A. Adin

Coupling flocculation with micro-ultrafiltration for waste water treatment and reuse

Secondary treated wastewater contains residual organics (non biodegradable and metabolites), colloids and suspended solids. Microfiltration or ultrafiltration is adequate for producing disinfected clear water suited for different kinds of applications. This may also be considered as a pre-treatment before reverse osmosis with the aim of extending the field of the produced water. However fouling of microfiltration or ultrafiltration membranes is the main limitation. Flocculation by its ability to remove organicolloids which play an important role in fouling phenomena might make the process more feasible. This study has been focused on the influence of flocculation on decreasing fouling of ultrafilration and microfiltration membranes. In a first step the optimal conditions of flocculation were determined. Two ranges of flocculant doses and pH correspond to high efficiency removal of suspended solids and organics (Total Organic Carbon). In a second setp the coupling with microfiltration (0.2 μm) or ultrafiltration (50 kDa) has been studied. The efficiency of the whole process is mainly dependent on the flocculant doses. Ultrafiltration is more suited than microfiltration due to higher efficiency. Flocculation allows quasi steady state operation of ultrafiltration at quite a high value of the filtrate flux. The critical flux corresponding to long term stable operation is dependent on the flocculent doses. The optimum values of the optimum doses previously determined correspond to a technicoeconomical optimum of the coupled process. These results obtained on a lab scale are presently being checked on a pilot scale.