• 한국환경과학회지
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• 제10권3호
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• pp.247-252
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• 2001

This study was performed to evaluate the inactivation and microbial regrowth of heterotrophic and nitrifying bacteria using chloramine as a secondary disinfectant for drinding water distribution system. Three sets of the three reactors filled with the $Cl_2/NH_3-N$ ratio of 3:1, 4:1, and 5:1 were used in these experiments. Chloramine concentration were applied to each set of the reactors with $1mg/\ell$,\;2mg/\ell\;and\;3mg/\ell$, respectively. For the set with elapsed time and reached to zero level after 7 days. Heterotrophic bacteria remarkably increased and nitrification through the experimenatal period (21 day). Furthermore the regrowth of heterotrophic bacteria and nitrification were not found. More than $2mg/\ell$ of chloramine with $Cl_2/NH_3-N$ ratio of 3:1, the nitrification could be inhibited by 2 days of contact time.

• 한국환경보건학회지
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• 제32권4호
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• pp.282-291
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• 2006

This study investigated the inactivation of the total coliform, an indicator organism in chlorine and chlorine in order to control microbial regrowth for water distribution systems and select an appropriate disinfection strategy for drinking water systems. The disinfection effects of chlorine and chlorine dioxide with regard to the dosage of disinfectant, contact time and DOC was investigated experimentally. In spite of the consistency of chlorine residuals at approximately 0.2 mg/l, bacteria regrowth was detected in the distribution system and it was confirmed by the scanning electron microscope results. The influence of organic carbon change on the killing effect of chlorine dioxide was strong.

• 한국환경과학회지
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• 제16권1호
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• pp.121-128
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• 2007

This study performed in order to evaluate the effects of pipe materials on corrosion and bacteria regrowth using a laboratory scale batch test. Two varieties of feed water with different microbial conditions were selected: tap water, surface river water (Han River water), and five pipe materials; carbon steel, copper, galvanized iron, stainless steel, and PVC, Carbon steel and galvanized iron pipes showed higher corrosion rates than other materials. In terms of attached bacterial growth, pipes with PVC and stainless steel showed higher bacteria concentration compared to other materials. Pseudomonas vesicularis was the predominant bacteria found on biofilm. The behavior of bacterial growth in the pipes was observed using a scanning electron microscope.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.334-337
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• 2003

This study was carried out to investigate the effect of soil properties, such as soil organic matter(SOM) content and water content on die-off and regrowth of indigenous microbes due to in-situ ozonation. Four different soils were collected and the soil samples applied to different ozonation time(0-360 min) were incubated during 4 weeks. Population of the indigenous microbes was monitored during incubation period. The number of indigenous microbes in all samples dramatically decreased (more than 90%) within 30 minutes of ozone injection. With increased ozonation time by 360 minutes, the number of the indigenous microbes decreased by 99.99% in all samples. Die-off of the indigenous microbes due to ozone treatment was inversely proportional to SOM and water content. Especially, sample 3 and Sample 4 containing relatively high SOM content and water content showed high regrowth rate, and this resulted from the increase of water soluble and biodegradable organic fraction in soil water after ozone treatment. Soil sample ozonated for 360 minutes showed minor increase in microbial population during 4 weeks of incubation period.

• Asian-Australasian Journal of Animal Sciences
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• 제6권2호
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• pp.191-195
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• 1993

The application of fertilizer P to Desmodium intortum at 40, 60 and 100 kg/ha resulted in the P content of the legume regrowth being 0.10, 0.13 and 0.16% on a dry matter basis. When the forages were fed alone to sheep in metabolism pens the corresponding voluntary intakes by sheep of the three forages were 27.3, 42.7 and $54.3g/W_{kg}{^{0.75}}$, respectively. Provision of additional P by rapid infusion into the rumen each morning before any fresh food was offered depressed the voluntary intake of all three feeds. It is suggested that the adverse effect of supplementary P was probably caused by an induced deficiency of either Ca or Mg and led to a reduction in microbial activity in the rumen.

• 상하수도학회지
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• 제19권1호
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• pp.47-52
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• 2005

This study was conducted to evaluate the performance of submerged hollow fiber MF processes to treat secondary wastewater for water reuse. Specifically, membrane productivity and filtrate water quality were investigated under various operating conditions (i.e. flux, recovery, and backwash rate) at pilot-scale. Membrane fouling became more severe with increasing flux and recovery, suggesting that low flux operation (< 25 LMH) was desirable. At high flux operating(> 37.5 LMH), increasing backwash rate showed only limited success. The biofouling, quantified by PEPA and BFHPC, was also significant in wastewater reclamation, and biogrowth control by chlorine, were necessary to improve membrane productivity. Filtrate water qualities are in good compliance with water reuse regulations regardless of operating conditions (flux, recovery and backwash rate). Particle (e.g. turbidity) removal ranged from 89 to 98%, while only 11 to 21% of organics (e.g. NPDOC) were removed by MF membrane. Only small improvement in biostability (e.g. AOC) was achieved by MF system, and thus, without post disinfection, significant microorganisms might be present in the filtrate due to regrowth. Lastly, in order to further investigate pathogen removal, controlled microbial challenge tests were performed by monitoring Giardia, Cryptosporidium, bacteria and virus, and showed relatively good microbial removal.

• 수도
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• 제24권4호통권85호
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• pp.79-87
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• 1997

In an effort to prevent the formation of DBPs from disinfection and the microbial regrowth in distribution systems, the ozonation followed by biological filtration process in drinking water treatment train has been recently developed as an alternative process to reduce effectively water-born organic matter as precursor. There are, however, insufficient for the consistent information and data about the relation between ozone dosage based on organic surrogate parameter, TOC or DOC and effect of ozonation on BDOC formation. This study is to review critically for the effect of ozonation on biodegradability on the basis of published technical papers including the output from author's research laboratory. It truned out that : 1. ozonation in the presence of organic matter has a tendancy to increase in BDOC content, 2. the rate of BDOC formation was maximum below 1mg $O_3/mg$ DOC of ozone dose, but about maximum content of BDOC was obtainable at the range from 1.5mg $O_3/mg$ DOC to 2mg $O_3/mg$ DOC, 3. from above 1mg $O_3/mg$ DOC, the rate of BDOC formation became slow down, 4. from above 2mg $O_3/mg$ DOC, BDOC formation was quantitatively negligible, In conclusion, it needs further systematic study and research concerned to biodegradability and treatability by ozonation in terms of organic characteristics and experimental conditions because it was hard to find out the consistent experimental data comparable each other that were performed by numbers of research authors.

• 상하수도학회지
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• 제32권6호
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• pp.527-533
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• 2018

Microorganisms detected in the biofilm not only cause secondary pollution of drinking water such as taste, odor and pathogenic disease but also increase the amount of disinfectant due to microbial regrowth during the transportation of tap water. In this work, the influence of C/N ratio in tap water on the characteristics of biofilm growth was examined. The C/N ratio of the tap water sample was controlled at 100:5, 100:10, 100:20, 100:30, and 100:40 by adding appropriate amounts of dextrose and $(NH_4)_2SO_4$. Of the five C/N ratios, heterotrophic plate counts (HPC) was highest at the ratio of 100:10. Following the initial formation in all the five experimental conditions, natural detachment of the biofilm was observed. Extracellular enzyme activity (EEA) analyses showed that the change of the EEA during the experimental period was similar to that of the HPC, demonstrating a positive correlation between HPC and EEA. For TOC concentration in the tap water sample, approximately 75% of the TOC was consumed in 7 days of the experiment and 96% in 28 days. The TOC appeared to be relatively rapidly consumed at the initial phase of the biofilm growth. Consumption pattern of the ammonia nitrogen was different from the TOC consumption pattern showing the different role of ammonia nitrogen on the growth of biofilm.

• 대한환경공학회지
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• 제30권6호
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• pp.601-608
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• 2008

본 연구의 목적은 파일롯 규모의 입상활성탄지에서 흡착과 생물학적 제거 기작이 진행되는 장기간의 운전동안 전처리공정으로서 오존처리의 영향을 평가하는 것이다. 공정별로 용존 또는 생분해성 유기물질의 제거, DOM의 성상과 특성변화와 미생물의 증식의 변화를 평가하였다. 오존공정이 존재하는 입상활성탄 공정(전오존처리+활성탄 여과지; Pre O$_3$ + F/A, 후오존처리 + 활성탄 흡착지; Post O$_3$ + GAC)은 오존의 위치(전오존 후오존)에 상관없이 입상활성탄 단독공정(활성탄 여과지; F/A, 활성탄 흡착지; GAC)에 비해 생물학적 제거능이 활성화된 장기간 운영 후에 DOC, 친수성 용존유기물(HPI), BDOC와 AOC의 제거율이 10$\sim$20% 정도로 높았다. 오존공정은 전반적인 DOC 제거에는 큰 영향을 주지는 못했지만, AOC를 약 20% 정도로 감소시켜 관로내 미생물의 재증식을 저감하는데 기여할 것으로 생각된다. 활성탄 여재에 고정된 미생물의 생체량인 Biomass는 전처리로서 오존처리의 유.무에 상관없이 공정별로 큰 차이를 보이지 않은 반면에, 유출수에서의 HPC는 F/A나 GAC에 비해 Post O$_3$ + GAC에서 매우 낮았다.

• 생명과학회지
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• 제17권9호통권89호
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• pp.1284-1289
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• 2007

정수처리 공정에서 생물활성탄 (BAC) 공정은 미생물의 유기물 제거능을 극대화시킨 일종의 생물여과 공정이다 BAC 공정은 유기물과 미생물 재성장능을 효과적으로 제거한다. BAC 공정은 그 수계에 존재하는 미생물들이 활성탄에 부착 ${\cdot}$ 서식하며 수중의 천연유기물질을 기질로 이용하기 때문에 그 수계에 서식하는 미생물 종들에 매우 의존적이다. 본 연구는 낙동강 하류의 배리취수장 원수를 사용하여 생물활성탄에 의한 pilot-plant 공정을 운전하면서 SAC 공정에서의 활성탄 재질별로 배양작 (평판배양법) 및 비배양적 방법 (FISH)을 이용하여 SAC 부착세균의 군집구조 특성을 조사하였다. 실험결과 석탄계 재질의 부착세균 HPC 및 생산력이 각각 $1.20{\times}l0^7{\sim}56.2{\times}l0^7$ CFU/g, $1.2{\sim}3.7\;mg-C/m^3{\cdot}h$ 의 범위를 보여 세균 생체량과 DOC 제거율은 석탄계 재질이 가장 높은 것으로 나타났다. 배양적 방법으로 활성탄 재질별 부착세균을 동정한 결과 Pseudomonas 속이 우접하였고, 그 다음으로 Flavobacterium 속, Alcaligenes 속, Acinetobacter 속, Sphingomonas 속 등의 순으로 동정되었다. 또한, Pseudomonas 속 중 석탄계와 야자계 BAC에서는 Pseudomonas vesicularis, 목탄계 BAC에서는 Pseudomonas cepacia가 우점종으로 분포하였다. 비배양적 방법인 FISH 법을 이용한 세균 군집구조 조사결과 활성탄 재질별로 ${\alpha}$군집 27.0 ${\sim}$ 43.0%, ${\gamma}$ 군집 11.3 ${\sim}$ 28.6%, ${\beta}$ 군집 7.1 ${\sim}$ 22.0% 비율로 나타나 유기물 제거효율은 주로 ${\alpha}$ 군집에 의해 조절되어짐을 알 수 있었다.