Hot Water Distribution Research Articles

Long-Term Effects of Hospital Water Network Disinfection onLegionellaand Other Waterborne Bacteria in an Italian University Hospital

Legionella control still remains a critical issue in healthcare settings where the preferred approach to health risk assessment and management is to develop a water safety plan. We report the experience of a university hospital, where a water safety plan has been applied since 2002, and the results obtained with the application of different methods for disinfecting hot water distribution systems in order to provide guidance for the management of water risk. The disinfection procedures included continuous chlorination with chlorine dioxide (0.4-0.6 mg/L in recirculation loops) reinforced by endpoint filtration in critical areas and a water treatment based on monochloramine (2-3 mg/L). Real-time polymerase chain reaction and a new immunoseparation and adenosine triphosphate bioluminescence analysis were applied in environmental monitoring. After 9 years, the integrated disinfection-filtration strategy significantly reduced positive sites by 55% and the mean count by 78% (P < .05); however, the high costs and the occurrence of a chlorine-tolerant clone belonging to Legionella pneumophila ST269 prompted us to test a new disinfectant. The shift to monochloramine allowed us to eliminate planktonic Legionella and did not require additional endpoint filtration; however, nontuberculous mycobacteria were isolated more frequently as long as the monochloramine concentration was 2 mg/L; their cultivability was never regained by increasing the concentration up to 3 mg/L. Any disinfection method needs to be adjusted/fine-tuned in individual hospitals in order to maintain satisfactory results over time, and only a locally adapted evidence-based approach allows assessment of the efficacy and disadvantages of the control measures.

Hot Water Temperature Drop in a Pipe as a Parameter in Order to Define Operation Time of a Circulation Loop in Domestic Hot Water Distribution System

The content of this submission is to define the operation time of a hot water circulation loop in term of the hot water temperature drop in a time depending on several factors. Type and diameter of a pipe, thickness of a thermal pipe insulation, location of distribution pipes and ambient temperature around the pipes belong among these significant factors. All these parameters and others are used in the analytic calculation of the hot water temperature drop in a time according to the standard STN EN 15316-3-2. So we can use the calculated time of hot water temperature drop in order to define time intervals of the water circulation in hot water distribution pipes. The aim of this submission is to determine heat losses from hot water distribution pipes and calculate the electric energy consumption of the circulation pump for this design state. The study results are demonstrated on the model object of a multi-dwelling house.

Profile-Based Control for Central Domestic Hot Water Distribution

A main goal of hot water distribution research is to improve the system's efficiency, i.e., to fulfill hot water requirements while minimizing energy and water losses. Central domestic hot water (CDHW) systems represent an important part of current installations worldwide, e.g., hotels, hospitals, sports centers, social facilities, and multifamily residential or apartment buildings. The optimization of such systems claims for forecasting capabilities and context-aware enhancements are based on patterns of use. Thus, the level of uncertainty is reduced, and systems are not forced to operate using blind/oversized/generic assumptions. This paper presents a novel control strategy based on habit profiles for the management of a CDHW system. A simulated environment is utilized to compare the introduced strategy with habitual performances. Simulations are supported by real databases concerning users' behavioral patterns. Results are promising and point to place profile-based strategies as a suitable approach for an optimized water and energy management in future buildings.

Legionella contamination in hospitals of the Campania Region: five years of environmental surveillance results.

The purpose of this study was to assess the presence and the distribution of Legionella serotypes in 50 hospital facilities in the Campania Region (Italy) through the sampling of their waters. From January 2008 to December 2012, in compliance with the Italian Monitoring Guidelines for Legionellosis, 4.842 water samples were collected from the end points of hot water distribution networks, air conditioning systems, boilers and cooling towers. 1.426 (29.4%) of the 4.842 samples resulted positive for Legionella spp, with a bacterial average of 3.40 log10 cfu/L. The frequency of Legionella isolation in the specimens progressively decreased during the study (43.8% in 2008 vs 22.9% in 2012). Samples from cooling towers (32.7%), showers and taps (31.9%) revealed a more frequent presence of the microorganism, although considerable bacterial concentration variability was found in all examined points. A bacterial average of 3.33 + 0.88 log10 cfu/L was detected in cooling towers, whereas the lowest values (2.89 + 0.92 cfu/L) were found in ACSs. The most frequently isolated species were L. pneumophila 2-14, detected in 60.6% of positive samples. Within serotypes, types 6 (23.8%), 8 (21.9%) and 3 (21.4%) resulted as being the most representative. A significant contamination was found in examined centers. It is therefore advisable to systematically implement currently available surveillance and monitoring strategies through the scrupulous monitoring of systems as well as through the application of validated and effective procedures.

Solar thermal systems for high rise buildings with high consumption demand: Case study for a 5 star hotel in Sao Paulo, Brazil

Solar thermal has been consolidated as a renewable energy solution for new buildings during recent years. Although this system has been easily integrated in low-rise buildings, a continuous challenge is the integration of solar thermal into the demanding architectural solutions for high-rise buildings. This article presents solutions for solar water installations in high rise buildings. It describes the integration of solar collectors into the building, hot water distribution installation and proposes a solution to minimise the risk of exposure to Legionella. As an example of the requirements of solar thermal in developing countries, the article analyses the development of the solar hot water standards in Brazil, where although there is a draft document for a federal standard, cities like Sao Paulo have already in place solar thermal requirements for any new building in the city. In order to promote the development of renewable integration, initiatives like PROCEL certify buildings energy performance if they meet the improved target, compared to regulatory requirements, of generating a minimum of 60% of hot water using solar thermal. The presented case study for a 5 star hotel clearly justifies the installation of solar thermal systems in buildings with a high demand for hot water.

Energy Analysis of Hot Water Distribution System - Interrupted Operation

At an actual increase energy price it is has impact cut-down energy requirement for preparation and distribution of hot water (HW). In the paper are presented results of exploration, where been evaluation effect interrupted operations distribution systems HW flat building. From presented analyses result - relative more savings heat is for long interrupted distribution systems and for little the number of flat in building.

Monochloramine and chlorine dioxide for controlling Legionella pneumophila contamination: biocide levels and disinfection by-product formation in hospital water networks

Legionella colonization in hospital hot water distribution networks was evaluated following 36 months of continuous treatment with monochloramine and compared with chlorine dioxide. Nitrite, nitrate, chlorite, chlorate, bromide, trihalomethanes and haloacetic acids as well as the biocide concentration at sampled points were measured. Only 8/84 samples treated with monochloramine were found contaminated and after the first 8 months of treatment no Legionella was isolated. Chlorine dioxide was associated with a strong reduction in Legionella contamination compared to pre-treatment, but differences according to the device were observed. Monochloramine between 2 and 3 mg l(-1) and chlorine dioxide between 0.50 and 0.70 mg l(-1) were needed to control Legionella colonization. Comparing no- and post-flush samples, a higher frequency of no-flush positive samples was noted using chlorine dioxide, suggesting an increased risk for patients when they open the tap. No increase in chlorite levels and no water nitrification occurred by using monochloramine. Chlorite at levels exceeding the limit requested for drinking water was measured when chlorine dioxide was applied. In conclusion, we highlight that continuous injection of monochloramine should be considered as an effective alternative to chlorine dioxide in controlling legionellae contamination inside hospital water distribution systems.

Isolation of nontuberculous mycobacteria from hospital waters in Turkey

Nontuberculous mycobacteria (NTM) are ubiquitous in hot and cold water distribution systems. With molecular typing methods it was shown that water can be the source of colonization and infection with NTM. The aim of our study was the investigation of NTM in hot and cold water samples taken from various departments of two hospitals in Istanbul, Turkey. Totally, 160 water samples were examined. The temperature, pH, and free chlorine levels of water samples were measured between 10-41 °C, 6.78-7.98 and <0.3-0.5 mg/L, respectively. NTM were detected in 33 (20.6%) samples. Totally 20 (60.6%), 10 (30.3%) and 3 (9.1%) isolates were identified as Mycobacterium lentiflavum, Mycobacterium gordonae, and Mycobacterium peregrinum, respectively. M. lentiflavum, which was the most frequently isolated NTM, is characterized by multiple resistance to antimycobacterial drugs. Although no infections with this mycobacterium were reported from our country so far, preventive measures may be considered in patients under immunosuppression. Because no significant correlations were found among the presence of NTM or species distribution and water temperature, pH or free chlorine levels, other factors need to be investigated.

Production and distribution of domestic hot water in selected Danish apartment buildings and institutions. Analysis of consumption, energy efficiency and the significance for energy design requirements of buildings

The goal of this work has been to document the efficiency of domestic hot water (DHW) distribution systems and to propose more energy efficient and environmentally friendly solutions for DHW systems based on analyses of existing conditions.In the article, measurements from 13 apartment buildings and two institutions are presented, i.e. consumption of DHW, heat loss from circulation lines and efficiency of the DHW system. The heat load and the cooling of the district heating water for DHW are documented as well.Possibilities for improving the DHW system include new types of circulation pipes, which have the potential of a 40% reduction of heat losses. In addition to the reduction of heat losses inside the building, a low return temperature from the hot water system will have a large impact on the heat losses from the district heating network when the building is being heated by district heating.It is likely that the production and distribution of DHW in buildings will constitute a dominant share of both the present, and in particular, the future energy design requirements of buildings. The results of this project could influence not only future buildings, but also existing buildings when renovation of installations take place.

Negative Impact of Bacteria Legionella Pneumophila in Hot Water Distribution Systems on Human Health

Negative Impact of Bacteria Legionella Pneumophila in Hot Water Distribution Systems on Human Health

Nosocomial Legionnaires’ Disease: Risque and Prevention

In 1977, Fraser et al. described an outbreak of pneumonia among legionnaires attending a convention at a hotel in Philadelphia in 1976. Legionnaires’ disease (LD) can be nosocomial, community acquired or travel related. The incidence of hospital-acquired legionellosis appears to be increasing. Colonization of water systems by <i>Legionella</i> spp. is ubiquitous in hospitals throughout the world. The outbreak, which later became known as legionnaires’ disease, was caused by a new pleomorphic, faintly staining gram-negative bacillus, <i>L.</i><i> </i><i>pneumophila</i>, which was isolated at the Center for Disease Control from lung tissues of legionnaires who died. Risk assessment for this disease forms the basis for the institution of control measures. Detection and quantification of <i>Legionella</i> spp. in the environment, in particular in the hospital water distribution system is one of the cornerstones of risk assessment. This review summarizes the current state-of-the-art regarding these aspects and points out important areas which require further study. The environmental surveillance revealed that the centralized hot water distribution system of the hospital was colonized with <i>Legionella</i>. Methods of prevention of the organisms for eradication involved in hospital water systems.

Predictive control and thermal energy storage for optimizing a multi-energy district boiler

As part of the OptiEnR research project, the present paper deals with optimizing the multi-energy district boiler of La Rochelle (France) adding to the plant a controlled thermal storage tank. This plant supplies domestic hot water and heats residential and public buildings, using renewable and fossil resources. Due to the complexity of the district boiler as a whole and the strong interactions between the sub-systems, previous works focused first on a modular approach used for the modeling of the plant. Next, a methodology based on both a multi-resolution analysis and the use of artificial neural networks was proposed to forecast the outdoor temperature and the thermal power consumption of the hot water distribution network. The present paper deals first with the modeling of a stratified thermal storage tank. Next, a basic and easy-to-implement controller was developed. Finally, using the global model of the district boiler, a model predictive controller generated optimal command sequences dealing with the flow of the water passing through the storage tank and the wood boiler set-point temperature. As a result, the consumption of fossil fuels, CO2 emissions and functioning cost were significantly reduced. Energy is stored during low-demand periods and used when demand is high, instead of engaging the gas–fuel oil boiler.

Development of a miniaturized DNA microarray for identification of 66 virulence genes of Legionella pneumophila

For the last five years, Legionella sp. infections and legionnaire's disease in Poland have been receiving a lot of attention, because of the new regulations concerning microbiological quality of drinking water. This was the inspiration to search for and develop a new assay to identify many virulence genes of Legionella pneumophila to better understand their distribution in environmental and clinical strains. The method might be an invaluable help in infection risk assessment and in epidemiological investigations. The microarray is based on Array Tube technology. It contains 3 positive and 1 negative control. Target genes encode structural elements of T4SS, effector proteins and factors not related to T4SS. Probes were designed using OligoWiz software and data analyzed using IconoClust software. To isolate environmental and clinical strains, BAL samples and samples of hot water from different and independent hot water distribution systems of public utility buildings were collected. We have developed a miniaturized DNA microarray for identification of 66 virulence genes of L. pneumophila. The assay is specific to L. pneumophila sg 1 with sensitivity sufficient to perform the assay using DNA isolated from a single L. pneumophila colony. Seven environmental strains were analyzed. Two exhibited a hybridization pattern distinct from the reference strain. The method is time- and cost-effective. Initial studies have shown that genes encoding effector proteins may vary among environmental strains. Further studies might help to identify set of genes increasing the risk of clinical disease and to determine the pathogenic potential of environmental strains.

Control of Legionella contamination in a hospital water distribution system by monochloramine

We report the results of 1-year application of monochloramine to control Legionella pneumophila contamination in a hospital hot water distribution system. In the main building of the hospital, a device continuously distributing monochloramine was installed. Legionella pneumophila and Pseudomonas spp contamination was followed in comparison with 2 other water networks in the same building using chlorine dioxide. Monochloramine significantly reduced the number of contaminated sites compared with baseline (from 97.0% to 13.3%, respectively), chlorine dioxide device I (from 100% to 56.7%, respectively), and device II (from 100% to 60.8%, respectively). No positive sample exceeded 10(4) colony-forming units/L versus 59.4% at baseline. Monochloramine could represent a good alternative to chlorine dioxide in controlling legionellae contamination in public and private buildings.

Modular approach for modeling a multi-energy district boiler

The present paper deals with the modeling of a district boiler (city of La Rochelle, west coast of France), as part of the OptiEnR research project. This “multi-energy” boiler supplies domestic hot water and heats residential and public buildings, using mainly wood and sometimes fuel or gas if necessary. The OptiEnR research project focuses on optimizing the performance of the boiler. Its main objective is to minimize the use of fossil energy, stocking renewable energy during low-demand periods and using it when peak-demand is high. Because of both the complexity of the plant as a whole and the strong interactions between the sub-systems (the wood boiler, the gas-fuel oil boiler, the breaking pressure bottle, the cogeneration plant, the hot water distribution network), a modular approach has been proposed. According to what information is available, a combination of white, grey and black boxes (Hammerstein–Wiener models) has been used to carry out the modeling task. To answer for the lack of information, additional parameters were proposed and identified. The model has been first used in simulation during heating periods, with the aim of optimizing both the parameters of the boilers control systems and the use of wood, gas and fuel oil. Next, it will be used, when adding to the plant a thermal storage unit and implementing a model predictive controller, to improve its functioning, especially reducing the coverage rate of the fossil energy boiler.

Ecological behaviour of three serogroups of Legionella pneumophila within a model plumbing system

Three Legionella pneumophila strains isolated from water samples and belonging to serogroups (sgs) 1, 6 and 9 were analysed for their capacity to colonise an experimental model simulating a domestic hot water distribution system. Ecological factors that could influence the persistence of the sgs such as intracellular life within protozoan hosts and bacterial interference by the production of antagonistic compounds were also studied. Viable counts of L. pneumophila increased both in the planktonic and in the sessile phases. Sg 6 showed a marked prevalence during the whole experiment and exhibited the highest host infection efficiency. Sg 1 was significantly less represented, but showed the highest capacity to reproduce in the protozoan hosts. Sg 9 was poorly represented and less adapted to intracellular life. Among the 14 bacteria constantly isolated in the system, five (35.7%) produced antagonistic substances against Legionella, with differences according to the bacterial strain and L. pneumophila sgs.

Effectiveness of different methods to control legionella in the water supply: ten-year experience in an Italian university hospital

We report our ten-year experience of hyperchlorination, thermal shock, chlorine dioxide, monochloramine, boilers and point-of-use filters for controlling legionella contamination in a hospital hot water distribution system. Shock disinfections were associated with a return to pre-treatment contamination levels within one or two months. We found that chlorine dioxide successfully maintained levels at <100 cfu/L, whilst preliminary experiments gave satisfactory results with monochloramine. No contamination was observed applying point-of-use filters and electric boilers at temperatures of >58°C and no cases of nosocomial legionellosis were detected in the ten-year observation period. Our performance ranking in reducing legionella contamination was filter, boiler, chlorine dioxide, hyperchlorination and thermal shock. Chlorine dioxide was the least expensive procedure followed by thermal shock, hyperchlorination, boiler and filter. We suggest adopting chlorine dioxide and electric boilers in parallel.

온수분배기용 유량제어밸브의 개발

The developed control valves, installed on the hot water distribution manifolds for the floor heating system, consist of the balancing valves and the shut-off valves. The balancing valve was designed to improve the flow control performance and to reduce the noise emitted from the valve by modification of the general V port. The port of the shut-off valve was designed with two ceramic plates, working by rotating upper plate, to improve the duration and to reduce the noise. For the evaluation of the new valves, the flow rate was measured and noise level test was carried out. The test results showed that the error of the flow rate accuracy test for the flow balance of each manifold circuit was less than and the noise level was less than 35 dB(A).

Influence of moisture content on measurement accuracy of porous media thermal conductivity

AbstractThe thermal conductivity measurement accuracy of sand was experimentally studied with a hot disk thermal constant analyzer and water morphologies, distribution, and evolution at the pore scale were observed with a charge coupled device (CCD) combined with a microscope. It was found that thermal conductivities of samples with low moisture content (&lt;25%) could not be accurately measured. For samples with low moisture content, the analysis showed that the water in the region adjacent to the analyzer sensor mainly existed as isolated liquid bridges between/among sand particles and would evaporate and diffuse to relatively far regions because of being heated by the sensor during measurement. Water evaporation and diffusion caused the sample constitution in the region adjacent to the sensor to vary throughout the whole measurement process, and accordingly induced low accuracy of the obtained thermal conductivities. Due to high water connectivity in pores, the rate of water evaporation and diffusion in porous media of high moisture content was relatively slow when compared with that of low moisture content. Meanwhile, water in the relatively far regions flowed back to the region adjacent to the sensor by capillary force. Therefore, samples consisting of the region adjacent to the sensor maintained the constant and thermal conductivities of porous media with relatively high moisture content and could be measured with high accuracy. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20272

Thermal disinfection of hotels, hospitals, and athletic venues hot water distribution systems contaminated by Legionella species

Legionella spp. (> or = 500 cfu liter(-1)) were detected in 92 of 497 water distribution systems (WDS) examined. Thermal disinfection was applied at 33 WDS. After the first and second application of the disinfection procedure, 15 (45.4%) and 3 (9%) positive for remedial actions WDS were found, respectively. Legionella pneumophila was more resistant to thermal disinfection than Legionella non-pneumophila spp. (relative risk [RR]=5.4, 95% confidence intervals [CI]=1-35). WDS of hotels with oil heater were more easily disinfected than those with electrical or solar heater (RR=0.4 95% CI=0.2-0.8). Thermal disinfection seems not to be efficient enough to eliminate legionellae, unless repeatedly applied and in combination with extended heat flushing, and faucets chlorine disinfection.