Sustainability has been a concern of survival for future long-term manned space missions. Therefore, the wastewater generated by the crew members, containing urine and hygiene wastewater, should be treated with appropriate biological processes to promote recycling efficiency. In this study, we developed a membrane-aerated biofilm reactor (MABR) that could achieve up to 96% total organic carbon (TOC) removal efficiency and up to 82% denitrification efficiency for an influent with 370–390 mg/L TOC and 500–600 mg/L total nitrogen (TN) without additional carbon source or sludge discharge. The nitrogen removal rate was about 100 mg N L−1 d−1. Metagenomic analysis indicated the presence of a variety of nitrifying, denitrifying, and anammox bacteria in the microbial community and existence of functional genes in nitrification, denitrification, and anammox pathways.
A novel wastewater treatment and reuse system (WTRS) combining an anaerobic membrane bioreactor (AnMBR) and an aerobic membrane bioreactor (MBR) with the design capacity of 115 L/d was developed for a terrestrial-based controlled ecological life support system (CELSS). Results clearly showed that the WTRS realized mineralization of organic compounds and reservation of nitrogenous nutrient, therefore converting the effluent into replenishment for the hydroponic system. Trace gas emission from the WTRS could meet requirements for the whole CELSS. Compared with physico-chemical processes, the specific consumables consumption of the WTRS was advantageous but its specific energy consumption is still in need of improvement. Results of microbial community analysis were consistent with the running state of the AnMBR and the MBR.
This article presents an approach for the adjustment of residual stress in silicon nitride (SiNx) films by constructing a composite multilayer structure. Curvature and Raman measurement results indicate that with the introduction of a 240-nm-thick SiO 2 sublayer, the residual stress in a 110-nm-thick SiNx film varies dramatically from high tensile stress (+358 MPa) to low compressive stress (-57 MPa). The adjustment of film stress leads to the improvement of film quality and the increase of refractive index. However, it also leads to the decreases of Young's modulus and film hardness of SiNx. Particularly, the optical band gap of SiNx remains almost unchanged during the process. This work demonstrates the practical feasibility of modifying the physical properties of SiNx with the film stress, and suggests a new physical route to stress engineering of SiNx films for microelectronic and optoelectronic applications.
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