Rain Water Harvesting System

Abstract
Rainwater harvesting, the small-scale collection and storage of runoff for irrigated agriculture, is recognized
as a sustainable strategy for ensuring food security, especially in monsoonal landscapes in the developing
world. In south India, these strategies have been used for millennia to mitigate problems of water scarcity.
However, in the past 100 years many traditional rainwater harvesting systems have fallen into disrepair due
to increasing dependence on groundwater. With elevated declines in groundwater resources, there is
increased effort at the state and national levels to revive older systems. Critical to the success of such efforts
is an improved understanding of how these ancient water-provisioning systems function in contemporary
landscapes with extensive groundwater pumping and shifted climatic regimes. Knowledge is especially
lacking regarding the water-exchange dynamics of these rainwater harvesting “tanks” at tank and catchment
scales, and how these exchanges regulate tank performance and catchment water balances. Here, we use
fine-scale water level variations to quantify daily fluxes of groundwater, evapotranspiration, and sluice
outflows in four tanks over the 2013 northeast monsoon season in a tank cascade that covers a catchment
area of 28.2 km2. Our results indicate a distinct spatial pattern in groundwater-exchange dynamics, with the
frequency and magnitude of groundwater inflow events (as opposed to outflow) increasing down the cascade
of tanks. The presence of tanks in the landscape dramatically alters the catchment water balance, with
catchment-scale runoff: rainfall ratios decreasing from 0.29 without tanks to 0.04 – 0.09 with tanks.
Recharge: rainfall ratios increase in the presence of tanks, from ~0.17 in catchments without tanks to ~ 0.26
in catchments with tanks. Finally, our results demonstrate how more efficient management of sluice
outflows can lead to the tanks meeting a higher fraction of crop water requirements.

Department of EEE 1 ATME College of engineering, Mysore

 Rain Water Harvesting System

Introduction on Rain Water Harvesting

Rainwater harvesting is the accumulation and storage of rainwater for reuse on-site, rather than
allowing it to run off. Rainwater can be collected from rivers or roofs, and in many places, the water
collected is redirected to a deep pit (well, shaft, or borehole), a reservoir with percolation, or collected from
dew or fog with nets or other tools. Its uses include water for gardens, livestock, irrigation, domestic use
with proper treatment, indoor heating for houses, etc. The harvested water can also be used as drinking
water, longer-term storage, and for other purposes such as groundwater recharge.

Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for
households usually financed by the user

Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops, the
land surface or rock catchments using simple techniques such as jars and pots as well as more complex
techniques such as underground check dams. The techniques usually found in Asia and Africa arise from
practices employed by ancient civilizations within these regions and still serve as a major source of drinking
water supply in rural areas. Commonly used systems are constructed of three principal components; namely,
the catchment area, the collection device, and the conveyance system

Objective:
Rainwater harvesting is the collection and storage of precipitation for later human use. This project focuses
on the design, construction and analysis of a rainwater harvesting system located at the Bourns College of
Engineering at the University of California, Riverside. The information collected from this project will be
used to build a template for designing a rain water harvesting system that can be placed in areas outside of
the Southern California region, with a specific look at the applicability of rain water harvesting in
developing regions.

A preliminary mathematical model was created using Microsoft Excel that can be used to determine the
potential volume of rainwater captured from an inputted rooftop area. Besides providing the volume of water
that could be potentially collected from a rain event, the Excel model outputs the estimated total cost of
installation and the amount of days harvested water can be used to irrigate a given lawn area. The collected
data from the Phase I design will provide an opportunity to optimize the Excel model, taking into
consideration local conditions and equipment costs.

Phase I funding was used to construct a harvesting system around one drain spout located at the Bourns
College site. To come up with a preliminary design of the system the Excel model was used to come up with
a tank size based on local rainfall data. The system includes a catch basin connected to a roof outlet, which
flows over a weir and flow meter. An auto-sampler is also connected to the system to take grab samples. The
water is tested for total suspended solids and total dissolved solids.

Department of EEE 2 ATME College of engineering, Mysore

 Rain Water Harvesting System

History of rain water harvesting

The construction and use of cisterns to store rainwater can be traced back to the Neolithic Age, when
waterproof lime plaster cisterns were built in the floors of houses in village locations of the Levant, a large
area in Southwest Asia, south of the Taurus Mountains, bound by the Mediterranean Sea in the west, the
Arabian Desert in the south, and Mesopotamia in the east. By the late 4000 BC, cisterns were essential
elements of emerging water management techniques used in dry-land farming.

Rainwater harvesting was also common in the Roman Empire. While Roman Aqueducts are well-
known, Roman cisterns were also commonly used and their construction expanded with the Empire. For
example, in Pompeii, rooftop water storage was common before the construction of the Aqueduct in the 1st
century BC. This history continued with the Byzantine Empire, for example the Basilica Cistern in Istanbul.

Though little-known, for centuries the town of Venice depended on rainwater harvesting. The lagoon
which surrounds Venice is brackish water, which is not suitable for drinking. The ancient inhabitants of
Venice established a system of rainwater collection which was based on man-made insulated collection
wells. Water percolated down the specially designed stone flooring, and was filtered by a layer of sand, then
collected at the bottom of the well. Later, as Venice acquired territories on the mainland, it started to import
water by boat from local rivers, but the wells remained in use, and were especially important in time of war
when access to the mainland water could be blocked by an enemy.

Rain water invented:

Rainwater harvesting has been around since nearly 2000 BCE thanks to ancient civilizations like India,
China, and Mesopotamia. However, the process evolved throughout time, in part because of the technologies
employed by ancient Rome.

Ancient Indians collected rainwater a top their houses. They also employed reservoir and dam systems. In
Mesopotamia and China, inhabitants would collect rain in cisterns, and these would be stored underground.
Such waters could be accessible during dry seasons.

Ancient Romans would also collect rainwater’s in cisterns. They were also able to irrigate waters to various
areas.

Department of EEE 3 ATME College of engineering, Mysore

 Rain Water Harvesting System

Defining Rain water harvesting

The process of collecting, storing and using the rain water where it falls either from a roof top or from land
surface is called rain water harvesting

Reasons for rainwater harvesting: Why

1 Increasing water needs/demands

 The rapid rise in human population has made optimum use of fresh water imperative.
 Urban water supply systems in particular are under tremendous pressure to meet the needs of the
population as well as industry and large-scale construction.
 The increased need for water results in lower groundwater table sand depleted reservoirs. Many
piped water supply systems fail.
 Consumption of polluted water is beset with health hazards.
 The use of rainwater is a useful alternative

2 Variations in water availability

 The availability of water from sources such as lakes, rivers and shallow ground water can fluctuate
strongly.
 Unchecked rainwater runoff is causing soil erosion.
 Collecting and storing rain water can provide water for domestic use in periods of water shortage.
 Rainwater may also provide a solution when the water quality is low or varies during the rainy
season in rivers and other surface water resources (for example in Bangladesh).

3 Responsibilities towards protecting Nature

 Using more of rainwater helps to conserve & augment the storage of ground water
 It helps to arrest sea water intrusion in coastal areas
 It helps to avoid flood & water stagnation in urban areas
 Reduces water and electricity bills

4 Advantage of collection and storage near the place of use

 Traditional sources are located at some distance from the community. Collecting and storing water
close to households improves the accessibility and convenience of water supplies and has a positive
impact on health.
 It costs less to collect rainwater than to exploit groundwater.
 Only traditional knowledge, skills and materials can be used to collect the water and no government
technical assistance is required for repair and maintenance.
 Collecting rainwater is the only way of recharging water sources and revitalizing dry open wells and
dry hand pumps.
 It can also strengthen a sense of ownership. It gives an opportunity for communities to come together
and work closer. It allows for the decentralized control and community management of water.
 It will provide productive employment to the rural poor in their own villages.

Department of EEE 4 ATME College of engineering, Mysore

 Rain Water Harvesting System

5 Quality of water supplies

 Water supplies can become polluted either through industrial or human wastes or by intrusion of
minerals such as arsenic, salt (coastal area) or fluoride.
 Rainwater is the ultimate fresh water.
 Rainwater is generally of good quality.

Reasons for rainwater harvesting: When

 Rain water harvesting measures are essential when the ground water is brackish or has a high Iron or
Fluoride content.
 Rain water harvesting measures should begin four months before the monsoon is to arrive.
 Concentrated water demand in urban areas for various purposes like household, institutions (e.g.
schools and colleges, hospitals, offices, markets and shopping malls), factories, and even water parks

Health benefits
 In many part of the country the ground water contains high amount of dissolved solids like fluorides
which are detrimental to health .rain water harvesting could emerge as a sustainable alternative.
 High dissolved solids in ground water also lead to hair loss. Poor lather for washing. Spoilage of cooked
food, scaling of vessels, pipingetc which can be reduced by rain water harvesting.
 Places where bacterial contaminated is high in ground and surface water, rain water harvesting could be a
healthy alternative.
 It reduces drudgery to women who do back breaking job of drawing and carrying water in the villages.

Data base of rain fall

Rain fall in mm (annual) From roof top every 100M For every one acres of land
(100Sft) @ 80% collection available of Rainwater
efficiency @30% collection efficiency

500 40,000 6,00,000

1000 80,000 12,00,000
1500 1,20,000 18,00,000
2000 1,60,000 24,00,000
2500 2,00,000 30,00,000

Department of EEE 5 ATME College of engineering, Mysore

 Rain Water Harvesting System

Methods of Rainwater Harvesting

Broadly there are two ways of harvesting rainwater

1. Surface runoff harvesting

2. Roof top rainwater harvesting

Rainwater harvesting is the collection and storage of rainwater for reuse on-site, rather than allowing it to
run off. These stored waters are used for various purposes such as gardening, irrigation etc. Various methods
of rainwater harvesting are described in this section.

1. Surface runoff harvesting

In urban area rainwater flows away as surface runoff. This runoff could be caught and used for recharging
aquifers by adopting appropriate methods.

Surface runoff (also known as overland flow) is the flow of water that occurs when excess storm water, melt
water, or other sources flows over the Earth's surface. This might occur because soil is saturated to full
capacity, because rain arrives more quickly than soil can absorb it, or because impervious areas (roofs and
pavement) send their runoff to surrounding soil that cannot absorb all of it. Surface runoff is a major
component of the water cycle. It is the primary agent in soil erosion by water.

Runoff that occurs on the ground surface before reaching a channel is also called a nonpoint source. If a
nonpoint source contains man-made contaminants, or natural forms of pollution (such as rotting leaves) the
runoff is called nonpoint source pollution. A land area which produces runoff that drains to a common point
is called a drainage basin. When runoff flows along the ground, it can pick up soil contaminants including
petroleum, pesticides, or fertilizers that become discharge or nonpoint source pollution.[3]

In addition to causing water erosion and pollution, surface runoff in urban areas is a primary cause of urban
flooding which can result in property damage, damp and mold in basements, and street flooding

2. Rooftop rainwater harvesting

It is a system of catching rainwater where it falls. In rooftop harvesting, the roof becomes the
catchments, and the rainwater is collected from the roof of the house/building. It can either be stored in a
tank or diverted to artificial recharge system. This method is less expensive and very effective and if
implemented properly helps in augmenting the groundwater level of the area.

Department of EEE 6 ATME College of engineering, Mysore

 Rain Water Harvesting System

Components of the Rooftop Rainwater Harvesting

The illustrative design of the basic components of roof top rainwater harvesting system is given in figure

Fig 1: Components of Rainwater Harvesting

The system mainly constitutes of the following sub components

 Catchments
 Transportation
 First flush
 Filter

Catchments
The surface that receives rainfall directly is the catchment of rainwater harvesting system. It may be
terrace, courtyard, or paved or unpaved open ground. The terrace may be flat RCC/stone roof or sloping
roof. Therefore the catchment is the area, which actually contributes rainwater to the harvesting system.

Transportation
Rainwater from rooftop should be carried through down take water pipes or drains to storage/harvesting
system. Water pipes should be UV resistant (ISI HDPE/PVC pipes) of required capacity. Water from
sloping roofs could be caught through gutters and down take pipe. At terraces, mouth of the each drain
should have wire mesh to restrict floating material.

First Flush
First flush is a device used to flush off the water received in first shower. The first shower of rains needs
to be flushed-off to avoid contaminating storable/rechargeable water by the probable contaminants of the
atmosphere and the catchment roof. It will also help in cleaning of silt and other material deposited on
roof during dry seasons Provisions of first rain separator should be made at outlet of each drainpipe.

Department of EEE 7 ATME College of engineering, Mysore

 Rain Water Harvesting System

Filter
There is always some skepticism regarding Roof Top Rainwater harvesting since doubts are raised that
rainwater may contaminate groundwater. There is remote possibility of this fear coming true if proper
filter mechanism is not adopted.

Secondly all care must be taken to see that underground sewer drains are not punctured and no leakage is
taking place in close vicinity.

Filters are used for treatment of water to effectively remove turbidity, colour and microorganisms. After first
flushing of rainfall, water should pass through filters. A gravel, sand and ‘netlon’ mesh filter is designed and
placed on top of the storage tank. This filter is very important in keeping the rainwater in the storage tank
clean. It removes silt, dust, leaves and other organic matter from entering the storage tank.

The filter media should be cleaned daily after every rainfall event. Clogged filters prevent rainwater from
easily entering the storage tank and the filter may overflow. The sand or gravel media should be taken out
and washed before it is replaced in the filter.

A typical photograph of filter is shown in Fig 2.

There are different types of filters in practice, but basic function is to purify water. Different types of filters
are described in this section.

Sand Gravel Filter

These are commonly used filters, constructed by brick masonry and filleted by pebbles, gravel, and sand as
shown in the figure. Each layer should be separated by wire mesh. A typical figure of Sand Gravel Filter is
shown in Fig 3.

Fig 3: Sand Gravel Filter

Department of EEE 8 ATME College of engineering, Mysore

 Rain Water Harvesting System

Charcoal Filter

Charcoal filter can be made in-situ or in a drum. Pebbles, gravel, sand and charcoal as shown in the figure
should fill the drum or chamber. Each layer should be separated by wire mesh. Thin layer of charcoal is used
to absorb odor if any. A schematic diagram of Charcoal filter is indicated in Fig 4.

Fig 4: Charcoal Filter

PVC –Pipe filter

This filter can be made by PVC pipe of 1 to 1.20 m length; Diameter of pipe depends on the area of roof. Six
inches dia. pipe is enough for a 1500 Sq. Ft. roof and 8 inches dia. pipe should be used for roofs more than
1500 Sq. Ft. Pipe is divided into three compartments by wire mesh.

Each component should be filled with gravel and sand alternatively as shown in the figure. A layer of
charcoal could also be inserted between two layers. Both ends of filter should have reduced of required size
to connect inlet and outlet. This filter could be placed horizontally or vertically in the system. A schematic
pipe filter is shown in Fig 5.

Fig 5: PVC-Pipe filter

Department of EEE 9 ATME College of engineering, Mysore

 Rain Water Harvesting System

Methods of Rooftop Rainwater Harvesting

Various methods of using roof top rainwater harvesting are illustrated in this section.

a) Storage of Direct Use

In this method rainwater collected from the roof of the building is diverted to a storage tank. The storage
tank has to be designed according to the water requirements, rainfall and catchment availability.

Each drainpipe should have mesh filter at mouth and first flush device followed by filtration system before
connecting to the storage tank. It is advisable that each tank should have excess water over flow system.

Excess water could be diverted to recharge system. Water from storage tank can be used for secondary
purposes such as washing and gardening etc. This is the most cost effective way of rainwater harvesting.

The main advantage of collecting and using the rainwater during rainy season is not only to save water from
conventional sources, but also to save energy incurred on transportation and distribution of water at the
doorstep. This also conserves groundwater, if it is being extracted to meet the demand when rains are on. A
typical fig of storage tank is shown in Fig 7.

Fig 7: A storage tank on a platform painted white

b) Recharging groundwater aquifers

Groundwater aquifers can be recharged by various kinds of structures to ensure percolation of rainwater in
the ground instead of draining away from the surface. Commonly used recharging methods are:-

a) Recharging of bore wells

b) Recharging of dug wells.

c) Recharge pits

d) Recharge Trenches

e) Soak ways or Recharge Shafts

f) Percolation Tanks

Department of EEE 10 ATME College of engineering, Mysore

 Rain Water Harvesting System

c) Recharging of bore wells

Rainwater collected from rooftop of the building is diverted through drainpipes to settlement or filtration
tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers. Abandoned bore
wells can also be used for recharge.

Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of catchment,
intensity of rainfall and recharge rate. While recharging, entry of floating matter and silt should be restricted
because it may clog the recharge structure.

First one or two shower should be flushed out through rain separator to avoid contamination. A schematic
diagram of filtration tank recharging to bore well is indicated in Fig 8.

Fig 8: Filtration tank recharging to bore well

d) Recharge pits

Recharge pits are small pits of any shape rectangular, square or circular, contracted with brick or stone
masonry wall with weep hole at regular intervals. Top of pit can be covered with perforated covers. Bottom
of pit should be filled with filter media.

The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and recharge rate of
soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m deep depending on the depth of
pervious strata.

These pits are suitable for recharging of shallow aquifers, and small houses. A schematic diagram of
recharge pit is shown in Fig 9

Department of EEE 11 ATME College of engineering, Mysore

 Rain Water Harvesting System

Fig 9: Recharge pit

e) Soak ways or Recharge shafts

Soak away or recharge shafts are provided where upper layer of soil is alluvial or less pervious. These are
bored hole of 30 cm dia. up to 10 to 15 m deep, depending on depth of pervious layer. Bore should be lined
with slotted/perforated PVC/MS pipe to prevent collapse of the vertical sides.

At the top of soak away required size sump is constructed to retain runoff before the filters through soak
away. Sump should be filled with filter media. A schematic diagram of recharge shaft is shown in Fig 10.

Fig 10: Schematic Diagram of Recharge shaft

f) Recharging of dug wells

Dug well can be used as recharge structure. Rainwater from the rooftop is diverted to dig wells after passing
it through filtration bed. Cleaning and desalting of dug well should be done regularly to enhance the
recharge rate. The filtration method suggested for bore well recharging could be used. A schematic diagram
of recharging into dug well is indicated in Fig 11 shown below.

Department of EEE 12 ATME College of engineering, Mysore

 Rain Water Harvesting System

Fig 11: Schematic diagram of recharging to dug well

G) Recharge trenches

Recharge trench in provided where upper impervious layer of soil is shallow. It is a trench excavated on the
ground and refilled with porous media like pebbles, boulder or brickbats. It is usually made for harvesting
the surface runoff.

Bore wells can also be provided inside the trench as recharge shafts to enhance percolation. The length of
the trench is decided as per the amount of runoff expected.

This method is suitable for small houses, playgrounds, parks and roadside drains. The recharge
trench can be of size 0.50 to 1.0 m wide and 1.0 to 1.5 m deep. A schematic diagram of recharging to
trenches is shown in Fig below 12.

Fig 12: Recharging to trenches

h) Percolation tank

Percolation tanks are artificially created surface water bodies, submerging a land area with adequate
permeability to facilitate sufficient percolation to recharge the groundwater. These can be built in big
campuses where land is available and topography is suitable

Department of EEE 13 ATME College of engineering, Mysore

 Rain Water Harvesting System

Quality of Rain Water

Rainwater may need to be analyzed properly, and used in a way appropriate to its safety. In the Gansu
province for example, solar water disinfection is used by boiling harvested rainwater in parabolic solar
cookers before being used for drinking. These so-called "appropriate technology" methods provide low-cost
disinfection options for treatment of stored rainwater for drinking.

While rainwater itself is a clean source of water, often better than groundwater or water from rivers or lakes,
the process of collection and storage often leaves the water polluted and non-potable. Rainwater harvested
from roofs can contain human, animal and bird feces, mosses and lichens, windblown dust, particulates from
urban pollution, pesticides, and inorganic ions from the sea (Ca, Mg, Na, K, Cl, SO4), and dissolved gases
(CO2, NOx, SOx). High levels of pesticide have been found in rainwater in Europe with the highest
concentrations occurring in the first rain immediately after a dry spell, the concentration of these and other
contaminants are reduced significantly by diverting the initial flow of run-off water to waste. Improved
water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the
tank) and by using a series of tanks, withdraw from the last in series. Pre-filtration is a common practice
used in the industry to keep the system healthy and ensure that the water entering the tank is free of large
sediments.

Conceptually, a water supply system should match the quality of water with the end use. However, in most
of the developed world, high-quality potable water is used for all end uses. This approach wastes money and
energy and imposes unnecessary impacts to the environment. Supplying rainwater that has gone through
preliminary filtration measures for non-portable water uses, such as toilet flushing, irrigation and laundry,
may be a significant part of a sustainable water management strategy.

Department of EEE 14 ATME College of engineering, Mysore

 Rain Water Harvesting System

Current uses of rain water harvesting in the world

 Canada

 India

 Israel

 New Zealand

 Sri Lanka

 South Africa

 United Kingdom

 In India, Tamil Nadu was the first state to make rainwater harvesting compulsory for every building to
avoid groundwater depletion. The scheme was launched in 2001 and has been implemented in all
rural areas of Tamil Nadu. Posters all over Tamil Nadu including rural areas create awareness about
harvesting rainwater TN Government site. It gave excellent results within five years, and slowly
every state took it as a role model. Since its implementation, Chennai had a 50% rise in water level
in five years and the water quality significantly improved.

 Karnataka: In Bangalore, adoption of rainwater harvesting is mandatory for every owner or the
occupier of a building having the site area measuring 60 ft (18.3 m) × 40 ft (12.2 m) and above and
for newly constructed building measuring 30 ft (9.1 m) × 40 ft (12.2 m) and above dimensions. In
this regard, Bangalore Water Supply and Sewerage Board has initiated and constructed “Rain Water
Harvesting Theme Park” in the name of Sir M. Visvesvaraya in 1.2 acres (4,900 m2) of land situated
at Jayanagar, Bangalore. In this park, 26 different type of rainwater harvesting models are
demonstrated along with the water conservation tips. An attempt has been made at the Department of
Chemical Engineering, IISc, Bangalore to harvest rainwater using upper surface of a solar still,
which was used for water distillation

 In Rajasthan, rainwater harvesting has traditionally been practiced by the people of the Thar Desert.
Many ancient water harvesting systems in Rajasthan have now been revived. Water harvesting
systems are widely used in other areas of Rajasthan, as well, for example the chauka system from the
Jaipur district.

 Maharashtra: At present, in Pune, rainwater harvesting is compulsory for any new housing society to
be registered.

 In Mumbai, Maharashtra, rainwater harvesting is being considered as a good solution to solve the
water crisis.

 The Mumbai City council is planning to make rainwater harvesting mandatory for large societies.

Department of EEE 15 ATME College of engineering, Mysore

 Rain Water Harvesting System

Advantages of Rainwater Harvesting

 Easy to Maintain
 Reducing Water Bills

 Suitable for Irrigation

 Reduces Demand on Ground Water

 Reduces Floods and Soil Erosion

 Can be Used for Several Non-drinking Purposes

Disadvantages of Rainwater Harvesting

 Unpredictable Rainfall
 Initial High Cost
 Regular Maintenance
 Certain Roof Types may Seep Chemicals or Animal Droppings
 Storage Limits

Department of EEE 16 ATME College of engineering, Mysore

 Rain Water Harvesting System

Applications of rainwater harvesting

Agriculture

Missions to six Caribbean countries have shown that the capture and storage of rainwater runoff for
later use is able to significantly reduce the risk of losing some or all of the year's harvest because of soil or
water scarcity. In addition, the risks associated with flooding and soil erosion during high rainfall seasons
would decrease. Small farmers, especially those farming on hillsides, could benefit the most from rainwater
harvesting because they are able to capture runoff and decrease the effects of soil erosion.

Many countries, especially those with arid environments, use rainwater harvesting as a cheap and
reliable source of clean water. To enhance irrigation in arid environments, ridges of soil are constructed to
trap and prevent rainwater from running down hills and slopes. Even in periods of low rainfall, enough
water is collected for crops to grow. Water can be collected from roofs, dams and ponds can be constructed
to hold large quantities of rainwater so that even on days when little to no rainfall occurs, enough is
available to irrigate crops.

Domestic use

 In China, Argentina, and Brazil, rooftop rainwater harvesting is used to provide drinking water,
domestic water, water for livestock, water for small irrigation, and a way to replenish groundwater
levels. Gansu province in China and semiarid northeast Brazil have the largest rooftop rainwater
harvesting projects going on.
 About 40% of Thailand's rural population utilizes rainwater harvesting. Rainwater harvesting was
promoted heavily by the government in the 1980s. In the 1990s, after government funding for the
collection tanks ran out, the private sector stepped in and provided several million tanks to private
households, many of which continue to be used today. This is one of the largest examples of self-
supply of water worldwide.
 Rainwater harvesting is mandatory for new homes built in Santa Fe, New Mexico.
 Texas offers a sales tax exemption for the purchase of rainwater harvesting equipment.
 Both Texas and Ohio allow rainwater harvesting to be used even for potable purposes.
 Oklahoma passed the Water for 2060 Act in 2012, to promote pilot projects for rainwater and gray
water use among other water-saving techniques.
 In the United Kingdom, water butts are often found in domestic gardens and on allotments to collect
rainwater, which is then used to water the garden.

Industry

Frankfurt Airport has the biggest rainwater harvesting system in Germany. The system helps save
approximately 1 million cubic meters of water per year. The cost of the system was 1.5 million dm (US
$63,000) in 1993. The system collects water from roofs of the new terminal which has an area of 26,800
square meters. The water is collected in the basement of the airport in six tanks with a storage capacity of
100 cubic meters. The water is mainly used for toilet flushing, watering plants and cleaning the air
conditioning system.

Rainwater harvesting was adopted at The Velodrome – The London Olympic Park – in order to
increase the sustainability of the facility. A 73% decrease in potable water demand by the park was
estimated. Despite this, it was deemed that rainwater harvesting was a less efficient use of financial
resources to increase sustainability than the park's black water recycling program.

Department of EEE 17 ATME College of engineering, Mysore

 Rain Water Harvesting System

Survey of Rain Water Harvesting Projects

To assess the information and survey is done in Mysuru of rainwater harvesting structures on roof top rain
water in surrounding area, a team of students from ATME College of engineering, visited the Projects in
NIE Crest and KSIC silk factory on 09-10 2018

Project Survey Visit no: 1

NIE Centre for renewable energy & sustainable energy

The demo of rain water harvesting is shown in above figure. In this the method it is used roof top
rain water harvesting. The method is explaining by Mr. S.Shamsundar teammate and good explanation is given
by him. Then the working is shown below

Components used in Rain Water Harvesting in NIE CREST

1. Catchments or roof surface.
2. Delivery system
3. Filter
4. Storage reservoir

Block Diagram of Rain Water Harvesting System in NIE CREST

Department of EEE 18 ATME College of engineering, Mysore

 Rain Water Harvesting System

1. Catchments
In this the rain water is collected on the roof top and flows towards the delivery system. When the
rain fall occurs the rain drop will flow towards one direction and the rain water is collected.
2. Delivery system
The rain water which is collected will flow towards the filter. The delivery system which is
connected to the catchment and filter. The water which is collected from rain will flow through the pipe
to the filter.
3. Filters
The filter which will purify the water of rain from which the water is collected through the delivery
System.
4. Storage Reservoirs
The rain water which is collected and filtered will store in a tank. Then it will be used for gardens
domestic use, industries depending on capacity of storage of water in liters.

Working of rain water harvesting in NIE CREST

When the rain occurs the rain droplets will flow towards the roof surface then it will flow
towards in one direction. Then the water is collected. The water will flow through the delivery system and a
funnel type mesh will be presented at the end of delivery system. Then the water will flow towards to tank 1
Then dust will settle down in tank 1. After the filling of tank1 then tank2 starts filling with the help of filter
Tank2 starts filling by this water is stored in storage tank. In the filter the fist layer is fully sponge, second
layer is filled sand and third layer is filled with pebbles. By the three layer the rain water is purified and
stored in the tank

On the basis of data base of rain depends on the storage. Mysore district receives an average rainfall
of 776.7mm. There are 53 rainy days in the district on average about 50% of annual rainfall occurs during
the southwest monsoon period the rainfall generally decreases from west to east.

When the team of students visited to the NIE Crest is shown in below

Department of EEE 19 ATME College of engineering, Mysore

 Rain Water Harvesting System

Project Survey Visit no: 2

KSIC Silk weaving factory

The above figure shows the entrance of KSIC silk weaving factory. In the factory the team visited
the project of rain water harvesting. In this the project storage is around 1000 liters. They are using for
garden/plantation. Below figure shows the rain water harvesting project

Department of EEE 20 ATME College of engineering, Mysore

 Rain Water Harvesting System

When the team visited KSIC Silk weaving factory the rain water harvesting team member Manjunath
explained. In this they use factory waste water is also used.
The explanation is giving by Manjunath on rain water harvesting to the team shown below

Block Diagram of Rain Water Harvesting System in KSIC Silk weaving factory

Department of EEE 21 ATME College of engineering, Mysore

 Rain Water Harvesting System

Components used in rain water harvesting in KSIC silk factory

1. Bar screen chamber
2. Equalization tank
3. Aeration tank
4. Settling tank
5. Pre-filtration tank
6. PSF(Pressure sand filter)
7. ACF(Activated Carbon filter)
8. Post-filtration tank

Bar screen chamber: - A bar screen is mechanical filter used to remove large objects, such as rags and
plastics, from waste water. Bar screens come in many designs. Some employ automatic cleaning
mechanisms using electric motors and chains, some must be cleaned manually by means of heavy rake.

Equalization tank: - The basins are designed to provide consistent influent flow to downstream processes.
Due to the additional retention time, aeration and mixing is required in equalization basins to prevent the
raw waste water from becoming septic and to maintain solids in suspension.

Aeration tank: - In this tank where the air is injected in the mixed liquor. The tank which will inject oxygen
to the liquor to allow biological flocs.

Settling tank: - Sedimentation tank, also called settling tank or clarifier, component of a modern system of
water supply or wastewater treatment. A sedimentation tank allows suspended particles to settle out of water
or wastewater as it flows slowly through the tank, thereby providing some degree of purification.

Department of EEE 22 ATME College of engineering, Mysore

 Rain Water Harvesting System

Pre-filtration tank: -A pre-filter is used to remove the dirt, debris, and organic water. Most all filters work
on an efficiency principle, which means that depending on flow rate, all or a portion of water is filtered
before entering the storage tank.

PSF (Pressure sand filter): - The pressure sand filter consists of a multiple layer of sand with a variety in
size and specific gravity. These filters are designed to remove turbidity and suspended particles present in
the feed water with minimum pressure drop. These filters are custom designed to suit the process
requirement.

ACF (Activated carbon filter): - Carbon filtering is a method of filtering that uses a bed of activated
carbon to remove contaminants and impurities, using chemical adsorption. Active charcoal carbon filters are
most effective at removing chlorine, particles such as sediment, volatile organic compounds (VOCs), taste
and odor from water.

Post-filtration tank: - After the filtration the chlorine is added to remove the dust particles and clear water
will be stored

Working of rain water harvesting in KSIC Silk weaving factory

The working of rain water harvesting system is the rain water is stored in tank and moved to the bar
screen chamber to remove the large objects like plastics, rags etc; to remove large particle by the waste
water of the factory is combined to the rain water. For this the bar screen chamber is used. Then it is moved
to the equalization tank is feeded. It will provide consistent influent flow to downstream processes. Then it
is feeded to the aeration tank. When it is feeded the air (oxygen) is injected to the tank. Then it will make
into biological flocs and it is feeded to the settling tank. It is also called as sedimentation tank. A
sedimentation tank allows suspended particles to settle out of water or wastewater as it flows slowly through
the tank, thereby providing some degree of purification. The output of water is again it is feeded to the
aeration tank it will be same as procedure and it will be feeded to the pre filtration tank. It is used to remove
the dirt, debris, and organic water. The purification process will be at 60% then it is feeded to the pressure
sand filter (PSF). The filter will remove turbidity and suspended particles present in the feed water with
minimum pressure drop and it is moved to the activated carbon filter (ACF). The Carbon filtering is a
method of filtering that uses a bed of activated carbon to remove contaminants and impurities, using
chemical adsorption. Then the both purification in PSF & ACF will be back washed to the bar screen
chamber and repeated the same procedure. And after the ACF process the purification process will be in
90%. The last filter is post filtration tank. In this the filtration process the chlorine is added to remove the
dust particles and clear water will be stored then it will be used for gardening/plantation.

Department of EEE 23 ATME College of engineering, Mysore

 Rain Water Harvesting System

The team visited to the rain water harvesting is shown below

Department of EEE 24 ATME College of engineering, Mysore