Concentration of urine in a pool

During the 2012 Summer Olympics in London, US swimmer Michael Phelps admitted to peeing in the pool during training sessions. Does it matter? Have your students calculate the concentration of urea based on the information below.

“Peeing in a swimming pool, even if all swimmers do it simultaneously, has very little impact on the composition of the pool water itself. An Olympic-size pool contains over 2 million litres of water and a single urination is somewhere in the region of 0.2 litres.” Don’t forget the approximate concentration of urea in urine is 9.3 g/L.

(Answer 9.3 x 10-7 g/L or 9.3 x 10-4 ppm)