Mysuru: Water scarcity has become one of the greatest concerns that has been on the minds of humans. But the girls from St. Rosello’s Central School, Mysuru, feel that the public are aware about water scarcity but yet have not adopted conservation practices and still continue to misuse this vital naturally available resource. The girls have designed a model titled ‘Sewage Water Treatment’ where the impure water is recycled and reused.  Shivapriya, M.U. Krupa and G. Likitha of Rosello’s School with their demonstration of sewage water treatment, explain how it can be used for irrigation and domestic purposes. The treatment involves a physical, chemical and a biological process. The contaminated water or sewage is screened where large objects are removed. Then the water is given a primary and secondary treatment before being sent into the settlement tank. The primary treatment — organic solid waste is removed in circular tanks, where heavy solids settle to the bottom and oil and grease float to the surface. Micro-organisms and the secondary treatment removes dissolved and suspended biological matter. Then the water flows into the settlement tank which has a soil bed and the water can be used for irrigation and washing purposes. Shivapriya said, “This water is not safe for drinking or cooking, but it can be used for other household purposes; we need to save water as much as possible and this water treatment and putting it back to use will definitely make a change towards the sustainable development of the earth.”