Fate of intracellular and extracellular antibiotic resistance genes in sewage sludge by full-scale anaerobic digestion.

Storage tank (ST) is a promising strategy for solid-liquid separation following anaerobic digestion (AD). However, little is known regarding the effects of ST on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and microbial communities. Therefore, this study first investigated eight typical ARGs (sul1, sul2, tetW, tetA, tetO, tetX, ermF, and ermB) and three MGEs (int1, int2, and tnpA) during full-scale AD of sludge and the liquid and biosolids phases of ST. Following that, intracellular ARGs (iARGs), extracellular polymeric substances (EPS)-associated ARGs, and cell-free ARGs removal were quantified in AD process, which is largely unknown for full-scale AD of sludge. The qPCR results showed that both AD and ST significantly removed ARGs, with ST biosolids showing the highest removal efficiency for the total measured relative (82.27 ± 2.09 %) and absolute (92.38 ± 0.89 %) abundance of ARGs compared to the raw sludge. Proteobacteria, Bacteroidota, Firmicutes and Campilobacterota were the main potential ARGs hosts in the sludge. Moreover, the results of different ARGs fractions showed that the total relative and absolute abundance of iARGs decreased by 90.12 ± 0.83 % and 79.89 ± 1.41 %, respectively, following AD. The same trend was observed for the abundance of EPS-associated ARGs, while those of cell-free ARGs increased after AD. These results underscore the risk of extracellular ARGs and provided new insights on extracellular ARGs dissemination evaluation.

Silica Aerogel-Modified Polyacrylonitrile Nanofibers to Reduce Heat Flux in Heat Storage Tanks of Greenhouse Buildings.

Polyacrylonitrile (PAN) nanofibers have specific characteristics such as thermal insulation, weatherproofing, and sunlight resistance and therefore are appropriate to be applied as insulation materials for various industries, especially in greenhouse construction. The heat source in greenhouse buildings that operate independently in the heating network comes from heat storage tanks. In the present study, employing thermal field numerical simulations, we investigate the heat flux of a cylindrical heat storage tank with silica aerogel-modified PAN nanofibers as thermal insulation materials. The geometric scale of the tank body, thermal insulation material thickness, and outdoor temperature are optimized to improve thermal insulation. The significant discrepancy in heat flux at different parts of the heat storage tank leads to the extreme heat flux arising at the water-gas interface on the inner and outer walls. It is indicated that the heat flux distribution can be effectively ameliorated by modifying the scale of the tank body to retain the overall water temperature. In particular, effective insulation can merely be acquired when the thermal conductivity of the insulation material is below 3.3 W·m-1·K-1. Eventually, the heat storage tank is optimized to store 1400 L water at 100 °C with a radius of 0.6 m and a thermal insulation thickness of 50 mm at an outdoor temperature of -10 °C, which can maintain excellent thermal insulation for 8 and 24 h at 87.7 and 69.9 °C, respectively.

Research on a Corrosion Detection Method for Oil Tank Bottoms Based on Acoustic Emission Technology.

This paper presents an acoustic emission (AE) detection method for refined oil storage tanks which is aimed towards specialized places such as oil storage tanks with high explosion-proof requirements, such as cave oil tanks and buried oil tanks. The method utilizes an explosion-proof acoustic emission instrument to detect the floor of a refined oil storage tank. By calculating the time difference between the defective acoustic signal and the speed of acoustic wave transmission, a mathematical model is constructed to analyze the detected signals. An independent channel AE detection system is designed, which can store the collected data in a piece of independent explosion-proof equipment, and can analyze and process the data in a safe area after the detection, solving the problems of a short signal acquisition distance and the weak safety protection applied to traditional AE instruments. A location analysis of the AE sources is conducted on the bottom plate of the tank, evaluating its corrosion condition accurately. The consistency between the evaluation and subsequent open-tank tests confirms that using AE technology effectively captures corrosion signals from oil storage tanks' bottoms. The feasibility of carrying out online inspection under the condition of oil storage in vertical steel oil tanks was verified through a comparison with open inspections, which provided a guide for determining the inspection target and opening order of large-scale oil tanks.

Enhancement of solar evacuated tube unit filled with nanofluid implementing three lobed storage unit equipped with fins.

This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.

Coupling simulation of pipeline nodes - Storage tank linkage in urban high-density built-up areas using optimization model.

Climate change and urbanization contribute to the increased frequency of short-duration intense rainstorms. Traditional solutions often involve multiple scenarios for cost-effectiveness comparison, neglecting the rationality of placement conditions. The effective coupling and coordination of the location, number, size, and cost of storage tanks are crucial to addressing this issue. A three-phase approach is proposed to enhance the dynamic link between drainage pipeline and storage tanks in urban high-density built-up areas, integrating Python language, SWMM, the Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-III), and the Analytic Hierarchy Process (AHP) methods. In the first stage, each node within the pipeline network is considered as a potential storage tank location. In the second stage, factors such as the length and diameter of the upstream connecting pipeline, as well as the suitability of the storage tank location, are assessed. In the third stage, the length and diameter of the downstream connecting pipeline node are evaluated. The results show that the 90 overflow nodes (overflow time >0.5h) have been cleared using the three-phase approach with a 50a (duration = 3h) return period as the rainfall scenario, which meets the flooding limitations. After the completion of the three-phase method configuration, the total overflow and SS loads were reduced by 96.45% and 49.30%, respectively, compared to the status quo conditions. These two indicators have decreased by 48.16 and 9.05%, respectively, compared to the first phase (the traditional method of only replacing all overflow nodes with storage tanks). The proposed framework enables decision-makers to evaluate the acceptability and reliability of the optimal management plan, taking into account their preferences and uncertainties.

Using fuzzy cognitive map in bow tie method for dynamic risk assessment of spherical storage tanks: A case study.

The present study aimed to perform a dynamic risk assessment of liquefied petroleum gas (LPG) in spherical storage tanks using the Hazard and Operability (HAZOP) method. The "LPG release from spherical storage tank" scenario was determined to be a top event based on the risk level. The causes and consequences of this scenario were then specified using the Bow-Tie method. Additionally, fuzzy cognitive mapping (FCM) was utilized to identify the most critical threats, consequences, and effective barriers in a dynamic approach. Results showed that fracture/rupture in pipelines/a storage tank due to fire had the highest output degree and was identified as the most influential threat in the occurrence of the LPG release. Fatality/injury due to fire and explosion had the highest input degree and was more influenced by the release of LPG as the main consequence in the selected scenario. The findings of this study enabled us to make a logical decision about effective barriers for avoiding and minimizing the release of LPG and its threats and consequences based on the fuzzy cognitive map. Moreover, the results of this study showed that the FCM method could determine the most critical nodes with a higher degree and represent their relationships.

Study on tank damage and response of adjacent tanks in full time domain of detonation.

The flammable gas volatilized from the storage medium in the tank will burn and explode under the action of an accidental ignition source. Tank explosions formed by the explosive shock wave, explosive debris will not only cause their own damage, but also on the safe operation of adjacent tanks to form a threat. Therefore, in this paper, the vertical dome roof tank is taken as the research object, the criteria of brittle fracture failure of tank materials are constructed, and the multi-field coupling calculation model of tank detonation based on TNT equivalent method is established, taking into account the fluid properties inside and outside the tank, the structure of implosion tank and adjacent tank. By analyzing the full time domain process of gas detonation in tanks under different influence factors, the response to implosion damage of tanks and adjacent tanks under the action of explosion shock wave overpressure and debris was obtained. With the increase of the liquid level, the overpressure and deformation of the shock wave of the detonation tank and adjacent tank decrease, and the type and number of fragments decrease. With the increase of the volume of the tank, the overpressure and stress of the shock wave become larger, the strain rate of the tank becomes larger, and brittle failure is more likely to occur. The types and number of fragments formed increase, but detonation fragments are not formed when the tank is full. The research results in this paper provide a theoretical basis and calculation method for preventing and controlling tank implosion accidents, as well as tank design and tank spacing layout.

Novel custom-made design and analysis of hydrogen PEM fuel cell for high endurance small UAV applications.

The purpose of this paper is to propose a new methodology to devise a custom-made hydrogen-based proton-exchange membrane fuel cell (PEMFC) system for a class of experimental fixed-wing small unmanned aerial vehicles (SUAVs). The proposed fuel cell provides three times higher flight endurance than the conventional battery-based powertrain. The chosen SUAV represents a class of high-altitude UAVs, having an operational altitude of 4500 m (14,760ft), cruising speed of 12-20 m/s (39.4-65.6 ft/s), take-off weight of 4 kg, wing-span of 1.61 m (5.28 ft) and battery-powered flight endurance of 1 h. The characteristic parameters and design configurations of the fuel cell are determined by employing the first principles of electrochemistry and thermodynamics. Corresponding simulations are performed using popular development tools like MATLAB/Simulink. The vital results in the form of - polarization and power curves for fuel cells, against the current density are obtained, which are further narrowed down to meet the target power requirements for determining the size of the hydrogen storage tank. The paper also comments on the auxiliary systems and fuel cell powertrain for SUAVs. Finally, the design efficiency of 54% for the fuel cell is achieved with respect to equivalent voltage for heating value with the calculated hydrogen storage tank size of 5.688 ls. This yields three times higher flight endurance as compared to the flight time found in literature for the same class of SUAVs.

Some thoughts on integrity management of mounded storage tanks.

In the domestic petrochemical industry, mounded storage tanks (MSTs) are widely used to store hazardous chemicals. The shell of the mounded storage tank is completely covered by soil to effectively mitigate the effect of the external environment and prevent thermal-expansion-induced explosion of the stored material. Because mounded storage tanks are mostly underground, they are highly safe, provide effective land utilization, and are highly energy efficient. Furthermore, the impact radius in case of an explosion is less than that of aboveground tanks. However, adequate regulations and standards for safety management are yet to be established. This study established a novel method for the integrity management of mounded storage tanks through database construction, risk assessment, applicability monitoring, and testing. At the same time, the risk assessment method for mounded storage tank characteristics is constructed for the first time.

Structural Health Monitoring of Chemical Storage Tanks with Application of PZT Sensors.

Chemical pressure storage tanks are containers designed to store fluids at high pressures, i.e., their internal pressure is higher than the atmospheric pressure. They can come in various shapes and sizes, and may be fabricated from a variety of materials. As aggressive chemical agents stored under elevated pressures can cause significant damage to both people and the environment, it is essential to develop systems for the early damage detection and the monitoring of structural integrity of such vessels. The development of early damage detection and condition monitoring systems could also help to reduce the maintenance costs associated with periodic inspections of the structure and unforeseen operational breaks due to unmonitored damage development. It could also reduce the related environmental burden. In this paper, we consider a hybrid material composed of glass-fiber-reinforced polymers (GFRPs) and a polyethylene (PE) layer that is suitable for pressurized chemical storage tank manufacturing. GFRPs are used for the outer layer of the tank structure and provides the dominant part of the construction stiffness, while the PE layer is used for protection against the stored chemical medium. The considered damage scenarios include simulated cracks and an erosion of the inner PE layer, as these can be early signs of structural damage leading to the leakage of hazardous liquids, which could compromise safety and, possibly, harm the environment. For damage detection, PZT sensors were selected due to their widely recognized applicability for the purpose of structural health monitoring. For sensor installation, it was assumed that only the outer GFRP layer was available as otherwise sensors could be affected by the stored chemical agent. The main focus of this paper is to verify whether elastic waves excited by PZT sensors, which are installed on the outer GFRP layer, can penetrate the GFRP and PE interface and can be used to detect damage occurring in the inner PE layer. The efficiency of different signal characteristics used for structure evaluation is compared for various frequencies and durations of the excitation signal as well as feasibility of PZT sensor application for passive acquisition of acoustic emission signals is verified.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks.

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Development of rapid and effective oil-spill response system integrated with oil collection, recovery and storage devices for small oil spills at initial stage: From lab-scale study to field-scale test.

In the present study, through the laboratory-to-field scale experiments and trials, we report the development and evaluation of an integrated oil-spill response system capable of oil collection, recovery (separation), and storage, for a timely and effective response to the initial stage of oil-spill accidents. With the laboratory-scale experiments, first, we evaluate that the water-surface waves tend to abate the oil recovery rate below 80% (it is above 95% for the optimized configuration without the waves), which is overcome by installing the hydrophilic (and oleophobic) porous structures at the inlet and/or near the water outlet of the separator. In the follow-up meso-scale towing tank tests with a scaled-up prototype, (i) we optimize the maneuverability of the assembled system depending on the speed and existence of waves, and (ii) evaluate the oil recovery performance (more than 80% recovery for the olive oil and Bunker A fuel oil). Although more thorough investigations and improvements are needed, a recovery rate of over 50% can be achieved for the newly enforced marine fuel oil (low sulfur fuel oil, LSFO) that was not targeted at the time of development. Finally, we perform a series of field tests with a full-scale system, to evaluate the rapid deployment and operational stability in the real marine environment. The overall floating balance and coordination of each functional part are sustained to be stable during the straight and rotary maneuvers up to the speed of 5 knots. Also, the collection of the floating debris (mimicking the spilled oil) is demonstrated in the field test. The present system is now being tested by the Korea Coast Guard and we believe that it will be very powerful to prevent the environmental damage due to the oil spills.

Methane emission rates averaged over a year from ten farm-scale manure storage tanks.

Methane (CH4) emissions from animal manure stored in outdoor tanks are difficult to predict because of several influencing factors. In this study, the tracer gas dispersion method (TDM) was used to quantify CH4 emissions from ten manure storage tanks, along with the collection of supporting information, in order to identify its emission drivers. The dataset included two tanks storing dairy cattle manure, six holding pig manure, and two with digestate from manure-based biogas plants. CH4 emissions from the tanks were measured six to 14 times over a year. Emissions varied from 0.02 to 14.30 kg h-1, or when normalised by the volume of manure stored, emission factors (EFs) varied from 0.05 to 11 g m-3 h-1. Annual average CH4 EFs varied greatly between the tanks, ranging from 0.20 to 2.75 g m-3 h-1. Normalised EFs are similar to literature values for cattle and digested manure, but at the high end of the interval for pig manure. The averaged manure temperature for all tanks varied from 10.6 to 16.4 °C, which was higher than reported in a previous Danish study. Volatile solids (VS) concentration was in average higher for cattle manure (ranging from 3.1 and 4.4 %) than pig manure (ranging from 1.0 to 3.6 %). CH4 emission rates were positively correlated with manure temperature, whereas this was not the case for VS concentration. Annual average EFs were higher for pig than for cattle manure (a factor of 2.5), which was greater than digested manure emissions (a factor of 1.2). For the pig manure storage tanks, CH4 emissions were higher for covered tanks than for uncovered tanks (by a factor of 2.3). In this study, manure storage tanks showed a large disparity in emission rates, driven not only by physical factors, but also by farm management practices.

Sludge interface measurement in the storage tank utilizing neutron backscattering technique: A field experiment.

Modern industrial plant operations commonly necessitate a measurement system of the liquids level interface in the oil storage tank. Various advanced-level indicators almost meet the demand, but these may not be in online condition and are less accurate due to sedimentation in the bottom tank. Sedimentation or sludge known as a petroleum hydrocarbons complex emulsion, contained water and solid particles generated during distribution, storage, or even production. The neutron backscatter technique can help the maintenance system of the tank or vessel by measuring sludge levels from outside the wall. This paper presents a non-intrusive method for identifying the interface between two materials in the crude oil storage system. A fast neutron source (241Am-Be) with activity 1 Ci (Ci) and a portable backscattering neutron detector are used for storage tank measurement. The storage tank has an outer diameter (OD) of 34 m and a height of 11 m. Time measurement is 2 s for each position, starting from 0 m to 11 m. The slow neutron intensity can be correlated to the hydrogen concentration inside chemical compounds. The interface between sludge and oil is identified at 27 cm from the bottom plate. The method has the potential for non-destructive measurement of sludge in a refinery facility.

Review of Decompression Damage of the Polymer Liner of the Type IV Hydrogen Storage Tank.

The type IV hydrogen storage tank with a polymer liner is a promising storage solution for fuel cell electric vehicles (FCEVs). The polymer liner reduces the weight and improves the storage density of tanks. However, hydrogen commonly permeates through the liner, especially at high pressure. If there is rapid decompression, damage may occur due to the internal hydrogen concentration, as the concentration inside creates the pressure difference. Thus, a comprehensive understanding of the decompression damage is significant for the development of a suitable liner material and the commercialization of the type IV hydrogen storage tank. This study discusses the decompression damage mechanism of the polymer liner, which includes damage characterizations and evaluations, influential factors, and damage prediction. Finally, some future research directions are proposed to further investigate and optimize tanks.

Performance of a superamphiphobic self-cleaning passive subambient daytime radiative cooling coating on grain and oil storage structures.

The thermal performance of a novel exterior coating material for commonly used grain and food-grain oil structures was investigated. Grain structures included a concrete squat silo and a concrete warehouse while the edible oil structure was a concrete sided tank. The exterior coating provided excellent moisture runoff and solar reflectance properties and is best described as a superamphiphobic self-cleaning passive subambient daytime radiative cooling (SSC-PSDRC) coating. The coating exhibited a remarkable subambient daytime cooling effect in various structures in different climatic regions. Compared with the roof surface temperatures of a cool white-coated concrete grain silo and a gray carbon iron-based edible oil storage tank, those of the PSDRC coated top surfaces could be reduced by 37 °C and 33 °C, respectively. The roof surface temperature of a warehouse painted with a cool-white coating-with a solar reflectance of 0.9 and an emissivity of 0.85-and that of a warehouse with the roof installed with aluminised polymer waterproof membranes were 19 °C and 18 °C higher than that of the PSDRC warehouse, respectively. Consequently, the interior temperature of the wheat pile in the PSDRC grain silo was 10 °C lower than that in the control squat silo. With the inner loop flow temperature control system operating, the interior air temperatures of the PSDRC west-facing separate space were 6 °C and 3 °C higher than those of the cool-white coated and control west-facing separate spaces, respectively. Even after the application of PSDRC coating for only a few days, the interior air temperature of the PSDRC oil storage tank was reduced by 38 °C, and the interior temperature of the oil storage tank was reduced by 4 °C. Furthermore, in practical applications, the coating showed impressive superamphiphobic self-cleaning capabilities and super aging resistance. The wide applications of the coating would have far-reaching, global implications for maintaining grain and edible oil products, particularly in the sub-tropical climates.

Simulation on Heat Transfer and Emergency Protection of Tanks in a Tank Farm under Fire Scenario.

It is very important to understand the heat transfer process between storage tanks in a tank farm under a fire scenario, which is one of the key factors in determining the consequences of accident development. In this paper, a CFD simulation is used to study the heat transfer process and emergency protection of tanks under a fire scenario. The simulated results show that the changes in wind speed can affect the heat transfer of the tank farm. The highest temperature of the tanks at 5.3 m/s (wind speed) is 1432 K, while the highest temperature at 17.1 m/s (wind speed) is 1556 K. At the same time, the changes in wind direction can also affect the heat transfer of the tank farm. For the 45° east by north (wind direction), almost all tanks in the tank farm are affected by the fire. When the water curtain was applied as an emergency protection measure, the simulated highest temperature of the tanks decreased to 779 K (the cooling water intensity 6 L/min·m2), while the highest temperature of the tanks was 1432 K without water curtain protection under the actual fire conditions. The simulated highest temperature of the tanks decreased to 671 K when the emergency thermal insulation coating was sprayed on the surface of the tanks, which can effectively protect the adjacent tanks from being destroyed.

Exploring the association of Brownfield remediation status with socioeconomic conditions in Wayne County, MI.

Urban neighborhoods with locations of environmental contamination, known as brownfields, impact entire neighborhoods, but corrective environmental remedial action on brownfields is often tracked on an individual property basis, neglecting the larger neighborhood-level impact. This study addresses this impact by examining spatial differences between brownfields with unmitigated environmental concerns (open site) and sites that are considered fully mitigated or closed in urban neighborhoods (closed site) on the US census tract scale in Wayne County, MI. Michigan's Department of Environment, Great Lakes, and Energy's leaking underground storage tank (LUST) database provided brownfield information for Wayne County. Local indicators of spatial association (LISA) produced maps of spatial clustering and outliers. A McNemar's test demonstrated significant discordances in LISA categories between LUST open and closed sites (p < 0.001). Geographically weighted regressions (GWR) evaluated the association between open and closed site spatial density (open-closed) with socioeconomic variables (population density, proportion of White or Black residents, proportion of college educated populations, the percentage of owner-occupied units, vacant units, rented units, and median household value). Final multivariate GWR showed that population density, being Black, college education, vacant units, and renter occupied units were significantly associated (p < 0.05) with open-closed, and that those associations varied across Wayne County. Increases in Black population was associated with increased open-closed. Increases in vacant units, renter-occupied units, and college education were associated with decreased open-closed. These results provide input for environmental justice research to identify inequalities and discover the distribution of environmental hazards among urban neighborhoods.

Performance evaluation of external compound parabolic concentrator integrated with thermal storage tank for domestic solar refrigeration system.

The aim of this research was to develop a model for a solar refrigeration system (SRS) that utilizes an External Compound Parabolic Collector and a thermal energy storage system (TESS) for solar water heating in Chennai, India. The system parameters were optimized using TRNSYS software by varying factors such as collector area, mass flow rate of heat transfer fluid, and storage system volume and height. The resulting optimized system was found to meet 80% of hot water requirements for the application on an annual basis, with an annual collector energy efficiency of 58% and an annual TESS exergy efficiency of 64% for a discharge period of 6 h per day. In addition, the thermal performance of 3.5 kW SRS was studied by connecting it to an optimized solar water heating system (SWHS). The system was found to generate an average cooling energy of 12.26 MJ/h annually, with a coefficient of performance of 0.59. By demonstrating the ability to efficiently generate both hot water and cooling energy, the results of this study indicate the potential for utilizing a SWHS in combination with STST and SRS. The optimization of system parameters and the use of exergy analysis provide valuable insights into the thermal behavior and performance of the system, which can inform future designs and improve the overall efficiency of similar systems.

Microbiological quality of roof tank water in an urban village in southeastern China.

Urban villages are unique residential neighborhoods in urban areas in China. Roof tanks are their main form of water supply, and water quality deterioration might occur in this system because of poor hygienic conditions and maintenance. In this study, water samples were seasonally collected from an urban village to investigate the influence of roof tanks as an additional water storage device on the variation in the microbial community structure and pathogenic gene markers. Water stagnation in the roof tank induced significant decreases in chlorine (p < 0.05), residual chlorine was as low as 0.02 mg/L in spring. Propidium monoazide (PMA)-qPCR revealed a one-magnitude higher level of total viable bacterial concentration in roof tank water samples (2.14 ± 1.81 × 105 gene copies/mL) than that in input water samples (3.57 ± 2.90 × 104 gene copies/mL, p < 0.05), especially in spring and summer. In addition, pathogenic fungi, Mycobacterium spp., and Legionella spp. were frequently detected in the roof tanks. Terminal users might be exposed to higher microbial risk induced by high abundance of Legionella gene marker. Spearman's rank correlation and redundancy analysis showed that residual chlorine was the driving force that promoted bacterial colonization and shaped the microbial community. It is worth noted that the sediment in the pipe will be agitated when the water supply is restored after the water outages, which can trigger an increase in turbidity and bacterial biomass. Overall, the findings provide practical suggestions for controlling microbiological health risks in roof tanks in urban villages.