Characterization of Two Olive Mill Wastewater and Its Effect on Fenugreek (<i>Trigonella foenum-graecum</i>) Germination and Seedling Growth

Abstract

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 (BOD 5 ) 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 concen - tration 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%.