Recently, the Moon has once again become the focus of the aerospace field. The lunar base is likely to be the next long-term extraterrestrial base for humans after the near-Earth orbit space station. However, the cost of lunar replenishment will substantially increase, and the time required for replenishment will become longer. It is necessary to establish a living system with higher degree of material closure and stronger self-sustainability to provide life support service for residents. The controlled ecological life support system (CELSS) is a feasible way to achieve the circular supply of oxygen, water, and food through biological regeneration. However, there is a practical issue of how to gradually establish a CELSS on the Moon and how to match the bio-regenerative system with the physicochemical system established in the early stage, to reduce the cost of the construction of the lunar life support system. In this paper, based on fully inheriting the physicochemical regeneration technologies of the present near-Earth orbit space station, biological components such as plants, microalgae, and microorganisms were gradually introduced in 4 stages to establish an upgraded CELSS with a total material closure degree of 98%. In addition, the material flux models of C, H, and O elements at different stages of the lunar base were designed and calculated. The results of this paper provide a reference for the construction of future lunar base life support systems in terms of improving the engineering feasibility of CELSS.

The reuse of wastewater is a key problem in controlled ecological life support system (CELSS). In this study, the feasibility to reuse the treated wastewater (including sanitary wastewater and urine wastewater) as a plant hydroponic medium was verified. Two salt-tolerant plants, apium graveolens Linn (celery) and mesembryanthemum cordifolium L.F. (cordifolium), were cultivated with the reused medium or Hoagland nutrient solution, and the characteristics of crop growth, hydroponic medium composition, and elements absorption by plants were investigated. The results showed that the reused medium replenished with micronutrient elements could maintain the normal growth of cordifolium and celery crops. The biomass productivity of cordifolium cultivated by the recycled medium (121.53 g FW/strain) was higher than that cultivated by Hoagland nutrient solution (98.33 g FW/strain). The nutrient elements accumulation in plant dry mass indicated that plants could effectively utilize the recycled mineral elements in wastewater, and cordifolium exhibited better stability and adaptability to salt-induced environment. The absorption capacity of Na and Cl elements in cordifolium cultivated within the reused medium was the highest, which was 4.54% DW and 2.63% DW, respectively. This study demonstrated the feasibility to directly reuse domestic wastewater as the main ingredient for plant hydroponics, which could provide insights into design and operation of plant hydroponics system and water circulation system in CELSS.