Are the non-reservable campground spots usually full in August?

People don't report that info here, but I think if you aren't particular, campsites are available if you arrive early in the day, especially days besides Friday or Saturday.

There are ample walk-in campsites, new ones added in 2012:
See this thread for a map

I probably should have asked... are the sunsets/sunrises from the Mt Whitney summit great?

I think they're worth the extra effort. Where else will you experience sunrise or sunset from a mountain peak. Yes, the crest at Trail Crest, or from any of the Windows along the crest are good places to see it, too. But other than the summit, the other places don't have convenient sleeping spots.


What kind of treatment do you recommend for lake water? I'll take what I think I'll need for the whole trip up and down, but just in case I can take some treatment tablets/filters.

Carrying all you need for a day hike is a recipe for failure. You probably need at least 6 liters, maybe more. Old regulars don't even treat the water -- I dip and drink from every stream, and just walk to the inlet stream at Trail Camp rather than use the little pond. If you would rather filter or treat, then do that. But DON'T try to carry all you need. (By the way, you need at least 3 liters from the last water, pond at Trail Camp, or until it dries up, the trickle at switchback 22 above Trail Camp.)