Monitoring metal ions present in the effluent discharged from a surface treatment plant: Analytical results

Precise data concerning the metals occurring in industrial discharge water from the surface treatment sector as well as their qualitative and quantitative fluctuations have to our knowledge never been reported. In the present study, we monitored 28 metals in the effluent from a surface treatment plant every week for about a year. The effluent studied was taken at the outlet of a depollution plant that removed a large proportion of the metals as insoluble forms. We report and discuss the analytical results obtained on a total of 49 samples. The results, expressed both as concentrations and as fluxes, showed high levels of polymetallic contamination of the effluent. Of the 28 metals tested for, 13 were detected and 6 (Co, Cr, Fe, Mn, Ni, and Zn) were systematically present at quantifiable levels. Our findings also indicated how Cr, Fe, Ni and Zn levels were strongly dependent on certain conditions prevailing at the inlet of the wastewater treatment unit. Even though the levels of each metal were under the regulatory limits when taken individually, overall pollution from metals was far from negligible, with a calculated total of 264 kg of metals being discharged each year.