Decks, Patios, Porches and Docks - Pressure washing deck

Hello, I'll first state that I'm completely new to home repair so bear with me :). I recently purchased my first town home and am in the process of fixing it up and repairing it. The house itself is only about 6 years old but the previous owners didn't maintain it at all. Currently I'm working on the deck. The deck is a 2 story deck that doesn't look like it has ever been sealed or stained in the past. It is very green which I'm guessing is mildew and black in a few places.

Yesterday, I purchased a Husky 1600PSI 2.4GPM pressure washer from home depot and some ZEP concentrate deck washing solution. I mixed the right amount of water and concentrate in and began pressure washing. The washer took off a tremendous amount of mildew and even much of the blackness but there is still some on certain boards. I believe I was washing it pretty hard and maintained good strokes but after a certain point it just wasn't coming off.

Is there anything I can do to remove the green from the board? I really don't want to stain and seal the deck until i'm confident I got everything.

-Shaun

I normally use a bleach/water solution and get good results. I'll mix 40-50% bleach with water and spray it on with a pump up garden sprayer, let it set and then rinse with the PWer. I'll retreat stubborn areas, sometimes scrubbing with an old broom will help.