Eun-Sik Kim

Microbial community analysis of bulk sludge/cake layers and biofouling-causing microbial consortia in a full-scale aerobic membrane bioreactor

Pyrosequencing was used to investigate biofouling-causing microbial consortia at the community level in bulk sludge and cake layers within a full-scale membrane bioreactor (MBR). The analysis revealed Chaos estimates of total operational taxonomic units (OTUs) of 1726, 1806, and 1362 for bulk sludge, cake outer layer, and cake inner layer, respectively. The bulk sludge and cake outer layer OTUs clustered together, whereas the cake inner layer OTUs formed a separate group, indicating that environmental conditions affected the microbial community composition within the MBR. Bacteroidetes, Proteobacteria, and Chloroflexi were the dominant phyla in both the bulk sludge and the cake layers. Comparison at the genus level showed twelve distinct genera in the cake layers that were absent in bulk sludge. Twenty distinct genera were recorded in the inner cake layer. Those genera are likely the microbial colonization pioneers in full-scale membrane bioreactors.

Removal of Heavy Metal Ion in Wastewater by Dendritic Nano-Structured Complex Material

The specific adsorbents for the removal of heavy metal were synthesized by polyamidoamine dendrimer and blast furnace slag, and their physico-chemical properties were evaluated in this study. The batch experiment was evaluated the adsorptive water treatment capability of adsorbent, and the zeta potential and surface morphology were analyzed for evaluating of the material. In result, 10% volume loading adsorbent presented the high yields of heavy metal adsorption in water phase, and Cr (III) interacted highly with dendrimer adsorbents. Furthermore, it was evaluated that the adsorption properties of dendrimer adsorbent were increased with increasing the ligand-to-metal charge-transfer.

Reduction of Fluoride in Water Phase by Micro-Nano Bubble Pretreatment Process

Fluoride is important to aquatic environment and health aspects, and the optimal fluoride concentration in water is below 1 mg/L. In this study, the micro-nano bubble pretreatment was applied to remove fluoride ions in the water phase. The pH control by calcium hydroxide (Ca(OH)₂), and coagulation processes with poly aluminum chloride (PAC), aluminum sulfate (Alum), F900 and two kinds of polymer named as A-polymer and A430P polymer were applied for the pretreated wastewater. In results, the combination of PAC and A430P polymer with micro-nano bubble pretreated wastewater showed a higher fluoride removal than the case of other combinations. In chemical oxygen demand (COD) removal, the combination of Alum and A430P polymer with micro-nano bubble pretreated wastewater showed the best removal efficiency (64.6%) while the COD removal without pretreatment was 71.4% for fluoride and 57.2% for COD.

Environmental Applications of Nano-Sized Recycled Aggregates: The Effect of Sterilization and Adsorption

To evaluate the sterilize efficiency of nano-sized recycled aggregates (RAs), several types of RAs were examined for the purpose of environmental stamping out procedure. The poultry (e.g., chicken) was selected as a target livestock of epidemic disease, and the blast furnace slag (BFS), fly ash (FA), slaked lime (SL), nano-cerium (n-Ce) and shell (Sh) were used as the RAs materials. The fermented solution of effective microorganisms (EM) was added to decompose the target livestock. Various kinds of lab-scale reactor were operated to examine the effects of RAs volume; high and low volume of RAs (e.g., 1.89 w/v% and 1.14 w/v% of RA in solution, respectively), and the effects of EM concentration (e.g., concentrated solution (100%) and diluted solution (12.5%)) with tested in different reaction time. The number of microorganisms after batch tests was counted for the sterilized effects of RAs, and organic matters (e.g., chemical oxygen demand (COD)) and inorganic matters (e.g., suspended solids (SS), heavy metals and potential ions) were analyzed before and after adsorption process. The cases of SL and n-Ce showed high removal of microorganism in the batch of high concentrated EM for 20 days. However the other RA materials were less effective on the sterilization especially in lower volume of RAs. In diluted EM (e.g., 12.5%) tests, most RAs have high sterilization efficiencies in the short periods of batch reaction regardless of RAs types, and it was more effective with longer reaction time. The BFS and n-Ce exhibited higher surface area than others and they adsorbed highly heavy metals in water. The results suggested that the concentration of target organism was the most important to determine sterilization and adsorption properties of RAs.

Nano-Sized Fume Biogas Production from Food Waster Using Semi-Continuous Anaerobic Digester

In this study, the nano-sized fume biogas production from food waste was investigated using lab scale semi-continuous stirred tank reactor (SCSTR) at 35 °C with 30d HRT and 30L working volume. The mesophilic digestion test was performed with three different feed materials (food waste) and food to microorganism (F/M) ratios (0.13, 0.34, and 0.27) in the same experiment. The results showed that the F/M ratios significantly affected the biogas production rate. The highest production rate was obtained at F/M ratio of 0.13. Nano-sized fume biogas produced in anaerobic digestion consists of 68.7% CH4, 31.2% CO2 and 30~200 nm particle. The average nano-sized fume biogas and methane production of digester were 29.96 L/Kg versus day-1 and 20.58 L/Kg versus day-1, respectively. The CH4 could be calculated as the heat energy 1.85 Kcal/Kg VS day-1. The digestion was operated without addition of chemicals or nutrients into the system.

Impact of Nano-Pore Structure in Harden Non-Sintering Cement.

This study investigates the nano pore structure of non-sintering cement (NSC) matrix. The result of pore structure properties showed no considerable difference in the total pore volume, but presented a large distinction in distribution of pore diameter by cement mixing ratio. The pore-diameter of NSC paste shows that occupation ratio of pore diameter below 10 nm was larger and was smaller than ordinary Portland cement (OPC) and blast-furnace slag cement (BSC) at pore diameter of over 10 nm. The reasons are due to the hydrate such as C-S-H gel and ettringite which formed dense nano pore structure of NSC matrix.