When the solid particles in a suspension are large and uniform in size, the pores within the filter cake remain relatively unobstructed, allowing the filtrate to pass through the cake layer at a high velocity. The use of flocculants to aggregate fine particles into larger clumps helps to enhance the filtration rate.
For suspensions containing solid particles that settle rapidly, it is advantageous to employ filtration equipment that feeds the suspension from above the filtration medium; this aligns the direction of filtration with the direction of gravity, allowing coarser particles to settle first and thereby minimizing clogging of both the filtration medium and the filter cake. For suspensions that are difficult to filter-such as colloidal systems-incorporating coarser solid particles (e.g., diatomaceous earth or expanded perlite) can render the filter cake more porous. Furthermore, when the filtrate exhibits high viscosity, heating the suspension can effectively reduce its viscosity. All of these measures serve to accelerate the filtration process.