Optimization of backwashing in pressurized sand filters: interaction between rate and duration using response surface modeling

Pressurized sand filters are widely used in solid–liquid separation processes, where maintaining filtration performance requires periodic backwashing to restore bed permeability and remove accumulated contaminants. The efficiency of this procedure depends on applying a backwashing rate high enough to promote particle detachment and transport without inducing loss of filter media. However, operational parameters are commonly defined empirically, despite their strong influence on cleaning performance and water consumption. This study investigated the interaction between backwashing rate and duration using a Central Composite Rotational Design to identify operating conditions that maximize contaminant removal while minimizing the volume of water discharged. Backwashing efficiency was quantified based on the residual total suspended solids retained in the filter bed after each experiment. Response surface modeling indicated that high backwashing rates (∼77.6 m 3 m −2 h −1 ) enable removal efficiencies above 90%, while experimental validation demonstrated that short durations (1 min) can achieve comparable performance to longer cycles. These results show that effective backwashing can be achieved within the first minute of operation when adequate hydraulic conditions are established. This strategy allows substantial reductions in water consumption (up to ∼70–80%) without compromising cleaning efficiency. • Backwashing rate is the dominant factor controlling cleaning efficiency. • High rates combined with short durations achieve >90% contaminant removal. • Short-duration backwashing reduces water consumption by up to ∼70–80%.