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Poly Vinyl Chloride Pipes in Rainwater Harvesting

 

Water which is essential for each human being needs to be utilized carefully. It has been estimated that in order to meet basic needs, individuals require 20 to 50 litres of safe water each day. Despite water's necessity to life, the reality is that billions of people worldwide are denied access to safe water. In 2002, the WHO estimated that 1.1 billion people (17% of the global population) lacked access to improved water sources, and 2.6 billion people (42% of the global population) lacked access to improved sanitation.(1) Half of the world's population will live with chronic water shortages by the year 2050 and 2.5 billion people have no access to basic sanitation (2)

Despite the fact that 75% of the Earth's surface is covered by water, only 2.5% of it is fresh water, of which three-quarters is locked up in glaciers and permanent snow cover. Only 0.3% of the water is surface water, found in rivers and lakes. The rest is buried deep in the ground. In many regions of the world, fresh water, both groundwater and surface water, is being used faster than it can be replaced. West Asia faces the greatest threat. Over 90% of the region's population is experiencing severe water stress.
Water stress is defined as areas where water consumption is more than 10% of renewable freshwater resources. Already about one-third of the world's population lives in countries suffering from moderate-to-high water stress, according to the Global Environment Outlook report.(3) Currently 800 million people are under a threshold of “water stress”. As rivers dry up, lakes shrink and groundwater reserves get depleted, that figure will rise to 3 billion in 2025, especially in parts of Asia and Africa . There is an urgent need to reduce waste and invest in infrastructure to harvest rainwater.(4)

 
 

Need for Water Harvesting in India
India has 18% of the world's population but only 4% of its fresh water and just over 2% of its land area. Many of the country's groundwater aquifers are already in critical condition. Available per capita water supply has declined since 1975 and water demand is set to exceed all usable sources of supply by 2050.(6) India's limited freshwater supplies are being steadily depleted through mismanagement and waste. Unless water resources are better conserved and used more efficiently, the IPCC has warned, the Ganges, Brahmaputra and Indus could be reduced to seasonal rivers by 2035.(7) Despite an estimated 2,464 cubic meters/person pa, many of its nearly 1 billion people suffer severe water shortages, in part as a result of uneven availability of water. Most rainfall comes during the monsoon season, from June to September, and levels of precipitation vary from 100 millimeters/ year in the western parts of Rajasthan to over 9,000 millimeters in the northeastern state of Meghalaya. Floods and droughts are both common throughout the country.(8)
In spite of higher average annual rainfall in India (1,170 mm, 46 inches) as compared to the global average (800 mm, 32 inches), India does not have sufficient water (9).

 
 

Water harvesting to recharge the groundwater enhances the availability of groundwater at specific place and time and assures a continuous and reliable access to groundwater
It reduces the rate of power consumption for pumping of groundwater. For every 1 m rise in water level, there is a saving of 0.4 KWH of electricity.
In saline or coastal areas, rainwater provides good quality water and when recharged to ground water, it reduces salinity and helps in maintaining balance between the fresh-saline water interface
In islands, due to limited extent of fresh water aquifers, rainwater harvesting is the most preferred source of water for domestic use.
In desert, where rainfall is low, RWH has been providing relief to people.
Rain is a primary source of water. The techniques of Rainwater Harvesting (RHW) are
1. Storage of rainwater for future use
2. Recharge to groundwater
The collection & storage of rainwater, prevention of losses through evaporation & seepage aimed at conservation and efficient utilization of limited water.

Types of Rainwater Harvesting
Catchment Areas
Rooftop catchments : In the most basic form of this technology, rainwater is collected in simple vessels at the edge of the roof. Variations on this basic approach include collection of rainwater in gutters which drain to the collection vessel through down-pipes constructed for this purpose, and/or the diversion of rainwater from the gutters to containers for settling particulates before being conveyed to the storage container for the domestic use. As the rooftop is the main catchment area, the amount and quality of rainwater collected depends on the area and type of roofing material

Land surface catchments : Rainwater harvesting using ground or land surface catchment areas is less complex way of collecting rainwater. It involves improving runoff capacity of the land surface through various techniques including collection of runoff with rain pipes and storage of collected water. Compared to rooftop catchment techniques, ground catchment techniques provide more opportunity for collecting water from a larger surface area.

Water Methods of Ground Recharge
 Storage Tanks
 Recharge Pits
 Trenches
 Abandoned Dug wells
 Abandoned Hand pumps
 Abandoned tube well
 Recharge wells
 Vertical Recharge shafts
 Shaft with recharge well
 Lateral trench with bore wells

How much water can be harvested ?
Water Harvesting potential        = Rainwater (mm)*Collection efficiency
Area of plot                              = 100 m2
Height of annual rainfall             = 0.6 m(600 mm or 24 inches)
Volume of rainfall over the plot = Area of plot *Height of rainfall
                                                = 100 m2 * 0.6 m
                                                = 60 m3 (60,000 litres)
Assuming that only 60 % of the total rainfall is effectively harvested,
Volume of water harvested     = 36,000 litres
An individual house of area of 300-500m2, the average cost will be Rs 20,000 – Rs 25,000 (11)
With one hectare of land, and 100 mm of rainfall, one can harvest 1 million litres of rainwater.(12)

Urban rainwater harvesting system
The components of a typical urban rainwater harvesting system are as follows:
Catchments: It is the surface that directly receives the rainfall and provides water to the system. It can be in the form of a terrace or a lawn or open ground. A roof made up of reinforced cement concrete (RCC), galvanized iron or corrugated sheets can also be used for rainwater harvesting.
Coarse mesh: It is present at the roof and it functions as a barrier to the passage of the debris.
Gutters: The channels around the edge of a sloping roof are called as gutters. The main functions of gutters are to collect and transport rainwater to the storage tank. Gutters can be in semi–circular or rectangular in shape. PVC is an ideal material. The size of the gutter should be according to flow during the highest intensity rain. It is advisable to make them 10 to 15 % oversize. It is important to support the gutters so as to prevent them from falling off due to water load.
Conduits: These are the pipelines or drains used to carry rainwater from the catchment area to the storage tanks. Polyvinyl chloride (PVC) is the common material used to prepare the conduits.
First flushing: A first flush device is a valve that ensures that runoff from the first spell of rain is flushed out and do not enter the system. The first spell of rain carries large amount of pollutants from the air and catchment area and hence first flushing is very essential.
Filter: The filter is used to remove suspended matter present in the rainwater. A filter unit is a chamber filled with filtering media such as fibre, coarse sand and gravel layers to remove debris and dirt from water before it enters the storage tank or recharges structure. Charcoal can be added for additional filtration. When rainwater is harvested in a large rooftop area, the filtering system consists of 3 concentric circular chambers in which the outer chamber is filled with sand, the middle one with coarse aggregate and inner most layer with pebbles.
Storage facility: The shape of these tanks can be cylindrical, rectangular or square. Commonly used material of construction includes plastic and polyethylene rotational moulded tanks is an ideal material. Depending upon the availability of space, these tanks could be constructed above ground, partly underground or fully underground.
Recharge structures:The ground aquifers may be recharged by the rainwater through suitable structures like dugwells, borewells, recharges trenches and recharge pits.

Conduits are pipelines or drains that carry rainwater from the Catchment or rooftop area to the harvesting system. Poly Vinyl Chloride is an ideal material.
Advantages of Poly Vinyl Chloride Pipes in Rainwater Harvesting
 Low cost
 Easy handling due to lightness
 Resistance to corrosion
 Non toxicity and inertness to chemicals
 Low thermal conductivity
 Resistance to abrasion
 Lower frictional losses
 Unaffected by termite, rodent, fungus and bacteria
 Ultraviolet stabilized, hence suitable for both indoor/outdoor applications
 Ease of installation, as all fittings made of PVC is available
 Ease of jointing by cementing, flanging

One of the high volume businesses is that of pipe business which includes PVC pipes for rainwater harvesting from diameter 50 mm diameter pipe upto 150 mm has helped entrepreneurs in achieving a higher net profitability. This net profitability is higher for large diameter pipes due to high volumes of business. This high volume business can be achieved by increasing the product mix with multifarious applications. These numerous applications which can be manufactured on a single machinery making the machinery versatile contributing to the growth of the plastic processing industry brings in higher net profitability for these entrepreneurs.
Distribution pattern, a very important element in the pipe business includes dealers in market where plastic products related to end use sector infrastructure exists. Well established with this distribution pattern, existing processors of plastic products related to infrastructure would find marketing of these products easier.. i.e. Existing processors of Polyethylene Rotational Moulded tanks, Poly vinyl Chloride pipes related to infrastructure business with their similar distribution network would find marketing of Poly Vinyl Chloride pipes for Rainwater harvesting easy.
Other factor contributing to the growth of this business is the growth in infrastructure business mainly the construction business.
Investment in Infrastructure Development in India
The Planning Commission has estimated that investment in infrastructure-defined to broadly to include road, rail, air and water transport, electric power, telecommunications, water supply and irrigation will need to be of the order of Rs 1450,000 crores or US$320 billion during Eleventh plan period. (13)

In India , construction is the second largest economic activity after agriculture

 
 

The investment in construction accounts for nearly 11% of India 's Gross Domestic Product (GDP) and nearly 50% of its Gross Fixed Capital Formation (GFCF) 65% of the total investment in infrastructure
The investment in this segment over the financial year 2005 to 2010 is estimated at US$124.65 billion (14)

(Total Housing units = 195 million)

 
 

(15, 16)
Initiatives by entrepreneurs with the Urban Development Departments, both for new as well old buildings in various states and mandation for Rainwater Harvesting in new as well as old buildings would help in storage of water for non potable purpose or recharge of groundwater. IS 13592 : 1992 amendment 4 of March 2006 has the foreward suitably modified to include rainwater harvesting

 


Contributed by Ms Poorvi C. Desai, Sr. Manager, Business Development-Polymers, Reliance Industries Limited
References
.(1) (Source: http://www.worldwatercouncil.org/fileadmin/wwc/Library/Right To Water_Final Text_Cover.pdf)
(2) (Source : The Environmental Benchmarker & Strategist)
.(3) (http://news.nationalgeographic.com/news/2003/06/0605_030605_watercrisis.html)
(4) (Source : http://www.un.org/works/Lesson_Plans/Water/Lesson_Plan_on_Water.doc )
(5) (Source:http://www.ci.austin.tx.us/watercon/rainwatersites.htm)
(6) (http://www.nextbillion.net/newsroom/2007/12/07/opinion-is-demographic-growth-good-for-india)
.(7) (http://209.85.175.104/search?q=cache:be3vg0sRtIMJ:www.businessworld.in/index2.php%Foption%3Dcom_content%26)
(8) (Source : http://www.care4nature.org/ecoinfo/indiamatters/archivewater2.htm)
(9) (Source: http://www.sulekha.com/expressions/articledesc.asp?cid=235222
(10) (Source : Serah Marie-Helen 2000, Water-Unreliable supply in Delhi , Manohar Publishers & Distributors, Centre for Civil Society)
(11) (Source : Centre for Civil Society)
.(12) (Source : http://www.siwi.org/press/presrel_05_SWP_Winner_Eng.htm)
(13, 14) (Source : Crisinfac)
(15, 16) (Source : http://209.85.175.104/search?q=cache:ujBEjp9Nd0YJ:tejas.serc.iisc.ernet.in/curr

 
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