Subsurface-flow constructed wetlands have become a very popular cost effective and green technology for treatment of waste water throughout Europe and the rest of the world. Original predictions over the longevity of constructed wetlands were approximately 50 -100 years (Conley et al 1991). However, it has become disappointingly apparent that these systems are clogging and have on average a lifetime of less than 10 years (Griffin et al 2008). Currently when a wetland becomes clogged, the whole site has to be refurbished and the reeds regrown, which takes several years and has significant economic consequences for the operators.
Our project ARBI aims to develop and trial an Autonomous Reed Bed Installation containing a magnetic resonance probe, can be deployed in several locations within a wetland to give measurements at different depths. By measuring the relaxation times of MR, sufficient information can be obtained to determine the clog state of the gravel bed of a wetland. This would enable the operators to isolate those areas of the bed where the problem resides and make a partial intervention, without the need to remove and re-plant the whole reed bed. When the system is developed, we will have potential for application in other water treatment systems based on subsurface flows like: slow rate sand filters, and river bank filtration.
The project will have major benefits for those organisations who would like to install reedbeds but have resisted doing because of concerns over performance and maintenance costs. These will increase the potential size of the market for reedbed installers and benefit the SMEs in the consortium who currently are operating in a constrained market which has not achieved its true potential.