Water quality assessment of highly polluted rivers in a semi-arid Mediterranean zone Oued Fez and Sebou River (Morocco)

Oued Fez (one of the Sebou River tributaries - Morocco) allowed us to study and quantify the effect of the lack of wastewater treatment on surface water quality in semi-arid hydrological context. The analysis is based on field data collected from June 2009 to December 2011. Concentration and load patterns of nitrogen, phosphorus and chromium (used in the processing of leather) are compared in stable hydrological conditions during low flow and high flow periods in an eight-location sampling network. The Oued Fez and the Sebou River are characterised by severe pollution downstream from the city of Fez, particularly TN (mainly NH4 and N-org), TP (mainly P-part) and TCr. The most polluted sites are those directly under the influence of domestic and industrial waste water inputs, particularly tannery effluents. Obviously, the concentrations measured at these locations are above all environmental quality standards. Pollutant loads are very heavy in the Sebou River and can contaminate the river course for kilometres. Moreover, as the water of the Sebou River is used for the irrigation of vegetables, serious problems of public health could arise. A better understanding of contaminant dynamics and self-purifying processes in these rivers will help implement actions and steps aimed at improving water quality in the Sebou River, which is the primary water supply source in Morocco and is used for agricultural and industrials purposes as well as for drinking water

Occurrence and removal of butyltin compounds in a waste stabilisation pond of a domestic waste water treatment plant of a rural French town

International audienc

Occurrence and removal of butyltin compounds in a waste stabilisation pond of a domestic waste water treatment plant of a rural French town

The aim of this study was to investigate the fate and behaviour of butyltin pollutants, including monobutyltin (MBT), dibutylin (DBT), and tributyltin (TBT), in waste stabilisation ponds (WSP). The study was conducted as part of a baseline survey and included five sampling campaigns comprising bottom sludge and the water column from each pond from a typical WSP in France. Butyltins were detected in all raw wastewater and effluents, reflecting their widespread use. Our results revealed high affinity between butyltins and particulate matter and high accumulation of butyltins in the sludge taken from anaerobic ponds. The dissolved butyltins in the influent ranged from 21.5 to 28.1 ng(Sn).L-1 and in the effluent, from 8.8 to 29.3 ng(Sn).L-1. The butyltin concentrations in the sludge ranged from 45.1 to 164 and 3.6-8.1 ng(Sn).g(-1) respectively in the first and last ponds. Our results showed an average treatment efficiency of 71% for MBT, 47% for DBT, 55% for TBT. Laboratory sorption experiments enabled the calculation of a distribution coefficient (Kd = 75,000 L.kg-1) between TBT and particulate matter from the WSPs. The Kd explained the accumulation and persistence of the TBT in the sludge after settling of particulate matter. The continuous supply of contaminated raw wastewater and the sorption-desorption processes in the ponds led to incomplete bio- and photolytic degradation and to the persistence of butyltins in dissolved and particulate matrices throughout the survey period. It is thus recommended to use shallow ponds and to pay particular attention when sludge is used for soil amendment

Effect of controlled crystallization on polaronic transport in phosphate‐based glass‐ceramics

The effect of induced crystallization on changes in electrical transport of two types of glass‐ceramics, pure polaron conductive 40Fe2O3‐60P2O5 (F40) (mol%) and predominantly polaronic 5Li2O‐5ZnO‐40P2O5‐50WO3 (Li‐50W) (mol%) was investigated. F40 glass‐ceramics produced at low heat‐treatment temperatures contain single‐phase Fe3(P2O7)2 whereas at higher temperatures two more phases Fe4(P2O7)3 and Fe(PO3)3 are formed. Structural modifications strongly depend on the crystallization temperature and time. The appearance of crystalline phases studied by Mössbauer spectroscopy exhibits changes in Fe2+/Fetot ratio in crystalline/glassy phases. The detailed analysis of different iron sites allows their correlation with changes in electrical conductivity as crystallization progresses. Depending on the course of crystallization, the contribution of each phase to the overall conductivity is determined by the frequency dependence of Zʺ(ω) and Mʺ(ω). DC conductivity shows a sharp decrease as Fe3(P2O7)2 phase appears and consequently glass matrix remains impoverished in Fe2+‐Fe3+ pairs. In the multiphase systems prepared at higher crystallization temperatures, the overall electrical conductivity increases although the continuous grain boundaries along different crystalline grains play a limiting factor. In contrast, the slight conductivity change in Li‐ 50W glass‐ceramics upon crystallization is a result of remaining W5+‐W6+ pairs in the residual glassy phase. Independence of electrical transport on Li+ ions confirms predominantly polaronic transport in Li‐50W glass‐ceramics