Recently I have compared the results of WEOC studies with and without filtering (Gleyic Albeluvisols) and they are almost the same. Is it possible to avoid filtering procedures?
You need to define which aspects of WEOC were being analyzed in those studies that were compared so we can fully answer this question: concentration, composition, size distribution, etc?
Filtration provides a means of standardization. If you do not wish to filter, you should probably centrifuge the samples and pour off the supernatant to reduce the microbial cell count, especially if you plan on storing those samples for any length of time (even at 4 C).