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- Wastewater as a nutrient source for hydroponic production of lettuce: Summer and winter growthPublication . Santos, Ounísia; Vaz, Daniela; Sebastião, Fernando; Sousa, Helena; Vieira, JuditeSolutions combining soilless cropping systems with wastewater reuse can offer benefits in the agriculture sector, reducing pressure on water resources, promoting sustainable production, and reclaiming wastewater. However, assessing the sanitary risks associated with wastewater reuse is of utmost importance. This study aimed to investigate the hydroponic growth of lettuce (Lactuca sativa var. crispa L.) in wastewater from an urban treatment plant with different levels of treatment and evaluate potential sanitary risks. Crop growth took place in a greenhouse, during summer and winter periods, using wastewater after primary (PTW) or secondary (STW) treatment, and a nutrient solution (NS), as control. Physical and chemical water quality parameters, morphological crop growth parameters, and environmental conditions inside the greenhouse were monitored. Toxicity analyses were carried out through cell viability assays with the Caco-2 cell line and total coliforms and Escherichia coli (E. coli) were determined. Wastewater-grown plants achieved acceptable growth, even though presenting lower fresh weight than NS-plants. STW-plants’ growth was limited essentially by nutrient deficiency, and PTW-plants were affected by nutrient deficiency, pH values, solid load, and N-NO2 concentration. Higher temperatures in summer led to faster crop growth, and lower temperatures in winter allowed better nutrient uptake by the crop. Wastewater-grown plants did not evidence toxicity in leaf extracts up to 1 % w/v. Coliform enumeration data indicated an accumulation in plant roots, with high removal from the wastewater. E. coli was not detected on plants’ leaves and total coliforms were within acceptable limits. Furthermore, the results point to an improvement in the wastewater quality, with minimum removal values of 75.2 % BOD5, 83.1 % COD, 43.4 % P, 44.9 % N, and 90.4 % K. The results demonstrated the viability of wastewater reuse for hydroponic production allowing a better understanding of its processes and contributing to mitigating water scarcity for food production, and the impacts of treated wastewater discharge in freshwater courses, particularly those associated with nutrient delivery to aquatic systems.
- Production of parsley and pennyroyal with an African catfish-based aquaponics partially fed with yellow mealworms - Tenebrio molitorPublication . Bernardino, Raul; Vieira, Judite; Vaz, Daniela C.; Santos, Ounísia D.; Ribeiro, Vânia S.; Pires, Cristiana L.; Cotrim, Luís; Bernardino, SusanaInsects can be used as alternative protein/food sources. Here, a novel aquaponic system based on the African catfish (Clarias gariepinus) fed with 30% of yellow mealworms (YM) (Tenebrio molitor) as substitute feed to 100% of fish meal (FM) was employed to produce parsley (Petroselinum crispum) and pennyroyal (Mentha pulegium). The two systems implemented (30YW/70FM and 100FM - control) showed identical water quality parameters. The 30YW/70FM operation led to a reduction by 27% of the carbon footprint, relatively to the 100FM system. Plants cultivated in the 30YW/70FM aquaponic system led to lower plant biomass (↓∼75%), as stated by the statistically significant (p < 0.05) lower values of “plant height”, “foliage diameter”, “leaf number”, “biggest leaf length” and “root length”. Moreover, 100FM parsley showed higher levels of greenness (100%) and health status (97%) than the 30YW/70FM plants (↓50% greenness; ↓20% health status). Likewise, 100FM pennyroyal also showed higher levels of greenness (100%) and health status (100%) than 30YW/70FM pennyroyal (↓56 % greenness; ↓59% health status). Also, even if all plants presented equivalent levels of P, K, Ca and Fe, the plants grown in the 30YW/70FM system showed some Cl-accumulation (>7.0 g Cl.kg−1 for parsley and > 4.0 g Cl.kg−1 for pennyroyal, in dry weight) in the leaves and Cu and Mn accumulation in the roots (> 0.4 g.kg−1 in dry weight). The presence of high concentrations of Cl in T. molitor, and consequently in the water and fish faeces, might have caused some abiotic stress and toxicity to plant tissues, reducing plant growth.