 So, as NC said that this whole thing of D-WATS I will first say a little bit about D-WATS as in about how this whole thing came about actually D-WATS actually happens for just decentralized rate for treatment systems. It is actually a registered train leave or something right now. So, what as we all know that I mean we all started working in the field of salutation since early 90s I finished my course in 1990 and since then and it is sad to say that even now two and a half decades later we are still properly struggling with the same basic issues even though our country might have leaped forward in so many other sectors. It is little sad that even now about 90 percent or so of our towns and cities do not have any proper waste collection or management system be it liquid waste or solid waste and so therefore we all know the related issues of water bone diseases and all the related thing I do not have to go into details about you. So, this whole step towards trying to go for better sanitation has always been trying to explore more to the possibility. So, over the years I think there has been several models that have been tried out and demonstrated and multiplied in several parts. Right now because of the Swach Bharat mission and all that there is a much more stronger thrust on trying to make India totally open defecation free and all that. The thing is that to a certain extent we are able to tackle the containment that is we are able to do the toilets and kind of contain it taking it one step away from above from open air defecation. But that actually is creating a whole lot of new challenges. In fact right now we are working with a village in rural Madhya Pradesh where actually people where it is a small village it is just about 20,000 people or something and they have been there they have lot of fields around and all that and everyone has been used to open air defecation for a long time. The thing is that now as part of the Swach Bharat they have been given toilets but the toilets if you are not giving enough thought to what is the treatment happening then that is where the problem gets started. So they all have these leech pits which are provided which has got filled up in some 6 months time. So what do you do with the waste that is accumulated in it? So that is the next challenge. We are actually trying to solve the problem but you are creating a whole lot of new challenges in another way actually. So just keeping that in mind. So how do you start it is that there were quite a few of us, about 7 or 8 of us in different parts of India were all working in decentralized sanitation and water and related issues in our own ways. And this was if you know it was like the pre-internet and pre-Google times actually. So the only way that we were probably keeping communication was through either journals or books or like personal contacts and all that. But finally that happened actually. So it was at that time that this whole concept of whether it is possible to do a decentralized wastewater treatment system actually began probably to prove in India. And the initial systems that we were talking about were things like aquatic weeds, lagooning and all that like using duckweed for wastewater treatment and small small experiments like that. The bio gas plants and all of those. But the whole experiment actually started getting a little more trust in early 90s when there is this architect called Ludwig Saase who was based out of Germany who has been working for many years in China on bio gas plants and then he moved to India also. He actually taking off from his research in bio gas plants he came with a very strong conclusion that actually for tropical climates like India anaerobic treatment systems are much more relevant. I am sure all of you know the difference between aerobic and aerobic treatment now that not going into it. But that was one major kind of research that paved the way for the next whole set of work that happened actually. So he wrote this book which was published in 1998 which was initially called the Lone Wards. But later on the publications are called D-Wards actually. It is a publication by CDD. I think any of you can actually order the book. But it is like I find that it is still probably the easiest kind of handbook to understand all the aspects of decentralized wastewater treatment systems. So with that I think the whole work that we were all doing in different parts kind of became a little more kind of streamlined and then under Borgas, Borgas stands for Bremen Overseas Research and Development Agency which was the Germany based group who actually brought together brought Ludwig Saase and brought all of us together. And then we registered as a society in 2001. Today CDD has over 20 individuals and institutional members and we work in different parts of the country and we are kind of spread our work even in different other parts of the world. And it has offices. We right now have a small office in Kochi. There is an office in Angpur, Chennai and Jaipur. And as NC said since my inspiration, the small firm that I am part of has actually been one of the founding members of CDD and ours is a practice which actually focuses I think many of you might have heard of the name Laurie Baker who is a legendary architect who kind of inspired all of us when we were in college and trying to really be responsible in our profession actually. So our journey into the whole thing of water and wastewater and all that was like a continuum of the architecture that we practice which is trying to be more responsible and sustainable and eco-friendly and all. So today the main, the works that CDD does focus us on actually implementing the decentralized wastewater systems. We have also taken it to the next level of trying to address a fecal stretch which I said earlier if you have decentralized system then fecal stretch management is also a very important part of it. Then this whole thing of capacity building is also being addressed to and we also now have started looking into the whole issue of urban wastewater visualization which I will come to when I talk about therapy. So this is just to say we are not even working so just getting into it. So just to kind of say, just to recap like what exactly, why do we really need a decentralized approach to wastewater? We all know that centralized conventional thing that we all learn in college and we are all kind of used to see and all of our decision makers are also used to is the centralized sewerage networks and centralized sewage treatment plants. Now why are these often impractical for a country like India? We all know. One is that of course you need to lay these very extensive large sewer pipes which I think many of you might be in North India where probably the water table is not a big issue but if you are talking about places like Kerala, coastal Kerala and all that when you actually go down to about 2 feet that is 60 centimeter you are already hitting the groundwater. And then imagine laying pipes in one in hundred slope because that's what you need if you want to transport your solid sand liquids in through the water and then you can never take it by gravity I was just telling NC today that even if you are having a pump chamber at every kilometer it means that you have to go 10 meters down to actually get your connection then you need a minimum pumping volume it's really not workable actually otherwise we have to have pumping stations at every 200, 300 meters and who's going to manage all these things where is the power supply going to come to kind of continuously run and operate these pumps. So this is where we and so invariably for all these kind of centralized systems more than 50 or 60 percent of the cost goes into this whole laying surface and the objects is also extremely high. So and the other thing is about getting land which again is a huge challenge particularly for places like Kerala because where land is really kind of expensive so how do you actually get the land to kind of set up a centralized sewage treatment plan and then is it really the people have started protesting also because you don't want the cities always want to be dumped into a village area and they may not really want it and you are not having a nutrient cycle also you are kind of taking all the nutrients from a big city area kind of dump it into one area which kind of imbalances both the places. So due to all these various reasons so again yeah this is what I said so all these impracticalities is probably why these kind of systems have not been probably set up in many of particularly the smaller towns and other but it's when people whether civic administration doesn't even have money to set up such a thing let alone think of operating and maintaining it for next year and the other major disadvantage about centralized systems is that there is no flexibility in terms of how the city grows actually because there is always a limit to kind of the planners to decide which part of the city is kind of going to grow or not so even in many of the bigger cities where you have switch networks it's often found that where the lines are laid probably the development is not happening probably it's probably very difficult to get of connected to the existing lines and all that so there are a lot of gray spots or areas which never get connected. So that is why I think over the last 25-30 years particularly with the research efforts as are many others in the field of anaerobic treatment there has been a lot of research happening on decentralized wastewater treatment systems and decentralized therefore means more focused on anaerobic systems. So the advantage of course are that you can optimize it to even single household levels you can still create it to CPCB discharge standards they are often operable with minimum or semi-skilled or unskilled labor hardly any mechanical parts and comparable capital costs but the operation costs are very very low so those are probably the winning aspect so this is again just kind of saying the same things. So what exactly is DEWATS? So DEWATS is not really like one technology that you can take across the board and apply to every scale we got it as rather an approach actually so it's basically the philosophy of trying to understand how you can actually treat wastewater on the site or as close to the place of generation through biological passive means and the treatment process is a combination predominantly of anaerobic but there is also some bit of aerobic treatment of course happening and some of the anoxic also so totally the whole concept of DEWATS is actually we would like to call it as a DEWATS approach so as I said again that you can start from as minimum as a single household then you can combine a cluster of 10 or 15 houses and have a cluster level system so you can have like a simplified sewer system and have it for a cluster level so basically always try and say that more than taking about one MLD or so no longer becomes like a DEWATS system so we always try and break it into smaller systems so that they are each they are smaller modular systems which can be managed easily and DEWATS can actually treat domestic and industrial sources to a certain extent not all kinds of industrial waters I think have been it's possible to do through purely DEWATS systems but a great degree of small industries which are predominantly can be reduced to biological systems can be tackled as I said very low simple optics all these things and it can lead from 1 to 2510 cube per day there is a lot of tolerance to inflow fluctuation is something that we have realized through years of working and there is a high degree of customization that is possible that I said and it's modular all these things that we repeated so the applications of housing houses, housing colonies apartments, hotels, schools offices and campuses so it's kind of trying to see the city as smaller units you don't really have to take all the water to one place but whether you can actually treat the waste water as much as possible at the source so it can be for any of these applications is what is the basic principles of DEWATS so again as we know the fundamental need for any wastewater treatment system the first step is actually sedimentation because you need your when you have your ship and you water everything coming together your first module is often a settling so basically the different steps in DEWATS one is called the sedimentation and then you have the anaerobic decomposition that is the second part of it I just come to each of these modules actually so these are the basic modules of DEWATS I just start with each of these so basically the first treatment module in DEWATS is something that you are familiar with which we all generally call as a septic tank or it can be called as a settler so what exactly happens here is which is something that I think in India almost every house or every building has like a septic tank so what happens in a septic tank or a settler essentially is that you have your solids which everything coming together and you separate out the settlable solids and there is also you can normally a settler has about at least 2 chambers sometimes usually 3 chambers also so what happens is that your bigger solids actually settle in the first chamber and the connection between the first and the first and the second chamber is somewhere in the middle so that you have the floating matter is also arrested your sludge is also settled and then you have more of the suspended solids and bigger sludge going into your next chamber so essentially a settler or a septic tank actually probably treats gives you a treatment efficiency of only about 25 to 30% because essentially what is happening is only a high degree of settling that is happening and there will be some amount of anaerobic reaction happening in this first chamber because the sludge there is already over time it becomes active anaerobic sludge so there is some degree of anaerobic but basically the treatment efficiency of a settler or a septic tank is 25 to maximum about 40% and you normally design the settler or a septic tank for a period of about 1, 2, 3 years desludging time so I don't know about generally in Kerala and all that or in many of the south Indian places we know that we give a septic tank that is followed by a soap pit so what actually happens is that after the septic tank you actually let it percolate into the ground now this is okay as long as your water table is very low and your density of development is very very low also so as and if you have a good fight what is applied because what happens is that then you are actually relying on the soil bacteria to actually do the rest of the treatment from this 25 to what is happening but when in K comes to a case of very high density development combined with high water table and the lack of pipe water supply what is happening is that this 25-30% treated water is directly going and contaminating your ground water or your surface water or your along with your soil also so that is why you can never consider that unless it's like a very sparsely located place where you have just like one house and maybe some 50 meters later you have something some other house and your soil is very good maybe the system might still work but it doesn't work in most of urban contents at least so a biogas plant is also like a settler itself it also somewhat as the same has a little better efficiency but of course biogas plants are a little more complicated to build so they are not as popular as the normal septic tanks because you have to be very airtight and all that and there is often a reluctance in people to kind of use the biogas generated from night soil or you have to kind of have a combination of using your food waste also to feed it to it it can work but it needs a little more acceptance from people if you are needs much more skilled labor to actually build a properly designed biogas plant but effectively that also does the same the same 30% efficiency so what we have added as a next module in the DEWATS system is something that we call as an anaerobic baffled reactor it sounds very complicated but essentially it's a tank which has at least 4 chambers so what happens is that as we all know your sludge that is there in anaerobic conditions is completely sealed and all that the sludge inside naturally develops anaerobic bacteria and about 90 days time you started developing the anaerobic bacteria into it so what we do in the anaerobic baffled reactor is that you are forcing your fresh wastewater to flow downward get maximum contact with the activated sludge in the bottom then it goes to the then it comes up again and then it flows to the next chamber so in this process we actually I'll show you towards the end that DEWATS has proper designed spreadsheets that have been developed to actually work out the dimensioning and the size depth everything of each of these systems actually so properly designed baffled reactor we design the flow velocity and we design the area of contact non-property that by the time it flows through each of these 4 to 6 chambers we can actually achieve an efficiency of almost 75 to 85% just by anaerobic processes alone so this gives a massive advantage in terms of the treatment efficiency actually so basically it's a flow number of chambers where you give active contact with the activated sludge in the bottom so as you realize as it comes to the last chambers your sludge also starts coming down because a lot of the sludge is already eaten up by the fresh wastewater that is coming in charge of it so that is the anaerobic baffled reactor that we again design the baffled reactor to have a deserging period of about 2 to 3 years or something like that depending on the space available and all the conditions and all that more than that what happens is that the sludge starts getting thicker and when the sludge gets very thick it's very difficult to kind of deserge it so we could normally restrict it to about 3 years or something like that and then the last often in the last chambers of the baffled reactor we also add filter media which we call it as an anaerobic filter so what exactly is happening here is that we almost 75% treated wastewater we try to give them a little more surface area for the bacteria to actually work so these are like again up flow chambers but you have like a perforated slab here and you again do that up flow so that and this is a filter media we normally use cinder or something like that which has a lot of pores in it so there is you are creating maximum surface area for the aerobic bacteria to work so the last chamber of the last one or two chambers of the tank is now treated as an anaerobic filter which will give you an efficiency of up to 90% actually so this whole system these are all completely anaerobic processes so you just need properly designed civil constructed tanks there are no mechanical moving parts or anything like that just that it has to be designed properly and all that after that so what comes so you know that if you are looking at normal domestic wastewater your BOD is generally assumed as somewhere in the range of 300 to 350 milligram per liter is the normal BOD then you understand all these basics of BOD and COD and all that I hope that you are all familiar so if you are talking about an inlet BOD of about 50 milligram per liter by the time you finish your settler your baffle reactor and anaerobic filter you can get an outlet BOD to the tune of about 50 to 70 milligram per liter range you can achieve it by normal discharge Indian discharge standards with this alone you can let off the treated water safely into the ground that is permitted by pollution control boat now so with just completely anaerobic system you can achieve it to the level that you can actually let it percolate if you have the soil condition that your water when your soil can actually let it absorb that water safely otherwise if you want to kind of take it to the next level of treatment that you would like to reuse it for let's say gardening or any other non portable uses we add in a module which we call as a planted gravel filter or they are also generally called as constructed wetlands also so what happens in this module is that you know the general marsh areas you find these semi aquatic plants which you find in many of these marsh areas what they actually do is that they are absorbing the nutrients from the water and treating it in a way so what we are trying to do in a planted gravel filter is to kind of create that kind of environment that you actually make use of the most of these semi aquatic plants they let out oxygen through their root system so we go for shallow root systems which let out oxygen through it and you give that final aerobic treatment to this water that has come out of the aerobic filter so the planted gravel filter is basically like an open shallow tank which has about 50 to 60 centimeters of graded filter media that is filled into it and we grow a lot of these semi aquatic plants like kana or typhoon or reeds and all that depending on what local plants are available which are shallow rooted and which are kind of semi aquatic any of those plants can be used and once it flows through this and comes out you can easily get a BOD of less than 30 milligram per liter and more so after the aerobic process of water we still tend to have a slightly blackish color because it has gone through all the aerobic processes but finally with the last treatment of a planted gravel filter you can get the water as really kind of clear and it doesn't have any odor or anything like that you can safely kind of reuse it and the planted gravel filter also has the additional function that it has in pathogen removal that is also another activity that happens in the planted gravel filter so therefore the with the final treatment you can achieve it efficiency of about 95 percent so with for all normal uses like even for reusing up to gardening or safely discharging into a water body this much of treatment modules are sufficient actually and you can see that this whole systems are completely passive there is nothing that that needs a kind of very skilled operation or anything like that whatever maintenance that comes into it I just show it to you before I get into the maintenance part of it there is another module the only thing is that a planted gravel filter as you know all the other times you can do it below your ground and you can make use of the space above that for some activity very often where you get stuck with trying to do wastewater treatment systems there is a space for it because everyone will be thinking about this only after they finish the whole building and some will you check the road board is kind of knocking on their noses when they think about the wastewater treatment system so all these aerobic processes can be in subsurface tank so you can at least use the space above for something else but the planted gravel filter does need to be in the open and you can create part of your garden as some of the case studies I will show you in my next presentation you can see but it may be it is open space but sometimes you have situations when you are not even having that much of space available due to various reasons there is another model which has been developed which is called a vortex actually vortex as the name says it actually works on the same principle of the of the vortex so you are actually forcing the wastewater to create that the vortex effect so that there is maximum aeration there is maximum air contact that is happening for the water and with the vortex you can actually bring down again the treatment as much or even more than the planted gravel filter only thing is that the vortex needs power and it needs certain amount of maintenance so if you are actually working on a situation where little bit of power usage is okay and you have some kind of personnel to kind of run and operate the system a vortex can be a substitute for your planted gravel filter so so this is what an overall a T-WATT system will look like you have the settler you have the baffle reactor you have the aerobic filter you have the planted gravel filter and finally you can either take it to a pond or something like that and use the water from there for your gardening and all that can be part of your landscape feature and that kind of a last polishing pond also helps in the final package and removal also because you are exposing the water to sunlight or you can have the same aerobic process settler baffle reactor filter and you can have a vortex and then reuse it so this is the basic processes that is involved in the T-WATT system this is how a vortex looks like these are some demonstration modules which were developed just to kind of see how that actually vortex works and the kind of treatment efficiency that you can see is happening this is one project where actually you have the whole of the aerobic systems below the ground it's been landscaped over and you just have this vortex and a small collection pond so the only thing that you actually get to see is this and just to show that you can actually integrate all these things as part of your landscape so that it can all look nice and be part of your overall features of it this is just a graph which is again summarizing the treatment efficiency as I said the septic tank this is the kind of if you are talking about an England BOD of about 330 or something then out of the septic tank you might get this much of an efficiency your baffle reactor will give you this much of efficiency the the planted gravel filter you can get out a BOD as I said of less than 20 and if you have a polishing pond of kind of final correction that which can also give you a further aeration and all that so you can achieve it to less than almost like 10 milligram per BOD so this and so you can see the steep curves in the whole of anaerobic processes actually so what are the kind of maintenance that one would need to kind of do for an anaerobic treatment process so the first thing is I think I put the slides the other way around the basic day to day maintenance of course is that whenever you have any kind of a treatment system you have the first set of manholes from which you are taking your water into it you will definitely have to see to it that bigger solids like sanitary napkins or diapers and things like that no treatment system can actually take care of it so you do need to have the initial screens particularly large use areas you can talk about hotels and hospitals or campuses and all that that kind of an initial screening and almost at least two or three types of maintenance of the initial bar screens or manholes collection chambers will be something that people will have to do then the other thing is in the anaerobic in the anaerobic process that is the only irregular chambers when the initial manholes have to be taken care of and then you will just have to do the desludging depending on your design period can be lay once in one year or two years or three years you will have to kind of in a protocol for it and you will have to desludge those chambers desludging we all know right now the desludging pumps and conveyance are available I think you are going to have another session on fecal sludge treatment and management and all that so I am not going into the details of it then in terms of your planted gravel filter and all that the regular maintenance would be one is that you have to ensure that the flow in and out of the planted gravel filter is maintained so mainly because you have the plant roots which are doing so depending on your how much of treatment efficiency the planted gravel filter has you will have to trim your plants at least once in a month so that you have fresh plants growing at least once in say three months or something you will have to remove at least one third of the plants so that you are creating little more space for the new plants to grow up and improve it otherwise after a while the bigger plants with their roots will spread too much and it can lead to clogging and from our experience actually only once in about eight to ten years you may sometimes have to completely remove and clean and backwash and put back the filter but that will be like once in eight years or something like that then there will be no big filter also but other than that there are daily maintenance of these things so these are all like the regular maintenance are things that a gardener or an unskilled person can actually take care of the other side and just last couple of slides so the next step that we are trying to work on is on moving towards prefabrication of D-WATS modules because as I said for designing the D-WATS systems we need certain amount of skills on understanding the whole design parameters, the complications and all that so now CDDs are actually moving towards prefabricating all these treatment modules so that depending on your how much of volume to be treated you can actually go for a modular system so there will be like one M-Cube two M-Cube and five M-Cube and ten M-Cubes so depending on the different volume you can lay the system in series or in parallel and that probably means little more efficiency quality also and as I said when you are talking about this whole decentralized wastewater management systems the centralized city level vehicle slash treatment plant is a must so while we actually try and push on getting people getting civic administrations to move for decentralized waste management it is also very important that we simultaneously lobby with the civic administrations to set up city level vehicle slash management units because whatever is done you will have to deslutch these units once in a year or two and all that so if you are taking a whole town you can actually develop a protocol that each of these service streets will be deslutched every week or something like that so that and all those things can go to a centralized vehicle slash management the vehicle slash management again can be treated with the DEWATS system itself and you are being similar to the process that I explained earlier only thing is that the sludge volume will be more so we are normally dewater the sludge and let the sludge dry and we use the water is treated and reused for gardening model so this is the major vehicle slash management unit the first vehicle slash treatment unit that CDDS has been they have in a Haleen here in Bangalore so these are the kind of design spreadsheets I don't know how clear they are from there but essentially kind of trying to tell you that the main things that we need to look at besides the quantity of load the COD BOD there are also things like the your actual physical design parameters like how much depth can you go how much land that you have and all that the temperature factors the the the conductivity of the filter media in each of these things and load with that you go into it so based on all these things is how you actually design our dewater system so this is the last line of the presentation just kind of trying to say that the how we see dewater is that it actually is more effective in kind of closing the loop as you know because you are closing the loop as close to the place of generation as much as possible because that means that you are actually making it much more sustainable in terms of returning back the nutrients to the to the ground returning back the water to where recharging the groundwater and all that so that whole process much much more effective in a decentralized approach than when you are compared to a centralized system