 Hello everybody, hope the course is going on well. As you have seen until now, this is not a normal academic course. We are actually learning by doing through some interventions in a specific context. Last week, we focused on the problem of sanitation in Ayurveda in general. The lectures focused on a situational analysis of wastewater management in the city and followed a stepwise approach to understand the problem at the town level. Also, last week we introduced something called fecal sludge management. Fecal sludge is the slurry that accumulates in your on-site sanitation systems like the septic tanks. If it is not removed periodically, it can potentially contaminate the soil and groundwater. Having understood the problem, this week we will look at the solution space. Particularly, we will explore the different alternatives to tackle the problem of liquid waste management. We will start with different wastewater treatment technologies. This will be taken by Professor Pradeep Kalbar of IIT Bombay and it is a very technical presentation. He will be explaining the conventional model of wastewater treatment, the various processes involved in treatment of wastewater and different types of collection systems. Since our interest is in more sustainable and participatory models, we will be looking at decentralized models. For that, we move on to a practitioner, architect Letha Jaygopal. She will explain the concept of decentralized wastewater treatment and how she has deployed it in one canal in Alapura. Good afternoon. I will show that you have been already expert of decentralization. So, in my time on why decentralization or why some different approaches, but how to achieve decentralization and what are the different technological options we have that I will cover in this presentation. And whenever you have questions, you can ask. If you see this particular slide where I have put the status of water supply and wastewater treatment in India. And as you can see, there is a huge gap between wastewater supply infrastructure that has been created in India and how much wastewater treatment is required. So, there is a tremendous gap between generated wastewater or here in this particular session, we talk about the sewage which is a domestic wastewater. So, there is a gap between sewage generated and sewage treated. So, and these newer funding schemes from central government or state governments are focusing on matching this gap between the sewage generation and sewage treatment. So, there is a huge amount of funding going to come. Still it is already has come and but we are and there are so many technologies available for wastewater treatment and which want to go forward and those kind of guidance are still not there, but overall as a expert when you grow in this field, you will understand what kind of technology choice you will make in given situations. So, I have this all classifications of technologies and I will just touch upon the basic principles of how this technologies works and some case studies where those have been applied that is the overall frame of this particular presentation. So, wastewater is basically defined by two aspect is quality at the flow and both needs to be considered in the design. It is not only the quality that will govern the size of the treatment plant, but it is also the flow and flow has a different aspect that I will cover. So, it is a quality and flow both needs to be taken into account and basically we are dealing with domestic wastewater which is sewage from the urban areas or rural areas from the housing societies, the houses and sometimes we have some small commercial facility that also discharged the air wastewater, but that is accommodated into sewage or institutional like these institutions, colleges or some other institute that also gets accommodated into domestic wastewater. And how the domestic water basically varies is basically on the usage and the resurgent wastewater is affected by climate, community size, density of development, community influence, dependability, quality of water supplies and water conservation practices. So, these are these are all factors that will affect the quality and quantity of wastewater generated. For example, a city such as Mumbai will have very different kind of wastewater characteristics than a city such as Kochi or Jaipur, because they have very different climatic conditions, very different water culture and that affects the wastewater quality and the quantity. So, we will discuss that I think you have been exposed to this terminology sewage is the mix of everything and if you just decipher into what is how sewage forms is basically forms from the black water, from the brown water and grey water. Black water is a mixture of urethane pieces and the washing water in toilet that we use, brown water is a mixture of pieces plus fresh water, but when you have the urethane separate urethane separated toilets you get a brown water and the grey water is from the kitchen and bathrooms that we get. And if you in a city scale we mix all these three flows and we get a sewage typically. So, you remember this particular classification and I guess you already have been exposed and these are the typical characteristics by which environmental engineers classify the sewage. Basically we call a weak, a medium or a strong sewage water depending on the type of its characteristics. The main concern in this particular characteristics is this particular value which is biochemical oxygen demand and chemical oxygen demand. This particular parameter you see this varies or varying here it is about 100 here it is about 200 here and it is about 400 here. So, more the strength of the BOD more the basically we classify it as a more strength or more intense sewage and BOD everybody understands here anybody needs an explanation of BOD yes. So, basically yeah any other so people who understand BOD what is BOD do not tell me the lump form tell me the what means. Quickly oxygen required for what to biodegrade right, but why we do why we major BOD what is the reason we measure BOD organic to know the organic matter and its requirement oxygen requirement. So, basically BOD is a not a direct parameter is a proxy parameter. Remember BOD, COD are proxy parameter for organic pollution. So, because measuring the total organic carbon is difficult and it is costly and hence to avoid that we have this measurements called as BOD and COD which are proxy for TOC. So, more the basically oxygen demand of a particular organic compound it will exert more BOD it will exert more COD. So, and the basically COD accounts for both biodegradable and non-biodegradable component of the oxygen demand. So, basically by this classification we have the weak medium and strength as three sewage classification and depending on that the technology choice differs whichever flow you get in this particular concentration your technology choice will be different. That is the first principle you should remember. First of all check the BOD according to BOD your classification or the technology choice will change. Yeah, these are the these are the main spectrum that you should look into and what we want to achieve from this is basically we have to treat, but treatment up to what level is also question that we should not we should have some goal that at what level we should treat our wastewater. So, we have the minimum discharge standards set up by the center position control board and those gates keep updated. So, we can just go and see the center position control board website and get those different discharge standards. So, these are the typical discharge standard which is under this particular environment production act should be 6. Under that we have this particular environmental discharge standards what we need is how much basically BOD and COD and nitrogen is allowed to discharged in a given treated effluent treated wastewater for different classes such as inland surface water such as public sewer this is for irrigation and this is for marine coastal areas. So, as per this again your whether to treat or whether not to treat if has city has its own similar treatment plan and if you have a access to public sewer then you can really do not have to worry about your sewage that directly goes to the sewer and municipal wastewater treatment plan should take care that is the ideal situation based on that these guidelines are basically fixed. And so, and but when you do not have that particular facility and when you have to dispose your sewage into such kind of canal or river or a lake you have to meet BOD standard of 30 and those are becoming more strict as free with the new regulations, but this has some logic why 30 because that much carrying capacity our particular this rivers and lakes has. So, there is lot of really goes into to fix this particular discharge standard assuming there is some carrying capacity available in the natural body. And as we push ourselves from 30 to 20 to 20 to 10 to 10 to 5 the cost of the treatment goes tremendous. So, up to 30 all technology spectrum has some comparison, but as you push below that your costing becomes very different very different. Hence you basically 30 is a very safe number 30 to 20 cost will be tremendous. And then you have a train now and you know this the second thing we should think of centralized and decentralized systems and I think you have a train what is the advantages and disadvantages. And such kind of small scale treatment cluster treatment or household level those goes into the decentralized system discussion. And if you talk about the approaches for wastewater management I call that the not the treatment, but the management because it is a strategy it is not the one technology if we can solve the problem we will have been doing that, but that is not the solution. We have to look at a how what kind of management approach we should have for solving this problem. So, first is the prevention and conservation. So, before creating the sewage we should try to minimize its quantity ok. So, how we can do that is the reduce consumption with this public awareness such as you have like PANALAPI and other such initiatives. So, reduction in the water consumption will give you the more basically lesser flow, but whether your organic load will deeply your VOD will go down or go up if you reduce the consumption. Let us say in all of P we decide from tomorrow we do not we will cut off 50 percent of water supply everybody agrees. And what happens to your VOD then? More or less? Less. Because I am cutting down 50 percent of water supply. So, what are we more concentrated right. So, whether it is good or bad? Bad. Bad? Bad for whom? Bad for whom? This is all question needs to be answered and then we we can say something about it right. As a environmentalist I like it it is not bad for me because more strength because handling more strength strong sewage with less volume is more easy than having a sewage with a diluted VOD and a more volume ok. So, if for example, Jaipur sewage is more easy to treat than Mumbai sewage because Mumbai is a huge flow and VOD lesser than Jaipur because it Jaipur has a very concentrated VOD of 500 400 whereas, Mumbai VOD will be all of 200 because it gives me advantage in terms of cost because if my reactor will be very getting a continuous food that will come into when we talk about the how the reactor works. Hence our particular this reduction in consumption will give me two advantages. One is direct saving in terms of water consumption and second is I will get a more strong VOD in the sewage and that will be more easy to treat in a effective manner than having a very diluted sewage and that kind of thing ok. And for that the second strategy the efficient devices and fixtures and fittings and there can be many more things that you can have efficient devices for reducing the water consumption. So, those two particular approaches one is prevention conservation and then the basically recovery recycling and treatment. So, read it from right to left such as recovery recycling and treatment ok. So, recovery in terms of we cannot have nowadays treatment only for the sake of treatment because of the cost involved because of the kind of operation and mental that this treatment technology is required spending so much money is not possible for government bodies. Hence we should have such a plan such that we can recover the energy nitrogen phosphorus and resources and then whatever treated influence we should recycle and hence the treatment not the only for the sake of disposal ok. So, that is the whole paradigm of wastewater management we are going into. And in terms of how we enable these three things is one is household or building level treatment that is the way of the starting point of the discharges. Second is decentralized treatment schemes and third is the centralized when you have collected everything together and and when to when to call something decentralized and centralized they are not fixed guidelines those basically there are where means depend on the population density depend on the city scale. So, but yeah as soon as you decide that I do not want to create only one single treatment plan that for given location you are thinking in decentralized manner. So, basically the classification for this centralized decentralized system is given in this particular book by Professor Alsewal and Professor Al-Solika where you have the centralized sewerage system which basically has a wastewater treatment plan which can be mechanized or it can be based on natural treatment system in centralized manner. And basically you can have the upside disposal or to water bodies to land or you can reuse for irrigation purposes so that is the centralized scheme of the thing. And then in the decentralized sewerage system you have the wastewater conveyance locally and system flush toilets, septic tanks with soap beads or drain trays or further treatment before surface discharge and package treatment plants, natural treatment systems, pond constructed wetlands or reculture etcetera. And then dry sanitation systems which are like not much commonly used and basically this is the classification of centralized wastewater treatment schemes. So, coming to the now treatment part one by one will go from building level to the community level to the centralized systems. Any questions until here? So, buildings are the start building or houses are the starting point of wastewater discharges and controlling and treating flow at building help in reducing burden on city level infrastructure. So, you may have some intervention at the building level which can be helpful to reduce the organic load on the city scale whatever treatment plant that municipality may be planning. And oil and grease may be trapped at the building level or if you have a big kitchen or restaurants this generates huge kind of oil and grease. For example, in LFP you have so many spas where they use lot of oil for therapies. So, those have very high organic matter. So, it will be basically giving you lot of load. So, you can have basically this spas should be having some island gas trap for their that is the first level of intervention. And then septic tanks are practice in cities where underground drainage schemes is not yet implemented because underground drainage schemes cost a lot. So, cities in India have emerged like having septic tank and then open drain and in that whatever a reduction happens that is going into reverse. But that was fine 30, 40 years before population was not that much. Now, the urbanization has grown a lot and that much intervention is not enough. So, this plus something additional has to be there such as decentralized treatment plant or centralized. And in the building level you have the twin pits and there is very nice point book by EVAC which is a Swiss Agency for Water and it gives a very nice classification of sanitation technologies. It is a very good when look at your level when you start to understand concepts of sanitation technologies. So, it is called compadium of sanitation systems and technologies and that is the representation I have obtained from that is a twin pit toilet and I think you must have been exposed for twin pit how it works right. Anybody not knowing twin pit system one person and I do explain two person yes. So, basically twin pit is you have this particular toilet and which is a flush water toilet. So, basically people use this flush water and twin pit is because one pit will be active at one time and once this is filled this will be closed and this remains there for a year. So, that it will be composted decomposted bacterial will be there and it will be just humus fine humus of the years and that can be used for agriculture applications. And then the second pit will be active in that time. So, by that time this pit fills you empty out this pit and this system works. This is a very good system for rural areas or arperial areas where there is a land or there is a practice of having this particular leach pit. And then you have the septic tank that is a second level building level second building level intervention and septic tanks are basically again a tank for which basically do not have any design treatment, but because of the nature of bacteria in anaerobic condition they leave there and start decomposing the organic matter in the black water. And septic tanks are typically designed for handling the this particular black water only and we have the IS code for huge design guidelines for septic tanks. And there are many of the books and this particular companion that I told which also covers this particular septic tank details. And with the baffle it improves the efficiency in terms of all the solids are collected in one baffle before so that the outlet will not be having any solids. So, basically septic tank is based on a simple principle that you retain the sludge and then we will start decomposing anaerobicity and that is the main purpose of septic tank. And this size basically is governed by how much solid how much solids per day per person generates typically it is assumed that about 30 to 40 liters per year per person is required for holding this sludge for one person and then you need additional amount per day for whatever flush water that generates. So, that is basically some retention time for that. Detention time is basically whatever volume it has divided by the flow V by Q is your detention time in terms of minutes or hours. So, all this treatment plants has a basic parameter of detention time which is V by Q volume divided by discharge that is whatever input you are applying to the this particular any unit whether it is septic tank or whether it is a complicated waste water treatment plant it has a simple in the basic one of the parameter is detention time or it is hydraulic retention time. And then if you want to go for more complicated systems in a at a building scale for a very organized cities or hotels or multi-storey buildings, we have a set of array of technologies I will explain the details later, but the scheme I am explaining here at the building level. So, you can have the sequencing batch reactor, moving bed bioreactor, fluidized bed bioreactor, membrane bioreactor and which will basically take care of organic load of the sewage. So, first is organic load, but that will not be enough for if you want to reuse because if you are making so much of investment I said objective should be to reuse recycle the waste water. So, you can see here the multimedia filters the actuated carbon this kind of additional systems you can place for reviewing the 100 percent solids. So, that your at least the treated effluent loads pure and then you have the ultra filtration movements also. And I will show you one of these examples and you have to disinfect and then we can maybe recycle for our secondary purposes as air conditioning, gardening, car washing those kind of things. And this is one of the treatment plant for one high rise building at the basement where you have this particular screening of the sewage it is a building level in the basement. And this is called membrane bioreactor. So, basically it is a combination of the biological activity and membrane force both are placed together I will explain how it works later just look at the scheme. And then you have this particular plumbing system twin public twin plumbing system or double plumbing system which take care of recycle water will be used for toilet flushing. And this plants can be designed and operate because and how this can be effective because it will reduce the fresh water demand of the entire building because toilet flush is about 40 to 50 liters per person in a such kind of lifestyle. So, that much amount of fresh water consumption will reduce So, this is for a long term sustainability of the city this kind of things are available that these are like more mechanized solutions and more high tech oriented solutions. And if there is a space we can have a simple natural treatment system also which is called constructed weight lines in a scientific language where you have the septic tank at the bottom of the building again this is a high rise building and this is the basically a septic tank and it can be a baffle multi baffle septic tank also. And then you have the weight lines these are designed for a particular flow and particular beauty and this you will not realize that treatment is occurring there itself. So, you have two sets of solutions one is completely mechanized completely high tech this is also high tech this is not low tech it look low tech, but it is not low tech by the way. It requires lot of scientific principles to design and maintain this particular facility. But it gives a very different basically appearance that you are using making the use of nature and treating the waste. So, any questions here we will see we will come to the actual principles by which these treatments occur. And then come into the community scale solutions and you can basically club these natural treatment systems and make a community level treatment system such as this is the waste this is a system from Nehru Nagar Vazirabad we have to check whether it is working or not, but when we documented this particular system that was that time it was working where you have the multiple waste tabulation ponds. Waste tabulation ponds are natural basically natural system where you have a pond there is a algal activity and there is a symbiosis between algae and a bacteria. So, this is a very well system very works with very good in a natural condition. And to improve the night basically the nutrient removal you can have one or two duct width ponds duct widths are again some very specific species for that can grow on the this particular pond. And there you have the facultative pond for basically for further treatment. So, these are the pictures from that particular side and we have a book chapter which documents all this sorts of treatment approaches which is anaerobic pond facultative and vitro shift pond and basically this is the grid pond. So, this is based on use of nature, but you can see the land requirement because, but this if we plan I guess assume some of your planners. So, if you are a planner if you while grow while you plan a city or while you plan expansion of city if you leave this spaces for having this kind of treatment this will basically help city sustain in a more environment friendly manner. Because if we do not have land we have to go to those machines and then machines will work to the basic difference between these two systems is this particular systems have low rate of basically full term removal. Whereas, the mechanized systems will basically accelerate the rate of removal and hence compact the area requirement. So, that is the basic difference one here both of the systems will give the same result at the end of the day. One will have slower rate natural treatment systems whereas, engineer system mechanized systems will have higher degradation rate because of we are doing something artificially there and that is why your land requirement is coming down. And then we come to the centralized collection and treatment. So, I explain the building level I explain the community level and now this is centralized collection and treatment where there are two different types of collection system one is called combined sewer system where we put together the storm water you see here storm water is connected here and mostly in Indian cities except metros if you metros we have the combined sewer system because it is more economical. So, one moorly sewer taking the and we are very only 2, 3 months rainfall and also some finite number of dates. So, this kind of system works in India and then you have the second is separate sewer system which where the sewer sewage is taken separately and storm is taken separately. So, these two kind of systems are in place and depending on your design you have to make a choice for when you decide a collection system. So, assuming that for centralized or decentralized with at some good scale you need some kind of collection system and for that you have to keep in mind centralized basically combined sewer system or separate sewer system. And these are some wastewater treatment unit operations and processes ok. So, basically there are some physical unit operations that we use for wastewater treatment such as cleaning flow equalization sedimentation flotation or granular filtration and those are used at various stages ok. It is it does not mean that I started with this that means it comes at the start of the plan just classification from the physical unit operation point of view. And then there are chemical unit operations which are like chemical precipitation adsorption disinfection and other chemical applications and that we take use of bacteria and algae and other microorganisms which are biological unit operations. So, we make use of three principles physical force chemicals and biology this combination of these three works in wastewater treatment plan ok. And in biological treatment you have a credit less possess aerated lagoon trickling filters a point stabilization all these things ok. So, we cover that good and what are the types of collection system combined and separate and which is more feasible in India or more commonly used in India combined. What are the commonly used unit operations and processing wastewater treatment first the three classification physical chemical biological two in physical two names in physical two unit two in chemical chlorination adsorption and two processes from biological aerated lagoon trickling filters actidation process ok good. So, any questions until now clear. Now, we come to the how all these three physical chemical and biological unit processes or operations there is a difference between operation and the process are put together to have the treatment. And as per our guideline center which we have a central public health environmental engineering organization which we call CPHEO which is a agency to develop guidelines for sanitation and sewage treatment. And this I am referring from this 2013 CPHEO guideline which basically talks about conventional wastewater treatment plan ok conventional meaning this most commonly conventionally we have been treating sewage in this manner. So, conventional treatment goes in this two primary and secondary and this particular in primary treatment we have the unit operation or process screening, grid removal and primary settling ok. So, in the primary treatment we take care of mostly suspended load of the particles ok. So, suspended load meaning will it remove some BOD will it remove some BOD how come. So, some motion right because even if it is a suspended, but it can be organic right. So, it will exert some BOD on the system. So, primary treatment is very essential and why I am saying this because primary treatment in primary treatment we make use of gravity that gravity will be used to settle the particle ok. Now, something that can be settled by gravity it is not wise to put it into a reactor right or for the further treatment because for the further treatment we are making use of basically additional artificial air to supply the oxygen which will increase the cost of the system because it will require more energy ok. So, basic principle you should remove basic principle you should remember is something that can be settled by gravity should be used in should be settled in primary treatment itself you should not take it to the secondary treatment because secondary treatment is a heart of the system which is meant to only convert the biological the dissolve BOD into suspended BOD ok. So, basically that conversion happens in the this reactor and there are different types of reactors ok, but basic treatment if you want to remember first principle is to remove the screen screen will help it is remove the floating material such as a plastic or something will come that will be obstructed with the screens. Then you have the green basically sand sealed particles of more large diameter which will settle which are mostly inorganic in nature those will be removed and then in the primary sedimentation time PST primary sedimentation time or it is also known as clarifier ok, primary clarifier ok because that is the settling settling of the solids ok and then this all very now everything you have removed that is subjected to the this particular biological reactor. The most commonly used biological reactor is called as activated sludge process ok. So, activated sludge process is where you see here some part of the sludge is taken back to the reactor because that particular bacteria available in the reactor are active ok and you do not have to basically always put new bacterial culture to maintain the system. You can just part of the system can be recycled part of the biomass is recycled to maintain the given concentration of the biomass in the system ok. So, this particular activated sludge process use the biomass to get removed the this particular BOD from the system ok. And whatever excess so, basically this particular reactor will convert the BOD to the suspended form and that needs to be settled down that is why secondary settling time or secondary clarifier ok and that will settle down that will be taken part of the sludge will be taken to the reactor and part will be wasted that is the excess sludge that system cannot hold or we should not keep that in the system ok. So, that is thickener and this will go back to the whatever the supernatant after thickening the sludge because this particular sludge will be very having lot of moisture lot of water into it and storage will be low. So, handling and transporting are such a voluminous sludge will be costly. So, typically we use this particular thickener and take take out whatever possible water from the sludge makes sludge more dense and again put it for the anaerobic digester because anaerobic digester will basically whatever remaining organic matter is there which is in a concentrated form now can be subjected to the anaerobic bacteria. Basically those bacteria which do not require oxygen for their metabolism ok. So, these are the bacteria which are survive on basically other form of sources than oxygen. So, here in ectodyslose process here we use use of anaerobic bacteria in anaerobic digester we use anaerobic bacteria and which provides basically methane ok bio gas and hence the energy can be recovered ok. And then you have the basically digested sludge and also supernatant is deceptive fat that is a conventional treatment plant. If you understand this all other treatments are variant of this particular scheme ok. Most of the systems require this nobody wants basically the solids into the biological reactor ok. So, and this biological reactor varies, but basic principle of recycling this biomass active biomass remains the same. Any questions here? That is the most important part of understanding wish order treatment. And this looks like in a graphical representation the screening is happening here bar screens are placed then this is the grid removal, this is primary clarifier. You see the oxygen is supplied here on some external source ok because we have to maintain the bacteria in anaerobic mode. Hence we have to supply some air from the outside and that sludge is settled and taken down for sludge processing ok. Coming to the variants of this particular treatment systems one of the conventional treatment plant works on a principle of basically this biological reactor activity sludge and bacterial mass is in suspension ok. It is a complete in suspension ok. That is why those are classified under suspended basically treatment methods, but we can attach the biomass to some media ok. So, that is another classification. So, wish order treatment methods or techniques that if you want to call what is physical chemical which are like this using the physical and chemical actions or physical forces and chemical using the chemicals which are like screening, sedimentation, ion exchange, multi media filter, adsorption, some membranes, rheumatism process and these all have its own particular unique purpose and when to use and when not to use ok. And then you have the biological system that classifies under first aerobic and anaerobic, aerobic where treatment is supplied and bacteria aerobic bacteria and anaerobic are where the bacterium are survive without oxygen. And under them you have the contact base of flow anaerobic sludge bank it UASB of flow anaerobic sludge bank it. Then you have the sludge digesters anaerobic bonds those are there. Then you have the in aerobic you have the suspended growth and under suspended growth you have the active sludge process, extended adhesion, aerated lagoons, waste ablation bonds ok. And then you have the attached growth where you have the bacterial mass is attached to some media ok. In all these technologies bacterial mass is in a suspension. And then you have the trickling filters, rotating biologists, land treatment, constricted wetlands and vermiculture these are the attached growth processes. Any questions here? This is the basic classification you should remember for anyways for the treatment ok.