Papers by Dick van der Kooij
Effect of water composition, distance and season on the adenosine triphosphate concentration in unchlorinated drinking water in the Netherlands
Water Research, 2010
The objective of our study was to determine whether water composition, distance to the treatment ... more The objective of our study was to determine whether water composition, distance to the treatment plant and season significantly affect the adenosine triphosphate (ATP) concentration in distributed drinking water, in order to resolve the suitability of ATP as an indicator parameter for microbial regrowth. Results demonstrated that the ATP concentration in distributed water averaged between 0.8 and 12.1 ng ATP L(-1) in the Netherlands. Treatment plants with elevated biofilm formation rates in treated water, showed significantly higher ATP concentrations in distributed drinking water and ATP content was significantly higher in the summer/autumn compared to the winter period at these plants. Furthermore, transport of drinking water in a large-sized distribution system resulted in significantly lower ATP concentrations in water from the distal than the proximal part of the distribution system. Finally, modifications in the treatment significantly affected ATP concentrations in the distributed drinking water. Overall, the results from our study demonstrate that ATP is a suitable indicator parameter to easily, rapidly and quantitatively determine the total microbial activity in distributed drinking water.
Spores of sulphite-reducing clostridia (SSRC) as surrogate for verification of the inactivation capacity of full-scale ozonation for Cryptosporidium
Water Supply
The inactivation of C. parvum and spores of Cl. perfringens by ozone treatment in natural water i... more The inactivation of C. parvum and spores of Cl. perfringens by ozone treatment in natural water in a lab-scale continuous-flow system was compared. In addition the inactivation of the natural occurring spores of sulphite-reducing clostridia (SSRC) in this water was monitored in one of the lab-scale systems as well as in a full-scale ozonation process. The survival ratio of C. parvum oocysts was determined using the CD-1 neonatal mouse infectivity test and for Cl. perfringens and SSRC the survival ratio was assessed with the standard anaerobic colony count on the iron-sulphite medium. The results of the lab-scale experiments revealed an inactivation rate constant k (Chick-Watson modelling) at 10°C for C. parvum of 0.14 (SD=0.014; P<0.001) and for Cl. perfringens of 0.25 (SD=0.01; P<0.001). Moreover, first results of monitoring the SSRC inactivation in full-scale ozonation processes indicated that the inactivation rate constant for these wild strains was in the same order of mag...
Quantitative assessment of the removal of indicator bacteria in full-scale treatment plants (THESIS VERSION)
The elimination of thermotolerant coliforms (Coli44) and spores of sulphite-reducing clostridia (... more The elimination of thermotolerant coliforms (Coli44) and spores of sulphite-reducing clostridia (SSRC) in full-scale water treatment was determined by large volume sampling. The objective was to determine the elimination capacity of full-scale treatment processes for micro-organisms, both vegetative bacteria and bacterial spores. In two short-periods in winter and summer, information was collected about the elimination of Coli44 and SSRC by the overall treatment, the contribution of the unit processes and the variability in elimination. Coli44 concentrations in the source waters were reduced by 3.2 to 6.3 log to an average concentration sufficiently low to achieve more than 99% compliance with the drinking water standard. The elimination of SSRC was lower (1.4 to 4.2) and SSRC were observed occasionally (>1%) in finished water by the routine weekly sampling of 100 ml samples. The study also yielded much information about the elimination efficacy of unit processes at the different...
Elucidation of membrane biofouling processes using bioassays for assessing the microbial growth potential of feed water
Applied and Environmental Microbiology, 2009
The ammonia-oxidizing prokaryote (AOP) community in three groundwater treatment plants and connec... more The ammonia-oxidizing prokaryote (AOP) community in three groundwater treatment plants and connected distribution systems was analyzed by quantitative real-time PCR and sequence analysis targeting the amoA gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Results demonstrated that AOB and AOA numbers increased during biological filtration of ammonia-rich anoxic groundwater, and AOP were responsible for ammonium removal during treatment. In one of the treatment trains at plant C, ammonia removal correlated significantly with AOA numbers but not with AOB numbers. Thus, AOA were responsible for ammonia removal in water treatment at one of the studied plants. Furthermore, an observed negative correlation between the dissolved organic carbon (DOC) concentration in the water and AOA numbers suggests that high DOC levels might reduce growth of AOA. AOP entered the distribution system in numbers ranging from 1.5 × 10 3 to 6.5 × 10 4 AOPs ml −1 . These numbers did not change during...
Applied and Environmental Microbiology, 2009
Free-living protozoan communities in water supplies may include hosts for Legionella pneumophila ... more Free-living protozoan communities in water supplies may include hosts for Legionella pneumophila and other undesired bacteria, as well as pathogens. This study aimed at identifying free-living protozoa in two unchlorinated groundwater supplies, using cultivation-independent molecular approaches. For this purpose, samples (<20°C) of treated water, distributed water, and distribution system biofilms were collected from supply A, with a low concentration of natural organic matter (NOM) (<0.5 ppm of C), and from supply B, with a high NOM concentration (7.9 ppm of C). Eukaryotic communities were studied using terminal restriction fragment length polymorphism and clone library analyses of partial 18S rRNA gene fragments and a Hartmannella vermiformis -specific quantitative PCR (qPCR). In both supplies, highly diverse eukaryotic communities were observed, including free-living protozoa, fungi, and metazoa. Sequences of protozoa clustered with Amoebozoa (10 operational taxonomic units...
Applied and Environmental Microbiology, 2018
Proliferation of L. pneumophila in premise plumbing poses a public health threat. Extended water ... more Proliferation of L. pneumophila in premise plumbing poses a public health threat. Extended water treatment using physicochemical and biofiltration processes, including slow sand filtration, at four surface water supplies in The Netherlands reduces the microbial growth potential of the treated water to a minimum level, and the distributed drinking water complies with high quality standards. However, heating of the water in warm tap water installations increases the concentration of easily assimilable organic compounds, thereby promoting biofilm formation and growth of L. pneumophila . Prevention of biofilm formation in plumbing systems by maintenance of a disinfectant residual during distribution and/or further natural organic matter (NOM) removal is not feasible in the supplies studied. Temperature management in combination with optimized hydraulics and material selection are therefore essential to prevent growth of L. pneumophila in premise plumbing systems. Still, reducing the con...
Applied and environmental microbiology, Jan 15, 2016
Legionella pneumophila proliferates in freshwater environments at temperatures ranging from 25 to... more Legionella pneumophila proliferates in freshwater environments at temperatures ranging from 25 to 45°C. To investigate the preference of different sequence types (ST) for a specific temperature range, growth of L. pneumophila serogroup 1 (SG1) ST1 (environmental strains), ST47, and ST62 (disease-associated strains) was measured in buffered yeast extract broth (BYEB) and biofilms grown on plasticized polyvinyl chloride in flowing heated drinking water originating from a groundwater supply. The optimum growth temperatures in BYEB were approximately 37°C (ST1), 39°C (ST47), and 41°C (ST62), with maximum growth temperatures of 42°C (ST1) and 43°C (ST47 and ST62). In the biofilm at 38°C, the ST47 and ST62 strains multiplied equally well compared to growth of the environmental ST1 strain and an indigenous L. pneumophila non-SG1 strain, all attaining a concentration of approximately 10CFU/cmRaising the temperature to 41°C did not impact these levels within 4 weeks, but the colony counts of...
Applied and environmental microbiology, 2017
Citation van der Kooij D, Brouwer-Hanzens AJ, Veenendaal HR, Wullings BA. 2017. Erratum for van d... more Citation van der Kooij D, Brouwer-Hanzens AJ, Veenendaal HR, Wullings BA. 2017. Erratum for van der Kooij et al., Multiplication of Legionella pneumophila sequence types 1, 47, and 62 in buffered yeast extract broth and biofilms exposed to flowing tap water at temperatures of 38°C to 42°C. Appl Environ Microbiol 83: e03036-16.
Applied and Environmental Microbiology, 2017
Legionella pneumophila in potable water installations poses a potential health risk, but quantita... more Legionella pneumophila in potable water installations poses a potential health risk, but quantitative information about its replication in biofilms in relation to water quality is scarce. Therefore, biofilm formation on the surfaces of glass and chlorinated polyvinyl chloride (CPVC) in contact with tap water at 34 to 39°C was investigated under controlled hydraulic conditions in a model system inoculated with biofilm-grown L. pneumophila . The biofilm on glass (average steady-state concentration, 23 ± 9 pg ATP cm −2 ) exposed to treated aerobic groundwater (0.3 mg C liter −1 ; 1 μg assimilable organic carbon [AOC] liter −1 ) did not support growth of the organism, which also disappeared from the biofilm on CPVC (49 ± 9 pg ATP cm −2 ) after initial growth. L. pneumophila attained a level of 4.3 log CFU cm −2 in the biofilms on glass (1,055 ± 225 pg ATP cm −2 ) and CPVC (2,755 ± 460 pg ATP cm −2 ) exposed to treated anaerobic groundwater (7.9 mg C liter −1 ; 10 μg AOC liter −1 ). An e...
Water Research, 2005
Legionella pneumophila was grown in a model warm water system with pipes of copper (Cu), stainles... more Legionella pneumophila was grown in a model warm water system with pipes of copper (Cu), stainless steel (SS) and cross-linked polyethylene (PEX) during recirculation of tap water at 25-35 1C. Subsequently, domestic use of warm (37 1C) water was simulated using tap water with a low AOC concentration (o10 mg C/L). Two times each week the temperature of the water in the electric heaters (not in the pipes) was elevated to 70 1C for 30 min. ATP concentrations in the water sampled from the pipes over a 2-year period were significantly different for the pipe materials, with median values of 2.1 ng/l (Cu), 2.5 ng/l (SS) and 4.5 ng/l (PEX), respectively. Median values of the biofilm concentration were similar on Cu and SS (about 630 pg ATP/cm 2) and 1870 pg ATP/cm 2 on PEX. Legionella multiplied in these biofilms and median values of Legionella concentrations in water were 1500 CFU/l (Cu) and about 4300 CFU/l for SS and PEX. Legionella to ATP ratios in water had median values of about 0.8 CFU/pg. Hot water flushing (70 1C) of the pipes on day 552, followed by 2 weeks of recirculation at 37 1C, caused strongly increased concentrations of ATP (up to 300 ng/l) and Legionella (410 7 CFU/l), with about 100 CFU/pg ATP. Concentrations declined to original levels within 1 week of domestic water use, etc. Legionella concentrations in water and biofilms were at the same levels for all materials after 2 years. Hence, copper temporarily limited the growth of Legionella under the applied conditions and a rapid biomass development strongly increased the Legionella to ATP ratio.
Biofouling potential of chemicals used for scale control in RO and NF membranes
Desalination, 2000
The potential of 14 different antiscalants (AS) to promote biofouling was determined with the eas... more The potential of 14 different antiscalants (AS) to promote biofouling was determined with the easily assimilable organic carbon (AOC) test and the Biomass Production Potential (BPP) test, respectively. The AOC concentrations of slow sand filtrate supplemented with 50 mg/l of AS ranged from 4 to 112 μg of C/l, and maximum concentrations of adenosinetriphosphate (ATP) from 7 to 380 ng/l,
Applied and Environmental Microbiology, 2011
The study whose results are presented here aimed at identifying free-living protozoa (FLP) and co... more 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 predomina...
Applied and Environmental Microbiology, 2004
The need for protozoa for the proliferation of Legionella pneumophila in aquatic habitats is stil... more The need for protozoa for the proliferation of Legionella pneumophila in aquatic habitats is still not fully understood and is even questioned by some investigators. This study shows the in vivo growth of L. pneumophila in protozoa in aquatic biofilms developing at high concentrations on plasticized polyvinyl chloride in a batch system with autoclaved tap water. The inoculum, a mixed microbial community including indigenous L. pneumophila originating from a tap water system, was added in an unfiltered as well as filtered (cellulose nitrate, 3.0-μm pore size) state. Both the attached and suspended biomasses were examined for their total amounts of ATP, for culturable L. pneumophila , and for their concentrations of protozoa. L. pneumophila grew to high numbers (6.3 log CFU/cm 2 ) only in flasks with an unfiltered inoculum. Filtration obviously removed the growth-supporting factor, but it did not affect biofilm formation, as determined by measuring ATP. Cultivation, direct counting, a...
Applied and Environmental Microbiology, 2006
A real-time PCR-based method targeting the 18S rRNA gene was developed for the quantitative detec... more A real-time PCR-based method targeting the 18S rRNA gene was developed for the quantitative detection of Hartmannella vermiformis , a free-living amoeba which is a potential host for Legionella pneumophila in warm water systems and cooling towers. The detection specificity was validated using genomic DNA of the closely related amoeba Hartmannella abertawensis as a negative control and sequence analysis of amplified products from environmental samples. Real-time PCR detection of serially diluted DNA extracted from H. vermiformis was linear for microscopic cell counts between 1.14 × 10 −1 and 1.14 × 10 4 cells per PCR. The genome of H. vermiformis harbors multiple copies of the 18S rRNA gene, and an average number (with standard error) of 1,330 ± 127 copies per cell was derived from real-time PCR calibration curves for cell suspensions and plasmid DNA. No significant differences were observed between the 18S rRNA gene copy numbers for trophozoites and cysts of strain ATCC 50237 or bet...
Applied and Environmental Microbiology, 2006
Representatives of the genus Legionella were detected by use of a real-time PCR method in all wat... more Representatives of the genus Legionella were detected by use of a real-time PCR method in all water samples collected directly after treatment from 16 surface water (SW) supplies prior to postdisinfection and from 81 groundwater (GW) supplies. Legionella concentrations ranged from 1.1 × 10 3 to 7.8 × 10 5 cells liter −1 and were significantly higher in SW treated with multiple barriers at 4°C than in GW treated at 9 to 12°C with aeration and filtration but without chemical disinfection. No Legionellae (<50 CFU liter −1 ) were detected in treated water by the culture method. Legionella was also observed in untreated SW and in untreated aerobic and anaerobic GW. Filtration processes in SW and GW treatment had little effect or increased the Legionella concentration, but ozonation in SW treatment caused about 1-log-unit reduction. A phylogenetic analysis of 16S rRNA gene sequences of 202 clones, obtained from a selection of samples, showed a high similarity (>91%) with Legionella ...
Applied and Environmental Microbiology, 2010
Two unchlorinated drinking water supplies were investigated to assess the potential of water trea... more 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...
Applied and Environmental Microbiology, 2010
Legionella pneumophila proliferates in aquatic habitats within free-living protozoa, 17 species o... more Legionella pneumophila proliferates in aquatic habitats within free-living protozoa, 17 species of which have been identified as hosts by using in vitro experiments. The present study aimed at identifying protozoan hosts for L. pneumophila by using a biofilm batch test (BBT). Samples (600 ml) collected from 21 engineered freshwater systems, with added polyethylene cylinders to promote biofilm formation, were inoculated with L. pneumophila and subsequently incubated at 37°C for 20 days. Growth of L. pneumophila was observed in 16 of 18 water types when the host protozoan Hartmannella vermiformis was added. Twelve of the tested water types supported growth of L. pneumophila or indigenous Legionella anisa without added H. vermiformis . In 12 of 19 BBT flasks H. vermiformis was indicated as a host, based on the ratio between maximum concentrations of L. pneumophila and H. vermiformis , determined with quantitative PCR (Q-PCR), and the composition of clone libraries of partial 18S rRNA g...
Applied and Environmental Microbiology, 2014
Biopolymers are important substrates for heterotrophic bacteria in (ultra)oligotrophic freshwater... more Biopolymers are important substrates for heterotrophic bacteria in (ultra)oligotrophic freshwater environments, but information about their utilization at microgram-per-liter levels by attached freshwater bacteria is lacking. This study aimed at characterizing biopolymer utilization in drinking-water-related biofilms by exposing such biofilms to added carbohydrates or proteins at 10 μg C liter −1 in flowing tap water for up to 3 months. Individually added amylopectin was not utilized by the biofilms, whereas laminarin, gelatin, and caseinate were. Amylopectin was utilized during steady-state biofilm growth with simultaneously added maltose but not with simultaneously added acetate. Biofilm formation rates (BFR) at 10 μg C liter −1 per substrate were ranked as follows, from lowest to highest: blank or amylopectin (≤6 pg ATP cm −2 day −1 ), gelatin or caseinate, laminarin, maltose, acetate alone or acetate plus amylopectin, and maltose plus amylopectin (980 pg ATP cm −2 day −1 ). Term...
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Papers by Dick van der Kooij