Assessment of microbial growth potential of PVC flexible tubing in contact with drinking water

2012 ◽  
Vol 12 (4) ◽  
pp. 489-495
Author(s):  
Z. G. Tsvetanova ◽  
E. J. Hoekstra
Keyword(s):  
Drinking Water ◽  
Microbial Growth ◽  
Immersion Test ◽  
Operating Conditions ◽  
Growth Potential ◽  
Contact Ratio ◽  
Contact Materials ◽  
Vending Machines ◽  
Tube Filling ◽  
Materials Used

Plasticized polyvinyl chloride (PVCp) tubes are commonly used to transport drinking water to public coffee vending machines, ice machines or water fountains. In contrast to pipe materials, the materials used beyond the consumer's tap are considered to be in contact with food and need to comply with the European Regulation for food contact materials; this, however, does not contain specific requirements about the enhancement of microbial growth. The aims of this study were to estimate microbial growth on PVCp tubes which were used to transport water to the types of machines noted above and to compare two methods of evaluating their net microbial growth potential. Four PVCp brands were tested for enhancement of microbial growth using a tube immersion test (the original Biomass Production Potential test) and a new tube filling test. Under field operating conditions, significant amounts of active biofilm accumulated on the PVCp-I tubes thereby impacting on water quality. In the laboratory test, the amount of biofilms on PVCp tubes and bacterial regrowth in the water depended on brand and were influenced by the surface-to-volume (S/V) contact ratio. To protect consumers' health, the microbial growth promoting potential of PVCp tubes should be taken into consideration when these products are in contact with drinking water.

The effect of the surface-to-volume contact ratio on the biomass production potential of the pipe products in contact with drinking water

2010 ◽  
Vol 10 (1) ◽  
pp. 105-112 ◽  
Author(s):  
Z. G. Tsvetanova ◽  
E. J. Hoekstra
Keyword(s):  
Drinking Water ◽  
Biomass Production ◽  
Microbial Growth ◽  
Biomass Concentration ◽  
Point Of View ◽  
Contact Ratio ◽  
Production Potential ◽  
Static Test ◽  
Growth Promoting ◽  
Construction Product

The biomass production potential (BPP) test is a semi-static test for assessment of microbial growth promoting properties of construction products in contact with drinking water (CPDW). In 2003 the test was selected for incorporation into a scheme for acceptance of CPDW in the framework of implementation of the European Construction Product Directive and Drinking Water Directive. The pass/fail criterion for the BPP test is based on the sum of microbial growth in water and in biofilm caused by substances released from CPDW. The test is performed at a surface-to-volume contact ratio (S/V) of 0.17 cm−1, that is quite different from the practice in buildings and domestic installations, where the usual ratios are 2.1 cm−1 for 3/4 inches pipe, 1.6 cm−1 for 1 inches pipe or 1.0 cm−1 for 1.5 inches pipe. The goal of the study was to evaluate the importance of S/V ratio for performance of the BPP test and for correct assessment of the growth promoting properties of CPDW. The BPP of 10 pipe products were compared under the S/V ratios of 0.17 cm−1 and 1.7 cm−1. The BPP of most polymer products were higher under the S/V ratio of 1.7 cm−1 in individual trials, but the differences were insignificant. However, the planktonic biomass concentrations were 4–14 fold higher at larger S/V ratio and this can be important from hygienic point of view. For acceptance of CPDW, besides a pass/fail criterion for the BPP, the planktonic biomass concentration could be taken as a second criterion for evaluation.

A study on assessment of biomass production potential of pipe materials in contact with drinking water

2009 ◽  
Vol 9 (4) ◽  
pp. 423-429 ◽  
Author(s):  
Z. G. Tsvetanova ◽  
E. J. Hoekstra
Keyword(s):  
Drinking Water ◽  
Biomass Production ◽  
Distribution Systems ◽  
Microbial Growth ◽  
Production Potential ◽  
Construction Products ◽  
Growth Promoting ◽  
Materials Used ◽  
Pipe Materials

The point of compliance in the European Drinking Water Directive is the consumer's tap and thus a set of requirements for the quality of materials used in distribution systems is needed. On European level an approval scheme for construction products in contact with drinking water is under development. The Regulators Group proposed that the Biomass Production Potential (BPP) test should be the basis for assessment of microbial growth support properties of products in contact with drinking water. Due to a lack of data the goal of this study was to generate more information on the growth promoting properties of pipe materials of different origin using the BPP test. The pipe materials under study showed different capacity to enhance bacterial growth and their BPP values could be ranked: Cu < SS < PP < PEx < PE < PVCp. A positive correlation between the planktonic biomass (PB) and the BPP was observed. Materials with a high BPP and a relatively higher PB/BPP ratio had a higher potential to impair bacteriological water quality. The option for derivation of pass-fail criteria based on planktonic biomass was discussed.

scholarly journals Primary ColonizingBetaproteobacterialesPlay a Key Role in the Growth ofLegionella pneumophilain Biofilms on Surfaces Exposed to Drinking Water Treated by Slow Sand Filtration

2018 ◽  
Vol 84 (24) ◽  
Author(s):  
Dick van der Kooij ◽  
Harm R. Veenendaal ◽  
Ronald Italiaander ◽  
Ed J. van der Mark ◽  
Marco Dignum
Keyword(s):  
Drinking Water ◽  
Biofilm Formation ◽  
Microbial Growth ◽  
Tap Water ◽  
Growth Potential ◽  
Sand Filtration ◽  
Slow Sand Filtration ◽  
Content Type ◽  
Premise Plumbing ◽  
Plumbing Systems

ABSTRACTSlow sand filtration with extensive pretreatment reduces the microbial growth potential of drinking water to a minimum level at four surface water supplies in The Netherlands. The potential of these slow sand filtrates (SSFs) to promote microbial growth in warm tap water installations was assessed by measuring biofilm formation and growth ofLegionellabacteria on glass and chlorinated polyvinylchloride (CPVC) surfaces exposed to SSFs at 37 ± 2°C in a model system for up to six months. The steady-state biofilm concentration ranged from 230 to 3,980 pg ATP cm−2on glass and 1.4 (±0.3)-times-higher levels on CPVC. These concentrations correlated significantly with the assimilable organic carbon (AOC) concentrations of the warm water (8 to 24 µg acetate-C equivalents [ac-C eq] liter−1), which were raised about 2 times by mixing cold and heated (70°C) SSFs. All biofilms supported growth ofLegionella pneumophilawith maximum concentrations ranging from 6 × 102to 1.5 × 105CFU cm−2. Biofilms after ≤50 days of exposure were predominated byBetaproteobacteriales, mainlyPiscinibacter,Caldimonas,Methyloversatilis, and an unculturedRhodocyclaceaebacterium. These rapidly growing primary colonizers most likely served as prey for the host amoebae ofL. pneumophila.Alphaproteobacteria, mostlyXanthobacteraceae, e.g.,Bradyrhizobium,Pseudorhodoplanes, and other amoeba-resistant bacteria, accounted for 37.5% of the clones retrieved. A conceptual model based on a quadratic relationship between theL. pneumophilacolony count and the biofilm concentration under steady-state conditions is used to explain the variations in theLegionellaCFU pg−1ATP ratios in the biofilms.IMPORTANCEProliferation ofL. pneumophilain 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 ofL. 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 ofL. pneumophilain premise plumbing systems. Still, reducing the concentration of biodegradable compounds in drinking water by appropriate water treatment is important for limiting theLegionellagrowth potential.

Nanofiltration of colored surface water: Quebec's experience

2003 ◽  
Vol 3 (5-6) ◽  
pp. 15-22
Author(s):  
P. Kouadio ◽  
M. Tétrault
Keyword(s):  
Drinking Water ◽  
Surface Water ◽  
Membrane Fouling ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Quebec City ◽  
Water Regulation ◽  
Eastern Canada

Three colored surface water nanofiltration pilot-scale projects were conducted in the province of Quebec (eastern Canada), between November 2000 and March 2002, by the company H2O Innovation (2000) inc., for the municipalities of Lac Bouchette, Latulipe-et-Gaboury and Charlesbourg (now part of Quebec City). Results indicated that nanofiltration permeate quality has an advance on present drinking water regulation standard in Quebec, but important membrane fouling occurred. Fouling can be controlled by pretreatment and optimization of the operating conditions.

scholarly journals The Role of Catalytic Ozonation Processes on the Elimination of DBPs and Their Precursors in Drinking Water Treatment

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 521
Author(s):  
Fernando J. Beltrán ◽  
Ana Rey ◽  
Olga Gimeno
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Humic Substances ◽  
Hypochlorous Acid ◽  
Drinking Water Treatment ◽  
Disinfection Byproducts ◽  
Catalytic Ozonation ◽  
Operating Conditions ◽  
Halogen Compounds ◽  
Radiation Sources

Formation of disinfection byproducts (DBPs) in drinking water treatment (DWT) as a result of pathogen removal has always been an issue of special attention in the preparation of safe water. DBPs are formed by the action of oxidant-disinfectant chemicals, mainly chlorine derivatives (chlorine, hypochlorous acid, chloramines, etc.), that react with natural organic matter (NOM), mainly humic substances. DBPs are usually refractory to oxidation, mainly due to the presence of halogen compounds so that advanced oxidation processes (AOPs) are a recommended option to deal with their removal. In this work, the application of catalytic ozonation processes (with and without the simultaneous presence of radiation), moderately recent AOPs, for the removal of humic substances (NOM), also called DBPs precursors, and DBPs themselves is reviewed. First, a short history about the use of disinfectants in DWT, DBPs formation discovery and alternative oxidants used is presented. Then, sections are dedicated to conventional AOPs applied to remove DBPs and their precursors to finalize with the description of principal research achievements found in the literature about application of catalytic ozonation processes. In this sense, aspects such as operating conditions, reactors used, radiation sources applied in their case, kinetics and mechanisms are reviewed.

scholarly journals Improving Blowout Performance of the Conical Swirler Combustor by Employing Two Parts of Fuel at Low Operating Condition

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1681
Author(s):  
Yixiang Yuan ◽  
Qinghua Zeng ◽  
Jun Yao ◽  
Yongjun Zhang ◽  
Mengmeng Zhao ◽  
...  
Keyword(s):  
Distribution Ratio ◽  
Performance Enhancement ◽  
Experimental Testing ◽  
Stability Boundary ◽  
Operating Conditions ◽  
Nox Emission ◽  
Combustion Stability ◽  
Gas Temperature ◽  
Contact Ratio ◽  
Fuel Distribution

Aiming at the problem of the narrow combustion stability boundary, a conical swirler was designed and constructed based on the concept of fuel distribution. The blowout performance was studied at specified low operating conditions by a combination of experimental testing and numerical simulations. Research results indicate that the technique of the fuel distribution can enhance the combustion stability and widen the boundary of flameout within the range of testing conditions. The increase of the fuel distribution ratio improves the combustion stability but leads to an increase in NOx emission simultaneously. The simulation results show the increase of the fuel distribution ratio causes contact ratio increase in the area of lower reference velocity and gas temperature increase. The increased contact ratio and temperature contribute to the blowout performance enhancement, which is identical to the analysis result of the Damkohler number. The reported work in this paper has potential application value for the development of an industrial burner and combustor with high stability and low NOx emission, especially when the combustion system is required to be stable and efficient at low working conditions.

scholarly journals Analysis and Comparative Assessment of Basic Tribological Properties of Selected Polymer Composites

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 75 ◽  
Author(s):  
Jerzy Jozwik ◽  
Krzysztof Dziedzic ◽  
Marcin Barszcz ◽  
Mykhaylo Pashechko
Keyword(s):  
Polymer Composites ◽  
Friction Force ◽  
Tribological Properties ◽  
Friction Pair ◽  
Computer Software ◽  
Operating Conditions ◽  
The Coefficient Of Friction ◽  
Cast Polyamide ◽  
Friction Path ◽  
Materials Used

Phenomena occurring in the contact area between two mating bodies are characterised by high complexity and variability. Comparisons are usually made between parameters such as the coefficient of friction, friction force, wear and temperature in relation to time and friction path. Their correct measurement enables the proper evaluation of tribological properties of materials used in the friction pair. This paper concerns the measurements of basic tribological parameters in the friction of selected polymer composites. Knowing the tribological properties of these composite materials, it will be possible to create proper operating conditions for kinematic friction pairs. This study investigated the coefficients of friction, friction force and temperatures of six polymer composites: cast polyamide PA6 G with oil, PA6 G with MoS2, polyoxymethylene POM with aluminium, polyethylene terephthalate PET with polytetrafluoroethylene PTFE, PTFE with bronze, and PTFE with graphite. The friction surface was also examined using an optical system and computer software for 3D measurements. As a result, PA6-G with oil was found to be the best choice as a composite material for thin sliding coatings.

scholarly journals Biofilm forming ability of Sphingomonas paucimobilis isolated from community drinking water systems on plumbing materials used in water distribution

2017 ◽  
Vol 15 (6) ◽  
pp. 942-954 ◽  
Author(s):  
Parul Gulati ◽  
Moushumi Ghosh
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Biofilm Formation ◽  
Water Distribution ◽  
Sem Analysis ◽  
Sphingomonas Paucimobilis ◽  
Simulated Distribution ◽  
Flow Through ◽  
Materials Used ◽  
Biofilm Development

Sphingomonas paucimobilis, an oligotroph, is well recognized for its potential for biofilm formation. The present study explored the biofilm forming ability of a strain isolated from municipal drinking water on plumbing materials. The intensity of biofilm formation of this strain on different plumbing materials was examined by using 1 × 1 cm2 pieces of six different pipe materials, i.e. polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), aluminium (Al), copper (Cu) and rubber (R) and observing by staining with the chemical chromophore, Calcofluor. To understand whether biofilm formation occurs under flow through conditions, a laboratory-scale simulated distribution system, comprised of the above materials was fabricated. Biofilm samples were collected from the designed system at different biofilm ages (10, 40 and 90 hours old) and enumerated. The results indicated that the biofilm formation occurred on all plumbing materials with Cu and R as exceptions. The intensity of biofilm formation was found to be maximum on PVC followed by PP and PE. We also demonstrated the chemical chromophore (Calcofluor) successfully for rapid and easy visual detection of biofilms, validated by scanning electron microscope (SEM) analysis of the plumbing materials. Chlorination has little effect in preventing biofilm development.

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