Biodegradable polymers have been more attractive for membrane materials, especially poly(lactic acid) (PLA) because they degrade in natural environment after use. In this study, the membranes were developed from a polymer blend of PLA and other biodegradable polymers, such as poly(butylene succinate) (PBS), poly(butylene adipate-co-terphthalate) (PBAT) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The membranes were formed via nonsolvent induced phase separation process using n-methyl-2-pyrrolidone (NMP) as a solvent and water as a nonsolvent. The pure water flux and BSA rejection were tested to determine the filtration performance of membranes. The microstructures and tensile strength of membranes were characterized by field emission scanning electron microscope (FE-SEM) and universal testing machine (UTM), respectively. All of membranes appeared finger-like and sponge-like structures in cross-section, and porous structure on surface. PLA/PHBV blend membranes had pure water flux and BSA rejection as high as PLA/PBS and PLA/PBAT blend membranes. The pure water flux and BSA rejection of the blend ratio (PLA/PHBV/NMP) of 15:1:84 were 65 l/m2•h and 79%, respectively.

The characteristics of foulant in the cake layer and bulk suspended solids of a 10 L submerged anaerobic membrane bioreactor (AnMBR) used for treatment of palm oil mill effluent (POME) were investigated in this study. Three different organic loading rates (OLRs) were applied with prolonged sludge retention time throughout a long operation time (270 days). The organic foulant was characterized by biomass concentration and concentration of extracellular polymeric substances (EPS). The thicknesses of the cake layer and foulant were analyzed by confocal laser scanning microscopy and Fourier transform infrared spectroscopy. The membrane morphology and inorganic elements were analyzed by field emission scanning electron microscope coupled with energy dispersive X-ray spectrometer. Roughness of membrane was analyzed by atomic force microscopy. The results showed that the formation and accumulation of protein EPS in the cake layer was the key contributor to most of the fouling. The transmembrane pressure evolution showed that attachment, adsorption, and entrapment of protein EPS occurred in the membrane pores. In addition, the hydrophilic charge of proteins and polysaccharides influenced the adsorption mechanism. The composition of the feed (including hydroxyl group and fatty acid compounds) and microbial metabolic products (protein) significantly affected membrane fouling in the high-rate operation.

A two-stage submerged anaerobic membrane bioreactor (2-sAnMBR) was operated to demonstrate the technology concept and to accelerate anaerobic biodegradation of Palm Oil Mill Effluent (POME). Then, the impact of different high organic loading rates (OLR) was investigated with a focus on water quality and biogas production. OLR higher than 50 kgCOD.m-3.d-1 induced an increase of volatile fatty acids (VFAs). As a consequence, the biogas production decreased from 19.8 to 11.0 L.d-1 and CH4 yield between 0.23 to 0.38 LCH4/gCODremoved. Nevertheless, the highest OLR (98 kgCOD.m-3.d-1) made it possible to reach a COD removal effectiveness of 70%, where the membrane contribution was around 23.9% to 34.7%. The ratio of propionic acid/acetic acid appeared to be a key indicator to prevent the AnMBR operation failure. Indeed, as soon as the value of 0.7 has been exceeded, several signs of AnMBR failure appeared. The methanogenic activity in AnMBR was inhibited by a hydrolysis ratio of 13% which transformed to VFA accumulation in system. The 250 mg.L-1 of Phenol concentration in POME was an inhibitory of the microbe in this system. Suspended solids concentration, proteins, polysaccharides, and volatile fatty acids were the substantial parameters that influenced the fouling rate.