Joshua Zhou, of Chapel Hill, was one of 20 Best of Category winners, earning $5,000 Friday at the Intel International Science and Engineering Fair.

In the Earth and Environment Sciences category, Zhou created a means to use industrial waste products combined with energy from light to degrade and remove pollutants from water, making it safer for aquatic life and human consumption.

The top prize of $75,000 went to a Canadian teen for his system to improve air quality in airplane cabins.

Zhou was one of 1,700 finalists who competed in Pittsburgh in the world’s largest high school science research competition.