Environmental monitoring represents one of the most critical challenges facing contemporary society, as water and air pollution significantly impacts human health, biodiversity, and ecosystem stability. This thesis investigates the development of a low-cost optical sensing system for large-scale monitoring of chemical and biochemical parameters, with a focus on bacterial detection in water. Currently, most water quality assessment methods rely on laboratory (ex situ) analyses. Although these approaches offer high accuracy, they are not suitable for continuous, distributed, and real-time monitoring, especially in developing regions where access to safe drinking water is critical. To overcome this limitation and contribute to the achievement of the United Nations Sustainable Development Goals, particularly Goal 6 (Clean water and sanitation), this work proposes a non-invasive and scalable in situ measurement solution based on fluorescence spectroscopy for bacterial detection.