In Morocco, the olive industry produces a large quantity of olive mill wastewater (OMW) every year for a short period (November to February). The physicochemical properties and quantities of these effluents depend largely on the extraction system used. The aim of this study is to characterize these effluents for the purpose of evaluating their impact on Fenugreek (Trigonella foenum-graecum) germination and seedling growth. For this purpose, a germination experiment was conducted, wherein 25 Fenugreek seeds were positioned on filter paper within Petri dishes. Subsequently, these seeds were subjected to varying concentrations of water sourced from two olive crushing processes: the Continuous System (OMW-CS) and the Semi-Modern System (OMW-SM) (0%, 1%, 2%, 5%, 7%, 10%, 25%, 50%, 75%, and 100%). The Petri dishes were then placed in an incubator set at 25 °C for a duration of 8 days. The results of the physicochemical analysis showed that both types of water had an acid pH and were rich in organic matter. The 5-day biological oxygen demand (BOD5) values were similar, while the chemical oxygen demand (COD) values were quite different. Microbiological analysis revealed that yeasts and fungi were the main constituents of the flora of these wastewaters, with no significant difference between the two types of OMW. However, the total number of aerobic mesophilic flora was higher for OMW-CS than for OMW-SM. Analysis of variance revealed a highly significant difference between OMW-CS concentrations (F = 2998.667; p <0.000) and OMW-SM (F = 2839.778; p <0.000). A minimal germination rate (30%) was recorded for OMW-CS at a concentration of 10%. For OMW-CS, total inhibition of germination was observed at concentrations of 25%, 50%, 75%, and 100%, while for OMW-SM, this inhibition was recorded above a concentration of 2%.
Olive mill wastewater (effluents from olive oil extraction during harvest) is a source of environmental pollution due to its high acidity and heavy loads of polyphenols and organics. Our aim is to study the phytotoxicity of olive mill wastewater (OMW) at different concentrations on the germination and growth of tomatoes (Solanum lycopersicum L.). To assess this, we measured the percentage of germination (GP), the germination inhibition rate (GIR), the length of the main stem, the number of leaves, and the biomass of the stem, leaves, and roots. The germination test was carried out by placing 25 tomato seeds on filter paper in Petri dishes and then irrigating with different concentrations of OMW (0%, 1%, 2%, 5%, 7%, 10%). The boxes were placed in an incubator at a temperature of 25 °C for 10 days. The results obtained show that, after 10 days of germination, the GP is maximal (more than 98%) at concentrations of less than 7% (r = -0.98; p<0.000) and with an “inhibitory” effect at more than 7% (r = +0.98; p<0.000). However, the growth in length (8.514±2.612 cm) and the number of leaves (4.667±0.866 leaves) were maximum, respectively, at 2% and 1%, after a period of 30 days. However, the dry weight is maximum (0.235±0.049 g) at 5% OMW, however, there is no significant difference in the fresh and dry weights of the stems and leaves for different concentrations. In light of these results, the OMW of crushing units using the continuous three-phase process could be used as an irrigation source at concentrations below 7%, for better tomato yield.
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