• Resources Recycling
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• v.13 no.1
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• pp.28-38
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• 2004

The characteristics of cyanide decomposition in aqueous phase by electric oxidization have been explored in an effort to develop a process to recycle waste water. Considering current efficiency and voltage, the free cyanide decomposition experiment by electric oxidization indicated that 5 V of voltage and copper catalytic Cu/CN mole ratio 0.05 was the most appropriate condition, where current efficiency was 26%, and decomposition speed was 5.6 mM/min. High voltage and excess copper addition increased decomposition speed a little bit but not current efficiency. The experiment of free cyanide density change proves that high density cyanide is preferred because speed and current efficiency increase with density. Also, the overall decomposition reaction could be represented by the first order with respcect to cyanide with the rate constant of $1.6∼7.3${\times}$10^{-3}$ $min^{-1}$ The mass transfer coefficient of electric oxidization of cyanide came out as $2.42${\times}$10^{-5}$ $min^{-1}$ Furthermore, the Damkohler number was calculated as 5.7 in case of 7 V and it was found that the mass transfer stage was the rate determining step.

• Korean Journal of Environmental Agriculture
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• v.23 no.1
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• pp.1-6
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• 2004

The seeding sources and concentration of ammonia on anaerobic digestion were investigated by batch culture bioreactors. The sources of seeding on anaerobic digestion were from swine wastewater collection pit of a hog raising farm and from anaerobic digestion sludge of a municipal sewage treatment plant. The inhibition of ammonia on anaerobic microorganisms was initiated at ammonia concentration of $1,500\;mgNH_4-N/L$ and it's effect was increased by increased by increasing ammonia concentration up to $3,500\;mgNH_4-N/L$ regardless the sources of seeding as evidenced by decreases in COD removal efficiencies and biogas yields. The inhibition occurred to not only methanogens but also acidogens since the concentration of volatile fatty acids was maintained at 50 mg/L The COD removal efficiency and biogas yield were Maintained constantly while increasing ammonia concentration up to $3,500\;mgNH_4-N/L$ when swine wastewater collection pit was used as a seeding; however, those were decreased while increasing ammonia concentration when anaerobic digestion sludge was used as a seeding. The results indicate that the seeding acclimated to high concentrations of ammonia for long time was easy in adaptation to high ammonia concentration and less subjective to ammonia inhibitory effects.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.261-269
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• 2015

In this study, we applied a membrane distillation process to investigate a feasibility of treating a wastewater with high concentration of organic matters including nitrogen and phosphorus. The laboratory scale experiment was performed by using a hydrophobic PVDF membrane with the pore size of $0.22{\mu}m$ and porosity of 75%. The installation was direct contact type where the temperature difference between a feed and permeate side was controlled to have a range from 20 to $60^{\circ}C$. We observed a flux variation and a concentration changes of COD, $PO{_4}^{3-}$-P, $NH_4{^+}$-N and conductivity of feed side as well as permeate side with various temperature differences (20 to $60^{\circ}C$), cross flow velocities (0.09 to 0.27 m/s) through the module, and pH (6.6 to 12.0) of the feed that has the initial concentration of COD about 1,000 mg/L, total nitrogen 390 mg/L, total phosphorus 10 mg/L, conductivity of $7,000{\mu}s/cm$. The results showed that the average flux was ranged from 4 to $40L/m^2/hr$ which was almost similar with the flux of NaCl and deionized water used as a feed solution. The lowest flux was obtained at the operating condition with the temperature difference of $20^{\circ}C$ and cross flow velocity of 0.09 m/s while the highest one was measured with $60^{\circ}C$ and 0.27 m/s. Above 99% of COD and $PO{_4}^{3-}$-P in the feed could be rejected regardless of an operating condition. However, the removal rate of ammonium nitrogen was varied from 64 to 99% depending on the pH of feed solution.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.599-607
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• 2000

In this research, ${NH_4}^+-N$ and ${PO_4}^{3-}-P$ in wastewater were removed by crystallization. Nitrogen and phosphate have been regarded as key nutrients in the eutrophication of rivers and lakes. Struvite, $MgNH_4PO_4{\cdot}6H_2O$, is insoluble in alkaline solutions. Fertilizer industry wastewater contains organic and nitrogen concentration of 330 mg/L and 550 mg/L, respectively. Nitrogen in this wastewater cannot be treated by conventional biological treatment without physicochemical pretreatment, because nitrogen concentration is relatively high compared to organic concentration. Magnesium ions used in this study were from bittern and commercial magnesium salts of $MgCl_2$ and $Mg(OH)_2$. Bittern obtained as a by-product of seasalt manufacture contains $8,000mg\;Ca^{2+}/L$ and $32,000mg\;Mg^{2+}/L$. Optimum initial pH was 10.5~11.0 and the reaction was complete or done in 2 min. Nitrogen removal efficiency using bittern, $MgCl_2 $ and $Mg(OH)_2$ (as source of $Mg^{2+}$) was 71 %, 81% and 83%. respectively. Phosphate removal efficiency was 99%, 98% and 93%, respectively. Therefore, bittern, $MgCl_2$ and $Mg(OH)_2$ can be efficiently used as $Mg^{2+}$ source for crystallization of nitrogen and phosphate. However, bittern is economically favorable $Mg^{2+}$ source for removing nitrogen and phosphate in wastewater.

• Clean Technology
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• v.18 no.4
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• pp.398-403
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• 2012

Selective nitrification and granulation have been carried out in a pilot scale air-lift sequencing batch reactor (SBR) for stable and economical nitrogen removal from wastewater. The SBR showed about 100% nitrification efficiency up to 1.0 kg ${NH_4}^+-N/m^3{\cdot}d$, about 90% efficiency at 1.0-2.0 kg ${NH_4}^+-N/m^3{\cdot}d$, and it was less than 90% when the load was higher than 2.0 kg ${NH_4}^+-N/m^3{\cdot}d$. Nitrite accumulation was induced by selective inhibition of nitrite oxidizing bacteria by free ammonia inhibition and dissolved oxygen limitation. For the purpose, high nitrite ratio (> 0.95) was obtained by keeping the pH higher than 8.0 and dissolved oxygen lower than 1.5 mg/L. In addition, sludge granulation was achieved by keeping reactor settling time to 5 minutes to wash out poor settling sludge and to promote the growth of granulation sludge. The operation accelerated sludge granulation and the sludge volume index (SVI) decreased and stably maintained to less than 75 in 60 days.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.2
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• pp.57-65
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• 2008

Wastewater containing strong organic matter is very difficult to treat by utilizing general sewage treatment plant. but the wastewater is adequate to generate biomass energy (bio-gas; methane gas) by utilizing anaerobic digestion. EcoDays Plug Flow Reactor (E-PFR), which was already proved as an excellent aerobic wastewater treatment reactor, was adapted for anaerobic food wastewater digestion. This research was performed to improve the efficiency of bio-gas production and to optimize anaerobic wastewater treatment system. Food wastewater from N food waste treatment plant was applied for the pilot scale experiments. The results indicated that the efficiency of anaerobic wastewater treatment and the volume of bio-gas were increased by applying E-PFR to anaerobic digestion. The structural characteristics of E-PFR can cause the high efficiency of anaerobic treatment processes. The unique structure of E-PFR is a diaphragm dividing vertical hydraulic multi-stages and the inversely protruded fluid transfer tubes on each diaphragm. The unique structure of E-PFR can make gas hold-up space at the top part of each stage in the reactor. Also, E-PFR can contain relatively high MLSS concentration in lower stage by vertical up-flow of wastewater. This hydraulic flow can cause high buffering capacity against shock load from the wastewater in the reactor, resulting in stable pH (7.0~8.0), relatively higher wastewater treatment efficiency, and larger volume of bio-gas generation. In addition, relatively longer solid retention time (SRT) in the reactor can increase organic matter degradation and bio-gas production efficiency. These characteristics in the reactor can be regarded as "ideal" anaerobic wastewater treatment conditions. Anaerobic wastewater treatment plant design factor can be assessed for having 70 % of methane gas content, and better bio-gas yielding and stable treatment efficiency based on the results of this research. For example, inner circulation with generated bio-gas in the reactor and better mixing conditions by improving fluid transfer tube structure can be used for achieving better bio-gas yielding efficiency. This research results can be used for acquiring better improved regenerated energy system.

• Clean Technology
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• v.3 no.2
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• pp.87-93
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• 1997

A new process has been developed for nitrate and other salts removals from polluted waters. Alumina cement and calcium oxide served as precipitating agents to remove nitrate with stirring at basic pH. Low content of alumina in the commercialized alumina cements resulted in a increasing in nitrate removal yield. It is found that the compositions of aluminium and calcium are the most important factors in successful nitrate insolubilization. In order to remove high concentration of nitrate in polluted water, multi-stage precipitation was found to be very effective. Sulfate, chloride, and phosphate ions as well as nitrate were also removed by the precipitated reaction. After precipitation, post-treatments including Na2CO3 addition and neutralization with acid alleviated the level of aluminium and calcium in the treated water.

• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.631-641
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• 2009

Transport of nitrous oxide and treated waste water was investigated in an estuary receiving treated waste water. Seasonal change of water quality were also observed to assure origins of $N_2O$ and to estimate the influence of treated waste water on $N_2O$ production in the survey area. Based on nitrous oxide concentration profiles in the survey area, discharged treated waste water were traced, which flowed upstream at the flood tide and downstream at the ebb tide with concentration maxima. It is assumed that nitrous oxide discharged from treated waste water is transported to the survey area with partial and vertical mixture. To determine the production of $N_2O$ in survey area, flux at each sampling sites were calculated and 25% of the produced $N_2O$ was originated from treated waste water in result. The remaining percentage of the production was also assumed to be the discharge from the sediment layers.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.568-571
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• 2001

Food wastewater eluted from the three-stage methane fermentation system developed in this lab showed high concentrations of TCOD, BOD, T-N and T-P. Because the effluent of biological filter chamber (BFC) still had high concentration of nitrogen and organic material, the effluent was treated with algal periphyton system using algae. The removal rates of COD, T-N and T-P wer 96, 98 and 91%, respectively, in this system. The grown algae could digested byy waterfleas using the ecological food chain system. Food wastewater is better than algal culture medium for growth of waterflea, Moima Macrocopa. During 12days, the individual of waterflea increased to 180 in the food wastewater containing a T-N concentration of 150 mg/ ${\ell}$.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.141-141
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• 2001

사이즈 프레스용 전분은 주로 산화전분이 이용되고 있으며, 전분업체에서 공급되는 것과 제지공장에서 자가변성으로 제조하여 이용하는 것으로 나눌 수 있다. 자가변성의 경우 경제적 측면에서 원가절감이 가능한 장점이 있는 반면 전분 품질이 다소 미흡한 단점이 있다. 자가변성 산화제로는 APSCAmmonium persulfate), 효소 등이 이용된다. 효소는 APS에 비해 전분 분자 내의 1,4결합만을 가수분해 시키고 점도안정성과 전분 용액 색상이 양호한 특성을 보인다. 또한 온도/농도/점도 등의 상관성을 자유롭게 이용하여 요구하는 전분 용액 품질을 얻을 수 있다. 제지용 전분 산화용으로는 주로 알파 -아밀라아제가 이용된다.본 실험은 산화전분을 효소변성을 이용한 생전분으로 가능성을 알아보고자 진행되었다. 일차적으로 실험실에서 하였고, 몇 차례의 mill trial을 통해 효소변성 전분 적용을 최적화하고자 하였다. 실험실적으로 효소변성을 위한 반응조건으로 온도, 시간, pH, 투입량 등을 설정하였 고, 각 조건별로 제조된 전분 용액의 점도를 측정하여 효소 반응성을 평가하였다. 실험 결과 전분 용액의 점도는 낮았고, 점도 안정성 또한 양호한 수준을 보였다. Cooking농 도는 20%로 하였으나 보다 고농도 cooking의 가능성을 확인할 수 있었다. 시트 물성도 전반적으로 산화전분 대비 대등한 수준을 나타내었다. Mill trial은 무림제지에서 실시하였고 사이즈 프레스 조제식을 이용하였다. 전분 농도는 초기에 20%로 시작하여 30%까지 올려서 trial을 실시하 였고, 그 외 작업조건들은 산화전분 적용 시와 동일하게 하였다. 효소 반응시간으로 인해 cooking시간이 다소 많이 걸렸으나 전반적인 조제 작업은 큰 문제 없이 이루어졌고, 효소변성 전분 용액의 점도는 낮은 수준으로 유지되었다. 사이즈 프레스 작업성이나 시 트 물성도 산화전분 적용 시와 대등한 수준을 보였으나, 전분 차이로 인한 색상 차이로 부가적인 염료 조정이 이루어졌다. 한편 폐수부하 증가를 우려하였으나, 이에 따른 문제는 크게 발생되지 않았다.