Domestic Water Systems Research Articles

Statistical analysis of parameters affecting Legionella and total cell growth in premise plumbing systems within buildings: A field study based on an empirical data set

During the storage and distribution of water in buildings, the excessive growth of pathogens can deteriorate the quality of drinking water. This study aims to investigate the factors influencing this growth and propose technical measures for prevention. The analysis is based on an empirical data set comprising 1361 samples from 204 domestic premise plumbing systems. In 14 systems, ultrafiltration plants were installed as microbiological barriers. Legionella cultivation and flow cytometry were used to determine microbiological properties. The study identified elevated total cell counts in tapping valves and pipe end lines in numerous premise plumbing systems, indicating prolonged water stagnation prior to sampling, which facilitates microbiological growth. Higher contamination rates were observed in these systems, with peripheral taps often being contaminated in lieu of the entire system. These systems were classified as microbiologically unstable due to the relevantly higher total cell numbers at hot water taps compared to the hot water tank (>25%). Furthermore, these systems exhibited a Legionella contamination rate that was 22.3% higher than in microbiologically stable systems. In some cases, peripheral contaminations may not accurately represent the entire premise plumbing system. Increasing the discard volume during sampling from 1 L to 3–5 L could provide more precise results during standard testing. Legionella species were primarily detected in the first 1 L of water after tap activation. Additionally, statistically significant relationships were observed between direct temperature and total cell number, as well as between the presence of ultrafiltration and total cell numbers at cold water taps.

Experimental investigation on wireless integrated smart system for energy and water resource management in Indian smart cities

In the realm of India's smart cities, precise meter readings are essential for effectively managing domestic energy and water systems. Nevertheless, meter reading employing conventional techniques prove to be both costly and time-consuming, especially considering the vast user base and deficit of everyday consumption analysis. To cope with this challenge, the proposed solution introduces a novel unified wireless smart metering system for measuring energy and water usage. This prototype harnesses the smart, advanced metering technology to manage energy and water resources. The presence of data and remote control capabilities in smart distribution transformers offers distribution operators the chance to optimize system operation and control. The innovative system proposed utilizes smart metering technology and incorporates a distribution system self-healing mechanism against power outages, revolutionizing the way utilities manage water and energy consumption. The system not only offers real-time consumption statistics to the utility provider but also provides the flexibility to remotely control the system's turn-on and turn-off functions. The system effectively captures real-time data, transmits it via LoRa to Telegram application. The system automatically re-establishes remote connections in the event of disconnections caused by emergency conditions or non-payment of the bill, once the relevant issue has been resolved. Additionally, the system promptly notifies authorities on overload, over-temperature, and instances of electricity theft. The system proficiently generates bills based on the consumed data and seamlessly transmits the consumed units to the authorities. The innovative system proposed has proven its ability to communicate effectively, yielding results that align with the given circumstances.

The impact of stagnation on the microbial quality of constructed water systems after COVID-19 shutdowns.

In response to COVID-19 pandemic, governments all over the world limited the movement of people and mandated temporary closure of different institutions. While, these measures helped to reduce the spread of COVID-19, stagnant water can cause water quality deterioration. Stagnation is considered in context with the proliferation of pathogenic and facultatively pathogenic bacteria which pose potential health risks to humans. The objective of this study was to document the hygienic microbiological status of different water systems after the first shutdowns (between 18th March 2020 and 18th May 2020) in Hungary in comparison with a reference period (between 3rd January 2020 to 17th March). During the reference period drinking waters were compliant > 95% of total samples to the parametric values. After the short period shutdowns, the ratio of tnon-compliant drinking water samples was 6.6%: mainly Pseudomonas aeruginosa (7%) and coliform bacteria (5%) resulted poor water quality. The microscopic analysis of drinking waters showed that after low water demand the values of non-compliant samples also increased due to the proliferation of Amoebozoa and other Protozoa species. The compliant pool waters' ratio was also high in the reference period (97-99%), while after the shutdowns more samples were positive in both pool operation type (fill-and-drain pools and pools with recirculation) due to the proliferation of P. aeruginosa (14%) and micrococci (12%). Legionella non-compliant samples in hot tap water did not show significant difference during both studied periods (15%) although after stagnation the Legionella CFU (colony forming unit) values of the samples increased markedly.

Disinfection of sink drains to reduce a source of three opportunistic pathogens, during Serratia marcescens clusters in a neonatal intensive care unit.

Evaluate the effects of five disinfection methods on bacterial concentrations in hospital sink drains, focusing on three opportunistic pathogens (OPs): Serratia marcescens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. Over two years, three sampling campaigns were conducted in a neonatal intensive care unit (NICU). Samples from 19 sink drains were taken at three time points: before, during, and after disinfection. Bacterial concentration was measured using culture-based and flow cytometry methods. High-throughput short sequence typing was performed to identify the three OPs and assess S. marcescens persistence after disinfection at the genotypic level. This study was conducted in a pediatric hospitals NICU in Montréal, Canada, which is divided in an intensive and intermediate care side, with individual rooms equipped with a sink. Five treatments were compared: self-disinfecting drains, chlorine disinfection, boiling water disinfection, hot tap water flushing, and steam disinfection. This study highlights significant differences in the effectiveness of disinfection methods. Chlorine treatment proved ineffective in reducing bacterial concentration, including the three OPs. In contrast, all other drain interventions resulted in an immediate reduction in culturable bacteria (4-8 log) and intact cells (2-3 log). Thermal methods, particularly boiling water and steam treatments, exhibited superior effectiveness in reducing bacterial loads, including OPs. However, in drains with well-established bacterial biofilms, clonal strains of S. marcescens recolonized the drains after heat treatments. Our study supports thermal disinfection (>80°C) for pathogen reduction in drains but highlights the need for additional trials and the implementation of specific measures to limit biofilm formation.

Monitoring of fresh water consumption and energy needs for hot tap water heating in residential buildings

The study addresses discrepancies between design and measured values in building energy systems, focusing on water heating inside buildings in Central and Eastern Europe. Using data measured by the authors from 2010 to 2019 in Czech cities, a novel empirical calculation relationship for water flow estimation in apartment buildings is introduced, which is different from the outdated 1940 equation. The proposed calculation is refined and validated based on the measured values, allowing for accurate specification of daily and hourly water demands. The innovative approach is expected to result in tangible savings and a 10–20 % reduction in energy consumption for hot water heating, emphasising its significance for sustainable energy supply to buildings.

Small-scale district heating system as heat storage for decentralized solar thermal collectors during non-heating period

Solar thermal energy usage in the Baltic countries is currently low, so there is a need to find technically and economically feasible solutions to increase the appeal of this technology. Integration of solar energy into existing district heating systems is a way to increase the share of renewable energy sources while utilizing the existing infrastructure, thereby reducing capital investments, as well as mitigating the risk of solar collector overheating and eliminating the need for local storage tanks in buildings. This study presents a parametric study for evaluating the effectiveness of using a district heating system to store heat produced by decentralized solar thermal collectors and comparing the district solution to the traditional local solution. The TRNSYS 18 model was developed for this purpose. The model investigates the impact of different hot tap water demand profiles as well as pipeline diameters and lengths on system energy efficiency, showing a statistically significant difference (p < 0.05) between installing solar collectors on residential and restaurant or office roofs, and no significant difference (p = 0.24) between restaurant and office. The model shows that solar energy can be shared within a 500 m distance between neighborhoods and that a larger main pipeline diameter can increase overall system efficiency.

Polycarbonate Ultracentrifuge Tube Re-use in Proteomic Analyses of Extracellular Vesicles.

Single-use laboratory plastics exacerbate the pollution crisis and contribute to consumable costs. In extracellular vesicle (EV) isolation, polycarbonate ultracentrifuge (UC) tubes are used to endure the associated high centrifugal forces. EV proteomics is an advancing field and validated re-use protocols for these tubes are lacking. Re-using consumables for low-yield protein isolation protocols and downstream proteomics requires reagent compatibility with mass spectroscopy acquisitions, such as the absence of centrifuge tube-derived synthetic polymer contamination, and sufficient removal of residual proteins. This protocol describes and validates a method for cleaning polycarbonate UC tubes for re-use in EV proteomics experiments. The cleaning process involves immediate submersion of UC tubes in H2O to prevent protein drying, washing in 0.1% sodium dodecyl sulfate (SDS) detergent, rinsing in hot tap water, demineralized water, and 70% ethanol. To validate the UC tube re-use protocol for downstream EV proteomics, used tubes were obtained following an experiment isolating EVs from cardiovascular tissue using differential UC and density gradient separation. Tubes were cleaned and the experimental process was repeated without EV samples comparing blank never-used UC tubes to cleaned UC tubes. The pseudo-EV pellets obtained from the isolation procedures were lysed and prepared for liquid chromatography-tandem mass spectrometry using a commercial protein sample preparation kit with modifications for low-abundance protein samples. Following cleaning, the number of identified proteins was reduced by 98% in the pseudo-pellet versus the previous EV isolation sample from the same tube. Comparing a cleaned tube against a blank tube, both samples contained a very small number of proteins (≤20) with 86% similarity. The absence of polymer peaks in the chromatograms of the cleaned tubes was confirmed. Ultimately, the validation of a UC tube cleaning protocol suitable for the enrichment of EVs will reduce the waste produced by EV laboratories and lower the experimental costs.

Pollution characteristics and health risk of sixty-five organics in one drinking water system: PAEs should be prioritized for control

Currently, a large number of emerging organic contaminants have been detected in domestic and international drinking water systems. However, there are differences among the research methods, which lead to system errors in directly comparing the hazards of different contaminants, so it is difficult to analyze the priority control pollutants and the risk control target in drinking water from previous studies. Therefore, we selected a drinking water treatment plant (DWTP) in the east of China, and detected trihalomethanes (THMs), antibiotics, phthalate esters (PAEs), organophosphate esters (OPEs), per and polyfluoroalkyl substances (PFASs), a total of sixty-five organic contaminants in one batch water sample of four seasons, and carried out the whole process monitoring of "Source water-DWTP-Network-Users", and calculated the health risks of contaminants in tap water. The results showed that DWTP could effectively remove antibiotics and PAEs; the removal rate of coagulation for antibiotics can be up to 47%; the release of PAEs in the plastic water supply pipe leads to a significant increase of the concentrations in the water transportation system, which can reach 2.92 times of that in finished water; compared with other contaminants, THMs and PAEs in tap water have higher health risks. This study reveals that THMs and PAEs are priority control organic pollutants, and the water supply network is the key risk control target in the drinking water system, providing a theoretical basis for how to ensure the safety of drinking water.

Shapes of hot water: the ontological politics of handwashing during the COVID-19 pandemic

ABSTRACT This paper explores the ontological politics and practices of handwashing using hot tap water during the COVID-19 pandemic in Sweden through attending to how handwashing was performed, what thoughts and emotions handwashing practices evoked, and reflections about why these thoughts and emotions emerged. In analyses based on written diaries, stories, digital photos, and videos from the private sphere of the home, we show how the concepts of humans, non-humans, childhood, economy, ethics, infrastructure, and nature – together with public health organizations’ promotions of handwashing recommendations – are enacted and woven into the fabric of hot tap water use. Hot tap water emerged as an ambiguous commodity, differently shaped depending on past experiences and how messages from authorities were received. The politics of the seemingly mundane activity of washing hands (especially prior to the COVID-19 pandemic) consists of connectivities and relationships between various phenomena in fluid space, and blurs the boundaries between local and global, past and present. Thrifty handwashing practices previously established in the private sphere were challenged during the COVID-19 pandemic, as popular versions of surgical scrubbing were promoted. These versions were sometimes challenged when the inclusion of hot water was questioned at home and in public debate.

Biosensors as early warning detection systems for waterborne Cryptosporidium.

Waterborne disease is a global health threat contributing to a high burden of diarrhoeal disease, and growing evidence indicates a prospective increase in incidence coinciding with the profound effects of climate change. A major causative agent of gastrointestinal disease is Cryptosporidium, a protozoan waterborne parasite identified in over 70 countries. Cryptosporidium is a cause of high disease morbidity in children and the immunocompromised with limited treatment options for patients at risk of severe illness. The hardy nature of the organism leads to its persistence in various water sources, with certain water treatment procedures proving inefficient for its complete removal. While diagnostic methods for Cryptosporidium are well-defined in the clinical sphere, detection of Cryptosporidium in water sources remains suboptimal due to low dispersion of organisms in large sample volumes, lengthy processing times and high costs of equipment and reagents. A need for improvement exists to identify the organism as an emerging threat in domestic water systems, and the technological advantages that biosensors offer over current analytical methods may provide a preventative approach to outbreaks of Cryptosporidium. Biosensors are innovative, versatile and adaptable analytical tools that could provide highly sensitive, rapid, on-site analysis needed for Cryptosporidium detection in low-resource settings.

Bacterial populations in different parts of domestic drinking water systems are distinct and adapted to the given ambient temperatures

Drinking water enters buildings with a given microbiological community composition. Within premise plumbing systems, the drinking water is subject to very different conditions and temperatures. Whereas part of the water stays cold, another part is heated to provide hot water. In this study, drinking water samples were taken at different locations in four buildings that had central heating circles and that were equipped with ultrafiltration modules. The latter were intended to keep bacterial numbers low. When studying the increase in bacterial concentrations in these water samples using regrowth tests at different incubation temperatures, a temperature-dependence could be observed. Bacteria in cold water samples propagated best when incubated at 22°C, but often poorly at 36°C and not at all at 50°C. Bacteria in hot water samples showed the reverse behavior and grew best when incubated at 50°C, whereas growth at 22°C was poor or associated with a long growth lag. Water samples from distal taps in periphery locations used for retrieving both cold and hot water showed intermediate growth behaviors. Results suggest the existence of different temperature-adapted bacterial populations within domestic drinking water systems. The finding was supported by sequence data revealing distinct differences in the microbiomes between cold and hot water samples. Abundant bacterial groups in hot water included Deinococci, Kryptonia, Ignavibacteria, Nitrospiria, Gemmatimonadetes and different genera of Gammaproteobacteria. Stagnation of hot water at 50°C, 55°C, or 60°C furthermore shaped the microbiome in different ways indicating that small temperature differences can have a substantial impact on the bacterial communities.

Investigating the Performance of the Compact Particulate Matter Collector for Use in Domestic Water Systems

The concept of the new water treatment system was developed. The system is based on the previously invented technology – Compact Particulate Matter Collector (CPMC). A primary area was defined in which such technology is intended to be used: water treatment in compact flue-gas condensation systems for a low-power wood-fuelled biomass boiler. Such a system is intended for use in domestic conditions. Such a process involves contamination of technical water with a mixture of particulate matter, resulting in suspension. The CPMC aims to divide the suspension into the relevant fractions effectively. A prototype operating based on CPMC technology was built. An experimental plan was developed, and an experimental stand was constructed to determine the prototype’s efficiency. The experimental plan envisaged five different prototype operating modes and two research steps, depending on the degree of prototype modification. Based on the research results, it was concluded that the prototype could operate effectively in the laboratory environment: achievable efficiency is equal on average between 57.84 % and 88.09 % depending on the operating mode (see the diagram below). The result is assessed as positive. TRL 3 has been reached. The next phases of the study would be the integration of the prototype into the relevant compact flue-gas condensation system and the exploration of commercialisation capabilities, which will stimulate TRL increase.

Tap water as the source of a Legionnaires' disease outbreak spread to several residential buildings and one hospital, Finland, 2020 to 2021.

In Finland, all microbiology laboratories notify Legionella findings and physicians notify Legionnaires' disease (LD) cases to the National Infectious Disease Register. All cases are interviewed, and water samples obtained from potential places of exposure. Legionella isolates from humans and water are compared by whole genome sequencing (WGS). In March 2021, Legionella pneumophila serogroup 1 (Lp 1) pneumonia cases increased in one Finnish city (120,000 inhabitants) where single LD cases are detected annually. We identified 12 LD cases, nine living in different residential buildings and three nosocomial, linked by identical human and/or water isolates. Three of these cases were from January 2020, October 2020 and February 2021 and identified retrospectively. Eleven were diagnosed by urinary antigen test, 10 by PCR and five by culture; age ranged between 52 and 85 years, and 10 had underlying diseases. Nine of 12 homes of LD cases and 15 of 26 water samples from the hospital were positive for Lp 1, with concentrations up to 640,000 cfu/L. Water samples from regional storage tanks were negative. Positivity in homes and the hospital suggested inadequate maintenance measures. Enhanced surveillance combined with WGS was crucial in detecting this unusual LD outbreak related to domestic and hospital water systems.

Effect of domestic pipe materials on microbiological safety of drinking water: Different biofilm formation and chlorination resistance for diverse pipe materials

Microbial biofilms that develop in pipe walls can pollute domestic water systems. Understanding biofilm formation and its chlorine resistance in domestic pipe materials will help reduce the possibility of microbial pollution. This study investigates microbial biofilm formation and chlorine resistance in three representative domestic pipes: polypropylene random (PPR), stainless steel (SS), and copper. Biofilm formation determined using crystal violet staining, heterotrophic plate count, and adenosine triphosphate, and extracellular polymeric substance (EPS) content of several typical bacteria were determined before and after disinfection in the different pipe materials. Bacteria in PPR pipes develop significantly more biofilm biomass than in the two metal pipes. EPS content was highest in copper pipe, while lowest biofilm biomass and EPS contents was displayed in SS pipe. The bacteria with more biofilm biomass in three pipe materials appeared to be different. Bacterial chlorine resistance did not differ significantly between the three pipe materials. The chlorine resistance of the same single-species biofilm appeared to vary in the pipe materials, and it was influenced by physiological state of bacterial cells, such as EPS. The data reveal the significant effects of domestic pipe materials on biofilm properties, which mean the possibility of microbial pollution is different.

Screening of thermal characteristics and assessment of comparative energy efficiency potential in a residential district

ABSTRACT By identifying buildings with poor thermal performance and prioritizing these in terms of energy efficiency potential, a sustainable transformation of the building stock may be accelerated. However, there is currently a lack of thermal characteristics (TCs) differentiating total energy use from hot water circulation (HWC), hot tap water (HTW) and space heating in large building portfolios. This research demonstrates a methodology based on a change-point model for identifying and prioritizing TCs, which also enables prediction of the Comparative Energy Efficiency Potential (CEEP). The change-point model allows for the differentiation of various processes, i.e. space heating, HWC and HTW, using only heating supply data and outdoor temperature. The studied district consists of 70 multi-family buildings in the Vasastaden district in Linköping, Sweden. The findings demonstrate that the proposed methodology allows for identifying and prioritizing TCs connected to HWC, HTW and space heating. The highest CEEP is in space heating, corresponding to a maximum of 2,016 MWh (16% of the district’s energy use), followed by HWC, 699 MWh (6% of the district’s energy use) and HTW, 520 MWh (4% of the district’s energy use). Consequently, a total decrease of 3,235 MWh (26%) is made possible according to the studied energy efficiency targets. HIGHLIGHTS A methodology for the prediction of the Comparative Energy Efficiency Potential (CEEP) in a building portfolio based on the identification and prioritization of TCs is proposed The study is enabled by the use of a unique change-point model (DTPC) for differentiating TCs solely from digital heating supply data and outdoor temperature 70 multi-family buildings (total heated area of 121,692 m2) in the Vasastaden district in Linköping, Sweden, are investigated The methodology is successful in identifying and prioritizing TCs related to HWC, HTW and space heating The highest CEEP is in space heating calculated at a maximum of 2016 MWh, which corresponds to 16% of the district’s total energy use

1193. Disinfection of the Sink Drains to Reduce a Source of Serratia marcescens During Infection Outbreaks in a Neonatal Intensive Care Unit

Abstract Background Sink drains are known reservoirs of pathogens and have been associated with multiple nosocomial outbreaks. In this study, the distribution of Serratia marcescens was investigated within the sink environment of a NICU and in colonized or infected newborns. The effect of different types of drain disinfection on bacterial concentration and on the detection of Serratia marcescens in sink drains was also investigated. Methods Sink drains from a NICU were sampled: 20 drains sampled for 6 weeks in the first year and 28 drains sampled for 5 months in the second year. S. marcescens isolated from positive patients were collected. A high-throughput short sequence typing (HiSST) method was developed to identify S. marcescens and compare strains and environmental DNA from sink drains with 56 clinical strains from 5 nosocomial outbreaks. Five interventions were tested: self-disinfecting drains, hot water disinfection, chlorine disinfection, steam disinfection and hot tap water flushing. Bacterial concentration of samples was measured in culture and flow cytometry and the HiSST method was used to identify S. marcescens. Results During the first and second sampling campaigns, 40% and 60% of sink drain samples were positive for S. marcescens with a moderate genotype diversity (1 to 11 different STs). The genotype profile of the 56 clinical strains was heterogeneous (26 STs). Four distinct STs were retrieved in 8 sinks after detection in patients whereas 1 ST was detected in a sink before detection in patient. Some environmental and clinical strains were found in drains for up to a year after the first sampling campaign. Each tested drain intervention reduced culturable bacteria (4-8 log) and viable bacteria (2-3 log), except for chlorine. The self-disinfecting drains, hot water and steam disinfection were able to remove temporarily S. marcescens from the drains. Conclusion The high genotypic diversity of the clinical strains suggests diffuse sources of S. marcescens within the NICU likely to cause nosocomial infection outbreaks. The self-disinfecting drains, hot water and steam disinfection seem to be the best methods to reduce bacterial concentration in drains and eliminate S. marcescens in the short term, thus limiting the risk of pathogens spread from the sink environment to patients. Disclosures All Authors: No reported disclosures.

Identifikasi jumlah angka kuman pada dispenser metode TPC (Total Plate Count)

Background: Food contamination can be caused by various factors, including food handler knowledge, body hygiene, food sanitation, and the cleanliness of cutlery. A microbiological examination that can be done is a swab of cooking utensils and cutlery, including a germ count examination. The dispenser is one of the tableware widely used by the community to provide drinks. The use of dispensers in gallon bottled drinking water consumers makes serving drinking water practical, but dispenser cleanliness is generally less considered by consumers.Objectives: The study aims to determine the number of germs in standard-temperature water faucets and hot-temperature water faucet dispensers using the TPC (Total Plate Count) method.Methods: This type of research is explanatory through a descriptive-analytic approach. The research was conducted at the Medical Technology Laboratory in 2022. Samples were taken from five water depot managers in Banda Aceh City. The media and reagents used were Physiological NaCl (0,85%), Aquadest, and Nutrient Agar (NA) media. Statistical analysis using Independent T-test at 95% CI.Results: The normal-temperature water faucet showed the highest number of germs, 193 colonies/cm2, and the lowest number of germs was shown by the hot-temperature water faucet (23 colonies/cm2). There was a difference in the number of germs between standard water taps and hot water taps (p= 0,025) in several dispensers in Banda Aceh City.Conclusion: There is a significant difference in the number of germs from dispenser swabs between standard-temperature water faucets and hot water faucets.

Efficacy of some washing solutions for removal of pesticide residues in lettuce

BackgroundWhen previous studies were examined, it was reported that a wide variety of pesticide residues were detected in lettuce (Bakırcı et al. in Food Chem 160:379–392, 2014; Balkan and Yılmaz in Food Chem 384:132516, 2022; Qin et al. in Food Res Int 72:161–167, 2015; Selim et al. in Res J Environ Sci 5:248–258, 2011). In addition, pesticide-contaminated lettuce poses a risk to consumers as it is a fresh food that is eaten raw. Therefore, pesticide removal processes must be applied before consumption. Some pesticide removal process, such as storage and heat treatment cannot be applied to lettuce because of unshelled, no long shelf life and consuming as fresh. Different practical methods are needed for the removal of pesticides process. The recommendations of suitable methods for cleaning salad materials in ready-to-eat sector, hotels, restaurants and homes are very important. It is important to reduce pesticide residues in vegetables and fruits that are consumed raw by washing them with non-toxic solutions. These approaches aim to protect public health. The study conducted in 2021 determined the effect of various washing treatments. For this purpose, before the washing trials, QuEChERS method was validated for determination of 7 pesticides in lettuce, by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Lettuce plants were grown in the greenhouse for the study. Lettuces were brought to the laboratory 24 h after pesticides were applied in the greenhouse. The samples were kept in 2 L washing solution for pesticide analysis.ResultsThe processing factor values of all washing applications were found below 1. This result shows that the residue level was reduced by washing solutions. Among the washing solution treatments, the rice vinegar washing solution was found to be most effective in reducing the pesticide residues which was due to the high degree in the pesticide degradation. Washing with filtered rice water also exhibited equivalent reduction capability similar to rice vinegar.ConclusionsThe effectiveness of washing solutions was different for boscalid, deltamethrin, fluopcolide, fluopyram, pyrimethanil, pyraclostrobin and sulfoxaflor. However, when the average removal of these pesticides was evaluated, the most effective solutions were rice vinegar, filtered rice water, carbonated water, NaCl + grape vinegar, hot tap water (40 °C), grape vinegar (6% acetic acid), grape vinegar + water, cold tap water (20 °C), lemon juice, baking soda water, grape vinegar (8% acetic acid), filtered mint water and grape vinegar (4% acetic acid), respectively. It was concluded that some of the solutions used in this study can significantly reduce exposure to pesticides for consumers.

The potential of mitigating greenhouse gas emissions from urban domestic water systems in highly urbanized areas

In highly urbanized areas, domestic water consumption and wastewater discharge are affected by several dynamic factors, such as economy, population, and environment, which further influence the greenhouse gas (GHG) mitigation potential of urban domestic water systems (UDWSs). To analyze GHG emission features of the UDWSs and their interactions with urban economic development, a hybrid approach of correlation analysis and a programming model was incorporated in a life-cycle framework to provide decision-making support for GHG mitigation strategies in the UDWSs. To verify the applicability of the method, Shenzhen city in Guangdong Province was chosen to analyze the potential of the UDWS for mitigating GHG emissions. The GHG emissions from the UDWS in Shenzhen was 747.82 kt CO2 eq in 2020. Compared with 2020, domestic water consumption would increase by 11.35 % and 18.67 % in 2025 and 2030, and wastewater discharge would increase by 12.88 % and 19.73 % in 2025 and 2030, respectively. In the trend of socio-economic development, the amount of water demand and wastewater discharge of urban residents would increase by 11.49 % to 18.75 % and 12.88 % to 19.75 % from 2020 to 2030, respectively. Optimum strategies of technologies for wastewater treatment and energy mix for electricity generation were obtained, with consideration of GHG mitigation goals in the future. As energy consumption contributed more than 25 % of GHG emissions in the USDWs of Shenzhen, the contributions of new energy sources for electricity production (i.e., offshore wind, solar photovoltaic, biomass, and nuclear) would increase by 0.58–1.02 times and 0.68–1.20 times from 2020 to 2025 and 2025 to 2030, respectively. The capacity of wastewater treatment would increase by 53.33 % to 80.00 % and 27.44 % to 29.82 % of the SBR and AAO technologies, respectively. Thus, it is suggested that decision makers should pay close attention to optimizing energy mix of electricity production.

Molecular screening and characterization of Legionella pneumophila associated free-living amoebae in domestic and hospital water systems

Free-living amoebae are ubiquitous in the environment and cause both opportunistic and non-opportunistic infections in humans. Some genera of amoebae are natural reservoirs of opportunistic plumbing pathogens, such as Legionella pneumophila. In this study, the presence of free-living amoebae and Legionella was investigated in 140 water and biofilm samples collected from Australian domestic (n = 68) and hospital water systems (n = 72). Each sample was screened in parallel using molecular and culture-based methods. Direct quantitative polymerase chain reaction (qPCR) assays showed that 41% samples were positive for Legionella, 33% for L. pneumophila, 11% for Acanthamoeba, and 55% for Vermamoeba vermiformis gene markers. Only 7% of samples contained culturable L. pneumophila serogroup (sg)1, L. pneumophila sg2-14, and non-pneumophila Legionella. In total, 69% of samples were positive for free-living amoebae using any method. Standard culturing found that 41% of the samples were positive for amoeba (either Acanthamoeba, Allovahlkampfia, Stenamoeba, or V. vermiformis). V. vermiformis showed the highest overall frequency of occurrence. Acanthamoeba and V. vermiformis isolates demonstrated high thermotolerance and osmotolerance and strong broad spectrum bacteriogenic activity against Gram-negative and Gram-positive bacteria. Importantly, all Legionella positive samples were also positive for amoeba, and this co-occurrence was statistically significant (p < 0.05). According to qPCR and fluorescence in situ hybridization, V. vermiformis and Allovahlkampfia harboured intracellular L. pneumophila. To our knowledge, this is the first time Allovahlkampfia and Stenamoeba have been demonstrated as hosts of L. pneumophila in potable water. These results demonstrate the importance of amoebae in engineered water systems, both as a pathogen and as a reservoir of Legionella. The high frequency of gymnamoebae detected in this study from Australian engineered water systems identifies an issue of significant public health concern. Future water management protocols should incorporate treatments strategies to control amoebae to reduce the risk to end users.