Interaction mechanisms of fouling and cleaning protocol for A/O-MBR treatment of coal⁃to⁃hydrogen wastewater

Abstract

The anoxic/aerobic membrane bioreactor (A/O-MBR) was conducted to investigate pollutants removal in coal⁃to⁃hydrogen wastewater at the pilot experiment. Results showed that the system exhibited effective removal of chemical oxygen demand (∼90%), ammonia nitrogen (>95%), and total phenols (>95%). Moreover, the Extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) approach was used to predict the MBR system's membrane fouling and chemical cleaning mechanisms in the MBR system. The results indicated that the initial stage dominated membrane fouling by the acid-base (AB) interaction energy. With aggravated membrane fouling, the determinate role was the van der Waals (LW) interaction energy. Furthermore, the cleaning agent NaClO obtained the highest trans-membrane pressure recovery (104.7% of the virgin trans-membrane pressure) in CGW treatment, compared with HCl or NaOH cleaning. It was attributed to the higher LW interaction energy between foulants and the NaClO-cleaned membrane than those between foulants and the HCl-/NaOH-cleaned membrane. Meanwhile, it could effectively restrain AB interaction energy decline between them. The findings of this study confirmed successful development of A/O-MBR for bio-refractory CGW treatment with NaClO chemically enhanced backwash. It also provided an in-depth understanding on the fouling and cleaning mechanisms of the MBR system.