• Environmental Engineering Research
• /
• 제24권1호
• /
• pp.17-23
• /
• 2019

This study monitored changes in the level of heterotrophic bacteria in the filtrate and investigated the effect of stagnant water on it, using a batch-operated, gravity-driven membrane system for household water treatment. The filtration test was carried out in the presence and absence of stagnant water in the filtrate line. The results showed that stagnant water accelerated the heterotrophic bacteria levels, measured by heterotrophic plate count, even though the heterotrophic plate count of the filtrate finally increased up to $10^5CFU/mL$ regardless of the presence of stagnant water. When the change in heterotrophic plate count of a batch was monitored over filtration time, heterotrophic plate count of the filtrate rapidly decreased within 5 min for each batch filtration. Biofilm formation on the filtrate line was observed in the presence of stagnant water. The biofilm fully covered the filtrate line and contained numerous microorganisms. During storage after filtration, heterotrophic plate count increased exponentially. To improve the filtrate quality of a filtration-based household water treatment system, therefore, the stagnant water in the filtrate line should be minimized, the filtrate produced at the first 5 min is recommended not to be used as potable water, and the storage of filtrate should be avoided.

• 한국물환경학회지
• /
• 제40권4호
• /
• pp.161-167
• /
• 2024

The demand for bottled water in South Korea is steadily increasing, but there are challenges regarding water sources and violations of water quality standards. Consumers struggle to identify products that do not meet these standards, highlighting the need for improved water management. This study aims to investigate the use of flow cytometry to identify microbial behavior in bottled water. Twelve different bottled water brands were selected for this study. A novel non-culture-based analysis method called total cell count via flow cytometry was utilized, which is not commonly used to assess drinking water quality. This method was compared to conventional culture-based methods for heterotrophic plate count and E. coli experiments, in order to introduce new indicators for hygiene management. Adenosine triphosphate analysis was also conducted to assess cell activity, and total organic carbon was measured to determine the presence of organic matter. The total cell counts varied among the different bottled water brands. The adenosine triphosphate levels ranged from 37.1ng/L to 221.7ng/L, while the total organic carbon ranged from 0.4 to 0.6 mg/L. Furthermore, E. coli was not detected in any of the bottled waters, and with the exception of two cases, the levels of heterotrophic bacteria did not exceed the drinking water standard of 100 CFU/mL. This study demonstrated a correlation between total cell count and heterotrophic plate count, suggesting that non-culture-based analysis could be valuable in promptly assessing microbial contamination, in contrast to the conventional methods that require approximately 48 hours for incubation.

• 상하수도학회지
• /
• 제19권2호
• /
• pp.181-192
• /
• 2005

This study evaluated the effect of factors influencing the initial biofilm formation in drinking water distribution pipe by running experiments using a $2^{4-1}$ fractional factorial experimental design with a replicate. Important variables used for assessing biofilm formation included BDOC(biodegradable dissolved organic carbon), viable heterotrophic bacteria present in drinking water, water temperature, and shear stress at two levels each. Based on the statistical analysis of biofilm levels measured as attached HPC(heterotrophic plate count) and community-level assay, the main factors that have significant effects on biofilm formation were found to be viable heterotrophic bacteria and BDOC. Water temperature only exhibited significant effect on the levels of attached HPC, while shear stress was not a significant factor under given conditions. Moreover, the statistical analysis revealed that interactions between the important variables were not statistically significant at a 0.05 significance level.

• 한국환경보건학회지
• /
• 제43권6호
• /
• pp.499-508
• /
• 2017

Objective: This study was conducted to investigate changes in microbiological quality according to various storage conditions in the drinking process of bottled mineral water. Methods: Heterotrophic plate counts ($21^{\circ}C$ and $36^{\circ}C$) and pathogenic indicators (total coliforms, fecal Streptococcus, Pseudomonas aeruginosa, Clostridium perfringens, Salmonella, and Shigella) were analyzed in commercial bottled mineral water stored under different conditions ($4^{\circ}C$, $20-25^{\circ}C$, $36^{\circ}C$) after injecting saliva. The heterotrophic plate counts were analyzed twice per day for the first week and once per day for the three weeks after. Pathogenic indicators were analyzed at the beginning and end (initial and final). Results: The results of the microbiological quality of the bottled mineral water in contact with saliva showed that heterotrophic plate counts ($21^{\circ}C$) had a tendency to be sustained or decrease slightly after 10 days. Heterotrophic plate counts ($36^{\circ}C$) had a high population in the initial samples and gradually decreased at $4^{\circ}C$ storage, but it remained constantly high in storage at $20-25^{\circ}C$ and $36^{\circ}C$. In the general drinking condition, the population was slightly higher than the control, but the overall trend was similar. Conclusions: As a result of the microbiological quality of mineral bottled water in contact with saliva during the process of drinking, heterotrophic plate counts ($21^{\circ}C$ and $36^{\circ}C$) showed a high population compared to the control, which was only opened and not in contact with saliva. In some samples, pathogenic indicators were also detected. Therefore, it is desirable to consume bottled mineral water as soon as possible after opening.

• 미생물학회지
• /
• 제31권3호
• /
• pp.245-254
• /
• 1993

1991년 9월부터 1992년 9월까지 23회에 걸쳐 서울시 구의정수장의 상수도계통 즉 원수와 정수 및 이곳에서 공급되는 단일 배급수계통의 3개 수돗물에서 종속영양세균(heterotrophic plate count : HPC) 과 장내세균(Enterobacteriaceae : total coliforms) 의 분포를 조사하였다. $R_{2}A$ 한천배지에서의 종속영양세균수는 원수 $1.22{\times}10^{3}~3.05{\times}10^{5}$ 정수 $1.50{\times}10^{1}~4.29{\times}10^{3}$, 수돗물 $2~5.41{\times}10^{3}$ cfu/100ml, 수돗물 0-47.5 cfu/100 ml 의 범위였으며, m-T7 한천배지에서의 손상된장내세균을 포함하는 장내세균수는 전수 0-27, 수돗물 0-35 cfu/100 ml/의 범위였다. 이러한 결과로부터 정수장에서 공급된 물이 배급수관을 통하여 공급되면서 종속영양세균 및 장내세균의 개체수가 증가하는 세균재생장 현상이 발생한다는 것을 확인하였다. 종속영양세균의 동정결과 원수, 정수, 수돗물을 포함하는 상수도계통의 물에서는 Peudomonas 와 Acinetobacter 가 우점하였으나, 원수에서는 Pseudomonas 의 비율이, 그리고 정수와 수돗물에서는 Acinetobacter 의 비율이 상대적으로 높은 것으로 나타났다. 장내세균은 Enterobacter agglomerans 가 우점종이었으며, 수돗물에서는 정수에서 검출되지 않았던 Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae, Shigella dysenteriae 등의 기회성 및 병원성 장내세균도 검출되었다.

• Journal of Microbiology and Biotechnology
• /
• 제17권9호
• /
• pp.1558-1562
• /
• 2007

To elucidate the influence of pipe materials on the VBNC (viable but nonculturable) state and bacterial numbers in drinking water, biofilm and effluent from stainless steel, galvanized iron, and polyvinyl chloride pipe wafers were analyzed. Although no HPC (heterotrophic plate count) was detected in the chlorinated influent of the model system, a DVC (direct viable count) still existed in the range between 3- and 4-log cells/ml. Significantly high numbers of HPC and DVC were found both in biofilm and in the effluent of the model system. The pipe material, exposure time, and the season were all relevant to the concentrations of VBNC and HPC bacteria detected. These findings indicate the importance of determining the number of VBNC cells and the type of pipe materials to estimate the HPC concentration in water distribution systems and thus the need of determining a DVC in evaluating disinfection efficiency.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
• /
• pp.132-135
• /
• 2003

Endotoxin concentrations were measured from 69 point-of-use(POU) water treatment system(WTS) by using Limulus amebocyte lysate(LAL) assay, and the results were compared to heterotrophic bacterial data. Endotoxin concentrations in all POU WTS water samples and tap waters varied within the range 0.8-79.1EU mL$\^$-1/ and 0.1-3.4EU mL$\^$-1/, respectively, The correlations between endotoxin concentration and HPC bacteria from the water samples showed not significant(r=0.18).

• 한국물환경학회지
• /
• 제16권4호
• /
• pp.431-443
• /
• 2000

Water quality data from water treatment plants in Korea during 1994-1998 were investigated to find out the characteristics of their non compliance. The number of plants surveyed were approximately 600 and the number of samples were over 30,000. Ten parameters of water quality selected in this study and their non compliance % (inside parenthesis) were as follows: Heterotrophic plate count (0.14%), Total coliforms (0.08%), $NH_3$-N (0.29%), $NO_3$-N (0.14%), THMs (0.02%), Turbidity (0.11%), Residual chlorine (5.5%), $KMnO_4$ consumption (0.04%), Hardness (0.03%), pH (0.07%). These levels of non compliance were compared to those obtained from WIDB (Water Industry Database, 1996) of American Water Works Association. This study strongly supported that small water plants (<10,000 tons/day) were more vulnerable in meeting the regulation criteria of many water quality parameters such as Heterotrophic plate count. Total coliforms, $NO_3$-N, THMs, Turbidity, Residual chlorine, $KMnO_1$ consumption, Hardness and pH. The $NH_3$-N concentration was especially high in winter and its violation was frequently found in the specific areas such as the downstream of major rivers. The average THMs concentration was surprisingly low, indicating $13{\mu}g/L$ which is 43% of US. Accordingly, these characteristics must be reflected in establishing the effective management of water quality policy of drinking water in Korea.

• 미생물학회지
• /
• 제49권4호
• /
• pp.321-327
• /
• 2013

본 연구에서는 암모니아 산화세균과 종속영양세균을 포함한 세균 생물막에 대한 chlorite ($0.66{\pm}0.01mg/L$)의 영향을 monochloramine ($1.77{\pm}0.03mg/L$)의 존재 유무에 따른 조건에서 알아보았다. Chlorite 단독 또는 monochloramine과 함께 적용한 경우에서 공히 생물막과 물 시료에 존재하는 암모니아 산화세균은 검출한계($0.6MPN/cm^2$ and 0.2 MPN/ml)에 근접한 수준으로 감소되는 것으로 나타났지만, chlorite/monochloramine으로 함께 첨가했을 때의 저해효과가 더욱 크게 나타났다. 종속영양세균의 경우 암모니아 산화세균과 달리 chlorite에 의한 저해가 거의 나타나지 않았다. 하지만 chlorite/monochloramine으로 적용한 경우 생물막과 물 시료에서 종속영양세균의 개체 수는 대조군 대비 각각 3.1 log와 3.0 log 감소하는 상당한 저해 효과를 보여주었다. 이러한 결과는 상수관망에 형성된 생물막에 존재하는 질산화 세균과 종속영양세균에 대한 효과적 제어방법중의 하나로 chlorite와 monochloramine 혼합사용의 성공적 가능성을 제시해 준다.

• Environmental Engineering Research
• /
• 제22권1호
• /
• pp.55-60
• /
• 2017

Provision of safe, accessible, and good water quality in the community is an important step towards reducing various waterborne illnesses. However, improving the quality of water should include spreading awareness to the public regarding the importance of cleaning their household water tanks. The aim of this study was to investigate the microbial quality of water of household water tanks in Dubai. The water samples from household water tanks were collected from forty houses, and a questionnaire was given to the residents to determine the history of the water tanks. The membrane filtration technique was used to quantify heterotrophic and total coliform bacteria on plate count agar and the violet red bile agar respectively. The overall results of this study have shown that 18 out of total 40 household water tanks contained different types of bacteria concentration level beyond local and widely accepted international standards. The overall results of this study indicated that there is a lack of awareness among residents regarding the importance of maintaining proper sanitation and hygiene of the household water tanks.