Rainwater harvesting

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Rainwater harvesting

  1. 1. 1APROJECT REPORTON“Rain water harvesting”Submitted in Partial Fulfillment for the Award ofBachelor of Technology DegreeOfRajasthan Technical University, KOTASession- 2012-2013From 04/02/12 to 04/03/13Session: - 2012-2013Submitted To: Submitted By(LACTURAR) Deep chaudharyDEPARTMENT OF CIVIL ENGG.ChittaranjanSunil kaswanAshishprajapatVIVEKANANDA INSTITUTE OF TECHNOLOGY (EAST)JAGATPURA, JAIPUR-302025(RAJASTHAN)
  2. 2. 2PREFACEThe main aim of our project was to put our knowledge intopractical use. This project has given us the experience to work in theactual field and it also teaches us to overcome the practical situationfaced in real life and to interact with people, keeping ourselves calmand patience in cases of difficulty.This project report is a brief description about our work doneunder the guidance of MR. NARAYAN MEGHNANIIt consists of thevarious departments that we’ve visited and the various tasks thatwe’ve done over there.We would like to say that this project has helped to shape thepractical knowledge that as a person we have inside us and it wouldalso help me throughout our life and for this we are very thankful toall the persons who helped us during our project period.Thanking you
  3. 3. 3ACKNOWLEDGEMENTAt the outset, we thank God almighty for making our endeavor a success. We also express ourgratitude to PROF. NarayanMeghnani(Head of the Department),Civil Engineering for providing uswith adequate facilities, ways and means by which we were able to complete this project.We express our sincere gratitude to our project Guide MR. AnandMathur (H.O.D.), CivilEngineering for his constant support and valuable suggestions without which the successfulcompletion of this project would not have been possible.We express our immense pleasure and thanks to all the teachers and staff of theDepartment of Civil Engineering, Last but not the least, we thank all others, and especially ourclassmates and our family members who in one way or another helped in the successful completion ofthis work.ALL GROUP MEMBERS
  4. 4. 4ABSTRACTAt the rate in which India population is increasing, it is said that India will surely replace China fromits number 1 position of most densely populated country of the world after 20-30. These will lead tohigh rate of consumption of most valuable natural resource „Water‟ is resulting in augmentation ofpressures on the permitted freshwater resources. Ancient method of damming river and transportingwater to urban area has its own issues of eternal troubles of social and political. In order to conserveand meet our daily demand of water requirement, we need to think for alternative cost effective andrelatively easier technological methods of conserving water. Rain water harvesting is one of the bestmethods fulfilling those requirements. The technical aspects of this paper are rainwater harvestingcollected from rooftop which is considered to be catchment areas from all hostels and Institutesdepartmental building at V.I.T. Campus. First of all, required data are collected i.e. catchment areas &hydrological rainfall data. Water harvesting potential for the hostels and faculty apartments wascalculated, and the tank capacity with suitable design is being considered. Volume of tank has beencalculated with most appropriate method of estimation. Optimum location of tank on the basis ofhydrological analysis and GIS analysis was done in the campus. Finally, Gutter design, its analysis,first flush and filtration mechanism are also dealt with in detail.Keyword: Rainwater harvesting, first flush mechanism, Roof water system, Gutter for conveyance,Underground RCC tank, Methods of distribution of harvested rainwater.
  5. 5. 5CERTIFICATEIt is hereby certified that this is a bonfire record of the project report entitled “Rainwaterharvesting” has been completed by “DEEP CHAUDHARY, CHITTA RANJANMANDAL, SUNIL KASWAN, ASHISH PRAJAPAT” of the VIII semester, CIVILENGINEERING in the year 2013 in partial fulfillment of the requirements to the award ofDegree of Bachelor of Technology in CIVIL ENGINEERING from VIVEKANANDAINSTITUTE OF TECHNOLOGY(EAST) affiliated to Rajasthan Technical University,Kota.(H.O.D)Mr. AnandlalmathurDEPARTMENT OF CIVIL ENGINEERING
  6. 6. 6CONTENTSPage No.Abstract - 4Chapter - 1 Introduction 7-8Chapter -2 Harvesting systems and itsfeatures9-10Chapter -3 113.1. Studies Carried out Globally3.2. Studies carried out in IndiaChapter–4 12-16Data collectionChapter – 55.0. First flush systemChapter – 617-2728-296.1. Hydrological Analysis6.2. Methods for storage of harvestedrainwater in tankChapter – 7Types of tank and designChapter – 8Detail and costConclusion3137-40
  7. 7. 7Chapter.1IntroductionA sufficient, clean drinking water supply is essential to life. Millions of people throughout the world still do nothave access to this basic necessity. After decades of work by governments and organizations to bring potablewater to the poorer people of the world, the situation is still dire. The reasons are many and varied butgenerally speaking, the poor of the world cannot afford the capital intensive and technically complextraditional water supply systems which are widely promoted by governments and agencies throughout theworld. Rainwater harvesting (RWH) is an option that has been adopted in many areas of the world whereconventional water supply systems have failed to meet people’s needs. It is a technique that has been usedsince antiquity. It is worth bearing in mind that rainwater harvesting is not the definitive answer tohousehold water problems. There is a complex set of inter-related circumstances that have to beconsidered when choosing the appropriate water source. These include cost, climate, hydrology,social and political elements, as well as technology, all play a role in the eventual choice of watersupply scheme that is adopted for a given situation. RWH is only one possible choice, but one that isoften overlooked by planners, engineers and builders.The reason that RWH is rarely considered is often due to lack of information – both technical andotherwise. In many areas where RWH has been introduced as part of a wider drinking water supplyprogrammed it was at first unpopular, simply because little was known about the technology by thebeneficiaries. In most of these cases, the technology has quickly gained popularity as the userrealizes the benefits of a clean, reliable water source at the home. the town supply is unreliable orwhere local water sources dry up for a part of the year, but is also In many cases RWH has beenintroduced as part of an integrated water supply system, where often used as the sole water sourcefor a community or household. It is a technology that is flexible and adaptable to a very wide variety ofconditions, being used in the richest and the poorest societies on our planet, and in the wettest andthe driest regions of the world.Storage tanks and cisternsThe water storage tank usually represents the biggest capital investment element of a domestic RWH system.It therefore usually requires careful design – to provide optimal storage capacity while keeping the cost as lowas possible. The catchment area is usually the existing rooftop or occasionally a cleaned area of ground, asseen in the courtyard collection systems in China, and guttering can often be obtained relatively cheaply, orcan be manufactured locally.There are an almost unlimited number of options for storing water. Common vessels used for very small-scalewater storage in developing countries include such examples as plastic bowls and buckets, jerrycans, clay orceramic jars, cement jars, old oil drums, empty food containers, etc. For storing larger quantities of water thesystem will usually require a tank or a cistern. For the purpose of this document we will classify the tank as anabove-ground storage vessel and the cistern as a below-ground storage vessel. These can vary in size from acubic meter or so (1000 liters) up to hundreds of cubic meters for large projects, but typically up to a maximumof 20 or 30 cubic meters for a domestic system. The choice of system will depend on a number of technical andeconomic considerations listed below.1. Space availability2. Options available locally3. Local traditions for water storage4. Cost – of purchasing new tank5. Cost – of materials and labour for construction.
  8. 8. 8One of the main choices will be whether to use a tank or a cistern. Both tanks and cisterns have theiradvantages and disadvantages. Table 1 summarizes the pros and cons of each-:Tank CisternPros 1. Above ground structureallows easy inspectionfor leakages2. Many existing designs tochoose from3. Can be easily purchased‘off-the-shelf’4. Can be manufacturedfrom a wide variety ofmaterials5. Easy to construct fromtraditional materials6. Water extraction can beby gravity in many cases7. Can be raised aboveground level to increasewater pressure1. Generally cheaper dueto lower materialrequirements2. More difficult to emptyby leaving tap on3. Require little or nospace above ground4. Unobtrusive5. Surrounding groundgives support allowinglower wall thickness andthus lower costsCons1.Require space2.Generally more expensive3.More easily damaged4.Prone to attack fromweather5.Failure can be dangerous1.Water extraction is moreproblematic – often requiringa pump2.Leaks are more difficult todetect3.Contamination of thecistern from groundwater ismore common4.Tree roots can damagethe structure5.There is danger to childrenand small animals if thecistern is left uncovered
  9. 9. 9Chapter.22.1.RAINWATER HARVESTING SYSTEMS AND ITS FEATURES -Rainwater Harvesting is a simple technique of catching and holding rainwater where its falls. Either,we can store it in tanks or we can use it to recharge groundwater depending upon the situation.1.a. Features of Rainwater Harvesting are:1. Reduces urban flooding.2. Ease in constructing system in less time.3. Economically cheaper in construction compared to other sources, i.e. dams, diversion, etc.4. Rainwater harvesting is the ideal situation for those areas where there is inadequategroundwater supply or surface resources.5. Helps in utilizing the primary source of water and prevent the runoff from going into sewer orstorm drains, thereby reducing the load on treatment plants.6. Recharging water into the aquifers which help in improving the quality of existinggroundwater through dilution.2.2. COMPONENTS OF RAINWATER HARVESTING SYSTEM-A rainwater harvesting system comprises of components for - transporting rainwater through pipes ordrains, filtration, and tanks for storage of harvested water. The common components of a rainwaterharvesting system are:-1. Catchments: The surface which directly receives the rainfall and provides water to the system iscalled catchment area. It can be a paved area like a terrace or courtyard of a building, or an unpavedarea like a lawn or open ground. A roof made of reinforced cement concrete (RCC), galvanized ironor corrugated sheets can also be used for water harvesting.2. Coarse Mesh: It prevents the passage of debris, provided in the roof.3. Gutters: Channels which surrounds edge of a sloping roof to collect and transport rainwater to thestorage tank. Gutters can be semi-circular or rectangular and mostly made locally from plaingalvanized iron sheet. Gutters need to be supported so they do not sag or fall off whenloaded with water. The way in which gutters are fixed mainly depends on the construction of thehouse, mostly iron or timber brackets are fixed into the walls. The detail of the designing part of theGutter is done in 7.3.4. Conduits: Conduits are pipelines or drains that carry rainwater from the catchment or rooftop areato the harvesting system. Commonly available conduits are made up of material like polyvinylchloride (PVC) or galvanized iron (GI).
  10. 10. 105. First-flushing: A first flush device is a valve which ensures flushing out of first spell of rain awayfrom the storage tank that carries a relatively larger amount of pollutants from the air and catchmentsurface.6. Filters: The filter is used to remove suspended pollutants from rainwater collected from rooftopwater. The Various types of filters generally used for commercial purpose are Charcoal water filter,Sand filters, Horizontal roughing filter and slow sand filter.7. Storage facility: There are various options available for the construction of these tanks withrespect to the shape, size, material of construction and the position of tank and they are:-8. Shape: Cylindrical, square and rectangular.9. Material of construction: Reinforced cement concrete (RCC), masonry, Ferro cement etc.10. Position of tank: Depending on land space availability these tanks could be constructedabove ground, partly underground or fully underground. Some maintenance measures likedisinfection and cleaning are required to ensure the quality of water stored in the container.If harvested water is decided to recharge the underground aquifer/reservoir, then some of thestructures mentioned below are used.11. Recharge structures: Rainwater Harvested can also be used for charging the groundwateraquifers through suitable structures like dugwells, borewells, recharge trenches and recharge pits.Various recharge structures are possible some which promote the percolation of water through soilstrata at shallower depth (e.g., recharge trenches, permeable pavements) whereas others conduct waterto greater depths from where it joins the groundwater (e.g. recharge wells). At many locations,existing structures like wells, pits and tanks can be modified as recharge structures, eliminating theneed to construct any fresh structures. Some of the few commonly used recharging methods arerecharging of dug wells and abandoned tube wells, Settlement tank, Recharging of service tube wells,Recharge pits, Soak ways Percolation pit , Recharge troughs, Recharge trenches, Modified injectionwell.
  11. 11. 11Chapter.33.1. STUDIES CARRIED OUT GLOBALLY-Today due to rising population &economical growth rate, demands for the surface water isincreasing exponentially. Rainwater harvesting is seems to be a perfect replacement for surface &ground water as later is concerned with the rising cost as well as ecological problems. Thus,rainwater harvesting is a cost effective and relatively lesser complex way of managing our limitedresources ensuring sustained long-term supply of water to the community. In order to fight withthe water scarcity, many countries started harvesting rain. Major players are Germany (Biggestharvesting system in Germany is at Frankfurt Airport, collecting water from roofs of the newterminal which has an large catchment area of 26,800 m2), Singapore (as average annual rainfallof Singapore is 2400 mm, which is very high and best suited for rainwater harvestingapplication), Tokyo (as RWH system reserves water which can be utilized for emergency waterdemands for seismic disaster), etc.3.2.STUDIES CARRIED OUT IN INDIA -Today, only 2.5 per cent of the entire world’s water is fresh, which is fit for human consumption,agriculture and industry. In several parts of the world, however, water is being used at a muchfaster rate than can be refilled by rainfall. In 2025, the per capita water availability in India willbe reduced to 1500 cubic meters from 5000 in 1950. The United Nations warns that this shortageof freshwater could be the most serious obstacle to producing enough food for a growing worldpopulation, reducing poverty and protecting the environment. Hence the water scarcity is going tobe a critical problem if it is not treated now in its peanut stage.Chapter.4
  12. 12. 12DATA COLLECTION-1. RAINFALL DATA COLLECTION –Jaipur is located at westlongitude directionin Rajasthan.Jaipurhas a hot climate and not receiveshigh rainfall during Southwest monsoon (June-September) and retreating Northeast monsoon(December-January). Average annual rainfall ranges between 50-80 cm.TABLE NO.1: MONTHLY RAINFALL DATA OF ROURKELA STATIONMonth Rainfall (mm)January 10February 24.9March 0April 0May 0June 10July 20August 15September 20October 0November 0December 15TOTAL 114.9
  13. 13. 13The case studies later in this document show a variety of tanks that have been built in different partsof the world. In jaipur -Collection surfacesFor domestic rainwater harvesting the most common surface for collection is the roof of the dwelling. Manyother surfaces can be, and are, used: courtyards, threshing areas, paved walking areas, plastic sheeting, trees,etc. In some cases, as in Gibraltar, large rock surfaces are used to collect water which is then stored in largetanks at the base of the rock slopes.Most dwellings, however, have a roof. The style, construction and material of the roof affect its suitability as acollection surface for water. Typical materials for roofing include corrugated iron sheet, asbestos sheet; tiles (awide variety is found), slate, and thatch (from a variety of organic materials). Most are suitable for collection ofroof water, but only certain types of grasses e.g. coconut and anahaw palm (Gould and Nissen Peterson, 1999),thatched tightly, provide a surface adequate for high quality water collection. The rapid move towards the useof corrugated iron sheets in many developing countries favors the promotion of RWH (despite the othernegative attributes of this material).GutteringGuttering is used to transport rainwater from the roof to the storage vessel. Guttering comes in a wide varietyof shapes and forms, ranging from the factory made PVC type to home made guttering using bamboo or folded
  14. 14. 14metal sheet. In fact, the lack of standards in guttering shape and size makes it difficult for designers to developstandard solutions to, say, filtration and first flush devices. Guttering is usually fixed to the building just belowthe roof and catches the water as it falls from the roof.Figure 4: A typical corrugated iron sheet roof showing gutteringSome of the common types of guttering and fixings are shown in figure 5.
  15. 15. 15Manufacture of low-cost gutters –Factory made gutters are usually expensive and beyond the reach of the poor ofdeveloping countries, if indeed available at all in the local marketplace. They are seldomused for very low-cost systems. The alternative is usually to manufacture gutters frommaterials that can be found cheaply in the locality. There are a number of techniques thathave been developed to help meet this demand; one such technique is described below.V- shaped gutters from galvanized steel sheet can be made simply by cutting and foldingflat galvanized steel sheet. Such sheet is readily available in most market centers(otherwise corrugated iron sheet can be beaten flat) and can be worked with tools that arecommonly found in a modestly equipped workshop. One simple technique is to clamp thecut sheet between two lengths of straight timber and then to fold the sheet along the edgeof the wood. A strengthening edge can be added by folding the sheet through 90oand thencompleting the edge with a hammer on a hard flat surface. The better the grade of steelsheet that is used, the more durable and hard wearing the product. Fitting a downpipe toV-shaped guttering can be problematic and the V-shaped guttering will often be continuedto the tank rather than changing to the customary circular pipe section downpipe. Methodsfor fixing gutters are shown in figure 5.
  16. 16. 16Chapter.5First flush systemsDebris, dirt, dust and droppings will collect on the roof of a building or other collection area. When the firstrains arrive, this unwanted matter will be washed into the tank. This will cause contamination of the water andthe quality will be reduced. Many RWH systems therefore incorporate a system for diverting this ‘first flush’water so that it does not enter the tank.The simpler ideas are based on a manually operated arrangement whereby the inlet pipe is moved away fromthe tank inlet and then replaced again once the initial first flush has been diverted. This method has obviousdrawbacks in that there has to be a person present who will remember to move the pipe.Other systems use tipping gutters to achieve the same purpose. The most common system (as shown in Figure7a) uses a bucket which accepts the first flush and the weight of this water off-balances a tipping gutter whichthen diverts the water back into the tank.The bucket then empties slowly through a small-bore pipe and automatically resets. The process will repeatitself from time to time if the rain continues to fall, which can be a problem where water is really at apremium. In this case a tap can be fitted to the bucket and will be operated manually. The quantity of waterthat is flushed is dependent on the force required to lift the guttering. This can be adjusted to suit the needs ofthe user.Figure 7 – a) the tipping gutter first flush system and b) the floating ball first flush system.
  17. 17. 17Another system that is used relies on a floating ball that forms a seal once sufficient water has been diverted(see Figure 7b). The seal is usually made as the ball rises into the apex of an inverted cone. The ball seals thetop of the ‘waste’ water chamber and the diverted water is slowly released, as with the bucket system above,through a small bore pipe. Again, the alternative is to use a tap. In some systems (notably one factorymanufactured system from Australia) the top receiving chamber is designed such that a vortex is formed andany particles in the water are drawn down into the base of the vortex while only clean water passes into thestorage tank. The ‘waste’ water can be used for irrigating garden plants or other suitable application. Thedebris has to be removed from the lower chamber occasionally.Although the more sophisticated methods provide a much more elegant means of rejecting the first flushwater, practitioners often recommend that very simple, easily maintained systems be used, as these are morelikely to be repaired if failure occurs.Filtration systems and settling tanksAgain, there are a wide variety of systems available for treating water before, during and after storage. Thelevel of sophistication also varies, from extremely high-tech to very rudimentary. A German company, WISY,have developed an ingenious filter which fits into a vertical downpipe and acts as both filter and first-flushsystem. The filter, shown in Figure 8, cleverly takes in water through a very fine (~0.20mm) mesh whileallowing silt and debris to continue down the pipe. The efficiency of the filter is over 90%. This filter iscommonly used in European systems.The simple trash rack has been used in some systems but this type of filter has a number of associatedproblems: firstly it only removes large debris; and secondly the rack can become clogged easily and requiresregular cleaning.The sand-charcoal-stone filter is often used for filtering rainwater entering a tank. This type of filter is onlysuitable, however, where the inflow is slow to moderate, and will soon overflow if the inflow exceeds the rateat which the water can percolate through the sand. Settling tanks and partitions can be used to remove siltand other suspended solids from the water. These are usually effective where used, but add significantadditional cost if elaborate techniques are used. Many systems found in the field rely simply on a piece of clothor fine mosquito mesh to act as the filter (and to prevent mosquitoes entering the tank).Post storage filtration include such systems as the up flow sand filter or the twin compartment candle filterscommonly found in LDC’s. Many other systems exist and can be found in the appropriate water literature.
  18. 18. 18Figure 8: the WISY filter (downpipe and high-capacity below ground versions) - Source: WISY Catalogue
  19. 19. 19Sizing the systemUsually, the main calculation carried out by the designer when planning a domestic RWH system will be to sizethe water tank correctly to give adequate storage capacity. The storage requirement will be determined by anumber of interrelated factors. They include:1. local rainfall data and weather patterns2. size of roof (or other) collection area3. runoff coefficient (this varies between 0.5 and 0.9 depending on roof material and slope)4. user numbers and consumption ratesThe style of rainwater harvesting i.e. whether the system will provide total or partial supply (see the nextsection) will also play a part in determining the system components and their size.There are a number of different methods used for sizing the tank. These methods vary in complexity andsophistication. Some are readily carried out by relatively inexperienced, first-time practitioners while othersrequire computer software and trained engineers who understand how to use this software. The choice ofmethod used to design system components will depend largely on the following factors:1. the size and sophistication of the system and its components2. the availability of the tools required for using a particular method (e.g. computers)3. the skill and education levels of the practitioner / designerBelow we will outline 3 different methods for sizing RWH system components.Method 1 – demand side approachA very simple method is to calculate the largest storage requirement based on the consumption rates andoccupancy of the building.As a simple example we can use the following typical data:Consumption per capita per day, C = 20 litersNumber of people per household, n = 6Longest average dry period = 25 daysAnnual consumption = C x n = 120 litersStorage requirement, T = 120 x 25 = 3,000 litersThis simple method assumes sufficient rainfall and catchment area, and is therefore only applicable in areaswhere this is the situation. It is a method for acquiring rough estimates of tank size.
  20. 20. 20Method 2 – supply side approachIn low rainfall areas or areas where the rainfall is of uneven distribution, more care has to be taken to size thestorage properly. During some months of the year, there may be an excess of water, while at other times therewill be a deficit. If there is enough water throughout the year to meet the demand, then sufficient storage willbe required to bridge the periods of scarcity. As storage is expensive, this should be done carefully to avoidunnecessary expense. This is a common scenario in many developing countries where monsoon or single wetseason climates prevail.The example given here is a simple spreadsheet calculation for a site in North Western Tanzania. The rainfallstatistics were gleaned from a nurse at the local hospital who had been keeping records for the previous 12years. Average figures for the rainfall data were used to simplify the calculation, and no reliability calculation isdone. This is a typical field approach to RWH storage sizing.The example is taken from a system built at a medical dispensary in the village of Ruganzu, Biharamulo District,Kagera, Tanzania in 1997.Rainwater harvesting Practical ActionDemand:Number of staff: 6Staff consumption: 25 lpcd*Patients: 30Patient consumption : 10 lpcdTotal daily demand: 450 litersSupply:Roof area: 190m2Runoff coefficient** (for new corrugated GIroof): 0.9Average annual rainfall: 1056mm per yearDaily available water (assuming all iscollected) = (190 x 1056 x 0.9)/ 365 = 494.7litersIn this case, it was decided to size the tank to suit the supply, assuming that there may be growth in numbersof patients or staff in the future. Careful water management will still be required to ensure water throughoutthe year.Demand:Number of staff: 6Staff consumption: 25 lpcd*Patients: 30Patient consumption : 10 lpcdTotal daily demand: 450 litersSupply:Roof area: 190m2Runoff coefficient** (for new corrugated GIroof): 0.9Average annual rainfall: 1056mm per yearDaily available water (assuming all is collected) =(190 x 1056 x 0.9)/ 365 = 494.7 liters
  21. 21. 21Figure 10 shows the comparison of water harvested and the amount that can be supplied to thedispensary using all the water which is harvested. It can be noted that there is a single rainy season.The first month that the rainfall on the roof meets the demand is October. If we therefore assume thatthe tank is empty at the end of September we can form a graph of cumulative harvested water andcumulative demand and from this we can calculate the maximum storage requirement for themdispensary.
  22. 22. 22Figure 10: Comparison of the harvestable water and the demand for each month-In this case the solution was a 50 cubic meterFerro cement tank-
  23. 23. 23Method 3 – computer modelThere are several computer-based program for calculating tank size quite accurately. One such program,known as sintex Tank, has been written by an Indian organization and is available free of charge on the WorldWide Web. The Ajit Foundation is a registered non-profit voluntary organization with its main office in Jaipur,India and its community resource center in Bikaner, India.User behaviour patterns with domestic RWHStyles of RWH – system, climate and geographical variablesRainwater that has been harvested is used in many different ways. In some parts of the world it is used merelyto capture enough water during a storm to save a trip or two to the main water source. Here, only smallstorage capacity is required, maybe just a few small pots to store enough water for a day or half a day. At theother end of the spectrum we see, in arid areas of the world, systems which have sufficient collection surfacearea and storage capacity to provide enough water to meet the full needs of the user. Between these twoextremes exists a wide variety of different user patterns or regimes. There are many variables that determinethese patterns of usage for RWH.Some of these are listed below:Rainfall quantity (mm/year)1. Rainfall pattern - The type of rainfall pattern, as well as the total rainfall, which prevails willoften determine the feasibility of a RWHS. A climate where rain falls regularly throughout theyear will mean that the storage requirement is low and hence the system cost will becorrespondingly low and vice versa. More detailed rainfall data is required to ascertain therainfall pattern. The more detailed the data available, the more accurately the systemparameters can be defined.2. Collection surface area (m2)3. Available storage capacity (m3)4. Daily consumption rate (liters/capita /day or lpcd)- this varies enormously – from 10 – 15 lpcda day in some parts of Africa to several hundred lpcd in some industrialized countries. Thiswill have obvious impacts on system specification.5. Number of users - again this will greatly influence the requirements.6. Cost– a major factor in any scheme.7. Alternative water sources– where alternative water sources are available, this can make asignificant difference to the usage pattern. If there is a groundwater source within walking
  24. 24. 24distance of the dwelling (say within a kilometer or so), then a RWHS that can provide a reliablesupply of water at the homestead for the majority of the year, will have a significant impact tolifestyle of the user. Obviously, the user will still have to cart water for the remainder of the year,but for the months when water is available at the dwelling there is a great saving in time andenergy. Another possible scenario is where rainwater is stored and used only for drinking andcooking, the higher quality water demands, and a poorer quality water source, which may be nearthe dwelling, is used for other activities.8. Water management strategy– whatever the conditions, a careful water management strategyis always a prudent measure. In situations where there is a strong reliance on storedrainwater, there is a need to control or manage the amount of water being used so that it doesnot dry up before expected.We can simply classify most systems by the amount of ‘water security’ or ‘reliability’ afforded by thesystem. There are four types of user regimes listed below:Occasional - water is collected occasionally with a small storage capacity, which allows the user tostore enough water for a maximum of, say, one or two days. This type of system is ideally suited to aclimate where there is a uniform, or bimodal, rainfall pattern with very few dry days during the yearand where an alternative water source is available nearby.Intermittent – this type of pattern is one where the requirements of the user are met for a part of theyear. A typical scenario is where there is a single long rainy season and, during this time, most or allof the users’ needs are met. During the dry season, an alternative water source has to be used or, aswe see in the Sri Lankan case, water is carted/ bowered in from a nearby river and stored in the RWHtank. Usually, a small or medium size storage vessel is required to bridge the days when there is norain.Partial – this type of pattern provides for partial coverage of the water requirements of the user duringthe whole of the year. An example of this type of system would be where a family gather rainwater tomeet only the high-quality needs, such as drinking or cooking, while other needs, such as bathing andclothes washing, are met by a water source with a lower quality.Full – with this type of system the total water demand of the user is met for the whole of the year byrainwater only. This is sometimes the only option available in areas where other sources areunavailable. A careful feasibility study must be carried out before hand to ensure that conditions aresuitable. A strict water management strategy is required when such a system is used to ensure thatthe water is used carefully and will last until the following wet season.Rainwater quality and healthRainwater is often used for drinking and cooking and so it is vital that the highest possible standards are met.Rainwater, unfortunately, often does not meet the World Health Organization (WHO) water quality guidelines.This does not mean that the water is unsafe to drink. Gould and Nissen-Peterson(1999), in their recent book,point out that the Australian government have given the all clear for the consumption of rainwater ‘providedthe rainwater is clear, has little taste or smell, and is from a well-maintained system’. It has been found that afavorable user perception of rainwater quality (not necessarily perfect water quality) makes an enormousdifference to the acceptance of RWH as a water supply option.Generally the chemical quality of rainwater will fall within the WHO guidelines and rarely presents problems.There are two main issues when looking at the quality and health aspects of DRWH:
  25. 25. 25Firstly, there is the issue of bacteriological water quality. Rainwater can become contaminated by facesentering the tank from the catchment area. It is advised that the catchment surface always be kept clean.Rainwater tanks should be designed to protect the water from contamination by leaves, dust, insects, vermin,and other industrial or agricultural pollutants. Tanks should be sited away from trees, with good fitting lids andkept in good condition. Incoming water should be filtered or screened, or allowed to settle to take out foreignmatter (as described in a previous section). Water which is relatively clean on entry to the tank will usuallyimprove in quality if allowed to sit for some time inside the tank. Bacteria entering the tank will die off rapidlyif the water is relatively clean. Algae will grow inside a tank if sufficient sunlight is available for photosynthesis.Keeping a tank dark and sited in a shadyspot will prevent algae growth and also keep the water cool. As mentioned in a previous section, there are anumber of ways of diverting the dirty ‘first flush’ water away from the storage tank. The area surrounding aRWH should be kept in good sanitary condition, fenced off to prevent animals fouling the area or childrenplaying around the tank. Any pools of water gathering around the tank should be drained and filled.Gould points out that in a study carried out in north-east Thailand 90 per cent of in-house storage jars werecontaminated whilst only 40% of the RWH jars were contaminated. This suggests secondary contamination(through poor hygiene) is a major cause of concern.Secondly, there is a need to prevent insect vectors from breeding inside the tank. In areas where malaria ispresent, providing water tanks without any care for preventing insect breeding can cause more problems thanit solves. All tanks should be sealed to prevent insects from entering. Mosquito proof screens should be fittedto all openings. Some practitioners recommend the use of 1 to 2 teaspoons of household kerosene in a tank ofwater which provides a film to prevent mosquitoes settling on the water.There are several simple methods of treatment for water before drinking.1. Boiling water will kill any harmful bacteria which may be present2. Adding chlorine in the right quantity (35ml of sodium hypochlorite per 1000 liters of water) willdisinfect the water3. Slow sand filtration will remove any harmful organisms when carried out properly4. A recently developed technique called SODIS (SolarDisinfection) utilizes plastic bottles which are filledwith water and placed in the sun for one full day. The back of the bottle is painted black. Moreinformation can be found through the Resource Section at the end of this documentQuality of waterWhether given water is suitable for a particular purpose depends on the criteria or standards of acceptablequality for that use. The physical as well as chemical quality of water is important to decide its suitabilityfor drinking purpose. Various standards are formulated by National and International agencies such asWHO, ICMR, PHE Committee and all the standards are recommendatory and provide guidelines fordeciding the requirements. Rain water samples were collected from project sites during the rainy season andanalyses. The parameter analyzed included ph, conductivity, total dissolved solid, total hardness, calcium,magnesium, chloride,, sodium etc. The analysis was carried out to know range of the parameters containedin rain water and compare with the standards recommended by various agencies. The data generated byanalysis of water samples are shown below.
  26. 26. 26
  27. 27. 27Chapter.6HYDROLOGICAL ANALYSIS-On the basis of experimental evidence, Mr. H. Darcy, a French scientist enunciated in 1865, a lawgoverning the rate of flow (i.e. the discharge) through the soils. According to him, this dischargewas directly proportional to head loss (H) and the area of cross-section (A) of the soil, andinversely proportional to the length of the soil sample (L). In other words,Q . A Q = RunoffHere, H/L represents the head loss or hydraulic gradient (I), K is the co-efficient of permeabilityHence, finally, Q = K. I. A.Similarly, based on the above principle, water harvesting potential of the catchment area wascalculated.The total amount of water that is received from rainfall over an area is called the rainwater legacyof that area. And the amount that can be effectively harvested is called the water harvestingpotential. The formula for calculation for harvesting potential or volume of water received orrunoff produced or harvesting capacity is given as:-Harvesting potential or Volume of water Received (m3)= Area of Catchment (m2) X Amount of rainfall (mm) X Runoff coefficientRunoff coefficient for any catchment is the ratio of the volume of water that runs off a surface tothe volume of rainfall that falls on the surface. Runoff coefficient accounts for losses due tospillage, leakage, infiltration, catchment surface wetting and evaporation, which will allcontribute to reducing the amount of runoff. Runoff coefficient varies from 0.5 to 1.0. In presentproblem statement, runoff coefficient is equal to 1 as the rooftop area is totally impervious.
  28. 28. 28METHODS FOR STORAGE OF HARVESTED RAINWATER IN TANK-Finally, we need to store the water which is obtained from the rooftop areas of the differentbuildings. The volume of tank which stores the harvested water will be directly proportional tothe total volume of water harvested.Technically, there are two types of methods for distributing the harvested rainwater:-1. RATIONING METHOD (RM)2. RAPID DEPLETION METHOD (RDM)To explain these both methods, let us first apply it on any hall say M.S.S. hall. The detailcalculation is carried out to get the valuable steps. Later on, these crucial steps are again appliedto all other building and number of days for consumption of stored water is calculated by usingboth of these methods.1. RATIONING METHOD (RM)-The Rationing method (RM) distributes stored rainwater to target public in such a way that therainwater tank is able to service water requirement to maximum period of time. This can be doneby limiting the amount of use of water demand per person.Suppose in this method, the amount of water supplied to student is limited which is equal to say,100 lt/day per capita water demand.Again, Number of students at M.S.S. HALL = 300Then, Total amount of water consumption per day = 300x0.1 = 30 m3/dayTotal no. of days we can utilize preserved water = stored water/water demandFor M.S.S. Hall (Sample hall), volume of water stored in tank was taken approx. = 3600 m3Hence finally, no of days = 3600/30 = 120 days (or 4 months)For long term storage of preserved water in good condition, preserving chemical should be added.2. RAPID DEPLETION METHOD (RDM)-In Rapid Depletion method, there is no restriction on the use of harvested rainwater by consumer.Consumer is allowed to use the preserved rain water up to their maximum requirement, resultingin less number of days of utilization of preserved water. The rainwater tank in this method isconsidered to be only source of water for the consumer, and alternate source of water has to beused till next rains, if it runs dries.For example if we assume per capita water demand = 150 lt/day = 0.15 m3/dayTotal amount of water consumption per day = 300 x 0.15= 45m3/dayTotal no. of days, preserved water can be utilize = stored water/water demand= 3600/45= 80 days (2.67 months)Hence, finally it is observed that, if the amount of water stored is equal to 3600 m3, then applying1. RDM, consumer can only utilize the preserved stored water for about 80 days (2.67 months),2. Where as in RM, preserved stored water can be utilized for a period of 120 days (4 months).
  29. 29. 29OPTIMISTICDETERMINATIONOF SIZE & TYPES OF TANK-COMPUTATION OF VOLUME OF RUNOFF PER YEAR:As we know the formula for runoffdischarge –Volume of water Received (m3) = Area of Catchment X Amount of Rainfall
  30. 30. 30Chapter.7TYPES OF TANK:Two type of tank can be used for storing of rainwater discharged from the roof1. LINED STORAGE TANK2. UNLINED NATURAL STORAGE TANKIn lined storage tank, earth work excavation is done and underground RCC water storage tank isconstructed which is completely covered from the top. The land above the tank can be used forserving as playground or parking slot, etc. In unlined natural storage tank, earth excavation isdone and all the water being allowed to fall directly in that pit and store it. In this method, we gettwo advantages.Firstly, our natural water gets recharged leads to augmentation of water level and groundcondition, increasing prospects for better future cultivation and plantation. Secondly,underground water can be extracted anywhere within some limited areas from that pit and can beused to satisfy daily water demand.
  31. 31. 31DETAIL ANALYSIS & DESIGNING OF RAINWATER HARVESTING SYSTEMCOMPONENT-In this section, all the component of rainwater harvesting system is to be designed for all thebuildings located inside the campus .Hence to start of, a sample calculation was done on a sample hall say M.S.S. hall, which willdraw the steps which has to be followed by all other building for designing its systemcomponents.Hence given below the complete design of all the components of rainwater harvesting of vit eastjaipur whose dimensions are mentioned in the figures 7 and tank size is 4 X 5 X 12.ANALYSIS & DESIGN OF UNDERGROUND SUMPProblem Statement :Height of tank= 4mArea of base = 60m2Taking subsoil consists of sand, angle of repose = 30®Saturated unit weight of soil = 17 K/m3Water table likely to rise up to ground levelM20 concrete, HYSD barUnit weight of water = 9.81 KN/m3Solution:There are four components of design:-i) Design of long wallii)Design of short walliii)Design of roof slabiv)Design of base slabGERNERALDesign of wall be done under two condition:-a) Tank full with water, with no earth fill outsideb) Tank empty with water, with full earth pressure due to saturated earth fill.41 Department of Civil Engineering,The base slab will be design for uplift pressure and the whole tank is to be tested against floatation.Taking size of the base of tank =12X5mAs length (L)=12mBreadth(B)=5mL/B=12/5=2.3{>2} , Hence long wall be designed as a cantilever.Bottom H/4 =4/4 = 1m of short wall be designed as cantilever , whileTop portion will be design as slab supported by long walls.2. DESIGN CONSTANTFor M20 concrete, бcbc=7N/mm2 , m=13Since face of wall will be in contact with water for each condition,Бst=15N/mm2 for HYSD bar.Permissible compressive stress is steel under direct compression = Бsc = 175 N/mm2For Бcbc = 7 N/mm2 ,Бst = 150 N/mm2 , m= 13 ,We have, K = = 0.378J= 1-(0.378/3) = 0.874R = 1/2 X 7 X 0.874 X0.378 = 11563. DESIGN OF LONG WALL
  32. 32. 32a) Tank Empty with pressure of saturated soil from outsidePa = KaγH+γwHγ = = 1/3γ‟ =17-981=7.19 Kn/m3 = 7190 n/m3γw = 9.81 Kn/m3Pa = (1/3)X7190X4 + 9810X4 = 48,426.67 N/m2Maxm. B.M. @ base of wall = 48,426.67 X (4/2)X (4/3) = 130,204.44 nmD= = 335.6mmProvide total depth D= 380 mmD = 380 -35 = 345 mmAst = = 2,878.75 mm2Using 30mm Φ bar, spacing ==109.13mmHence, provide 20mm Φ bar @ 100mm c/c on the outside face @ bottom of long wall.CURTAILMENT OF REINFORCEMENTSince the B.M. is proportional to h3Asth/Ast = (h/H) 3 from which, h= H(Asth/Ast) ^(1/3)If Asth = 1/2XAst (I.e. half of bar being curtailed)h= H(1/2)^(1/3) = 4(1/2)^(1/3)=3.17 mHeight from base = 4-3.17 = 820 mmHeight as per code, IS 456, bar should contain further for a distance of 12Φ or d (which ever more)12 XΦ = 12X 12 = 240D=345mm,So bar curtailed @ distance from the base = 820+345 = 1.17mMin % of reinforcement = 0.3 – 0.1 = 0.23 %Min Ast = 0.23X380X1000/100=879.43mm2So, curtailment @ 1.17m from the base = 0.5XAst = 0.5 X 28787 =1439.35 > 879.43 (O.K)DISTRIBUTION REINFORCEMENTAst = 879.43 mm2Area to be provided on each face = 879.43/2 = 439.72 mm2Hence proving 10mm Φ @ spacing = 170mmTaking spacing = 160mm on both face of long wallDIRECT COMPRESSION IN LONG WALLThe earth pressure acting on short wall will cause compression in long wall, because top portion ofshort wall act as slab support on long walls.At h=1m(>H/4) above the base of short wallPa=Kaγ‟ (H-h)+γ w (H-h)=(1/3)X7190(4-1)+9810(4-1) = 33,620N/m2This direct compression developed on long wall is given byPlc=Pa.B/2=33620X5/2 = 91,550 N {This will be taken by distribution steel & wall section.}Rainwater Harvesting at N.I.T. Rourkela 2 0 1 043 Department of Civil Engineering, N.I.T. RourkelaB>TANK FULL WIT H WATER & NO EARTH FILL OUTSIDEP=γwh=9810x4=39240 N/M2M=P.H2/6 = 39,240 X42/6 = 104640 NmAst = = 2,313.53 mm2Using 20mm Φ @ spacing = = 135.7Taking 20mm Φ @ spacing 130mm c/c @ inside face.CURTAILMENT OF REINFORCEMENTAsth/Ast = (h/H) 3 from which, h= H(Asth/Ast) ^(1/3)If Asth = 1/2XAst (I.e. half of bar being curtailed)h= H(1/2)^(1/3) = 4(1/2)^(1/3)=3.17 mHeight from base = 4-3.17 = 820 mm
  33. 33. 33Height as per code, IS 456, bar should contain further for a distance of 12Φ or d (which ever more)12 XΦ = 12X 12 = 240D=345mm,So bar curtailed @ distance from the base = 820+345 = 1.17mSo, at the base, 20 mm Φ @ 130mm c/cAt top from 1.17m from base, 20mm Φ @ 260mm c/cDIRECT TENSION ON LONG WALL:-Since the top portion of short wall act as slab supported on long wall, the water pressure acting onshort wall will cause tension in long wall:-Pl=P.B/2 = 9810 X 3X 5/2 = 73, 575 NAs req. = 73,575/150 = 490.5mm2Area of distribution steel (=879.43 mm2) will take direct tension.4.DESGIN OF SHORT WALLSA) TANK EMPTY WITH EARTH PRESSURE FRON OUTSIDEI) TOP PORTIONThe bottom 1m (H/4) act as cantilever while the remaining above 3m act as slab on long wallAt, =1m, above base of short wall,Pa-= Kaγ‟ (H-h)+γ w (H-h)Rainwater Harvesting at N.I.T. Rourkela 2 0 1 044 Department of Civil Engineering, N.I.T. Rourkela=(1/3)X 7190X3 + 9810 X 3 = 36,620 N/m2Mf@ support = PaL^2/12 = 36,620 X 5^2 / 12 = 76,291.67 NmThis causes tension outside.Mf @ centre = PaL2/8 – Mf = 36,620 X 52 (1/8- 1/12) = 38,145.83 Nmd= 380 –(25+20+10) = 325 mmAt support, Ast = = 1790.57mm2Using 16mm Φ bar Ast = = 116.7mmSo providing 16mm Φ bar@ spacing 110mm c/c @ outer face.At mid span, Ast = (0.5X1790.57 = 895.285 mm2Providing 16mm Φ @ spacing = 223.3 .i.e. providing 220mm c/c at inner face.II)BOTTOM PORTIONThe bottom 1m will bend as cantilever.Intensity of earth pressure @ bottom = 48,826.67 N/m2 (from step 3)M = 0.5X 48,826.67X1X (1/3) = 8137.78 NmAst = = 179.92 mm2Minm. Steel @ 0.23% = 879.43 mm2So, Ast = Astminm.Spacing of 12mm Φ = = 128.5 .i.e. 120 mm c/cHence providing 12mm Φ bar @ spacing 120mm c/c at the outside face in vertical direction forbottom 1m height.DIRECT COMPRESSION IN SHORT WALLOnly one meter of long pushes the short wall due to earth pressure, Pbc = PaX1 =36,620nThis compression is being taken up by distribution reinforcement.B)TANK FULL WITH WATER AND NO EARTH FILL OUTSIDEi)TOP PORTIONP=W(H-h) = 9810 X3 = 29,430 N/m2Mf @ support = PB2/12 = 29430 X 5^2 / 12 = 61,312.25 Nm causing tension at the inside.Mc @ centre = PB2/24 = 0.5 X 61,312.5 = 30,656.25 Nm causing tension at the outside.Direct tension on short wall due to water pressure on the end 1meter of long wallP b =W(H-h) X 1
  34. 34. 34=29,430 X1 = 29430 NEffective depth d, for horizontal steel= 325mm @ distance x = d-D/2 = 325 – 380/2= 135 mmAst1 = M-Pbx/БstjdAst2 = Pb/бsAT INSIDE FACE (END OF SHORT WALL)Ast1 =– = 1345.8mm2Ast2 = 29430 / 150 = 196.2 mmTotal = 196.2+1345.8 = 1542 mm2Using 12mm Φ bar, spacing = 1000X113/1542 = 75 mm c/c.AT OUTSIDE FACE (MIDDLE OF SHORT WALL)Ast1 =– = 636.26mm2Ast2 = 29430 / 150 = 196.2 mmTotal = 196.2+636.26= 822.46 mm2Using 12mm Φ bar, spacing = 1000X113/822.46 = 120 mm c/c @ outside face.i)BOTTOM FACEP (from step 3b)= 39240 N/m2Mf 0.5X(1/3)X 39240 = 6540 Nm causing tension at the inside.Mc @ centre = PB2/24 = 0.5 X 61,312.5 = 30,656.25 Nm causing tension at the outside.Ast = = 144.6 mm 2But min. Steel req. = 879 mm2So providing 12mm Φ bar @ spacing 120mm c/c.SUMMARY OF REINFORCEMENT IN SHORT WALLTaking of maxm out of both case 4A and 4BRainwater Harvesting at N.I.T. Rourkela 2 0 1 046 Department of Civil Engineering, N.I.T. RourkelaI) Horizontal reinforcement @ inner face = 16mm Φ @ 75mm c/cI) Horizontal reinforcement @ outer face = 16mm Φ @ 110mm c/cIII) Vertical reinforcement @ inner face & outer face = 12mm Φ @ 120mm c/c5.DESIGN OF TOP SLABL/B = (12/5 ) = 2.4 (> 2) i.e. one way slabLet live load on top slab = 2000 N/m2Assuming thickness of 200mm including finishing ,etc.Self weight = 0.2 X 1X1X 25,000 = 5000 N/m 2Total weight = 2000+5000 = 70000 N/m2M = WB^2 / 8 = 7000(5+0.38) 2 / 8 = 25,326.35 NmD= = 140mmProviding a total thickness (D) = 180mmd = 180-25-6 = 149 mmAst = = 1302.5 mm2Spacing of 16mm Φ = 1000X201/1302.5 = 150 mm c/c @ outside face.DISTRIBUTION REINFORCEMENTPt % = 0.3 – 0.1 X = 0.277%Spacing of 10mm Φ bar = 1000 X 78.54 / 415.7 = 180 mm c/c6.DESIGN OF BOTTOM SLABMagnitude of uplift pressure, Pu = WH1= 9810 X 4.3 = 42,183 N/m2A) CHECK FOR FLOATIONCheck is done when tank is empty.Total upward floatation force = P = Pu X B X L = 42183X5X12 = 2530980 NTotal Downward force = weight of wall + (weight of roof slab + finishes) + weight of base slab
  35. 35. 35= [0.38(5+5+12+12) X4.3X25000] + [ 0.2X 5X12X25000] + [ 5X12X0.3X25000]= 2138900NWeight of roof so downward force is less than buoyant force, we need to provide extension of 0.5 mon both side.Extra weight req. = 2530980-2138900 = 392080NBy extending 0.5 on both side, extra weight of tank= [(0.5 x 5 X 2) + (0.5 X 12 X 2) + (0.5 X 0.5 X 4)] X 25000 X 0.3= 135000 NWeight of soil = [(0.5 x 5 X 2) + (0.5 X 12 X 2) + (0.5 X 0.5 X 4)] X 17000 X 4= 1224000 NTotal = 1359000N (safe)B)DESIGN OF BASE SLABConsidering 1m length of slab, upward water pressure = 42183N/m2Self weight of slab = 1 X 1 X 0.3 X 25000 = 7500 N/m2Net upward pressure, P = 34683 N/m2Weight of roof slab per meter run = 0.2 (2+0.38)X1X25000 = 11900 NWeight of wall / meter run = 0.38X4X1X25000 = 38000 NWeight of earth projection = 1700 X 4 X 1 X 0.5 = 34000 N/mNet unbalance force / meter run = 34683 (6.286 X 1) – 2 (38000 +11900 + 34000) = 50217.3NReaction on each wall = 50217.3/2 = 25108.67 NPa = Kaб‟ H + wH = 48826.67 N/m2Pa =48826.67 X(4/2) X 1 = 97653.34 Nm acting @ (4/3)+0.3 = 1.66 m from the bottom of baseslabB.M. @ edge of cantilever portion = (34683 X 0.5 2 / 2 )+ 25108.67 X1.66- (1700X4X0.52/2)= 45165.76Nm causing tension @ bottom face.B.M @ centre of span = ((34683/2)X (6.286) 2/4) + 97653.34X1.66 –(38000+11900+25108.67)X4.38/2 -1700X4X0.5(6.38/2-0.25) = 234044.7 Nmd = = 450 mm, so keeping D = 500 mm , d = 450 mmAst = = 7140.1 mm2Providing 24mm Φ bar spacing = 1000X 452.4 / 7140 = 65 mm c/cDistribution reinforcement in longitudinal direction = 0.3 – 0.1[]= 0.243 % Area o n steel = 0.243 X1000X300/100 = 729 mm2Area on steel on each face = 729 /2 = 364.5 mm2Spacing of 8mm Φ bar = 1000X 50.3 / 364.5 = 138 mmProvide 8 mm Φ bar @ 130 mm c/c on each face.DETAIL COST ESTIMATION OF SUMP (UNDERGROUND TANK)Finally cost of entire project play a crucial role in any type of project. Before implementing theproject, it is highly necessary for the engineers to check project, whether it is economical or not.Hence, the detail cost estimation should be done.Tank shall be of first class brickwork in 1:4 cement mortar foundations and floor shall be of 1:3:6cement concrete. Inside of septic tank shall be finished with 12mm cement plaster and floor shall befinished with 20mm cement plaster with 1:3 mortar mixed with standard water proofing compound.Upper and lower portion of soak-pit shall be of second class brickwork in 1:6 cement mortars andmiddle portion shall be of dry brickwork. Wall thickness is about 30cm.
  36. 36. 36Chapter.8DETAIL COST ESTIMATION OF SUMP (UNDERGROUND TANK) –Finally cost of entire project play a crucial role in any type of project. Before implementing theproject, it is highly necessary for the engineers to check project, whether it is economical or not.Hence, the detail cost estimation should be done.Tank shall be of first class brickwork in 1:4 cement mortar foundations and floor shall be of 1:3:6cement concrete. Inside of septic tank shall be finished with 12mm cement plaster and floor shallbe finished with 20mm cement plaster with 1:3 mortar mixed with standard water proofingcompound. Upper and lower portion of soak-pit shall be of second class brickwork in 1:6 cementmortars and middle portion shall be of dry brickwork. Wall thickness is about 30cm. Roofcovering slabs shall be precast R.C.C. The length of the connecting pipe from latrine seat may betaken as 3 meters. And suitable rates are assumed.Given below the detail cost estimation of constructing an underground sump of dimensions (4 x 5x 12) at hostel site:
  37. 37. 37Hence, after studying the present market value of material required for constructing the entire tankand using it while calculating during costing and estimation of tank. After all several steps, the totalcost of tank was came out to be Rs. 7,17,685.80. This steps was applied to all other building fordetermining the final cost price of the tank.FIRST FLUSH MECHANISMSFirst flush mechanism is shown in the fig8. Due to long dry period, the catchment area generally getsdirty. Hence in order to prevent entry of excess dirt from the catchment area from entry into tank andpolluting the water, first flush mechanism is designed. And the order of this mechanism becomeshighly important when water preserved is utilized for drinking purpose. Turbidity factor was alsoconsidered while design first flush mechanism. After studying our requirement and prevailingcondition, the design value of this mechanism was fixed to be 8liters/10m2. And finally Ball-Valvedesign was chosen. Ball-Valve design has a unique mechanism for controlling the flow of water intoand outside of the tank. Ball-Valve design is shown in the figure. This system consists of ball insidethe specially designed pipe which opens and closes the opening of outlet to the storage tank anddiversion chamber according the level of water. When the water fills up to the brim, the water isdiverted to the main tank from the side outlet. And when the water needs to be rejected is sent to thesmall diversion chamber where it fills the inlet pipe.Ball Valve Type First-Flush Mechanismthe diversion chamber and the pipe up to the Ball-Valve are carefully designed to match thediversion volume that is calculated. The connection between the terrace water and storage tankrebuilds when water reaches the level of the ball making the ball to float and block the connectionbetween the terrace water and diversion chamber, thus sending the water back again to mainstorage tank. In this way, Small diversion chambers are designed for the downpipes from eachterrace. The diversion tank can have a tap which may be operated.
  38. 38. 38FiltrationFiltration is highly required for the rainwater which is harvested from the rooftop area. Whenwater is use for drinking purpose then this process become even more important. But, basicfiltration is preferable required to avoid excessive dirt entering the system. A very simple, cost-effective mechanism has been chosen preferred overelaborate commercial systems. Leaf and twigscreen, for basic which is a 5mm thick mesh with wire frame running along the gutters wasselected. With most of the commercial fine filtration systems, there is a general difficulty ofhandling high flow rates, thus, a practical filtration method was selected running the flow througha fine cloth/mosquito net mesh. The flow rate would not be impeded much; it’s very costeffective and can be easily maintained and replaced. Again, two cloth filters for hydraulic andcleaning efficiency using a graded sand load can be chosen whose results are highly comparableto commercial filters.
  39. 39. 39
  40. 40. 40CONCLUSIONThis paper dealt with all aspect of improving the water scarcity problem in the vit campus byimplementing ancient old technique of rainwater Harvesting. Two alternatives have been suggestedfor tank design, which takes separate approaches towards the consumption of harvested rainwater.These results are given clearly in the table. Hence from this table, we can draw out a conclusion that ahuge amount of water got collected from the rooftop surfaces of all the entire buildings. And if, thisproject is being done seriously and implemented to the campus then R5 (behind Mechanical) has ahuge harvesting potential. This reservoir should have to build for the storage of 9942.1 m3 of water.Hence this tank has huge capacity of getting rainwater and on proper storage, this tank can supplyalmost throughout the year for about 300 consumers having a consuming rate of 100liter/day ascalculated by rational depletion method. The water has almost the potential amount of tank-Reservoir capacity (m3) No. of days of potential byRational MethodsNo. of days of potential byRapid depletion method9942.1(R5) 331.40 220.93Tank cost – Rs. 717685.8

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