membrane reactors or for activated sludge so the more intensive the technology is the more energy we'll use it will be more energy intensive but on the other hand it will have a smaller footprint area right so it's a matter of cost benefit analysis to decide which one to use about the cost of the system we have to take into account not only investment costs but also o m costs which in in time can be just as high or even higher than investment cost if you see the the blue part of the bars here that's the investment cost and the orange part is the o m cost within the lifetime of each system so you can see a very big difference between the three bars on the left and the one bar on the right and the difference is that all the technologies on the left are less mechanized they are extensive technologies and the one on the right is activated sludge in which you need a lot of energy to introduce air into the mix into the water in order to provide oxygen and the cost of energy of course in time is very high yeah so that was the introduction to the treatment treatment strategies and also the presentation and the introduction to the main technologies for each part of the treatment process maybe up to here you will have some some questions you want to ask or share some experience we can have a couple of minutes now to to discuss the technologies before we go into the last part which is about specific key aspects for reuse project on irrigation do you have any questions on the on the chat box maybe or no there are no questions within the chat box gustavo yes sir maybe just to uh open uh some questions or at least some aspects that will be dealt with uh later on for a discussion um in waters scarce areas where water is very expensive the caribbean is extracting water from the ocean and and using diesel plants as a main source of water and the transition from primary treatment for sewage i mean from primary treatment to secondary secondary treatment would be very critical um why because you want to reduce the the pressure that you have on existing um aquifers and also reducing the cost of developing new sources of water so in choosing the technology maybe you can consider guiding the participants into some criteria in in which you can actually view wastewater not in terms of complying with uh discharge effluent standard but also the reuse and that this goes back to your initial argument about how to pick technology from having in mind that you want to have an off taker a reuse of that water in at the end of the pipe at the end of the treatment train so going from primary to secondary treatment in reducing the the um uh contaminant um content of sewage would be critical i think for reuse and for reducing the pressure on existing water sources so when water is very expensive it seems that investing in secondary treatment may be advisable and desirable to reduce the overall pressure in the water and waste water treatment system maybe you can consider that as a way i mean this is facing very expensive water in uh in the caribbean islands absolutely going into into secondary treatment treatment is is definitely an opportunity because when you have an effluent that has gone through secondary treatment then you have more options of reuse right since you have a better quality effluent you can do more things with with it as we will see in the next slides it you have to uh make your wastewater compatible to the needs of the reused application you want to implement right so the the higher the level of treatment the more opportunities you will have for um reuse yeah thank you and also sustaining the treatment with operational and maintenance costs that are reasonable we see numerous cases in latin america and probably across the caribbean of imhof tanks that are completely run down and and this dysfunctional unfunctional after after investments so even if you say that those range of technologies are reasonable in terms of the investment and operational management maintenance cost it turns out that they are not as uh as easy to maintain right so you have to have a close look at that too and in that regard i want to ask you maybe you can later on answer this if uh using a nature-based solutions constructed wetlands can be used earlier in the treatment train not just as uh to finish a secondary treatment but also earlier on um to remove uh pollutants and basically try to avoid maybe the expensive uh cost of of of some of those um anaerobic um treatment tanks right about the first part of your comment um secondary treatment yes it is more demanding on operational maintenance as compared to primary treatment and we do have we do see all these problems in treatment plans that have been built all over uh central and south america that have been built and they are not operational currently but what we see is that the problem is not so much on the investment side the problem is is is uh more on the o m side usually those plants um don't have people in charge or they don't have the technical competencies or the motivation or the budget to operate the plants right so the plants are being built but due to a lack of a sustainable manage management model or a sustainable management arrangement uh some of these projects fail and they're they're not sustainable and that's maybe the the biggest difference we want to see between the the millennium development goals and the sustainable development goals right with the development with the millennium development goals mdgs from 2000 to 2015 we were going after infrastructure just trying to reach better coverages right but now in the under the sdgs from 2015 to 2030 we want this systems to be more sustainable uh to improve the the the treatment levels and also to improve the the water bodies right to recuperate uh water and inhabited so that's a of course a big challenge that we face now so in order to make this uh secondary treatment level works to to function very well and be sustainable we should put more emphasis on the business models and the management side i think that's where we're weak okay gustavo we have a few questions now in the chat okay okay um firstly mr benita is asking what is your opinion on the nerdo technology okay uh this comes from holland very very interesting technology because it's uh granules generated in an in an anaerobic environment so very interesting because each granule is like a mini treatment plant each granule has a part of it is anaerobic part of it is anoxic so very efficient very new also they are trying to to have this as a patented technology but there's also other initiatives in other parts of the world going on the on the same direction it's very promising but not widely adopted yet some some big cities have adopted the technology but it's not widely adopted i think it's it's promising it has a lot of potential okay thank you um additionally he asked what can you recommend for the removal of fog fat oil and grease this was also asked by another participant who added that um can these be sent to the sanitary landfill can fog be sent to the sanitary landfills yes usually it depends on the place but usually the the sanitary landfill will take fog um you just have to take as much water as you can out of it and then you can you can just uh send it to the sanitary landfill with the rest of solid waste um in order to separate fog which is fact oil oil and grease from wastewater basically you need a trap with at least 10 minutes rotation time so the fat will will float no and the sand will deposit in in the bottom but if if for some reason you have too much uh fat in the in the water then it's um you can have an aerated process if you put some air air bubbles into that chamber then the the air will help you separate the fat from the sand and you will have a faster more efficient process so whenever you you have a lot of fog in the water you can use an aerated separation for for fat it's not it's not complicated but of course you will need some some mechanization and some energy for that okay another question from um risha aline um they're curious about the built-in toilet and sink they want to know what the name of it and the name of it is under the volume of the water used to wash hands fill the tank or does one have to wash several times without flushing then can this be connected to the grill water system right what you do is you just use the the sink regularly right and the water coming out of the sink will be filling out the filling up the the tank of the toilet right once the tank is full the the exceeding water from the sink will just go to the sewer right or either to the regular sewer or to the waste to the great water sooner um so you you're you're saving some water you're not saving all all the water from the sink right if the if the tank of the sink if the tank of the toilet is full and you use the sink then that water will go to the sewer but if the if the tank is uh is um empty then it will uh fill as as you use the sink and there are several companies making this uh a lot of in this use in asia but i i also seen some company i believe in colombia or peru making this type of of zinc dash toilet systems okay thank you um miss walters is asking um are there effluent water quality standards set for reels in caribbean and latin america in household and agricultural terrains yes there are some not many uh in next session on on thursday next week the the the whole session we will talk about governance and also standards and different guidelines and and we also have the participation of of a couple of experts from central america and the caribbean which will explain about the current situation of of standards and normative on wastewater and reuse okay um a comment from mr kampf his exp he spoke about his experience on pre-treatment sorry um that's my experience that any pre-treatment should be aimed on withholding carbon and transfer the carbon into me methane gas or compost not only for energy or source recovery but mainly to prevent ch4 release climate gas that means no impulse tongues or septic tanks anymore do you agree uh yes yes yes and no i i agree because if if you have anaerobic uh reactors in aerobic tanks and you are releasing all this methane methane in the air into the atmosphere of course you are polluting you're increasing your co2 footprint right um and in that case yes it's much better to dry and compost all this organic matter you will still you'll still generate a little bit of co2 but much less than if you have an anaerobic reactor now if you have an anaerobic reactor and this is mainly valid for for larger plants of course if you have a large anaerobic reactor and you generate all this biogas but you burn it or in that case you will not be generating uh methane into the air right you you can for example you can generate energy electric energy and use that energy into the same plant into the same process for example right and then you will be using less energy from from the network in that case your footprint of course will be also very very small so yeah for for smaller plants septical tanks and all anaerobic system yes you are are generating methane into into the air and it is a problem thank you so the final question the united star um what kind of treatment system options are recommended for high temperature effluents for example excellence from sugar processing and rom distilleries usually anaerobic processes work much more efficiently with higher temperatures right so but it doesn't have to be really high of course the the point is that anaerobic uh reactors are inefficient if you if the temperature of water is below say 14 degrees celsius 14 and below is inefficient for an anaerobic reactor so as you go as the temperature goes up to 15 18 20 up to 35 degrees then you have very high efficiency in uh anaerobic technology so if you re effluent this worm like 30 degrees or 35 degrees then anaerobic is is the way to go if the temperature of wastewater is high it's harder than that it's higher than 35 degrees then you should take the heat out of the of the wastewater you should take that heat out use that heat for something else and then once the the temperature is 35 degrees or below then you can use an anaerobic reaction now most processes most biological processes work better at warm temperatures between 20 and 30 degrees okay so this is our final two questions and we will be able to proceed since this will show for the dry toilets what happens to the water when you clean the section that collects the solids or you don't use water when cleaning um yes there are different types of of dry toilets the more developed these toilets are the less sticky the surface is so basically you don't need to to touch the the surface in order to clean but in case you need to clean it um most of these toilets have a chamber underneath in which you collect the the pieces right so you you you just take out the the container and you can use uh some some water and soap to [Music] with a scrub to to clean the the toilet now some other toilets use a little bit of water to to clean itself right but uh for example vacuum toilets right vacuum toilets like the ones we have on an airplane use water but they use uh half a liter of water instead of using six liters of water which is what a regular toilet uses so we have toilets that use very little water we have vacuum toilets and we also have totally dry toilets in which you need to to either take the the the plastic pipe out and clean it with water or take the bottom the container out and and clean the the other part but the idea is that if it's a very well designed toilet then there's basically no contact between the feces and the toilet and it just falls through okay mr headley is asking what type of systems would you recommend for small island states with limited land space and high energy car well that's a good one because the the the more compact you want to do the plant the more energy you will you will need no uh but um a combination of um anaerobic technology as a first step and then only a region at the very last step um for small plants it can be done at a very low cost so for for resource or hot hotels i would i would uh recommend um something like an avr and anaerobic buffer reactor followed by a very short small component of a submerged aerated filter problem if you have some some room uh for uh for a constructed well and that can be a part of the the landscape of of the premises no and you can use their fluent for irrigating subsurface irrigation of greenery and landscaping okay thank you you're welcome should we continue then yes we may proceed thank you okay this is the last part of the presentation uh and we will talk about some key aspects for implementing a wastewater reuse project we have different opportunities several opportunities one of them is crop irrigation of course if we do reuse in crop irrigation we will conserve water we will close the nutrient cycles and we will also contribute to food safety in case we are irrigating crops [Music] sit at the city-wide level we can also irrigate parks forestry for station or landscapes as we were talking before industrial use or reuse is very interesting because sometimes we need water only for process water or for cooling some process in which case the quality requirements will be very low so a lot of potential here also and in some countries such as uh israel and the netherlands they are injecting the treated wastewater into sand dunes in order to recharge aquifers so in that case they end up doing indirect reuse of treated waste water because that water goes all the way back to being drinking water uh in in this session and the also the rest of the course we're we're concentrating more on irrigation reuse for crop irrigation but which has a lot of potential but we have also we need to be very careful about uh several aspects several key aspects uh that we have to take into account for reuse in crop irrigation so here on on the left side you have um our treated wastewater right so this is for our reuse project this is our supply side and on the right we have our demand side what we want to do with the treated effluent what type of crop we want to irrigate right what's that what application is so on the left side on the supply side the main thing to take into account is the quantity right the quantity will usually be fixed right if we're dealing with a hotel then we have a certain number of rooms and number of people which will generate a certain flow of wastewater if we're talking about a small municipality or a district the same we have a number of people and so so quantity will usually be directly proportional to the number of people right and they will be uh very consistent and fixed within this uh system we're analyzing now quality can vary a lot if it comes from in an industrial process or if it's just purely domestical the domestic the quality of the wastewater will be will vary a lot and once we treat the wastewater it depends on the technology we use the treatment train we design and also the regular regulatory standards will define the effluent quality right so this is this varies a lot it depends on all these variables right the original use the technology and the standards that the treatment plant has to comply with on the right side on the demand side we have to consider the type of crop [Music] for example lettuces are different from alfalfa or from father for cows right each each crop is different because the destiny of the final destination of the product will be different and also the crop itself might have more or less resistance to different types of water different types of levels of salinity for example so in israel for example they irrigate cherry tomatoes the small very sweet tomatoes are usually irrigated with wastewater because wastewater has more salts in it and that specific crop is very tolerant to high levels of salinity and as i mentioned water for cows is different than tomatoes or lettuces because lettuces and tomatoes we eat raw we eat directly right and if they have been in in contact with wastewater that it has not been disinfected then they represent a health risk and other crops like high stem crops or or maize right we we cook we boil all those products and they are much safer for for the end consumers so those types of crops we we have to take into account and also the type of soil the permeability of the soil the more permeable the soil is the water will go down uh more rapidly and there's more risk of polluting aquifers for example so type the type of soil is very important also if the soil already con contains high concentrations of salt then there's a good chance we will have problems applying treated wastewater because we will be applying even more results to it if we have a soil with a low ph acidic soils then wastewater is welcome to that soil soil because it will stabilize the the soil you'll make it better and also irrigation practices are important the amount of water we apply the periodicity of irrigation any this also depends on the uh on how the sensible is the groundwater to our irrigation process and we will see a type of table next on on that issue so we have to manage all these uh aspects on the wastewater site and also on the reuse application side and we have to know to find the perfect match that's what is important to match the type of quality of wastewater we want we can achieve to the application we we want to apply it to so in the end uh it's a it's a health issue we want healthy people we want healthy crops we want healthy soil and we want healthy water and that's the the reason we have to to to do all this uh research on on how to match our waste water to the best application we can find when we talk about health risk and healthy people there's basically three ways we can transmit pathogens with wastewater the first way is product contamination when products such as lettuces or tomatoes are directly in contact with wastewater the second way is uh air transmission when especially if we're spraying wastewater uh using sprinklers for example there's more risk that the pathogens and bacteria will fly into through the air and reach uh people and the third way if is if we are in direct contact with with wastewater if we operate the wastewater tree treatment plant or if we are a farmer reusing reusing wastewater for for irrigation in that case we can we might be in direct contact with wastewater and we may get sick and there's also some there could be some dangerous elements in water such as selenium for example or heavy metals in that case there's basically no option for reuse if we have for example lead or mercury in water our treatment plants won't remove that right and and there's no option in reusing that because we will just uh transport those heavy metals from the wastewater to the soil to the plants to the people and that will create problems so that's one very good reason for decentralization right if we treat wastewater from uh from a hotel or from a condominium that waste water usually will not be polluted with chemicals or mercury or heavy metals which we do find in larger systems which collect water from many households and also industries there's this important guidelines from iso in order to prevent the health problems and make sure we we manage all these risks on next session we will look into those guidelines in material uh so healthy crops in in soil this concept of back ground water is is important background water means the original quality of water be before the domestic or industrial use right so if if our original water comes from deep bore bore holes for example it it might already contain some level of salinity in which case the wastewater will be very saline right and we don't want that so if we have a better background water we also have better uh treated water uh that is all the the issues about uh salt right that if we put up if we add too much salt to the to the soil then the soil will become too salty and that goes against the the crops of course so it's always a good idea to combine different water qualities in order to irrigate so if we combine rains with treated wastewater or we combine treated waste water with other source of irrigation water that's also always uh good it's a good practice so we don't saturate the soil with with salts and the soil structure has to do a lot with minerals and also with um organic load so the the sludge we generate in treatment plants or the sludge we generate via collection from septic tanks it can be a good improvement to soil because when we dehydrate this sludge we of course we stabilize the sludge and and apply it to the to the fields we can improve the structure of the soil it's a it's an improvement to the to the soil and healthy water we have to take care of the underground water and in these um guidelines from iso guideline 16 075 we will also look at these guidelines next week there are four categories on um on how sensible is the four categories on the sensitivity of the groundwater to be contaminated from the water we use for irrigation so basically there's a high sensitivity when the aquifers are very shallow and when the soil is very light so if we have less than 15 percent clay content and the aquifer is less than two meters down the surface then there's a high chance we will [Music] pollute the the aquifer the sensitivity gets down as the aquifer is lower or we have heavier soils more clay into the soil in that case the soil retains more water and the soil ends up treating the the water the the the water and the aquifer is more protected and there's a zero chance of polluting an aquifer when either there's no aquifer below the surface or there's a huge rocky rocky place there and there's no hydraulic connection between the the soil under the crop and in the aquifer itself this is very rare but in that case there's no possibility whatsoever so basically what we have to do is to apply enough irrigation so the crops take up the water and evaporate the water and not enough not so much irrigation so we don't create runoff that will end up in a watercourse anyways right so in this uh chart in this table you we can see all the green squares are this is our safe zone to operate when the aquifer is low when we have heavy soils right then we have the yellow boxes in the middle and the extremes when when we have a very high aquifer and very light soil and we're basically taking down the wastewater all the way to the aquifer that's what we want to prevent and the other two red boxes is when we have too much irrigation water and we create a high runoff with lots of nutrients that we don't think into the water course so basically those are the key aspects we have to take into account uh for considering application reuse application on crops but the specific parameters and and the and the ph and all that we will see into more detail on the next session next thursday the this presentation and other materials can be found at the web crew academy website you have the the link on the on the screen you it will also be pasted on the chat box and then we will have some sometimes so you can complete the evaluation survey at the end of this presentation in the meanwhile you can type any other questions you may have on the chat box before we end thank you yes gustavo um thanks before we pass to your final five minutes maybe to uh respond to a couple of questions please uh we ask everybody to fill out the survey um as gustavo suggested and um will allow you maybe a minute or not maybe just the along with the your response to a pending question that the general will pass to you on to you and maybe we'll just let people fill out the survey while you answer those and you and we are jordan so please gustavo um go ahead and okay first question um from edwin flores he's asking your opinion about handmade sand gravel and carbon filters for corn and bean irrigation systems some filters are great i think they are very appropriate technology for [Music] um for for reuse um widely used not only for for reuse but also for us final uh polishing of of uh wastewater treatment plants i think stem filters should be used more [Music] there's a lot of advantages in them natural technology you do need a lot of space so that's the only drawback thank you mr benito is asking your opinion on using calcium nitrate to combat h2s formation if you have oxygen deficiency in in which type of process is this and what kind of wastewater are they cheating the mistake domestic treatment okay to tell you the truth i'm i've never tried that i'm not aware of of that uh possibility i don't know if it's really necessary if you have some kind of um aerated process after the aerobic process then maybe it wouldn't be necessary to to apply that so i know in other ways i would try to to put more oxygen into the air in order to to prevent the formation of the sulfates there are no more questions within the chat but we do invite participants to open their microphone if they so require to ask any further questions thank you well thanks everybody for the participation i think we have around 60 people today microsoft david we thank you very much gustavo for your excellent presentation and we remind everybody that next week is module 3 which deals with governance standards and regulations in wastewater treatment and reuse so each module requires a separate registration so make sure to register and um without further ado we wish you a very productive day and see you soon then thank you thank you david thank you janelle thanks everyone see you next thursday thank you