Young Australian students have taken out high ranking places at the 2005 Intel International Science and Engineering Fair (Intel ISEF) in Phoenix Arizona.

Projects involving a navigational system for the blind, possible discovery of an ancient coastline on Mars and a lower-cost technology to analyse compounds used to protect against disease were the student projects that won top awards at ISEF.

Among the 1,447 students who competed in the 56th edition of the annual international event was 17-year-old Karabar Distance Education Centre student Andrew Stewart who earned third place in the Environmental Sciences category for his multitiered wetlands project: a technique for improving the efficiency of artificial wetlands.

Andrew's experiment was one of three entered from Australia and involved using a plant to remove excess nutrients from run-off water and thus reduce pollutants. Polluted waterways in Australia are a major local and international environmental issue-and Andrew investigated how a swamp plant, Carex appressa, absorbed nitrate and ammonium ions from water polluted by agricultural run-off. These ions promote rapid algal growth which can kill other aquatic life.

Andrew's plants soak up the ions quickly over five days but then slow their uptake. When more polluted water is added, the plants begin working again speedily for five days. Andrew is exploring whether a two-tiered artificial wetland filled with his plants is the way to remove most of the unwanted nutrients.

Also among the place-getters was 17-year-old David Llewellyn from Great Lakes College, NSW. David received fourth place for his experiment to assess the toxicity of introduced weeds on aquatic invertebrates.

Intel CEO Craig Barrett said Intel ISEF reflects what can happen when students are encouraged to pursue a passion and investigate the world around them. "It is truly inspiring to see what today's award winners have accomplished. I have faith that this new generation of young scientists and engineers will help cure diseases, protect the environment and develop breakthrough technologies that will one day change the world," Barrett said.

Other winners came across the world including Hungary Germany, Taiwan and Korea.