Rainwater harvesting building
Contents
Introduction 3
Design of water harvesting building 3
Preliminary design 3
Detailed design and development 3
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 aluminium sheet preferably. A drain or gutter is provided along the edge of the roof for collecting water. The gutter is attached with a slight slope towards pipe to make water flow freely in the storage tank. This may be constructed with of G.I. sheet, bamboo or any other available material. The diameter of down 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 is used as filler materials. (Ward, Memon and Butler, 2012) 3
Storage tank :- 3
Detailed production phase 4
Construction of the underground storage tank 4
System evolution 5
Size estimation 5
Quantity of water, which can be harvested 5
Characteristics of water harvesting building design- 5
Validation 5
Conclusion 6
References 7
Introduction
The 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. Rain water is bacteria free, pure, does not consist any organic matter and also soft water. Rainwater harvesting is a relevant technique for those areas which does 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 is 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 not only save water, but save money also. One cannot even imagine life without water that’s why saving or collecting water is nowadays very important. (Ward, Memon and Butler, 2010)
Design of water harvesting building
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. Rooftop is designed with material like plastic corrugated sheets, cement tiles, corrugated clay tiles, concrete slab, etc. the rain water is collected on the roof of a building. Catchment or roof size influences the volume of collected water because of the size of building 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 non potable 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)
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 aluminium sheet preferably. A drain or gutter is provided along the edge of the roof for collecting water. The gutter is attached with a slight slope towards pipe to make water flow freely in the storage tank. This may be constructed with of G.I. sheet, bamboo or any other available material. The diameter of down 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 is 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 constructed 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 in the little raised platform. For cleaning of the storage tank one outlet pipe can be fixed at the bottom level of the tank. The size of the storage tank is depend on the water daily need, catchment area or roof top area and rainfall.
Components of a storage tank are-
A manhole of 0.50 m × 0.50 m size with cover
Vent pipe/ overflow pipe (with screen) of 100 mm diameter.
Drain pipe (100 mm diameter) at bottom.
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, tap can be used for water outlet. (Matos et al., 2015)
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 suitable material for tank construction as it is durable and long running. A benefit of concrete cisterns is that it decrease 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 according to the ratio 1:2:4 ( 1 part cement: 2 parts of coarse sand and 4 parts of stone aggregates of 20 mm nominal size).
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 in 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 by chicken wire mesh all over it and plastered in cement mortar. 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 carry rainwater from the catchment or the roof area to harvesting system. Some benefits of using Poly vinyl chloride pipes are, these are cheap in terms of money, light weight, have the resistance from corrosion, non toxic and nonpoisonous, have less conductivity for heat, ho not affected by bacteria, very easy to install and have resistibility from ultra violet rays. (Roebuck, Oltean-Dumbrava and Tait, 2010)
System evolution
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 the case of roof area covering to improve water runoff. The size of the catchment area and the tank should be enough to supply sufficient water for the users during the dry period. To calculate the volume of the tank such formula can be used:-
V = (t × n × q) + et
Where, V = Volume of the tank (litres)
t = duration of dry season (days)
n = Number of users
q = Consumption per capita per day (litres)
et = Evaporation loss during the dry period (Bicknell, 2012)
Quantity of water, which can be harvested- the amount of water which is harvested into gutter system is calculated by using the following formula-
Q = RC × R × A,
Where, Q = quantity of water that runs off,
RC =runoff coefficient,
R= total rainfall (mm/y),
A = the area of catchment (m2). (Jebamalar, Ravikumar and Meiyappan, 2012)
Characteristics of water harvesting building design-
The material used in the construction of the roof should be non poisonous.
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 storage tank should have a tight fitting roof that excludes light, a manhole cover and a flushing pipe at the bottom of the tank.
The contaminated water should not enter into the storage tank.
Water from other unreliable sources should not be emptied into the tank through pipe connections or the manhole cover. (Dallman et al., 2016)
Validation
Validation of rainwater harvesting, building design can be done by the following methods:-
For validation first that should be found out that where 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 need to be recorded that in daily purposes like in flushing, in graders how many litre 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 in order 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. (Chiu, Tsai and Chiang, 2015)
Conclusion
Rainwater harvesting is the best way of making use of rainfall all around the world. Rain water 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 non toxic materials for the construction of the roof and the catchment area and for the storage tank also non toxic material should be used.storage tanks should be properly constructed with ferrocement. 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 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.
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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.
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.
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.
Rainwater harvesting. (2011). Structural Survey, 29(3).
Roebuck, R., Oltean-Dumbrava, C. and Tait, S. (2010). Whole life cost performance of domestic rainwater harvesting systems in the United Kingdom. Water and Environment Journal, 25(3), pp.355-365.
Ursino, N. (2016). Risk Analysis Approach to Rainwater Harvesting Systems. Water, 8(8), p.337.
Ward, S., Memon, F. and Butler, D. (2010). Rainwater harvesting: model-based design evaluation. Water Science & Technology, 61(1), p.85.
Ward, S., Memon, F. and Butler, D. (2010). Rainwater harvesting: model-based design evaluation. Water Science & Technology, 61(1), p.85.
Ward, S., Memon, F. and Butler, D. (2012). Performance of a large building rainwater harvesting system. Water Research, 46(16), pp.5127-5134.
Ward, S., Memon, F. and Butler, D. (2012). Performance of a large building rainwater harvesting system. Water Research, 46(16), pp.5127-5134.