Yun-Chul Chung

Novel method for enhancing permeate flux of submerged membrane system in two-phase anaerobic reactor

A two-phase anaerobic reactor system with a submerged membrane in the acidogenic reactor was designed for the enhancement of organic acid conversion and methane recovery. A submerged membrane system in a two-phase anaerobic reactor was tested to increase the sludge retention time (SRT) of acidogen and to enhance the solid separation. The pilot plant experiment was performed for piggery wastewater treatment for a year. The membrane material used was mixed esters of cellulose of 0.5 micron pore size. COD removal efficiency was 80% and the methane production showed 0.32 m3/kg COD removed for the submerged membrane system in the anaerobic digester. As the cake resistance of the membrane caused a serious problem, a stainless-steel prefilter and air backwashing methods were applied to minimize the cake resistance effectively. Among the tested prefilters, the 63 microns pore prefilter showed the best performance for reducing cake resistance and a successful long-term operation. By cleaning with alkali first and acidic solutions later, the permeate flux decreased by long-term operation was recovered to 89% of that with a new membrane.

Use of coagulant and zeolite to enhance the biological treatment efficiency of high ammonia leachate.

ABSTRACT Most landfill leachates in Korea, herein defined as the contaminated liquid resulting from the percolation of water through a landfill, are high in ammonium nitrogen, which inhibits biological treatment processes and deteriorates rivers. A laboratory experiment investigated the effect of pre-removal of ammonium nitrogen using zeolite on the efficiency of organic treatment of the following activated-sludge process. Ferric chloride was initially used as a coagulant for solids removal. A clinoptilolite and mordenite rich rock from the Guryongpo area, the Yeongil Basalt, in Korea, reduced the ammonia nitrogen concentrations of leachate from 1300–1500 to 110–130 mg/l in a 24 h batch operation. Three activated sludge reactors were operated to compare treatment efficiency under different influent conditions. In reactor 1, leachate having high concentration of chemical oxygen demands (COD) and suspended solids (SS) was directly fed to the reactor without pretreatment. The supernatant, after the coagulation process that remove some suspended solids and COD, was fed to reactor 2. As the use of coagulation process alone is not effective to remove ammonium nitrogen, supernatant treated by both coagulation focusing on the removal of COD and the zeolite concentrating on the removal of ammonium nitrogen was fed to reactor 3. As the result of experiment, greater efficiency in lowering the chemical oxygen demand (83%, influent COD; 1800–3000 mg/l, effluent COD; 300–500 mg/l) was achieved in reactor 3. Meanwhile, 63% (influent COD; 4000–5000 mg/l, effluent COD; 1470–1840 mg/l) and 66% (influent COD; 2400–3300 mg/l, effluent COD; 820–1100 mg/l) removal efficiency of COD were achieved in reactors 1 and 2, respectively. Thus, ammonia pre-removal by zeolite remarkably improved the lowering of chemical oxygen demand and the solids separation in the activated sludge process.

Effects of grain shape and texture on the yield strength anisotropy of Al-Li alloy sheet

The in-plane anisotropy of yield strength in aluminum-lithium (Al-Li) alloys has been attributed to crystallographic textures, grain morphologies, and directional precipitates. Hot-rolled Al-Li alloys are reported to exhibit the minimum yield strength near 45{degree} to the rolling direction due to rolling textures (i.e., Cu, S and Bs components in {beta}-fiber) and elongated grains. During recrystallization treatment in the thermo-mechanical processing, continuous recrystallization (CRX) or discontinuous recrystallization (DRX) can take place. It is known that CRX occurs by formation and growth of subgrains, while the DRX occurs by growth of newly developed nuclei with different crystal orientations from those of original grains. CRX hardly alters texture, on the contrary DRX completely changes the texture. The grain morphology of CRX, affected by rolling and recrystallization conditions, can be controlled without changing crystallographic textures. In this work, equiaxed grains with rolling textures are obtained by CRX, and the contributions of grain shape and texture to the in-plane anisotropy of yield strength have been identified in an Al-Li-Cu-Mg-Zr-Mn alloy.

Biological nitrogen removal using a modified oxic/anoxic reactor with zeolite circulation

A modified, laboratory-scale, oxic/anoxic process with zeolite circulation achieved a high efficiency (97%) of nitrogen removal from synthetic wastewater. This process lowered the turbidity and the suspended solid concentration in the effluent. The zeolite was effective as a biomedium due to the formation of biofilm on the surface of zeolite and the continuous biological regeneration.

Effect of pH on Phase Separated Anaerobic Digestion

A pilot scale experiment was performed for a year to develop a two-phase anaerobic process for piggery wastewater treatment (COD: 6,000 mg/L, BOD: 4,000 mg/L, SS: 500 gm/L, pH 8.4, alkalinity 6,000 mg/L). The acidogenic reactor had a total volume of 3 m3, and the methanogenic reactor, an, anaerobic up-flow sludge filter, combining a filter and a sludge bed, was also of total volume 3 m3 (1.5 m3 of upper packing material). Temperatures of the acidogenic and methanogenic reactors kept at 20°C and 35°C., respectively. When the pH of the acidogenic reactor was controlled at 6.0–7.0 with HCl, the COD removal efficiency increased from 50 to 80% over a period of six months, and as a result, the COD of the final effluent fell in the range of 1,000–1,500 mg/L. BOD removal efficiency over the same period was above 90%, and 300 to 400 mg/L was maintained in the final effluent. The average SS in the final effluent was 270 mg/L. The methane production was 0.32 m3 CH4/kg CODremoved and methane content of the methanogenic reactor was high value at 80–90%., When the pH of the acidogenic reactor was not controlled over the final two months, the pH reached 8.2 and acid conversion decreased compared with that of pH controlled, while COD removal was similar to the pH controlled operation. Without pH control, the methane content in the gas from methanogenic reactor improved to 90%, compared to 80% with pH control.

Ammonium exchange and bioregeneration of bio-flocculated zeolite in a sequencing batch reactor

Natural zeolite was added to the sequencing batch reactors to assess its role in ammonium exchange. Even though the biofilm was fully developed on the zeolite surface, ammonium removal and the biological regeneration of the zeolite occurred constantly during the anoxic-fill phase and the reaction phase, respectively. However, the specific nitrification rate of the bio-flocculated zeolite was lower than that observed in the control on account of the limited ammonium release to the liquid phase.

The effect of silver addition on 7055 Al alloy

Abstract The effect of silver addition on the microstructure and mechanical properties of the 7055 Al alloy was investigated. Mechanical properties of various alloys used in this study are correlated with the formation of constituent particles and microstructural changes of fine precipitates. According to the experiment, tensile strength of the 7055 Al alloy decreased by the addition of silver, although silver additions were observed to refine η′. The low tensile strength is attributed to the relatively low number density of η′ in silver-bearing alloys in which a large amount of hardening elements, such as Zn and Mg, are consumed to form silver-bearing constituent particles.

Optimization of the mechanical strength of PVA/alginate gel beads and their effects on the ammonia-oxidizing activity

AbstractPoly (vinyl alcohol) (PVA)/alginate gel beads were fabricated to entrap ammonia-oxidizing bacteria. The PVA/alginate gel beads were prepared in different conditions to investigate the effects of the fabrication procedures on the mechanical strength and the initial ammonia-oxidizing activity. For the mechanical strength, the optimal conditions were analyzed using response surface analysis (RSA) considering the inter-correlated effects of the reaction times of cross-linking and phosphorylation. For RSA, nine trials resulted in a partial cubic polynomial equation, which best predicted the amount of residual debris after homogenization. In the model, the optimum conditions of 3.5 h of cross-linking and 5.6 h of phosphorylation were estimated to ensure the maximum mechanical strength. The initial ammonia-oxidizing activity was significantly affected by the cross-linking due to the highly acidic environment of pH 3.3, but it was not affected by the phosphorylation in pH 4.2. Batch experiments to measure...

Increased removal of nickel and organics in the upflow anaerobic sludge bed filter reactor using sulfate and sulfide additions

Glucose (total organic carbon: 1,200 mg/l) and nickel (0 to 40 mg/l) were added to an anaerobic upflow sludge bed filter reactor. The removal efficiencies of total organic carbon and nickel were maintained to 95% and 98.5%, respectively, since nickel was precipitated with sulfide which was converted from sulfate added at 80 mg SO4-S/l by sulfate reducing bacteria. Sulfate therefore enhances its organic removal efficiency of AUBF reactor under the presence of heavy metal.

Study of Nitrogen and Organics Removal in Sequencing Batch Reactor (SBR) Using Hybrid Media

Abstract The removal of nitrogen and organics in a sequencing batch reactor (SBR) using hybrid media were investigated in this work. The hybrid media was made by the use of polyurethane foam (PU) cubes and powdered activated carbon (PAC). The function of activated carbon of hybrid media was to offer a suitable active site, which was able to absorb organic substances and ammonia, as well as that of PU was to provide an appropriated surface onto which biomass could be attached and grown. A laboratory-scale moving-bed sequencing batch reactor (SBR) was used for investigating the efficiency of hybrid media. The removal of nitrogen and organics for synthetic wastewater (COD; 490–1,627 mg/L, 180–210 mg/L) were evaluated at different COD/N ratio and different anoxic phase conditions, respectively. The system was operated with the organic loading rate (OLR) of 0.1, 0.16, 0.24, and 0.28 kg COD/m3 day, respectively. Each mode based on OLR was divided as the periods of 45 days of operation time, except for third mode that was operated during 30 days. After acclimatization period, effluent total COD concentrations slightly decreased and the removal efficiency of organics increased to about 90% (COD; 70 mg/L) after 60 days and achieved 98% (COD; 30 mg/L) at the end of experiments. The organics reduction seemed to be less affected by shock loading since high organic loads did not affect the removal efficiency. The concentrations in effluent showed almost lower than 1 mg/L and concentrations were high (150 mg/L) during a very low C/N ratio (C/N = 2). Over 90% of T-N removal efficiency (T-N; 16 mg/L) was obtained during the last 20 days of the operation after controlling the COD/N ratio (C/N = 7). The mixing condition and COD/N ratio at anoxic phase were determined as a main operating factors. In future, the optimal operating conditions of SBR system with hybrid media will be investigated from the view of maintaining a sufficient biomass to the hybrid media under the vigorous mixing conditions.