Hot Water Distribution Systems Research Articles

Persistence of viable but nonculturable Legionella pneumophila state in hospital water systems: A hidden enemy?

There is little evidence of the long-term consequences of maintaining sanitary hot water at high temperatures on the persistence of Legionella in the plumbing system. The aims of this study were to describe the persistence and genotypic variability of L. pneumophila in a hospital building with two entirely independent hot water distribution systems, and to estimate the thermotolerance of the genotypic variants by studying the quantity of VBNC L. pneumophila. Eighty isolates from 55 water samples obtained between the years 2012–2017 were analyzed. All isolates correspond to L. pneumophila serogroup 6. The isolates were discriminated in four restriction patterns by pulsed-field gel electrophoresis. In one installation, pattern A + Aa predominated, accounting for 75.8 % of samples, while the other installation exhibited pattern B as the most frequent (81.8 % of samples; p < 0.001). The mean temperature of the isolates was: 52.6 °C (pattern A + Aa) and 55.0 °C (pattern B), being significantly different. Nine strains were selected as representative among patterns to study their thermotolerance by flow-cytometry after 24 h of thermic treatment. VBNC bacteria were detected in all samples. After thermic treatment at 50 °C, 52.0 % of bacteria had an intact membrane, and after 55 °C this percentage decreased to 23.1 %. Each pattern exhibited varying levels of thermotolerance. These findings indicate that the same hospital building can be colonized with different predominant types of Legionella if it has independent hot water installations. Maintaining a minimum temperature of 50 °C at distal points of the system would allow the survival of replicative L. pneumophila. However, the presence of Legionella in hospital water networks is underestimated if culture is considered as the standard method for Legionella detection, because VBNC do not grow on culture plates. This phenomenon can carry implications for the Legionella risk management plans in hospitals that adjust their control measures based on the microbiological surveillance of water.

Development of heat-shock resistance in Legionella pneumophila modeled by experimental evolution.

Because it can grow in buildings with complex hot water distribution systems (HWDS), healthcare facilities recognize the waterborne bacterium Legionella pneumophila as a major nosocomial infection threat and often try to clear the systems with a pasteurization process known as superheat-and-flush. After this treatment, many facilities find that the contaminating populations slowly recover, suggesting the possibility of in situ evolution favoring increased survival in high-temperature conditions. To mimic this process in a controlled environment, an adaptive laboratory evolution model was used to select a wild-type strain of L. pneumophila for survival to transient exposures to temperatures characteristic of routine hot water use or failed pasteurization processes in HWDS. Over their evolution, these populations became insensitive to exposure to 55°C and developed the ability to survive short exposures to 59°C heat shock. Heat-adapted lineages maintained a higher expression of heat-shock genes during low-temperature incubation in freshwater, suggesting a pre-adaptation to heat stress. Although there were distinct mutation profiles in each of the heat-adapted lineages, each acquired multiple mutations in the DnaJ/DnaK/ClpB disaggregase complex, as well as mutations in chaperone htpG and protease clpX. These mutations were specific to heat-shock survival and were not seen in control lineages included in the experimental model without exposure to heat shock. This study supports in situ observations of adaptation to heat stress and demonstrates the potential of L. pneumophila to develop resistance to control measures. IMPORTANCE As a bacterium that thrives in warm water ecosystems, Legionella pneumophila is a key factor motivating regulations on hot water systems. Two major measures to control Legionella are high circulating temperatures intended to curtail growth and the use of superheat-and-flush pasteurization processes to eliminate established populations. Facilities often suffer recolonization of their hot water systems; hospitals are particularly at risk due to the severe nosocomial pneumoniae caused by Legionella. To understand these long-term survivors, we have used an adaptive laboratory evolution model to replicate this process. We find major differences between the mutational profiles of heat-adapted and heat-naïve L. pneumophila populations including mutations in major heat-shock genes like chaperones and proteases. This model demonstrates that well-validated treatment protocols are needed to clear contaminated systems and-in an analog to antibiotic resistance-the importance of complete eradication of the resident population to prevent selection for more persistent bacteria.

Legionella maioricensis sp. nov., a new species isolated from the hot water distribution systems of a hospital and a shopping center during routine sampling.

Two Legionella-like strains isolated from hot water distribution systems in 2012 have been characterized phenotypically, biochemically and genomically in terms of DNA relatedness. Both strains, HCPI-6T and EUR-108, exhibited biochemical phenotypic profiles typical of Legionella species. Cells were Gram-negative motile rods which grew on BCYEα agar but not on blood agar and displayed phenotypic characteristics typical of the family Legionellaceae, including a requirement for l-cysteine and testing catalase positive. Both strains were negative for oxidase, urease, nitrate reduction and hippurate negative, and non-fermentative. The major ubiquinone was Q12 (59.4 % HCPI-6T) and the dominant fatty acids were C16 : 1 ω7c (28.4 % HCPI-6T, ≈16 % EUR-108), C16 : 0 iso (≈22.5 % and ≈13 %) and C15 : 0 anteiso (19.5 % and ≈23.5 %, respectively). The percent G+C content of genomic DNA was determined to be 39.3 mol %. The 16S rRNA gene, mip sequence and comparative genome sequence-based analyses (average nucleotide identity, ANI; digital DNA-DNA hybridization, dDDH; and phylogenomic treeing) demonstrated that the strains represent a new species of the genus Legionella. The analysis based on the 16S rRNA gene sequences showed that the sequence similarities for both strains ranged from 98.8-90.1 % to other members of the genus. The core genome-based phylogenomic tree (protein-concatemer tree based on concatenation of 418 proteins present in single copy) revealed that these two strains clearly form a separate cluster within the genus Legionella. ANI and dDDH values confirmed the distinctiveness of the strains. Based on the genomic, genotypic and phenotypic findings from a polyphasic study, the isolates are considered to represent a single novel species, for which the name Legionella maioricensis sp. nov. is proposed. The type strain is HCPI-6T (=CCUG 75071T=CECT 30569T).

Transcriptomic Adaptation of Legionella pneumophila to Transient Heat Shock

A natural inhabitant of freshwater microbial ecology, Legionella pneumophila is an opportunistically pathogenic bacteria that has found a niche in hot water distribution systems (HWDS) where it challenges hospitals with the spread of nosocomial infection. Superheat-and-flush is a high-temperature pasteurization which can be temporarily effective, but systems often test positive for contamination soon after pasteurization. Because of the centrality of pasteurization in HWDS sanitation schemes, an understanding of the L. pneumophila intrinsic heat shock response may help improve the strategies used to counter its proliferation and ability to trigger nosocomial outbreaks. We tested a group of strains to assess differences in heat shock tolerance between clinical, laboratory, and environmental strains of different origin. The transcriptome of a model Philadelphia-1 L. pneumophila strain in response to heat shock was determined using microarray as an exploratory analysis of the heat shock response: 401 genes were induced, including genes involved in determining protein fate and ribosome biosynthesis while 43 genes were downregulated. Mutants of 3 individual genes were tested to find their direct effects on heat shock tolerance. Deletions of dksA or rpoS, genes involved in the regulation of life cycle switching and important for surviving long-term nutrient deprivation in freshwater lowered heat shock tolerance, suggesting an overlap in the pathways required to tolerate these stressors. Surprisingly, the deletion of htpG, the 90-kilodalton heat shock protein, was found to increase the ability to survive under transient heat shock. Taken altogether, our results show that L. pneumophila exhibits most components of the conserved bacterial heat shock response. Based on this exploratory transcriptomic study, we have provided data that can act as a platform for the research of L. pneumophila's survival to pasteurization in hot water systems.

Energy Consumption by DHW System with a Circulation Loop as an Energy Efficiency Component, Based on an Example of a Residential Building

In the EU countries, almost 50% of the produced energy is used in residential buildings. More than 25% of this energy is used to produce domestic hot water, of which almost 80% is used to heat water in domestic hot water circulation systems. This is due to high expectations on the part of residents based on their comfort, in particular regarding the supply of heat for heating and domestic hot water. In the course of their long-term research conducted on real systems, the authors confirmed that the operation of domestic hot water distribution systems causes significant costs, mainly due to heat losses. Therefore, typical variants of energy optimization of such systems were analyzed. Tests have shown that selected solutions, such as the use of control automation, are not sufficient, and recommended additional thermal insulation may not be applicable due to technical reasons. With an aim of finding a solution to the problem, the publication analyzes operational data from an existing heat source and domestic hot water circulation system in a residential building. On the basis of these analyses, a solution was proposed to reduce energy consumption within the installation by means of its hydraulic optimization. The reduction of heat losses in domestic hot water installation by means of a method presented by the authors is estimated at approximately 20%.

Environmental surveillance of Legionella in tourist facilities of the Balearic Islands, Spain, 2006 to 2010 and 2015 to 2018.

BackgroundLegionnaires’ disease is a respiratory illness often associated with hotels and travel. Spain is a major tourist destination and one of the European countries with most cases of Legionnaires’ disease , both community- and travel-associated. However, the prevalence of Legionella in tourist facilities is unknown.AimThe present investigation aimed to survey the tourist facilities in the Balearic Islands, Spain, for Legionella prevalence.MethodsWe visited tourist facilities in the Balearic Islands in two different periods (2006–2010 and 2015–2018) and took water samples following national and international guidelines. Legionella was investigated by culture methods following international standards (ISO 11731:1998).ResultsWe evaluated 13,472 samples from 465 facilities. Bacteria of the Legionella genus were detected in 65.4% of the surveyed facilities. Contamination of the facilities was significantly higher during the second decade (54.5 vs 78.6%). The most frequent colonisers were L. pneumophila serogroup 2–14. We detected the pathogen in 15.9% and 6.9% of hot and cold water distribution systems samples, respectively. The Legionella contamination rate in cold water systems samples was higher when free chlorine levels were < 0.2 mg/L and at > 25 °C temperatures, while in the hot water systems samples, the contamination rate was higher at < 50 °C. Of the samples from hot tubs, 10.9% were contaminated.Conclusion Legionella prevalence in hotels in the Balearic Islands was high but the contamination rates depended on the installations. Corrective measures are still needed to improve Legionella control.

Determination of Legionella spp. prevalence in Spanish hotels in five years. Are tourists really at risk?

Legionella spp. is the etiological agent of the serious respiratory pneumonia known as Legionnaires' disease. This respiratory illness is frequently associated with travel and tourist resorts. Spain is an important tourist destination, and one of the top European countries concerning Legionnaires’ disease cases, both community and travel associated. Still, the colonization of Legionella in our hotels remains scarce. Here, we surveyed 204 hotels in the Canary Islands, Spain, for five years (2015–2019), to determine the Legionella prevalence. Samples were obtained and analysed following national and international guidelines. We detected the pathogen in 140 of 2,318 samples (6.0%). The water distribution systems (WDS) were more colonized (7.4%) than the whirlpools (4.7%). Contamination levels were minimal (<3 log CFU L−1) in most of the cases, and only 3.6% of samples were highly contaminated minimal (>4 log CFU L−1). We isolated Legionella in 4.3% and 8.5% of cold and hot water distribution systems, respectively. The Legionella prevalence in cold water systems samples was higher when free chlorine levels were below 0.2 mg L−1, whereas in the hot water systems samples, the prevalence was higher at <50 °C. Legionella pneumophila was the most frequently isolated species, being the members of the serogroups 2–14 the most prevalent. The annual distribution showed a colonization pick in June, followed by the winter months. Regarding the geographical distribution, the presence of Legionella was more prevalent in the western islands. Our study concludes that Legionella contamination rates in samples from facilities of the Canary Islands is lower than most of the observed in other European studies. However, corrective measures are still needed to improve Legionella control.

Heat Loss Reduction in the Selected Hot Water Distribution System

One possibility of reducing the energy consumption of buildings is to reduce heat loss in hot water distribution system kept in buildings. The aim of this paper is to present the results of research, which focused on energy efficiency of the distribution system of hot water in residential buildings. As part of the research have been carried out test measurements on the hot water distribution line and air temperature around the distribution line. Test measurements were conducted in two separate stages, in which measurements were made, as with continuous and intermittent operation in distribution system. The first stage of measurements took place before reconstruction of hot water distribution system when pipes weren´t insulated with thermal insulation. The second stage took place after reconstruction of the system, when pipes were fitted with thermal insulation. The aim of the research was to determine the course of the temperature of the water in the distribution system in different stages and highlight the effectiveness of isolating the hot water distribution system.

Investigating Bacterial and Free-Living Protozoa Diversity in Biofilms of Hot Water Pipes of Apartment Buildings in the City of Riga (Latvia)

Background: Biofilms, when formed on the surfaces of water pipes, can be responsible for a wide range of water quality and operational problems. We sought to assess the bacterial and free-living protozoa (FLP) diversity, in relation to the presence of Legionnaire's disease-causing bacteria Legionella pneumophila (L. pneumophila) in 45 biofilms of hot water distribution system pipes of apartment buildings in Riga, the capital city of Latvia.Results: 16S rRNA amplicon sequencing (metataxonomics) revealed that each biofilm contained 224 rather evenly distributed bacterial genera and that most common and most abundant were two genera, completely opposites in terms of their oxygen requirements: the obligately anaerobic Thermodesulfovibrio and the strictly aerobic Phenylobacterium. Water temperature and north-south axis (i.e., different primary water sources) displayed the most significant effect on the inter-sample variations, allowing us to re-construct three sub-networks (modules) of co-occurring genera, one involving (potentially FLP-derived) Legionella spp. Pangenome-based functional profile predictions suggested that all three may be dominated by pathways related to the development and maintenance of biofilms, including quorum sensing and nutrient transport, as well as the utilization of various energy sources, such as carbon and nitrogen. In our 18S rRNA amplicon sequencing data, potential hosts of L. pneumophila were detected in 11 out of 12 biofilm samples analyzed, however, in many cases, their relative abundance was very low (&amp;lt;1%). By validating our findings using culture-based methods, we detected L. pneumophila (serogroups 2, 3, 6 and 9) in nine (20%) biofilms, whereas FLP (mostly Acanthamoeba, Vahlkampfidae and Vermamoeba spp.) were present in six (~13%) biofilms. In two biofilms, L. pneumophila and its potential hosts were detected simultaneously, using culture-based methods.Conclusions: Overall, our study sheds light on the community diversity of hot water biofilms and predicts how several environmental factors, such as water temperature and source might shape it.

Preventing Healthcare-Associated Legionellosis with Rapid Reduction of High Concentrations of Legionella Using Mechanical Removal of Blind Ends and Intensive Hot Water Flushing

Background: The aim of this paper was to present the effectiveness of the mechanical removal of blind ends and flushing of hot water systems at outlets as the only possible emergency measures to reduce the concentration of Legionella spp in hot water. Methods: Two measures have been undertaken: mechanical removal of blind ends and intensive hot water flushing when the water has not been used for more than 7 days. Results: We detected Legionella pneumophila serogroup 1 in concentration of 1.000- 55.000 CFU/L at all samples sites. In the control sampling, after three weeks, we found seven sampling sites negative for Legionella and only two sampling sites positive. All nine sampling sites were negative after ten weeks. Conclusion: Establishing good water flow throughout the hospital seems to be the most important measure, in order to make the multiplication of Legionella in the hot water distribution systems unlikely.

Numerical Modeling of The Effects of Reclamation and Proposed Infrastructures on Thermal Dispersion of Power Plant Wastewater at PLTGU Muara Karang, Jakarta Bay

Reclamation plan in Jakarta Bay close to the power plant cooling water discharge location. It will affect hot water distribution system and possibly increase water temperature around the power plant intake location. The increase in water temperature at the intake location will disrupt the operation of the power plant. The impact of hot water discharge to the intake location can be reduced by extending the intake channel and building barrier walls as planned by the Muara Karang Power Plant. Modeling is done with 3 scenarios, namely the existing condition, the existence of the reclamation island, and the proposed infrastructure around the power. This modeling aims to determine the effect of the reclamation island on heat distribution, especially around the intake location and the effectiveness of the infrastructures in minimizing the problem. Simulation for the east and west monsoons is done in 3 dimensions with MIKE3 Flow Model FM (DHI) by applying temperature function. Overall, the presence of reclamation island will increase the average temperature at the intake by 0.32 to 0.7°C compared to the existing conditions, and the proposed infrastructure is quite effective to reduce the temperature at the intake by 0.5 to 0.8°C.

THE ANALYSIS OF WATER SPEED INFLUENCE IN HOT-WATER DISTRIBUTION SYSTEM ON THE AMOUNT OF HEAT LOSS

One of the main tasks around the world is to reduce energy consumption with constant consumer comfort. The hot water supply system uses a significant part of thermal energy and requires no less attention than the heating or ventilation system. The amount of heat loss from hot water distribution systems is of great importance for the energy consumption of buildings. In winter, part of this heat is used for space heating, in summer they are unused and is considered as lost heat. For this reason, this paper considers the influence of water velocity in the pipe, pipe size, and water temperature on the total heat losses in the insulated hot-water distribution system. The data are presented in tabular and graphical form. A graph of the dependence of the amount of heat loss on the temperature and velocity of hot water is obtained.

The Tail-Specific Protease Is Important for Legionella pneumophila To Survive Thermal Stress in Water and inside Amoebae.

Legionella pneumophila (Lp) is an inhabitant of natural and human-made water systems, where it replicates within amoebae and ciliates and survives within biofilms. When Lp-contaminated aerosols are breathed in, Lp can enter the lungs and may infect human alveolar macrophages, causing severe pneumonia known as Legionnaires' disease. Lp is often found in hot water distribution systems (HWDS), which are linked to nosocomial outbreaks. Heat treatment is used to disinfect HWDS and reduce the concentration of Lp However, Lp is often able to recolonize these water systems, indicating an efficient heat shock response. Tail-specific proteases (Tsp) are typically periplasmic proteases implicated in degrading aberrant proteins in the periplasm and important for surviving thermal stress. In Lp Philadelphia-1, Tsp is encoded by the lpg0499 gene. In this paper, we show that Tsp is important for surviving thermal stress in water and for optimal infection of amoeba when a shift in temperature occurs during intracellular growth. We also demonstrate that Tsp is expressed in the postexponential phase but repressed in the exponential phase and that the cis-encoded small regulatory RNA Lpr17 shows the opposite expression, suggesting that it represses translation of tsp In addition, our results show that tsp is regulated by CpxR, a major regulator in Lp, in an Lpr17-independent manner. Deletion of CpxR also reduced the ability of Lp to survive heat shock. In conclusion, our study shows that Tsp is likely an important factor for the survival and growth of Lp in water systems.IMPORTANCELp is a major cause of nosocomial and community-acquired pneumonia. Lp is found in water systems, including hot water distribution systems. Heat treatment is a method of disinfection often used to limit the presence of Lp in such systems; however, the benefit is usually short term, as Lp is able to quickly recolonize these systems. Presumably, Lp responds efficiently to thermal stress, but so far, not much is known about the genes involved. In this paper, we show that the Tsp and the two-component system CpxRA are required for resistance to thermal stress when Lp is free in water and when it is inside host cells. Our study identifies critical systems for the survival of Lp in its natural environment under thermal stress.

Saving cold drinking water in residential hot water distribution systems

In homes that have instantaneous gas heaters to heat water, cold water is wasted in the first seconds of using hot water fixtures. This waste is caused due to the large lengths of piping between the hot water fixtures and the heater that feeds them. The water in such pipes suffers thermal losses over time. When turning on the fixtures, this drinking water, because it is cold, is rejected by users, especially when using showers. This work deals with the conformation of a system that avoids wasting water in residential hot water services. To establish this conformation, a usual plumbing design was analysed to verify the changes proposed in order to optimise the operation of the system. The gas-heated hot water pipes are currently installed so that the pipes start at the heater and run through the entire house to the hot water fixtures furthest from the heater. It was found that the waste of water in a water fixture decreases if there is the consumption of hot water previously in one of the water fixtures of the house. To avoid this waste, according to the configuration of the current plumbing systems, it is necessary to install an additional set of electronic equipment that automatically redirects the cold water − that would be wasted − to a water tank for later use. The system proposed is composed of a solenoid valve located at the end of the hot water pipe. This valve has the function of letting flow to the water tank the approximate amount of cold water that would be wasted. Through a radio frequency signal sent when a button located near the hot water fixtures is pressed, the system recognises which water fixture was turned on and the approximate amount of cold water that must be released through the valve until the arrival of hot water from the heater. Then, there must be a pipe that collects the water that flows through the solenoid valve. Such pipe will be connected to a vertical pipe, responsible for collecting water from all flats and directing the water to the water tank. The installation of the system is based on the recommendations of the standards used in Brazil and the most frequent configuration found in homes. This work also serves as a guide for installing the system in homes other than the example shown herein.

How Molecular Typing Can Support Legionella Environmental Surveillance in Hot Water Distribution Systems: A Hospital Experience.

In this study, we aimed to associate the molecular typing of Legionella isolates with a culture technique during routine Legionella hospital environmental surveillance in hot water distribution systems (HWDSs) to develop a risk map able to be used to prevent nosocomial infections and formulate appropriate preventive measures. Hot water samples were cultured according to ISO 11731:2017. The isolates were serotyped using an agglutination test and genotyped by sequence-based typing (SBT) for Legionella pneumophila or macrophage infectivity potentiator (mip) gene sequencing for non-pneumophila Legionella species. The isolates’ relationship was phylogenetically analyzed. The Legionella distribution and level of contamination were studied in relation to temperature and disinfectant residues. The culture technique detected 62.21% of Legionella positive samples, characterized by L. pneumophila serogroup 1, Legionella non-pneumophila, or both simultaneously. The SBT assigned two sequence types (STs): ST1, the most prevalent in Italy, and ST104, which had never been isolated before. The mip gene sequencing detected L. anisa and L. rubrilucens. The phylogenetic analysis showed distinct clusters for each species. The distribution of Legionella isolates showed significant differences between buildings, with a negative correlation between the measured level of contamination, disinfectant, and temperature. The Legionella molecular approach introduced in HWDSs environmental surveillance permits (i) a risk map to be outlined that can help formulate appropriate disinfection strategies and (ii) rapid epidemiological investigations to quickly identify the source of Legionella infections.

Corrosion resistance of commonly used plumbing materials for water distribution systems exposed to disinfection treatments

ABSTRACTIn this study, the corrosion resistance of commonly used plumbing materials was evaluated when three disinfection treatments were applied in hot water distribution systems. In particular copper, brass, stainless steel and galvanised steel were tested in environments containing monochloramine, chlorine dioxide and hydrogen peroxide disinfectants under real field conditions for a long period of time (1 year), in order to evaluate the effect of free corrosion on the metal specimens; chlorinated polyvinylchloride (CPVC) was tested in the same environments in order to evaluate the degradation of the mechanical properties of plastic specimens. The results obtained enabled us to rank the metallic materials corrosion resistance against disinfectants in decreasing order, as follows: stainless steel, copper and copper-based alloys, galvanised steel. CPVC samples proved to be extremely stable in all of the disinfectants investigated, maintaining the same compression behaviour of the pipes aged with untreated water after 12 months of exposure.

EVOLUCIÓN DE LOS MATERIALES UTILIZADOS EN REDES DE DISTRIBUCIÓN DE AGUA CALIENTE

Nowadays, one of the most significant technological challenges is the decreasing dependence of carbon-based fuels and the polluting emissions into the atmosphere. In pursuit of that objective, the Directive 2010/31/UE from the European Commission, provided that all new buildings must be low energy consumption, nearly zero-energy. This Directive is being transposed into national law through the modification of CTE, Technical Building Code and RITE, Regulation of Thermal Installations in Buildings, both are pending to publish along this year 2018. According to the data from both the European Commission recommendations about net primary energy consumption at kWh/(m2/year) and the Development Ministry communicated in the EECN Congress, celebrated last December 2017, the outer skin, solar protection and ventilation of new buildings going to reach a very high level of efficiency, so energy consumption by domestic hot water will become very important. This change in residential buildings energy consumption profile, requires a detailed study of this system. This work studies, statistically, the materials more used in domestic hot water distribution systems, thanks to the data from last years gathered by Spanish Professional Associations both new and refurbishment Works. In a first step of this study, it is concluded that the metallic materials use has been reduced considerably, but nowadays these materials are used about in 20% of building works, despite their worst thermal transmission coefficient. We also know that the material more used is Cross-Linked Polyethylene, however, there are important differences over all the Spanish regions.

Prevalence of Legionella spp. in hot water samples from Polish hospitals in 2009-2013

Background: Microbiological threat from Legionella spp. is associated with the current widespread use of air-condition systems and frequent colonization of hot water distribution systems in public facilities (hospitals, hotels, nursing homes). This poses a particularly high risk in hospitalized patients, as many of them are immunocompromised. More than 50 species and 72 serogroups of Legionella spp. have been described thus far, including more than 20 species being pathogenic to humans. Material/Methods: Microbiological threat posed by Legionella spp. was assessed based on a retrospective analysis of microbiological quality of water from hot water distribution systems in Polish hospitals, determined in 2009-2013 at certified laboratories of the Sanitary-Epidemiological Surveillance. The results were kindly provided by the hospitals’ administration upon request, for which the authors would like to express their deepest gratitude. The study material included samples of hot water from internal distribution systems in 379 Polish hospitals, collected by the State Sanitary Inspectorate. Results: Based on the results of microbiological analyses, we were able to estimate Legionella spp. colonization rates in hospital water distribution systems and to assess the activities undertaken by the State Sanitary Inspectorate to reduce excessive bacterial counts in this reservoir. Microbiological analyses conducted in 2009-2013, i.e. after implementing a statutory obligation to monitor Legionella spp. in hospital hot water distribution systems, showed elevated bacterial counts in 3.92% to 12.7% of the samples. These findings justify further microbiological monitoring of hospital water distribution systems. Discussion: The prevalence of the most pathogenic serotype SG1 in hot water distribution systems of Polish hospitals is relatively low compared to other European countries. To maintain this favorable status, hospital water systems should be monitored not only for the presence of Legionella pneumophila, but also for the prevalence of serogroup 1 L. pneumophila.

Development of a Mathematical Model for Precise Temperature Measurement in Geoinformation Systems for Monitoring Individual Heat Consumption In Apartment Buildings

One of the main energy saving objectives is to find methods for metering individual heat consumption in each apartment of an apartment building. Achievements in the area of microprocessor devices made it possible to create a new type of measurement and control systems for monitoring and metering energy resources. Newly developed heat meters are the ground for fundamental changes in energy saving and energy efficiency. Apartment buildings are heated by various hot water distribution systems, for which it is not always possible to use conventional heat meters. The ambiguity related to the parameters of heat meters can adversely affect the estimation of heat consumption by each apartment in an apartment building. This paper is aimed at analyzing a new contact temperature measurement method and means used to create a system for heat monitoring and metering in an apartment building. The developed system can be used to meter energy resources of facilities distributed in a specific area, with geographic referencing to each facility. This makes it possible to remotely monitor heat energy consumption, which makes the energy consumption control system much more transparent and ensures public control. The system gathers data from a large number of users, processes data in real time and promptly responds to users’ requests based on recent developments in information technology. An important advantage of the developed system is that it can be used to anticipate emergency situations taking into account various factors, such as weather conditions and the age of buildings. Due to all of the above, the system can be used in the future not only in Russia but also abroad.

Potential of thermal storage for hot potable water distribution in cruise ships

Hot potable water preparation in ships requires lots of energy from the power plant; this is particularly true in modern cruise ships with a high demand of potable water for people, restaurants, spa and pools. Usually the required amount of hot water is instantly produced using a number of different energy sources available on board. However, the use of direct heaters on peak demand conditions increases fuel consumption and greenhouse gas emissions. This is especially important in the case of ship in port configuration, due to the reduced number of active engines and therefore the reduced amount of waste heat from the cooling line usually employed for this task.This paper investigates possible solutions to size a hot water thermal storage in order to compensate the mismatch between heat generation during cruise and heat required during ship in port configuration. The performances of different solutions are compared using dynamic thermal simulations of the ship’s hot water distribution system with different regimes and time dependent heat requirements. Moreover it will be introduced the use of PCM materials with the aim to further improve system’s performance.