Feasibility of combined upflow anaerobic sludge blanket-aerobic membrane bioreactor system in treating purified terephthalic acid wastewater and polyimide membrane for biogas purification

Anaerobic processes have become actively practiced for waste and wastewater treatment during the recent years because it can apply for high organic loading whereas the producing biogas can be recovered as a new energy source. This study prompted to look on the feasibility of a combined upflow anaerobic sludge blanket (UASB) and aerated membrane bioreactor (MBR) system for the treatment of purified terephthalic acid (PTA) wastewater and the usage of polyimide membranes for biogas separation. The results revealed that the combined system is robust and flexible in relation to the change in hydraulic retention times (HRTs) and organic loading rates. The overall chemical oxygen demand (COD) removal of 97% with the maximum loading rate of 20 g L−1 per day was achieved at 12 h HRT. The biogas from the UASB reactor was mainly methane (>62%). The separation between CO2 and CH4 was explored using different concentrations of dense polyimide (PIs) membranes and feed pressure. The results revealed that PIs based membranes possess high potential for CH4 purification with high selectivity and permeability towards CO2 than CH4. The expediency of the proposed treatment system and gas-separating module was seen and thus purified biomethane could be mustered continuously.