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The expanding population and rapid urbanisation, in particular in the Global South, are leading to global challenges on resource supply stress and rising waste generation. A transformation to resource-circular systems and sustainable recovery of carbon-containing and nutrient-rich waste offers a way to tackle such challenges. Eco-industrial parks have the potential to capture symbioses across individual waste producers, leading to more effective waste-recovery schemes. With whole-system design, economically attractive approaches can be achieved, reducing the nvironmental impacts while increasing the recovery of high-value resources. In this paper, an optimisation framework is developed to enable such design, allowing for wide ranging treatment options to be considered capturing both technological and fnancial detail. As well as technology selection, the framework also accounts for spatial aspects, with the design of suitable transport networks playing a key role. A range of scenarios are investigated using the network, highlighting the multi-faceted nature of the problem. The need to incorporate the impact of resource recovery at the design stage is shown to be of particular importance., Comment: 31 pages, 13 figures

Wastewater treatment plants (WWTPs) play an important role within the urban water cycle in preventing the natural water environment and human health from being negatively affected by human activities. However, wastewater treatment processes such as the discharge of effluent and indirect emissions resulting from energy or chemical production, also negatively affect the environment. Footprints have been used to track human influence on the environment through different areas of concern and have been applied in assessing the sustainability of WWTPs. A comprehensive review of footprint assessment for evaluating the wastewater treatment process in WWTPs was investigated in this article. The review showed that the carbon footprint and the water footprint were the two of the most popular footprints for evaluating the sustainability of WWTPs, and other footprint (such as nitrogen and phosphorus footprints) assessment applications were also introduced to assess the eutrophication of water bodies. To promote the application of footprint assessment on WWTP, this article regulated the study goals, frameworks, system boundary, data treatment methods, resultant interpretation process. The pros and cons of footprint assessments were discussed and investigated in detail, several suggestions were come up with for the improvement of footprint assessments. The analyzation of footprint assessments under different WWTPs revealed that wastewater treatment technologies and scales significantly impacted the footprints. Moreover, the research hotspots identified by way of a keyword network diagram showed that researchers tended to propose new indicators and models for the grey water footprint and the carbon footprint respectively, and water-carbon-energy nexus was a promising direction for future studies. Finally, two possible application scenarios, element tracing through modified footprints and management improvement through mathematical optimization, were proposed to optimize the operation strategies of WWTPs. Overall, footprint assessment research for WWTPs is still at the initial stage and needs further exploration and improvement, e.g. introducing new tools, exploring system variation under various scenarios, combining other footprints, and implementing the nexus assessment.

Tensile stress occurs in the vicinity of upper surface of the specimen in the severe plastic deformation zone, which increases the cracking and fracture tendency of the specimen and impedes the further ECAP processing. In this paper, the conventional ECAP die (Ψ = 16° and Φ = 90°) was modified to eliminate the tensile stress and enhance the compressive stress in the severe plastic deformation zone, therefore reducing the cracking and fracture tendency of the specimen. Finite element analysis demonstrated that the stress state changes from tensile to strongly compressive when using the modified die. A modified die was made and employed to extrude the commercially pure aluminum to verify its effectiveness experimentally. The billet was successfully extruded for 20 passes without obvious surface defects with the modified die, compared to 13–14 passes at most for the conventional die. Consequently, much more fine and uniform microstructure was obtained with the average grain size of 200–300 nm, while the average grain size is ∼500 nm in the case of using the conventional die.