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Energy consumption from municipal wastewater treatment plants (WWTPs) has brought escalating dual pressure of high expenditure and greenhouse gas emissions to environmental engineers and policy makers. In order to identify the underlying factors affecting energy usage, a comprehensive nationwide investigation program was done to analyze 1184 urban WWTPs in China over a period of 30 years (1984–2013). This investigation included a consolidated evaluation of key design parameters (scale, treatment process and effluent standard), different treatment units and geographical distribution of WWTPs in terms of energy consumption. Comparisons were also made between the statistical- and the baseline-value of unit energy consumption. These findings demonstrated the importance of the integrated effects of key design parameters on WWTPs energy consumption, and specific reference benchmark, recommendations, strategies and future development were provided accordingly. The present work can hopefully assist in understanding of how and to what extent key factors are incorporated into design guidelines, and also help decisions makers and engineers construct and upgrade WWTPs in the best energy saving way. Image 1 • A nationwide study was done to analyze 1184 wastewater treatment plants in China. • Comparisons were made between the statistical and baseline value of unit energy consumption. • Specific energy benchmark was provided for reference to achieve energy saving. • Key design parameters were integrated to formulate strategies for best energy saving. [ABSTRACT FROM AUTHOR]

Self-cleaning mechanisms of photovoltaic panels is a research hotspot in recent years, but the preparation of superhydrophobic coatings with excellent anti-reflection effect and durability for photovoltaic panels is still a problem to be solved. Inspired by the human scalp structure, we propose an interconnected three layer coatings (ITSC), which can produce self-cleaning effect on photovoltaic panels. Specifically, the prepared ITSC, owning porous three-dimensional network structure, consists of three layers with similar and cross-linked materials to ensure continuity and good adhesion among layers. Based on the experimental results, it can be concluded that the coating has an average transmittance that is 6.44% higher compared with bare glass. The bandwidth of high light transmittance (>91%) is almost 4 times that of bare glass. The pencil hardness test grade of the coating is 5 H, and the tape adhesion test grade is 5 B. In three simulated severe environmental stability tests (acid rain, high temperature and low temperature), the proposed coating can still maintain long term superhydrophobicity. Compared with uncoated photovoltaic panels, the maximum output power of coated one is 2.61 times that of the blank panel after the deposition of saline laterite under simulated drizzle conditions. The proposed coatings provide a promising solution for improving the performance of photovoltaic panels, reducing the negative impact of dust deposition, and improving the power output efficiency of photovoltaic power plants. [ABSTRACT FROM AUTHOR]