Removal of phosphates from water by a hybrid flotation–membrane filtration cell

A new hybrid process for treating wastewater, combining membrane microfiltration and flotation, was investigated. The hybrid process combines the advantages of both membrane separation and flotation: the flotation cell removed a large proportion of suspended solid particles while the membrane module produced a clean water permeate effluent. The hybrid process was investigated using an aqueous suspension of iron colloidal particles produced in situ. Process parameters investigated were: effect of gas flow rate, which was necessary for the flotation process, and the frequency and length of backflushing, required in order to reduce the fouling of membranes and to extend their useful working time. The results indicated that the increase of airflow rate positively affected the hybrid cell performance, up to a critical value. Backflushing, on the other hand, resulted in an improvement of the hybrid cell performance.