Experimental study on CELSS-based domestic wastewater recycling for sustainable vegetable cultivation

Elevated contamination levels of domestic wastewater <b>pose challenges</b> to its treatment and reuse in Controlled Ecological Life Support System (CELSS). <b>To address this,</b> biologically treated domestic wastewater was <b>employed as a primary nutrient source</b> for leafy vegetables. <b>A comparative analysis</b> of growth parameters and nutrient assimilation was performed on two vegetables with distinct salt tolerance capacities, ice plant (<i>Mesembryanthemum crystallinum</i>) and lettuce (<i>Lactuca sativa</i>), under two cultivation systems: recycled wastewater and Hoagland solution. <b>Key findings indicated that:</b> Both had <b>comparable edible biomass</b> in recycled wastewater (ice plant: 127.28 g·plant⁻¹; lettuce yield marginally lower) vs Hoagland controls (ice plant: 124.87 g·plant⁻¹)<b>, with no significant difference</b>. Lettuce exhibited <b>enhanced root development</b> in wastewater, with <b>significantly greater underground biomass</b> (<i>p</i> < 0.05) than Hoagland-grown counterparts, <b>suggesting adaptation to saline stress</b> (wastewater EC: 6.39 mS·cm^-1<b>)</b>. Nutrient-wise, recycled wastewater had gently changed elemental ratios and pH maintained weakly acidic during cultivation. Vegetables in recycled wastewater took up more K⁺, Na⁺, and trace elements vs. Hoagland (e.g. lettuce Na content: 3.2× Hoagland controls). <b>∼13.12 m² of ice plant</b> could intake sodium from one person's daily urine under the experiment. <b>These results demonstrate</b> that recycled wastewater serves as <b>a viable primary nutrient source</b> for CELSS agriculture. Ice plant exhibited <b>higher sodium assimilation efficiency</b> and systemic adaptation to recycled wastewater, whereas lettuce developed <b>compensatory root morphological modifications</b> to mitigate high salinity.