Rainwater Harvesting System Design

This work aims to develop a proper design of rainwater harvesting system that can be used to supplement the water needs of the occupants in the residential building in order to save the scarce water provided by the government.

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RAIN WATER HARVESTING SYSTEM IN USAGE OF THE RESIDENTIAL BUILDING
By (Name)
Course
Professor’s name
University name
City, State
Date of submission

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Executive summary
Water conservation in high rise buildings have raised concern in the recent years due to
the scarcity of this precious commodity. This has been as a results of the population growth and
urban development. There is huge potential in water saving mechanism that should be harnessed
by our country. This work aims to develop a proper design of rainwater harvesting system that
can be used to supplement the water needs of the occupants in the residential building in order to
save the scarce water provided by the government. This will greatly help in solving the water
demands for users in the residential building since our main objective is to design a proper
system. The report will further highlight the water usage pattern and the materials required for
the design of rainwater harvesting system including the process flow diagram. An inventory
analysis will then be carried out to determine the material, energy, emission unit estimates
required for the design with keen consideration of the cut off criteria formulated. To ensure that
the system is efficient and ready for use, quality assessment of the system will be carried out to
eliminate any doubts of inefficiency in the design system.

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Table of Content
Introduction....................................................................................................................................4
Project objective...............................................................................................................5
Project design process...................................................................................................................5
Application of the rain water harvesting system..................................................................6
Functions......................................................................................................................6
Functional unit..............................................................................................................8
Process flow diagram for rainwater harvest.......................................................................10
Inventory Analysis.......................................................................................................................11
Data collection...............................................................................................................11
Quality Data Assessment.................................................................................................13
Cut off criteria................................................................................................................13
Conclusion....................................................................................................................................14
References.....................................................................................................................................15
Appendix.......................................................................................................................................17

Rainwater Harvesting System Design 4
Introduction
Water is the most precious gift of nature and something that most people take for granted.
The significance of this valuable commodity to our survival and its limited supply is increasingly
being realized by people. Human beings require water for variety of uses. About 71% of the
earth’s surface is composed of water, and out of the total volume of water available on the
earth’s surface 95.5 % is saline , 3.5 % is in the form of ice and glaciers and only 1.5 % is fresh
water (Mun & Han, 2012).
Water is crucial in supporting life of living organisms and has a variety of uses including
its contribution to the larger ecosystem in which the replication of the biodiversity lies. Not only
is insufficiency of fresh water restricted to the dry areas but also in areas with good supply where
accessibility of clean and pure water is becoming a serious problem. Water shortage is brought
about by poor storage capacity of water, poor infiltration, larger inter annual and yearly
fluctuations of rainfall (due to monsoon rains) and high dissolution demand (Li, et al., 2010).
Harvesting of rainwater is a very customary way of obtaining water from surfaces like rock
outcrops, roofs of furrowed iron sheets and other surfaces which prevent water infiltration in
seasonal rivers by building dams and other water storage facilities. Areas where there is
sufficient rainfall the amount stored could be quite substantial (Jothiprakash & Sathe, 2009).
The term ‘Harvesting’ was possibly used first by Geddes of University of Sydney. He
defined ‘harvesting’ as the method of collecting and storing any form of water which could be
runoff or creek flow for irrigation purposes (Otti & Ezenwaji, 2013) Rain water is usually soft,
saturated with oxygen and corrosive. Microorganisms and other eliminated substances in the air
are trapped but the impurities are usually unimportant. However, collecting pools, and containers
can be contaminated and wherever possible after a prolonged dry season one should get rid of the
first rain flush (Chiu, et al., 2009).

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Project objective
Our main goal statement is to design an efficient sustainable rainwater harvesting system
for storage purposes. This is because, an improperly designed system, may lead to future
operational risks, thus raising the maintenance and operational costs. If the problem persist, it
may even results into abandoning of the building, Manufacturers are therefore advised to install
proper design mechanism for the rainwater harvest.
Project design process
Residential building contributes to a high consumption of water pattern due to its urgency
for usage not only in Australian residential buildings but also across the world. The essentiality
of water for home usage has raised concerns especially in the highly populated regions such as
the developing world where clean and fresh water is in short supply as a result of poor water
management and drought (Ward, et al., 2010). With unabated demand of this unique and scarce
resource, which cannot be substituted by any other product for its specific purpose, has raised
concerns on implementing alternative methods of acquiring this natural resource that is already
limited per our needs (Palla, et al., 2011). This is because the water supply is not adequate as per
our requirement. The demand and supply gap increasingly widening day by day and is even
predicted to become worse in the near future.

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Figure 1; The Global water Distribution
Source: (Dkhar, 2012)
Application of the rain water harvesting system
Functions
The function of the harvested rainwater include drinking water, washing, flushing toilets,
watering the plants, and many other uses. Atmospheric pollutants such as infrequent rains,
vegetation hanging, roof materials, dust accumulation, and bird and rodent droppings can be
carried along with the rainwater from the roof (Jones & Hunt, 2010). It therefore means that, if
the water is to be used for drinking purposes, it has to be treated in accordance with the
Australian Drinking Water guidelines as stated in the National Health and Medical Research
Council. Water treatment methods that can be employed in the system but not limited to debris
filtration, and purification methods such as UV treatment or chlorination to achieve the purpose
of disinfection (Otti & Ezenwaji, 2013).

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Figure 2: Indoor household use
Source: AWWA Research Foundation
Figure 3: typical plumbing design of Rainwater Utilisation in residential building
Source: google images

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Functional unit
The main components of rain water harvesting system include; conveyance, storage,
overflow, outlet, and delivery. The conveyance system is composed of a series of gutters,
downspouts and downpipes that direct the water collected from the roof to the storage tank or the
cistern. The water harvested will service a four storey residential high rise building. Water will
be supplied to the building from two pipes of 0.5 inch diameter each.
The typical consumption of water in the building is indicated below;
Figure 4: Area of water consumption in the building
Source: (Dkhar, 2012)

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Figure 5: Water Consumption on every floor of the building
Source: (Dkhar, 2012)

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The total amount of water consumption of the building per day is 38,183 litres
Process flow diagram for rainwater harvest
Figure 6: Rainwater harvest
Source: (Jothiprakash & Sathe, 2009)
A more detailed control centre of the rainwater purification mechanism is as shown in appendix
A
Figure 7: schematic showing water flow from the tank storage to their end use in the different
floors of the building Source: (Dkhar, 2012)

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Inventory Analysis
Data collection
Rainwater harvesting in residential buildings
Input Material category Unit Quantity
Acid rain water Elementary flow gallons
Roofing material e.g. sheet, tile or
shingle roof
Elementary flow foot
Gutters Elementary flow foot
Storage tank Elementary flow gallons
All necessary pipes and fittings Elementary flow inches
Cartridge filter Elementary flow Inch
Reverse osmosis filter Elementary flow Inch
UV light disinfection Intermediate product g
Ozone disinfection Intermediate product g
Chlorine disinfection Intermediate product g
Floating filter intake Elementary flow Inch
Pump controller Elementary flow Inch
Fuel Intermediate product Kg
Oxygen Intermediate product Kg
Overflow siphon Elementary flow Inch
First flush diverter Elementary flow Inch
Down spout debris diverter Elementary flow Inch
Valves Elementary flow Inch

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Vent cap Elementary flow Area
Output Material category Unit Quantity
Pure water Intermediate product gallons
Debris e.g. leaves Intermediate product g
Residual solid materials Intermediate product g
Overflow water Elementary flow Gallons
CO2 emission Elementary flow Kg
Hydrogen chloride emission to the
atmosphere
Elementary flow g

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Quality Data Assessment
Inventory
item
Time
related
coverage
Geographical
coverage
Technology
coverage
Foreground
precision
completeness consistency productivity
Pure water 2019 Very good Very good average Very good Very good Very good
Debris e.g.
leaves
good good Very good good good good
Residual
solid
materials
Average good Very good good good average
Overflow
water
Very good Very good good Very good good Very good
CO2
emission
good Very good average Very good good Very good
Hydrogen
chloride
emission to
the
atmosphere
poor good good Very good good average
Cut off criteria
• Mass: Exclude flows that are < 2% of the cumulative mass of all the inputs and outputs
• Energy: Exclude flows that are < 2% of the cumulative energy of all the inputs and
outputs
• Environmental relevance: Include flows that potentially have a significant environmental
impact, even if they meet the above criteria

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• The sum of the excluded flows shall not exceed 2% of mass, energy or environmental
relevance
Conclusion
Designing a sustainable rainwater harvesting system for the residential building requires
workable functional unit that comprise of a processing unit that have both the elementary and
intermediate flow of materials, energy, emissions and other releases. The functional unit for
rainwater harvesting will contain a storage tank, pump, regulating valves, filtration system, and
sanitation stage in order to produce a pure product which is safe and ready for use. During the
design process, it is important to identify the material systems, their usage in the system, their
units and quantity just like the ones identified in the discussion above on rainwater harvest. In
order to make the design concept of RWH a success, quality assessment need to be done to
ensure that the process works effectively, as such certain allowable limits in the design need to
be followed to ensure that the work done is within the cut off criteria. Future research need to be
carried out in order to improve the quality of rainwater harvest and supplementing the most
favoured roof water harvesting with the surface water harvesting.

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References
Aladenola OO, Adeboye OB 2010, Assessing the potential for Rainwater Harvesting, Water
Resource Management, Vol. 24 992129-2137, Springer Science
Chiu Y., Liaw C. and Chen L. 2009. Optimizing rainwater harvesting systems as an innovative
approach to saving energy in hilly communities. Renewable Energy. (34):
492-498.
Jones, M.P. and Hunt, W.F., 2010. Performance of rainwater harvesting systems in the
southeastern United States. Resources, Conservation and Recycling, 54(10), pp.623-629.
Jothiprakash V., and Mandar V. Sathe. 2009. Evaluation of rainwater harvesting methods and
structures using analytical hierarchy process for a large scale industrial area. Journal of Water
Resources and Protection, Vol. 1, No. 6, pp 427-438
Li Z., Boyle F. and Reynolds A. 2010. Rainwater harvesting and grey water treatment systems
for domestic application in Ireland. Desalination. 260: 1- 8.
Mun, J.S. and Han, M.Y., 2012. Design and operational parameters of a rooftop rainwater
harvesting system: definition, sensitivity and verification. Journal of Environmental
Management, 93(1), pp.147-153.
Otti V. I., Ezenwaji E.E. 2013. Enhancing Community-Driven Initiative in Rainwater Harvesting
in Nigeria. International Journal of Engineering and Technology Volume 3 No. 1, January, 2013
Palla, A., Gnecco, I. and Lanza, L.G., 2011. Non-dimensional design parameters and
performance assessment of rainwater harvesting systems. Journal of Hydrology, 401(1-2), pp.65-
76.

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Ward, S., Memon, F.A. and Butler, D., 2010. Rainwater harvesting: model-based design
evaluation. Water Science and Technology, 61(1), pp.85-96.

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Appendix
Appendix A: Control center for rainwater harvest