WWT	WATER & WASTEWATER TECHNOLOGIES (WWT) INSTITUTE FOR ADVANCED STUDIES

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Water has been described in the Holy Quran at 63 places, reinforcing its pre-eminent position in human life.

 

Water appears to be the simplest of all compounds, but it is extremely complex in its structure and properties. Not many of us will know that water in its purest form is more corrosive than the strongest of acids. It is common knowledge among the scientists that no single model is able to explain all of its properties.

 

Water is the pre-eminent vector of life and human activity. Water constitutes 60-70% of the weight of animals and 80% of that of other living mechanisms. It will be of interest to you, to know some of the significant features of this invaluable resource on our planet, Earth. There is a
so-called hydrological cycle, in which water undergoes various phases. Total water on earth is estimated at 1,370 million km3, however fresh water is of the order of 0.5 to 1.0 million km3 only. The atmosphere contains about 50,000 km3 of water. The rate of evaporation is about 500,000 km3/year. Precipitation on the continents is around 120,000 km3/year. Nature processes only a very, very small part of all the water in the world for use in the ecosystems and for municipal, industrial, and agricultural purposes. Only 0.3% of the fresh water supply is accessible for human consumption.

 

Water by design is perfect. Water is satisfying and cleansing, but unfortunately, it is not always pure. Water is no longer considered to be an infinitely renewable resource that we once thought it was.

 

The annual fresh water demand of the world was projected to increase from 4,130 km3 in 1990 to 5,190 km3 in 2000, implying a sharp decline in the per capita availability of water in large parts of the world. Regional disparity of water supply and the explosive growth of megacities intensified the demand for large scale transfer of fresh water. Between the year 1950 and 1990 the number of cities with a population of over a million increased from 78 to 290. According to a UN report the scarcity of water may prove to be the most important obstacle to sustainable development, and even survival, over large parts of the world.

 

In the context of the industrial activities of the modern world, it would be necessary to keep in view that overall one ton of industrial products would represent an average use of 200 tons of water (44,000 gallons). The production of a ton of steel requires 33,000 gallons of water, a ton of petrol in a refinery from crude oil needs 16,500 gallons of water, and a ton of artificial fibre from a chemical needs about 165,000 gallons of water. These facts imply some very important economic fundamentals, which have been too long ignored. The first is that industrial expansion or development is impossible without water in large quantities. The second is that unless water can be obtained at a lower cost per unit than all the other materials involved in an industrial product, industrial production will be expensive and impractical. In early ‘90s there were reports by the Industrial Estates Associations that water shortage affected production in most industries, reducing their production capacity to one third.

 

Realizing this grave situation, a United Nations Water Conference was convened in 1977. The International Drinking Water Supply and Sanitation Decade was launched in 1980 with a realization of the need to provide about 2 billion people with safe drinking water and adequate sanitation by 1990. Shortage of finance and skilled staff hampered the achievement of this goal and the theme was extended beyond the 90’s. An international body by the name of World Water Council was created in 1996 to promote global awareness and advocate sound policies. Fresh water, a potential source of conflict in every region was high on the agenda of environmental ministries from around the world at a meeting in early 1998 held under UNEP.

 

Technically and economically, it is now feasible to generate large volumes of water of acceptable purity through the desalination of seawater, brackish water, and water reuse. It is an established fact that the desalination technology has come of age. By December 1997, the IDA World Wide Desalting Plants Inventory Report No. 15 shows that 12,451 units with a total capacity of 5 billion gpd had been installed or contracted. About 59% of this capacity was of seawater plants alone. Desalination is now economically used in 120 countries around the world.

 

Desalination was usually thought to be a process of water supply appropriate only for arid and rich countries, typically in the Middle East. It is true that most of the very large desalination plants are located in the Arabian peninsular; There are, however, a surprising number of plants around the world, some in places that were not supposed to be good candidates for this rather expensive source of water.

 

The Middle East id the biggest user of desalination technology with a production capacity of 2.64 billion bgd that is about 53% of the world total. The largest Reverse Osmosis plant is operating at Yanbu, Saudi Arabia with a capacity of 33 mgd, which uses the Toyobo Cellulose Hollow Fibre technology. The biggest thermal desalination unit is located at Tawilah, UAE, with a production capacity of 117 mgd. The Middle Eastern Countries cannot live without desalination any more and the share of Desalination in these countries for potable water supplies is 65 to 85 percent.

 

The commercially viable desalination processes in use worldwide today can be categorized into two major types: (a) Thermal Processes and (b) Membrane Separation processes. There are again three sub-categories under (a) viz. (i) Multi Effect Desalination (MED), Multi Stage Flash Distillation (MSF) and Mechanical Vapour Compression (MVC). There also three sub-categorize under (b) viz. (i) Brackish Water Reverse Osmosis (BWRO), Electrodialysis Reversal (EDR) and Seawater Reverse Osmosis (SWRO). It is important to understand that the overall design of desalination plants is site specific and the plants are not available as ex-shelf items.  

 

 

The coastal region of Sindh and Balochistan is full of promise for introducing desalination technology. There was a time when water for settlements on the coast used to be transported in launches plying from Karachi. One of the serious inhibiting factors in developing economic activities in the coastal region has been lack of fresh water. The desalination systems, both thermal and reverse osmosis, lend themselves eminently to the use of renewable sources of energy. There is plenty of sun available. Mature technology for conversion of solar energy to electrical power via photovoltaic systems is also available. The RO Desalination plants could be installed at point of use could be installed in the shortest possible time. Thermal desalination units based on the latest Evacuated Tube and Heat Pipe Collector technology could also be installed at places where reasonable maintenance facilities are available. Efforts for poverty alleviation can become more meaningful, if dependable systems for at least drinking water for the people are provided at subsidized rates.