A METHOD TO REDUCE SALINITY IN AN ESTUARIAL RESERVOIR

Abstract

Air bubbles have been used as a source of energy in a number of applications in the past years. Much of the work concerns the horizontal surface- currents generated by air-bubbles. The power of these currents has been used to reduce the height of sea waves and to prevent salt-intrusion in canals and rivers. The rates of air-supply are quite high. The present work concerns the use of bubble-energy at comparatively low rates, and aims at evolving a method of effectively using the energy of bubbles as they issue from nozzles, submerged in a fluid. The method consists of confining the bubbles within a limited volume of fluid, enclosed by two solid barriers* in the form of a tapering flame, the wider end of which is placed over the air supply line. The volume of fluid is caused to flow by momentum- transfer of the bubbles. In a two layer system of salt-water and fresh-water, the method enables the layer of salt-water to be gradually raised, through the flume to the surface, until no salt-water is left. By colouring the salt water, it is possible to detect the end-point, when the last trace of salt water is uplifted. As the power of the issuing bubbles is known, it is possible to find the total energy expenditure in raising the salt water. By applying the total energy concept, variations of total energy requirements and total losses are studied. Conditions for best operation, and characteristic performance curves are obtained from fundamental studies. It has been found that the flume behaves in a manner similar to a pump as well as similar to a mixer. The dual function appears suitable for dragging up saline water trapped in an estuarial reservoir, and for mixing it with the less dense fluid near the surface. Bubbling at low air-supply rates has also been applied to use the heat stored under ice cover to prevent ice-formation in lakes. This has been carried out by injecting air in the water without any other device (apart from the air-hose) and it has been stated that “considerable investigation is needed before this technique can be developed, so as to be the most efficient way of using the heat…….. to prevent ice formation”. *plastic sheets