Dans ce travail, nous avons caractérisé et évalué l’impact sur le milieu marin des rejets industriels de tannerie. Les résultats montrent que la qualité des eaux usées varie considérablement d’une étape de production à l’autre. Les opérations de prétannage (travail de rivière) sont les plus polluantes avec des teneurs en DCO qui peuvent atteindre 30 000 mg/L. L’analyse des eaux usées au niveau du bassin de collecte, où s’achemine l’ensemble des effluents de l’usine, montre une charge polluante importante et variable avec le temps. La DCO fluctue entre 700 et 3 400 mg/L et les matières en suspension entre 500 et 8 000 mg/L avec des charges polluantes moyennes de 114 et 358 kg/jour respectivement. Ces eaux sont aussi chargées en chrome avec des teneurs qui se situent entre 40 et 115 mg/L, soit une charge de 6,5 kg/jour. La teneur en sulfures varie entre 65 et 160 mg/L. En outre, l’indice de biodégradabilité (DBO5/DCO : 0.1 – 0.2) indique que ce rejet n’est pas facilement biodégradable.L’examen des teneurs en chrome chez des espèces bioindicatrices, la moule Mytilus galloprovincialis et les algues Ulva lactuca et Corallina officinalis, montre l’ampleur des apports en polluants causée par ce type de rejets au niveau de la mer. Les teneurs en chrome au niveau de ces espèces à proximité de point du déversement de ces eaux usées, sont élevées comparées à d’autres points plus éloignés.In this study, the pollution load and the impact of tannery wastewaters on the marine environment were assessed. The composition of the effluents from different fabrication steps varied considerably. Pre-tanning operations seem to be more polluting than other tanning operations, with the Chemical Oxygen Demand (COD) reaching 30 000 mg•L‑1. The analysis of the global effluent showed an important and variable pollution load versus time. The COD ranged from 700 to 3,400 mg•L‑1, and the suspended matter from 500 to 8,000 mg•L‑1 for an average pollution load of 114 and 358 kg•d‑1 respectively. Chromium concentrations ranged from 40 to 115 mg•L‑1, giving a daily load of 6.5 kg•d‑1. Sulfide concentrations varied from 65 to 160 mg•L‑1. The biodegradability index (DBO5/DCO: 0.1‑0.2) indicates that the effluent is not readily biodegradable. In order to assess the impact of the tannery wastewaters on the marine environment, the mussel Mytilus galloprovincialis and the algae Ulva lactuca and Corallina officinalis were selected as bioindicators. The results indicated high chromium contents in the species living near the point of discharge into the sea
The present work aims to isolate actinomycete bacteria with antagonistic abilities towards Botrytis cinerea, the causal agent of gray mold, from a soil sample collected from the rhizosphere of a healthy tomato grove. In vitro confrontation led to the isolation of 104 actinomycete isolates; fifteen isolates have shown the most significant mortality rate of the mycelial growth of B. cinerea (>50%). Based on the results of this screening, representative strains were selected to verify their in vivo antagonistic activity on tomato fruits; the reduction of B. cinerea has a percentage ranging from 52.38% to 96.19%. Furthermore, the actinomycete isolates were evaluated for their plant growth-promoting (PGP) properties and their ability to produce biocontrol-related extracellular enzymes viz., amylase, protease, cellulase, chitinase, esterases, and lecithinase. Indeed, Ac70 showed high β-1,3-glucanase activity and siderophore production (17U/ml and 43% respectively), and the highest chitinase activity (39μmol/ml) was observed for Ac24. These results indicated that these actinomycetes might potentially control gray mold caused by B. cinerea on tomato fruits. Investigations on enhancing the efficacy and survival of the biocontrol agent in planta and finding out the best formulation are recommended for future research.
The reuse of treated wastewater for agricultural practices is becoming increasingly important due to the growing demand for the transition to a circular economy. It has the major advantage of providing an alternative resource to the conventional water used for agricultural irrigation. The main objective of this work is to study, through tests on experimental installations, the effect of the type of irrigation water on the growth and development of lettuce. The types of irrigation water were prepared from purified wastewater, treated wastewater plus fertilizer, conventional water, and conventional water plus fertilizer. The physicochemical analyzes of wastewater from the Imzouren-Bni Bouayach WWTP resulted in different values of the parameters measured (pH, temperature, electrical conductivity, oxygen below, suspended matter, BOD5, COD, nitrate, nitrite and phosphorus) which fall within the limited range of direct discharges and comply with Moroccan standards for the quality of water intended for irrigation. The results of the characterization of the soil showed that it is a basic soil (pH= 8.5), unsalted (electrical conductivity = 2.43 ms/cm) and poor in organic and nutrient elements (Carbon 0.8%, organic matter 1.46%, nitrogen 0.06 mg/l, phosphorus 10.5 mg/l, potassium 56.4 mg/l.) The main results of the plant analysis show that the production level of this study crop irrigated with conventional water is similar to that of this study crop irrigated with treated wastewater. In other words, irrigation with treated wastewater allows lettuce to guarantee irrigated production at least at the level of conventional water. Another motivated addition of nitrogen, phosphate and potash mineral supplement in the treated wastewater improves the production potential of lettuce.
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