Scientific analysis of the bacteriological characterization of Ecuador's Guano River in 2019, revealing pollution patterns and water quality challenges
Water Quality Bacteriology River Pollution
In the highlands of Ecuador, between the imposing volcanoes of Chimborazo province, winds the Guano River, a watercourse that tells a silent but eloquent story about the coexistence between nature and human activity.
This river, born from the melting snow of Chimborazo and runoff from the Igualata páramo, has witnessed how human communities grow and prosper on its banks, but also how this coexistence exerts pressures on its fragile ecosystem.
In 2019, a team of scientists undertook a comprehensive study to bacteriologically characterize its waters, revealing concerning realities but also providing crucial tools for its recovery.
According to WHO, at least 2 billion people worldwide use drinking water sources contaminated with fecal matter, and inadequate sanitation affects 4.2 billion 1 .
Length of river studied
Sampling points
Seasonal campaigns
Parameters measured
When scientists assess water safety for human consumption or recreational contact, they don't directly search for dangerous pathogens like Salmonella or Vibrio cholerae. Instead, they use an ingenious system of indicator organisms - bacteria whose presence suggests there might be fecal contamination and, by extension, potential pathogens 7 .
The most common indicators are total coliforms, fecal coliforms (with Escherichia coli as the main star), and intestinal enterococci.
To transform complex data from multiple parameters into a comprehensible water quality assessment, scientists use statistical aggregation tools like the Water Quality Index (WQI) 2 .
These metrics synthesize physical, chemical, and bacteriological information into a single numerical value that allows water to be classified into intuitive categories (excellent, good, acceptable, poor, very poor).
The scientific team established a strategic sampling design along 21 kilometers of the Guano River, from its origin at the confluence of Agags and Puluchaca streams to its mouth at the Chambo River.
They identified 29 observation points representing different anthropogenic pressures and natural conditions 2 . These included:
For bacteriological evaluation, researchers used two gold standard techniques in aquatic microbiology: the membrane filtration technique and the most probable number (MPN) method 7 9 .
Parallelly, physicochemical parameters such as pH, electrical conductivity, dissolved oxygen, temperature, and nutrient concentrations (nitrates, phosphates) were measured using portable field equipment and laboratory analysis according to standardized protocols 2 .
Selection of 29 sampling points representing different environmental conditions
Collection of water samples during low precipitation period
Collection of water samples during high precipitation period
Bacteriological and physicochemical analysis of all samples
Statistical processing and interpretation of results
Bacteriological results revealed widespread contamination along the Guano River, with clear spatial and temporal trends.
Concentrations of E. coli, the most specific indicator of recent fecal contamination, showed a dramatic increase when passing through the urban area of Guano, where discharges of inadequately treated wastewater pour directly into the channel 2 .
Multivariate statistical analysis revealed significant correlations between bacteriological indicators and certain physicochemical parameters.
Electrical conductivity showed a positive correlation with fecal contamination indicators, suggesting that organic pollution and mineralization go hand in hand in this system 2 .
| Sampling Point | Distance from Origin (km) | E. coli (CFU/100ml) | Total Coliforms (CFU/100ml) | Dissolved Oxygen (mg/L) | Conductivity (μS/cm) | pH |
|---|---|---|---|---|---|---|
| Agags-Puluchaca | 0.0 | 85 | 220 | 7.8 | 125 | 7.1 |
| Pre-Guano | 7.2 | 210 | 550 | 7.2 | 180 | 7.0 |
| Ciudad Guano (entry) | 10.5 | 8,500 | 15,000 | 5.8 | 385 | 7.3 |
| Ciudad Guano (exit) | 11.8 | 12,700 | 22,500 | 4.2 | 450 | 7.4 |
| Pre-Chingazo | 15.3 | 7,200 | 13,800 | 5.1 | 420 | 7.3 |
| Mouth | 21.0 | 9,850 | 18,200 | 4.8 | 395 | 7.4 |
| Bacteriological Parameter | Correlated Variable | Correlation Coefficient (r) | Significance (p-value) |
|---|---|---|---|
| E. coli | Conductivity | 0.82 | <0.01 |
| E. coli | Dissolved Oxygen | -0.79 | <0.01 |
| Total Coliforms | Nitrates | 0.75 | <0.05 |
| Enterococci | Phosphates | 0.68 | <0.05 |
| Fecal Coliforms | Turbidity | 0.71 | <0.05 |
The bacteriological characterization of a river requires a specialized arsenal of tools and reagents, each with a specific function in the detection and quantification of microorganisms.
| Reagent/Material | Function | Scientific Basis |
|---|---|---|
| mEndo Agar Medium | Selective culture for total coliforms | Contains bile salts that inhibit Gram-positive bacteria and lactose + brilliant green that detect fermentation |
| mFC Agar Medium | Specific culture for fecal coliforms | Includes rosolic acid that inhibits non-enterics and aniline blue that indicates acidification by lactose fermentation |
| Membrane filters (0.45μm) | Bacteria retention for direct counting | Pore size optimized to trap bacteria while allowing water passage |
| Reagents for pH/conductivity | Measurement of physicochemical parameters | Specific electrodes that respond to hydrogen ion concentration or ionic conduction capacity |
| Lactose broth | Liquid medium for MPN method | Detection of lactose fermentation through gas production in Durham tubes |
| Buffers and diluent solutions | Preparation of serial dilutions for quantitative analysis | Sterile isotonic solutions that maintain bacterial viability during sample preparation |
The 2019 bacteriological study of the Guano River painted a worrying but invaluable portrait of an aquatic ecosystem under significant anthropogenic pressure.
The findings clearly demonstrate how human activities - especially the discharge of inadequately treated wastewater - fundamentally alter the microbiological quality of a water body, with implications for ecosystem health and public health of riverside communities.
Beyond diagnosis, this research provides crucial tools for the management and recovery of the river. The use of locally adapted water quality indices and the analysis of correlations between variables offers environmental managers clear intervention points where targeted actions can produce significant improvements.
The recovery of the Guano River will require a coordinated effort that includes wastewater treatment plants, stricter regulations on industrial discharges, more sustainable agricultural practices, and community education programs. But the first step - understanding the dimension and nature of the problem - has already been taken thanks to bacteriological characterizations like the one carried out in 2019. Science has provided the diagnosis; now it is up to society to implement the cure.