• Environmental Engineering Research
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• 제24권3호
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• pp.501-512
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• 2019

The seasonal effects on the biostability of drinking water were investigated by comparing the seasonal variation of assimilable organic carbon (AOC) in full-scale water treatment process and adsorption of AOC by three filling materials in lab-scale column test. In full-scale, pre-chlorination and ozonation significantly increase $AOC_{P17\;(Pseudomonas\;fluorescens\;P17)}$ and $AOC_{NOX\;(Aquaspirillum\;sp.\;NOX)}$, respectively. AOC formation by oxidation could increase with temperature, but the increased AOC could affect the biostability of the following processes more significantly in winter than in warm seasons due to the low biodegradation in the pipes and the processes at low temperature. $AOC_{P17}$ was mainly removed by coagulation-sedimentation process, especially in cold season. Rapid filtration could effectively remove AOC only during warm seasons by primarily biodegradation, but biological activated carbon filtration could remove AOC in all seasons by biodegradation during warm season and by adsorption and bio-regeneration during cold season. The adsorption by granular activated carbon and anthracite showed inverse relationship with water temperature. The advanced treatment can contribute to enhance the biostability in the distribution system by reducing AOC formation potential and helping to maintain stable residual chlorine after post-chlorination.

• 한국환경과학회지
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• 제19권3호
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• pp.261-267
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• 2010

The variation of assimilable organic carbon(AOC) concentration at each condition of ozonation was investigated using a model water and drinking water resource. AOC concentration of model raw water and drinking water resource tended to increase at low ozone dose. The maximum AOC concentration was detected when the residual ozone begin to be measured. Also, the AOC concentration increase at pH 8 compared to both pH 6 and 7 while that for pH 9 decreased rapidly. The removal characteristics of trihalomethane formation potential(THMFP) by ozonation was also investigated. Unlike the trend of AOC, the THMFP concentration never increased by ozonation but decreased even at low ozone dosage. From these results, the ozone dosage would be effective to simultaneously decrease both AOC and THMFP.

• Asian-Australasian Journal of Animal Sciences
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• 제27권9호
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• pp.1285-1292
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• 2014

An in vitro experiment was conducted to evaluate the effects of Aspergillus oryzae culture (AOC) and 2-hydroxy-4-(methylthio)-butanoic acid (HMB) on rumen fermentation and microbial populations between different roughage sources. Two roughage sources (Chinese wild rye [CWR] vs corn silage [CS]) were assigned in a $2{\times}3$ factorial arrangement with HMB (0 or 15 mg) and AOC (0, 3, or 6 mg). Gas production (GP), microbial protein (MCP) and total volatile fatty acid (VFA) were increased in response to addition of HMB and AOC (p<0.01) for the two roughages. The HMB and AOC showed inconsistent effects on ammonia-N with different substrates. For CWR, neither HMB nor AOC had significant effect on molar proportion of individual VFA. For CS, acetate was increased (p = 0.02) and butyrate was decreased (p<0.01) by adding HMB and AOC. Increase of propionate was only occurred with AOC (p<0.01). Populations of protozoa ($p{\leq}0.03$) and fungi ($p{\leq}0.02$) of CWR were differently influenced by HMB and AOC. Percentages of F. succinogenes, R. albus, and R. flavefaciens (p<0.01) increased when AOC was added to CWR. For CS, HMB decreased the protozoa population (p = 0.01) and increased the populations of F. succinogenes and R. albus ($p{\leq}0.03$). Populations of fungi, F. succinogenes (p = 0.02) and R. flavefacien (p = 0.03) were increased by adding AOC. The HMB${\times}$AOC interactions were noted in MCP, fungi and R. flavefacien for CWR and GP, ammonia-N, MCP, total VFA, propionate, acetate/propionate (A/P) and R. albus for CS. It is inferred that addition of HMB and AOC could influence rumen fermentation of forages by increasing the number of rumen microbes.

• Environmental Engineering Research
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• 제15권1호
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• pp.9-14
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• 2010

The objective of this study was to assess the variation in the concentration of assimilable organic carbon (AOC) in a drinking water resource, and investigate the characteristics of AOC derived from algae. The seasonal change in AOC at the Kamafusa dam corresponded to changes in the algal cell number. In order to understand the relationship between AOC and algae in a water resource and water purification plant, two kinds of laboratory experiment were performed. The algal culture experiment showed that extracellular organic matter (EOM) that was released during the growth of Phormidium tenue with M-11 medium led to significant increases in the AOC concentration, but no significant variation in the AOC concentration was observed with CT medium containing a high dissolved organic carbon concentration. The chlorination experiment showed that the AOC included in EOM was not easily removed by chlorination, although the AOC included in intercellular organic matter released from the algal cells by chlorination was removed under conditions where residual chlorine was detected.

• 한국환경보건학회지
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• 제32권6호
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• pp.539-542
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• 2006

The objective of this paper is to compare the applicability of assimilable organic carbon (AOC) or biodegradable dissolved organic carbon (BDOC) for quantifying biodegradable organic material (BOM) and bio-stability in distribution systems for a variety of finished waters. The study the data is derived from was part of an AWWARF and Tampa Bay Water tailored collaboration project to determine the effect of blending different waters on distribution system water quality. Seven different finished waters were produced from surface, ground, or brackish water on site and fed 18 independent pilot distribution systems (PDSs), either as single finished water or as a blend of several finished waters. AOC and BDOC have often been used as indicators of bacterial regrowth potential in distribution systems. In this study, AOC was the more useful assay of the two for the BOM concentrations observed in the PDSs. BDOC did not distinguish BOM while AOC did at the low BOM levels from many of the advanced treatments (e.g. RO, $O^3/BAC$). AOC in contrast allowed much more meaningful calculations of the consumption or production of AOC as the blends passed through the PDSs even for very low BOM blends. In addition, meaningful trends corresponding to changes in heterophic plate count (HPC) were observed for AOC but not for BDOC. Moreover, AOC stability was associated with waters produced from advanced membrane treatment.

• 대한환경공학회지
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• 제27권2호
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• pp.158-162
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• 2005

이 연구에서는 대규모 나노여과 정수처리 시스템의 각 단계의 생물학적 안정성과 공정내의 AOC를 측정하고자 한다. 나노 여과 정수처리 시스템은 미 플로리다 주 남부의 Plantation 시의 $45,400\;m^3$/day (12 mgd) 규모의 연수화 시설에서 연구하였으며, 표면 대수층의 유기물이 많은 지하수를 원수로 이용하였다. 유입원수의 평균 AOC 농도는 158 g/L acetate-C이다. 전처리(산과 스케일 방지제첨가) 후 AOC농도는 12.7% 가량 증가하였는데, 이는 전처리 과정에서 투입된 화학물들이 생물학적 안정성을 저감시킬 수 있음을 의미한다. 전체적으로 나노여과공정은 63.4%와 94.8% 의 AOC 및 DOC 제거효율을 보였다. 특히 1단계에서의 AOC 제거율 (68%)이 2단계에서의 제거율 (58%)보다 다소 높았는데 이는 높은 회수율과 산 전처리과정이 있는 대규모 나노 공정 2단계에서 흔히 형성되는 낮은 pH 높은 이온강도 및 경도 등의 화학적 환경에 기인한다고 사료된다.

• 한국환경보건학회지
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• 제28권5호
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• pp.42-52
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• 2002

배수관망에서의 박테리아 재 증식은 큰 현안문제로 대두되고 있으며 이를 억제하기 위한 염소소독 또한 발암성의 부산물인 THMs(trihalomethanes)등을 생성시킬 우려 때문에 미국에서는 오존살균처리 또는 나노여과 (nanofiltration) 법으로 대체해 오고 있다. 그러나 종래의 많은 bench scale 실험결과를 통해 이러한 처리 이후에 잔존하는 미량의 유기물(assimilable organic carbon)이 박테리아 재 증식에 계속하여 영향을 주고 있다는 결과가 AOC(assimilable organic carbon)와 박테리아 재증식의 상관관계를 통하여 밝혀지고 있다. 그러나 현재까지 이러한 연구결과를 full-scale규모의 현장시설에서 직접 검토한 예는 없다. 따라서 본 실험은 미국플로리다주에 위치한 두 지역의 full-scale배수관망 시설을 선정하여 실시하였다. 첫 번째 시설은 오존 살균처리를 그리고 다른 한곳은 나노여과와 석회 연수법 (lime softening)을 병행한 처리법을 사용하고 있다. 박테리아 증식은 R2A 배지를 사용하는 HPC(heterotrophic plate counts)법으로 평가했으며 오존이 공급된 배수관망에서의 HPC 는 각 셈플링 지점의 AOC값을 이용한 지수모델과 높은 상관관계가 있음이 판명되었다($R^2$=0.97). 또한 오존처리는 100%이상의 AOC 농도증가를 나타냈다. 나노여과법과 석회연수법을 병행하고 있는 시설에서도 AOC에 근거한 지수모델과 상관관계를 나타냈다($R^2$=0.75). 그러나 BDOC(biodegradable dissolved organic carbon)는 박테리아 증식에 있어 매우 낮은 상관관계 값을 표시했다($R^2$=0.11). 결과적으로 종래의 많은 bench scale실험결과와 같이 AOC는 배수관망에서의 박테리아 증식과 크게 상관관계를 갖고 있는 것으로 밝혀졌다.

• Environmental Engineering Research
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• 제11권6호
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• pp.293-302
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• 2006

The reaction of ozone with NOM (Natural Organic Matter) can occur by two different pathways: that involving molecular ozone and by way of reactions with hydroxyl radicals which are produced from the decomposition of molecular ozone. As such, the formation of ketoacids and Assimilable Organic Carbon (AOC) can be controlled by controlling the pathway by which ozone reacts with NOM. The ratios of $[OH{\cdot}]/[O_3]$ ($R_{CT}$ values) were determined under the various ozonation conditions. The $R_{CT}$ values increased with increasing initial ozone concentration. The $R_{CT}$ values (ranges from 10 to $35^{\circ}C$) increased linearly as temperature increased (within the range from 10 to $35^{\circ}C$). However, $R_{CT}$ was independent of hydraulic retention time (HRT). Operational conditions were found to affect the formation of AOC. The conditions where the molecular ozone reaction predominated resulted in an increase in the formation of AOC.

• 한국동물생명공학회지
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• 제36권4호
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• pp.230-238
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• 2021

This study attempted to determine the characteristic features of postpartum dairy cows during their return to estrus. Moreover, it investigated the effects of abnormal ovarian cycles (AOC) on subsequent reproductive performance and the relationship between normal ovarian cycles (NOC) and the blood urea nitrogen (BUN) level postpartum. Incidentally, 56.3% of the Holstein cows and 66.7% of the Jersey cows had NOC, whereas the 43.7% and 33.3% of the Holstein and Jersey, respectively, had AOC. Within 100 days of calving, the cows with AOC had significantly lower rates of artificial insemination (AI) submission as well as pregnancy and a significantly longer interval to first AI, as compared to that in the cows with NOC. Additionally, the cows with NOC had a significantly higher first AI conception rate than that in the cows with AOC. In this study, of the 32 Holstein cows, 8 resumed their ovarian cycle within 20 days of calving, 10 resumed the cycle with 21-40 days of calving, 8 within 41-60 days of calving, while the remaining 6 did not resume their ovarian cycles until 60 days postpartum. Furthermore, the likelihood ratios of incidence of NOC are 0.93, 1.94, and 0.38, respectively, in the groups with BUN levels < 15, 15-19.9, and ≥ 20 mg/dl. In conclusion, AOC postpartum adversely affects reproductive performance such as AI submission rate, pregnancy rate, interval to first AI and first AI conception rate; moreover, an increase or decrease in the BUN levels beyond 15-19.9 mg/dL leads to the AOC postpartum.

• 상하수도학회지
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• 제32권2호
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• pp.159-168
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• 2018

Climate change is believed to increase the amount of dissolved organic matter in surface water, as a result of the release of bulk organic matter, which make difficult to achieve a high quality of drinking water via conventional water treatment techniques. Therefore, the natural water treatment techniques, such as managed aquifer recharge (MAR), can be proposed as a alternative method to improve water quality greatly. Removal of bulk organic matter using managed aquifer recharge system is mainly achieved by biodegradation. Biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) can be used as water quality indicators for biological stability of drinking water. In this study, we compared the change of BDOC and AOC with respect to pretreatment methods (i.e., ozone or peroxone). The oxidative pretreatment can transform the recalcitrant organic matter into readily biodegradable one (i.e., BDOC and AOC). We also investigated the differences of organic matter characteristics between BDOC and AOC. We observed the decreases in dissolved organic carbon (DOC) and the tryptophan-like fluorescence intensities. Liquid chromatographic - organic carbon detection (LC-OCD) analysis also showed the reduction of the low molecular weight (LMW) fraction (15% removed, less than 500 Da), which is known to be easily biodegradable, and the biopolymers, high molecular weight fractions (66%). Therefore, BDOC consists of a broad range of organic matter characteristics with respect to molecular weight. In AOC, low molecular weight organic matter and biopolymers fraction was reduced by 11 and 6%, respectively. It confirmed that biodegradation by microorganisms as the main removal mechanism in AOC, while BDOC has biodegradation by microorganism as well as the sorption effects from the sand. $O_3$ and $O_3+H_2O_2$ were compared with respect to biological stability and dissolved organic matter characteristics. BDOC and AOC were determined to be about 1.9 times for $O_3$ and about 1.4 times for $O_3+H_2O_2$. It was confirmed that $O_3$ enhanced the biodegradability by increasing LMW dissolved organic matter.