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Solar-driven interfacial evaporation technologies for food, energy and water
Solar-driven interfacial evaporation technologies use solar energy to heat materials that drive water evaporation. These technologies are versatile and do not require electricity, which enables their potential application across the food, energy and water nexus. In this Review, we assess the potential of solar-driven interfacial evaporation technologies in food, energy and clean-water production, in wastewater treatment, and in resource recovery. Interfacial evaporation technologies can produce up to 5.3 l m–2 h−1 of drinking water using sunlight as the energy source. Systems designed for food production in coastal regions desalinate water to irrigate crops or wash contaminated soils. Technologies are being developed to simultaneously produce both clean energy and water through interfacial evaporation and have reached up to 204 W m–2 for electricity and 2.5 l m–2 h–1 for water in separate systems. Other solar evaporation approaches or combinations of approaches could potentially use the full solar spectrum to generate multiple products (such as water, food, electricity, heating or cooling, and/or fuels). In the future, solar evaporation technologies could aid in food, energy and water provision in low-resource or rural settings that lack reliable access to these essentials, but the systems must first undergo rigorous, scaled-up field testing to understand their performance, stability and competitiveness.
Impact of transboundary water flows on quality-induced water pressure in China
Quality-induced water pressure (P) is gaining increased attention. With the flows of transboundary water, P can be transferred among upstream and downstream regions. Here, we quantified the magnitude of pollutant transmission, and assessed its impact on individual provinces in China. On the annual basis, P was mitigated in 61% of provinces for Chemical Oxygen Demand, 87% for Ammonia Nitrogen, and 84% for Total Phosphorus, while it was intensified for 77% for Total Nitrogen in 2021. The aggregated P were mitigated in 68% of provinces, while intensified in 32% provinces. Furthermore, the monthly assessment has found that the impact of transboundary water on P varies seasonally, generally alleviating in winter and exacerbating in summer. This fluctuation was attributed to the comparatively higher quality of transboundary inflows during winter relative to local water quality. This study provides a scientific foundation for effective water management and quality control.
Water industry strategies to manufacture doubt and deflect blame for sewage pollution in England
The water and sewerage companies (WaSCs) in England are majority-owned by a range of global investors. The industry is under intense scrutiny for widespread failure in its environmental performance, discharging 12.7 million monitored hours of untreated wastewater and sewage into English waterways between 2019 and the end of 2023. At the time of writing, multiple investigations by environmental and financial regulators are in progress, and regulatory oversight is under review by the recently formed Office for Environmental Protection. While limited monitoring hid the full extent of underperformance, we argue that the WaSCs have prolonged this environmental disaster through strategies that mirror those of other large polluting industries in the past. We test this hypothesis for the nine major WaSCs in England against a published framework of 28 ‘greenwashing/deception’ tactics of large industries. We identified 22 of these tactics that could be seen as disinformation, greenwashing and manufacturing doubt. The financial exploitation of water resources in England, alongside long-term degradation of infrastructure and ineffective regulation, raises globally important issues around water security, ethics and environmental stewardship. Much greater scrutiny of both industry performance and industry communication is required.
Brine management with zero and minimal liquid discharge
Zero liquid discharge (ZLD) and minimal liquid discharge (MLD) are brine management approaches that aim to reduce the environmental impacts of brine discharge and recover water for reuse. ZLD maximizes water recovery and avoids the needs for brine disposal, but is expensive and energy-intensive. MLD (which reduces the brine volume and recovers some water) has been proposed as a practical and cost-effective alternative to ZLD, but brine disposal is needed. In this Review, we examine the concepts, technologies and industrial applications of ZLD and MLD. These brine management strategies have current and potential applications in the desalination, energy, mining and semiconductor industries, all of which produce large volumes of brine. Brine concentration and crystallization in ZLD and MLD often rely on mechanical vapour compression and thermal crystallizers, which are effective but energy-intensive. Novel engineered systems for brine volume reduction and crystallization are under active development to achieve MLD and/or ZLD. These emerging systems, such as membrane distillation, electrodialytic crystallization and solvent extraction desalination, still face challenges to outcompete mechanical vapour compression and thermal crystallizers, underscoring the critical need to maximize the full potential of reverse osmosis to attain ultrahigh water recovery. Brine valorization has potential to partially offset the cost of ZLD and MLD, provided that resource recovery can be integrated into treatment trains economically and in accordance with regulations.
Advancing robust all-weather desalination: a critical review of emerging photothermal evaporators and hybrid systems
All-weather solar-driven desalination systems, integrating photothermal evaporators with hybrid technologies, present a sustainable, cost-effective, and high-efficiency strategy for freshwater production. Despite significant advancements, previous reviews have predominantly focused on daytime evaporation, neglecting the broader scope of all-weather seawater evaporation. This review provides a comprehensive examination of the current status of all-weather seawater evaporators and their hybrid systems. Initially, the review details the system’s composition and operating principles, as well as the design criteria for high-performance evaporators. It then goes over various common photothermal conversion materials for seawater desalination, with a particular emphasis on those materials tailored for all-weather applications. It also offers an in-depth overview to the developed photothermal hybrid systems for all-weather seawater evaporation, including their working principles, the efficiency of evaporation across the day-night cycle, and their practical applications. Lastly, the existing challenges and potential research opportunities are thoroughly discussed.
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