Fate of Emerging Contaminants During Infiltration of Untreated Wastewater in Mezquital Valley, Mexico
This study analyzed 218 organic microcontaminants in wastewater canals, springs and groundwater from the Mezquital Valley. Five volatile organic compounds (VOCs) and 9 semi-volatile organic compounds (SVOCs) were detected in the wastewater used for irrigation. Only 2 SVOCs were detected in all the wastewater canals and groundwater sources, whereas no VOCs were detected in groundwater and springs.
Of the 118 pharmaceutically active compounds (PhACs) and 7 reproductive hormones measured, 65 PhACs and 3 hormones were detected in the wastewater. In groundwater sources, 23 PhACs were detected. Most of these compounds have low concentrations compared to those detected in canals. There were only few detections and at lower concentrations in the deeper aquifers. These results suggest that the subsurface acts as a filter, adsorbing and degrading most of the organic pollutant content in the infiltrated wastewater. A new wastewater treatment plant (PTAR Atotonilco) is being built to treat the wastewater prior to its release to the Mezquital Valley. The geochemical changes that this cleaner water will produce when infiltrated into the aquifer have not been assessed yet.