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This study detailed the effect of simultaneous multiple intrinsic and extrinsic factors on the characteristics of Sfax activated sludge wastewater treatment plant (WWTP), located in Southern East Tunisia. The plant performance was evaluated through descriptive and statistical analysis of quantity and quality data of both raw wastewaters and treated effluent over a period of three years (2008-2010). Despite the rehabilitation, poor performance was shown to be attributed to raw wastewaters quality, civilization populations, bad functioning of the aerators and the industrial fallouts and deposits. Therefore, the downstream values of BOD 5 , COD, SS, FC, FS, TKN and TP are enough to achieve a final effluent that would meet the Tunisian standards limit. Multiple regression analysis showed that removal efficiencies of BOD 5 , COD and SS can be predicted to reasonable accuracy (R 2 = 0.973, 0.946 and 0.925, respectively). Goodness of the model fit to the data was also evaluated through the relationship between the residuals and the model predicted values of BOD 5 r, CODr and SSr. The advantage of this model is that it would allow a better process control.

Olive oil is the most important commodities produced in the Mediterranean region. Due to its significant economical importance, the usage of pesticides in its production is systematic, by using a wide range of plant protection products with a variety of modes of action. As a consequence, monitoring of their residue levels in these products is a necessity. In the present study a reversed-phase high performance liquid chromatography method, with a short sample preparation step, based on acetonitrile extraction is developed and validated in olive oil, with a large scope that includes Deltamethrin as pesticide. Good sensitivity and selectivity of the method were obtained with limits of quantification at 0.2 mg kg-1. Deltamethrin has recovery rate which is of about 80℅. We confirm also the efficiency of alumina, used as adsorbent in the clean up step, to remove triglycerides and to get a pure extract. The agronomic implementation of this protocol allows us to determine the influence of some parameters on the dose and the period of treatment affecting the detected quantities of Deltamethrin residues in the produced olive oil. Indeed, we prove that the treatment dose should be specific for each case considering the olive variety, the geography of the orchard, and the predicted harvest time to determine the convenient dose of treatment. In addition, the results show that the preventive treatment at the blooming phase, does not lead to the concentration of Deltamethrin residues in the oil as it happens at the lipogenesis phase.

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The occurrence and the removal efficiency of natural estrogens, estrone (E1), 17β-estradiol (E2) and estriol (E3), as well as a synthetic estrogen, 17α-ethinylestradiol (EE2), were investigated in two sewage treatment plants (STPs) employing different activated sludge processes in Tunisia, by monitoring their concentrations in dissolved wastewater. The analytes were extracted by solid-phase extraction and then analyzed by gas chromatography coupled with mass spectrometry (GC-MS). Results indicate that natural and synthetic estrogens were detected in the STP influent samples. The concentrations of natural and synthetic estrogens (except E1) detected in the effluents of alternating activated sludge process were generally lower than the limit of detection. On the other hand, all estrogens were not totally removed through the simple activated sludge process; as a result, they were detected in effluent samples. E3 showed the highest concentration in the influent samples at 98 ng L-1 in the alternating anoxic/aerobic activated sludge process, and at 102 ng L-1 in the simple activated sludge. Two different types of diurnal variation of estrogens discharge were identified. The two STPs had approximately similar daily loads of estrogens in influents at 112.7 µg d-1 and 109.58 µg d-1 , respectively. The distribution of estrogens in the STPs is affected by their metabolisms in human body and their transition through biological treatment processes. Removal efficiency varied among STPs; high removal of estrogens (84-97%) with the exception of E1 (80%), were generally achieved in alternating anoxic/aerobic activated sludge process with a high hydraulic retention time (40 h) and treatment stages for removal of nitrogen. E1 showed the lowest removal of all estrogens in the two STPs. This could be caused by conversion of E2 to E1 in the treatment process, or by cleavage of estrogen conjugates. On the other hand, E3 showed the highest removal of all estrogens both in alternating anoxic/aerobic and simple activated sludge processes at 97.5% and 85.5%, respectively). EE2, which is particularly sensitive to human consumption as the oral contraceptive, were removed by approximately 77.5%) in the simple activated sludge process. Filamentous bacteria were less effective in removal estrogens than protozoa.