Clorax and water. Mix half and half, spray on and leave until the mildew is gone and rinse off.
yup that works......just wet surrounding grass & plants first....then rinse again
a pressure washer alone should remove it
I agree with HandyANDY so If you don't have a pressure washer then I would suggest renting one. It will do the job without worrying about killing plants/grass.
Good old elbow grease. Mixture of some bleach and water good stiff brush on a pole and have at it. Once done, rinse with a good strong stream of water from the house. use lots of water to prevent the bleach from harming any plants or grass along the sides of the walk.
Muratic acid. Buy it at the hardware store- follow the directions on the bottle.