Evaluation of the impact of dumping of domestic wastewater, applying the organic matter pollution index (ICOMO) in the Sococha river, located between Villazón (Bolivia) and La Quiaca (Argentina)

Abstract

Pollution indices (PIs) are widely used to assess the contamination levels of specific water bodies by integrating a carefully selected set of parameters closely linked to the particular pollution processes affecting the source. One such index is the Organic Matter Pollution Index (ICOMO), which incorporates parameters such as 5-day Biochemical Oxygen Demand (BOD5), Dissolved Oxygen (DO), and Total Coliforms. In this study, the ICOMO method was applied to evaluate the degree of organic pollution in the Sococha River. Sampling was conducted at four stations, selected following a preliminary field survey of the study area. Based on the measured parameters, the pollution index values were calculated, yielding the following ratings: Station 1 (Good: 0.35), Station 2 (Poor: 0.99), Station 3 (Poor: 0.93), and Station 4 (Moderate: 0.58). These results reveal a significant deterioration in water quality along the river’s course, indicating a progressive decline from upstream to downstream points. The validity of the ICOMO method was confirmed by comparing the obtained values with the thresholds established in the Water Pollution Regulation (RMCH). Laboratory analyses generally exceeded the permissible limits set by the regulation, underscoring the urgent need to implement control and mitigation measures to improve water quality in the Sococha River basin.