Advanced electrochemical oxidation process for wastewater purification in life support system

Long-duration spacecraft flying and space station requires autonomous self-sufficient life support systems (LSS), which refer to the greatest practical level of mass, recycle and safety for humans. It implies that human wastes (e.g. urine) are responsible to be mineralized with closed cycling of water, gas to fully meet human requirements. Therefore exploring novel high-efficiency wastewater mineralization process is urgently needed. The paper focused on the urine treatment by advanced electrochemical oxidation process to explore new technology for wastewater purification in the controlled ecological life support system (CELSS) in the spacecraft and space station. The effects of current, pH and the initial concentration of the urine were investigated in a novel electrochemical system with perfect electrode life. Elevated the current will lead to faster chemical oxygen demand (COD) removal rate, and the instantaneous current efficiency (ICE) keeps relatively high. The wastewater without pH adjustment showed good performance on COD removal comparing with that of the pH = 3, indicating that this technology is very suitable for LSS. The COD removal was 3.6 times larger than that of diluted 10-folds though the removal rate was decreased. The results of HPLC analysis indicated that some degradation intermediates formed during degradation and they were gradually disappeared after treated 60 min. The total The total organic carbon (TOC) of the urine that diluted 10-times could reach below 10 mg L-1, indicating the feasibility of the wastewater purification. Based on these results, a closed LSS based on the integration of the hard-core of the AEOPs and biological unit, which includes many separation and purification processes, was proposed. The apparatus was very simple, the reaction conditions were not rigor and the energy consumption was acceptable, showing promising applicability in spacecraft or space station.