Influence of Hot Water Temperature and Use Patterns on Microbial Water Quality in Building Plumbing Systems

Although many guidance documents have been developed to inform the design and operation of building water systems to ensure safe water quality, there is a lack of consensus on some topics. This study interviewed 22 subject matter experts (SMEs) to identify topics of concern for managing water quality in buildings and compared SME views with information available on these topics in 15 systematically screened important guidance documents. The study found 18 design and 11 operational topics as critical for managing water quality in buildings. No one guidance document addressed all these topics, suggesting that a compendium of available guidance is needed. SMEs most frequently recommended temperature and residual disinfectant measurements as good parameters for monitoring overall building water quality. Both SME and guidance document recommendations for temperature for controlling opportunistic pathogen growth were reasonably consistent with water heater setpoint >60 °C. However, hot water temperature recommendations varied between 50 and 55 °C for other locations (i.e., the water temperature at the tap or end of the return loop). On the contrary, recommendations for disinfectant residual levels (0.2–2.0 mg/L), flushing frequency (1–14 days), and allowable time for hot water to reach the tap (10–60 s) were not consistent. While this study was able to reconcile diverging views on some of the water quality topics, such as identifying common guidance for water heater set point to at least 60 °C, it also highlights lack of definitive guidance on other critical topics, such as residual level, flushing frequency, hot water time to tap, and the use of thermostatic mixing valves, indicating that these are significant knowledge gaps that need further investigation. The study concludes that there is a need for developing evidence-based guidance, particularly on the topics where expert opinions diverged.

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Long-term changes in microbial water quality indicators in a hydro-power plant reservoir: The role of natural factors and socio-economic changes

AMBIO ◽

10.1007/s13280-020-01470-1 ◽

2021 ◽

Author(s):

Gunta Spriņġe ◽

Māris Bērtiņš ◽

Lesya Gnatyshyna ◽

Ilga Kokorīte ◽

Agnese Lasmane ◽

...

Keyword(s):

Water Quality ◽

Power Plant ◽

Hydro Power ◽

Microbial Water Quality ◽

Economic Changes ◽

Water Quality Indicators ◽

Natural Factors ◽

Long Term Changes

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Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

Energies ◽

10.3390/en14164741 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4741

Author(s):

María Gasque ◽

Federico Ibáñez ◽

Pablo González-Altozano

Keyword(s):

Experimental Data ◽

Water Temperature ◽

Temperature Profile ◽

Storage Tank ◽

Water Storage ◽

Hot Water ◽

Experimental Temperature ◽

Inlet Temperature ◽

Water Storage Tank ◽

Minimum Number

This paper demonstrates that it is possible to characterize the water temperature profile and its temporal trend in a hot water storage tank during the thermal charge process, using a minimum number of thermocouples (TC), with minor differences compared to experimental data. Four experimental tests (two types of inlet and two water flow rates) were conducted in a 950 L capacity tank. For each experimental test (with 12 TC), four models were developed using a decreasing number of TC (7, 4, 3 and 2, respectively). The results of the estimation of water temperature obtained with each of the four models were compared with those of a fifth model performed with 12 TC. All models were tested for constant inlet temperature. Very acceptable results were achieved (RMSE between 0.2065 °C and 0.8706 °C in models with 3 TC). The models were also useful to estimate the water temperature profile and the evolution of thermocline thickness even with only 3 TC (RMSE between 0.00247 °C and 0.00292 °C). A comparison with a CFD model was carried out to complete the study with very small differences between both approaches when applied to the estimation of the instantaneous temperature profile. The proposed methodology has proven to be very effective in estimating several of the temperature-based indices commonly employed to evaluate thermal stratification in water storage tanks, with only two or three experimental temperature data measurements. It can also be used as a complementary tool to other techniques such as the validation of numerical simulations or in cases where only a few experimental temperature values are available.

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Seasonal Succession of Bacterial Communities in Three Eutrophic Freshwater Lakes

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18136950 ◽

2021 ◽

Vol 18 (13) ◽

pp. 6950

Author(s):

Bin Ji ◽

Cheng Liu ◽

Jiechao Liang ◽

Jian Wang

Keyword(s):

Water Quality ◽

Surface Water ◽

Water Temperature ◽

Bacterial Communities ◽

Seasonal Succession ◽

Lake Eutrophication ◽

Urban Lake ◽

Freshwater Lakes ◽

Functional Prediction ◽

Bacterial Indicator

Urban freshwater lakes play an indispensable role in maintaining the urban environment and are suffering great threats of eutrophication. Until now, little has been known about the seasonal bacterial communities of the surface water of adjacent freshwater urban lakes. This study reported the bacterial communities of three adjacent freshwater lakes (i.e., Tangxun Lake, Yezhi Lake and Nan Lake) during the alternation of seasons. Nan Lake had the best water quality among the three lakes as reflected by the bacterial eutrophic index (BEI), bacterial indicator (Luteolibacter) and functional prediction analysis. It was found that Alphaproteobacteria had the lowest abundance in summer and the highest abundance in winter. Bacteroidetes had the lowest abundance in winter, while Planctomycetes had the highest abundance in summer. N/P ratio appeared to have some relationships with eutrophication. Tangxun Lake and Nan Lake with higher average N/P ratios (e.g., N/P = 20) tended to have a higher BEI in summer at a water temperature of 27 °C, while Yezhi Lake with a relatively lower average N/P ratio (e.g., N/P = 14) tended to have a higher BEI in spring and autumn at a water temperature of 9–20 °C. BEI and water temperature were identified as the key parameters in determining the bacterial communities of lake water. Phosphorus seemed to have slightly more impact on the bacterial communities than nitrogen. It is expected that this study will help to gain more knowledge on urban lake eutrophication.

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Relative Performance of 1-D Versus 3-D Hydrodynamic, Water-Quality Models for Predicting Water Temperature and Oxygen in a Shallow, Eutrophic, Managed Reservoir

Water ◽

10.3390/w13010088 ◽

2021 ◽

Vol 13 (1) ◽

pp. 88

Author(s):

Xiamei Man ◽

Chengwang Lei ◽

Cayelan C. Carey ◽

John C. Little

Keyword(s):

Water Quality ◽

Water Temperature ◽

Water Quality Model ◽

Relative Performance ◽

Bubble Plume ◽

Quality Model ◽

Quality Models ◽

Management Interventions ◽

Water Quality Models ◽

D Model

Many researchers use one-dimensional (1-D) and three-dimensional (3-D) coupled hydrodynamic and water-quality models to simulate water quality dynamics, but direct comparison of their relative performance is rare. Such comparisons may quantify their relative advantages, which can inform best practices. In this study, we compare two 1-year simulations in a shallow, eutrophic, managed reservoir using a community-developed 1-D model and a 3-D model coupled with the same water-quality model library based on multiple evaluation criteria. In addition, a verified bubble plume model is coupled with the 1-D and 3-D models to simulate the water temperature in four epilimnion mixing periods to further quantify the relative performance of the 1-D and 3-D models. Based on the present investigation, adopting a 1-D water-quality model to calibrate a 3-D model is time-efficient and can produce reasonable results; 3-D models are recommended for simulating thermal stratification and management interventions, whereas 1-D models may be more appropriate for simpler model setups, especially if field data needed for 3-D modeling are lacking.

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Simulating Diurnal Variations of Water Temperature and Dissolved Oxygen in Shallow Minnesota Lakes

Water ◽

10.3390/w13141980 ◽

2021 ◽

Vol 13 (14) ◽

pp. 1980

Author(s):

Bushra Tasnim ◽

Jalil A. Jamily ◽

Xing Fang ◽

Yangen Zhou ◽

Joel S. Hayworth

Keyword(s):

Water Quality ◽

Dissolved Oxygen ◽

Water Temperature ◽

Shallow Lakes ◽

Quality Model ◽

Lake Water Quality ◽

Ecological Processes ◽

Turbulent Diffusion Coefficient ◽

Hourly Data ◽

Mean Square Errors

In shallow lakes, water quality is mostly affected by weather conditions and some ecological processes which vary throughout the day. To understand and model diurnal-nocturnal variations, a deterministic, one-dimensional hourly lake water quality model MINLAKE2018 was modified from daily MINLAKE2012, and applied to five shallow lakes in Minnesota to simulate water temperature and dissolved oxygen (DO) over multiple years. A maximum diurnal water temperature variation of 11.40 °C and DO variation of 5.63 mg/L were simulated. The root-mean-square errors (RMSEs) of simulated hourly surface temperatures in five lakes range from 1.19 to 1.95 °C when compared with hourly data over 4–8 years. The RMSEs of temperature and DO simulations from MINLAKE2018 decreased by 17.3% and 18.2%, respectively, and Nash-Sutcliffe efficiency increased by 10.3% and 66.7%, respectively; indicating the hourly model performs better in comparison to daily MINLAKE2012. The hourly model uses variable hourly wind speeds to determine the turbulent diffusion coefficient in the epilimnion and produces more hours of temperature and DO stratification including stratification that lasted several hours on some of the days. The hourly model includes direct solar radiation heating to the bottom sediment that decreases magnitude of heat flux from or to the sediment.

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Investigation on the Flow of Groundwater Around Kamioosu Dam at the Time of Initial Filling by Using Water Quality and Water Temperature.

Doboku Gakkai Ronbunshu ◽

10.2208/jscej.1997.579_177 ◽

1997 ◽

pp. 177-189

Author(s):

Isao Shiozaki ◽

Akio Murakami ◽

Hiroyuki Taniguchi ◽

Yasuhiro Kawakami ◽

Hisashi Imai

Keyword(s):

Water Quality ◽

Water Temperature

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A square grid model for assessing the effect of alternative land uses on water quality

Canadian Journal of Civil Engineering ◽

10.1139/l76-021 ◽

1976 ◽

Vol 3 (2) ◽

pp. 209-218 ◽

Cited By ~ 1

Author(s):

Thomas W. Constable ◽

Nicholas Kouwen ◽

Shully I. Solomon

Keyword(s):

Water Quality ◽

Land Use ◽

Water Quantity ◽

Preliminary Design ◽

Land Use Patterns ◽

Time Intervals ◽

Square Grid ◽

Use Patterns ◽

Grid Technique ◽

Artificial Ponds

A mathematical model has been developed which can aid in assessing the effect of the modification of land use patterns on the water quantity and water quality regime of a watershed. The basin under study is divided into a number of elements using a square grid technique. The hydrologic and water quality components are evaluated at each element in the basin at successive time intervals, and flows are routed through the elements by use of a streamflow network system. The model can be used to assist in evaluating the effects of alternative land use configurations in a watershed, such as urbanization, the removal or growth of forests, the construction of dams, etc., on water quantity and water quality. It can also be used in the preliminary design of an urbanized area to estimate the size of storm sewers, artificial ponds, etc.

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