Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times

Bencsik, Martin; Shamim, M.F.; Morris, Robert H.; Newton, Michael I.

doi:10.1007/s13762-013-0336-7

Cited by 6 publications

(2 citation statements)

References 17 publications

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“…Determining the clog state of both model systems and wetland samples have been extensively investigated in the laboratory setting using relaxation measurements [10], [11], [12], [13], [14]. The parameter T2 eff has been previously used to successfully characterize clogging in a model system where a highly homogeneous magnetic field has been used for MR measurements [11], [12], however this was not possible with the inhomogeneous magnetic field of a low-cost permanent magnet system such as the type used in this work [14].…”

Section: Introductionmentioning

confidence: 99%

“…The parameter T2 eff has been previously used to successfully characterize clogging in a model system where a highly homogeneous magnetic field has been used for MR measurements [11], [12], however this was not possible with the inhomogeneous magnetic field of a low-cost permanent magnet system such as the type used in this work [14]. Therefore this work focusses on T1 relaxation measurements which have also been used to determine the clog state with a similar sensor in the past [10], [13], [14].…”

Section: Introductionmentioning

confidence: 99%

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Temperature dependence of magnetic resonance probes for use as embedded sensors in constructed wetlands

Hughes‐Riley

Dye

Anderez

et al. 2016

Sensors and Actuators A: Physical

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Constructed wetlands are now accepted as an environmentally friendly means of wastewater treatment however, their effectiveness can be limited by excessive clogging of the pores within the gravel matrix, making this an important parameter to monitor. It has previously been shown that the clog state can be characterised using magnetic resonance (MR) relaxation parameters with permanent magnet based sensors. One challenge with taking MR measurements over a time scale on the order of years is that seasonal temperature fluctuations will alter both the way that the sensor operates as well as the relaxation times recorded. Without an understanding of how the sensor will behave under different temperature conditions, meaningful information about the clog state cannot be successfully extracted from a wetland. This work reports the effect of temperature on a permanent magnet based MR sensor to determine if the received signal intensity is significantly compromised as a result of large temperature changes, and whether meaningful relaxation data can be extracted over the temperature range of interest. To do this, the central magnetic field of the sensor was monitored as a function of temperature, showing an expected linear relationship. Signal intensity was measured over a range of temperatures (5 °C to 44 °C) for which deterioration at high and low temperatures compared to room temperature was observed. The sensor was still operable at the extremes of this range and the reason for the signal loss has been studied and explained. Spin-lattice relaxation time measurements using the sensor at different temperatures have also been taken on a water sample and seem to agree with literature values. Further to this, measurements have been taken in an operational wetland over the course of 203 days and have shown a linear dependence with temperature as would be expected. This work concluded that the sensor can perform the task of measuring the spin-lattice relaxation time over the required temperature range making it suitable for long-term application in constructed wetlands.

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