This study describes the optimization of the wastewater treatment process through the use of a free water surface flow constructed wetland with floating macrophytes at the laboratory level (20 L). A factorial design 2 was used in order to find the best operation conditions of the wastewater treatment process. The performance of macrophytes Eichhornia crassipes and Typha domingensis was investigated by operating the wetland system at hydraulic retention times of 2 and 4 days. The results showed an optimum operational condition that removed 92.39% of initial organic load (measured as COD). The nutrient removal efficiency of the constructed wetland was 99.28% for total nitrogen and 87.78% for phosphorus. The best operating condition includes the use of E. crassipes, with 4 days of hydraulic retention and the use of gravel as a filter. According to this, organic matter degradation kinetics was studied by the comparison of three kinetic models: first-order model, Stover-Kincannon model and Grau-second-order model. Stover-Kincannon and Grau kinetics models were more appropriate to represent the organic matter degradation kinetics in constructed wetland, with a determination coefficient of 0.9997. Based on the kinetic removal results, the process showed a maximum rate of organic load removal of 2500 mg/L d.

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This paper provides a technical analysis of a river’s current and future resilience in a watershed with intensive agricultural and fishing activities. The study area was the last section of the Culiacan River corresponding to the river mouth over a lagoon system. Dissolved oxygen modeling was performed using the Streeter-Phelps model to evaluate the river self-depuration capability using Biochemical Oxygen Demand, dissolved oxygen, streamflow, and water temperature data from 2013 to 2020. Fieldwork was carried out to establish the geomorphological characteristics of the river by determining stream velocity, width, and depth and the location of nine sources of pollution on the river. The modeling was performed for three groups of months with different temperatures, identified by hierarchical cluster analysis. Estimates were made for future scenarios, assessing the effect of climate change on the Culiacan River’s self-depuration capability. The results showed that most of the year, the degradation rate of the system results in rapid assimilation of organic matter. However, the modeling indicates that the river would lose its resilience capability under climate change. Thus, it is essential to implement wastewater treatment systems to reduce the environmental impact on the aquatic ecosystem in the river and the lagoon system.