**2.2. Sampling and characterization of wastewater**

The water sampling was carried out in the discharge of wastewater from an electroplating industry, located in the City of Toluca, State of Mexico. A sample composed of 5 L of residual water was collected, which was integrated with five individual samples of 1 L each, taken from the wastewater discharge every 15 min. The parameters, determined according to standard methods [14], were pH, electrical conductivity (EC), nitrates (NO<sup>3</sup> −), sulfates (SO<sup>4</sup> 2 ), chlorides (Cl−), total chromium (by atomic absorption spectrometry) and chromium VI (by diphenylcarbazide spectrophotometry) [14].
