By Guest Author Rohit P. Singh
Water, the fundamental necessity of every extant species on earth, is becoming a source of danger in many parts of the world today. According to a survey by the World Health Organisation (WHO), unsafe drinking water kills more than 1.5 million children per year. More than 1.1 billion people today lack access to clean water, and 2.6 billion people lack access to basic sanitation. As we know that only 1% of water on earth is drinkable, as 97% is saline and 2% is in the form of glaciers, a global population of over 6 billion people that is increasing at a rate of around 80 million people per year can only be supplied with clean water if we find a sustainable method to convert saline water into clean water.
Desalination, which is the conversion of seawater containing salts and minerals to potable water through various physical and chemical methods, has emerged as a potential solution to India’s and the world’s looming water crisis. India has taken steps towards commissioning desalination plants to meet the needs of people with no access to safe water. The most important issue is the cost-effectiveness of the methodology and the type of energy used for desalination. India has recently built desalination plants that use nuclear and even solar power apart from the conventional fuels. Many factors enter into the capital and operating costs for desalination: capacity and type of plants; plant locations; feed water quality; labor, energy and financing costs; ease of concentrate disposal, the level of instrumentation and automation; and plant reliability. However, as a guideline, the production cost of a brackish water desalination plant is rupees (Rs.) 10 to 15 per cubed meter of water. The production costs for a seawater desalination plant vary between Rs. 40 and 50 per cubed meter, whereas the production costs of desalted water from effluent vary from Rs. 15 to 50 per cubed meter.
As one example of a plant, the recently installed Kudankulam Nuclear Power Project (KKNPP) in the Tirunelveli district in Tamil Nadu in South India has tremendous capacity: it produces desalinated water at a rate of 300,000 liters per hour. Taking seawater from the Gulf of Mannar, the plant uses a mechanical vapor compression technology and has two 1,000-MWe Russian reactors. It is expected to start working by the end of this year and has been erected on a turnkey basis by Tata Projects in conjunction with IDE Technologies Limited, Israel. A solar-powered desalination plant produced by The Energy and Resources Institute (TERI) has the capacity to produce 100 liters of clean water per day. Although the process of desalinating saline water – evaporating water, condensing and collecting the pure water vapor – remains the same, what makes all the difference is the TERI plant’s no-fuss, closed-loop design and the total absence of conventional fuels, making it sustainable, affordable, and eco-friendly.
Thus, if India’s 7,000-kilometer coastline is put to use by the government as well as the private sector, we may see the beginning of an end to the country’s water concerns. Apart from solving the water crisis, desalination technology could also prove to be a blessing in disguise in solving water conflicts with neighboring countries such as Pakistan and Bangladesh. As MNCs such as General Electric and Aquatech are building huge plants in the western state of Gujarat, a solution to the longstanding conflict with Pakistan over the 1960 Indus Water Treaty can be devised, by providing clean water to both Gujarat and Pakistan.
The project commissioned to Aquatech is India’s first ultra mega power project (UMPP) and is located at Mundra in coastal Gujarat. The 4,000-megawatt coal-fired plant is owned by Coastal Gujarat Power Ltd. (CGPL), a Tata Power group company. The project aims to produce 12 million liters per day of treated water by November 2009 and will be India’s first private sector power project using supercritical boiler technology.
However, desalination is best-suited and most cost-effective for regions that close oceans. Supplying desalinated water to a place such as Delhi, which is far from the sea, will be expensive. Therefore, we also need to look into other potentially effective solutions such as rain water harvesting. Not long ago, most the cities were self-sufficient in meeting their water needs from the extensive urban water bodies that supplied water to citizens. But today, it seems as though these bodies have disappeared and groundwater is being extensively extracted by both the government and the private sector. So now, what we need to do is not dam a river and block its flow, or boost water out of the ground and suck the earth dry, or build canals and lay kilometers of pipes, but merely harvest rainwater.
As India receives only about 100 hours of rain a year, these 100 hours must be used efficiently to catch and store water for the remaining 8,660 hours. In areas where there is inadequate groundwater supply or surface resources are either lacking or insufficient, rainwater harvesting offers an ideal solution. Recharging water into the aquifers also helps improve the quality of existing groundwater.
A typical rain water harvesting system for a roof top consists of catchments (which directly receive the rainfall and provide water to the system); coarse (at the roof to prevent the passage of debris); gutters (channels all around the edge of a sloping roof to collect and transport rainwater to the storage tank), conduits (pipelines or drains that carry rainwater from the catchment or rooftop area to the harvesting system); first-flushing (a valve that ensures that runoff from the first spell of rain is flushed out and does not enter the system); filters (used to remove suspended pollutants from rainwater collected over roofs); storage tanks and recharge structures. These components handle the complete process of transporting, filtering and storing water in a rainwater harvesting system.
Rainwater harvesting is currently practiced on a large scale in cities such as Chennai, Bangalore and Delhi, and has been made a part of the state policy. Rainwater can be harvested for storing it for ready use in containers, and groundwater recharging for withdrawal later. It can be done on surfaces such as rooftops, paved and unpaved areas, water bodies and storm-water drains. In Ahmadabad, rainwater is even collected in tanks at places such as temples, hotels and residential buildings. Bangalore is set to adopt rainwater harvesting in all buildings, including residential ones, built on existing sites equal to or greater than 60×40 feet and new, planned sites equal to or greater than 30×40 feet, if the Legislative Council approves a bill to do so.