Efficiency of Microfiltration Systems for the Removal of Bacterial and Viral Contaminants from Surface and Rainwater

Dobrowsky, P. H.; Lombard, Melissa A.; Cloete, William J.; Saayman, Michael J.; Cloete, T.E.; Carstens, Machteld E.; Khan, S. Ajmal; Khan, Wesaal

doi:10.1007/s11270-015-2317-6

Cited by 40 publications

(14 citation statements)

References 54 publications

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“…Li et al (2014) found that copper-zeolite filter media could reach a high removal efficiency of bacteria in rainwater, and the copper leaching was 9 μg/L. Dobrowsky et al (2015) evaluated the efficiency of microfiltration systems for the treatment of harvested rainwater. Results showed a good removal performance of heterotrophic bacteria and coliform, but viruses and adenovirus were not effectively removed by the filtration system.…”

Section: Introductionmentioning

confidence: 99%

A low pressure gravity-driven membrane filtration (GDM) system for rainwater recycling: Flux stabilization and removal performance

et al. 2017

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Rainwater is a nature resource, which can be widely used for non-potable and potable applications in water scared countries after appropriate treatment. Gravity-driven membrane filtration (GDM) process is a promising technology for decentralized rainwater treatment due to no backwashing, flushing and chemical cleaning. In this study, we established a single lab-scale GDM system for the stored rainwater (simulative cellar rainwater) treatment with two months operation, and a stored tap water was used as a compared system to evaluate the permeability and organics removal performance. Results showed that GDM exhibited a good performance for bacteria and turbidity removals, but the removal performance of DOC was undesirable due to the low rejection of low molecular-weight fulvic. Additionally, the permeate flux reached stable with the value of 6-6.5 L/mh during 60 days operation in the rainwater system, however, the tap water system stabilized only at 4 L/mh. Hydraulically reversible resistance accounted for large proportions (90%) of the total resistance, which indicated that the flux could be recovered by simple physical flushing. The bio-fouling layer adhered on the membrane surface was characterized at the end of the filtration experiment. Higher bio-activity with lower EPS (polysaccharides and proteins) contents of the fouling layer were found in the rainwater system compared with the control system, which was the main reason for the higher flux. These results show that rainwater can be treated in a single GDM process with low maintenance, which makes the process suitable for decentralized water supply.

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Section: Introductionmentioning

confidence: 99%

A low pressure gravity-driven membrane filtration (GDM) system for rainwater recycling: Flux stabilization and removal performance

et al. 2017

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“…For the detection and quantification of Legionella spp., Acanthamoeba spp., N. fowleri and V. vermiformis total gDNA was extracted from pasteurized (68 °C, 74 °C, 84 °C, 93 °C) and the corresponding unpasteurized tank water samples. For this, 1 l of each sample was first subjected to flocculation as previously described by Dobrowsky et al [ 54 ]. Briefly, 2 ml of CaCl 2 (1 M) and 2 ml of Na 2 HPO 4 (1 M) were added to each sample before the samples were stirred (room temperature) for 5 min.…”

Section: Methodsmentioning

confidence: 99%

Molecular detection of Acanthamoeba spp., Naegleria fowleri and Vermamoeba (Hartmannella) vermiformis as vectors for Legionella spp. in untreated and solar pasteurized harvested rainwater

et al. 2016

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Background Legionella spp. employ multiple strategies to adapt to stressful environments including the proliferation in protective biofilms and the ability to form associations with free-living amoeba (FLA). The aim of the current study was to identify Legionella spp., Acanthamoeba spp., Vermamoeba (Hartmannella) vermiformis and Naegleria fowleri that persist in a harvested rainwater and solar pasteurization treatment system.MethodsPasteurized (45 °C, 65 °C, 68 °C, 74 °C, 84 °C and 93 °C) and unpasteurized tank water samples were screened for Legionella spp. and the heterotrophic plate count was enumerated. Additionally, ethidium monoazide quantitative polymerase chain reaction (EMA-qPCR) was utilized for the quantification of viable Legionella spp., Acanthamoeba spp., V. vermiformis and N. fowleri in pasteurized (68 °C, 74 °C, 84 °C and 93 °C) and unpasteurized tank water samples, respectively.ResultsOf the 82 Legionella spp. isolated from unpasteurized tank water samples, Legionella longbeachae (35 %) was the most frequently isolated, followed by Legionella norrlandica (27 %) and Legionella rowbothamii (4 %). Additionally, a positive correlation was recorded between the heterotrophic plate count vs. the number of Legionella spp. detected (ρ = 0.710, P = 0.048) and the heterotrophic plate count vs. the number of Legionella spp. isolated (ρ = 0.779, P = 0.0028) from the tank water samples collected. Solar pasteurization was effective in reducing the gene copies of viable V. vermiformis (3-log) and N. fowleri (5-log) to below the lower limit of detection at temperatures of 68–93 °C and 74–93 °C, respectively. Conversely, while the gene copies of viable Legionella and Acanthamoeba were significantly reduced by 2-logs (P = 0.0024) and 1-log (P = 0.0015) overall, respectively, both organisms were still detected after pasteurization at 93 °C.ConclusionsResults from this study indicate that Acanthamoeba spp. primarily acts as the vector and aids in the survival of Legionella spp. in the solar pasteurized rainwater as both organisms were detected and were viable at high temperatures (68–93 °C).

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“…Samples (2 L) were taken aseptically from each of the five heaters in sterile screw-top glass bottles from cold water taps 3 min after opening (CT), hot water taps directly after opening whilst water is still cold (HT1) and hot water taps after running at maximum heat for 1 min (HT2). Water was transported immediately to the laboratory and processed within 1 h. Microbial cells in the samples were concentrated by filtration (2 L) and released from the filters into suspension by incubation in an acidic buffer according to Dobrowsky et al (2015). The samples were flocculated by the addition of 2 mL/L CaCl 2 (1M) and 2 mL/L Na 2 HPO 4 (1M) and subsequent stirring (5 min).…”

Section: Distribution System Sampling and Molecular Quantificationmentioning

confidence: 99%

A potential source of undiagnosed Legionellosis: Legionella growth in domestic water heating systems in South Africa

Stone

Louw

Gakingo

et al. 2019

Energy for Sustainable Development

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Legionella is a genus of pathogenic bacterial mesophiles that cause a range of diseases collectively referred to as Legionellosis, with immunocompromised individuals being particularly susceptible. Water heaters, a potential domestic niche for these pathogens, are heavy energy consumers, causing cost-sensitive users to employ energy-saving initiatives, such as scheduling and lower temperature set points. However, lower heated water temperatures allow Legionella to flourish. This paper uses computational fluid dynamics modelling to show that the pipes downstream of a horizontal electric water heater provide an environment that is conducive to Legionella growth, not the heater itself. The presence of Legionella in water heaters is established through water sampled from five in-field water heaters, of which the temperatures and heating schedules are known. Microbiological techniques (PCR and weight-based qRT-PCR) are used to assess Legionella and L. pneumophila presence at point-of-use taps. A model is used to determine the potential infection rate from these concentrations, demonstrating that undiagnosed Legionellosis infection is likely. In low-and middleincome countries, like South Africa, misdiagnosis of Legionellosis may be common due to the shadow cast by HIV and TB prevalence.

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Efficiency of Microfiltration Systems for the Removal of Bacterial and Viral Contaminants from Surface and Rainwater

Cited by 40 publications

References 54 publications

A low pressure gravity-driven membrane filtration (GDM) system for rainwater recycling: Flux stabilization and removal performance

A low pressure gravity-driven membrane filtration (GDM) system for rainwater recycling: Flux stabilization and removal performance

Molecular detection of Acanthamoeba spp., Naegleria fowleri and Vermamoeba (Hartmannella) vermiformis as vectors for Legionella spp. in untreated and solar pasteurized harvested rainwater

A potential source of undiagnosed Legionellosis: Legionella growth in domestic water heating systems in South Africa

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