Weiwei Huang

Investigation of the mechanisms of membrane fouling by intracellular organic matter under different iron treatments during ultrafiltration

Iron is an important trace element in algal growth and water eutrophication. This study focused on the ultrafiltration (UF) membrane fouling mechanism by the intracellular organic matter (IOM) of Microcystis aeruginosa under different iron treatments. The results indicated that the membranes experienced faster flux decline and worse fouling reversibility when the IOM formed under low iron concentrations. In contrast, less IOM membrane fouling was found under normal and high iron concentrations. The mass balances of the dissolved organic carbon (DOC) content implied that the IOM in the low-iron treatment was associated with higher IOM retention and a higher capacity of reversibly deposited organics, whereas more IOM in the high-iron treatment passed through the UF membrane. The IOM in the low-iron treatment was composed of more biopolymer macromolecules, whereas the IOM in the high-iron treatment contained more UV-absorbing hydrophobic organics. The fluorescence excitation-emission matrix (EEM) spectra coupled with peak-fitting analysis implied that the fouling associated with protein-like components was more irreversible in the low-iron treatment than those in the normal- and high-iron treatments. Cake formation combined with intermediate blocking was identified as the main membrane fouling mechanism responsible for the flux decline caused by IOM solutions in the three iron treatments in this study.

Fate and UF fouling behavior of algal extracellular and intracellular organic matter under the influence of copper ions

Copper ion plays an important role in the outbreak of algal blooms. The aim of this research was to investigate the fate and fouling behavior of algal extracellular organic matter (EOM) and intracellular organic matter (IOM) under different copper concentrations during ultrafiltration (UF). Under the lowest copper concentration of 0.01 μmol/L, both the EOM and IOM caused the largest decrease in filtration flux, followed by EOM under high copper concentrations of 0.3 μmol/L and 0.1 μmol/L; less membrane fouling was induced by IOM under a copper concentration of 0.3 μmol/L than under a copper concentration of 0.1 μmol/L. More reversible fouling (Rre) was induced by EOM/IOM at the lowest copper concentration of 0.01 μmol/L than under the other two copper concentrations, whereas more membrane fouling was induced by EOM than by IOM under the different copper concentrations. Fluorescence excitation-emission matrices-parallel factor analysis (PARAFAC) indicated that fouling by the protein-like components in EOM was more irreversible under 0.01 μmol/L copper than under 0.1 μmol/L and 0.3 μmol/L copper. However, the fouling by this component was more reversible in the IOM solutions than in the EOM solutions. The amount of macromolecular biopolymers was highly correlated with the total and reversible membrane fouling during the EOM/IOM filtration, whereas a weaker correlation (r2) between the humic-like organics and membrane fouling was determined by Pearsons correlation matrix analysis. High-performance size exclusion chromatography (HPSEC) combined with peak-fitting prediction was suggested to be more suitable for membrane fouling implication in algal water treatment.

Microplastic pollution in rice-fish co-culture system: A report of three farmland stations in Shanghai, China

Microplastics are emerging contaminants of increasing concern. Despite the occurrence of microplastics in farmland soils, the knowledge on microplastics in rice-fish co-culture ecosystems is limited. In this study, we investigated the distribution of microplastics in three rice-fish culture stations in Shanghai. During non-rice and rice-planting periods, microplastics in water, soils and aquatic animals (eel, loach and crayfish) were systematically assayed using methods of NaCl density extraction, H2O2 digestion and micro-fourier transform infrared spectroscopy. Results showed that average microplastic abundances were 0.4 ± 0.1 items L-1, 10.3 ± 2.2 items kg-1, 1.7 ± 0.5 items individual-1 in water, soils and aquatic animal samples, respectively. We found an increasing trend in microplastic abundances in water, soil and animal samples from non-rice period to rice-planting period. Almost all of microplastics were found in digestive tracts of animals. Major microplastics were small (<1 mm) polyethylene and polypropylene fibers, with color of white and translucent. Size, shape, color and polymer type distributions of microplastics were similarly found in environmental and animal samples. Moreover, microplastic abundances in aquatic animals correlated to abundance in farmland soils. This study, for the first time, reveals the occurrence and characteristics of microplastic pollution in rice-fish culture ecosystem which suggests the potential ecological risks of microplastics in the agroecosystem.