A new approach to backwash initiation in membrane systems

Fouling is a common but serious problem encountered during membrane filtration. It leads to permeability decline, higher energy demands for maintaining a constant permeate flux and eventually requires the membrane separation process to be completely stopped for physical or chemical cleaning of the membrane filtration system. Previous studies associated with membrane cleaning involving complex models, statistically designed experiments and trial and error have shown promising results in terms of reducing membrane fouling. However, the success attributed to these approaches relies on steady operating parameters, like foulant concentration and permeate flux. Unfortunately, in most full scale applications, these conditions are not fulfilled, resulting in non-optimal results in terms of membrane fouling. This study involved a detailed investigation into membrane fouling, permeate flux recovery and control techniques to develop a new control system able to optimise the backwash, which is considered as the most efficient technique for fouling minimisation, especially when using hollow fibre membranes. This new control system was validated by a series of experiments resulting in the reduction of up to 40% in the backwashing water required. The system was also able to automatically optimise backwash initiations at variable permeate flux and variable concentrations of organic matter in the wastewater.