The Change of Forward Osmosis Filtration Performance by Trace Organic Compounds in Heavy Metal Removal by Forward Osmosis Filtration

Objectives : The purpose of this study was to examine how the presence of trace organic compounds (TROCs) affects water flux and heavy metal rejection in forward osmosis (FO) filtration when feed solution (FS) contains TROCs and heavy metals.Methods : Four FS (① only heavy metals, ② heavy metals and Trimethoprim, ③ heavy metals and Ibuprofen, ④ heavy metals and Triclosan) were used, and the FO filtration experiments were conducted to perform comparative analysis on the water flux and the rejection rate depending on the FS type.Results and Discussion : The water flux was higher when FS contained TROCs except Ibuprofen, compared to FS containing only heavy metals. It is speculated that the increased water flux was influenced by the decrease in the internal concentration polarization (ICP), which was caused by the adsorption of the TROCs in the support layer of the membrane. The water flux decreased when FS contained Ibuprofen, and this may be because reverse salt flux increased due to the Gibbs-Donnan effect. The rejection rate was not affected by TROCs when heavy metals were mostly rejected in FO filtration, but for the heavy metal that was not fully rejected, the rejection rate increased when FS contained TROCs. It is speculated that this was mainly due to clogging caused by the adsorption on the membrane.Conclusions : It was demonstrated that the presence of TROCs in FS can affect water flux and the rejection rate of heavy metals. Therefore, when the FS containing heavy metals and various organic substances is treated by FO filtration, the performance of the filtration is expected to change depending on the composition of the solution.

Fate of Trace Organic Compounds in Hyporheic Zone Sediments of Contrasting Organic Carbon Content and Impact on the Microbiome

The organic carbon in streambed sediments drives multiple biogeochemical reactions, including the attenuation of organic micropollutants. An attenuation assay using sediment microcosms differing in the initial total organic carbon (TOC) revealed higher microbiome and sorption associated removal efficiencies of trace organic compounds (TrOCs) in the high-TOC compared to the low-TOC sediments. Overall, the combined microbial and sorption associated removal efficiencies of the micropollutants were generally higher than by sorption alone for all compounds tested except propranolol whose removal efficiency was similar via both mechanisms. Quantitative real-time PCR and time-resolved 16S rRNA gene amplicon sequencing revealed that higher bacterial abundance and diversity in the high-TOC sediments correlated with higher microbial removal efficiencies of most TrOCs. The bacterial community in the high-TOC sediment samples remained relatively stable against the stressor effects of TrOC amendment compared to the low-TOC sediment community that was characterized by a decline in the relative abundance of most phyla except Proteobacteria. Bacterial genera that were significantly more abundant in amended relative to unamended sediment samples and thus associated with biodegradation of the TrOCs included Xanthobacter, Hyphomicrobium, Novosphingobium, Reyranella and Terrimonas. The collective results indicated that the TOC content influences the microbial community dynamics and associated biotransformation of TrOCs as well as the sorption potential of the hyporheic zone sediments.