Evolution of Wastewater Treatment Plants in Lake Chapala, Mexico (2011-2024)

The Lerma-Santiago-Pacific region faces significant challenges related to water availability and pollution. The main problem lies in the fact that water extraction exceeds the annual renewable natural supply. The contamination of the Lerma River is evident from its source, aggravated along its course by urban, industrial and agricultural discharges deficient treatment or without treatment. The Lerma River undergoes intense extraction for agricultural use and receives discharges from various cities, reaching negligible flows in the dry season. Water quality continues to deteriorate until it reaches Lake Chapala, where about 64% of the water arrives untreated, where the Wastewater Treatment Plants (WWTPs) are insufficient or not operating. The objective of this research is to determine the status of the treatment plants of the Lake Chapala basin in the period 2011-2024. Descriptive study of the evolution of the treatment plants of the Lake Chapala basin. Place and duration of study are the treatment plants of the Lake Chapala basin in the period 2011-2024. The methodology consisted of analyzing the information collected in a 2011 study regarding the projections for the capacity of WWTPs for the year 2020, together with the analysis of the historical growth of the population and the estimation of the same for the year 2030, and evaluating how the provision of drinking water and wastewater supply has evolved, likewise, the proposed capacity for the construction, expansion and/or modification of the WWTPs will be evaluated, as well as the technical details on the proposed expansions, the proposed processes for the expansions and the economic and financial evaluation, as well as the systematic expenses in their current state and the projection considerations. The results showed the comparison of WWTPs between 2011 and 2025 shows an increase from 22 to 42 WWTPs, many of them located and operated in private, outside the municipal administration. However, although the number of WWTPs has increased, 13 of them are out of operation. Some of the plants increased their capacity, however most were not expanded and decreased their operating capacity, so they are insufficient for current demand. Most small towns decreased their population growth rate and increased the operating capacity of their WWTPs. However, large populations increased their population growth, which represents a risk that in a short time the expansions of the WWTPs will be insufficient to meet the demand for wastewater that needs to be treated before discharging it into Lake Chapala. The conclusion of this analysis reveals the complexity of wastewater treatment infrastructure planning and management in a dynamic demographic and economic context. The results underscore the importance of adopting more flexible and adaptive approaches to infrastructure planning that can respond to reality.