• Journal of Environmental Science International
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• v.2 no.4
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• pp.299-310
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• 1993

This study was aimed to evaluate the effects of effluent recycling on the UASB reactor performances at the various organic loading rates and influent substrate concentrations. The organic removal efficiency of the reactors operated with effluent recycle were above 85%. However, the efficiencies of the reactors operated without the recycle were below 40% even though the effort to increase the efficiencies was made by changing the influent substrate concentrations and the organic loading rates, and introducing the effluent recycle at the final stage of the experiment. It was realized that the certain amount of effluent recycling from the start-up stage in UASB reactors seemed to be necessary to provide the effective contact chances between the substrate and granular sludge for better performances of the UASB process.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.19-21
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• 2007

In recent, a great number of electric motor units (EMUs) have been disused in Korea according as its legal duration is 25 years. Generally, the disused EMUs are disposed by selling original form or scrapping for junk. Until now, any efficient disposal system for disused EMUs has not existed. The purpose of this study was to develop the recycling process for the FRP used as an interior panel of EMU. This process was to manufacture a product mixing binders, fillers and the powdered FRP. The characteristics of a product were changed with the mixing ratio of the powdered FRP. The optimal ratio of the powdered FRP was from 10 % to 15 % (w/w). In the future, the application of this process can enhance the efficiency of resource recycling and decrease the cost of waste treatment in the EMU industry.

• Resources Recycling
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• v.13 no.4
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• pp.46-52
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• 2004

The present main research direction of waste treatment is the development of incineration system for low pollution. Also, heat value of waste is increased because of the rising of living standard, environmental consideration and collection of sorted waste for recycling. Therefore, many researches have been continued for solving ash problem including heavy metals, dioxin problem and high energy efficiency by use of high heat value. This study is described for the facilities of pyrolysis system, pyrolysis-melting system, pyrolysis-gasification melting system.

• Resources Recycling
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• v.28 no.6
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• pp.73-78
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• 2019

In this investigation, off-gas generated from the activated sludge in wastewater treatment plant was monitored. Through monitoring, the oxygen transfer efficiency in the aeration system and the reliability was evaluated by comparing to clean water. First, the dissolved oxygen, oxygen transfer coefficient, and standard oxygen transfer efficiency were measured based on clean water, and the values were 8.60 mg/L, 9.490/hr and 23.96%, respectively. The off-gas monitoring at the wastewater treatment plant indicated that the standard oxygen transfer efficiency was 22.81%. Little difference in oxygen transfer efficiency this data inferred that the performance was improved through diffuser installation in the field monitoring system.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.69-75
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• 2020

This study was conducted to improve the solid-liquid separation efficiency of clarifiers. To do so, the study did a bio-flocculation experiment simply by controlling the stirring speed (rpm) and baffle angle of a clarifier on a lab scale, but without using a coagulant. For the purpose of the experiment, the feed wall of a clarifier was so improved that a baffle could be installed on the clarifier. Then, it was ensured to change its stirring speed (to 0.0rpm, 0.6rpm, and 1.2rpm), with the angle fixed at 10°. As a result, it was found that concentration efficiency increased by 2.0%, and effluent removal efficiency (SS concentration) by 7.8%, at a stirring speed of 0.6ppm. This indicates the bio-coagulation efficiency of sludge increased with changing stirring speeds. Then, the baffle angle of the sedimentation unit was changed to analyze how the changed baffle angle would affect the sedimentation of sludge. As a result, it was found that the compression of sludge interface was very effective at a baffle angle of 20°. It is hoped that these experimental findings will be useful in improving the sedimentation efficiency of circular clarifiers.

• Journal of information and communication convergence engineering
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• v.15 no.1
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• pp.62-71
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• 2017

This paper presents a low-power voltage converter based on a reconfigurable capacitor array. Its energy recycling capacitor array stores the energy during a charge stage and supplies the voltage during an energy recycle stage even after the power source is disconnected. The converter reconfigures the capacitor array step-wise to boost the lost voltage level during the energy recycle stage. Its energy saving is particularly effective when most of the energy remaining in the charge capacitors is wasted by the leakage current during a longer sleep period. Simulations have been conducted using a voltage source of 500 mV to supply a $V_{DD}$ of around 800 mV to a load circuit consisting of four 32-bit adders in a 65-nm CMOS process. Results demonstrate energy recycling efficiency of 85.86% and overall energy saving of 40.14% compared to a conventional converter, when the load circuit is shortly active followed by a long sleep period.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.4
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• pp.81-90
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• 2009

About 35 domestic incinerators are being operated currently. There is waste management policy to reuse waste efficiently and reduce waste through incineration which include reuse, recycling and energy recovery. However, there is a critical social issue that some heavy metals(Cu, Pb) were found in bottom ash from incineration of waste. After incineration, bottom ash is treated with chemicals to prevent second pollution of heavy metals from bottom ash and increase efficiency of heavy metal stabilization.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.4
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• pp.27-33
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• 2008

Polyethylene terephtahalate has been used in several areas such as fiber, film, bottle, and disposable products. Production of PET has been rapidly increasing these days. Since PET is a semi-permanent material, it has a non-biodegradable character in itself. Wasted PET products can cause serious environmental problems. Many countries around the world impose environmental legal restrictions over their abandonments. Many researches on the enviromental influence factors and treatment techniques of the wasted PET have been carried out. The main objective of this study is to develop a new sizing agent using recycling PET and improve its internal sizing effect. Dried powder of PET was used to make the modified PET. After extracting water-dispersible PET by subcritical hydrolysis, polyester resins have been extracted and triphenyl phosphate(TPP) has been added to obtain optimal internal sizing agent. It was found that the optimum dosage of TPP was 2% (per PET weight) and the hydrolysis temperature was independent on making the modified PET.

• Journal of Environmental Science International
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• v.21 no.10
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• pp.1255-1263
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• 2012

Batch cultivations were performed to evaluate the influences of the initial pH condition on mesophilic and thermophilic acidogenic fermentation with food waste recycling wastewater. In both conditions of mesophilic and thermophilic fermentation, TVFAs production rates were maximized at the initial pH 7 condition as 0.15 and 0.23 g TVFAs/L hr, respectively. And pH was also maintained stably between 6 and 7 during 72hr acidogenic cultivation at both conditions. However, predominant VFA components were different according to reaction temperature conditions. In mesophilic condition, propionic acid which has low conversion efficiency to methane was accumulated up to 1,348 mg/L while acetic and butyric acid were predominant in thermophilic condition. Therefore, thermophilic acidogenic fermentation was superior for the effective VFAs production than mesophilic condition. From the DGGE analysis, the band patterns were different according to the initial pH conditions but the correlations of the each band were increased in similar pH conditions. These results mean that microbial communities were certainly affected by the initial pH condition. Consequently, the adjustment of the initial pH to neutral region and thermophilic operation are needed to enhance acidogenic fermentation of food waste recycling wastewater.

• Environmental Engineering Research
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• v.24 no.1
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• pp.107-116
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• 2019

Nitrogen removal, nitrous oxide ($N_2O$) emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes were investigated. Two sequencing batch reactors (SBRs) and two continuous-flow multiple anoxic and aerobic reactors (CMRs) were operated under high dissolved oxygen (DO) (SBR-H and CMR-H) and low DO (SBR-L and CMR-L) concentrations, respectively. Nitrogen removal was enhanced under CMR and low DO conditions (CMR-L). The highest total inorganic nitrogen removal efficiency of 91.5% was achieved. Higher nitrifying and denitrifying activities in SBRs were observed. CMRs possessed higher $N_2O$ emission factors during nitrification in the presence of organics, with the highest $N_2O$ emission factor of 60.7% in CMR-L. SBR and low DO conditions promoted $N_2O$ emission during denitrification. CMR systems had higher microbial diversity. Candidatus Accumulibacter, Nitrosomonadaceae and putative denitrifiers ($N_2O$ reducers and producers) were responsible for $N_2O$ emission.