Understanding the role of operating condition on fouling development in membrane distillation (MD) is critical
for the further optimization of MD technology. In this study, organic fouling development in MD was investigated
varying the feed inlet temperature from 35 to 65 ◦C and the cross-flow velocity from 0.21 to 0.42 m/s. The
fouling layer thickness was estimated at the end of each experiment non-invasively with optical coherence to-
mography. The set of experiments was mined to model the initial flux decline, the near-stable flux, and the final
foulant thickness responses by central composite design, a useful response surface methodology (RSM) tool. The
results indicated a linear increment of the fouling thickness by increasing the feed inlet temperatures. Overall,
the feed inlet temperature governed both the initial flux decline and the fouling deposition. The benefits in water
productivity obtained by increasing the feed temperature were always offset by higher fouling deposition. Higher
cross-flow velocities showed a positive effect on the initial flux, which however translated in larger values of the
initial flux decline rate. On the other hand, the higher shear stress contributed to a decrease of the final steady-
state fouling layer thickness. The proposed approach was proven to be a valuable tool to assess the role of the
operating conditions on fouling and process performance in MD.
