Critical flux and rejection behaviour of non-circular-channelled membranes: Influence of some operating conditions

The use of non-circular-channelled membranes and their performance in microfiltration as a pretreatment for desalination for wastewater reuse has been investigated. The membrane performance is appraised with reference to (i) fouling propensity, i.e. critical flux and (ii) removal of organics in terms of solid retention efficiency. Critical flux determinations were carried out, employing the step by step technique, under various operating conditions (Reynolds number, pore sizes and pH). The effluent from a synthetic activated sludge production process was used. Increasing the pore size appears to increase the critical flux as does increased pH. It is shown that the non-circular geometry gives rise to a very high critical flux under turbulent flow conditions whilst the opposite effect is observed under laminar flow conditions. Solid retention efficiencies of up to 92% are achieved which decrease with increment in pore size. It seems that a larger pore size allows the transmission of smaller particles accounting for the lower rejection seen. All observations are explained in terms of the hydrodynamics and particle interactions involved within the membrane filtration system.