A novel polyacrylonitrile (PAN)-based ultrafiltration (UF) hollow-fiber membrane was newly synthesized for nanofiltration (NF) applications. This semi-fully NF hollow-fiber membrane was characterized using a variety of analysis techniques. The membrane exhibited higher negative charge and hydrophilicity and lower surface roughness compared to the pristine UF hollow-fiber membrane. Experiments to study the performance and fouling were simulated under laboratory conditions in a cross-flow system and in–out mode using organic compounds, namely, humic acid and sodium alginate. The removal efficiencies of humic acid and sodium alginate were 65% and 73%, respectively, in the pristine hollow-fiber membrane and 93% and 95%, respectively, in the proposed membrane. The flux decline by natural organic matter was less in the case of the proposed membrane compared to that in the pristine membrane. To mitigate organic fouling on the proposed membrane, sodium hypochlorite (NaClO) was used as a chemical enhanced backwashing agent. At a NaClO concentration of 1 mg/L with a backwashing time of 30 s, an optimal flux recovery of 92.1% of the initial permeability of the PAN-NF hollow-fiber membrane was achieved with less membrane degradation. The results of this study will provide practical insight and act as a technical guide for NF-based plant engineers/operators.

The purpose of this study is to conduct drought vulnerability assessment and cluster analysis of Korean island areas at eup (town) myeon (subcounty) level. Drought vulnerability assessment was conducted using factor analysis and entropy method, and cluster analysis was analyzed using K-means, a nonhierarchical cluster analysis method. Vulnerability consisted of climate exposure, sensitivity, and adaptive capacity. Twenty-two indicators were used to evaluate and analyze vulnerability of drought in small island areas. The results of entropy method showed that winter rainfall, no rainfall days, agricultural population rate, cultivation area rate, water supply rate and groundwater capacity have a substantial impact on drought assessment. The overall assessment of vulnerability indicated that Seodo-myeon Ganghwa-gun, Seolcheon-myeon Namhae-gun, and Samsan-myeon Ganghwa-gun were most vulnerable to drought. The cluster analysis was evaluated by categorizing the regions into three clusters, and policy support and planning are needed to suit the characteristics of each cluster was observed.

Fiber media filtration for combined sewer overflow (CSO) treatment was evaluated in this work. Pilot-scale experiments of CSO treatment involve seven layers that form radial-type fiber media filters. The fiber media filter was characterized using analysis techniques and exhibited extremely high hydrophobicity and negative charge. The results obtained for a sewer treatment plant at Tancheon in Seoul revealed potential for suspended solid, total organic carbon, and biochemical oxygen demand removal with efficiencies of 89.6%, 56%, and 42%, respectively. The results are consistent with the sieving effects and electrostatic repulsion between fiber media and pollutants. Head loss was induced by organic pollutants and was 10.5 cm after 20 h of operation. To mitigate the head loss induced by organic pollutants on the fiber media filter, sodium hypochlorite (NaClO) was used as a chemical backwashing agent. An NaClO concentration of 2000 mg/L with a soaking time of 24 h yielded an optimal head loss recovery of 96.2% of the initial head loss obtained for the virgin fiber media filter without media filter degradation. The result of the present study will provide practical insight and act as a technical guide for CSO treatment plant engineers.