Evaluating the Optimal Oil Concentrations in the Startup Performance of a Membrane Bioreactor Treating Oily Noodle-soup Wastewater.

The discharge of high-strength oily wastewater adversely affects the environment; therefore, the treatment of wastewater containing fats, oils, and grease from the food industry is of importance. In this study, we used a membrane bioreactor (MBR) to treat Ramen noodle-soup wastewater, and we evaluated the optimal oil concentration in the wastewater for the startup of the MBR treatment in winter and summer. The MBR system had a sufficient startup in both seasons when fed with a 20-fold dilution of the original oily wastewater, containing approximately 950 to 1,200 mg/L oil and approximately 3,000 to 4,400 mg/L biological oxygen demand (BOD; BOD-SS load of 0.1 to 0.2 kg/kg/d). The reactor performance in winter were relatively stable during the operation. While, activated sludge microbes in summer were not highly active with a 40-fold dilution of wastewater, because of the decreased mixed liquor suspended solid concentration during the operation period. Population shifts in the sludge microbiome with increasing oil concentrations were analyzed using high-throughput sequencing, and the relative abundance of operational taxonomic units belonging to the phylum Bacteroidetes were highest in both winter and summer when fed with 20-fold dilution of the wastewater. In particular, the family Chitinophagaceae was dominant, with relative abundances of 13.5% in winter and 5.1% in summer, suggesting that this family may play important roles in the startup of a MBR treating the wastewater.

Activated sludge microbiome in a membrane bioreactor for treating Ramen noodle-soup wastewater.

Population shifts in the activated sludge microbiome of a membrane bioreactor (MBR) during the treatment of Ramen noodle-soup wastewater were analyzed by high-throughput sequencing. An MBR underwent stable treatment of wastewater containing increasing oil concentrations (from 135 to 1,350 mg/L) for 26 days; however, after feeding with wastewater containing 2,700 mg/L of oil, the mixed liquor suspended solids and transmembrane pressure exhibited gradual and rapid increases, respectively, leading to clogging of the membrane. Phylogenetic analysis revealed an oil supply-dependent increase in the abundance of Cupriavidus gilardii (relative abundance of 26.2% at Day 30) in the sludge together with Parasegetibacter terrae (9.9%) and Ferruginibacter yonginensis (9.4%). These dominant species may play important roles in noodle-soup wastewater treatment.