This project started as an exploration into addressing freshwater pollution issues surrounding agricultural lands in New Zealand. Every year the runoff from these lands introduces ionic contaminants into the freshwater sources, affecting aquatic life as well as human populations living downstream. It’s important to consistently monitor these freshwater sources for contamination, although laboratory testing is expensive, discouraging frequent testing. Portable monitors exist, however the most affordable ones are limited in features.

To ensure the project incorporated domain-specific knowledge and addressed the real-world requirements. a collaboration with the Department of Civil and Environmental Engineering was established. Several water quality metrics were evaluated for suitability, and the electrical conductivity of water was selected, as it reliably indicates the presence of ionic contaminants in water.

Since a key requirement was to ensure the accessibility of this technology, various avenues were explored to lower the cost. A key design decision was to offload the expensive components such as battery, processing power, internet connectivity, and geo-location to the ever-ubiquitous smartphone. This lowered the overall manufacturing cost of the sensor to under 35 USD while enabling a range of features including the ability to collect sensor readings along with precise location data and track contamination trends over time and across regions. Another key factor to lower the cost was the use of common manufacturing processes for manufacturing the sensing electrodes. Each iteration of the sensor and the custom design was tested against standard solutions in an environmental engineering laboratory, ensuring that a high accuracy was maintained. The smartphone app was designed with a strong emphasis on user-friendliness. The sensor and the app integrate seamlessly, requiring only a couple of button presses to capture a reading. The sensor was evaluated with real-world water samples where it scored a high accuracy against lab-based equipment. Additionally, the complete system was evaluated for its usability through a user study where it achieved a high usability score. This project takes a strong step in the field of citizen science, empowering the general public to participate in the scientific process and fostering greater environmental awareness.