• Journal of Environmental Health Sciences
• /
• v.43 no.6
• /
• 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.

• Journal of Korean Society on Water Environment
• /
• v.26 no.5
• /
• pp.871-879
• /
• 2010

To figure out the removal efficiency of indicator and pathogenic bacteria by unit processes of a sewage treatment plant using activated sludge process, analyses were done for incoming sewage, influent and effluent of primary clarifier, aeration tank, secondary clarifier and final discharge conduit of the plant. A matrix of bacterial items (average of bacterial reduction [log/ml], p value of paired t-test, number of decreased cases of twenty analyses, removal percentage only for decreased cases) between incoming sewage and final effluent of the plant were heterotrophic plate counts (1.54, 0.000, 20, 95.01), total coliforms (1.38, 0.000, 19, 83.94), fecal coliforms (0.90, 0.000, 20, 94.84), fecal streptococci (0.90, 0.000, 20, 98.08), presumptive Salmonella (0.23, 0.561, 7, 99.09), and presumptive Shigella (1.02, 0.002, 15, 92.98). Total coliforms, fecal coliforms, heterotrophic plate counts, and fecal streptococci showed highest decrease through secondary clarifier about 1-log (p<0.001) between 88% and 96%, and primary clarifier represented the significant (p<0.05) decrease. However, final effluent through discharge conduit showed higher total coliforms and fecal streptococci than effluent of secondary clarifier (p<0.05). In addition, final effluent once violated the water quality standard while effluent of secondary clarifier satisfied the standard. Hence some control measures including elimination of deposits in discharge conduit or disinfection of final effluent are necessary.

• Journal of Environmental Health Sciences
• /
• v.28 no.5
• /
• pp.42-52
• /
• 2002

Two full-scale distribution systems, one treating water by ozonation and another treating water by nanofiltration in parallel with lime softening, were monitored for bacterial growth. Both systems kept disinfectant residuals surf as chlorine and chloramine in their respective distribution systems. Bacterial growth was assessed by heterotrophic plate counts (HPC) on R2A agar. In the distribution systems fed by ozonated water, HPCs were correlated ($R^2$= 0.97) using an exponential model with the assimilable organic carbon (AOC) at each sampling site. Also, it was observed that ozonation caused a significant increase in the AOC concentration of the distribution system (over 100％ increase) as well as a significant increase in the bacterial counts of the distribution system (average increase over 100％). The HPCs from the distribution systems fed by nanofiltration in parallel with lime-softening water also displayed an exponential correlation ($R^2$ = 0.75) with an exponential model based on AOC. No significant correlation was found between bacteria growth on R2A agar and BDOC concentrations. Therefore, in agreement with previous work, bacterial growth in the distribution systems was found to correlate with AOC concentrations.

• Journal of Microbiology and Biotechnology
• /
• v.14 no.6
• /
• pp.1114-1119
• /
• 2004

The biofilms on pipe walls in water distribution systems are of interest since they can lead to chlorine demand, coliform growth, pipe corrosion, and water taste and odor problems. As such, the study described in this paper is part of an AWWARF and Tampa Bay Water tailored collaboration project to determine the effect of blending different source waters on the water quality in various distribution systems. The project was based on 18 independent pilot distribution systems (PDS), each being fed by a different water blend (7 finished waters blended in different proportions). The source waters compared were groundwater, surface water, and brackish water, which were treated in a variety of pilot distribution systems, including reverse osmosis (RO) (desalination), both membrane and chemical softening, and ozonation-biological activated carbon (BAC), resulting in a total of 7 different finished waters. The observations from this study consistently demonstrated that unlined ductile iron was more heavily colonized by a biomass than galvanized steel, lined ductile iron, and PVC (in that order) and that the fixed biomass accumulation was more influenced by the nature of the supporting material than by the water quality (including the secondary residual levels). However, although the bulk liquid water cultivable bacterial counts (i.e. heterotrophic plate counts or HPCs) did not increase with a greater biofilm accumulation, the results also suggested that high HPCs corresponded to a low disinfectant residual more than a high biofilm inventory. Furthermore, temperature was found to affect the biofilms, plus the AOC was important when the residual was between 0.6 and 2.0 mg $Cl_2/l$. An additional aspect of the current study was that the potential of the exoproteolytic activity (PEPA) technique was used along with a traditional so-called destructive technique in which the biofilm was scrapped off the coupon surface, resuspended, and cultivated on an R2A agar. Both techniques indicated similar trends and relative comparisons among the PDSs, yet the culturable biofilm values for the traditional method were several orders of magnitude lower than the PEPA values.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.4
• /
• pp.779-781
• /
• 2010

After preliminary tests indicated an increased number of heterotrophic bacteria, we investigated possible sources of contamination in a neonatal intensive care unit (NICU) water distribution system. Scanning electron microscopic examination of flexible metallic hoses associated with the system revealed the presence of a biofilm; partial 16S rDNA sequencing revealed that the biofilm contained Blastomonas natatoria. Purgation of the water system three times a day, reinforced faucet cleaning, decreasing the cold water temperature to $12^{\circ}C$, and six repeated chlorinations at concentrations as high as 2 mg/l were not sufficient to eradicate the bacterial contamination. Replacing all of the rubber-interior flexible metallic hoses with teflon-lined hoses, followed by heating the water to $70^{\circ}C$, successfully controlled the bacteria.

• Korean Journal of Microbiology
• /
• v.42 no.2
• /
• pp.95-102
• /
• 2006

To evaluate bacteriological water quality of groundwater in Yeungnam Province, samples were taken from 123 locations during summer and 117 locations during winter. The medians of heterotrophic plate counts.(HPCs) were 30 CFU/mL for the summer samples and 40 CFU/ml for the winter, and more than 25% showed HPCs higher than 100 CFU/ml. Coliform bacteria were detected from 46% of the summer samples and 30% of the winter. In these coliform-positive samples, the medians of coliform counts were 20 CFU/ml for the summer samples and 4 CFU/ml for the winter. Genera such as Citrobacter, Enterobacter, Escherichia, Klebsielia, Pantoea, Rahnellia, and Serratia were identified from the coliform isolates; among them, 48% were members of the genus Enterobacter. While E. cloacae, E. amnigenus, and K. pneumoniae were the most frequently isolated species, E. coli was isolated only from 1 location. The coliform counts were positively correlated with the HPCs, which also positively correlated with water temperature. The results of present study provide further insight on the extent of groundwater contamination with coliform bacteria.

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.6
• /
• pp.527-533
• /
• 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.

• Journal of Korean Society of Water and Wastewater
• /
• v.33 no.5
• /
• pp.395-404
• /
• 2019

The point-of-use water dispenser systems are widely used because of convenience in handling and demand for high-quality drinking water. The application has been increased recently in the public places such as department stores, universities and the rest areas in express ways. Improvement of water qualities by the dispenser systems was compared with tap water in this study. The tap water is supplied to the dispenser as the influent of the dispenser system. The twelve dispensers in the public places were used. The five dispensers used reverse osmosis as the main filter and other dispensers used various filters such as ultrafiltration, nanofiltration, and alumina filter. The water quality indicators for sanitation safety, i.e., turbidity and total coliforms, were evaluated. Other water qualities such as pH, residual chlorine, heterotrophic plate count (HPC), and total cell counts were also analyzed. By the point-of-use water dispenser, the turbidity, residual chlorine and pH were decreased and the HPC and total cell counts were increased. The t-test results revealed that the HPC of the tap waters were not significantly different from the treated waters but the total cell counts of the two groups were significantly different. The low pH of the RO filter treatment was also significantly different from the tap waters. This study will contribute to understand the role of the point-of-use water dispenser in improving water quality and to identify key water quality for the proper maintenance of the dispenser systems.

• Applied Chemistry for Engineering
• /
• v.19 no.1
• /
• pp.122-128
• /
• 2008

We evaluated the relationship between the multiplication of heterotrophic microorganisms and physicochemical factors in the final discharged sewage water from J municipal waste water treatment plants. Dissolved organic carbon (DOC) was the most crucial factor influencing multiplication of heterotrophic plate counts (HPC) among the water quality variables selected. Degrading bacteria, such as proteolytic bacteria, lipholytic bacteria, starch degrading bacteria, cellulolytic bacteria, and pectinolytic bacteria, were monitored to understand the condition of nutrients in finished sewage effluent. The percentages of lipid and protein combined occupied 81% in finished sewage water. The multiplication of HPC showed the highest value in August. The formation of trihalomethane (THM) was low in the finished discharge water during chlorine disinfection, which was $71{\mu}/L$ (which was less than $100{\mu}/L$- the standard of drinking water quality) with 10 mg/L of chlorine during 15 min.

• Ocean and Polar Research
• /
• v.25 no.1
• /
• pp.21-30
• /
• 2003

Seasonal fluctuations of physico-chemical and biological aspects of the environment were studied in Vladivostok harbour (Golden Horn Bay, the East Sea/Sea of Japan). The benthic community structure was described with a focus on size-spectra (bacteria, meio- and macrofauna) related with the chemical environment and chemical fluxes in sediment and to reveal their possible ecological role in the process of bioremediation of the environment. Samples from two sites with different concentrations of heavy metals (Fe, Zn, Cu, Pb, Mn, Cr, Ni Cd, Co) and petroleum hydrocarbon were assessed by a number of methods. These included plate counts of culturable bacteria, observation through a scanning electron (SEM) and transmission electron microscope (TEM). These approaches were complemented with microscopic assessments of the diversity of the benthic community. The specific communities had a limited number of species, tolerant to abnormally high levels of toxic compounds. The dominant species were presented by several sho.1-lived small polychaetes (Capitella capitata) and nematodes (Oncholaimium ramosum). The highest population density was recorded in microbenthos, in various diatoms, various physiological groups of bacteria which participate in biomineralization: marine heterotrophic bacteria, which oxidized oil, black oil in addition to groups resistant to heavy metals. They have the entire set of mechanisms for neutralizing the negative effect of those compounds, forming the detrital food web and biogeochemical circulation of material in sediments, which results in the biological self-recycling of sea basins. Macro- and meiobenthic organisms were more sensitive to a greater extent of $H_2S$ and petroleum hydrocarbons than to metal content, but the within-site rankings were the same as those achieved for microbiological analyses.