Here’s something interesting (from AOL news):

(Sept. 13) – The beautiful trail in the sky looked like a mysterious celestial event. In reality, it was urine.
Some skygazers were treated to the unexpected view of a bright sparkling glow Wednesday night, created when astronauts aboard the space shuttle Discovery dumped the waste out into space.
The water dump was a scheduled task for STS-128 pilot Kevin Ford, who poured out urine and waste water stored aboard the shuttle in preparation for a landing attempt Thursday. Weather thwarted that try, but astronauts found sunny skies in California on Friday and descended at Edwards Air Force Base to end a demanding two-week mission to the International Space Station.
The light show Wednesday was aided by an unusually large amount of water being dumped all at once – about 150 pounds (68 kg), said NASA spokeswoman Kylie Clem. Discovery had just undocked from the International Space Station the day before, and had not been able to unload waste water during the 10-day visit.
“It would have been a large quantity because we don’t do water dumps while docked to the station now,” Clem told in an e-mail. “That is a fairly new restriction over the last couple of flights in order to prevent potential contamination of the Kibo module.”
The Kibo module is a new Japanese-built research lab on the space station that includes an external platform to expose science experiments to the space environment. Water dumps from a docked shuttle could potentially pollute the experiments.
In general, though, spotting space water dumps from Earth is common, Clem said.