published peer review: Relationships between Free-Living #Protozoa, Cultivable #Legionella spp., and Water Quality Characteristics #yam

R.M. Valster, B.A. Wullings, R. van den Berg and D. van der Kooij recently published 'Relationships between Free-Living Protozoa, Cultivable Legionella spp., and Water Quality Characteristics in Three Drinking Water Supplies in the Caribbean' in: Applied and Environmental Microbiology, vol. 77 (2011) no.20, p.7321-7328.

           

Abstract

The study whose results are presented here aimed at identifying free-living protozoa (FLP) and conditions favoring the growth of these organisms and cultivable Legionella spp. in drinking water supplies in a tropical region. Treated and distributed water (±30°C) of the water supplies of three Caribbean islands were sampled and investigated with molecular techniques, based on the 18S rRNA gene. The protozoan host Hartmannella vermiformis and cultivable Legionella pneumophila were observed in all three supplies. Operational taxonomic units (OTUs) with the highest similarity to the potential or candidate hosts Acanthamoeba spp., Echinamoeba exundans, E. thermarum, and an Neoparamoeba sp. were detected as well. In total, 59 OTUs of FLP were identified. The estimated protozoan richness did not differ significantly between the three supplies. In supply CA-1, the concentration of H. vermiformis correlated with the concentration of Legionella spp. and clones related to Amoebozoa predominated (82%) in the protozoan community. These observations, the low turbidity (<0.2 nephelometric turbidity units [NTU]), and the varying ATP concentrations (1 to 12 ng liter–1) suggest that biofilms promoted protozoan growth in this supply. Ciliophora represented 25% of the protozoan OTUs in supply CA-2 with elevated ATP concentrations (maximum, 55 ng liter–1) correlating with turbidity (maximum, 62 NTU) caused by corroding iron pipes. Cercozoan types represented 70% of the protozoan clones in supply CA-3 with ATP concentrations of <1 ng liter–1 and turbidity of <0.5 NTU in most samples of distributed water. The absence of H. vermiformis in most samples from supply CA-3 suggests that growth of this protozoan is limited at ATP concentrations of <1 ng liter–1.

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researcher Patrick Smeets spoke at Canadian Water Network (CWN) QMRA project meeting (27-28 October 2011, Montreal-Laval, Canada) #yam

Pierre Payment (INRS-Institut Armand Frappier) is leading the CWN project on QMRA “Assessing waterborne health risks through quantitative risk assessment models”. The goal of the project is to address issues that have limited the use of QMRA in Canada. KWR was invited to give the Dutch and European perspective and experiences with QMRA, but also to learn from the results from the Canadian research so far.

Monica Emelko and Philip Schmidt (University of Waterloo) showed that the counts in microbial samples are not independent of the recovery of the method. Current QMRA models assume this independence which leads to a systematic bias that results in an overestimation of risk. Secondly they showed that uncertainty needs to be separated from variability in QMRA models in order to provide support for decision based on QMRA outcomes. Both these issues are relevant for the Dutch legislative QMRA of surface water supplies. 

Nathalie Tufjenki (McGill University) focused on pathogen removal by soil passage, providing important parameters for models that are used in risk assessment of ground water supplies. Unique assessment of the inactivation rate of microorganisms that are attached to soil particles shows that they die-off much faster than freely suspended organisms. Secondly she showed that attachment is not only dependent of ionic strength of the water, but also that pathogenic attach less easily than non-pathogenic strains of E. coli. This puts the use of E. coli as and indicator organism for all (pathogenic) bacteria under discussion for vulnerable groundwater sites.  

The CWN meeting shows that although the Dutch have extensive experience in QMRA, they can still learn from the Canadian research to improve their assessments. QMRA is still a young discipline in drinking water and international knowledge exchange through these projects is essential for all parties involved in supplying safe and healthy water.  

Finally Nick Ashbolt (USEPA) discussed the importance of Legionella as a waterborne health risk, as 29% of all water related infections are caused by this organism, and health consequences are often severe. Even though Legionella is mostly a problem of in-house plumbing and therefore not the responsibility of the water supplier, there is a moral obligation to use the expertise of the supplier to address this problem. This viewpoint links in very well with the recently started Dutch Health based investments project that assesses the best health return for investments in the water supply chain from catchment to consumer.

 

 

 

 

 

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KWR researcher Helena Sales Ortells talks on the Catalan Radio program 'Eureka' about Q fever

'Eureka!' is a Catalan radio program on the popularization of science. As part of the program, scientists living in other countries all around the world talk about fresh scientific, economic, social or cultural topics. Last week KWR researcher Helena Sales Ortells was interviewed about her research in The Netherlands.The interview was focused, in general, on the health risks people are exposed to (E.coli, Legionella, Cryptosporidium, Norovirus, etc.) through their contact with urban water systems. The last part of the interview was about the risk of Q fever through inhalation of shower aerosols proceeding from aerated groundwater. Helena will be interviewed in the program monthly, talking every time about a different topical (science-related) subject in The Netherlands.

Listen to Helena Sales Ortells here (from minute 13.30 to 19.05).

Maintaining the microbial quality in distribution systems and connected installations remains a challenge for water supply companies all over the world

On May 11-12 the conference Microbial Growth in Drinking Water Distribution Systems and Tap Water Installations is organized by KWR Watercycle Research Institute under the authority of the Dutch Joint Water Sector Research Programme, known as BTO. The regrowth issue is selected for this conference, because maintaining the microbial quality in distribution systems and connected installations remains a challenge for the water supply companies all over the world, despite many years of research. Exchange of information on this issue will be helpful in identifying the main concerns and knowledge gaps related to regrowth and stimulate cooperation in future research.

Topics of the conference include:

  • An overview of the regrowth issue in different countries;
  • Water quality problems related to regrowth;
  • Assessment and causes of regrowth in drinking water;
  • Prevention of regrowth by water treatment and distribution;
  • Research needs;
  • Technical programme: Visit to dune area and water treatment facility Heemskerk (PWN).

Invited speakers from Canada, Japan, USA, and European countries will present the latest information related to microbiological regrowth.

KWR-researchers Paul van der Wielen (editor) and Bart Wullings (photographer) will report from the conference in the next two days.

KWR peer reviewed: Concentration and Diversity of Uncultured Legionella spp. in Two Unchlorinated Drinking Water Supplies

Recentelijk publiceerden Wullings, B.A., Bakker, G. and van der Kooij, D. "Concentration and Diversity of Uncultured Legionella spp. in Two Unchlorinated Drinking Water Supplies with Different Concentrations of Natural Organic Matter" in: Applied and Environmental Microbiology 77(2011)2, p.634-641.


 

Abstract
Two unchlorinated drinking water supplies were investigated to assess the potential of water treatment and distribution systems to support the growth of Legionella spp. The treatment plant for supply A distributed treated groundwater with a low concentration (<0.5 ppm of C) of natural organic matter (NOM), and the treatment plant for supply B distributed treated groundwater with a high NOM concentration (8 ppm of C). In both supplies, the water temperature ranged from about 10°C after treatment to 18°C during distribution. The concentrations of Legionella spp. in distributed water, analyzed with quantitative PCR (Q-PCR), averaged 2.9 (± 1.9) × 10(2) cells liter(-1) in supply A and 2.5 (± 1.6) × 10(3) cells liter(-1) in supply B. No Legionella was observed with the culture method. A total of 346 clones (96 operational taxonomical units [OTUs] with ≥97% sequence similarity) were retrieved from water and biofilms of supply A and 251 (43 OTUs) from supply B. The estimation of the average value of total species richness (Chao1) in supply A (153) was clearly higher than that for supply B (58). In each supply, about 77% of the sequences showed <97% similarity to described species. Sequences related to L. pneumophila were only incidentally observed. The Legionella populations of the two supplies are divided into two distinct clusters based on distances in the phylogenetic tree as fractions of the branch length. Thus, a large variety of mostly yet-undescribed Legionella spp. proliferates in unchlorinated water supplies at temperatures below 18°C. The lowest concentration and greatest diversity were observed in the supply with the low NOM concentration.


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KWR peer reviewed: Detection of Protozoan Hosts for Legionella pneumophila in Engineered Water Systems by Using a Biofilm Batch Test

Recentelijk publiceerden Rinske M. Valster, Bart A. Wullings, and Dick van der Kooij in: APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Nov. 2010, p. 7144–7153.

Abstract
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KWR peer reviewed: Concentration and Diversity of Uncultured Legionella spp. in Two Unchlorinated Drinking Water Supplies with Different Concentrations of Natural Organic Matter

Recentelijk publiceerden Bart A. Wullings,Geo Bakker, and Dick van der Kooij in: APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Jan. 2011, p. 634–641.

Abstract

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