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Usually, water treatment plants employ chlorine or sodium hypochlorite during the disinfection process, ensuring that there are not any pathogenic microorganisms in water. However, chlorine might react with natural organic matter and lead to formation of potentially carcinogenic by-products regarding human health, such as haloacetic acids (HAAs). Several countries regulate the levels of these acids in drinking water. Therefore, their concentrations must be monitored with the greatest accuracy as possible. In order to achieve this goal, a method through gas chromatography coupled with mass spectrometry (GC-MS) was validated and applied to the determination of HAAs in samples of water destined to the public water service provision from the city of Maringá, Paraná State, Brazil. Measurements between two periods have close recovery values, indicating that the method has good accuracy during the same day. The limits of detection (LOD) and quantification (LOQ) were satisfactory, with LOD 0.42 μg L-1 and LOQ 1.40 μg L-1 for dichloro-acetic acid (DCAA) analysis. Recovery values obtained for the nine haloace-tics acids (HAA9) corresponded to 69.9-107.3 % for samples. The repeatability performed for two periods presented close relative standard deviation (RSD) values, indicating that the method has good accuracy during the same day.

The concern for the removal of contaminants, such as hydrogen sulfide (H 2 S), during crude oil processing has been intensified. Sulfur compounds, such as dissociated H 2 S, are detected in the effluents of process gas condensation and streams of acid water. The objective of this study is to apply electrochemical oxidation to neutralize H 2 S in industrial effluents. Tests were performed in a porous bed electrochemical reactor, which was composed of reticulated vitreous carbon. The oxidation process is direct and potentiostatically controlled, and the dissociated sulfide was oxidized to sulfate and/or thiosulfate, main product of the reaction. Figures of merit were constructed to evaluate the performance of electrochemical reactor under different hydrodynamic conditions, by varying the flow rate, and overpotential, by varying the distance between the electrodes in the reactor. The figures of merit indicated that the best condition for the formation of thiosulfate occurred at the lowest flow rate used, 1.05 L h −1 and at a greater distance between the electrodes, 60 mm. [ABSTRACT FROM AUTHOR]