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- A comprehensive ecotoxicological evaluation of a treated olive mill wastewater and obtained sludgePublication . Pinto, José N.; Pereira, Andreia; Silva, Ana Rita. R.; Cardoso, Diogo N.; Mostafaie, Amid; Campos, Fábio; Rehan, Iryna; Moreira, Olga; Lopes, Ivã Guidini; Murta, Daniel; Afonso, Alexandra; Oliveira, Margarida; Silvério, Karina S.; Santos, Maria Teresa; Carvalho, Fátima; Almeida, Adelaide; Loureiro, SusanaOlive mill wastewaters (OMWWs) are an environmental problem in the Mediterranean region, and it is crucial to explore strategies for their treatment and repurposing. The chemical precipitation technique (CPT) has been presented as a cost-effective wastewater treatment solution that might be applied to OMWW. The CPT-resulting precipitant subproducts (sludge) may be reprocessed (e.g., agricultural fertilizer and/or soil amendment), while the treated wastewater may be repurposed or reused (e.g., irrigation, aquaponic, or industrial processes). This study aimed to evaluate the efficacy of CPT in treating wastewater from the olive oil industry from an ecotoxicological perspective. Additionally, to assess the safe use of the obtained sludge in CPT treatment, its effects on soil biota were assessed. For this, a set of ecotoxicological assays using freshwater (Raphidocelis subcapitata, Daphnia magna and Danio rerio), terrestrial invertebrates (Folsomia candida and Enchytraeus crypticus), and plants (Brassica oleracea and Lolium perenne) were used as model organisms. Results demonstrated that CPT reduced OMWW toxicity to freshwater organisms, offering a favorable outlook on CPT’s potential as a wastewater treatment method. Increasing application rates of sludge in soil reduced the shoot biomass and the hydric content of both plants compared to the control. Survival of F. candida and E. crypticus was not affected by sludge in soil at any tested application rate, yet sludge application negatively affected the reproduction of both species, even at relevant sludge application rates (2%) of sludge in soils. Overall, the applicability of this sludge obtained by the CPT treatment in soils should be carefully evaluated due to the observed adverse effects on soil biota. Although the results of CPT were promising in reducing the toxicity of OMWW for these aquatic species, some adjustments/improvements should be performed to improve this technique and use all the obtained resources (treated water and sludge) in a fully circular perspective.
- Hermetia illucens L. frass in promoting soil fertility in farming systemsPublication . Menino, Regina; Esteves, Catarina; Fareleira, Paula; Mano, Raquel; Antunes, Joana; Rehan, Iryna; Murta, Daniel; Moreira, OlgaFollowing a pot trial with annual ryegrass (Lollium multiflorum Lam. (Pooideae: Poaceae)), where the effect of chemical fertilization was compared with organic fertilization with Black Soldier Fly larvae frass (BSFF), obtained by bio-digestion of cattle production effluents, and with mixed fertilization in proportions of 25%, 50%, and 75% of BSFF, the effect on crop production and soil fertility was tested in three soils of different textures, namely, sandy soil (Gleyic podzol), calcareous soil (Haplic calcisol), and clay soil (Haplic fluvisol). On top of the previous experimental device, a second year of testing was carried out with sowing of the same crop, but without any fertilizer input in all the residual soils for the different further modalities. With regard to the second sowing cycle production, the results are supportive of the expectation that fertilization with BSFF has a superior capacity for soil fertility resilience (assessed in terms of the ability to maintain or even increase soil production in the following year, in the absence of any fertilizer application) in all the soils tested in this experiment, with a significantly greater difference in the treatment corresponding to fertilization with only BSFF compared to the exclusively chemical treatment, in all the soils tested. Furthermore, BSFF, preferably as a mixed fertilizer (in a proportion until 75%), is shown to be a promising alternative for Gleyic podzol in the production of ryegrass as in the resilience and promotion of soil productivity. As far as more fertile soils are concerned (as in the case of Haplic calcisol and Haplic fluvisol), BSFF has not proved promising in terms of immediate crop production.
- Olive pomace inclusion alters the microbial community of Black Soldier Fly larvae frass while maintaining fertilizer qualityPublication . Lopes, Ivã Guidini; Lima, Nathali Machado de; Ribeiro, Teresa; Murta, Daniel; Yong, Jean Wan Hong; Lalander, CeciliaOlive pomace (OP) is a sludge arising from the production of olive oil, generated in increasing amounts in Portugal. The management of this toxic waste stream is complex and the number of processing plants is limited. In this study, OP was incorporated as a feed component for rearing black soldier fly larvae (BSFL) under industrial conditions. Larvae were reared inside a climate-controlled room with regulated temperature and humidity. The rearing cycle lasted 13 days, after which larvae were harvested. In addition to assessing bioconversion efficiency and larval proximate composition, the resulting frass was examined for its fertilizer potential. Frass was analyzed for plant nutrient content and microbial profile in three forms: fresh, heat-treated (70°C for 1 h), and pelletized. The inclusion of OP in the diets reduced waste-to-biomass conversion efficiency (21.5%DM to approximately 13.3%DM) but did not affect the proximate composition of the larval biomass, which consistently contained around 43%DM crude protein and 20%DM crude fat. Neither the presence of OP nor the applied post-treatments altered the nutrient composition of frass, which contained on average 3.5% total N, 2.6% P2O5, and 5.9% K2O. However, at the highest inclusion level (84%), the abundance of bacterial and fungal groups was significantly reduced. The predominant phyla in the frass were Actinobacteria, Bacteroidota, Firmicutes, Proteobacteria, Ascomycota and Basidiomycota, and the dynamics of microbial communities were influenced by specific micronutrients. The presence of OP led to a significant reduction of potentially pathogenic bacteria and fungi in the frass, indicating a sanitizing effect attributable to this material.