Low-cost colorimetric sensor for water quality monitoring

With the increased concentrations of eutrophying ions, heavy metals, and organic contaminants in the water bodies, there is a need to develop tools for regular water quality monitoring. Various sensing techniques such as colorimetric, electrochemical, optical fluidic, and luminescent have been developed to monitor contaminants in water bodies. Many of the reported sensors enable high sensitivity (i.e., nM or ppb detection levels); however, the primary challenges in their field application include complex synthesis approach, reliability in long-term use, poor portability, intensive maintenance, and skilled labour requirement. This chapter reviews the research and development of various low-cost sensors to detect eutrophying anions (nitrate, nitrite, and phosphate), heavy metals (lead, chromium, cadmium, and mercury), pathogens, and emerging contaminants (ECs). The analytical performance, cost, and ease of deployment of sensors for detecting pollutants are critically evaluated. The feasibility of developed sensors for deployment on the Internet of Things platform is also identified. Lastly, a recommendation on the applicability of the developed sensors for field-scale application is presented.