• Environmental Engineering Research
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• 제13권3호
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• pp.155-161
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• 2008

This study examined effects of the fermented leachate of food waste (FLFW) on nitrogen and phosphorous removal for domestic wastewater containing a low carbon-to-nitrogen (C/N) ratio in sequencing batch reactor (SBR). When the FLFW was not supplied in the process, release of phosphorus and excessive intake was not observed at both anaerobic and aerobic stages. On the other hand, when the FLFW was gradually added, active release of phosphorus and intake of phosphorus was noticed at an anaerobic stage and aerobic stage, respectively, resulting in improved phosphorus removal efficiency. The removal efficiency of nitrogen and phosphorus was increased from 75% and 37% (R-1, control test) to 97% and 80% (R-4, the highest substrate ratio test), respectively. In addition, although activity of the nitrogen oxidizing microorganisms was reduced when the reaction temperature was decreased to $10^{\circ}C$, the phosphorus removal efficiency was shown to increase with the addition of FLFW, indicating an independence from temperature. Overall, this study suggests that an efficient nutrients removal process can be successfully employed into a SBR when the FLFW is added to a wastewater which has a low C/N ratio.

• 한국농공학회논문집
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• 제53권6호
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• pp.85-91
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• 2011

Three different types of wetlands (unplanted wetland, reed planted wetland, cattail planted wetland) were constructed at the mouth of Seokmoon reservoir with 910 $m^2$ each to examine the effects of wetland plant on pollutant removal rate in constructed wetland, and operated for 9 years (2002~2010). Water depth of the wetland was maintained at 0.3~0.5 m, flow rate was about 40~200 $m^3$/day, and retention time was managed at about 1~5 days. There was no difference in removal rate of SS, TN, and TP between reed wetland and cattail wetland. Removal rate of SS and TN in planted wetland with reed and cattail were higher than unplanted wetland, whereas removal rate of TP in unplanted wetland was higher then planted wetland. The monthly variation of removal rate in planted wetlands was high compared with unplanted wetland. From the long term monitoring results, SS and TN removal rates of period3 (2008~2010) were higher than period1 (2002~2004) in planted wetland, whereas TP removal rate was decreased as time goes on. Overall, pollutant removal rate in constructed wetland was more influenced by existence of plants than by plant species. Although constructed wetland is operated long term period, SS, TN, and TP removal rate (SS 90 %, TN 60 %, TP 40 %) can be maintained high values.

• 대한치과교정학회지
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• 제52권3호
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• pp.201-209
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• 2022

Objective: To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors. Methods: The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque. Results: The mean period of total in-bone stay of microimplants in the post-retention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4-5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively. Conclusions: The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

• 한국환경과학회지
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• 제25권11호
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• pp.1493-1498
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• 2016

The efficiencies of Gang-Byeon sewage treatment facilities, which are based on GPS-X modelling, were analysed and used to design recycle water treatment processes. The effluent of an aeration tank contained total kjeldahl nitrogen (TKN) of 1.8 mg/L with both C-1 and C-2 conditions, confirming that most ammonia nitrogen ($NH_3{^+}-N$) was converted to nitrate nitrogen ($NO_3{^-}-N$). The concentrations of $NH_3{^+}-N$ and $NO_3{^-}-N$ were found to be 222.5 and 227.2 mg/L, respectively, with C-1 conditions and 212.2 and 80.4 mg/L with C-2 conditions. Although C-2 conditions with higher organic matter yielded a slightly higher nitrogen removal efficiency, sufficient denitrification was not observed to meet the discharge standards. For the total nitrogen (T-N) removal efficiency, the final effluent concentrations of T-N were 293.8 mg/L with biochemical oxygen demand (BOD) of 2,500 mg/L, being about 1.5 times lower than that (445.3 mg/L) with BOD of 2,000 mg/L. Therefore, an external carbon source to increase the C/N ratio was required to get sufficient denitrification. During the winter period with temperature less than $10^{\circ}C$, the denitrification efficiency was dropped rapidly even with a high TKN concentration (1,500 mg/L). This indicates that unit reactors (anoxic/aerobic tanks) for winter need to be installed to increase the hydraulic retention time. Thus, to enhance nitrification and denitrification efficiencies, flexible operations with seasons are recommended for nitrification/anoxic/denitrification tanks.

• 한국환경농학회지
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• 제19권2호
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• pp.134-141
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• 2000

전기화학적 방법을 이용한 농공단지폐수의 효율적인 처리기술개발을 위한 기초실험으로서 전압, 전극판 간격, pH 및 전해용액 주입농도 등에 따른 오염물질 처리효율을 조사한 결과는 다음과 같다. 전압별 전기화학반응조내 온도 및 pH는 전압이 높을수록 상승하였으나, EC는 전압별로 별 변화가 없었다. COD, 탁도, T-N 및 T-P의 처리율은 전압이 높을수록 증가하였으며 전압 20V일 경우 COD는 20분, 탁도는 30분, T-N 및 T-P는 2분일 때 각각 그 처리율이 약 65, 90, 68 및 84%로 가장 높았다. 전극판 간격별 COD 처리율은 전극간격이 좁아질수록 그리고 전기반응시간이 경과할수록 전반적으로 증가하는 경향이었으며, 탁도 처리율은 전극판 간격 모두 전기반응초기에 약 80%이상 처리되었고, T-N 처리율은 전극판 간격이 좁을수록 높았다. T-P 처리율은 전기반응시간 2분 후에 전극판 간격 모두에서 약 79% 이상 처리되었다. 초기 pH에 따른 COD 처리율은 전반적으로 pH 7에서 높았으며, 탁도 처리율은 전기반응시간 2분 이후의 모든 조건에서 약 80%이상 처리되었다. 그리고 T-N 처리율은 초기 pH가 높아질수록 증가하였고, T-P 처리율은 전기반응시간 2분 이후 초기 $pH\;5{\sim}9$에서 약 $79{\sim}96%$로서 가장 높았다. NaCl 농도별 오염물질 처리율은 전반적으로 NaCl을 주입한 경우가 NaCl를 주입하지 않은 경우에 비해 매우 높았으며, COD 및 T-P의 처리율은 $NaCl\;500mg/l$, 탁도 처리율은 $NaCl\;1,000mg/l$, T-N의 처리율은 NaCl 250 및 $500mg/l$에서 전반적으로 다른 조건에 비하여 높았다.

• 상하수도학회지
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• 제22권5호
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• pp.581-587
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• 2008

In this study, we investigated the buffering effect with different COD, $NH_4{^+}-N$ and TP shock loads on the performance of lab-scale Sequencing Batch Reactor(SBR) using synthetic wastewater. This study was operated under the following conditions : HRT, 12 hrs : MLSS, 2,000 mg/L : F/M ratio, $0.2kgCOD/kgMLSS{\cdot}d$ : SRT, 20days, and was increased by a factor, COD : ranging from 200-2000 mg/L, $NH_4{^+}-N$ : ranging from 30-300 mg/L, T-P : ranging from 5-50 mg/L in the reactor. As results, COD removal rate at different shock loads was decreased until 42.1%(stable state : 95%) and concentration with effluent was higher than 695 mg/L(at Run 6). In case of $NH_4{^+}-N$ removal rate was decreased until 35.8% from 97.0% and also T-P removal rate was decreased until 5.0%. Effluent concentrations of COD, $NH_4{^+}-N$ and T-P were rapidly increased according to shock loads and needed 3, 4 and 6 additional cycle times for recovering the stable condition.

• 상하수도학회지
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• 제20권1호
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• pp.115-121
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• 2006

The purpose of this study was to investigate applicability of pretreatment on the existing biological treatment for domestic wastewater reclamation. From Jar Tests, it was found that optimum dosage of coagulant was PAC 0.5mg/L and $FeCl_3$ 180mg/L for urban sewage. In this study, PAC 0.5mg/L was selected considering sludge production and the amount of coagulant required. In a continuous experiment performed with combining chemical coagulation and biological treatment, a considerable removal efficency was obtained in term of BOD, SS, T-N, T-P and ABS. When the raw sewage was supplied into the pre-chamical treatment facility, the removal of BOD and SS was 48.3% and 81.1%. However T-N removal was very low which means T-N consists of $NH_3-N$ mostly. T-P was almost completely recluced by the chemical addition. The effluent BOD & SS was 57~76 and 21~43mg/L, which could reduce the size of biological treatment facility. From the cost estimation pre-chemical treatment could save around half of the area required for biological treatment with post ceagulation.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.398-401
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• 2003

Bacillus species predominantly outgrown in a night soil treatment system were isolated and characterized. Cell interactions took place among them and cell population changed under various culture conditions. Maximum removal of $NH_4\;^+-N$ and cell production occurred under the conditions of 30% DO and C/N ratio of 8. Additions of 0.8% peptone and 0.3% yeast extract to a basal medium influenced the growth of isolates and the removal of $NH_4\;^+-N$ in flask culture, and metal ions such as Ca, Fe and Mg also did. During the flask experiment of nitrogen removal under an aerobic condition, active nitrification by the isolates occurred largely in 1 h with the decrease of COD and alkalinity destructed was only 74.6% of theoretical value. From the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 29.0%. This conversion of ammonia to $N_2$ under an aerobic condition was confirmed by GC analysis. The B3 process using the Bacillus species seemed to have some economic advantage.

• 멤브레인
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• 제12권2호
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• pp.67-74
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• 2002

침지형생물막 반응조와 역삼투막을 이용하여 염색폐수를 공업용수로 재이용하기 위한 실험을 수행하였다. 실험실과 현장의 pilot plant 실험 결과 20-25 cmHg의 흡인압력으로 10 LMH($1/m^2$.hr)의 투과유속을 얻었다. 침지형생물막 반응조에서 CODcr, $COD_{Mn}$ 및 T-N의 제거율은 각각 93%, 90%, 60%로 나타났다. 난분해성 물질과 총질소의 제거효율을 높여서 염색폐수를 공업용수로 재이용하기 위한 침지형생물막 반응조와 역삼투막(SMBR+R/0)을 조합한 공정을 수행한 결과, 질소제거율이 80% 이상으로 총질소 농도를 15 mg/L를 얻었다. 조합공정은 염색폐수를 공업용수로 재이용하기에 적합하였다.

• 한국물환경학회지
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• 제22권1호
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• pp.7-16
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• 2006

The present study evaluated effect of temperature on removals of organic matter (C), nitrogen (N) and phosphorus (P) in Modified-Dephanox (M-Dephanox) process, which is hybrid system, comparing with those of Modified-Ludzack Ettinger (MLE) under the suspended-growth bacteria, as control. M-Dephanox process was more stable than MLE process in the removal of C, N, P, especially in nitrification, as the temperature was decreased from $25^{\circ}C$ to $16^{\circ}C$. As the temperature was decreased from $25^{\circ}C$ to $16^{\circ}C$, the removal efficiency of $NH_4{^+}-N$ of M-Dephanox process was decreased by 3.8%, but that of MLE process decreased by 25.7%. T-N removal efficiency of M-Dephanox was higher than MLE process by 27.1% and 26.9% at $25^{\circ}C$ and $16^{\circ}C$ of temperature, respectively.