Descriptive and multivariate analyses of four Tunisian wastewater treatment plants: A comparison between different treatment processes and their efficiency improvement.

This study was undertaken to evaluate the performance of four wastewater treatment plants/processes over a 4 year period. The wastewater flow evolution, energy consumption, and quality indicator parameters (BOD5, COD and TSS) at the inlet and outlet sites of the plants were determined. In comparing three domestic WWTPs with different wastewater treatment processes, the multivariate analyses (RDA and ANOVA) showed that although the Agareb plant received the highest pollution load, it displayed a high level of removal efficiency especially for COD, BOD, TSS, TKN and NH4+. It also revealed that the fluctuations in the wastewater composition and its contamination by varied industrial discharge could lead to the decrease in performance of the WWTP with activated sludge process as observed for the Southern Sfax plant. However, the electrolysis of the outlet water of Southern Sfax plant showed a significant improvement in COD removal.

Degradation of 4-chloroguaiacol by dark Fenton and solar photo-Fenton advanced oxidation processes.

This paper evaluates the dark Fenton and the solar photo-Fenton advanced oxidation processes for the treatment of solutions containing 4-chloroguaiacol (4-CG). The 4-CG was chosen as a model compound found in pulp and paper wastewater formed in the bleaching process in the pulp industry. The effects of operating parameters, including reaction time, hydrogen peroxide-to-ferrous iron molar ratio (H2O2/Fe2+), initial chemical oxygen demand (COD), pH value, and temperature, on 4-CG degradation efficiency using the solar photo-Fenton process were investigated. It was demonstrated that both processes could effectively degrade 4-CG in water and followed first-order kinetics. The degradation rate in solar photo-Fenton oxidation was much faster than that of the dark reaction. The 4-CG degradation depends on its concentration in the solution. The degradation efficiency decreases when the concentration of the 4-CG increases. Under the conditions of pH 3, H2O2/Fe2+ molar ratio 2, H2O2 16 mmol x L(-1), Fe2+ 8 mmol x L(-1), initial COD 640 mg x L(-1), reaction time approximately 24 minutes, and temperature 25 degrees C, the 4-CG and COD percent removal were greater than 80 and 89%, respectively.

Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry.

The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2µmolL(-1), with a detection limit of 0.065µmolL(-1).

Kinetic degradation of the pollutant guaiacol by dark Fenton and solar photo-Fenton processes.

This work is first intended to optimize the experimental conditions for the maximum degradation of guaiacol (2-methoxyphenol) by Fenton's reagent, and second, to improve the process efficiency through the use of solar radiation. Guaiacol is considered as a model compound of pulp and paper mill effluent. The experiments were carried out in a laboratory-scale reactor subjected or not to solar radiation. Hydrogen peroxide solution was continuously introduced into the reactor at a constant flow rate. The kinetics of organic matter decay was evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The experimental results showed that the Fenton and solar photo-Fenton systems lead successfully to 90% elimination of COD and absorbance at 604 nm from a guaiacol solution under particular experimental conditions. The COD removal always obeyed a pseudo-first-order kinetics. The effect of pH, temperature, H(2)O(2) dosing rate, initial concentration of Fe(2+), and initial COD was investigated using the Fenton process. The solar photo-Fenton system needed less time and consequently less quantity of H(2)O(2). Under the optimum experimental conditions, the solar photo-Fenton process needs a dose of H(2)O(2) 40% lower than that used in the Fenton process to remove 90% of COD.

Electrochemical degradation of waters containing O-toluidine on PbO2 and BDD anodes.

Electrochemical oxidation of O-toluidine (OT) was studied by galvanostatic electrolysis using lead dioxide (PbO2) and boron-doped diamond (BDD) as anodes. The influence of operating parameters, such as current density, initial concentration of OT and temperature was investigated. Measurements of chemical oxygen demand were used to follow the oxidation. The experimental data indicated that on PbO2 and BDD anodes, OT oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high temperature. Furthermore, BDD anodes offer significant advantages over PbO2 in terms of current efficiency and oxidation rate.