The typical sediment load above treeline in the High Sierra (including Mt Whitney) is decomposed granite (sand) with a small amount of fine material (silt) and very little organic material. The sand sinks to the bottom, but the fines might be in suspension and hard to see. Organic matter can be invisible, but there is very little organic matter above treeline. The water is mostly clear above treeline and you're only on Whitney for 1-3 days. However, with 17,000 people on the Whitney trail every year, I recommend some type of insurance against water contamination in this area. Filtering seems like a heavy option. Consider Aquamira drops, a UV penlight, tablets, or other lightweight methods instead of filtering.
I really like the Aquamira drops. Mix the two parts and then go get your source water. By the time you fill up your container, the 5-minute premix is done. Then there is a 20-minute delay before you can drink, but the taste is clean, its very convenient, and lightweight. I usually go with about 1/2 the recommended concentration unless the water is sketchy.
I can share a few lessons I've learned the hard way over the years using a variety of filters. This is mostly applicable to popular camp locations at lower elevations below treeline where some slow creeks (and many lakes) might have organic matter (mush) at the bottom and/or a higher concentration of fine material (silts). This stuff will clog your filter quickly if you aren't careful with the location of the intake in the source water. This may require you to be hunched over in a pretzel position with a third hand to hold onto the clean water container. Prefiltering is usually a very good idea in this situation. Use the prefilter that comes with your filter, or any decent prefilter that connects to your intake hose. Bring a spare prefilter especially for a long trip or big group. Coffee filters with a rubber band or twist tie to seal around a prefilter will help extend the life of the prefilter, but will increase pumping resistance and its another hassle to deal with, but it seems to work and its lightweight.
You can do as REI recommended and pour the untreated water through a bandana or other cloth before filtering (coffee filters are too slow for drip filtering). This technique allows you to sit down on a rock or log while pumping. You should still use a prefilter and perhaps a coffee filter depending on the fine sediment load. This approach requires an additional container you are trying to avoid, but your cookware might work for small batches. Platypus makes a large bag container with a ziplock open top which can be useful and not too heavy. This approach is surely overkill above treeline especially when dealing with snowmelt as the nearby source.
