 Namaste and welcome back to the video course on Watershed Management. In module number 10, lecture number 39, today we will discuss about water recycling. So, some of the important topics covered in today's lecturing route, water recycling uses, benefits, water management solutions, water recycling treatments, primary treatments, secondary treatment, tertiary treatment, conventional and modern techniques. We wait for today's lecture, water recycling and wastewater treatments. So, as we were discussing in the last lecture, so this water conservation is very important as far as the water management in a watershed basis, in a watershed is considered or in a in a in a district or in a city is considered we have to look say which way we can go for water conservation. So, that is one aspect, the conservation is one aspect and then still we may have a lot of water stress or say water scarcity in many areas. So, then especially in urban areas say where say we need a huge amount of water for say domestic, industrial and other purposes, but availability is much much less. So, there say other than water conservation, I mean by reducing the amount of use of water and the most efficient way utilization, so that is what as we discussed in the last lecture about the water conservation. But say especially in urban areas we can go for water recycling, so water recycling is mainly say we can give some treatment to the to the wastewater or the effluents generated from the particular domestic or the industrial or whichever sector we consider and then say we can use for other purposes. So, that is the the in a general way what we can define as water recycling. So, other than water conservation we have to go for water recycling, so that the water stress or the non away between water we can sort it out in certain a certain way. So, when we discuss about the water recycling, so as I mentioned water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, sewer processes, toilet flushing and groundwater recharge. So, that way say for example, if you consider a domestic purposes consent, if this is a residential building then we can see that the the water coming from the the the sinks we can separate it and then give some treatment like a same preliminary or primary treatment and then we can directly use for say irrigation like this and then say for example, the water coming from the toilet source we can do some kinds of it can pass through a safety tanga or it can be given some treatment and then directly use for other purposes. So, that way say a common type of recycled water is water that has been reclaimed from say the wastewater or sewage. So, it can be say either from the industrial sources or it can be from the domestic sources or as such the the municipal wastewater. So, as we can see that when we look into the hydraulic cycle actually the nature is also doing the same. So, through the natural water cycle the earth has recycled and reused the water for say millions of millions of years. So, the the the water is coming as precipitation and then it goes through a the hydraulic cycle and finally, it is evaporated and then finally, again coming back as as rainfall. So, the nature is also doing in one way or another way of natural water recycling. But say say as far as the the in terms of water recycling here what we are discussing is what way we can say give some treatment and reuse for various purposes either for agricultural industrial domestic or other kinds of purposes. So, that is the in terms of water recycling. So, when we look into water recycling so, we can see that when we critically analyze the water recycling. So, actually it offers the the resources as water as a resource and then that way we can see that lot of financial savings we can obtain through the the the water recycling. So, the advantage is that the wastewater treatment say we can tailor made to meet the water quality requirements of planned reuse. So, say for example, if we are going to use the wastewater for say say irrigation or the agricultural purposes. So, it may be we do not have to give for complete treatment may be a preliminary or primary treatment or secondary treatment may be sufficient depending upon the quality of the the wastewater. So, then say recycled water for landscape irrigation say for example, it requires less treatments than recycled water for say for a domestic or drinking purposes. So, if we are planning to say for example, drinking then we have to go for ender cycles of treatment like preliminary, primary, secondary and tertiary treatment and even same reverse osmosis or that kind of treatment is required if we are going to use for drinking. But for other purposes like an irrigation or the the industrial reuses that way we do not have to give that much treatment. So, that way we can see that we can save water. So, that way we get the financial savings and then also we can reduce the the amount of wastewater to be treated for various purposes. So, that way when we look into water recycling. So, water is sometimes recycled and reused on site. So, that means, say in an industrial site there itself we can simply same same give some treatments and directly utilize. So, industrial facility recycles water for cooling processes and then another type of the recycled water is water that can be reclaimed from municipal wastewater or sewage. So, we can see that as far as the municipal wastewater is concerned the the water the wastewater is collected from various sources and then the the it will be totally heterogeneous type of wastewater and then again that also we can give some treatments and then say reuse. So, that way we can see that grey water or grey water is say a reusable wastewater from residential, commercial and industrial bathroom, ceings, bath bath tub, shower drains, cloth washing, equipment drains etcetera. So, the the wastewater we can collect from various sources and then actually when we deal with the municipal wastewater it will be mix of many of these things and then we have to give appropriate treatments before we reuse for the intended purposes. So, grey water say reused on site say for example, for landscape irrigation like that. So, that way when we look into water recycling say say it depends upon the the the quality of the wastewater and then say what grade of treatment we have to give to that wastewater and then what purpose we are going to use that treated water. So, accordingly say we have to give appropriate treatments and then appropriate use we have to identify as far as the the wastewater is concerned. So, when we look into literature we can see that the recycled water we can use for different purposes. So, even though with say complete set of treatment starting from primary, secondary to tertiary and treatment like say ultraviolet or the reverse osmosis type of treatment we can use for portable purposes. So, what we say when we look into literature we can see that the recycled water is very rarely used for portable purposes only say in some cases they are totally fresh water is not at all available. So, we can see that the the recycled water is not not generally used for portable purposes, but used for non-portable purposes. So, some of the important non-portable purposes here I have a listed like agricultural. So, we can use for irrigation. So, only thing is that if say the particular product we are directly using for the consumption human consumption or the say raw weightables like that then we have to give a say better treatment as far as the wastewater is concerned otherwise there is possibility of contamination even of the weightables or fruits. So, that way depending upon the the purpose of irrigation we can give appropriate treatments. So, agriculture, landscape, public parks, golf course irrigation, cooling water for power plants and oil refineries, then processing water for mills plants, then the the recycled water can be used for toilet flushing. Then we can use the recycled water for dust control, construction activities, cone gate mixing, then we can have artificial lakes by using the the recycled water. And then say as I mentioned if we are going to use for portable purpose we have to give appropriate treatment to the the wastewater. So, say nowadays in some of the arid and semi arid regions the recycled water is used to recharge groundwater aquifers and then augmenting surface water is for reservoirs. But this is after going through a series of treatment to the the wastewater, so that a good quality recycled water is obtained and that can be used for say even to recharge groundwater aquifers or augment the surface water reservoirs. So, that way when we look into the the the recycling processes. So, as I mentioned we have to see say the the grade of the wastewater and then we have to see what kind of treatments we have to give and then what is our intended purpose of the the recycled water. So, now within this perspective let us look what are the important benefits as far as water recycling is concerned. So, some of the important benefits I have listed here, so like reduction of treated waste water discharge to sensitive or impaired surface waters, then reduction of imported water and avoided cause associated with the importing water. So, we can say recycle the water give appropriate treatment, so that we do not have to import water for various purposes. Then environmental benefits, so that way we can see that when we are not using the fresh water we are giving appropriate treatment to the wastewater and then we are reusing it. Then we can see that we can achieve sustainable water resource management as far as the the environment is concerned. Then recycled water can also be used to create or enhanced wetlands and riparian habitats. So, we can however say use this wastewater treated recycled wastewater say especially to recycle water to wetlands, we can discharge wetlands and then that can be that say some way of cleaning process will be taking place within the wetlands itself. Then conservation of other resources besides water like say we can remove chromium from a leather industry, then reuse at little extract was so only some say depending upon the use say for example, the water which we are use going to use for flushing in domestic sector or the water we are using for cooling purposes, so we do not need a very high quality water. So, that way with some minimum treatments we can use the water again, so that way we can reuse at little extract was. Then savings on water abstraction course, so say if we can reuse the wastewater or the recycled water, then we can see that instead of pumping water from the deeper aquifer systems, so we can save cost of abstraction or the cost of the power cost we can reduce. So, then reduce dependence of vagaries of river flows and then gaining tax advantages in irid and designated zones, then reduction in effluent discharge volume. So, when we are say when we are treating the wastewater and then when we are using the recycled water actually we are reducing the volume of the wastewater. So, that way the say before discharging this effluent to the river or a lake, so then we do not have to we will not have much volume that we have to give appropriate treatment. So, that way we can reduce the effluent that which is to be discharged say to rivers, lakes or the sea. So, these are some of the important benefits as far as water recycling is a consens. So, now say within this perspective, so we were discussing about what is say water recycling and then how we have to do these and then what are its benefits like that. So, now when we look into overall water management solutions say within a watershed or within a particular area or within a within an urban environment is consens, say we can go for various solutions. So, here let us discuss say what are the possible solutions, so water management solutions. So, as I mentioned earlier, so we have got water stress, so that we can indicate in terms of water stress index. So, actually this is an annual renewable water resource per capita that are available to meets needs for domestic, industrial, agriculture and other purposes. So, say we can come up with an index called water stress index for the particular area based upon the availability of water based upon the various uses. So, depending upon the supply and demand we can come up with a water stress index. So, this is one of the commonly used approach to evaluate water availability. So, as we were discussing earlier also about toothed out of the world population will be under moderate to high water stress according to the projection that to predict in 2025. And then 50 percent of the population will face constraints as far as water supply is concerned. So, that way this water recycling is say one important solution that we can look into. So, when we look into water management solutions say within the perspective water stress index we can have say we can go for water say water management solutions are concerned we can go for surface water management solutions, drainage and waste water management solutions, polluted water management and water recycling management. So, like that we can classify into four as far as water management solutions as far as a particular watershed or particular area is concerned. So, now if you look into surface water management solutions so that what we are trying to do is say with respect to the available surface water say in terms of say water available in a particular area or particular watershed or particular urban area say in terms of water available in lakes rivers or the ponds or water surface water available. So, we have to give appropriate treatment say and then use so for the or the we go for beneficial use. So, that way some of the things what are generally used to give appropriate treatment for surface water in good modular water storage units, permeable geotextiles, silt traps, vortex flow controls. So, modular water storage units means say we can have systems like a poly storm from poly pipe light weight cells with a high void ratio. So, applications include rain water, soak waste or storm water attenuation. So, this we can say we can give appropriate treatment for rain water or the storm water and then we can use for various purposes. Then as far as permeable geotextiles are concerned this is in conjunction with a modular storage units say just like rain water, soak waste then tap and wrap package for self installation for low risk areas like that. And then third one is especially used for storm water system silt traps. So, here we intercept to the silt and the small objects from water drainage systems then situated upstream of the modular water storage units. So, that is say what how we can use silt traps. Then vortex flow controls so, this is used with the storm water attenuation system to ensure continue to ensure optimum designated water flow rates at discharge outlet by utilizing an internal vortex makes them more efficient. So, like that same available same from rain water or storm water as a surface water source we can give appropriate treatments and that recycled water we can use for the particular use like either domestic or the agricultural or other industrial purposes. Then now second one is drainage and wastewater management. So, here say the water say which we are draining that we are trying to use effectively. So, we can have pumping stations say for example, for small applications like in packaged tank and pump systems designed to lift small quantities of wastewater to reach existing drain or sewer. Then we can have pumping stations say for example, for large applications like a packaged chamber and pump systems to lift large quantities of wastewater to reach existing drain or sewer. Then sewage treatment plants like designed for use where safety tank is either impractical and a connection to the main sewer is impossible. Then we can have systems like a grease traps and separators were primarily used in catering and commercial premises then to prevent vast amounts of grease and animal fats and oils from entering and solidifying in the drainage systems. So, what we are trying to say these are various systems which we can use say as a drainage water. So, the drained water we can directly say after through this treatment we can use for as a various purposes say recycled water. And then third solution is polluted water management solution. So, here say we are we are we can have bypass separators like designed to intercept oil petrol and silt from lightly contaminated surface water drainage systems. And then like a full retention separators saying like to intercepts oil, petrol, silt from heavily contaminated surface water drainage systems in high risk areas. Then treating the full flow that can be generated from the catchment area through the drainage systems. So, like that what we are trying to. So, here say somewhat polluted water say we give say various type of treatments and then recycle or we are planning to use for particular purpose depending upon the quality of the water. And then finally, say fourth one is the water recycling management solutions. So, this is what is actually we will be discussing in detail. So, here the grey water this is actually the grey water recovery systems say for domestic or industrial or commercial applications. So, here we can use the recycled water same in combination with rainwater harvesting say as far as domestic applications are concerned. And then we can capture, treat and store lightly soiled water used within a drilling in a residential area or we can reuse the around the house for supplying water to flush toilets, wash clothes or water say the garden. So, like that we can use the grey water recovery systems say for domestic applications. And then as next one is grey water recovery systems for industrial and commercial applications. So, here same the recycle water is used in combination with rainwater harvesting also. We can capture, treat and store lightly soiled water. So, that we can give with some mild treatments we can use for the intended purpose. Then we have reused for supplying water to flush toilets, wash clothes or water fields then a sports grounds or gardens like that. So, that way we can have either the domestic applications, industrial applications and commercial applications. So, only as I mentioned earlier depending upon the quality of the water waste water we give appropriate treatment and that recycle water is used for either domestic, industrial or commercial or agricultural applications. So, that way when we look into water recycling say we can say go for say different types of treatments and then according to the treatments we can use for particular type of use. So, if we are having the waste water. So, first one is we have to collect the waste water and then we can give some preliminary treatment like a soiled waste, soiled flotis flots all these things we can remove. And then next one is primary treatment. So, there say like sedimentation we can retain the water form sometime in say tanks or pits like that. So, that the floating materials and other things will be settled down. So, this is so called sedimentation process. So, actually this is simple treatment is not sufficient for any kind of reuse if the water is totally polluted then we have to go for further treatment. But if it is simple say water coming from a kitchen or like that then even after primary treatment we can use the recycled water form say in gardening or irrigation purpose. Then from the primary treatment the water is going to secondary treatment. So, there we can go for various treatments like biological oxidation or disinfection kind of treatment. So, actually after secondary treatment we can use the recycled water form various purposes like surface irrigation say for example, non food crop then say restricted landscape. So, we can use the water form say to get grass or the landscaping then it can be put to wetlands where further kinds of treatment will be taking place and then wildlife habitats then stream augmentation then say depending upon the quality of the water we can go for industrial cooling so like that. So, this is about the secondary treatment. So, after the secondary treatment the water can be sent to the tertiary or advanced treatment there we will be giving detailed treatment with respect to the chemical say like chemical coagulation filtration disinfection like that. So, actually the water coming from after this treatment is somewhat pure water to certain extent. So, this water we can use for say landscape golf course irrigation then toilet freshing, vehicle washing, food crop irrigation, unrestricted recreation environment. So, like that we can use this water for various purposes. And then if you are going to use the recycled water form say drinking or potable purposes then we can say how somewhat treatment like say reverse osmosis kinds of treatment or the ultraviolet disinfection treatment. And this water say so directly say using for potable we can use for groundwater recharge and then surface water reservoir augmentation like that. So, like this when we are looking to the wastewater say for as far as water recycling is concerned we have to go through a say systematic treatment depending upon the nature of the wastewater and depending upon the use for which we are going to put this recycled water. So, accordingly appropriate treatment will be given and will be reused. So, now further let us discuss somewhat in detail about this various stages of wastewater treatment say for recycling purposes. So, as I mentioned earlier depending upon the wastewater nature we can give appropriate treatments before recycling. So, first one is the preliminary treatment. So, there say we can remove the heavy solids like wood, rags and grit etcetera. So, this we can put the wastewater we can pass the water through wrinkling wastewater through a screen with bars of 20 to 50 m apart. So, that all the wood rags etcetera will be captured. So, that is so called preliminary treatment. Then the water will be sent to primary treatment. So, here we will slow the wastewater flow rate and settlement chambers or sedimentation tanks we can use. So, in domestic situation septic tank can be used as a settlement chamber then which may remove about 30 to 50 percent of the BOD and suspended solid. So, primary treatment to set next entry we can remove say most of the floating materials sediments and all those kinds of things and even some of the BOD also we can remove through primary treatment. Then next one is the secondary treatment. So, here we can go for various kinds of treatments like biological treatment say for example, to remove the microorganisms and removes the remaining BOD and suspended solids. So, here during later stages of secondary treatment the nitrification processes like an ammonia present in wastewater is transformed into nitrate. So, like that we can go for a series of secondary treatments and as we have seen in the previous slide this after secondary treatments the water may be used for purposes like reaction or say golf course reaction or landscaping like that. Then terrestrial treatment is actually this involves taking the wastewater through a further biological, physical or chemical step. So, here further we try to remove the BOD suspended solids, nitrogen, phosphorus and pathogens in the terrestrial treatment. So, we can also provide say like natural systems like wetlands or ponds and lagoons and then where say if land is available. So, that will be say the water will be detained for long time and then either aerobic or anaerobic kinds of say treatment will be taking place in these kinds of systems. So, that is about the terrestrial treatment. So, when we look in the terrestrial treatment actually say when we look in the wastewater through to after the terrestrial treatments the water can be used for various purposes say reuse is concerned or recycle after the recycling through the terrestrial treatment. We can directly utilize like for irrigation then say a toilet flushing or direct industrial purpose like that. So, terrestrial treatment for industrial reuse is usually done by using mechanized or physico chemical processes such as say some of the important terrestrial treatments I have listed here like activated carbon treatment. So, we can pass through pass the secondary treated wastewater through activated carbon. So, that most of the contaminants will be removed then chemical oxidation and other advanced oxidation processes then multimedia filtration and softening like lime soda adding lime soda passing through CO light. So, this is actually mainly for industrial purpose then on demineralization say like ion exchange processes then disinfection like by adding chlorine, hyperchlorine, ozone or ultraviolet systems or then we can put the waste the wastewater through for membrane processes like micro filtration, ultra filtration and then the latest is the reverse osmosis. So, depending upon the type of use so, we can choose particular type of terrestrial treatments and then directly from that treatment we can use the water or we can recycle the water. So, that way when we look into the tertiary treatments so, we can classify the treatment method into the biological methods and physico chemical method. As far as physico chemical method is concerned like screen, git removal, sedimentation, filtration etcetera. So, these are all physico chemical methods then biological method is concerned we can consider the treatment within the presence of oxygen or so, called aerobic methods and then anaerobic methods so, say without oxygen. So, that way some of the anaerobic methods include contact birds, sludge digesters etcetera. Then aerobic methods say we can again classify into suspended growth or attached growth. So, suspended growth say systems like activated sludge digest, aerated lagoons etcetera we can utilize. Then same the attached growth is concerned we can go for trickling filter, land treatment etcetera. So, when we discuss the terrestrial treatments we have a series of treatment methodologies number of methodologies are available so, depending upon the type of waste water or depending upon the quality of the components of the waste water. We choose particular type of treatments and then that also depends upon the intended reuse. So, what kind of whether we are going to use the recycled water for say domestic purposes or industrial purposes or agricultural purposes. So, accordingly we can choose particular type of treatment systems so, that say we have to see that the the economics also I mean the benefit cost ratio also we have to see when we say put the waste water through such treatment. So, now let us look into some of the important methods of treating the waste water. So, the waste water treatment is concerned we can classify into a conventional way of treating waste water and then modern techniques as far as waste water treatment is concerned. So, some of the treatment techniques are briefly mentioned here. First one is say cesspools. So, this is mainly we are using for containment say it is generally decentralized way of treatment. So, a cesspool is a big tank of at least 18 cubic meter size it has an inlet, but no outlet. So, we do not treat waste water here, but store it until it is removed by a such tanker so, that it will be taken for further treatment some other locations. So, it is a temporary storage. So, due to the environmental pollution especially to groundwater so, it is not prepared in urban environment. So, say we have to we should keep the waste water in a in a very good container otherwise if it is leaked into the soil then the groundwater will be affected. And then second one is safety tanks. So, actually this is a primary treatment and it can be also decentralized. So, safety tanks have we have both an inlet and outlet and this is much smaller and suitable for small scale waste water treatment and that can be adopted for domestic say like a household purpose or the housing societies or hotels like that and this provide primary treatment and should be followed by a shock pit or leach field. So, that one more treatment is required. So, safety tank is also a conventional way of treating the waste water. Then third one is leach fields or actually this can be secondary or tertiary and dispersal or it can be also centralized system or decentralized system. So, here same it is generally a last stage of a conventional treatment system. So, this is preceded by safety tank and this combination is often referred to as safety tank system. So, a leach field is a series of perforated pipes surrounded by gravity that run in underground trenches. So, this through this say we get to somewhat treated wastewater and then the next one is waste stabilization ponds. So, this can be all stages possible like a secondary tertiary then it can be either centralized system or decentralized system. So, like a solar ponds, settlement ponds, lagoons or sewage ponds with a small anaerobic ponds in the beginning followed by large aerobic ponds. So, the waste water go through a series of ponds and then finally, we will be getting somewhat treated water. So, this say generally this kinds of stabilization ponds will be placed in tandem with reed birds. So, that making system more attractive and larger. So, in the one of the limitations we need larger surface area to have this kinds of waste stabilization ponds. Then the other kinds of say the conventional treatment include like constructed wetlands. So, this also can be centralized or decentralized systems. So, constructed wetlands actually this is a human made wetland designed to closely imitate the treatment functions that occur in a natural wetlands. So, just like what is happening within an ecosystem. So, there will be some specific type of plants will be there in the system that absorb minimum the contaminants within the waste water and then the water will be detained, the waste water will be detained for some time and that will be going through a natural processes. And then this will be operating on in an ambient solar energy and to care a low external energy input. So, that way the waste water will be passing through the system for some time and then the we will be getting somewhat treated water. And then other conventional techniques like duck weed ponds. So, this can be also centralized or decentralized system. So, this is some green colored small plants which grows in sewage for holding ponds. So, this is this plants will be absorbing all this some of the waste material within the water and then that will become a feed for the plants. So, this feed on the organic elements in the waste water for growth for the treatment of low strength community waste water this can be used. And duck weeds help in removing nutrients and heavy metals by absorbing components like nitrogen, phosphorous, sulphur and tracer trace elements like that. So, this is another conventional treatment technique as far as water recycling is consensual. Then another one is so called trickling filter. So, this is actually used for secondary or tertiary treatment. So, trickling filters are always preceded by a primary settlement storage usually a septic tank and followed by a humus tank and they are also known as percolating filters, biological filter and filter buds. Then a trickling filter is a container usually filled with blast furnace clinger or stones called as media and then the waste water will be passing through that and then many of the waste material will be absorbed. Sewage is distributed over the surface of the media and drains freely to the base. The method is relatively robust tolerant of peak loadings and does not require power if a fall is available. So, that way this trickling filter is one of the best conventional way of treating the waste water and that treated waste water can be recycled or can be used as a recycled water for say various purposes like agriculture. Then say let us now look into some of the modern techniques used for treating the waste water. So, this is mainly say we use say as tertiary treatment. So, first one is the upflow anaerobic sludge blanket reactor or UASBR. So, here treatment plants say we can say actually as module it will be available directly it can be obtained from the shops and can be assembled. A sludge blanket cultured in the lower portion of the UASBR very effective traps suspended and dissolved organic matter. Then we can have rotating biodiscondacter say second unit in the series and takes the atmospheric oxygen and then an attached growth anoxic reactor is built into the upper portion of the UASBR for conversion of nitrates and nitrates into nitrogen gas. And then end-air operation is operation is simple and system once stabilized can be left to itself without much human intervention. So, once it is stabilized we have to only pass the waste water through the system and then the system will be keep on working. So, treated water may be used in say it will be somewhat good quality water say water. So, that can be used for irrigation purpose depending upon the nature of the waste water. So, that is about the UASBR. Then another one is another modern technique is called cyclic activated sludge process or SEATEC. So, here say the cyclic activated wastewater treatment process actually we pass through the water through activated carbon. So, carbon oxidation, nitrification, denitrification, biophosphorous removal all are carried out simultaneously as far as that SEATEC is concerned. And this technique ensures that all the effluent process like equalization, aeration, settling and decanning carried out in a single time. So, this is a very systematic modern system. So, where we can directly get better quality water. And then this treats the effluent level specified by authorities for irrigation or discharge into open water sources like rivers. So, through the cyclic activated carbon process we can achieve say the BOD can be less than 30 milligram per litre, COD can be less than 150 milligram per litre and ammonium nitrate can be less than 5 milligram per litre like that. So, like that we can achieve say better quality water through when the wastewater is going through the SEATEC technique. So, the technology is automatic and found to be very economical. So, for small scale industries this technique is very useful for the treatment of the wastewater. So, that way we can see that say the SEATEC or the USB are so like that this kind of modern techniques are very effective and then it occupies much much smaller space and then for a small industrial unit in an area we can directly they can buy it and put it in operation mode. And then as far as the modern techniques are concerned most important technique is so called a membrane processes. So, here we will be passing the wastewater through the membranes and then that will be capturing most of the the contaminants within the wastewater. So, that we will get a better quality water. So, the membrane process actually the membranes are semi permeable material designed to separate particulate colloidal and dissolved substances from liquid solutes or the wastewater. Then these membranes allows substances smaller than the membranes posed to flow through while holding back substances larger than the pores. So, depending upon the requirement we can have say microfilters or nanofilters like that. So, membranes produced from a variety of materials we can use for such purposes like cellulose acetate and polyamides then polysulfones and then polypropylene nylon polyvinyl alcohol etcetera. So, various kinds of membranes are available nowadays in market. So, the four most common configurations are like we can keep the configuration tubular form, plate and frame, spiral wound and hollow fiber. So, like that depending upon what kind of design we are doing as far as the membrane processor consent and depending upon the type of membrane and we can have the particular system. So, as far as the membrane processor consent actually we can classify this into four categories. The first one is the micro filtration. So, this categorization is according to the size of the membrane. So, micro filtration membranes actually pores will be greater than 50 nanometers are the least expensive membranes and this we can use in wastewater treatment for turbidity removal of solids separation after biological treatment and then this also can be we can use in membrane bioreactors and this can be used for removal of helmin over other organisms etcetera from the wastewater. So, micro filtration when the membrane pores are greater than for 50 nanometers. So, that kind of membrane when we use that is called micro filtration. Second one is so called ultrafiltration. So, ultrafiltration means the ultrafiltration membranes the pore size will be varying from 2 to 50 nano microns or nanometer 50 nanometer have been used in wastewater treatment for many of the same applications as micro filter membranes except that ultrafiltration scheme systems will give a better separation of final colloids bacteria virus etcetera. So, when the wastewater is passed through the ultrafiltration system. So, other than the colloids and the sediments all these things we can also remove the bacteria viruses etcetera from the wastewater. So, this water available from the ultrafiltration will be much better than what is from the micro filtration. And the third system is so called nano filtration. So, here in nano filtration membranes the pores should be less than 2 nanometers. So, the pressure the pressures vary between 522 1400 kilo Pascal and flux rates vary from 200 to 800 liters per meter square per day. And this the water passing through the nano filtration we can directly use for even 4 portable purposes like recharging or other kinds of purposes. Then the ultimate say filter technique is by using the technique is called reverse osmosis. So, here the membranes pores will be much smaller than 2 nanometer and have the lowest molecular weight cut off and then high operating pressures of more than 1400 kilo Pascal. And flux rates vary from 300 to 500 liters per meter square per day. So, this is say actually even say we are reverse osmosis one of the commonly used technique say as far as the desalination plans are concerned. And the reverse osmosis in further treating pre-treated say from micro filtration or ultrafiltration to produce waters of high quality for indirect reuse applications. So, even say for example, if the water is not available in particular we can the the water passing through reverse osmosis systems we can directly even utilize or we can use for the the the recharge to the aquifer systems like that. And then one more say modern techniques like ultra virus disinfection. So, where we can remove all the the pathogen bacteria viruses etcetera from the the the recycled water and then directly we can use for the intended use. So, like this we can see that say depending upon the the use what we are considering. So, depending upon the quality of the the wastewater we go for a particular type of say treatments and then we can directly say use for the intended use depending upon the treatments given. So, before closing today's lecture let us say have an overview of the water recycling practices. So, water recycling is a growing practice in many regions of the world including USA, Europe, India, Australia, Israel etcetera. So, especially in countries like a Israel, Australia where water scarcity is there they they this water recycling is very common in many of the areas. Say as far as US is concerned about 13 million meter cube per day is recycled and reused and a small fraction of total volume wastewater generally actually this is small fraction. Out of the 140 million meter cube per day only about 10 percent of waste water is recycled and suggesting the potential of recycling and recycled water use on a volume basis is growing at an estimated 15 percent per year in the United States. And all evidence suggests that water recycling will play major role in the water management in the 21st century. So, this water recycling practices are increasing in many of their especially industries concerned they are looking for zero liquid discharge that means no waste water from the the system. So, that way say many of the industries are now adopting the water recycling. In the United States for example, at a compound annual growth rate of 15 percent the volume of recycled water would be about 45 to 15 million meter cube per day in another 5 to 10 years. So, like that the system is growing and the water recycling is becoming very common. As far as water recycling in India is concerned say in India not much recycling is done but now industries are being especially industry sector the recycling is coming up like anything. So, in India some of the methodology is adopted as far as recycling is concerned water recycling is concerned like a plain water conservation reuse without any treatments reuse after treatment using on-site toilet waters and some easily treated industrial waste waters then reuse after treatment using off-site sources of municipal waste water. Then say study of the reuse of waste water in India shows that the reuse has achieved in affordable cost and some industries have in fact saved the money by reusing their waste water. So, many examples are there say where the money is the whatever the money invested say in waste water treatment or water recycling they have got back in previous time and then they are saving money as far as water recycling and reuse is concerned. So, in India the water recycling has first begun say in Mumbai say in 1964 and 65 especially by textile industry and that time water gravity was much less to Mumbai region. So, that way the textile industry started this showing that about 15 to 20 percent of the water can be recycled without any pre-treatment especially in textile industries. And cost of providing direct reuse was relatively small then cost-benefit ratio is high and cost recovery periods is say within 2 or 3 years. Then the recycling was carried out in as many as 22 mils in 70s and 80s in Mumbai and later a few more industries started recycling. A typical treatment scheme say for example say if you consider toilet water is as follows the wastewater so first it will be screened then extended aeration will be given chemical dosing plus flocculation will be done then sand defiltration then CO8 softening plus acid correction occasional chlorine shock dose then make a water say for example using for cooling towers. So, then remaining sludge and other wastewater will be returned to sewer line. So, like that it will be going through a systematic process depending upon the wastewater and then depending upon the intended use. So, now before closing today's lecture let us discuss two small cases where the water recycling is practiced for last few years in Mumbai say for example first industries Oswald, Agro, Union Garbet plant, Chambur, Mumbai. So, here they have given terrestrial treatment this is built up this is actually a very old plant say about 10 same 40 years say actually this plant is there. So, for sewer treatment reclamation with capacity 5 to 10 million liters per day raw sewage was obtained from municipal corporation as far as this industry is concerned and so being using the wastewater from municipal corporation which is a dependable source of water. A treated water used for cooling say used for cooling purposes and treatment scheming would say the wastewater coming from the municipal or the sewage water then it will be passing through screening then grit removal will be done then extended aeration is given then chemical dosing plus flocculation so that all the sediment or the suspended solids will be removed then sand filtration is given then COH it will be passed through COH so that softening is done and plus acid correction and occasional chlorine shock dose are given and then this water is directly used for cooling purposes. Then another example is rasteric chemical fertilizers RC of Chambur, Mumbai. So, actually this plant was installed in 2000 for recycling about 23 million liters per day and the investment was about 400 millions rupees and a complicated treatment process including reverse osmosis is installed in the RC of Plant. 2005 the operating cost was about rupees 39 per meter cube with the success of recycling scheme municipality also started to charge this wastewater so the wastewater to the RC was taken from the municipal supply and the plant in the RC was the following floor sheets like wastewater will be taken from municipal supply waste to sewage then it will be put through screening then grit removal then activated storage system clarifier then sand filter then pressure filter then cartridge filter then it will be passed through reverse osmosis and then a degas to remove carbon dioxide and finally this is used in industry. So that way RCF this last say 10-15 years they are very effectively using this municipal sewage wastewater the sewage for their water supply in the RC of Plant. So now before closing the lecture let us look at the future of water recycling. So water recycling has proven to be effective and successful in creating new and reliable water supply then non portable reuse is widely accepted and advances in wastewater treatment technology and health studies may be for portable purpose also we can use recycling what waste and grey water requires less energy than treating salt water like a desalination system then water recycling is a sustainable approach and can be cost effective in the long term then public be informed and involved in the planning processes. So before closing today's lecture so these are some of the references used for today's lecture then few questions total questions critically analyzed and study the scope of water recycling in India whether water recycling and reuse a solution for water scarcity in India study and compare various case studies available and evaluate the economics. Then self evaluation questions illustrate water recycling and its importance what are the benefits of water recycling and what are the different stages of wastewater treatment illustrate various conventional ways of treating the wastewater then a few assignment questions like discuss various uses of recycled water describe various water management solutions describe the various stages of terrestrial treatment methods illustrate various modern ways of treating wastewater. So today we are discussing about the the water recycling so we are discussing about the how we can use the wastewater for various purposes by giving appropriate treatments depending upon the wastewater nature of the wastewater we have to be appropriate treatment for the intended use. So in the last lecture in the next lecture we will be discussing about the water reuse and further reclamation and further topics in this module. Thank you.