Development of Membrane Bioreactor Employing Commercial and Modified Membranes for Wastewater Treatment in Bangladesh

Abstract

Industries across various sectors are exacerbating water pollution through the direct discharge of untreated wastewater into natural ecosystems. Traditional wastewater treatment approaches often prove inadequate in mitigating pollutants. However, membrane bioreactors (MBRs) emerge as a promising remedy with membranes constituting the fundamental element of the system. MBRs are the favored choice for treating high-strength wastewater as all the bacteria are retained within the reactor which can degrade the toxic and bio-degradable matters present in the wastewater. Globally, MBR systems with different setups have been seen widespread utilization for treating various wastewater across lab and pilot scales. However, implementation of MBR technology for wastewater treatment in Bangladesh is relatively new, and research conducted at both laboratory and industrial scales remains limited. This research investigates the fabrication and effectiveness of blended membranes using polyethersulfone (PES) and commercially available polysulfone (PSF) as matrix for wastewater treatment in a submerged MBR. In the first phase, commercially available PSF polymer was mixed with polyethylene glycol (PEG) and sodium alginate (SA) to fabricate PSF-PEG and PSFSA blended membranes applying the non-solvent induced phase separation (NIPS) method, where PSF-PEG membranes exhibited higher performance in terms of porosity (9.25%) and flux (308 L/m2h) compared to PSF-control and PSF-SA membranes. For synthetic textile wastewater treatment using MBR, both PSF-PEG and PSF-SA membranes achieved 87-89% removal of COD and about 90% removal of BOD5 while PES-commercial membrane demonstrated 90% COD and 92% BOD5 removal. However, color removal efficiency of fabricated membranes was lower compared to a PES-based commercial membrane. In the second phase, PES polymer was blended with PEG and polyvinylpyrrolidone (PVP) to fabricate PES-PEG and PES-PVP membranes. The PES-PEG blended membrane, incorporating 3 wt.% PEG, exhibited the highest porosity of 28.64% and a flux of 1328 L/m2h, outperforming the PES-control membrane with a porosity of 2.73% and a flux of 226 L/m2h. Conversely, the PES-PVP blended membrane, optimized with 5 wt.% PVP, showed porosity of 15.04% and a flux of 660 L/m2h. During MBR operation of synthetic textile treatment, PES-PEG and PES-PVP membranes showed high efficiency in removing BOD5 (93-94%), COD (95-96%), and color (93-94%) compared to the PES-based commercial membrane. Despite differences in permeate flux, all fabricated membranes demonstrated significant efficacy in microorganism removal akin to the PES-based iv commercial membrane. In the third phase, a real industrial wastewater collected from a CETP was subjected to treatment using both fabricated (PES-3PEG) and commercial membranes using MBR. The results demonstrated exceptional efficiency in eliminating organic matter removal across both membranes, achieving about 93% removal for COD and 88-89% for BOD5 after 28 days of continuous operation.