Bacterial colonization of domestic reverse-osmosis water filtration units

1989 ◽  
Vol 35 (11) ◽  
pp. 1065-1067 ◽  
Author(s):  
Pierre Payment
Keyword(s):  
Drinking Water ◽  
Reverse Osmosis ◽  
Heterotrophic Bacteria ◽  
Bacterial Colonization ◽  
Water Filtration ◽  
Water Reservoirs ◽  
Colony Forming Units ◽  
Plate Counts ◽  
Bacterial Content ◽  
Heterotrophic Plate Counts

We have analyzed the bacterial content of water from the reservoirs of 300 reverse-osmosis units installed in households. The heterotrophic plate counts on R2A medium (20 and 35 °C) ranged from 0 to 107 colony forming units per millilitre (cfu/mL). Most reservoirs contained water with bacterial counts between 104 and 105 cfu/mL. The bacteria identified were Pseudomonas (not aeruginosa), Alcaligenes or Moraxella, Acinetobacter, Flavobacterium, and Chromobacterium. This report emphasizes the importance of bacterial colonization by heterotrophic bacteria in water reservoirs from domestic reverse-osmosis units.Key words: drinking water, bacteria, reverse-osmosis filter, regrowth.

scholarly journals Determination of cytotoxicity and invasiveness of heterotrophic plate count bacteria isolated from drinking water

2002 ◽  
Vol 2 (3) ◽  
pp. 115-122 ◽  
Author(s):  
D. Pavlov ◽  
C.M.E. de Wet ◽  
W.O.K. Grabow ◽  
M.M. Ehlers
Keyword(s):  
Drinking Water ◽  
Health Risk ◽  
Heterotrophic Bacteria ◽  
Penicillin G ◽  
Plate Count ◽  
Heterotrophic Plate Count ◽  
Water Supplies ◽  
Plate Counts ◽  
Study Support ◽  
Heterotrophic Plate Counts

Evidence has been presented that some heterotrophic bacteria often detected in drinking water supplies possess features associated with pathogenicity. This suggests that even the low numbers of heterotrophic bacteria considered acceptable by drinking water specifications may constitute a health risk, particularly to immunocompromised consumers. In this study, 339 bacteria were isolated at random from routine heterotrophic plate count (HPC) tests on selected drinking water supplies in South Africa. In a first screen for potentially pathogenic properties, 188 of the isolates (55.5%) displayed a- or b-haemolysis on blood agar. Further analysis of the haemolytic isolates for enzymes associated with virulence revealed the presence of chondroitinase (5.3%), coagulase (16.0%), DNase (60.6%), elastase (33.0%), fibrinolysin (53.7%), gelatinase (62.2%), hyaluronidase (21.3%), lecithinase (47.9%), lipase (54.8%) and proteinase (64.4%) of the isolates. No fluorescein or pyocyanin was detected in any of the isolates. Among the haemolytic isolates 68.6% were resistant to oxacillin (1 μg), 59.6% to penicillin G (2 units), 47.3% to penicillin G (10 units), 53.7% to ampicillin (10 μg) and 42.6% to ampicillin (25 μg). Cytotoxicity, invasiveness and adherence properties of the haemolytic isolates was determined on HEp-2 and Caco2 cell lines. Among the haemolytic isolates 96% were cytolytic on the HEp-2 cell line. All the haemolytic isolates adhered to HEp-2 and Caco2 cells but gram-negative isolates tended to adhere in larger numbers than gram-positive isolates. HEp-2 cells were invaded by 42% of the haemolytic isolates. Heterotrophic bacteria, which most frequently revealed the above features associated with pathogenicity included species of the following genera: Aeromonas, Acinetobacter, Aureobacterium, Bacillus, Klebsiella, Moraxella, Pseudomonas, Staphylococcus, Tsukamurella and Vibrio. The results obtained in this study support earlier indications that bacteria detected by routine heterotrophic plate counts on drinking water supplies may include bacteria associated with potentially pathogenic properties. The extent to which these bacteria in drinking water supplies may constitute a health risk remains to be investigated.

Chlorine requirement for biologically stable drinking water after nanofiltration

2013 ◽  
Vol 14 (3) ◽  
pp. 405-413
Author(s):  
Y. Ohkouchi ◽  
Y. Yata ◽  
R. Bun ◽  
S. Itoh
Keyword(s):  
Drinking Water ◽  
Water Distribution ◽  
Flow Reactor ◽  
Heterotrophic Bacteria ◽  
Tap Water ◽  
Biological Stability ◽  
Bacterial Regrowth ◽  
Chlorine Residual ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

There is considerable interest in minimizing the chlorine residual in Japan's tap water because of increasing consumer complaints about the chlorinous odor of drinking water. However, minimization of the chlorine residual requires stricter control of biodegradable organics in finished water to ensure biological stability during water distribution. In this context, we investigated the improvement of biological stability of drinking water by nanofiltration (NF). The removal of assimilable organic carbon (AOC) was 52% on average, but showed large seasonal variation. It was found to be difficult to maintain the acceptable AOC level for biologically stable water by NF. In addition, significant bacterial regrowth in NF permeates was still observed without chlorination, although 52% AOC was removed. Then, the chlorine concentration required to prevent bacterial regrowth during distribution of nanofiltrated water was determined using continuous-flow reactor systems. The heterotrophic plate counts (HPC) densities in biofilm were monitored at different chlorine conditions. The results indicated that the NF process could significantly reduce the chlorine requirement of the finished water. The relationship between free chlorine residual and HPC in biofilm formed from 1 μgC AOC showed that a trace level of chlorine residual, <0.1 mg/L, could inactivate heterotrophic bacteria and prevent biofilm formation.

Biofilm formation in drinking water affected by low concentrations of phosphorus

2002 ◽  
Vol 48 (6) ◽  
pp. 494-499 ◽  
Author(s):  
Markku J Lehtola ◽  
Ilkka T Miettinen ◽  
Pertti J Martikainen
Keyword(s):  
Drinking Water ◽  
Organic Carbon ◽  
Microbial Growth ◽  
Available Phosphorus ◽  
Phosphorus Addition ◽  
Drinking Waters ◽  
Low Concentrations ◽  
Geographical Regions ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

There are geographical regions where microbial growth in drinking waters is limited by phosphorus instead of organic carbon. In these drinking waters even a low amount of phosphorus can strongly enhance microbial growth. The formation of biofilm can be limited by low availability of phosphorus in drinking waters with low content of phosphorus. The formation of biofilms on polyvinyl chloride plates was studied in laboratory experiments with water containing 48 μg/L assimilable organic carbon and 0.19 μg/L microbially available phosphorus. We found that low additions of phosphate (1–5 μg/L PO43–-P) to water increased microbial growth in the water and in the biofilm. The effect of phosphorus on microbial growth could be detected by determining either the microbial cell production or the content of ATP in biofilms. Also, in steady-state biofilms, microbial concentrations were higher with phosphorus addition as enumerated by heterotrophic plate counts on R2A-agar and acridine orange direct counting. This work confirms the earlier findings of the importance of phosphorus for microbial growth in humic-rich drinking waters.Key words: biofilm, drinking water, microbes, phosphorus.

scholarly journals Correlations between total cell concentration, total adenosine tri-phosphate concentration and heterotrophic plate counts during microbial monitoring of drinking water

2008 ◽  
Vol 1 (1) ◽  
pp. 71-86 ◽  
Author(s):  
E. Siebel ◽  
Y. Wang ◽  
T. Egli ◽  
F. Hammes
Keyword(s):  
Drinking Water ◽  
Cell Concentration ◽  
Rapid Determination ◽  
Total Cell ◽  
Detection Methods ◽  
Microbial Quality ◽  
Culturable Bacteria ◽  
Water Quality Control ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

Abstract. The general microbial quality of drinking water is normally monitored by heterotrophic plate counts (HPC). This method has been used for more than 100 years and is recommended in drinking water guidelines. However, the HPC method is significantly handicapped because it is time-consuming and restricted to culturable bacteria. Recently, rapid and accurate detection methods have emerged, such as adenosine tri-phosphate (ATP) measurements to assess microbial activity in drinking water, and flow cytometry (FCM) to determine the total cell concentration (TCC). It is necessary and important for drinking water quality control to understand the relationships among the conventional and new methods. In the current study, all three methods were applied to 200 drinking water samples obtained from two local buildings connected to the same distribution system. Samples were taken both on normal working days and weekends, and the correlations between the different microbiological parameters were determined. The results showed that the rapid determination methods (i.e., FCM and ATP) correlated significantly (R2=0.69), but only a weak correlation (R2=0.31) was observed between the rapid methods and conventional HPC data. With respect to drinking water monitoring, both FCM and ATP measurements were confirmed to be useful and complimentary parameters for rapid assessing of drinking water microbial quality.

Bacterial succession within a biofilm in water supply lines of dental air–water syringes

1995 ◽  
Vol 41 (7) ◽  
pp. 647-654 ◽  
Author(s):  
B. D. Tall ◽  
H. N. Williams ◽  
K. S. George ◽  
R. T. Gray ◽  
M. Walch
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Water Supply ◽  
Bacterial Colonization ◽  
Dental Equipment ◽  
Colony Forming Units ◽  
Bacterial Succession ◽  
Plate Counts ◽  
Acinetobacter Spp ◽  
Scanning Electron

Biofilms have been implicated as reservoirs for bacterial contamination of water delivered by dental air–water syringes. A 6-month study was done of bacterial colonization and biofilm formation in plastic water supply lines connected to dental air–water syringes. Changes in biofilm flora were observed by both scanning electron microscopy and bacteriologic culture. By day 7, many rod- and spiral-shaped bacteria had colonized the ridged surface of the luminal wall of the tubing, as revealed by scanning electron microscopy. By day 30, individual microcolonies were embedded in extracellular polymeric material. By day 120, these microcolonies had begun to coalesce, and by day 180 the biofilm had developed into a multilayered, heterogenous mixture of microcolonies. The mean aerobic plate counts of colony-forming units of planktonic and biofilm populations were, in log10 values, 5.9 ± 0.54/mL and 4.2 ± 0.82/cm2, respectively. Early colonizers were predominantly Pseudomonas spp., but included Pasteurella, Moraxella, Ochrohactrum, and Aeromonas spp. Flavobacterium and Acinetobacter spp. were observed later. Many of these organisms are opportunistic pathogens. These results demonstrate the longitudinal dynamics of biofilm formation.Key words: dental equipment, air–water syringes, biofilms.

Effect of dead cells on biofouling in the reverse osmosis process

2013 ◽  
Vol 13 (5) ◽  
pp. 1396-1401
Author(s):  
Myung Seop Shin ◽  
Lan Hee Kim ◽  
Sung-Jo Kim ◽  
Chang-Min Kim ◽  
Kyu-Jung Chae ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Biofilm Formation ◽  
Extracellular Polymeric Substances ◽  
Live Cells ◽  
Feed Water ◽  
Fouling Control ◽  
Flux Decline ◽  
Low Concentrations ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

Biofilm formation in membrane processes causes a flux decline, pressure drop increase, and other adverse effects. Understanding the mechanisms of fouling, control, and cleaning are important in order to resolve fouling problems. In this paper, the effect of cell viability on biofouling was studied via a feed water analysis and membrane autopsy. Pseudomonas aeruginosa PAO1 was used as the model bacteria. Biofouling tests were divided into two parts: live cells and dead cells (autoclaved cells). The feed water was periodically collected every 3 h to analyze the total direct counts (TDCs), heterotrophic plate counts (HPCs), and extracellular polymeric substances (EPS). A membrane autopsy was performed to characterize the fouled membrane through TDCs and EPS. When dead cells were inoculated into the feed water, low concentrations of TDCs and EPS were measured in both the feed water and fouled membrane. As a result, it was determined that initial flux decline by biofouling can be reduced if feedwater is disinfected before the reverse osmosis process.

scholarly journals Membrane Fouling and Chemical Cleaning in Three Full-Scale Reverse Osmosis Plants Producing Demineralized Water

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Florian Beyer ◽  
Judita Laurinonyte ◽  
Arie Zwijnenburg ◽  
Alfons J. M. Stams ◽  
Caroline M. Plugge
Keyword(s):  
Reverse Osmosis ◽  
Membrane Fouling ◽  
Full Scale ◽  
Feed Water ◽  
Chemical Cleaning ◽  
Laboratory Setup ◽  
Plant Chemical ◽  
Plate Counts ◽  
Cleaning Procedures ◽  
Heterotrophic Plate Counts

Membrane fouling and cleaning were studied in three reverse osmosis (RO) plants. Feed water was secondary wastewater effluent, river water, and surface water. Membrane autopsies were used for fouling characterization. Fouling layer measurements included total organic carbon (TOC), adenosine triphosphate, polysaccharides, proteins, and heterotrophic plate counts. In all locations, membrane and spacer fouling was (bio)organic. Plant chemical cleaning efficiencies were evaluated from full-scale operational data and cleaning trials in a laboratory setup. Standard cleaning procedures were compared to two cleaning procedures specifically adapted to treat (bio)organic fouling using commercial blend cleaners (mixtures of active substances). The three RO plants were impacted by irreversible foulants causing permanently decreased performance in normalized pressure drop and water permeability even after thorough chemical cleaning. The standard plant and adapted cleaning procedures reduced the TOC by 45% on average, with a maximum of ~80%. In general, around 20% higher biomass removal could be achieved with adapted procedure I compared to adapted procedure II. TOC measurements and SEM showed that none of cleaning procedures applied could remove foulants completely from the membrane elements. This study underlines the need for novel cleaning approaches targeting resistant foulants, as none of the procedures applied resulted in highly effective membrane regeneration.

scholarly journals Correlations between total cell concentration, total adenosine tri-phosphate concentration and heterotrophic plate counts during microbial monitoring of drinking water

2008 ◽  
Vol 1 (1) ◽  
pp. 1-6 ◽  
Author(s):  
E. Siebel ◽  
Y. Wang ◽  
T. Egli ◽  
F. Hammes
Keyword(s):  
Drinking Water ◽  
Cell Concentration ◽  
Rapid Determination ◽  
Total Cell ◽  
Detection Methods ◽  
Microbial Quality ◽  
Culturable Bacteria ◽  
Water Quality Control ◽  
Plate Counts ◽  
Heterotrophic Plate Counts

Abstract. The general microbial quality of drinking water is normally monitored by heterotrophic plate counts (HPC). This method has been used for more than 100 years and is recommended in drinking water guidelines. However, the HPC method is handicapped because it is time-consuming and restricted to culturable bacteria. Recently, rapid and accurate detection methods have emerged, such as adenosine tri-phosphate (ATP) measurements to assess microbial activity in drinking water, and flow cytometry (FCM) to determine the total cell concentration (TCC). It is necessary and important for drinking water quality control to understand the relationships among the conventional and new methods. In the current study, all three methods were applied to 200 drinking water samples obtained from two local buildings connected to the same distribution system. Samples were taken both on normal working days and weekends, and the correlations between the different microbiological parameters were determined. TCC in the samples ranged from 0.37–5.61×105 cells/ml, and two clusters, the so-called high (HNA) and low (LNA) nucleic acid bacterial groups, were clearly distinguished. The results showed that the rapid determination methods (i.e., FCM and ATP) correlated well (R2=0.69), but only a weak correlation (R2=0.31) was observed between the rapid methods and conventional HPC data. With respect to drinking water monitoring, both FCM and ATP measurements were confirmed to be useful and complimentary parameters for rapid assessing of drinking water microbial quality.

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