G.T. Seo

Microalgae membrane photobioreactor for further removal of nitrogen and phosphorus from secondary sewage effluent

For further removal of nitrogen and phosphorus from secondary sewage effluent, two strains of microalgae, Chlorella sp. ADE4 and Chlorella vulgaris, were selected for cultivation in the membrane photobioreactor. The Chlorella sp. ADE4, isolated from wastewater illustrated higher removal efficiency of T-N and T-P, and faster algal growth than the Chlorella vulgaris in a batch experiment using treated sewage effluent. The T-N and T-P removal efficiency was 66.5% and 94.5%, respectively, within HRT of two days when the photobioreactor of Chlorella sp. ADE4 was operated in continuous mode. The effluent water quality was 6.3 mg/L and 0.044 mg/L for T-N and T-P. It was estimated that the algal biomass productivity was 55 mg/L·d with T-N and T-P uptake rates of 6.25 and 0.483 mg/L·d, respectively, in the system. Operational flux below 58 LMH was found to be effective for separation of algal cell from effluent in membrane system.

Effect of nutrient starvation on nutrient uptake and extracellular polymeric substance for microalgae cultivation and separation

AbstractThe purpose of the present study is to investigate the effects of nutrient starvation of microalgae on its nitrogen (N) and phosphorus (P) uptake, characteristics of extracellular polymeric substances (EPS), and algal sedimentation. An experiment was carried out by starving the wastewater-tolerant microalgae Chlorella sp. ADE4. The algal cultivation was put under various conditions of nutrient starvation in order to enhance nutrient removal and algal cell separation. The experimental results showed that 40 h of nutrient starvation prior to the cultivation did affect nutrient removal of Chlorella sp. ADE4. When using synthetic wastewater, the N-starved algae was the most effective in removing 82% of N in 48 h and 92% of P in 24 h. However, the starvation conditions did not cause noticeable removal improvement when microalgae were tested with real wastewater effluent. N and P removal efficiencies of 57 and 100%, respectively, were achieved in 48 h in real wastewater effluent. The lower N removal eff...

Iron oxide nanoparticle-impregnated powder-activated carbon (IPAC) for NOM removal in MF membrane water treatment system

Abstract A novel powder-activated carbon (PAC) by surface modification with iron oxide nanoparticles was applied to microfilter (MF) membrane system for stable operation and removal of natural organic matter (NOM) in water. Two types of PAC (wood-based and coal-based) were used for the preparation of the iron oxide nanoparticle-impregnated PAC (IPAC). The impregnation of the iron oxide nanoparticles played a role to increase the pHPZC of the PACs which means that the IPAC has higher basicity and larger adsorption capacity than the virgin PAC. From the experimental results of size exclusion chromatography (SEC) and SUVA254, there was no specific selectivity in adsorption of NOM on the IPAC. The saturated magnetization value of the IPAC was in the range of 6.75–8.04 emu/g that was enough to separate the IPAC particle from aqueous solution by magnetic force. An IPAC column followed by MF membrane system was operated to investigate NOM removal and membrane fouling control. A magnetic ring on the column above ...

Long Term Operation of Biological Hydrogen Production in Anaerobic Sequencing Batch Reactor (ASBR)

Long term hydrogen production was investigated in an anaerobic sequencing batch reactor (ASBR) using mixed microflora. Glucose (about 8,250 mg/L) was used as a substrate for the ASBR operation under the condition of pH 5.5 and 37°C with mixing at 150 rpm. The experiment was carried out over a period of 160 days. Hydrogen yield was 0.8 mol H2/mol glucose with F/M ratio 2 at initial operation period. The hydrogen yield reached to maximum 2.6 mol H2/mol glucose at 80th day operation. However decreased hydrogen yield was observed after 80 days operation and eventually no hydrogen yield. Although well-known hydrogen producer Clostridium sp. was detected in the reactor by PCR-DGGE analysis, changed reactor operation was the major reason of the decreased hydrogen production, such as low F/M ratio of 0.5 and high propionic acid concentration 2,130 mg/L. Consequently the long period operation resulted in MLSS accumulation and then low F/M ration stimulating propionic acid formation which consumes hydrogen produced in the reactor.

Computational study of NF membrane removal in rejection of specific NOM compounds

ABSTRACT A computational study was conducted to verify natural organic matter removal of two types of nanofiltration (NF) membranes. NF membranes used in this study were fully aromatic polyamide based on trimesoyl chloride and 1,3-benzenediamine (NE90) and semi-aromatic polyamide based on trimesoyl chloride and piperazine with polyvinyl chloride coating (NE70). The solute–membrane interaction was modeled using density functional theory (DFT) to clarify and verify the experiment results of our previous study. The calculations were performed by the calculated highest occupied molecular orbital and lowest unoccupied molecular orbital with frontier orbital gap which reflexed adsorption energy between organic molecules and the membrane surface materials. DFT showed as an effective tool to predict interaction phenomenon between solute and membranes, which is relative to membrane fouling and rejection of particular organic substances. The calculation results showed that carboxylic compound has high-energy gap an...

Effects of Fill Time on the Fractal Dimension and Size of Floc for SBR Treating Low C/N Ratio Wastewater

Abstract The aim of this study was to investigate the effects of fill time of influent on the physical characteristics of biological floc for sequencing batch reactor (SBR) treating low C/N ratio wastewater. The fractal dimension and size of floc were measured for characterizing floc. The fractal dimension of floc was analyzed by using Small Angle Laser Light Scattering (SALLS) method. SBR with short fill time showed higher removal efficiencies of COD, BOD, T-N, and T-P than with long fill time. Larger floc size and fractal dimension were generated at SBR with short fill time. Short fill time generated the sludge with better settling and thickening properties. Alternating anaerobic and aerobic condition in the cycle also affected the floc size and fractal dimension. The floc size decreased under anaerobic phase, and floc size increased under aerobic phase. During fill time, the fractal dimension of floc decreased. As the fill stop, the fractal dimension of floc increased. Therefore, the fill time condition more affected the fractal dimension of floc. More efficient nitrification and phosphorus release were observed during a cycle with short fill time operation.