Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detr...Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water（Lake Huron） with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal,reports of skin rashes have sparked questions surrounding tap water in some Flint homes.This study investigated the presence of contaminants, including disinfection by-products（DBPs）, in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water.Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible.展开更多
The cement mortar lining(CML)of commonly used ductile iron pipes can severely deteriorate the drinking water quality at the initial stage of use,but the behavioral characteristics of different elements release from th...The cement mortar lining(CML)of commonly used ductile iron pipes can severely deteriorate the drinking water quality at the initial stage of use,but the behavioral characteristics of different elements release from the CML in this stage is still unclear.In this study,dynamic immersion experiments with new cement mortar lined ductile iron pipe reactors were conducted under different feed water hardness and alkalinity conditions.The results showed that the release of alkaline substances from the CML at the initial stage of use could strongly influence the pH of water,which consequently greatly impacted the release/precipitation behaviors of calcium,aluminum and silicon.The pH and aluminum concentration of the effluent water could reach 11.5 and 700μg/L within 24 hr of hydraulic retention time,respectively,under conditions of relatively lower hardness and alkalinity.Due to the pH elevation,calcium carbonate precipitation could occur even at much lower feed water alkalinity.Whereas the aluminum and silicon could keep release from the CML in soluble form at different hardness and alkalinity levels,and their release rate depended on the amount of calcium carbonate precipitation.Thus,aluminum and silicon were more suitable as indicators of the corrosion intensity at the initial stage of CML use rather than the traditional calcium carbonate precipitation potential.Appropriate feed water hardness and alkalinity levels for mitigating the initial intense corrosion of CML were proposed:hardness>40 mg/L(CaCO_(3)),alkalinity>100 mg/L(CaCO_(3)).展开更多
The system of stakeholders impacting water heater selection decisions in the U.S.is complex,with numerous actors and key players engaging with varying degrees of information asymmetry.The limited availability of decis...The system of stakeholders impacting water heater selection decisions in the U.S.is complex,with numerous actors and key players engaging with varying degrees of information asymmetry.The limited availability of decision-making tools could lead to unintended consequences of water and energy saving decisions on public health,such as the growth of opportunistic pathogens in water systems.We use a qualitative meta-synthesis to identify key stakeholders,map interactions among these stakeholders,identify decisions,roles,and influences,and inventory potential interventions.This study identifies and characterizes the important attributes of the residential water heater stakeholder system(leverage points)that influence the selec-tion of water heating technologies.The ultimate desired outcome of the work is to facilitate the selection of water heating components and design configurations that meet occupant objectives and constraints while limiting the potential for health and safety risks due to scalding or opportunistic pathogens.This effort identifies a clear need for decision-making support tools for selecting residential water heaters,one that takes a whole-systems perspective in the water heater stakeholder system and takes advantage of key leverage points for effective intervention.展开更多
Hot water recirculation systems(RECIRC)are labeled green and are sometimes mandated in local plumbing codes.Previous work conducted under non-optimized operation schemes demonstrated that these systems actually waste ...Hot water recirculation systems(RECIRC)are labeled green and are sometimes mandated in local plumbing codes.Previous work conducted under non-optimized operation schemes demonstrated that these systems actually waste energy and water versus standard(STAND)water heater counterparts.Optimization of RECIRC system operation by minimizing pump operation did improve energy efficiency 6-60%,saving consumers 5-140%annually in associated utility costs.However,STAND systems were still more energy efficient than any of the RECIRC systems.With respect to factors that might influence pathogen growth,reducing RECIRC pump operations increased disinfectant residual by as much as 560%as compared to the baseline RECIRC system;however,STAND systems still had 25-250%more total chlorine residual than any of the RECIRC systems.At 60℃operating temperature,STAND systems have 30-230%more volume at risk for pathogen growth(e.g.,volume with temp 37-46℃)than any of the RECIRC systems.Thus,in the context of“green”design,RECIRC systems provide a convenience to consumers in the form of nearly instant hot water,at a cost of higher capital,operating and overall energy costs.RECIRC systems have distinct advantages in controlling pathogens via thermal disinfection but disadvantages in control via secondary disinfection residual.展开更多
Electric hot water recirculation and on-demand instant hot water systems have been identified as“green”water systems due to purported energy and water savings,and some municipalities and districts even require green...Electric hot water recirculation and on-demand instant hot water systems have been identified as“green”water systems due to purported energy and water savings,and some municipalities and districts even require green systems in residences.The performance of these devices have never been rigorously tested and evaluated.This work aims to address that gap by conducting a comparative,head-to-head study evaluating energy efficiency,temperature profiles and consumer issues such as cost and quality of system for two“green”water heating systems as compared to a standard water heater.Not only did the standard system outperform the hot water recirculation system with respect to temperature profile during flushing,but the standard system also operated with 32-36%more energy efficiency.Although the recirculation system did in fact save some water at the tap,when factoring in the energy efficiency reductions and associated water demand,recirculation systems actually consumed up to 7 gallons more water per day and cost consumers more money.On-demand systems operate with virtually 100%energy efficiency,but cannot be used in many circumstances dependent on scaling and incoming water temperature,and may require expensive upgrades to home electrical systems and use of low/ultra low flow showerheads.Although additional research is necessary to better understand nuances of electric water heating in the context of the water-energy nexus,this research provides a first step for rational decision making by regulators,public health officials,manufacturers and consumers.展开更多
基金funding from the U.S.Environmental Protection Agency, Meghan Franco for assistance with XAD resin extractions, Shealy Environmental, Inc.for VOC analyses
文摘Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water（Lake Huron） with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal,reports of skin rashes have sparked questions surrounding tap water in some Flint homes.This study investigated the presence of contaminants, including disinfection by-products（DBPs）, in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water.Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible.
基金supported by the Beijing Municipal Science&Technology Program (No.Z201100008220003)the National Key R&D Program of China (No.2019YFD1100105)。
文摘The cement mortar lining(CML)of commonly used ductile iron pipes can severely deteriorate the drinking water quality at the initial stage of use,but the behavioral characteristics of different elements release from the CML in this stage is still unclear.In this study,dynamic immersion experiments with new cement mortar lined ductile iron pipe reactors were conducted under different feed water hardness and alkalinity conditions.The results showed that the release of alkaline substances from the CML at the initial stage of use could strongly influence the pH of water,which consequently greatly impacted the release/precipitation behaviors of calcium,aluminum and silicon.The pH and aluminum concentration of the effluent water could reach 11.5 and 700μg/L within 24 hr of hydraulic retention time,respectively,under conditions of relatively lower hardness and alkalinity.Due to the pH elevation,calcium carbonate precipitation could occur even at much lower feed water alkalinity.Whereas the aluminum and silicon could keep release from the CML in soluble form at different hardness and alkalinity levels,and their release rate depended on the amount of calcium carbonate precipitation.Thus,aluminum and silicon were more suitable as indicators of the corrosion intensity at the initial stage of CML use rather than the traditional calcium carbonate precipitation potential.Appropriate feed water hardness and alkalinity levels for mitigating the initial intense corrosion of CML were proposed:hardness>40 mg/L(CaCO_(3)),alkalinity>100 mg/L(CaCO_(3)).
文摘The system of stakeholders impacting water heater selection decisions in the U.S.is complex,with numerous actors and key players engaging with varying degrees of information asymmetry.The limited availability of decision-making tools could lead to unintended consequences of water and energy saving decisions on public health,such as the growth of opportunistic pathogens in water systems.We use a qualitative meta-synthesis to identify key stakeholders,map interactions among these stakeholders,identify decisions,roles,and influences,and inventory potential interventions.This study identifies and characterizes the important attributes of the residential water heater stakeholder system(leverage points)that influence the selec-tion of water heating technologies.The ultimate desired outcome of the work is to facilitate the selection of water heating components and design configurations that meet occupant objectives and constraints while limiting the potential for health and safety risks due to scalding or opportunistic pathogens.This effort identifies a clear need for decision-making support tools for selecting residential water heaters,one that takes a whole-systems perspective in the water heater stakeholder system and takes advantage of key leverage points for effective intervention.
基金support of the National Science Foundation under grant 1033498.
文摘Hot water recirculation systems(RECIRC)are labeled green and are sometimes mandated in local plumbing codes.Previous work conducted under non-optimized operation schemes demonstrated that these systems actually waste energy and water versus standard(STAND)water heater counterparts.Optimization of RECIRC system operation by minimizing pump operation did improve energy efficiency 6-60%,saving consumers 5-140%annually in associated utility costs.However,STAND systems were still more energy efficient than any of the RECIRC systems.With respect to factors that might influence pathogen growth,reducing RECIRC pump operations increased disinfectant residual by as much as 560%as compared to the baseline RECIRC system;however,STAND systems still had 25-250%more total chlorine residual than any of the RECIRC systems.At 60℃operating temperature,STAND systems have 30-230%more volume at risk for pathogen growth(e.g.,volume with temp 37-46℃)than any of the RECIRC systems.Thus,in the context of“green”design,RECIRC systems provide a convenience to consumers in the form of nearly instant hot water,at a cost of higher capital,operating and overall energy costs.RECIRC systems have distinct advantages in controlling pathogens via thermal disinfection but disadvantages in control via secondary disinfection residual.
基金support of the National Science Foundation under grant 1033498.
文摘Electric hot water recirculation and on-demand instant hot water systems have been identified as“green”water systems due to purported energy and water savings,and some municipalities and districts even require green systems in residences.The performance of these devices have never been rigorously tested and evaluated.This work aims to address that gap by conducting a comparative,head-to-head study evaluating energy efficiency,temperature profiles and consumer issues such as cost and quality of system for two“green”water heating systems as compared to a standard water heater.Not only did the standard system outperform the hot water recirculation system with respect to temperature profile during flushing,but the standard system also operated with 32-36%more energy efficiency.Although the recirculation system did in fact save some water at the tap,when factoring in the energy efficiency reductions and associated water demand,recirculation systems actually consumed up to 7 gallons more water per day and cost consumers more money.On-demand systems operate with virtually 100%energy efficiency,but cannot be used in many circumstances dependent on scaling and incoming water temperature,and may require expensive upgrades to home electrical systems and use of low/ultra low flow showerheads.Although additional research is necessary to better understand nuances of electric water heating in the context of the water-energy nexus,this research provides a first step for rational decision making by regulators,public health officials,manufacturers and consumers.
