Constructed wetlands are a popular form of waste-water treatment that have proliferated across Europe and the rest of the world in recent years as an environmentally conscious alternative to chemical treatments. The ability to monitor the conditions in the bed and control input factors such as heating and aeration may extend the lifetime of the reed bed substantially beyond the ten year lifetime normally reached. The Autonomous Reed Bed Installation (ARBI) project is an EU FP7 initiative to develop such a bed. One critical parameter to observe is the clog state of the reed bed, as this can severely impact on the efficiency of water treatment. Magnetic resonance (MR) sensors can be a powerful tool in determining clogging levels (Analyst 2011, 136, 2283-2286) and allow automated remedial action to be taken against the bed improving treatment efficiency, prolonging the life of the bed and avoiding the need to refurbish the bed, which is both time consuming and costly. This work details magnetic sensors suitable for long-term embedding into a constructed wetland
