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New products from Indian laboratories -- Cost-effective water purifier

Somasekhar Mulugu

THE National Chemical Laboratory (NCL), Pune, has developed a water purifier that can exclude viruses and bacteria, operating at a minimum tap pressure of 90.4 bars. The cost-effective, manually-operated purifier is targeted for application in the rural areas.

The purification is done by a membrane fabricated and patented by NCL scientists. The pores of the ultrapurification membrane are small (less than the dimensions of a virus) and adequate to remove worms, spores and viruses.

The membrane is cost-effective and has an average life of three-four years. The cost of the water treated using the membrane works out to around 83 paise per litre, as per the economics worked out by the Laboratory.

Membrane technology is commonly used to treat water, including waste water, on a commercial scale. Ultrapurification systems are, however, considered ideal for domestic use, individual homes and buildings. Such application is widespread in Japan and othe r advanced nations.

France, which uses highly-developed water technologies, has made considerable progress in using ultrapurification technology for municipal drinking water supplies. It has also proved the method on a pilot scale at several locations.

To achieve good results in the use of ultrapurification technology, the membrane used for waste water treatment should be highly permeable, low-fouling and able to reject undesirable species. Ideally, the membrane should eject both bacteria and viruses, which cause health problems.

Typical water-borne bacterial diseases include dysentery, typhoid, tuberculosis, cholera; and viral infections include polio, hepatitis and encephalitis. In developing countries such as India, water-borne diseases are the primary cause for the large numb er of deaths; the supply of safe, potable water has been recognised and advocated as the best way of eliminating this problem.

According to Dr. B.D. Kulkarni, the NCL scientists designed a self-cleansing purifier based on mechanical power instead of electrical power so that it can be easily utilised in the rural areas. The mechanically-operated pump circulates water from a groun d level tank to the membrane module at a given pressure, which is adjusted with the help of a valve. The feed water is passed in a tangential direction to the membrane so that any large molecule or particles are pushed ahead and do not block the pores of the membrane. The system is thus self-cleansing. The filtered water is collected in a vessel and the balance returned to the tank or used for non-drinking purposes.

The NCL has tested the membrane modules with the established E coli broth test for bacteria and such small molecules as albumin and casein. The membrane efficiency can be affected if the water quality is poor, or if a leak develops, but it can be rectifi ed.

Warheads for

Indian missiles

In modern warfare a country's firepower is measured by its ability to cripple critical civil and defence installations of the enemy. Airports, supply depots, fuel points and armament centres are the key targets.

Missiles with long reach, lethal payload and accurate strike ability play a vital role in determining the result of most battles. The Gulf War of the early 1990s and the US bombing of Yugoslavia in 1998 are apt examples of the effective use of missile sy stems with high accuracy and precision.

Indian Defence scientists have successfully developed a range of missiles _ Agni, Prithvi, Akash, Trishul and Nag _ under the Integrated Guided Missile Development Programme (IGMDP), launched in 1982.

Of these, the Prithvi _ both in its Army and Air Force versions _ has been introduced into the country's Defence services after extensive trials. Bharat Dynamics Limited (BDL), Hyderabad, manufactures and supplies the missiles to the armed forces.

The scientists of the Defence Research and Development Organisation (DRDO) have also fabricated four different warheads that would be utilised as per the target to be bombed. The enemy points range from soft targets _ like soldiers in the open _ to more difficult ones, such as airport runway, industrial complexes, food and ammunition supply depots, and control rooms.

In designing the warheads, the DRDO scientists had to develop new technologies and complex mathematical models. For this, the scientists fabricated software that not only aided in design but also in the prediction and performance of warheads under variou s combat conditions.

The software package and computer aided design (DAD) tools have led to the optimal design of various sub-systems of the warheads. For example the antitank-cum-anti-personnel bomblet developed for the Prithvi missile, has been made universal in design for a range of products, including cargo shells, bombs and rocket systems.

The warhead systems designed and developed will enable the armed forces to use a fully indigenous strategic weapon system. This capability is crucial, especially when agreements on the non-use of nuclear weapons become the norm globally. Conventional arm aments with enhanced range, precision and destructive power will play a major role in deciding the future of warfare.

The four different warheads developed by the Defence scientists include a pre-fragmented warhead for neutralising soft targets; the submunition type, which incorporates the Dual-Purpose Improved Conventional Bomblet is effective against personnel up to a distance of 10 metres around the point of burst, while the submunition incendiary warhead is effective against inflammable targets. The runway denial penetrating submunition warhead is designed to neutralise targets such as runways and industrial comple xes.