As(V) removal from drinking water by coagulation and filtration through immersed membrane

In this work we investigated As(V) removal by coagulation with FeCl3 as coagulant combined with microfiltration through immersed membrane. The adsorption capacity of the coagulant was determined and the continuous removal of arsenic was performed with special emphasis on the membrane fouling rate. During a continuous experiment in a reactor with an immersed membrane, tap water was spiked with 100 μg/L of As(V) and treated with 5.16 mg Fe(III)/L. During the experiment, the concentration of As(V) in treated water was always under 10 μg/L. The configuration of the membrane allowed the maintaining of a high permeate flow rate at 60 L/m2 h. Membrane fouling was mostly caused by the precipitation of scale on the membrane surface and into the membrane pores which contributed 50% to the total resistance while the cake resistance contribution to total resistance was low and reached 15% at the end of the experiment when suspended matter in the reactor reached 8.85 g/L. The initial permeability of the membrane could be restored by chemical cleaning with oxalic acid. The investigated process showed good efficiency and stability in removing As(V) from drinking water.

► As (V) adsorption on to Fe (OH)3 during coagulation
► Separation of coagulant suspension by immersed membrane
► High permeate flux achieved and low membrane fouling observed during experiment
► Possible implementation in existing arsenic removal process