Modelo conceitual para vigilância da qualidade da água para consumo humano em sistemas de pequeno porte.

Abstract

Drinking water quality surveillance (DWQS) is essential to ensure water supply security, providing information to support efficient decision-making. Even so, surveillance has some barriers in small water supply systems due to the lack of coordination between the interested institutions, inadequate data collection and analysis, difficulty in accessing information, poor systematization, human and financial scarce resources, insufficient infrastructure and labor, and arbitrary decision-making. Therefore, this work aims to develop a conceptual model for implementing DWQS adjusted to small systems. To this, a systematic and predictive methodology, combining risk assessment, geoprocessing, and continuous improvement tools, was developed and applied in a small pilot water supply system in the Brazilian city of Araruna. This conceptual model consisted of actions structured according to the PDCA cycle tool in the planning, execution, verification, and action stages. The planning stage must carry out registration of all water supply infrastructures to proceed with risk assessment, using a semi-quantitative method, which sums risk factors, parameterized based on quality standards, to calculate the risk of each registered infrastructure and distribute them in space and time, and, through spatial interpolation, delimit vulnerability zones that support a sampling plan for water quality. Then, in the execution stage, this sampling plan must monitor at least the indicators of free residual chlorine (FRC), turbidity, total coliforms, E. coli, and fluoride monthly, selecting points primarily in the areas of greatest vulnerability. So, in the verification stage, the monitoring data must be evaluated by adapting the failure mode and effect analysis method, calculating the health risks associated with water quality at the monitored points. Based on the data generated in the previous stages, the action stage develops a plan to improve local supply conditions, defining methods of investigation and communication of the information generated. By applying this conceptual model on a pilot scale, it was possible to verify that the main weaknesses of the system are related to alternative solutions that presented higher risks, both in the planning and verification stages, and the most significant indicators in the associated health risk to water quality were the microbiological indicators and the FRC. Given these results, the action plan indicates that the pilot system should prioritize efforts to improve the supply conditions of alternative solutions, especially in the microbiological quality of the water. This recommendation indicates that the conceptual model was profitable because it generated information in a small pilot system, recommending priority actions that would have more relevant effects on improving water supply. However, it is interesting that this model is tested in other systems, with other scenarios, types of supply, water quality indicators, and regulatory standards in different countries, to verify the robustness of the conceptual model or the need for adjustments.