Clogging Measurement, Dissolved Oxygen and Temperature Control in a Wetland Through the Development of an Autonomous Reed Bed Installation (ARBI)
The suitability of different magnetic resonance sensor types, based on magnet arrangement, for the detection of different solids loadings in wetland sludges were explored. Unilateral and borehole design sensors were investigated. A development of the Helmholtz-style borehole design was selected due to its simplicity of design, low cost and large field of detection. The effect of aerating and heating a pilot wetland on organic matter and NH4-N reduction was investigated. Aeration improved performance across a range of oxygen concentrations down to 0.5 ppm below which little benefit was seen. No significant improvement was seen with heating between control and experimental bed. This is thought to be due to seasonal effects raising the temperature of the control to within 10 °C of the experimental bed, a difference thought not to be significant at the measured temperature range, (15–25 °C). Temperature driven hydrolysis of embedded organics may also be causing increased soluble COD outlet loads. We have demonstrated a Helmholtz like NMR sensor can detect differences in solids loading when buried in a gravel mix. Aeration can significantly increase treatment performances by 56 % and 69 % for COD and NH4-N reduction respectively at an oxygen tension of 5 ppm.
KeywordsAerated wetland Clogging Feedback Sensor Magnetic resonance Temperature
The research leading to these results has received funding from the European Union’s Seventh Framework Programme managed by the REA – Research Executive Agency http://ec.europa.eu/research/rea (FP7/2007_2013) under project reference 606326. The work has been supported by the following partners: ARM Ltd. (UK), Lab-Tools Ltd. (UK), Lightmain Ltd. (UK), OxyGuard International A/S (Denmark), TechnoSAM SRL (Romania), Nottingham Trent University (UK), Universitat Politècnica de Catalunya (Spain).
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