Given the need to improve bioenergy production processes, it is necessary to focus on low-cost culture media and environmental conditions of radiation and temperature. The Scenedesmus dimorphus species was cultured in eutrophicated lagoon water and Bayfolan 0.3% as culture media under four photoperiods with the objective of evaluating the biomass productivity, bioremediation capacity and influence of illumination on the composition and lipid content. It is concluded that the increase of light hours in the culture with eutrophicated lagoon water produces a decrease in the biomass productivity and COD removal percentage. The highest biomass productivity was obtained in photoperiod F1 (10.5:13.5) hours L:O, 0.053 ± 0.0015 g/L day and a removal of 95.6%. Bayfolan 0.3% with F2 (11.5:12.5) and F3 (12.5:11.5) did not show significant differences in the biomass productivity and COD removal. The increase in light hours in the photoperiod induced an increase of 1.01% and 2.84% of saturated fatty acids and 0.8% and 2.14% of monounsaturated fatty acids, as well as a decrease of 3.85% and 2.88% of polyunsaturated fatty acids in eutrophicated lagoon water and Bayfolan 0.3%, respectively.

The production of biodiesel from microalgae faces several problems to be solved, among them is the necessity of increasing their lipid content, optimizing the harvesting, and improving the conversion of lipids to bioenergy, therefore reducing the energy cost of the production process prior to its commercial launch. Research focused on optimizing the biodiesel production process known as transesterification has various objectives such as eliminating the biomass drying stage, unifying the extraction and transesterification stages, improving the reaction yield using supercritical conditions, providing heating with microwave and ultrasonic radiation, reusing enzymatic and heterogeneous catalysts, among others. This chapter aims to summarize the advances that have been achieved with the various operating conditions for the in situ, direct, and supercritical oil transesterification process of microalgae from the genera Chlorella, Scenedesmus, Spirulina, and Nannochloropsis.

Fresh water is vital for human activities; however, an increase in the contamination of water bodies has been observed, so it is necessary to monitor the degree of contamination and take measures to preserve it. In Altamira, Tamaulipas, the Guayalejo-Tamesí River basin has three estuaries and seven lagoons, including Laguna El Conejo, of which the National Water Commission only monitors one. The objective of this research is to determine water quality on the basis of the parameters COD, BOD₅, T, pH, and sediment characteristics. The open reflux method was used according to NMX-AA-030-SCFI-2012 for COD, BOD Track II, HACH equipment for BOD₅, and the granulometric characterization recommended by the Unified Soil Classification System ASTM D-2487-17. The water was found to be uniformly contaminated throughout its length in the range of 117.3–200 mg/L COD, and BOD₅ ranged from 15.8–112.75 mg/L throughout the study period, with sediments dominated by poorly graded soil and fine clay. Comprehensive management is needed because the BOD₅/COD ratio varies between 0.11and 0.56, indicating that it contains recalcitrant organic matter, which is difficult to biodegrade.

Emerging contaminants (ECs) represent a growing environmental problem due to their presence in various environmental matrices. In Mexico, research on ECs remains limited. This scoping review, conducted in accordance with the PRISMA-ScR guidelines, analyzes their environmental fate during the period 2004–2025, considering their distribution in surface and groundwater, sediments, and influents and effluents from wastewater treatment plants (WWTPs). The reviewed studies demonstrate the presence of pharmaceutically active compounds (PhACs), endocrine-disrupting compounds (EDCs), personal care products, phthalates, bisphenols, pesticides, illicit drugs, xanthines, perfluoroalkyl and polyfluoroalkyl substances (PFAS), metabolites, and industrial compounds. The Apatlaco, Cuautla, and Santa Catarina rivers exhibit the greatest diversity of ECs, while groundwater shows evidence of infiltration of PhACs, phthalates, bisphenols, and triclosan, associated with urban, industrial, and tourist discharges. In sediments, PhACs and EDCs accumulate at concentrations in the ng/g range, while phthalates reach concentrations of thousands of ng/g, indicating their affinity for the solid phase. At Mexican wastewater treatment plants, conventional treatment methods do not completely remove ECs, allowing residual amounts to be discharged into receiving bodies of water. Overall, national monitoring should be expanded to include metabolites, transformation products, and advanced treatment assessment.