Antibiotic resistance genes (ARGs) are extensively detected in various environmental media, whose risk assessment in the drinking water systems has not been comprehensive. This study established a ...new risk assessment of ARGs in the drinking water systems, considering the chlorine-resistance ability, transferability, and ARGs harboring potential of pathogens. The risk of ARGs in a typical drinking water reservoir was also evaluated based on the detection of ARGs and antibiotic-resistant bacteria (ARB). Fourteen ARGs were detected with a relative concentration range of 10-4–10-3 (ARGs/16S rRNA gene). Five isolated ARB were identified as human opportunistic pathogens, one of which (Pseudomonas aeruginosa HLS-6, CCTCC AB 2017269) is resistant to hundreds of milligrams per liter levels of antibiotics and low-level chlorine. This result indicated that ARB tolerant to high-levels of antibiotics could be isolated from environments containing trace levels of antibiotics. Moreover, complete genome sequencing confirmed the inclusion of ARGs (sul1, aadA2) on the class I integron in HLS-6, indicating that the risk of ARGs in this drinking water reservoir could be classified as resistance risk ranking in drinking water system 1 (R3DW 1). The risk assessment of ARGs in this study provides a clear understanding of ARG risk in drinking water systems. The results reveal that the ARGs and ARB contamination of drinking water reservoirs pose significant challenges for drinking water treatment efficiency and affect drinking water safety.
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•Sulfonamides ARGs were the dominant type.•Five isolated ARB were identified as human opportunistic pathogens.•ARB from trace-level-antibiotic environment show high-level antibiotics resistance.•A new risk assessment system of ARG in drinking water system is established.•The tolerance to chlorine is a vital factor in the risk assessment of ARGs.
The emergence of increasingly affordable variable-speed drive technology has changed the approach used to control chilled water systems equipped with these drives. The purpose of this research was to ...develop an integrated chilled water modeling technique that can determine the optimal system setpoints and estimate the energy saving potential of chiller system. The chiller system equipped with Variable Frequency Drives (VFDs) on cooling tower fans and condenser water pumps. To accomplish the objective, physical component models of the centrifugal chiller, cooling tower and condenser water pump were established with the goal of incorporating the system’s condenser water flow rate and cooling tower fan speeds as optimization variables. Furthermore, a cooling load prediction algorithm was developed using a multiple non-linear regression model to approximate the building’s cooling load subject to a range of environmental conditions. The inputs and outputs of the individual component models were linked to estimate how adjusting the cooling tower fan and condenser water pump speed would influence the system’s comprehensive performance. The overall system model was then optimized using a generalized reduced gradient optimization algorithm to determine the potential energy savings through speed control with VFDs and to ascertain a control logic strategy for the building automation system to operate the heating and cooling system. A case-study was performed on a single chiller system at a museum and the model was calibrated according to logged data collected over four months. Results showed that for the system analyzed, the energy saving of optimizing the cooling tower fan system was found to be 12–15%, while the energy saving potential of optimizing the condenser water pump with the cooling tower fan was negligible. Additionally, comparing different cooling tower fan control strategies showed that a wet-bulb approach-based cooling tower control strategy was shown to have the highest correlation to the optimized fan speed with an R2 of 0.924.
Global urbanisation will put considerable stress on both water and energy resources. While there is much research at the national and regional levels on the energy implications of water supply (the ...urban water-energy ‘nexus’), there is relatively little at the city scale. This literature is further diminished when attempting to account for the climate impact of urban water systems. A study of the urban water-energy-climate nexus is presented for México City. It is shown that 50% of México City water comes from a local aquifer with a further 30% deriving from energy-intensive surface sources which are pumped over considerable topography. The water supply system consumes 90% of the water system energy demand, and is responsible for the majority (90%) of the CO2e emissions. In the wastewater sector, 80–90% is discharged with no or little treatment, with correspondingly low energy demand. The small fraction that is treated accounts for the majority of energy use in the wastewater sector. This study shows the uncertainty in energy demand and CO2e emissions when reliant on secondary data which considerably over/under-estimate energy use compared with primary data. This has implications when assessing energy and carbon budgets. Three water savings options are assessed for their impact on energy and CO2e emissions reductions. Considerable reductions in water supply volumes and concomitant energy consumption and CO2e emissions are possible. However the extent of implementation, and the effectiveness of any implemented solutions depend on financing, institutional backing and public support. An additional measure to reduce the climate impact is to switch from traditional to renewable fuels. This work adds city-level quantification of the urban water-energy-climate nexus, allowing policy makers to discern which water-system elements are responsible for the greatest energy use and climate impact, and are better equipped to make targeted operational decisions.
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•The water system related energy use and climate impact of Mexico City is presented.•Water supply is responsible for ~90% of energy consumption in the system.•Wastewater treatment is limited with concomitant low energy/carbon impact.•Water savings measures may lead to major reductions in energy use and carbon impact.•A switch to greener energy fuels would cut carbon impacts.
Pharmaceuticals are globally consumed by humans and animals to support daily health and to treat disease. Following consumption, they may reach the aquatic environment either directly through the ...discharge of untreated wastewater to water bodies, or indirectly via treated wastewater as a result of their incomplete removal from wastewater treatment plants. This paper reviews the processes that control the occurrence and fate of pharmaceuticals in water systems, including sorption, photodegradation, hydrolysis and biodegradation. The degree to which these four processes occur is influenced by pharmaceutical types and their chemical structure as well as environmental factors such as sunlight, water depth, organic matter content, water chemistry, sediment properties, and type and abundance of microorganisms. Depending on the complex interactions of these factors, pharmaceutical compounds may be mineralized, partially degraded, or remain intact because they are resistant to degradation. Kinetic rate parameters and the half-life of a variety of pharmaceutical products are provided herein for the above processes under different environmental conditions. Usually, photodegradation and biodegradation represent dominant reaction processes, while hydrolysis only affects some pharmaceuticals, particularly antibiotics. The identified sorption and reaction rate parameters can be incorporated into a concise modeling framework to assess and predict longitudinal concentration profiles of pharmaceutical products in the manmade and natural systems, particularly when large amounts of pharmaceuticals are discharged during abnormal events such as a virus outbreak. Finally, future research is suggested, including the fate of transformed products (intermediates) in water systems.
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•A systematic view approach to probe the pharmaceuticals fate and transport was provided.•Processes of sorption, photodegradation, hydrolysis and biodegradation were reviewed.•Photo- and bio-degradation are dominant reactions for most pharmaceuticals.•Sorption and reaction kinetics rates for different environment matrix were presented.•A concise modeling framework tying every process together was designed.
Seasonal variations in water system distributions were examined in Onagawa Bay of the Sanriku area using long-term hydrographic data obtained from April 2000 to February 2017. In this study, we ...classified the waters in the bay into six water systems defined by Hanawa and Mitsudera (1987) and coastal water (CW), which appears in the nearshore region but not in the offshore region. The mode water system analysis revealed clear seasonal variations in the water system distributions in the bay, characterized by the predominance of the Tsugaru Warm Current water system in the lower layer in fall, the entire water column in winter, the Oyashio water system in the lower layer in spring, and CW in the surface layer from spring to summer. CW in the bay was less saline and/or less dense than the offshore water and mostly distributed in the surface layer from April to October, indicating that CW was formed by mixing freshwater discharged from the river with water in the bay. The relationship between surface salinity in the mouth part of Onagawa Bay and freshwater supply from the Kitakami River flowing into Oppa Bay indicated that a part of the CW in Onagawa Bay was derived from outside the bay.
This study aimed to compare the effects of four different rearing systems—namely clear water, green water, recirculating water and biofloc water systems—on survival, growth and quality of mud crab (
...Scylla paramamosain
) megalopae reared from early zoeae. Twelve 60-L plastic buckets filled with 50 L of disinfected seawater were stocked with 20 larvae of zoea 1 (Z1) L
−1
. The larvae were fed both probiotic-enriched L-strain rotifers (
Brachionus plicatilis
) and probiotic-enriched
Artemia
(
Artemia franciscana
) in all systems. After 20 days of culture, the green water system resulted in the highest survival to megalopae than all the other systems. The survival of megalopae reared under the biofloc water system was similar to that of the clear water system, but both systems exhibited higher survival than the recirculating water system. However, larval growth performance was not affected by the various rearing systems. The quality of megalopae produced under these systems was determined by ammonia and simulated transport stress tests. The ammonia stress test did not show a significant difference in the quality of megalopae, but the simulated transport stress test demonstrated a significant effect of rearing system on the quality of mud crab megalopae. The resistance to the air exposure until the end of the 48 h of transport was observed in the green water system. Overall, the results of the present study revealed that the green water system is the most suitable for rearing
Scylla paramamosain
larvae from Z1 to megalopa stage.
Abstract
Scholars and policy makers alike frequently promote drinking water system consolidation as a solution to the longstanding struggles of small water systems and the related consequences of ...service fragmentation, including vulnerability to climate change and persistent racial and economic inequalities in access to safe and affordable drinking water. Despite enthusiasm for the concept, however, our understanding of how, why, and where consolidations occur has remained stubbornly limited such that the promise of drinking water system consolidation remains theoretical at best. This study analyzes all known water system consolidations (
n
= 206) in the state of California over a 7‐year period (2015–2021). We find empirical support for certain theoretical claims about consolidation, including an overall reduction in the number of regulated systems, with the largest reductions occurring among particularly underperforming, climate‐vulnerable, and unrepresentative system types. Other findings, however, do not align with the literature on the subject. We find limited evidence of either water service privatization or remunicipalization trends and seemingly limited prospects for economies of scale benefits through consolidations. Moreover, roughly half of consolidations during the study period involve non‐residential water systems. Among the consolidated community water systems, systems serving higher‐resourced communities are overrepresented compared to those serving lower‐resourced communities by a margin of two‐to‐one. It is time to move beyond the blanket assumption of positive consolidation benefits toward a more nuanced understanding of the associated opportunities and limitations. Depending on their goals, policymakers may need to support more specific types of consolidation.
Key Points
Consolidations are reducing the number of regulated systems including among underperforming and unrepresentative system types
Consolidations occur across institutional types and typically involve very small/nonresidential systems, reducing prospects for economies of scale benefits
Residents served by consolidating and receiving systems tend to be similar but among consolidated systems, low‐resource communities are underrepresented
This paper is concerned with global existence and blow-up phenomena for an integrable two-component Camassa–Holm shallow water system. A new global existence result and several new blow-up results of ...strong solutions to the system are presented. Our obtained results for the system are sharp and improve considerably earlier results.
The widespread use of antibiotics has resulted in pollution associated with antibiotics and antibiotic resistance genes (ARGs) in urban water systems, threatening the public health and the ecological ...security. In this study, the patterns of the diversity and abundance of the antibiotics and ARGs in a typical city (Kunming, China) were analyzed by monitoring their presence in the tap water, the land block sewage discharge units, the sewage pipes, the influent of WWTP, the effluent of WWTP, and the urban river channel. The results showed that although the average concentration of total antibiotics in tap water was 10 ng/L, the concentrations reached hundreds or even thousands of ng/L in all the other sections, indicating antibiotics entering water system through human or pets discharge. The relative abundances of ARG copies to 16S rRNA gene copies in the effluent of WWTP, the urban river channel which was the downstream of WWTP were higher than those of the sewage pipes, increasing risk of ARG transfer after treatment by WWTP. In general, the relative abundance of ARGs in spring was higher than that in winter. There was no significant correlation between antibiotics concentrations and their corresponding ARGs, except for a correlation between tetracyclines and tet-resistance genes. Due to the existence of transposases, the urban water system is exposed to a widespread risk of horizontal transfer of ARGs.
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•Investigate the abundance of antibiotics and ARGs in urban water systems in China.•Concentrations reached hundreds or even thousands of ng/L in urban drainage system.•Abundance of ARGs in sewage was increased after the treatment.•Urban water system is exposed to a widespread risk of horizontal transfer of ARGs.
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