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( Wookeun Bae ),( Jin-wook Chung ),( Eon-bin Shin ),( Young-jin Cho ),( Jong-ho Kim ),( Gwaug-beom Ko ) 한국폐기물자원순환학회 2002 APLAS Vol.2002 No.1
Leachates from aged landfills are often rich in ammonium nitrogen although the concentration of organic matter is relatively low. This study was performed to evaluate the possibility of applying leachate recirculation to enhance landfill stabilization. The concept of this technology is that ammonium in the leachate is nitrified to nitrite in an above-ground reactor and then the leachate containing nitrite is recirculated to the landfill, in which nitrite is reduced to nitrogen gas. Column experiments were conducted to demonstrate the feasibility of denitrification in a landfill. Shortcut biological nitrogen removal (SBNR) process was tested to see how ammonium in the leachate converted to nitrite under certain operating conditions, using a pilot- scale reactor. The results were: 1) Nitrite was denitrified in a landfill material, apparently consuming less COD than in nitrate denitrification; 2) Ammonium in the leachate converted to nitrite under an alkaline pH around 8. A logical combining of the two results leaded to an expectation that a leachate of high ammonium could be treated in-situ by leachate recirculation and SBNR technology. An experiment that combines the SBNR technology and the in-situ nitrite denitrification is undergoing, using six sets of lab-scale reactors and a pilot-scale plant.
Design of a Wearable Hand Rehabilitation System for Quantitative Evaluation of the Stroke Hand
Jeongsoo Lee,Wookeun Park,Suin Kim,Joonbum Bae 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10
In this paper, the design of a hand rehabilitation system is introduced for evaluating the hand function and performing the hand rehabilitation. In an attempt to evaluate the hand function such as a finger stiffness, a finger independency, a multi-finger synergy quantitatively, the finger joint angles and the external force to the finger should be measured via the device. In addition, the device assists voluntary/involuntary movement of the hand flexion/extension motion for hand rehabilitation and the device can apply the force to each finger. In order to find the additional requirements, an expert’s group interview was performed. According to the interview, several requirements for designing the rehabilitation system were found and these are categorized as four parts (wearability, durability, soft contacting with skin and stability). Based on the above requirements, several structure design candidates are introduced and analyzed for each candidate’s merits and demerits with numerical simulation. Total system configuration using the final design and future works are introduced in the last part of this paper.
Park, Seongjun,Bae, Wookeun,Rittmann, Bruce E. Wiley Subscription Services, Inc., A Wiley Company 2010 Biotechnology and Bioengineering Vol.105 No.6
<P>A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and oxygen limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients. Biotechnol. Bioeng. 2010;105: 1115–1130. © 2009 Wiley Periodicals, Inc.</P>
Kim, Seungjin,Bae, Wookeun,Kim, Moonil,Kim, Jong-Oh,Chung, Jinwook Taylor Francis ; Publications Division, Selper Ltd 2015 Environmental Technology Vol.36 No.8
<P>A two-stage biological aerated/anoxic filter (BAF) system for denitrification-nitrification was developed to increase nitrogen removal in the treatment of municipal wastewater with low carbon:nitrogen (C/N) ratio [Formula: see text]. This system exhibited a high denitrification efficiency (67%), despite the low C/N ratio, and the ratio of reduced nitrate to consumed organic compounds was greater than the theoretical value due to the minimization of the conversion of organic carbon to biomass growth, the maintenance of low levels of dissolved oxygen in recycled water, and the maximization of use of organic carbon biosorbed inside biomass in the denitrification BAF. The maximum rate of nitrogen removal was achieved at a recycle ratio of 170%, and the headloss in two BAFs was maintained after a 24-h backwash. Biological nitrogen removal in a two-stage BAF system was possible in a short hydraulic retention time (1.2???h) because the maximum reaction rates of nitrifiers and denitrifiers in each column were achieved.</P>
Chung, Jinwook,Bae, Wookeun,Lee, Yong-Woo,Ko, Gwang-Beom,Lee, Sang-Uk,Park, Seong-Jun Taylor Francis 2004 Journal of Environmental Science and Health. Part Vol.39 No.7
<P>A shortcut biological nitrogen removal (SBNR) process was operated to treat an ammonium rich landfill leachate using a pilot-scale reactor. The SBNR process was intended to oxidize ammonia to nitrite and, then, to reduce it to nitrogen gas. When the hydraulic retention time was 4–3 days, a half of the ammonium oxidized was accumulated as nitrite in the oxidation tank. The nitrite was denitrified completely in the anoxic tank when recycled. The average free ammonia (FA) concentration in the ammonium oxidation tank was 3.7 mg/L. The specific substrate utilization rates of ammonium oxidizers and nitrite oxidizers were investigated at varying FA concentrations through batch experiments. The highest specific ammonium oxidation rate was observed when the FA concentration was 10 mg/L. The rate decreased slightly when the FA concentration was increased to 20 or 50 mg/L, or decreased significantly when it was 5 mg/L. In case of nitrite oxidation, the specific nitrite utilization rate decreased significantly with increasing FA concentration up to 10 mg/L. Consequently, the optimal FA concentration in leachate treatment was 10 mg/L for maximum nitrite accumulation and maximum ammonium removal, or 5 mg/L for lower ammonium concentration and reasonable nitrite accumulation.</P>