Resumen en español

This paper presents the results of treatment with ozone and subsequent fractionation of dissolved organic matter (DOM) from secondary effluent from Cerro de la Estrella wastewater treatment plant located in Mexico City. The ozonation was carried out with two concentrations of ozone in the gas phase (5 and 25 mg/L) and two contact times (10 and 20 min). Fractionation of DOM was made using the resins XAD-4 and XAD-8, in order to determine the amount of hydrophobic and hydrophilic organic matter present in the wastewater. The best results were achieved with a concentration of 25 mg/L and a contact time of 20 minutes, achieving removals of 85 % color, 63 % turbidity, 71 % chemical oxygen demand (COD) and 78 % of UV254. We also determined the composition of DOM of secondary effluent in terms of total organic carbon (TOC), finding that ozone causes the hydrophobic organic matter from the effluent studied to decrease from 46 % to 32 % and the hydrophilic organic matter to increase from 32 % to 42 %.