“…There have been some theoretical developments that account for the accumulation of particles in UBE models (e.g., Mackie et al, 1987;Choo and Tien, 1995;Putnam and Burns, 1997), and other simplified models that relate particle accumulation to changes in pore transmissivity (e.g., Hunt et al, 1993;Boller and Kavanaugh, 1995;Stephan and Chase, 2000). However, in general it is difficult to represent processes of particle mounding using trajectory analyses and hence, these types of analyses are best suited to modeling the efficiency of clean filter beds.…”