Not necessarily "filtration" but rather "treatment". There are a number of various chemical treatments that can be used. For clear water I use MSR water treatme

Not necessarily "filtration" but rather "treatment". There are a number of various chemical treatments that can be used. For clear water I use MSR water treatment tablets (chlorine dioxide?), for seriously muddy and dirty water I rely on my partner's filter. We walked over 500 miles of desert in Utah and Arizona, the water tends to be very hard to come by and what's available is often contaminated by cattle, etc. Water treatment is a must.