**5. Conclusions**

This study concludes that, in the case of the middle Bogotá River basin, TC and *E. coli* concentrations are significant, since they exceed the permissible values established by current regulations. The analysis conducted for each year from 2007 to 2019 evidenced contamination in the water body, especially in the El Salitre WWTP, downstream Engativá, downstream Rio Fucha, and downstream Rio Tunjuelo stations, among others. Nevertheless, TC and *E. coli* concentrations have decreased in four stations—Rio Frio, Quebrada La Honda, the Jaboque discharge, and Rio Chic ú—mainly due to the oxygenation, geomorphology, and aeration processes where anthropic impacts are minimal. In these sections of the Bogotá River, due to the natural characteristics of the water body and contributions from its tributaries, the concentration levels of these pollutants are considerably reduced.

Even though specific sections of the riverbed have been recovered over the years through different environmental programs conducted by the Regional Autonomous Corporation (CAR), as well as via an increased environmental awareness in some areas, the current state of the middle basin of the Bogotá River remains unsatisfactory. In fact, its current condition is unacceptable due to the different activities that occur near the riparian buffer zone of the river, which brings about uncontrolled domestic, industrial, and/or commercial wastewater discharges, an increased number of illegal settlements, and poor adherence to the Territorial Organization Plan (POT) in different municipalities. Likewise, inappropriate organic and inorganic solid waste managemen<sup>t</sup> also favors the development of these fecal concentrations found in the surface waters of the river.

All these variables affecting the middle basin of the Bogotá River have a negative impact on public health and the environment, since this water is used to supply drinking water to a few communities outside Bogotá, as well as irrigation systems for crops intended for human consumption, causing gastrointestinal diseases to the human body due to its high content of coliforms and other toxic substances. For this reason, more WWTPs are expected to be implemented in the municipalities bordering the river, and significant improvements in the treatment capacities of each unit are required. In addition, new technologies should be implemented, such as solar water disinfection technologies in individual units and phytoremediation, where plant species such as algae are used to reduce the number of microorganisms favoring the development of communities.

**Author Contributions:** M.F.C.F. worked on data collection and conceptualization of information; I.R.C.M. worked on methodology construction, formal analysis and research; Y.E.D.C., D.E.M. and P.A.P.V. worked on data and information analysis and writing; C.E.M.M. and R.F.C.Q. worked on revision and writing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data provided by the Corporacion Autonoma Regional (regional autonomous corporation) (CAR).

**Acknowledgments:** The authors are grateful for the support of the Universidad Cooperativa de Colombia and the Partners Voor Water fund of the Dutch Government through the project Sustainable Water by floating solar energy powered Efficient reverse osmosis Treatment (SWEET).

**Conflicts of Interest:** The authors declare no conflict of interest.
