The Feasibility Research on Reusing High Salinity Wastewater as a Plant Nutrient Medium for Plant Hydroponics in 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.