• 생태와환경
• /
• 제50권2호
• /
• pp.187-194
• /
• 2017

본 연구는 경상북도에 위치한 하천과 호소에서 채집한 미세조류의 배양실험을 통해 영양염류 제거에 유용한 미세조류를 탐색하고, 실제 배출되는 폐수, 개인하수 및 가축분뇨 방류수에 미세조류를 접종하여 질소와 인 제거효율을 평가하고자 하였다. 조류를 채집하여 예비 배양조에서 배양한 미세조류 군집의 우점종은 Monoraphidium contortum, Scenedesmus acutus, Coelastrum microporum, Chlorella sp.로 나타났으며, 4000 Lux와 8000 Lux 조도에서 인공폐수를 배양액으로 배양한 미세조류 군집의 우점종은 Chlorella sp., Scenedesmus obliquus로 나타났다. 8000 Lux 조도에서 $NO_3-N$ 제거율은 63.0%~83.6%로 나타났고, 4000 Lux 조도에서 $NO_3-N$ 제거율은 27.2%~88.1%로 나타났다. 4000 Lux와 8000 Lux 조도에서 $PO_4-P$의 제거율은 95.3% 이상으로 $NO_3-N$의 제거율보다 높게 나타났다. $NO_3-N$와 $PO_4-P$의 제거 효율은 $1.0{\times}10^6cells\;mL^{-1}$ 농도로 접종하였을 때 $1.0{\times}10^5cells\;mL^{-1}$와 $1.0{\times}10^7cells\;mL^{-1}$ 농도로 접종하였을 때 보다 높게 나타났다. 미세조류를 이용한 인공폐수에서의 TN과 TP 제거율은 각각 94.9%과 90.0%로 나타났으며, TN과 TP 제거속도는 $1.961mg\;L^{-1}\;day^{-1}$, $0.200mg\;L^{-1}\;day^{-1}$로 나타났다. 실험에 사용된 모든 폐수에서 미세조류를 이용하여 영양염류가 제거되었고, 그중 개인하수 방류수가 영양염류 제거율이 가장 높게 나타났다.

• Environmental Engineering Research
• /
• 제22권1호
• /
• pp.12-18
• /
• 2017

Struvite precipitation has been proven to be an effective method in removing and recovering ammonia nitrogen (N) and phosphate phosphorus (P) from wastewater. In this study, effects of pH, molar ratios and pre-treatment of effluent of anaerobically digested swine wastewater were investigated to improve struvite crystallization. The magnesium : ammonium : phosphate ratio of 1.2 : 1.0 : 1.0 was found to be optimal, yet the molar ratio in the wastewater was 1 : 74.9 : 1.8. From the analysis, the optimum pH was between 8.0 and 9.0 for maximal phosphate P release and from 8.0 to 10.0 for maximal ammonia N and phosphate P removal from real wastewater. Analysis from Visual MINTEQ predicted the pH range of 7-11 for ammonia N and phosphate P removal and recovery as struvite. For pre-treatment, microwave pre-treatment was ineffective for phosphate P release but ultrasound pre-treatment showed up to 77.4% phosphate P release at 1,000 kJ/L of energy dose. Precipitates analysis showed that phosphorus and magnesium in the collected precipitate had almost same values as theoretical values, but the ammonia content was less than the theoretical value.

• 유기물자원화
• /
• 제18권1호
• /
• pp.89-97
• /
• 2010

본 연구에서는 오존을 이용하여 축산폐수를 전처리하고 일반하수와 연계하여 처리하였을 때 처리효율을 실험실 규모의 장치를 이용하여 비교 분석하였으며 결과는 다음과 같다. 축산폐수의 오존산화 결과 대상폐수의 pH를 산성(pH4), 중성(pH7), 알칼리성(pH10)으로 변화시켰을 때 각각 COD제거율은 시간당 17%, 78%, 62% 로 분석되었다. 오존산화에 의해 NBDCOD 중 일부가 미생물이 분해가능한 BDCOD 로 전환되어 SCODcr/TCODcr 비는 26%에서 약 38%로 증가하였다. 따라서, 오존산화에 의한 축산폐수의 전처리는 난분해성 물질을 생물학적 분해 가능한 물질로 일부 전환시키며 후단 생물학적 처리 단계에서의 제거효율을 높일 수 있는 영향을 미치는 것으로 분석되었다. 오존산화처리된 축산폐수와 하수와의 연계유입수를 MLE(Modified Ludzack-Ettinger) 공정으로 처리한 결과, 내부반송 100%일 때 TCODcr 93.8%, T-N 74.3%, T-P 89.7%, SS 97.5%의 처리효율을 나타냈다. 또한 내부반송율을 150%로 증가시켰을 때 처리효율은 각각 94.5%, 54.5%, 70.8%, 98.5% 로 나타났고, 200%로 증가시켰을 때 처리효율은 각각 92.6%, 83.1%, 81.9%, 98.5% 로 나타났다. 연계유입수를 원수로 사용한 경우 특히 질소제거율은 내부반송율 100%, 150%, 200%에서 각각 74.3%, 54.5%, 83.1%로 나타났으며, 모든 경우에 있어 일반하수를 원수로 사용한 경우보다 질소제거율이 우수한 것으로 분석되었다.

• 한국산학기술학회논문지
• /
• 제11권10호
• /
• pp.4055-4068
• /
• 2010

본 연구는 고도처리공법을 적용하여 수년간 가동 중인 하수처리시설에 대한 운전현황을 측정 분석하여, 고도처리공법 적용의 적정성을 평가하고자 하였다. 단위공정별 처리효율은, BOD의 경우 1차침전지 35, 생물반응조 87, 최종방류수 48 %, T-N의 경우 1차침전지 18, 생물반응조 40, 최종방류수 25 %, T-P의 경우 1차침전지 23,, 생물반응조 38, 최종방류수25 % 등으로, 각 단위공정별로 양호한 처리효율을 나타내었다. 생물반응조 내의 미생물 관측 결과, 다양한 종류의 세균과 원생동물 및 후생동물이 관측되었고, 담체의 세균 부착기능이 안정적으로 유지되고 있음을 알 수 있었다. 최종방류수질은 BOD 5.5, COD 9.9, SS 4.6, T-N 11.8, T-P 0.99 mg/L으로 방류수 수질기준보다 낮은 양호한 수질상태를 나타내었다.

• Restorative Dentistry and Endodontics
• /
• 제47권1호
• /
• pp.13.1-13.13
• /
• 2022

Objectives: This study evaluated the efficacy of 3 reciprocating systems and the effects of 2 instruments for irrigant activation on filling material removal. Materials and Methods: Forty mesiobuccal roots of maxillary molars were prepared up to size 25.06 and obturated. Micro-computed tomography (micro-CT) examination #1 was performed. Teeth were then divided into 4 groups (n = 10), according to the retreatment protocol: (1) manual, (2) Reciproc Blue, (3) WaveOne Gold, and (4) X1 Blue. Micro-CT examinations #2 and #3 were performed after filling removal and repreparation, respectively. Next, all teeth were divided into 2 new groups (n = 20) according to the irrigant activation protocol: XP Clean (XP Clean size 25.02) and Flatsonic (Flatsonic ultrasonic tip). Micro-CT examination #4 was performed after irrigant activation. Statistical analysis was performed with a significance level set at 5%. Results: WaveOne Gold removed a significantly greater amount of filling material than the manual group (p < 0.05). The time to reach the WL was similar for all reciprocating systems (p > 0.05). X1 Blue was faster than the manual group (p < 0.05). Only manual group improved the filling material removal after the repreparation stage (p < 0.05). Both activation protocols significantly improved the filling material removal (p < 0.05), without differences between them (p > 0.05). Conclusions: None of the tested instruments completely removed the filling material. X1 Blue size 25.06 reached the working length in the shortest time. XP Clean and Flatsonic improved the filling material removal.

• 한국물환경학회지
• /
• 제22권4호
• /
• pp.678-686
• /
• 2006

The feasibility of the high-hydrophilic biofilter was examined for application in rural wastewater treatment in Korea. The intermittent trickling biofiter was developed for wastewater treatment of media and examined instantaneous wetting water and immersional wetting water. Melamin foam absorbed 120 times it's weight in water and maintained wetting status than other materials. These characteristics are improvement for application in rural areas showing large variance of amount of influent. The biofilter process was effective in treating organic pollutants; mean removal efficiencies of $BOD_5$ and TSS were above 80%. The average SS concentrations of effluent was showed below $10mg/L^{-1}$ and meet guidelines in special regions, however, the average concentration of $BOD_5$ was about $20mg/L^{-1}$. The removals of T-N and T-P were relatively less effective and removal efficiencies were below 40%. It might meet the guidelines for T-P because of low levels of influent T-P concentration. However, the T-N concentration were too high and further treatment is required. The effluent concentration of $NH_4-N$ showed a significant reduction rate about 43.8%, but part of $NH_4-N$ was transformed to $NO_2-N$ and $NO_3-N$ inside the biofilter through nitrification process. The effluent concentration of org-P was removed about 78.8% of influent concentration by filtration. Considering stable performance and effective removal of pollutant in wastewater, low maintenance, and cost-effectiveness, the hydrophilic biofilter system was thought to be an effective and feasible alternative for decentralized rural areas.

• 상하수도학회지
• /
• 제21권5호
• /
• pp.589-599
• /
• 2007

This study was conducted to investigated the removal efficiency of BOD and nutrient for the treatment of low strength municipal wastewater by a biological nutrient removal system. In this experiment, the effect of operating parameter including HRT of 7.0hr, BOD/TN ratios of 2.62~4.08, internal recycle of 50~300%, and return sludge of 50~100%, were studied during winter season. Efficiencies of organic matter and T-P removal and denitrification were not significantly affected by the change of temperature in winter season. However, the specific nitrification rate and nitrification efficiency decreased at low temperature. Besides, denitrification efficiencies increased with increasing BOD/TN ratios. It was also found that the internal recycle and return sludge ratio below 50% is required for the effective denitrification of low strength municipal wastewater. With operating mode 4 of the optimum, the effluent BOD, T-N and T-P concentration were obtained to average 5.8, 14.6, and 0.84 mg/L, respectively. The temperature-activity coefficient (${\theta}$) of specific nitrification rate, specific denitrification rate and specific phosphorus uptake rate were obtained 1.044, 1.017, 1.028, respectively.

• The Journal of Advanced Prosthodontics
• /
• 제11권6호
• /
• pp.305-312
• /
• 2019

PURPOSE. The purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading. MATERIALS AND METHODS. The study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (10⁶ cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces. RESULTS. There was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant. CONCLUSION. The use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

• 한국산학기술학회논문지
• /
• 제14권2호
• /
• pp.970-976
• /
• 2013

본 연구는 간헐포기 공정을 이용하여 생활하수의 고도처리 효율을 증진시키는 방안을 제시하고자 수행되었다. 운전기간동안 유기물 제거효율 검토 결과, HRT 9hr 이상에서 TCODcr와 TBOD의 제거효율은 각각 91.1~96.3%와 91.4~97.5%로 높은 제거효율을 나타냈으나, HRT가 6hr에서는 각각 86.9~90.5%, 88.0~90.9%로 제거효율이 감소된 것으로 조사되었다. $NH_3$-N은 HRT 9hr 이상에서는 95% 이상의 높은 제거효율을 나타냈으며, T-N 제거효율은 HRT 9~12hr에서 67.6~76.7%, HRT 6hr에서는 50%로 감소되었는데 이는 탈질에 필요한 탄소원이 부족하기 때문이다. 운전기간동안 T-P 제거효율은 평균 32%로 낮게 조사되었는데 강화되는 법적기준을 준수하기 위해서는 반응조 후단에 화학적 인 제거 공정이 필요한 것으로 사료된다.

• 한국농공학회지
• /
• 제42권4호
• /
• pp.96-105
• /
• 2000

Field experiment was performed from August 1996 to December 1999 to examine the performance of constructed wetland system for wastewater treatment in rural area. The constructed wetland system was installed in Konkuk University and the effluent from septic tank of school building was used as an influent to the treatment basin. The treatment basin was composed of sand bed with planted reed. From August 1996 to June 1998 the hydraulic loading rate was fixed with about 15.63cm/day and theoretical detention time was 1.38 days, and from July 1998 to December 1999 the hydraulic loading rate was about 6.25cm/day and theoretical detention time was 3.5days. It worked continuously even during winter time, and the sewage flowed without freezing even when average daily air temperature was below -1$0^{\circ}C$. Average removal rate of BOD , COD, and SS was about 70%, T-P removal rate was about 50.8% , and T-N removal rate was 23.9%. The reason for poor T-N removal might be due to high influent concentration and short retention times. At the later years BOD and COD removal rates were increased , and SS and T-P removal rates did not change significantly , but T-N removal rates were decreased. The effluent of the wetland system often effluent water quality standards for sewage treatment plant, therefore, further treatment would be required if the effluent need to be discharged to the public water. Wetland system involves relatively large land area and could be suitable for rural area. Therefore, utilization of reclaimed sewage for agricultural purpose or subsequent land treatment is recommended as a ultimate disposal of sewage for agricultural purpose or subsequent land treatment is recommended as a ultimate disposal of sewage in rural area.