Harvesting of water
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Contents
Introduction 3
Theory 3
Design of water harvesting building( model) 3
Preliminary design 3
Detailed design and development 4
Storage tank:- 5
System test 7
Size estimation 7
Harvesting system evolution 8
Human factors 8
Validation 9
Optimization 9
Conclusion 10
Research skills 10
References 10
Introduction
Rainwater harvesting system is an approach in which rainwater is collected and stored naturally in tanks or reservoirs. It is very beneficial for the areas which receive heavy rainfall. Rainwater is bacteria free, pure, does not consist any organic matter and also soft water. Rainwater harvesting is a relevant technique for those areas which do not have sufficient water and experience water storage due to overuse or because of less availability of reservoirs but have sufficient rainfall. One of the most important methods of rainwater harvesting is rooftop harvesting. In assessment 1, the literature view and conceptual part of rainwater harvesting are being discussed. Now taking that assessment further, here we analyze the design of the rainwater harvesting building in detail and its validation and evolution.
Water is an important and precious resource because of its use and demand in population. With the help of rainwater harvesting, this demand of water can be fulfilled up to 50%. This is not only saves water, but save money also. One cannot even imagine life without water that’s why saving or collecting water is nowadays very important. (Matos et al., 2015)
Theory
For setting up a rainwater harvesting system in a building, here used a theory called LEED BD&C 2009. This theory focuses on the conservation factors and specify all the essential parameters that need to be taken care in the construction of a harvesting building. This prerequisite the reduction of water uses, credits water efficient landscaping, innovating technologies for wastewater reduction by calculating sewage in buildings. Based on LEED BD&C 2009 theory, the appropriate model of rainwater harvesting for buildings is discussed below.
Design of water harvesting building( model)
Preliminary design
A simplest rainwater harvesting system includes a storage tank or reservoir to collect water; this storage tank is connected with a pipe from the rooftop. The rooftop is designed with material like plastic corrugated sheets, cement tiles, corrugated clay tiles, concrete slab, etc. the rainwater is collected on the roof of a building. Catchment or roof size influences the volume of collected water because of the size of building the roof. The collected rainwater volume is also affected by the intensity of rainfall in the area. The reliability of the system depends on the nature of consumption of water, such as potable or nonpotable uses and volumes of collected water. The volume depends on the condition of climate while consumption depends on the society habits. In brief, the reliability will determine whether the system is successful and economically feasible or not. (Ursino, 2016)
Figure:- flow chart of rainwater harvesting system
Source:- https://commons.wikimedia.org
Detailed design and development
Catchment and gutter pipe:-
Most important component of rainwater harvesting is catchment; it is used to store the collected water. The existing size of the roof catchment area is 102 mm approximately and from which 40mm is used as gutter and used for holding or storing rainwater. The roof should be made of galvanized iron sheets or aluminum sheet preferably. A drain or gutter is provided with the corner of the roof for collecting water. The gutter is attached with a slight slope towards pipe to make water flow freely into the storage tank. This may be constructed with Galvanized iron sheet, bamboo or any material which is easily available. The diameter of down or outlet pipe should be 100mm and to prevent entrance of dry leaves and other debris, it should be covered with 20mm wire screen at the inlet. For filtering the water, sand, palm, coconut fibres are used as filler materials. (Ward, Memon and Butler, 2012)
Storage tank:-
The other component of rainwater building harvesting design is storage tank. This tank can be made under the ground or above the ground. The underground tank may be masonry or R.C.C. structure suitably lined with water proofing materials. The tank constructed on the surface of the ground should be of G.I. sheet or Ferrocement. The tank should be placed on the little-raised platform. For cleaning of the storage tank, one outlet pipe can be attached at the lower part of the storage tank. The storage tank size depends on the daily water need, catchment area or rooftop area and rainfall.
Components of a storage tank are-
A storage tank of 0.50 m × 0.50 m size with cover
Vent pipe/ overflow pipe (with screen) of 100 mm diameter.
Drain pipe with 100 mm diameter at the end point.
In case of the underground tank, approximately 30 cm of the tank should be above the ground; a hand pump should be installed for taking out the water from the tank. In case of the tank which is above the surface, the tap can be used for water outlet. (Matos et al., 2015)
Figure: model of rainwater harvesting building
Source:- https://stanfordanamcityproject.wordpress.com
Detailed production phase
Construction of the underground storage tank
Reinforced Cement Concrete Tank (RCC)
Reinforced concrete tanks can be constructed underground or on the surface of the ground. Concrete is a suitable material for tank construction as it is durable and long-running. A benefit of concrete cisterns is that it decreases the rainwater cohesiveness because of dissolution of calcium carbonate. Every tank should have the system for the overflowing of water in case of excess water. The overflow system should connect to the drainage system. The reinforced cement concrete tank design and the construction method follow the requirement IS 3370 (part-I) -1965 and IS 456-1964. The mixture of cement and concrete must come according to the ratio 1:2:4. In this ratio one part of the cement, two parts of coarse sand and four parts of stone is added. The size of the stone must be about 20 mm.
Some rules and regulations should be followed while constructing an RCC tank are- in the mixture of cement and concrete the amount of water should be appropriate by not adding too much water to the mixture. After mixing, it must be applied within half an hour. (Akpinar Ferrand and Cecunjanin, 2014)
Construction of roof of the tank
For constructing the roof, mild steel materials is used for making the frame and it also covered fully with the help of mesh made with chicken wire. The roof has two opening one for filter containers with the diameter of 35 cm and second is for manhole with the diameter of 60 cm. Filter opening must be one side of the roof and manhole should be in the center. (Blocken and Carmeliet, 2012)
Construction of drain or gutter pipes
Poly vinyl chloride pipes are used for the water inlet and outlet. These pipes takes water of the rain from the catchment or the roof area to the harvesting tank. Some benefits of using Poly vinyl chloride pipes are, these are cheap regarding money, light weight, have the resistance from corrosion, nontoxic and nonpoisonous, have less conductivity for heat, ho not affected by bacteria, very easy to install and have resistibility from ultraviolet rays. (Ward, Memon and Butler, 2012)
System test
Size estimation
The size of the system design depends on the actual available area of the roof and rainfall. These factors are not controllable, but some modification could be done in terms of roof area covering to inhance runoff of water. The size of the catchment area and the tank should be appropriate so that it can store that much water which is needed by the users in the period of no rainfall. To calculate the volume of the tank, such formula can be used:-
V = (t × n × q) + et
Where V = Volume of the storage tank in litres
t = duration of no rainfall period in days
n = Number of users
q = Consumption per capita per day (litres)
et = Evaporation loss during the no rain season (Bicknell, 2012)
Quantity of water, which can be harvested-
The quantity of water which is harvested into the gutter or harvesting system is measured by the following formula-
Q = RC × R × A,
Where Q = quantity of water,
RC =runoff coefficient,
R= total rainfall (mm/y),
A = the catchment area (m2). (Jebamalar, Ravikumar and Meiyappan, 2012)
Harvesting system evolution
The material used in the construction of the roof should be nonpoisonous.
The surface of the roof should be smooth and tough and easy to clean.
Wire mesh screen should be fixed at the inlet/outlet of gutter pipe to prevent entrance of dry leaves etc.
The contaminated water should not enter into the storage tank.
Water from other unreliable sources should not be entered in the storage tank by inlet or outlet pipes. (Dallman et al., 2016)
Human factors
Human factors also involved in the establishment of a rainwater harvesting plant. Harvesting system is developed for the welfare of the human society. Many points should be kept in mind while setting up a rainwater harvesting the plant are like the construction should be based on the total number of the people living in the society or are where plant is being set up. The size of catchment area or roof top also influenced by the human factor and the size of storage tank also choose according to the number of users. The human factor plays a major role in the setup of the rainwater harvesting plant. The system should be environmentally friendly and according to the user. As here we are designing an environmentally friendly building it should be kept in my that the setup should be natural. (Blocken and Carmeliet, 2012)
Validation
Validation of rainwater harvesting, building design can be done by the following methods:-
For validation first, that should be found out that where the plant is going to construct and the survey should be done on the water usage in that area. One survey can be done on the use of water by the users, and it also depends on the number of persons in the family or the community where the harvesting system is going to be established. It needs to be recorded that in daily purposes like in flushing, in graders how many litres water is needed. For calculating this the storage tanks need to be filled, it is utilized fully till the tank is empty. Number of fillings over a period was recorded to determine the daily usage. The data were collected by this can be used for the conclusion that how much water is needed for a person. To find out the real value of parameters of the rainwater harvesting. System design and validate the applicability survey method can be used. The detail of the system is also needed to construct a valid and useful harvesting system such as the area, depth, and capacity of the tank, is it free from toxic, etc. rainfall data also being collected for validation of the harvesting system to know whether it is useful or not. (Mahmoud, Mohammad, and Alazba, 2015)
Optimization
Optimisation of design parameters includes analysis of rainfall, water demand, catchment area, and storage capacity. There is a large scope for improving and enhancing the blueprint of the framework of water harvesting buildings by making it compelling and skillful. It should be considered that the amount of rainfall should be appropriate, for getting the optimum amount of water the harvesting system considerably established in the areas which receive heavy rainfall the area of catchment should be enough that can store a considerable amount of water that is needed. Regular cleaning and maintenance should be done in permanent basis to improve the quality of water; the drainage pipe must be made up with nontoxic materials and outlet and inlet should cover with filter mesh cover. (Chiu, Tsai and Chiang, 2015)
Conclusion
Rainwater harvesting is the best way of making use of rainfall all around the world. Rainwater is a clean source of fresh and soft water that can be collected naturally by the harvesting system, if smartly utilized, it can solve many issues related to the water deficiency. It can be done in both larger and lower scales. For the construction of better, valid and useful water harvesting system building, few points are there that should be kept in mind. Selection of durable and nontoxic materials for the construction of the roof and the catchment area and the storage tank also nontoxic material should be used. Storage tanks should be properly constructed with ferrocement. The roof from where runoff water is to be collected should be made up of materials like bamboos, wood, etc. and should be cleaned regularly. Gutter pipes should be made up of strong and durable material like P.V.C. Construction of the tank should be appropriate so that enough water can be stored for the usage. These are the few points which make a harvesting system valid and useful and long-lasting system for buildings. Rainwater harvesting design surely has so many advantages, but it has disadvantages also like unpredicted rainfall. Due to this, system might be less relevant to the areas where rainfall is considerably less. It also requires regular maintenance and storage limit must be the important issue while setting up a harvesting system.
Research skills
The rainwater harvesting system can be used better or efficiently by using different types of research skills. These research skills could be coming up with some ideas of using rainwater to form electricity, drinking water and other resources that can be beneficial in daily life and also reduce the wastage and unnecessary use of water. How to save water from wastage and how to provide water in the places where rainwater is sufficient but ground water is less. Other that that how to reuse water, could be taken into consideration while developing or constructing such kind of environmentally friendly building.
References
Akpinar Ferrand, E. and Cecunjanin, F. (2014). Potential of Rainwater Harvesting in a Thirsty World: A Survey of Ancient and Traditional Rainwater Harvesting Applications. Geography Compass, 8(6), pp.395-413.
Bicknell, S. (2012). Motor protection for rainwater harvesting. World Pumps, 2012(6), pp.44-45.
Blocken, B. and Carmeliet, J. (2012). A simplified numerical model for rainwater runoff on building facades: Possibilities and limitations. Building and Environment, 53, pp.59-73.
Chiu, Y., Tsai, Y. and Chiang, Y. (2015). Designing Rainwater Harvesting Systems Cost-Effectively in a Urban Water-Energy Saving Scheme by Using a GIS-Simulation Based Design System. Water, 7(11), pp.6285-6300.
Dallman, S., Chaudhry, A., Muleta, M. and Lee, J. (2016). The Value of Rain: Benefit-Cost Analysis of Rainwater Harvesting Systems. Water Resources Management, 30(12), pp.4415-4428.
Ghailan, A. (2015). Rainwater Harvesting in Iraq(2005 JRCSA Forum|Panel Discussion). Journal of Rainwater Catchment Systems, 11(2), pp.43-50.
Ghimire, S. and Johnston, J. (2017). Holistic impact assessment and cost savings of
rainwater harvesting at the watershed scale. Elem Sci Anth, 5(0), p.9.
Jebamalar, A., Ravikumar, G. and Meiyappan, G. (2012). Groundwater Storage through Rain Water Harvesting (RWH). CLEAN – Soil, Air, Water, 40(6), pp.624-629.
Mahmoud, S., Mohammad, F. and Alazba, A. (2015). Delineation of potential sites for rainwater harvesting structures using a geographic information system-based decision support system. Hydrology Research, 46(4), p.591.
Matos, C., Bentes, I., Santos, C., Imteaz, M. and Pereira, S. (2015). Economic Analysis of a Rainwater Harvesting System in a Commercial Building. Water Resources Management, 29(11), pp.3971-3986.
Mun, J., Kim, R. and Han, M. (2012). The Effects of Catchment Materials and Treatment Train on Rainwater Quality in a Rainwater Harvesting System. Materials Science Forum, 724, pp.451-454.
Rainwater harvesting. (2011). Structural Survey, 29(3).
Traboulsi, H. and Traboulsi, M. (2015). Rooftop level rainwater harvesting system. Applied Water Science, 7(2), pp.769-775.
Ursino, N. (2016). Risk Analysis Approach to Rainwater Harvesting Systems. Water, 8(8), p.337.
Ward, S., Memon, F. and Butler, D. (2012). Performance of a large building rainwater harvesting system. Water Research, 46(16), pp.5127-5134.