**1. Introduction**

Over 2,000,000,000,000 people live in countries experiencing high water stress, and 4,000,000,000,000 people worldwide experience severe water scarcity for at least one month of the year. The environmental impact of this shortage will continue to increase, as water demand grows and the effects of climate change intensify [1]. Within this context, it is evident that some rivers exhibit high concentrations of organic matter and nutrients, high pollution levels caused by heavy metals, and high levels of contamination. Hence, continuous inspection and improvement are required to prevent major negative effects in

**Citation:** Castro Fernández, M.F.; Cárdenas Manosalva, I.R.; Colmenares Quintero, R.F.; Montenegro Marín, C.E.; Diaz Cuesta, Y.E.; Escobar Mahecha, D.; Pérez Vásquez, P.A. Multitemporal Total Coliforms and *Escherichia coli* Analysis in the Middle Bogotá River Basin, 2007–2019. *Sustainability* **2022**, *14*, 1769. https://doi.org/10.3390/ su14031769

Academic Editors: Pierfrancesco De Paola, Francesco Tajani, Marco Locurcio, Felicia Di Liddo and Agostina Chiavola

Received: 23 August 2021 Accepted: 10 January 2022 Published: 3 February 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

these rivers [2]. The 2030 Agenda for Sustainable Development is committed to "leaving no one behind", seeking universal and equitable access to drinking water, thus fostering socio-economic development and achieving the full realization of human rights across the globe [3].

Its vast hydrographic wealth ranks Colombia among the top 10 countries in the world in terms of water availability. Its water supply is 59 L/s/km2, which equates to six times the world average and three times the Latin American average. In addition, the country reports an annual rainfall of 3000 mm, exceeding the global average by three times and approximately twice the South American average [4]. However, according to the World Health Organization (WHO), 1,500,000 young children (under the age of 5) die every year due to the lack of safe water and sanitation, which is a common issue in developing countries such as Colombia [5].

Moreover, if Colombia is to remain a water power, the national governmen<sup>t</sup> must be committed to defending the country's water resources. It must also enforce the local regulations issued by Colombia's Ministry of Environment, Housing and Territorial Development [6]. It is important that for the proper managemen<sup>t</sup> of domestic and industrial wastewater treatment plants (WWTPs), investments are made to ensure that they run at optimal operating conditions throughout the national territory [7].

Colombia reports significant progress in the managemen<sup>t</sup> of conventional and hazardous solid waste against other Latin American countries. However, this is not completely feasible because there are still opportunities for improvement regarding the final disposal of solid waste in rural areas and municipalities, which still face issues due to the inappropriate disposal of solid waste, a situation fueled by poor landfill infrastructure and poor coverage of basic sanitation services [8]. Solid-waste mismanagement has caused cracks in landfills around the country, leading to landslides and leachate leakage, in addition to biogas accumulations that can generate atmospheric pollution [9]. This issue directly or indirectly affects the quality of water resources, since the subsoil and groundwater may become contaminated. Furthermore, poor garbage collection service coverage contributes to degrading not only the environment but also human health [8].

Total and fecal coliforms are Gram-negative bacteria, with aerobic and facultative growth capacity, that are commonly found in plants, soil and animals, as well as in humans [10]. The presence of coliforms in water bodies clearly indicates contamination by sewage discharges or decaying matter and especially by organic waste. Fecal contamination constitutes the main sanitary risk for water bodies since, given these conditions, this water will contain pathogenic microorganisms that can cause diseases threatening human health [11]. In fact, the presence of enteropathogenic microorganisms represents a high risk to public health [12].

Waterborne diseases are related to the presence of these fecal bacteria in both sewage and drinking water, which generate high morbidity and mortality rates, mainly in children [13]. Acute diarrheal disease is characterized by frequent discharges of feces with abnormal consistency. Approximately 85% of diarrhea-related deaths involve children under one year of age. The pathogens associated with diarrhea are: viruses, such as rotaviruses, which usually infect 10–50% of all humans; protozoa, such as *Cryptosporidium* sp., *Giardia lamblia*, and *Entamoeba histolytica*, which report a lower frequency of 1–8%; and bacteria, such as *Shigella* sp. (8–30%), enterotoxigenic *E. coli*, and enteropathogenic *E. coli*, which usually affects 5–40% of the population [14]. As mentioned above, *E. coli* is one of the direct causes of diarrheal diseases. Therefore, sanitary controls aimed at mitigating microbiological risks are extremely important and represent a critical measure for the population. Environmental managemen<sup>t</sup> in watersheds should necessitate a social responsibility approach, with the participation and commitment of different stakeholders at the governmental and national levels [15].

The Magdalena river basin has an area of 257,400 km2, occupying 22.5% of the Colombian territory, with a length of 1612 km [16]. This basin supplies water to 80% of the country's population and supports ~85% of the national GDP [17]. However, due to its

high level of contamination, the Magdalena River represents a health risk for a large part of the population in the center of the country who consume drinking water from this river [18]. The Magdalena riverbed experiences greater microbiological contamination by total coliforms (TC) and *Escherichia coli* during the dry season than during the rainy season because, during the rainy season, its flow increases due to rainfall, thus generating a dilution in the concentration of microorganisms [17]. Given that its major tributary is the Bogotá River, which flows directly into this body of water, serious social, economic, political, and environmental problems are observed [19].

In fact, one of the 17 goals proposed in the UN's Sustainable Development Goals for 2030 refers to adequate sanitation to ensure a clean watershed. In 2017, Colombia ranked 16th among 179 countries in the world, with a volume of 50,000 m<sup>3</sup> of water per inhabitant per year. With respect to this total volume, the Bogotá River provides ~300 m<sup>3</sup> of water per inhabitant per year [20]. The Bogotá river basin has been named as the most polluted water body in Colombia, as a result of sewage discharges from more than 7.4 million people residing in the area [21], and its waters flow into the Magdalena River, a major national river system [18].

The high concentrations of total and fecal coliforms in the middle reaches of the Bogotá River basin during the dry season are largely due to human and industrial settlements. There is also a relationship between the effects of climatic seasons and the pollution sources evaluated in this study [22]. In addition, discharges of untreated wastewater are the main source of contamination by these Enterobacteriaceae [23]. According to the 2014 Colombian Water Study, the Bogotá River reports an extremely high vulnerability index to water stress, which evidences the fragility of supply experienced by this water system during climatic phenomena, such as the El Niño event. Another critical variable to be evaluated is the water pressure reported by the different ecosystems and the amount of water that does not return to the basin. In fact, when analyzing the relationship between the green water footprint, which refers to the use and retention of water stored in the soil, and the blue water footprint, which refers to the retention of surface- and groundwater (rivers, lagoons, and aquifers) by anthropogenic activities, it becomes evident that water availability is seriously threatened by the large number of agricultural and livestock activities that are concentrated in the river subzones [24].

Historically, the Bogotá river basin has experienced significant uncertainty due to its pollution and sanitation, as well as water imbalances in its channel caused by inadequate land use and overexploitation. The different variables that influence anthropogenic modifications must be evaluated in order to preserve these ecosystems [25]. A better understanding of tipping points in lotic ecosystems will help to identify long-term impacts caused by human–ecosystem interactions and to establish adaptive and transformative managemen<sup>t</sup> plans for large rivers [26]. Pollution caused by industrial and domestic wastewater in the municipalities of the Capital District is also fostered by nefarious and underperforming treatment plants [27]. The increasing development of urbanization has exceeded the normal balance, thus stimulating an increase in environmental services and goods, which is coupled with increased waste generation [28].

According to the 2018 Progress Report of the Colombian Water Study, the capital city of Bogotá accounts for most of the domestic pollutant load on water sources [29]. For this reason, multiple prevention and correction activities aimed at reducing pollution are being carried out, which directly benefits the city's localities, since the middle section of the Bogotá river basin is located in the urban area of the Colombian capital [20]. However, although the "El Salitre" WWTP has been in operation since 1999 [30], it has not been able to remove the expected load volume, as it cannot keep up with processing the required wastewater levels. This plant has the capacity to treat 4 m<sup>3</sup> of wastewater per second but receives 15 m<sup>3</sup> per second, generated by the ~3 million people living in Bogotá alone. Therefore, most of the wastewater is not adequately treated. In addition, the Bogotá River also receives multiple discharges as it passes through the city [20].

This work focuses on determining the spatiotemporal patterns of microbiological conditions reported between 2007 and 2019 by the 35 stations located along the middle basin of the Bogotá River.

#### **2. Materials and Methods**

#### *2.1. Study Area*

The Bogotá River runs through the Cundinamarca and Boyacá highlands, crossing the department of Cundinamarca from northeast to southeast. Its headwaters are at 3300 m above sea level (masl) in the Páramo de Guacheneque forest reserve, in the municipality of Villapinzón, and flow into the Magdalena River, in the municipality of Girardot, at 280 masl, covering an area of influence of ~589,143 ha [31]. The Bogotá River is divided into three basins—the high, middle, and low basins—passing through 47 municipalities of the department of Cundinamarca, which route represents an influence on just over 10 million people, who are mainly from the city of Bogotá [32].

The middle basin of the Bogotá River corresponds to the section located between the monitoring stations, as shown in Figure A1: Quebrada La Tenería (No. 68) and downstream Quebrada Honda (No. 67). This river basin receives discharges (either directly or indirectly) from the municipalities of Chía, Cota, Tenjo, Subachoque, El Rosal, Funza, Madrid, Mosquera, Bojacá, Facatativá, Soacha, Tena, San Antonio del Tequendama, and part of the discharges from Cajicá, but especially the discharges from the Capital District of Bogotá. Its main tributaries in this section are the discharges from the Frio, Chicú, Balsillas, Salitre, Fucha, Tunjuelo, Soacha rivers, and the La Cuy and Honda streams. The data of the stations in this study were provided by the Corporación Autónoma Regional de Cundinamarca (CAR).

#### *2.2. Station Sampling Design*

For the last 12 years, the Environmental Laboratory of the CAR has studied the middle basin of the Bogotá River, performing microbiological analysis in 35 monitoring stations, taking as a reference the highest values, these being the most representative of the study. The sampling frequency was in the two seasons of the year, taken as the high-water and low-water seasons, which indicate the rainy and dry periods. For the development of microbiological analysis, two periods were identified. They were given the numbers 01, which includes the months from January to June, and 02, which includes the months from July to December. This designation is added after specifying the year of sampling, for example, 2014-02. The numbering of each station corresponds to the identification provided in the data by the CAR; these numbers do not have a sequential order. The monitoring stations are described below: Quebrada La Tenería (No. 68), upstream of Chía (No. 14), Chía Municipal Discharge (No. 29), downstream of Chía (No. 3), Limnigrafica (LG) bridge (Pte). La Balsa station (No. 42), River Frio (No. 75), downstream River Frio (No. 10), Cota Municipal Discharge (No. 30), LG Pte. La Virgen station (No. 43), River Chic ú (No. 74), Limnimetric (LM) Vuelta Grande (No. 58), Juan Amarillo Bypass (No. 22), El Salitre WWTP (No. 59), El Cortijo (No. 39), Jaboque discharge (No. 28), Engativá discharge (No. 27), Engativá downstream (No. 4), La Ramada (No. 53), LG Pte. Cundinamarca (No. 56), LM Hacienda San Francisco (No. 57), River Fucha (No. 76), downstream River Fucha (No. 11), Gibraltar pump (No. 24), LG La Isla (No. 54), Rio Tunjuelo (No. 70), downstream River Tunjuelo (No. 13), Rio Balsillas (No. 72), River Soacha (No. 79), Soacha cannel (No. 23), LG Las Huertas (No. 55), Mondoñedo bridge (No. 60), upstream Salto Tequendama (No. 18), San Antonio. Tequendama municipal discharge, Quebrada La Cuy (No. 31), Quebrada Honda (No. 67), and downstream Quebrada Honda (No. 9). Of the abovementioned stations, the ones closest to the urban area can be seen in Figure 1.

**Figure 1.** Location of Middle Basin Monitoring stations located with the identification number described above, Bogotá River approach. Source: prepared by the authors, 2021.

At a methodological level, coliforms were reported as per the Colilert method, which detects TC and *E. coli* using the defined substrate and a fluorescence technique. Then, spatial-temporal graphs were plotted for the TC and *E. coli* variables. The values reported were compared with the reference value of 2.0 × 10<sup>4</sup> MPN/100 mL for TC and 2.0 × 10<sup>3</sup> MPN/100 mL for *E. coli*, established by Executive Order 1594 in 1984.

The data collected for the middle Bogotá River basin were analyzed using a quantitative study that compared the results reported by the Regional Autonomous Corporation (CAR) in the 12 years from 2007-01 to 2019-02 at the 35 wastewater quality monitoring stations located along the waters of the middle river basin, taking the values established by Executive Order 1594 in 1984 as a reference. The results from the 35 stations or sampling points were organized sequentially according to each location within the middle basin, based on the coordinates provided by the Regional Autonomous Corporation (CAR), with each location being pinpointed using a geographic information system (ArcGis). Subsequently, the sets of values collected were cleaned using Excel and Origin Lab. Data analysis was performed using a descriptive statistical method to understand and analyze a given set of data [33], comparing the microbiological results of total coliforms and *Escherichia coli* over the 12-year period, in relation to the two seasons of the year, taking into account the maximum values of each season along the middle basin of the Bogota River (multitemporal analysis).
