Removal of Nitrate from Water Using TiO2/ PVDF Membrane Photobioreactor

Removing low-concentration nitrate from water is desirable because it may cause eutrophication when discharged, but it is challenging using current technologies. Membrane photobioreactor (MPBR) technology (which is the combination of membrane and microalgae cultivation) emerges as a suitable option to efficiently reduce the nutrient load from wastewater. This study developed a high-efficiency microalgal-bacterial Membrane PhotoBioReactor (MPBR) to biologically remove nitrate from water. In order to obtain low-fouling membranes, TiO2 nanoparticles were entrapped in PVDF membranes prepared by the phase inversion method. Successful fabrication of composite membranes (PVDF/TNT) was confirmed by using XRD, FTIR, DSC, TGA, SEM, and AFM. Membrane properties were studied using contact angle, tensile strength, pure water flux, Bovine Serum Albumin (BSA) rejection, antifouling properties, and porosity. Compared with the pristine PVDF films, the hydrophilicity, permeability, and antifouling performance of the proposed membrane were improved. A laboratory-scale MBR equipped with a synthesized membrane was used to evaluate the performance of mixotrophic denitrification under different Carbon Nitrogen (C/N) ratios, Hydraulic Retention Times (HRT), Nitrate loading, and Influent alkalinity. Methanol was supplied as a carbon source. Almost complete denitrification was achieved when the bioreactor was fed with 75 mg/L NO3−–N, 150 mg/L methanol at 4 h HRT without external alkalinity supplementation. The results as a whole indicated that the MPBR can be applied effectively to the removal of nitrate from real wastewater.