Evaluación del riesgo de deterioro biogénico inducido por H2S en estructuras de concreto de la línea de aguas residuales; en plantas de tratamiento de aguas residuales (ptar). Caso de estudio: Ptar Buga

Abstract

The biogenic deterioration of concrete induced by hydrogen sulfide (H₂S) is one of the primary degradation mechanisms affecting wastewater infrastructure. This study aimed to evaluate the risk of biogenic deterioration in concrete structures within the wastewater treatment line of the Buga Wastewater Treatment Plant (WWTP) by integrating the analysis of the internal environment with the chemical and surface condition of the concrete. The methodology included the measurement of physicochemical parameters of wastewater and the internal environment, such as airborne H₂S, dissolved sulfides, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), relative humidity, ventilation, and hydraulic retention time (HRT), together with the inspection of concrete deterioration indicators, including biofilm formation, surface pH, and carbonation depth. These variables were integrated using a multicriteria approach based on the Analytic Hierarchy Process (AHP) to develop an Environmental Aggressiveness Index (EAI) and a Concrete Surface Deterioration Index (CSDI), which were subsequently combined to estimate a Global Risk Index (GRI) and construct a Risk Assessment Matrix (RAM). The results revealed a GRI of 0.55 for the secondary clarifier, classifying the structure as high risk, as H₂S release occurred primarily in this unit, where peak concentrations of up to 26 ppm were recorded under conditions of longer hydraulic retention time and greater flow turbulence. Furthermore, biofilm development on moist concrete surfaces was found to be associated with surface chemical alteration of the material. The integration of the proposed indices enabled the identification of structures with greater susceptibility to biogenic deterioration within the evaluated wastewater treatment system.