Magnetic microspheres including Fe₃O₄, MnFe₂O₄, ZnFe₂O₄, and CoFe₂O₄ have been synthesized via a simple solvothermal method followed by surface hydrophobization with 1H,1H,2H,2H-perfluorooctyltrichlorosilane. The hydrophobic magnetic microspheres can self-assemble into a thin film under simulated solar light irradiation and float on the surface of water. The formed film was used as photothermal material for water evaporation based on a new concept of interfacial solar heating. The water evaporation efficiency was significantly enhanced by the Fe₃O₄ thin film, and is about 1.4, 1.7 and 2.2 times higher than that without the formation of a Fe₃O₄ thin film, Fe₃O₄ uniformly dispersed in water, and water evaporation itself, respectively. The temperature gradient distributions from the surface to the bottom of the water directly demonstrated the advantage of interfacial solar heating for water evaporation. We believe that the water evaporation efficiency with the magnetic thin film is mainly due to the high light absorption, rapid heat transfer and good solid–liquid adhesion performance. In addition, the hydrophobic magnetic microspheres also have advantages over other reported photothermal materials due to their easy recycling, non-toxicity, low dose, and low cost.

Pipe breaks have significant impacts on the hydraulic and water quality performance of water distribution systems (WDSs). Therefore, it is important to evaluate these impacts for developing effective strategies to ultimately minimize the consequences of these events. However, there has been surprisingly limited research focusing on impact evaluation for pipe breaks so far. To address this gap, this paper proposes a framework to comprehensively evaluate hydraulic and water quality impacts of pipe breaks on a WDS using six quantitative metrics. These metrics primarily focus on identifying (i) break outflow volume, (ii) water shortage, (iii) nodes with reduced service quality, (iv) pipes with affected pressures, (v) pipes with reversed flow directions, and (vi) pipes with significantly increased velocities, for each breaking event within a WDS. Statistical behaviors, spatial properties, and pipe rankings of metric results are analyzed to reveal the underlying characteristics of impacts induced by pipe breaks. We illustrate the proposed framework using three WDSs with different properties. Results show that impacts of pipe breaks not only vary with pipe diameters but are also significantly influenced by pipe locations, when the break occurs, and the specific metric considered. The proposed framework greatly enhances the fundamental understanding of the underlying properties of breaking impacts on the hydraulic and water quality of WDSs, as well as the ranking of pipes based on the consequences of breaks. Such understanding offers important guidance to develop effective pipe management, resource planning, and break restoration strategies to minimize the impacts of breaking events on WDSs.

Leakage or pipe burst detection, often carried out by using the pressure sensor systems (PSSs) within a water distribution network (WDN), is critical to enable such networks to operate in a safe manner. The majority of previous studies have focused on either the advancement of detection equipment or the development of detection algorithms (leakage localization or sensor deployment). In contrast, this paper proposes a methodology to investigate the underlying capacity of existing PSSs for pipe burst detection using a set of quantitative metrics. These metrics focus on the identification of (1) nodes where bursts cannot be detected by the PSS (undetectable nodes); (2) undetectable demands, derived from the demands of undetectable nodes; (3) detection dimension, representing the number of sensors that can simultaneously detect a burst at a node; (4) the spatial region where bursts within each subregion can be detected by a particular sensor with a minimum outflow; and (5) the detectable threshold, which indicates the minimum burst outflow of each node triggering its associated pressure sensor. The proposed methodology has been applied to two real-world WDNs with varying sizes and configurations. Results show that the former two metrics can indicate the spatial distribution of the nodes at which bursts can be detected, and the latter three metrics can successfully reveal the PSS’s detection dimension and spatial regions, as well as the detectable threshold of each node. Such improved understanding offers guidance to develop effective burst-management strategies and to facilitate decision-making processes regarding sensor placement and burst localization.

Apart from water quality, leakage control and energy consumption management are the most concerning challenges for water treatment plants (WTPs). The joint scheduling of pumps and pressure reducing valves (PRVs) in the water distribution network can reduce excessive pressure and distribute pressure more evenly, which achieves comprehensive reduction of leakages and energy consumption. Taking into account the main shortcomings of the commonly used methods, such as scheduling pumps or PRVs separately, or optimizing PRV settings when their position is given, etc., this paper has taken the PRV (position and setting) and the working status of variable speed pumps (VSPs) as decision variables and the cost savings contributed by leakage reduction and energy consumption savings as the objective function, which maximized the economic benefits brought by PRV and/or VSP scheduling. A genetic algorithm (GA) was used to optimize the solution under multiple working conditions. The performance of three control strategies (PRV-only scheduling, VSP-only scheduling, and joint scheduling of PRVs and VSPs) are compared to each other based on a small network. Joint scheduling has achieved the best economic benefits in reducing the gross cost (contributed by leakage and energy consumption) of the three control strategies, which results in a leakage reduction of 33.4%, an energy consumption reduction of 25.4%, and a total cost reduction of 33.1%, when compared to the original network, and saving about 1148 ${\mathrm{m}}^3$ water (7% of the original consumption) and 722 $\mathrm{kWh}$ electric energy (25.4% of the original consumption) per day.

Erosion of a saturated sand bed by a vertically upward water jet was studied experimentally. Direct observations on the behavior of sand-bed erosion were obtained by increasing the flow rate at a small increment until fluidization developed to the surface of the sand layer. With the increase in flow rate, the sand bed underwent different stages: no cavity, a stable cavity above the jet, an unstable cavity propagating upward, and full fluidization. The mechanism for the cavity evolution was investigated, and an analytical model was developed to predict the critical flow rate for full fluidization. The model predictions compared well with the measurements in the experiments with different sand-layer thicknesses.