Microwave Sensors for Real-Time Nutrients Detection in Water

Current wastewater monitoring techniques rely on the use of nutrients detection as the result of some chemical reaction, which is undesirable for long-term use in real-time applications. In addition, new legislation may render such systems obsolete if they cannot reliably determine the amount of nutrients in wastewater relative to allowable levels. This chapter attempts to address this issue by considering the use of microwave sensing techniques as an alternative real-time approach that has the potential to monitor wastewater nutrients such as phosphate and nitrate. The method utilizes a broad range of microwave frequencies (1-15 GHz) and is demonstrated with two different types of structure for this purpose, namely a traditional resonant cavity and a flexible interdigitated electrode structure. A variety of experimental results are shown that validate the applicability of the microwave sensing for detecting phosphates and nitrates in the solutions. LabView software used for analysis of captured data and for easy user interpretation of this data is also demonstrated. Future work to be undertaken is discussed in relation to improving the performance of the sensor further, as well as adding the capability to automatically determine both the type and concentration of nutrients in water solutions.