Assessment of water quality in the upper Lerma river subbasin, State of Mexico

Abstract

The Lerma river basin begins in the municipality of Almoloya del Río in the State of Mexico and ends at Lake Chapala in Jalisco. Within this stretch lies the upper Lerma river basin in the State of Mexico, extending from Almoloya del Río to Temascalcingo. This basin is subdivided into three sub-basins: Upper, middle, and lower. Over the past few decades, the area has been heavily polluted, primarily due to direct discharges from residential, agricultural, livestock, and industrial sectors, which has compromised the vulnerability of aquatic systems, public health, and the self-sufficiency of healthy food. Under these circumstances, the purpose of this research is to assess the water quality of the Upper Sub-Basin according to permissible parameters set forth in NOM-001-SEMARNAT-2021 to characterize the environmental risks arising from the concentration of various pollutants originating from wastewater discharges. Regarding the methodology, three water collections were conducted throughout the study area during the rainy season and the dry season. The water samples were analyzed at the water quality laboratory of the Autonomous University of Chapingo and the company NALCO in accordance with the methodologies required by the regulations. The results showed concentrations of heavy metals, COD, BOD, oils, and fats that exceed the maximum permissible limits set by NOM-001-SEMARNAT-2021. The findings presented here provide a basis for developing strategies and designs to mitigate pollution-related damage; among these, a combined anaerobic reactor and wetland system is proposed for communities with fewer than 2,500 residents, to reduce energy costs at large-scale treatment plants serving population centers throughout the watershed, such as the Toluca Valley, Ixtlahuaca, Atlacomulco, and Temascalcingo.